catalysts

Article Light Cycle Oil Source for Hydrogen Production through Autothermal Reforming using Ruthenium doped Perovskite Catalysts

Yukwon Jeon 1,*, Hoi-Kyoeng Jung 2, Cho-I Park 2, Yonggun Shul 3 and Joo-il Park 2,*

1 Department of Environmental Engineering, Yonsei University, 1 Yonsei-gil, Wonju, Gangwon-do 26493, Korea 2 Department of Chemical & Biological Engineering, Hanbat National University, Daejeon 34158, Korea; [email protected] (H.-K.J.); [email protected] (C.-I.P.) 3 Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea; [email protected] * Correspondence: [email protected] (Y.J.); [email protected] (J.-i.P.); Tel.: +82-33-760-2466 (Y.J.); +82-42-821-1530 (J.-i.P.)


Received: 15 August 2020; Accepted: 8 September 2020; Published: 10 September 2020


Abstract: As the hydrogen economy is coming soon, the development of an efficient H2 production system is the first issue to focus on. In this study, a first attempt to utilize light cycle oil (LCO) feedstock is introduced for H2 production through autothermal reforming (ATR) using perovskite catalysts. From a careful characterization, it is found that LCO possesses a high content of C–H and S/N compounds with over 3–4 ring bonds. These various compounds can directly cause catalyst deactivations to lower the capability of H2 extraction from LCO. To achieve a heteroatom resistance, two different perovskite micro-tubular catalysts are designed with a Ru substitution at the B-site. The activity and stability of the Ru doped perovskite were controlled by modifying the Ru electronic structure, which also affects the oxygen structures. The perovskite with a B-site of Cr reveals a relatively high portion of active Ru and O, demonstrating an effective catalyst structure with a comparable LCO reforming activity at the harsh ATR reaction conditions. The greater stability due to the Ru in the perovskite is investigated post-characterization, showing the possibility of H2 production by LCO fuel through the perovskite catalysts.

Keywords: hydrogen; autothermal reforming; light cycle oil; perovskite catalyst; Ru substitution

1. Introduction The high demand for a new energy source has risen for many years, due to the limited amount of carbon-based sources that also cause severe environmental pollution by combustion [1,2]. The Paris Agreement was agreed under the United Nations Framework Convention on Climate Change (UNFCCC) between over 190 countries to be prepared for the severe climate change [3–5]. The goal of this agreement is to limit the global warming to 2 ◦C (and even 1.5 ◦C) at above pre-industrial levels by 2100 [6–8]. To achieve this goal, the international society is focusing on reducing the emission of the greenhouse gas (GHG) by a quick or large scale decarbonization system in all sectors of their economies. There are many decarbonization scenarios that have come out so far, but it is important to change to a new energy paradigm, which runs by an efficient and sustainable alternative energy source for the all sectors of the economy [8,9]. Hydrogen is foreseen to play a major role as a clean and potentially sustainable energy carrier, feedstock and fuel for applying to heating, industry, transportation and any other systems [7–11]. Therefore, a huge demand for hydrogen has recently increased, due to the expansion of the hydrogen-based society.

Catalysts 2020, 10, 1039; doi:10.3390/catal10091039 www.mdpi.com/journal/catalysts Catalysts 2020, 10, 1039 2 of 16

So far, more than 95% of hydrogen is produced by the reforming of fossil fuels, mainly to natural gas due to its high energy efficiency and practicality as a transition toward high technology [8,12–14]. Heavy-hydrocarbon sources, such as diesel and gasoline etc., have been recognized as a practical feedstock for establishing an efficient H2 infrastructure, because of its rich H2 content with high volumetric/gravimetric energy densities, easy storage and transport with a great accessibility [15–17]. To extract H2 from a heavy-hydrocarbon feed, it is reported that autothermal reforming (ATR), a combination of partial oxidation and steam reforming reactions, is effective due to its great cracking ability with low coke formation, high H2 yields and fast reaction start-up, etc. [18,19]. This technology has been expanded to various studies using different feedstock like gas oil, bio-oil and biomass, etc. [15,20,21]. Light cycle oil (LCO) is a middle distillate product of the fractionation of fuel catalytic cracking (FCC) reactor effluent [22,23]. Generally, LCO is the low-quality feedstock within the range of the distillation and viscosity (similar molecular structure) for diesel fuel production, since LCO is difficult to upgrade in conventional hydrotreating units. When directly using LCO, it is a poor diesel fuel blending component due to a poor performance of the engine ignition from a low cetane number and high density. The main application is its usage as a viscosity cutter for reducing the final viscosity of heavy residual fuel [24]. Therefore, in this study, a first attempt to directly utilize LCO as a feedstock for hydrogen production under autothermal reforming with a heteroatom-resistant catalyst is introduced. It has advantages for infrastructural reasons, and especially for the economical price of the starting feeds without any pretreatment processes [15,20]. Basically, LCO contains a high C/H atomic ratio and high concentration of the refractory sulfur species and N compounds. Such severe operating conditions are a concern when designing catalysts, because these kinds of hetero-atoms can decrease its stability caused by an agglomeration of the metal active sites, carbon coking and sulfur poisoning. Noble metals (Pt, Rh, Ru, and Pd etc.) deposited onto supports, are typically used as a conventional catalyst, but these are not free from the deactivation under such conditions due to the exposure of the active sites directly to hetero-atoms [25–27]. Nevertheless, LCO is an attractive feedstock in order to be commercially viable for H2 production. No studies on the reforming process by LCO have been reported, hence a highly active and stable catalysts under high S, N conditions need to be developed. Perovskite structured materials have been catalyst candidates for H2 production due to their stability at high temperature, H2-rich and redox environments [28–30]. Moreover, a good resistant to coke deposition and low chemical binding energy with sulphur are suitable for the suggested LCO reforming. With the formula ABO3, the B cation is believed to be responsible for the catalytic activity. It is possible to stabilize an active cation by partial substitution of B-sites, and further improve the activity/stability by the change of the perovskite structure and electronic configuration [31–34]. The metal doping can modify the perovskite oxide structure which could increase the surface active oxygen and reducibility at the same time, for higher activity in a autothermal reaction conditions [17]. Moreover, the metal substituted in the perovskite framework is trapped stably by the synergy effect with the surrounded active oxygen, resulting in a relatively high stability in even a very harsh reaction conditions. Therefore, doped perovskite catalysts can be suitable to chemical reactions at complicated operating conditions, especially H2 production from heavy-hydrocarbon feedstock. However, there are no studies reported on such catalyst systems at the LCO reforming reaction. Here, LCO-ATR reactions for economical H2 production are carried out under Ru doped perovskite catalysts with a micro-tubular morphology. The feedstock of LCO is characterized by the gas chromatography-atomic emission (GC-AED) to investigate the C/H atomic ratio, the concentration of the refractory sulfur species and N compounds. Two different perovskite catalysts are synthesized by the activated carbon fiber (ACF) template method to produce a hollow fibrous feature for higher surface area and mass/heat transfer [16,17,20]. A comparable amount of Ru with Pt is substituted into the B-site of LaCoO3 and LaCrO3. The prepared catalysts were characterized by SEM-EDX, XRD and XANES to investigate the structural difference. The activities of the designed perovskite catalysts were then measured at various temperature and each stability was compared in terms of the LCO Catalysts 2020, 10, 1039 3 of 16 Catalysts 2020, 10, x FOR PEER REVIEW 3 of 16 compositionterms of the to LCO the gascomposition products, to carbon the gas coking products, and carbon sulfur coking poisoning and sulfur after LCO-ATRpoisoning after reactions LCO- to understandATR reactions the mechanism. to understand the mechanism.

2. Results2. Results and and Discussion Discussion

2.1.2.1. LCO LCO Feedstock Feedstock Characterization Characterization In FigureIn Figure1, the1, the carbon, carbon, sulfur, sulfur, and and nitrogen nitrogen contents contents of of the the LCOLCO feedstock,feedstock, analyzed using using gas gas chromatography-atomicchromatography-atomic emission emission detection detection (GC-AED) (GC-AED) hyphenatedhyphenated with with a a high high temperature temperature injector injector systemsystem (HT (HT GC-AED) GC-AED) are are demonstrated. demonstrated. The The LCO LCO contained contained hydrocarbons hydrocarbons in in the the range range of of C10 C10 to C22to as wellC22 as 35,694well as ppm 35,694 sulfur ppm and sulfur 1177 and ppm 1177 nitrogen. ppm nitrogen. Moreover, Moreover, the sulfur the chromatogram sulfur chromatogram indicated thatindicated LCO contained that LCO 16,839 contained ppm of16,839 sulfur ppm as theof sulfur reactive as the sulfur reactive species sulfur and species 18,854 ppmand 18,854 of sulfur ppm as of the refractorysulfur as sulfur the refractory species. sulfur species.

FigureFigure 1. The1. The analytical analytical results results of of gas gas chromatography-atomic chromatography-atomic emission detection detection (GC-AED) (GC-AED) on on light light cyclecycle oil oil (LCO) (LCO) feedstock: feedstock: (a ()a carbon,) carbon, ( b(b)) nitrogen, nitrogen, ( (cc)) sulfur,sulfur, withwith comparisonscomparisons of of LCO LCO references. references.

InIn order order to to observe observe thethe molecular range, range, the the as-received as-received LCO LCO were were also analyzed also analyzed by using by two- using two-dimensionaldimensional gas gas chromatography chromatography coupled coupled with with time-of-flight time-of-flight mass massspectrometry spectrometry (2D GC-ToF (2D GC-ToF MS). MS).Various Various compounds, compounds, including including hydrocarbon, hydrocarbon, sulfur sulfur and and nitrogen nitrogen species, species, in inthe the samples samples were were classifiedclassified in Tablein Table1 into 1 into family family groups groups according according to to their their chemical chemical structures,structures, such as as ring ring numbers numbers andand saturation, saturation, for for easily easily discussing discussing their their reactivities reactivities overover reformingreforming catalysts. Figure Figure 1a1a shows shows the the C–HC– chromatogramH chromatogram to to analyze analyze the the HC HC composition composition inin thethe LCOLCO feed. It It was was found found that that a arelatively relatively lowlow quantity quantity of of around around 55% 55% was was C–H C–H compounds, compounds, indicatingindicating the high content content of of sulfur sulfur and and nitrogen nitrogen compounds.compounds. This This value value can can be be directly directly correlatedcorrelated toto the total H 22 yieldyield when when LCO LCO is is applied applied toto a a reformingreforming reaction. reaction. Most Most ofof hydrocarbon species species (C (CxHxyH) werey) were located located in 2- inor 3-ring 2- or 3-ringcompounds, compounds, from fromthe the list list of the ofthe C–H C–H compounds compounds in Table in Table 1. The1. Thecompounds compounds with with2–3 rings 2–3 ringsshow showa relatively a relatively high highcontent content of 42 of 42wt wt% while % while around around 10% 10% of the of comp the compoundsounds with withno rings no ringswas detected, was detected, meaning meaning hard hardring ring opening opening is a is crucial a crucial point point to toachieve achieve the the reforming reforming reaction. reaction. The The nitrogen nitrogen chromatogram chromatogram in

Catalysts 2020, 10, x FOR PEER REVIEW 4 of 16 Catalysts 2020, 10, x FOR PEER REVIEW 4 of 16 Catalysts 2020, 10, x FOR PEER REVIEW 4 of 16 FigureCatalysts 1b 2020 revealed, 10, x FOR that PEER the REVIEW nitrogen-containing species in the LCO feedstock mostly consisted4 of 16 Figure 1b revealed that the nitrogen-containing species in the LCO feedstock mostly consisted of Catalystsunsubstituted,Figure 2020 , 1b10, xrevealed FOR mono- PEER that REVIEWand thedialkyl-ca nitrogen-containingrbazoles with aspecies total nitrogen in the LCO content feedstock of 1176 mostlyppm. This consisted4 level of 16 of of unsubstituted, mono-Figure and 1b dialkyl-carevealedCatalysts thatrbazoles2020, 10the, x nitrogen-containingFORwith PEER a total REVIEW nitrogen species content in of the1176 LCO ppm. feedstock This level mostly of consisted of 4 of 16 nitrogenunsubstituted, can adversely mono- and affect dialkyl-ca the performancerbazoles with of catalytica total nitrogen ring-opening content and of 1176 other ppm. hydrotreating This level of nitrogen canFigure adverselyunsubstituted, 1b revealed affect themono-that performance the and nitrogen-containing dialkyl-ca of catalyticrbazoles ring-opening specieswith a totalin the nitrogen andLCO other feedstock content hydrotreating of mostly 1176 ppm. consisted This levelof of process.nitrogenCatalysts The can as-received 2020 adversely, 10, x FOR information affectPEER REVIEW the performance on the aromatic of catalyticand nonaromatic ring-opening contents and of other LCO hydrotreatingwere 73 and 4 of 16 process. The as-received informationCatalystsFigure 2020 , 1b 10on, xrevealed the FOR aromatic PEER that REVIEW andthe nonaromaticnitrogen-containing contents species of LCO in were the 73LCO and feedstock mostly consisted4 of 16 of Catalystsunsubstituted,202027nitrogen, wt10, %, 1039 respectively. can mono- adversely andCatalysts dialkyl-ca affect 2020, 10therbazoles, x FORperformance PEER with REVIEW a total of catalytic nitrogen ring-opening content of 1176 and ppm. other This hydrotreating level of 4 of 16 4 of 16 process. The as-receivedunsubstituted,Catalysts 2020 information, 10 mono-, x FOR PEERand on dialkyl-caREVIEWthe aromatic rbazoles and nonaromatic with a total nitrogencontents contentof LCO ofwere 1176 73 ppm. and This level4 of 16 27 wt %, respectively.nitrogenprocess. Figurecan Theadversely 1b as-received revealed affect thatinformation the the performance nitrogen-containing on the aromaticof catalytic andspecies ring-opening nonaromatic in the LCO and contents feedstockother of hydrotreating LCO mostly were consisted 73 and of 27 wt %, respectively.Figurenitrogen 1bFigure revealed can 1b adversely revealedthat the affectnitrogen-containingthat thethe nitrogen-containing performance species of catalytic in species the LCOring-opening in thefeedstock LCO andfeedstock mostly other consisted mostlyhydrotreating consistedof of process.27 wt Theunsubstituted, %, as-received respectively.Figure mono- information 1bTable revealed and 1. Classifieddialkyl-ca on that the aromaticthe C,rbazoles S, nitrogen-containing and Nand with species nonaromatic a total of LCO nitrogen speciesfeedstock. contents content in theof LCO ofLCO 1176 were feedstock ppm. 73 and This mostly level ofconsisted of Tableunsubstituted,process. 1. Classifiedunsubstituted, The mono- C,as-received S, and and mono- N dialkyl-ca species information and of dialkyl-ca rbazolesLCO feedstock.on the withrbazoles aromatic a total with nitrogenand a totalnonaromatic contentnitrogen of contentscontent 1176 ppm. ofof 1176LCO This ppm. were level This 73of and level of in Figure27 1wtb %, revealed respectively.nitrogen thatcanunsubstituted, theadversely nitrogen-containing affect mono- the and performance dialkyl-ca speciesrbazoles of catalytic in thewith LCOaring-opening total feedstock nitrogen and content mostlyother of hydrotreating 1176 consisted ppm. This of level of Species nitrogenRing27 wt SA/USA can %, respectively.adverselyTable 1 1. Classified affect the C, S,performance and NCompositions species of of catalytic LCO/(%) feedstock. ring-opening and other% hydrotreating 1 nitrogenTable can 1. adverselyClassified C, affect S, and the N speciesperformance of LCO feedstock.of catalytic ring-opening and other hydrotreating Speciesunsubstituted, Ring HC SA/USAprocess. mono- The andnitrogen as-received dialkyl-carbazoles can adversely informationCompositions affect on with thethe aromatic a/performance(%) total nitrogenand nonaromatic of catalytic content contentsring-opening of% 1176 of LCO ppm. and were 57.92 other This 73 andhydrotreating level Species process.Ring The SA/USAprocess.Table as-received 1. 1 The Classified as-received information C, S, and information N on species theCompositions aromatic of on LCO the feedstock.andaromatic/(%) nonaromatic and nonaromatic contents ofcontents LCO% were of LCO 73 and were 73 and HC 27 wt %, respectively.process. The 1 as-received information on the aromatic and nonaromatic 57.92 contents of LCO were 73 and of nitrogenSpecies can adversely 27Ring wt %, respectively. SA/USA affect the performanceTable 1.Eicosane Classified of catalytic (2.38),Compositions C, S, Octadecane and ring-opening N species/(%) (2.50), of LCO and feedstock. other hydrotreating% HC 0 27 -wt %, respectively.Eicosane (2.38), Octadecane (2.50), 8.94 57.92 0Species HC -Ring SA/USA27 wt %, 1 respectively. CompositionsNonadecane (0.92),/ (%) etc. 8.94 % 57.92 process. The as-receivedSpecies information Ring SA/USA onNonadecane the 1 aromaticEicosane (0.92), andetc. (2.38), nonaromatic OctadecaneCompositions (2.50), contents /(%) of LCO were 73 and % HC 1 0 SA - Table 1,7-Dimethyl-4-(1-methylethyl1. ClassifiedEicosane C, S, and (2.38), N species Octadecane)cyclodecane of LCO (2.50),feedstock. (0.165), etc. 57.92 0.17 8.94 0 - Table 1. ClassifiedTable 1. NonadecaneClassifiedC, S, and N C, species (0.92),S, and etc.ofN LCOspecies feedstock. of LCO feedstock. 8.94 27 wt %,1 respectively. SA 1 HC USA 1,7-Dimethyl-4-(1-methylethyl Benzene Table (1.48), 1. Classified)cyclodecane Octane (0.21) C, S,(0.165),, andCyclopropane N etc. species of (0.11), LCO 0.17 etc. feedstock. 2.06 57.92 Species1 Ring SA SA/USA 1 1,7-Dimethyl-4-(1-methylethylEicosane (2.38),Nonadecane OctadecaneCompositions (0.92),)cyclodecane (2.50), etc./(%) (0.165), etc. 0.17 % 0 - 1 8.94 1 USA Species 2 1 Ring SA BenzeneSA SA/USA (1.48), Octane 1,7-Dimethyl-4-(1-methylethyl Cyclopropane, (0.21) 1 , Cyclopropane 1,1’-methylenebis-Eicosane (0.11),Compositions)cyclodecane etc. (2.38), (0.07), Octadecane/(%) (0.165),etc. 2.06 etc. (2.50), 0.01 0.17 % Species0 Ring - SA/USA 1 Nonadecane (0.92), etc. Compositions/(%) 8.94 % 2 SAHC 1 Species USA Cyclopropane,Ring SA/USA Benzene 1,1’-methylenebis- (1.48), Octane (0.07), (0.21) etc., Cyclopropane Compositions (0.11), 0.01/(%) etc. 2.06 57.92 % 1 HC 1 SA USAHC 1,7-Dimethyl-4-(1-methylethyl Benzene Naphthalene (1.48), Octane (5.39), (0.21) )cyclodecane1,1’-Biphenyl, CyclopropaneNonadecane (0.165), (1.12), (0.92), (0.11), etc. etc. etc. 0.17 2.06 57.92 57.92 2 2 TableHCUSA SA 1. Classified C, S, Cyclopropane, and NEicosane species 1,1’-methylenebis- of(2.38), LCO Octadecane feedstock. (0.07), (2.50), etc. 10.65 0.01 57.92 0 1 Naphthalene - SA (5.39), 1,1’-Biphenyl 1,7-Dimethyl-4-(1-methylethyl1H-IndeneEicosane (1.12), (0.55), (2.38), etc. Octadecane )cyclodecane (2.50), (0.165), etc. 8.94 0.17 2 USA 1 2 USA SA Benzene (1.48), Cyclopropane,Naphthalene Octane (0.21) (5.39),1,1’-methylenebis-, Cyclopropane 1,1’-BiphenylEicosane (0.11),(0.07),(2.38), (1.12), etc.10.65Octadecane (2.50), 2.06 0.01 0 1 0 - USA1H-Indene - (0.55), Benzene etc. Nonadecane (1.48),Eicosane Octane (0.92), (2.38), (0.21) etc. Octadecane, Cyclopropane (2.50), (0.11), etc. 8.94 2.06 8.94 Species Ring 2 3 2 SA SA/USA SAUSA 1 0 Cyclopropane, - Tricyclo-octane,Naphthalene 1,1’-methylenebis-Compositions (5.39), 8-methyleneNonadecane 1,1’-Biphenyl/(%) (0.07), (0.01),Nonadecane (0.92), etc. (1.12),etc. etc. (0.92), etc. 0.01 0.02 10.65 % 8.94 3 SA 2 1 USA SA Tricyclo-octane, 1,7-Dimethyl-4-(1-methylethyl 8-methylene1H-Indene (0.01), etc. (0.55), Nonadecane etc.)cyclodecane (0.92), 0.02 (0.165), etc. etc. 10.65 0.17 1 2 SA SA NaphthalenePhenanthrene 1,7-Dimethyl-4-(1-methylethyl (5.39),1H-Indene Cyclopropane,(17.57), 1,1’-Biphenyl Anthracene (0.55), etc.1,1’-methylenebis- (1.12), (6.87),)cyclodecane (0.165),(0.07), etc. etc. 0.17 0.01 HC 3 3 1 USA SA USA 1 SA Benzene Tricyclo-octane, (1.48), 1,7-Dimethyl-4-(1-methylethylOctane 8-methylene (0.21), Cyclopropane (0.01), etc. (0.11),)cyclodecane etc. 31.40 (0.165), 0.02 57.92 2.06 etc. 0.17 2 USA 1 Phenanthrene1 USA SA (17.57), Benzene AnthraceneFluorene 1,7-Dimethyl-4-(1-methylethyl (1.48),Naphthalene (6.87), (1.47),Octane etc. (0.21) (5.39),, Cyclopropane 1,1’-Biphenyl)cyclodecane (0.11), (1.12),10.65 (0.165), etc. etc. 2.06 0.17 3 USA 3 SA 2 1 USA USAPhenanthrene Tricyclo-octane,1H-Indene Benzene(17.57), (0.55), 8-methylene Anthracene(1.48),etc. Octane (0.01), (6.87), (0.21)etc.31.40 , Cyclopropane (0.11), 0.02 etc. 10.65 2.06 2 SA 1 USAFluorene (1.47), Cyclopropane, etc. Benzene (1.48),1,1’-methylenebis-1H-Indene Octane (0.21) (0.55), (0.07),, Cyclopropane etc. etc. (0.11), etc. 0.01 2.06 0 3 4 3 SA USA -USA 2 SA 2 Eicosane Tricyclo-octane, SA Pyrene Phenanthrene (2.38), (2.06), Octadecane Cyclopropane, Benz(a)anthracene 8-methylene (17.57), Cyclopropane, (2.50), Anthracene 1,1’-methylenebis- (0.01), Nonadecane (1.24), etc. 1,1’-methylenebis- (6.87), etc. (0.92), (0.07), etc. etc. (0.07), 0.02 4.68 31.40 etc. 8.94 0.01 0.01 3 USA 2 SA NaphthaleneFluorene Cyclopropane, (5.39), (1.47), 1,1’-Biphenyl etc. 1,1’-methylenebis- (1.12), (0.07), etc.31.40 0.01 4 S 1 USA 2 SA USA Pyrene 3 (2.06), SA 1,7-Dimethyl-4-(1-methylethyl)cyclodecane Benz(a)anthraceneNaphthaleneFluorene (1.24), Tricyclo-octane, (1.47),etc. (5.39), etc. 1,1’-Biphenyl 8-methylene (0.165), 4.68 (1.12), etc.(0.01), etc. 30.75 0.1710.65 0.02 4 USA2 USA Phenanthrene Pyrene (2.06), (17.57), Benz(a)anthracene1H-Indene AnthraceneNaphthalene (0.55), (6.87), (1.24), etc. (5.39), etc. 1,1’-Biphenyl (1.12), 4.68 10.65 S 1 3 USA USA 2 BenzeneUSA (1.48), OctanePhenanthrene (0.21),Naphthalene1H-Indene Cyclopropane (17.57), (5.39), (0.55), Anthracene1,1’-Biphenyl (0.11),etc. 30.75 etc. (6.87), (1.12),31.40 2.06 10.65 S 4 USA 3 2 USAUSA PyreneFluorene (2.06), Benz(a)anthracene (1.47), etc. 1H-Indene (1.24), etc. (0.55), etc. 30.75 4.68 31.4010.65 2 3 SA SA Cyclopropane, Tricyclo-octane, 1,1’-methylenebis- 8-methyleneFluorene1H-Indene (0.07), (1.47), (0.01), (0.55), etc. etc.etc. etc. 0.01 0.02 S 4 0 USA - 3 SA 3 Pyrene SA (2.06), Benz(a)anthracene Tricyclo-octane, Tricyclo-octane, (1.24),8-methylene etc. 8-methylene (0.01), etc. (0.01), 4.680.01 etc. 30.75 0.02 0.02 0 2 - USA 4 3 Naphthalene USA SA (5.39),Phenanthrene 1,1’-Biphenyl Pyrene Tricyclo-octane, (17.57), (2.06), (1.12), Benz(a)anthraceneAnthracene 1H-Indene 8-methylene (6.87),0.01 (0.55), (1.24),(0.01), etc. etc. 10.65 4.68 0.02 S 3 USA Phenanthrene Phenanthrene (17.57), Anthracene (17.57), Anthracene (6.87), 30.75 (6.87), 31.40 3 0 SA3 - USA3 USA Tricyclo-octane,FluorenePhenanthrene 8-methylene (1.47), (0.01), (17.57), etc. etc. Anthracene (6.87), 0.01 0.02 31.40 31.40 1 0 S - - Fluorene (1.47), etc. 0.000.01 30.75 3 4 USA USA3 PhenanthreneUSA Pyrene (17.57), (2.06), Anthracene Benz(a)anthracene (6.87),Fluorene (1.24), (1.47), etc. etc. 31.40 4.68 31.40 1 - Fluorene (1.47), 0.00 etc. 4 0 1 USA - 4 - USA 4 USA Pyrene (2.06), Pyrene Benz(a)anthracene (2.06), Pyrene Benz(a)anthracene (2.06), (1.24), Benz(a)anthracene etc. (1.24), etc. (1.24),0.01 0.00 etc.4.68 4.68 4.68 S 0 4 USA- Pyrene (2.06), Benz(a)anthracene (1.24), etc. 30.75 0.01 4.68 1S -S 1-Propene-2-thiol ( ), Benzo[b]thiophene (0.119, 0.00 30.75 30.75 S 1-Propene-2-thiolS ( ), Benzo[b]thiophene (0.119, 30.75 30.75 1 - 0.00 2 0 - 1 - 1-Propene-2-thiol - ( ), Benzo[b]thiophene (0.119, 10.78 0.01 0.00 2 - 0 0 - 1-Propene-2-thiol - ( ), Benzo[b]thiophene10.78 (0.119, 0.01 0.01 0- 0 - 0.01 0.01 2 - 10.78 2 1 - - 1-Propene-2-thiol1-Methyl-prop-2-enyl ( Dithiopropanoate ), Benzo[b]thiophene (0.07, (0.119, ), etc. 10.78 0.00 1 - 1-Propene-2-thiol ( ), Benzo[b]thiophene (0.119, 0.00 1 - 1 - - 0.00 0.00 2 - 1 - 10.78 0.00 2 - 1-Propene-2-thiol ( ), Benzo[b]thiophene (0.119, 10.78 Dibenzothiophene1-Propene-2-thiol ( ( ),), Benzo[b]thiophene 2,7- (0.119, 1-Propene-2-thiol ( ), Benzo[b]thiophene (0.119, 2 Dibenzothiophene - ( 1-Propene-2-thiol 1-Propene-2-thiol ), (10.08,2,7- ( ), ), Benzo[b]thiophene (0.119,10.78 2 - Dimethyldibenzothiophene 10.78 2 2 - Dimethyldibenzothiophene -Dibenzothiophene ( ), 2,7- 10.78 10.78 3 - 2 - Dibenzothiophene ( ), 2,7- 19.90 10.78 3 - Dimethyldibenzothiophene 19.90 3 - DibenzothiopheneBenzo[b]thiopheneDimethyldibenzothiophene ( (0.119, ), 2,7- ), etc. 19.90 3 - Dimethyldibenzothiophene(9.63, Dibenzothiophene ), etc. ( ), 2,7- 19.90 (9.63, ), etc. 3 - Dimethyldibenzothiophene 19.90 DibenzothiopheneDibenzothiophene(9.63, (8.94, ( ), etc. ), ), 2,7- 3 - 3 - Dibenzothiophene ( ), 2,7- 19.90 19.90 (9.63, Dimethyldibenzothiophene Dibenzothiophene ), etc. ( ), 2,7- DibenzothiopheneDimethyldibenzothiophene ( ), 2,7- 4 3 - - Phenaleno(9.63, [1,9-bc]thiophene (0.04, ),Dimethyldibenzothiophene etc. 0.07 19.90 4 - Phenaleno [1,9-bc]thiophene (0.04, Dimethyldibenzothiophene 0.07 3 3 - 2,7-Dimethyldibenzothiophene - ), etc.(9.63, (9.63, ), etc. ), etc. 19.90 19.90 4 - 3 - Phenaleno [1,9-bc]thiophene (0.04, 0.07 19.90 4 - ), etc. 0.07 N Phenaleno [1,9-bc]thiophene(9.63, ), etc. (0.04, ), etc. 1.35 N 4 - (9.63, 1.35), etc. 0.07 4 - PhenalenoPhenaleno [1,9-bc]thiopheneButanenitrile [1,9-bc]thiophene), etc.(0.002), (0.04, (9.63, (0.04, etc. ), etc. ), 0.07etc. N 0 - 4 - (9.63, ), etc. 0.003 1.35 0.07 N Butanenitrile (0.002), etc.Phenaleno), etc. [1,9-bc]thiophene (0.04, 1.35 0 - Butanenitrile (0.002), etc. 0.003 N 0 - ), etc. 0.0031.35 N 4 - Butanenitrile (0.002), etc. 1.35 0.07 1 0 N - - Phenaleno [1,9-bc]thiophene (0.04, 0.040.003 1.35 0 -4 4 - 3-Methyl-1,2-diazirine - ButanenitrilePhenaleno Butanenitrile (0.017, (0.002),Phenaleno [1,9-bc]thiophene (0.002), etc. [1,9-bc]thiophene etc. (0.04, ), etc. (0.04, 0.003 0.07 0.07 1 - 4 - ), etc. 0.04 0.07 0 1 - 3-Methyl-1,2-diazirine - (0.017, Phenaleno Butanenitrile ),[1,9-bc]thiophene etc.), etc. (0.002), (0.04, etc. 0.003 0.04 0 - ), etc. 0.003 1 N 1 - - 3-Methyl-1,2-diazirine (0.017, ), etc. ), etc. 0.040.04 1.35 2 N - N 3-Methyl-1,2-diazirine3-Methyl-1,2-diazirine (0.017, (0.017, ), etc. ), etc. 0.07 1.35 1.35 2 - 1 - N Butanenitrile (0.002), etc. 0.07 0.04 1.35 0 - 3-Methyl-1,2-diazirinePyridine (0.02, (0.017, Butanenitrile Butanenitrile (0.002), ), etc. ), etc. (0.002), etc. 0.003 2 0 - 1 0 - - - Butanenitrile (0.002), etc. 0.07 0.003 0.04 0.003 2- 0Pyridine (0.02, - 3-Methyl-1,2-diazirine ), etc. (0.017, ), etc.0.07 0.003 2 - Pyridine (0.02, ), etc. 0.07 1 - Pyridine (0.02, ), etc. 0.04 Catalysts 20202 , 10 , x FOR - PEER1 REVIEW - Pyridine (0.02, ), etc. 0.07 5 of 16 0.04 2 1 - -3-Methyl-1,2-diazirine (0.017, ), etc. 0.07 0.04 1 - PyridineCarbazole3-Methyl-1,2-diazirine (0.02, (0.637, 3-Methyl-1,2-diazirine (0.017, ), etc. ), (0.017, ), etc. ), etc. 0.04 3 - 3-Methyl-1,2-diazirine (0.017, 1.23 ), etc. CarbazoleCarbazole (0.637, (0.637, ), Pyridine 3,3-Diphenyl-5-methyl-3H-pyrazole ), (0.02, ), etc. 3 3 - 2 - - Carbazole (0.637, ), 1.23 1.230.07 3 2 - 2 - - Carbazole (0.637, ), 1.23 0.07 0.07 3 - 2 - Pyridine (0.02, ), etc. 1.23 0.07 Carbazole(0.281, (0.637,(0.281,Pyridine (0.02, Pyridine ), etc. ), (0.02, ), ), etc. ), etc. 3 - Pyridine (0.02, ), etc.1.23 (0.281, ), Carbazole (0.637, ), 3 - (0.281, ), 1.23 44 - - 0.01 0.01 4 - (0.281, ), 0.01 Benzo(a)phenazineBenzo(a)phenazine Carbazole (0.006, (0.637, (0.006, ), etc. ),), etc. 4 3 - - (0.281, Carbazole Carbazole(0.637, ), (0.637, ), 0.01), 1.23 4 3 - 3 - - Carbazole (0.637, ), 0.01 1.23 1.23 Total 3 - (0.281, ), 90.02 1.23 Total 4 - 0.01 90.02 1 4 Saturated1 - (SA)/Unsaturated (USA). 0.01 Saturated (SA)/Unsaturated(0.281, (USA). ), (0.281, (0.281, ), ), (0.281, ), Among the4 aromatic - hydrocarbons, diaromatics (49 wt %) and triaromatics (34 wt %) were0.01 4 4 - - 0.01 0.01 Among the aromatic hydrocarbons,4 - diaromatics (49 wt %) and triaromatics (34 wt %) were 0.01 predominant with small contents of monoaromatics (6 wt %) and polyaromatics (compounds with predominant with small contents of monoaromatics (6 wt %) and polyaromatics (compounds with four four or more rings, 11 wt %). As shown in Figure 1c, the value of the sulfur species is in total of over or more rings,30% 11 in wtthe %). LCO As compositions, shown in Figure which1 c,is thea very value high of theconcentration sulfur species comparing is in totalto other of overheavy- 30% in the LCO compositions,hydrocarbon feeds which such is as a diesel, very gasoline high concentration and even gas-oils comparing [15–17,20]. This to other large heavy-hydrocarbonamount of sulfur feeds suchspecies as diesel, will gasolineaffect to a deactivation and even gas-oils of the cata [15lysts–17 during,20]. the This LCO large reforming amount reaction, of sulfur showing species the will necessity of the stable catalyst development. Therefore, a higher content of S and N species affect to a deactivation of the catalysts during the LCO reforming reaction, showing the necessity of neighboring with 2–3 ring compounds has been led to usage of heteroatom resisted catalyst type such the stable catalystas perovskite development. form. Therefore, a higher content of S and N species neighboring with 2–3 ring compounds has been led to usage of heteroatom resisted catalyst type such as perovskite form. 2.2. Synthesis of Perovskite Catalysts To produce hydrogen from a heavy-hydrocarbon source of LCO, perovskite based micro- tubular catalysts are designed due to a relatively high surface area and efficient mass transfer for a high contact time and short diffusion of the reactants in the autothermal reforming system. The microtubular feature was obtained through an ACF combustion method at mild heat treatment [16,17], and each stoichiometric element with a comparable noble-metal loading (5 wt %) formed catalyst materials composed of perovskite nanoparticle network.

2.2.1. SEM-EDX (Scanning Electron Microscopy-Energy-Dispersive X-ray) Figure 2 shows the SEM and EDX results to investigate the morphology and elemental composition of the prepared perovskite micro-tubular LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3 catalysts. A clear hollow fibrous feature is seen with a corresponding of the ACF template. Through this method, a uniform size was obtained with outer and inner fiber diameter in the ranges of around 3.9– 5.1 and 4.1–5.2 μm. As summarized in Table 2, the unique micro-tubular shape provides relatively high surface area of the perovskite materials with a value of around 15 m2/g, which is 3–4 times higher than the original surface area of the grain perovskites [16]. The perovskite surface connected with the uniform size of the spherical nanoparticles also offers a relatively high surface area, which is expected to definitely affect the catalytic activity like reforming reactions. From the SEM-EDX analysis in Figures 2 and S1, it was possible to investigate the chemical compositions calculated by the average values. All perovskite elements were well distributed over the fibrous catalysts in the whole area, especially Ru, which was doped to the B-site. Table 2 shows that each compositions is well agreed with the designed stoicometric perovskite materials. The Ru amount was in the range of 0.14–0.16 molar ratio, which is around 5% in weight comparable to the prepared Pt reference.

Catalysts 2020, 10, x FOR PEER REVIEW 5 of 16

necessity of the stable catalyst development. Therefore, a higher content of S and N species neighboring with 2–3 ring compounds has been led to usage of heteroatom resisted catalyst type such as perovskite form.

2.2. Synthesis of Perovskite Catalysts To produce hydrogen from a heavy-hydrocarbon source of LCO, perovskite based micro- tubular catalysts are designed due to a relatively high surface area and efficient mass transfer for a Catalysts 2020, 10, 1039 5 of 16 high contact time and short diffusion of the reactants in the autothermal reforming system. The microtubular feature was obtained through an ACF combustion method at mild heat treatment 2.2.[16,17], Synthesis and each of Perovskite stoichiometric Catalysts element with a comparable noble-metal loading (5 wt %) formed catalyst materials composed of perovskite nanoparticle network. To produce hydrogen from a heavy-hydrocarbon source of LCO, perovskite based micro-tubular catalysts2.2.1. SEM-EDX are designed (Scanning due to Electron a relatively Microscopy-Energy-Dispersive high surface area and efficient X-ray) mass transfer for a high contact time and short diffusion of the reactants in the autothermal reforming system. The microtubular Figure 2 shows the SEM and EDX results to investigate the morphology and elemental feature was obtained through an ACF combustion method at mild heat treatment [16,17], and each composition of the prepared perovskite micro-tubular LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3 catalysts. stoichiometric element with a comparable noble-metal loading (5 wt %) formed catalyst materials A clear hollow fibrous feature is seen with a corresponding of the ACF template. Through this composedmethod, a ofuniform perovskite size was nanoparticle obtained with network. outer and inner fiber diameter in the ranges of around 3.9– 5.1 and 4.1–5.2 μm. As summarized in Table 2, the unique micro-tubular shape provides relatively 2.2.1. SEM-EDX (Scanning Electron Microscopy-Energy-Dispersive X-ray) high surface area of the perovskite materials with a value of around 15 m2/g, which is 3–4 times higher thanFigure the original2 shows surface the SEM area and of the EDX grain results perovs to investigatekites [16]. The the morphologyperovskite surface and elemental connected composition with the ofuniform the prepared size of the perovskite spherical micro-tubular nanoparticles also LaCr offers0.85Ru a 0.15relativelyO3 and high LaCo surface0.85Ru area,0.15O which3 catalysts. is expected A clear hollowto definitely fibrous affect feature the catalytic is seen activity with a correspondinglike reforming reactions. of the ACF template. Through this method, a uniformFrom sizethe SEM-EDX was obtained analysis with in outer Figures and 2 innerand S1, fiber it was diameter possible in theto investigate ranges of the around chemical 3.9–5.1 andcompositions 4.1–5.2 µm. calculated As summarized by the av inerage Table values.2, the uniqueAll perovskite micro-tubular elements shape were provides well distributed relatively over high surfacethe fibrous area catalysts of the perovskite in the whole materials area, especially with a value Ru, which of around was doped 15 m2 /tog, the which B-site. is 3–4Table times 2 shows higher thanthat theeach original compositions surface is area well of agreed the grain with perovskites the designed [16 ].stoicometric The perovskite perovskite surface materials. connected The with Ru the uniformamount sizewas ofin thethe sphericalrange of nanoparticles0.14–0.16 molar also ratio, off erswhich a relatively is around high 5% surfacein weight area, comparable which is expectedto the toprepared definitely Pt areference.ffect the catalytic activity like reforming reactions.

Figure 2. SEM image and EDX mapping images of (a) LaCr0.85Ru0.15O3 and (b) LaCo0.85Ru0.15O3, Figure 2. SEM image and EDX mapping images of (a) LaCr0.85Ru0.15O3 and (b) LaCo0.85Ru0.15O3, includingincluding elemental elemental analysisanalysis results.results.

TableTable 2. 2.Elemental Elemental and and N N2 2adsorption adsorption isomers isomersanalysis analysisof of LaCr LaCr0.90.9Ru0.1OO3 3andand LaCo LaCo0.90.9RuRu0.10.1O3O 3 catalysts. catalysts. Elemental Compositions 1 BET Analysis 2 Catalysts Elemental TotalBET Pore Volume Average Pore S Catalysts La Cr vs. Co Ru BET (p/p0 = 0.990) Diameter Compositions 1 (m2/g) Analysis 2 (mL/g) (nm)

LaCo0.85Ru0.15O3 1.00 0.86 0.14 15.5 0.047 12.6

LaCr0.85Ru0.15O3 1.00 0.84 0.16 14.3 0.051 15.9 1 2 Calculated the average from SEM-EDX analysis in Figure2 and Figure S1. Calculated from N2 adsorption-desorption analysis.

From the SEM-EDX analysis in Figure2 and Figure S1, it was possible to investigate the chemical compositions calculated by the average values. All perovskite elements were well distributed over the fibrous catalysts in the whole area, especially Ru, which was doped to the B-site. Table2 shows that each compositions is well agreed with the designed stoicometric perovskite materials. The Ru amount Catalysts 2020, 10, x FOR PEER REVIEW 6 of 16

Total Pore Average Pore SBET Volume La Cr vs. Co Ru Diameter (m2/g) (p/p0 = 0.990) (nm) (mL/g) LaCo0.85Ru0.15O3 1.00 0.86 0.14 15.5 0.047 12.6 LaCr0.85Ru0.15O3 1.00 0.84 0.16 14.3 0.051 15.9

1 Calculated the average from SEM-EDX analysis in Figures 2 and S1. 2 Calculated from N2 adsorption- desorption analysis.

2.2.2. XRD (X-Ray Diffraction) The proof of the noble metal doping, ruthenium, is very important in this study, since the doped noble metal is reported to appear with much higher stability, and even activity, on the reforming reactions using heavy-hydrocarbon feedstock [17,20,33,34]. This can be demonstrated by the change Catalystsof the XRD2020, 10patterns., 1039 In Figure 3, XRD analysis was performed to investigate the perovskite structure6 of 16 of LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts, comparing to the non-doped LaCoO3 and LaCrO3 as references. Overall, both catalysts show great homogeneity and high crystallinity of the perovskite wasstructure in the from range the of clear 0.14–0.16 and intense molar ratio, XRD whichpatterns. is around It was seen 5% in that weight both comparableperovskites toare the consisted prepared of Pt reference. the major diffraction peaks for LaCrO3 and LaCoO3, respectively, without any obvious additional peaks, indicating a fine Ru doping of the desired 0.15 mol into the B-site perovskite structure. 2.2.2. XRD (X-Ray Diffraction) The XRD patterns for LaCoO3 based materials in Figure 3 show major peaks corresponding to the perovskiteThe proof of(hkl) the indices noble metal of (110)/(104), doping, ruthenium, (202), (024), is very(214), important and (220), in respected this study, to since the thediffraction doped noblelines characteristic metal is reported of rhombohedral to appear with LaCoO much3 perovskite higher stability, phase and (JCPDS even 48–123) activity, [33,34]. on the The reforming strong reactionsdoublet at using around heavy-hydrocarbon 32–33° is the evidence feedstock of rhombo [17,20,33hedric,34]. This deformation can be demonstrated of the ideal bycubic the perovskite change of thestructure. XRD patterns. By the Ru In doping Figure3 into, XRD th analysise B-site of was the performed perovskite to structure, investigate a slight the perovskite shift of this structure doublet oflet LaCoto a 0.85lowerRu0.15 angleO3 and value LaCr was0.85Ru observed0.15O3 catalysts, at the right-hand comparing toside the of non-doped Figure 3. LaCoO It means3 and a LaCrO modified3 as references.rhombohedral Overall, structure both (JCPDS catalysts 86-1662), show great which homogeneity is due to the and different high crystallinityionic radii of of Co theIII (0.61 perovskite Å) and structureRuIII (0.82 from Å) [33,34]. the clear The and changed intense d-value XRD patterns. and cell It parameters was seen that in bothTable perovskites 3 indicates are that consisted the partial of thereplacement major diff ofraction CoIII ions peaks by for the LaCrO bigger3 RuandIII LaCoOions increase3, respectively, the average without B-site any ion obviousradius, resulting additional to peaks,the rhombohedric indicating a deformation fine Ru doping of the of the perovskite desired 0.15lattice. mol into the B-site perovskite structure.

Figure 3. XRD patterns with the magnification of peaks (110)/(104) and (112) (right hand side) of Figure 3. XRD patterns with the magnification of peaks (110)/(104) and (112) (right hand side) of LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3, including LaCrO3 and LaCoO3 as references. LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3, including LaCrO3 and LaCoO3 as references.

The XRD patterns for LaCoO3 based materials in Figure3 show major peaks corresponding to Table 3. The d-values, cell parameters and particles size of LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3 the perovskite (hkl) indices of (110)/(104), (202), (024), (214), and (220), respected to the diffraction catalysts, including LaCrO3 and LaCoO3 as references. lines characteristic of rhombohedral LaCoO3 perovskite phase (JCPDS 48–123) [33,34]. The strong 1 2 doublet at around 32–33 ◦ is thePeak evidence d-Value of rhombohedric Cell Parameters deformation of Particles the ideal Size cubic perovskite structure. By the Ru doping intoP thep B-sited (Å) of the perovskitea (Å) b (Å) structure, c (Å) a slight P shifts of this doublet let to a lower angle value was observed at the right-hand side of Figure3. It means a modified rhombohedral structure (JCPDS 86-1662), which is due to the different ionic radii of CoIII (0.61 Å) and RuIII (0.82 Å) [33,34]. The changed d-value and cell parameters in Table3 indicates that the partial replacement of CoIII ions by the bigger RuIII ions increase the average B-site ion radius, resulting to the rhombohedric deformation of the perovskite lattice. The Cr based LaCrO3 perovskite shows slightly different reflection patterns corresponded to the perovskite (hkl) indices of (112), (022), (220), (222), (312), and (040). These are interpreted to the orthorhombic structure within the Pbnm space group, stated in powder diffraction file JCPDF 024-1016 [16,17,35,36]. With a similar theory above for LaCr0.85Ru0.15O3, the Ru doping generally introduces a distortion into the ideally orthorhombic perovskite structure while the pure LaCrO3 has only one distinct B-site in the lattice [28,31,32]. The peak shifts to a lower angle at the magnified III image of the (112) reflection (Figure3) evidences the substitution of Ru into LaCrO3 without no significant structural changes. The crystal ionic radii of the CrIII (0.75 Å) is also smaller than the substituted RuIII (0.82 Å) in the B-site [37], which expands the perovskite lattice structure (Table3) and Catalysts 2020, 10, 1039 7 of 16

provides a high percentage of octahedral RuO6 configuration sites at the crystal structure with the designed stoichiometric ratios. Interestingly, a decrease of the particle sizes is also observed for both perovskite catalysts with partial Ru doping, which may convey also a higher catalytic activity during the LCO-ATR reactions.

Table 3. The d-values, cell parameters and particles size of LaCr0.85Ru0.15O3 and LaCo0.85Ru0.15O3 catalysts, including LaCrO3 and LaCoO3 as references.

Peak 1 d-Value Cell Parameters Particles Size 2

Pp d (Å) a (Å) b (Å) c (Å) Ps LaCoO3 33.15 2.783 5.468 5.453 13.17 38.2 LaCo0.85Ru0.15O3 32.72 2.794 5.514 5.511 13.73 21.3 LaCrO3 32.63 2.741 5.493 5.477 7.745 27.9 LaCr0.85Ru0.15O3 31.82 2.761 5.515 5.512 7.793 18.3 1 Peak position of (110)/(104) and (112) from XRD. 2 Particle size (nm) calculated from the most intense and non-overlapped XRD peak (110)/(104) and (112) using the Scherrer equation.

2.2.3. XANES (X-Ray Absorption Near Edge Structure) To verify the Ru doping and chemical state of the doped Ru, XANES is a useful analytic tool to understand the chemical structure of each perovskite elements and Ru. The B-site elements can also inform the partial replacement of Ru, and Ru XANES provides a direct information on the chemical state that is important at the reforming reactions. Moreover, as we used an autothermal reforming reaction condition in this study, the oxygen species is also very important due to the interaction between all reactants and catalysts. Figure4a,b both for normalized Co and Cr K-edge XANES spectra of LaCo 0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts, respectively, show the typical shape of the white-lines, indicating well produced perovskite structure. This main peak is attributed to the 1s–4p dipole transition. At the normalized Co and Cr K-edge XANES sepctra for the Ru doped and undoped perovskites, the line shapes are very analogous, showing that the local and structure electronic of doped and undoped perovskites are very similar, respectively. Generally, it is possible to understand the oxidation state from the position and intensity of the adsorption edge. Each position indicates mainly CoII, III and Cr II, III, which are in allowance with the oxidation states in the perovskite structure [38,39]. However, after the Ru substitution for both perovskite catalysts, a slight shift and decrease of the white-line was observed at both compositions with Ru. This reflects on an increase of the degree of electron disorder of Co and Cr, proving the Ru doping into the B-site at the perovskite lattice [40,41]. It relates to the change of the constant Co/Cr–O bond length in each LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalyst, which can be correlated to the change of the O bonding structure. However, the chemical bonding character of Ru is the most important study to investigate how the Ru electronic and geometric structures affect the activity and durability at the LCO-ATR reaction conditions. From Figure4c, the normalized Ru K-edge XANES spectra of LaCo 0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts showed a similar shape of the major peaks. The first thing to explore is the presence of the pre-edge peak, which usually indicates the local structure of Ru [42–46]. For both perovskites, there were no pre-edge peak, which conveyed a strongly stabilized local symmetry of Ru, like as the nearly regular octahedral symmetry at the orthorhombic lattice of the Cr based perovskite. Essentially, the intense and sharp resonance peaks of the Ru species were identical to the RuO2 reference. Though, there was a change in the intensity and shifts in the energies comparing to the Ru references, due to the different electronic structures. Both perovskites show shifts to a higher energy from the increased intensity of the position at 22,135 eV, and further increased at the Ru in Cr based perovskite was seen. The peak positions in these major edge regions are assigned to the dipole transition of 1s 5p, which can be translated to Ru(4+δ)+ species [42–44]. As the higher activated charge of Ru → principally contributes to the increase in the transition energy, the further shift of the energy region (4+δ)+ for LaCr0.85Ru0.15O3 catalyst indicates in relatively higher portion of Ru at the doped perovskite Catalysts 2020, 10, 1039 8 of 16

structure, which may be able to display a relatively higher activity than the LaCo0.85Ru0.15O3 catalyst underCatalysts the 2020 LCO-ATR, 10, x FOR PEER reaction REVIEW conditions. 8 of 16

FigureFigure 4.4. XASXAS analysis analysis of of the the normalized normalized XANES XANES spectra spectra of of ( (aa)) Co Co K-edge K-edge (LaCoO (LaCoO3 3 andand LaCoLaCo0.850.85Ru0.150.15OO3),3 ),(b (b) )Cr Cr K-edge K-edge (LaCrO (LaCrO3 3andand LaCr LaCr0.850.85RuRu0.15O0.153),O (3c),) Ru (c) RuK-edge K-edge (LaCo (LaCo0.85Ru0.850.15RuO30.15 andO3 andLaCr LaCr0.85Ru0.850.15RuO3 0.15includingO3 including RuO2, RuO RuCl2,3 RuCl, Ru3 ,foil Ru foilas references) as references) and and (d) ( dO) OK-edge K-edge (LaCoO (LaCoO3,3 , LaCoLaCo0.850.85Ru0.15OO3,3 LaCrO, LaCrO3 and3 and LaCr LaCr0.850.85RuRu0.15O0.153).O 3).

ItFrom is also Figure worthy 4c, to studythe normalized about the oxygenRu K-edge species, XANES which shouldspectra beof di ffLaCoerent0.85 forRu0.15 eachO3 ofand the LaCoLaCr0.850.85Ru0.15OO3 3catalystsand LaCr showed0.85Ru0.15 a similarO3 catalysts shape (Figure of the4 majod). Generally,r peaks. The the first oxygen thing species to explore are divided is the bypresence two, surface of the adsorbedpre-edge peak, oxygen which and usually lattice oxygenindicates [17 the,20 local]. The structure amount of of Ru the [42–46]. surface For oxygen, both thatperovskites, is closely there related were to the no catalyticpre-edge reactions, peak, which is a veryconveyed important a strongly factor stabilized at the autothermal local symmetry reforming of reactionsRu, like usingas the heavy-hydrocarbonnearly regular octahedral feedstock. symmetr At they at normalized the orthorhombic O K-edge lattice XANES of the spectra Cr based of the LaCoperovskite.0.85Ru0.15 Essentially,O3 and LaCr the 0.85intenseRu0.15 andO3 sharpcatalysts resonance in Figure peaks4d, of regions the Ru for species O α at were ~533 identical eV and to O theβ at ~538RuO eV2 reference. are assigned Though, as surface there oxygen was a change atomsand in the lattice intensity oxygen and atom, shifts respectively. in the energies The Ocomparingα is assigned to asthe oxygen Ru references, atoms placed due to at the the different surface region electronic by a st transitionructures. ofBoth an Operovskites 1s electron show into theshifts unoccupied to a higher O 2penergy anti-bonding, from the increased and Oβ stated intensity the oxygenof the position atoms inat the22,135 structural eV, and oxide further phase increased by convoluting at the Ru in the Cr O 2pbased states perovskite in the perovskite was seen. lattice The peak [45, 46positions]. From in the these diff majorerent shapeedge regions of the Oare K-edge assigned XANES to the spectra,dipole (4+δ)+ thetransition content of of 1 thes→5 Opα, whichsurface can oxygen be translated at the LaCr to Ru0.85Ru species0.15O3 catalyst [42–44]. was As the much higher larger activated than the charge Oα at theof Ru LaCo principally0.85Ru0.15 Ocontributes3 catalyst, to maybe the increase due to thein th structurale transition changes energy, after the further Ru doping. shift Thisof the relatively energy largerregion amount for LaCr of surface0.85Ru0.15O oxygen3 catalyst with indicates an activated in relatively Ru in the perovskitehigher portion structure of Ru can(4+δ)+ provide at the adoped higher activityperovskite and evenstructure, durability which on themay LCO-ATR be able reactionsto display for eaffi cientrelatively hydrogen higher production. activity than the LaCo0.85Ru0.15O3 catalyst under the LCO-ATR reaction conditions. 2.3. LCO-ATRIt is also byworthy Various to Reactionstudy about Temperature the oxygen species, which should be different for each of the LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts (Figure 4d). Generally, the oxygen species are divided Under the prepared micro-tubular catalysts of LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3, an autothermalby two, surface reforming adsorbed reaction oxygen byand using lattice the oxygen characterized [17,20]. The LCO amount fuel wasof the carried surface out oxygen, at various that is closely related to the catalytic reactions, is a very important factor at the autothermal reforming operation temperatures in a range of 750–950 ◦C at the fixed conditions of H2O/O2/C = 1.5/0.4/1 and reactions using 1heavy-hydrocarbon feedstock. At the normalized O K-edge XANES spectra of the GHSV = 4000 h− . The fuel conversion and the selected gas products in mol % were plotted in Figure5 LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts in Figure 4d, regions for Oα at ~533 eV and Oβ at ~538 to compare the catalytic behavior under operating conditions with high C–H, S, N concentrations. eV are assigned as surface oxygen atoms and lattice oxygen atom, respectively. The Oα is assigned as As shown in Figure5, it was obvious that the H 2 production increases at the elevating temperature, oxygen atoms placed at the surface region by a transition of an O 1s electron into the unoccupied O which is expected from the general idea of the trend in increasing fuel conversions. Furthermore, 2p anti-bonding, and Oβ stated the oxygen atoms in the structural oxide phase by convoluting the O it can be also conveyed that the higher temperature facilitates the activation of C–H bonds and easily 2p states in the perovskite lattice [45,46]. From the different shape of the O K-edge XANES spectra, cuts these bonds to create H2 gas products [16]. In the line of this trend, the lower proportion of the content of the Oα surface oxygen at the LaCr0.85Ru0.15O3 catalyst was much larger than the Oα at non-reformed hydrocarbons (CH4,C2H4,C2H6, and C3H6) in the products was seen when the increase the LaCo0.85Ru0.15O3 catalyst, maybe due to the structural changes after Ru doping. This relatively in H was also accompanied by a decrease in CO . The highest H production was revealed at the larger2 amount of surface oxygen with an activated xRu in the perovskite2 structure can provide a higher temperature of 900 C for both perovskite catalysts. Generally, the hydrogen production by the activity and even durability◦ on the LCO-ATR reactions for efficient hydrogen production. reforming reaction takes place at the temperature of 800–850 ◦C, especially for heavy-hydrocarbons. The2.3. relativelyLCO-ATR highby Various reaction Reaction temperature Temperature of 900 ◦C may come from the C–H composition of the LCO fuel. As from the characterization results of LCO (Table1), the high content with over 30% of the 3 ringsUnder aromatic the compounds, prepared micro- such astubular phenanthrene, catalysts anthracene, of LaCo0.85 andRu fluorene,0.15O3 and etc., LaCr might0.85Ru be0.15 relativelyO3, an autothermal reforming reaction by using the characterized LCO fuel was carried out at various operation temperatures in a range of 750–950 °C at the fixed conditions of H2O/O2/C = 1.5/0.4/1 and GHSV = 4000 h−1. The fuel conversion and the selected gas products in mol% were plotted in Figure 5 to compare the catalytic behavior under operating conditions with high C–H, S, N concentrations.

Catalysts 2020, 10, 1039 9 of 16 difficult to crack the C–C and C–H bonding compared to the compounds with lower ring numbers. The high possession of the compounds with 3 rings also affected to the relatively low H2 production with the maximum value of 48 mol % at 900 ◦C for the LaCo0.85Ru0.15O3 catalyst, due to the relatively low hydrogen density from this high 3–4 rings content, compared to the other heavy-hydrocarbon feedstocks. At the higher temperature of 950 ◦C, slight decrease in H2 production was observed for both catalysts while CO2 (by-products) were detected to be increased. This was due to a higher combustion rate of the intermediate of C–H activation, which may make it difficult to convert reactants into the desired product of H2. At the same reaction conditions of LCO-ATR, LaCo0.85Ru0.15O3 catalyst shows more efficient initial H2 production rate than the LaCr0.85Ru0.15O3 catalyst, even though the characterization results demonstrated a more active model for the LaCr0.85Ru0.15O3 catalyst by having active Ru and O species. Meanwhile, LaCo0.85Ru0.15O3 catalyst includes Co species which is well known catalysts at oxidative reactions [38,47]. Therefore, the relatively high initial catalytic activity may come from the synergy effect of Co and Ru at the LCO autothermal reforming reaction including Catalysts 2020, 10, x FOR PEER REVIEW 9 of 16 oxygen as a reactant.

Figure 5. Reformate (H2, CO, CO2, and C1,2,3Hn) productions (mol%) from LCO-ATR tests under the Figure 5. Reformate (H2, CO, CO2, and C1,2,3Hn) productions (mol %) from LCO-ATR tests under the temperature range of 750–950 °C (H2O/O2/C = 1.5/0.4/1, GHSV = 4000 h−1) for1 (a) LaCo0.85Ru0.15O3 and temperature range of 750–950 ◦C (H2O/O2/C = 1.5/0.4/1, GHSV = 4000 h− ) for (a) LaCo0.85Ru0.15O3 (b) LaCr0.85Ru0.15O3 catalysts. and (b) LaCr0.85Ru0.15O3 catalysts.

2.4. Long-TermAs shown Test in ofFigure LCO-ATR 5, it Reactions was obvious that the H2 production increases at the elevating temperature, which is expected from the general idea of the trend in increasing fuel conversions. Figure6 displays the long-term LCO-ATR reactions over 25 h for LaCo 0.85Ru0.15O3, Furthermore, it can be also conveyed that the higher temperature facilitates the activation of C–H LaCr0.85Ru0.15O3 and Pt-GDC reference catalysts. The product distributions of H2, CO, CO2 and bonds and easily cuts these bonds to create H2 gas products [16]. In the line of this trend, the lower C1,2,3Hx were evaluated to investigate the stability of each catalyst under this severe reaction conditions. proportion of non-reformed hydrocarbons (CH4, C2H4, C2H6, and C3H6) in the products was seen The results were screened by the typical data scattering for this kind of reaction type due to the when the increase in H2 was also accompanied by a decrease in COx. The highest H2 production was non-homogeneous mixture of the reactants [48]. It was interesting that the prepared Ru doped catalysts revealed at the temperature of 900 °C for both perovskite catalysts. Generally, the hydrogen exhibited good reforming efficiencies for LCO-ATR with harsh reaction conditions. This may not be production by the reforming reaction takes place at the temperature of 800–850 °C, especially for only due to the stabilization of the doped Ru into the perovskite structure but also the micro-tubular heavy-hydrocarbons. The relatively high reaction temperature of 900 °C may come from the C–H feature with relatively high surface area and efficient mass/heat transfer property. As we investigated at composition of the LCO fuel. As from the characterization results of LCO (Table 1), the high content the temperature dependent results, the initial performance of H production for the LaCo Ru O with over 30% of the 3 rings aromatic compounds, such as phenanthrene,2 anthracene, and0.85 fluorene,0.15 3 catalyst (48 mol %) basically started with a higher value than the LaCo Ru O catalyst (43 mol %). etc., might be relatively difficult to crack the C–C and C–H bonding 0.85compared0.15 3to the compounds However, the highest initial performance was revealed at the Pt-GDC reference catalyst (56 mol %) with lower ring numbers. The high possession of the compounds with 3 rings also affected to the even at the similar amount of noble metal (5 wt %) as an active site, since platinum is usually highly relatively low H2 production with the maximum value of 48 mol% at 900 °C for the LaCo0.85Ru0.15O3 activecatalyst, in due most to of the the relatively catalytic low reactions. hydrogen density from this high 3–4 rings content, compared to the other heavy-hydrocarbon feedstocks. At the higher temperature of 950 °C, slight decrease in H2 production was observed for both catalysts while CO2 (by-products) were detected to be increased. This was due to a higher combustion rate of the intermediate of C–H activation, which may make it difficult to convert reactants into the desired product of H2. At the same reaction conditions of LCO- ATR, LaCo0.85Ru0.15O3 catalyst shows more efficient initial H2 production rate than the LaCr0.85Ru0.15O3 catalyst, even though the characterization results demonstrated a more active model for the LaCr0.85Ru0.15O3 catalyst by having active Ru and O species. Meanwhile, LaCo0.85Ru0.15O3 catalyst includes Co species which is well known catalysts at oxidative reactions [38,47]. Therefore, the relatively high initial catalytic activity may come from the synergy effect of Co and Ru at the LCO autothermal reforming reaction including oxygen as a reactant.

2.4. Long-Term Test of LCO-ATR Reactions

Figure 6 displays the long-term LCO-ATR reactions over 25 h for LaCo0.85Ru0.15O3, LaCr0.85Ru0.15O3 and Pt-GDC reference catalysts. The product distributions of H2, CO, CO2 and C1,2,3Hx were evaluated to investigate the stability of each catalyst under this severe reaction conditions. The results were screened by the typical data scattering for this kind of reaction type due to the non- homogeneous mixture of the reactants [48]. It was interesting that the prepared Ru doped catalysts exhibited good reforming efficiencies for LCO-ATR with harsh reaction conditions. This may not be only due to the stabilization of the doped Ru into the perovskite structure but also the micro-tubular feature with relatively high surface area and efficient mass/heat transfer property. As we investigated at the temperature dependent results, the initial performance of H2 production for the LaCo0.85Ru0.15O3

Catalysts 2020, 10, x FOR PEER REVIEW 10 of 16

catalyst (48 mol%) basically started with a higher value than the LaCo0.85Ru0.15O3 catalyst (43 mol%). However, the highest initial performance was revealed at the Pt-GDC reference catalyst (56 mol%) Catalystseven at2020 the, 10 similar, 1039 amount of noble metal (5 wt %) as an active site, since platinum is usually highly10 of 16 active in most of the catalytic reactions.

Figure 6. Products distribution (mol %) of the reformate (H2, CO, CO2, and C1,2,3Hn) during long-term Figure 6. Products distribution (mol%) of the reformate (H2, CO, CO2, and C1,2,3Hn) during long-term LCO-ATR reaction (25 h) for (a) LaCo0.85Ru0.15O3,(b) LaCr0.85Ru0.15O3 and (c) Pt-GDC reference LCO-ATR reaction (25 h) for (a) LaCo0.85Ru0.15O3, (b) LaCr1 0.85Ru0.15O3 and (c) Pt-GDC reference catalysts (H2O/O2/C = 1.5/0.4/1, 1127 K, GHSV = 4000 h− ). catalysts (H2O/O2/C = 1.5/0.4/1, 1127 K, GHSV = 4000 h−1). The stability of the prepared perovskite catalysts can be also examined by the long period on stream The stability of the prepared perovskite catalysts can be also examined by the long period on of the LCO-ATR reactions in comparison to the Pt-GDC reference catalyst (Figure6). The notable point stream of the LCO-ATR reactions in comparison to the Pt-GDC reference catalyst (Figure 6). The in Figure6a,b was that the Ru doped perovskite catalysts were not much su ffered from the decrease notable point in Figure 6a,b was that the Ru doped perovskite catalysts were not much suffered from on the H2 production by the catalyst deactivation, comparing to the Pt deposited GDC catalysts. the decrease on the H2 production by the catalyst deactivation, comparing to the Pt deposited GDC Even though the Pt based catalysts revealed a great initial capacity on H2 extraction, there was a catalysts. Even though the Pt based catalysts revealed a great initial capacity on H2 extraction, there hugewas a drop huge on drop the on catalytic the catalytic activity activity after after the 25the h 25 under h under high high content content of of S andS and N. N. This This result result waswas in anin agreementan agreement with with many many results results from from other other research research groups,groups, that the the Pt Pt is is drastically drastically deactivated deactivated underunder this this kind kind of of harshharsh reactionreaction conditions by by th thee sulfur sulfur poisoning poisoning and and maybe maybe coke coke formation formation at the at the metalmetal active active surface surface [[16–20].16–20]. The decrease in in the the H H22 productionproduction ability ability was was also also accompanied accompanied byby the the dramaticdramatic increase increase ofof thethe COCO22 molar percentage, as as shown shown in in Figure Figure 6c.6c. This This can can be be interpreted interpreted asas a a largelarge coke coke formation formation duedue toto thethe happening of of the the Boudouard Boudouard reaction reaction (2CO (2CO → COCO2 +2 +C).C). Not Not only only → sulfursulfur poisons poisons the thePt Pt activeactive surfacesurface for deactivation, deactivation, but but also also coking coking blocks blocks the the active active sites sites and and results results inin the the loss loss of of the the active active surfacesurface area [48,49]. [48,49]. Additionally, Additionally, much much more more coking coking is isknown known to tooccur occur at atthe the highhigh concentration concentration of of the the C–H C–H bond bond rings rings and and aromatic aromatic compounds, compounds, which which can can be be exactly exactly linked linked to to the LCOthe LCO compositions. compositions. Interestingly,Interestingly, a a comparable comparable activity activity and and great great stability stability with with almost almost no no deactivation deactivation was was achieved achieved for bothfor both Ru doped Ru doped perovskite perovskite catalysts, catalysts, as monitored as monitored in Figure in Figure6a,b. This 6a,b. substantial This substantial stability stability of the catalystsof the demonstratescatalysts demonstrates high tolerance high againsttolerance sulfur against poisoning sulfur poisoning and coking and on coking the LCO on heavy-hydrocarbonthe LCO heavy- feedstockhydrocarbon with feedstock a large content with a of large C–H, content S, and Nof species.C–H, S, Whileand N therespecies. was While a slight there decrease was a in slight the H 2 decrease in the H2 production performance for the LaCo0.85Ru0.15O3 catalyst, it was surprising that the production performance for the LaCo0.85Ru0.15O3 catalyst, it was surprising that the LaCr0.85Ru0.15O3 LaCr0.85Ru0.15O3 catalyst shows small but a gradual increase on the capability of the H2 extraction from catalyst shows small but a gradual increase on the capability of the H2 extraction from LCO reforming LCO reforming process, and cross over with the performance of the LaCo0.85Ru0.15O3 catalyst. Besides, process, and cross over with the performance of the LaCo0.85Ru0.15O3 catalyst. Besides, as apart as apart from the trend of Pt-GDC, the CO2 production decreases against the H2 production, from the trend of Pt-GDC, the CO2 production decreases against the H2 production, indicating a low occurrenceindicating ofa carbonlow occurrence deposition of oncarbon the catalyst deposition surface. on the The catalyst reason forsurface. this remarkable The reason observation for this remarkable observation might be explained from the characterization above. As we previously might be explained from the characterization above. As we previously mentioned, the LaCr0.85Ru0.15O3 mentioned, the LaCr0.85Ru0.15O3 catalyst possesses a highly active Ru species which can be further catalyst possesses a highly active Ru species which can be further activated for better performance activated for better performance during the reforming reaction. In addition, the oxygen structure during the reforming reaction. In addition, the oxygen structure consisted of more surface oxygen that consisted of more surface oxygen that are active and easily react with the deposited S and C to release are active and easily react with the deposited S and C to release as gas products with C-O and S-O as gas products with C-O and S-O active bonds, respectively, resulting in the good catalyst stability active bonds, respectively, resulting in the good catalyst stability at the LCO-ATR condition. at the LCO-ATR condition. 2.5. Post Characterization of the Used Perovskite Catalysts 2.5. Post Characterization of the Used Perovskite Catalysts In Figure7, the used perovskite catalysts were post-characterized to investigate the deactivation behavior during the LCO-ATR reactions. It is important to analyze the presence of the C, N and S contents, because these can be a clue on the stability comparing both perovskites and even Pt-GDC reference catalysts. From the SEM image in Figure7a,b, both used perovskite catalysts retained their hollow fibrous structure, proving a great physical stability of the catalysts. When we look closely on the fiber surface, it was smooth and clear due to a light carbon coverage after the LCO-ATR. However, Catalysts 2020, 10, x FOR PEER REVIEW 11 of 16

In Figure 7, the used perovskite catalysts were post-characterized to investigate the deactivation behavior during the LCO-ATR reactions. It is important to analyze the presence of the C, N and S contents, because these can be a clue on the stability comparing both perovskites and even Pt-GDC Catalystsreference2020 catalysts., 10, 1039 From the SEM image in Figure 7a,b, both used perovskite catalysts retained their11 of 16 hollow fibrous structure, proving a great physical stability of the catalysts. When we look closely on the fiber surface, it was smooth and clear due to a light carbon coverage after the LCO-ATR. However, comparingcomparing to to the the fresh fresh and and after after Pt-GDC Pt-GDC catalysts catalysts in Figurein Figure7c,d, 7c,d, there there was awas large a formationlarge formation of coking of aroundcoking thearound catalyst, the catalyst, which make which it make difficult it difficult to even to distinguish even distinguish the Pt-GDC the Pt-GDC grain grain morphology. morphology. This is aThis clear is evidence a clear evidence of the huge of the drop huge of the drop H2 ofextraction the H2 extraction ability from ability the LCOfrom feedstock.the LCO feedstock. Moreover, onMoreover, this decrease, on this it is decrease, expected it to is have expected large sinteringto have oflarge the sintering Pt nanoparticles of the Pt on nanoparticles the reference catalysts.on the Onreference the other catalysts. hand, due Onto the the other trapped hand, Ru due position to the in trapped the perovskite Ru position framework in the perovskite [17,28,29], framework the Ru at the developed[17,28,29], perovskitethe Ru at the catalysts developed should perovskite have great cataly resistancests should to the have sintering great resistance which could to the be sintering confirmed fromwhich the could stable be H confirmed2 production from behavior the stable from H2 theproduction LCO feedstock behavior as from well. the LCO feedstock as well.

Figure 7. SEM images of used (a) LaCr0.85Ru0.15O3, (b) LaCo0.85Ru0.15O3 catalysts, and (c) fresh/(d) used Figure 7. SEM images of used (a) LaCr0.85Ru0.15O3,(b) LaCo0.85Ru0.15O3 catalysts, and (c) fresh/(d) used Pt-GDCPt-GDC catalyst catalyst after after LCO-autothermalLCO-autothermal reformingreforming (ATR) reactions for for 25 25 h, h, as as well well as as (e ()e )TG TG analysis. analysis.

ForFor further further investigation, investigation, the the amount amount of theof depositedthe deposited carbon carbon was calculatedwas calculated by the by TGA the analysis TGA inanalysis Figure 7ine. Figure Each used 7e. Each catalyst used was catalyst loaded was in loaded the TGA in andthe theTGA weight and the loss weight during loss the during increasing the increasing temperature was monitored under air flow. Generally, the carbon species combusted from temperature was monitored under air flow. Generally, the carbon species combusted from 400–500 ◦C, which400–500 can °C, be which exactly can seen be atexactly the Pt-GDC seen at TGA the Pt-G plot.DC An TGA extremely plot. An large extremely weight large loss of weight over 30%loss wasof observedover 30% and was this observed value canand bethis confirmed value can by be the conf SEMirmed results. by the On SEM the results. other hand, On the relatively other hand, small amountrelatively of carbonssmall amount is measured of carbons for the isperovskite measured catalystsfor the perovskite and even halfcatalysts of the and carbon even was half deposited of the carbon was deposited at the LaCr0.85Ru0.15O3 catalyst, which clearly prove the good stability under the at the LaCr0.85Ru0.15O3 catalyst, which clearly prove the good stability under the harsh reaction conditions.harsh reaction The CHNSconditions. analysis The results, CHNS summarized analysis results, in Table summarized4, provide more in Table information 4, provide on N more and S information on N and S species deposition on the used catalysts after the LCO-ATR that includes species deposition on the used catalysts after the LCO-ATR that includes high content of S and N. As a high content of S and N. As a result, the quantity of N and S residues deposited on used Pt-GDC result, the quantity of N and S residues deposited on used Pt-GDC catalyst is highly correlated with the catalyst is highly correlated with the concentrations of S, N, and aromatic species contained in the concentrations of S, N, and aromatic species contained in the LCO fuels, representing low tolerance on LCO fuels, representing low tolerance on all of the presented species. With the order of the deposited all of the presented species. With the order of the deposited carbon amount, relatively lower amount carbon amount, relatively lower amount of S and N species was discovered at the LaCr0.85Ru0.15O3 of S and N species was discovered at the LaCr0.85Ru0.15O3 catalyst comparing to the LaCo0.85Ru0.15O3 catalyst comparing to the LaCo0.85Ru0.15O3 catalyst. Therefore, we may conclude that this better catalyst. Therefore, we may conclude that this better tolerance under severe LCO reforming reaction is tolerance under severe LCO reforming reaction is in accordance with the higher reforming efficiency in accordance with the higher reforming efficiency and stability, which is strongly associated mainly and stability, which is strongly associated mainly with higher possession of the active Ru and O at a with higher possession of the active Ru and O at a modified electronic perovskite structure. modified electronic perovskite structure.

Table 4. Weight loss and compositions of C, H, N, S of the used LaCr0.85Ru0.15O3, LaCo0.85Ru0.15O3 Table 4. Weight loss and compositions of C, H, N, S of the used LaCr0.85Ru0.15O3, LaCo0.85Ru0.15O3 and and Pt-GDC catalysts after LCO-ATR for 25 h. Pt-GDC catalysts after LCO-ATR for 25 h. 1 2 Catalysts Weight Loss (wt %)Composition 2(%) Catalysts Weight Loss 1 (wt %) Carbon Hydrogen(%) Nitrogen Sulfur Pt-GDC 31.87 94.87 0.51 0.43 4.19 LaCo0.85Ru0.15O3 2.56 95.79 0.82 0.26 3.01 LaCr0.85Ru0.15O3 1.12 96.74 0.82 0.15 2.29 1 2 Weight loss from 600 ◦C (TGA analysis). Compositions of C, H, N and S after LCO-ATR for 25 h (CHNS analysis). Catalysts 2020, 10, 1039 12 of 16

3. Materials and Methods Light cycle oil (LCO): A full-range of the industrially produced LCO, supplied by GS-Caltex Co., was used as the feedstock in this study. Through oxidative desulfurization (ODS), the received LCO was pre-treated to remove 4,6-DMDBT selectively in GS-Caltex Co (Seoul, Korea). The carbon, nitrogen and sulfur species in the feedstock and liquid products were monitored by HT (high temperature) GC-AED. The HT GC-AED system includes a Hewlett-Packard gas chromatograph (Agilent 7890, Agilent, Santa Clara, CA, United States) equipped with J&W DB-1 metal capillary column coupled to an atomic emission detector (JAS2390AA). The inlet was programmed to increase from 50 to 500 ◦C in 9 min. The inlet was held at constant pressure and the column flow rate was 12 mL/min at 30 ◦C. The oven was programmed to increase from 30 to 450 ◦C at 30 ◦C/min. The transfer line between the GC and the AED was 450 ◦C and cavity temperature was 430 ◦C. The compounds in the LCO feed was analyzed using 2D GC-ToF MS. 2D GC-ToF MS system consists a 7890B gas chromatograph and a 7200B mass spectrometer (Agilent Technologies, Santa Clara, CA, United States). In the 2D GC system, two different columns were applied; a nonpolar column was used as the first column and a polar column was used as the second column, which eluted compounds by the order of their polarity and boiling point, respectively. In the 2D GC-ToF MS spectra, the horizontal axis displays the boiling point and the vertical axis represents the polarity. The first column was a 30 m 0.32 mm (I.D.) capillary × tube and the temperature ramp rate is at 5 ◦C/min. After cooling, the sample was introduced into the second column. The second column was opened the GC with the same modulation time using short columns (length: 2 m, I.D.: 0.18 mm). Because both columns are treated at a same oven, they are nearly constant in the oven when the sample reaches the second column. An ionization source ionized the separated compounds, and a constant voltage accelerated the obtained ions. Catalyst preparation: Lanthanum(III) nitrate nonahydrate (La(NO ) 9H O, 99%, Sigma-Aldrich, 3 3· 2 St. Louis, Missouri, United States), Cobalt(II) nitrate hexahydrate (Co(NO ) 6H O, 98%, Sigma-Aldrich, 3 2· 2 St. Louis, Missouri, United States), chromium(III) nitrate nonahydrate (Cr(NO ) 9H O, 99%, Yakuri), 3 3· 2 and ruthenium(III) nitrosyl nitrate (HN4O10Ru, 99%, Sigma-Aldrich, St. Louis, Missouri, United States) were purchased as precursors for perovskite synthesis. The Ru doped perovskite micro-tubular fibers were synthesized by carbon template method using ACF (OG-20A, Osaka Gas Co. Ltd., Chuo-ku, Osaka, Japan) for hollow fiber feature, which can be carried out by mild heat treatment at air gas through the combustion of the carbon content [16]. The perovskite ion elements are deposited on the carbon surface by an aqueous impregnation for a rapid and convenient synthesis. aqueous HNO3 (6 M, Duksan, Ansan-si Gyeonggi-do, Korea) and H2SO4 (6 M, Duksan, Ansan-si Gyeonggi-do, Korea) were used to sequentially treat the template to a negatively charged surface. The treated ACF were mixed with a III III III III mixed aqueous solution and stirred for 24 h with a stoicmetric of La /Co 0.85(Cr 0.85)/Ru 0.15 ions. The Ru content were fixed as around 5 wt %. Then, the final perovskite catalysts of LaCo0.85Ru0.15O3 and LaCr0.8Ru0.2O3 were obtained by the calcination under sufficient airflow at 1027 K for 6 h. To compare the structural change, LaCoO3 and LaCrO3 were prepared under same method. Moreover, 5 wt % Pt–GDC (gadolinium-doped CeO2, Sigma-Aldrich, St. Louis, Missouri, United States) was prepared by incipient wetness impregnation [17]. Characterization: Scanning electron microscopy (SEM, JSM-6701F, JEOL, Akishima, Tokyo, Japan) at 15 kV, equipped with an energy-dispersive X-ray (EDX) spectrometer, is used to investigate the morphology of the micro-tubular feature and the chemical composition of each samples. X-ray diffraction (XRD, Miniflex AD11605, Rigaku, Akishima, Tokyo, Japan) is applied to scan the crystal structure by using Cu-Kα radiation (λ = 1.5405 nm) at 30 kV/30 mA. A distribution graph of N2 adsorption-desorption at 77 K (ASAP 2010, Micromeritics, Norcross, GA, United States) was obtained to determine the Brunauer–Emmett–Teller (BET) surface area, pore volume, and pore diameter using the BET equation. The X-ray absorption spectroscopy (XAS) results were collected at the Pohang Accelerator Laboratory (PAL, Pohang, Korea), beamline 10C (Multipole-wiggler, Ge 13-element detector) and 10D (Bending magnet, Phoibos 150). The X-ray absorption near edge structure (XANES) data at Co, Cr and Ru K-edges were collected in transmission mode at beamline 10C Wide XAFS using Catalysts 2020, 10, 1039 13 of 16

gas-ionization detectors. The Ru spectra were calibrated by comparing with RuO2, RuCl3 and Ru metal references. The XANES data of O K-edge were collected at beamline 10D XAFS. To analyze the deposited elements after the LCO reforming, thermogravimetric analysis (TGA) was performed by a 1 heating range from 30 ◦C to 900 ◦C (5 ◦C min− ) under air flow, and CHNS analysis was carried out by the PerkinElmer 2400 Series II. LCO-ATR (autothermal reforming): ATR of the LCO fuels was carried out in an atmospheric fixed-bed stainless steel flow reactor. The temperature of the reactor was controlled using thermocouples that were inserted coaxially into the catalyst bed center. To provide a homogeneous supply of the fuels, the fuels were fed into the reactor using a liquid pump with ultrasonic injector. For LCO-ATR experiments using the catalysts, the temperature was controlled between 750 and 950 ◦C at atmospheric pressure and the molar ratios of H2O/C = 1.5/1 and O2/C = 0.4/1 were applied using a mass flow controller. 1 The formula of υ0/V is used to fix the gas hourly space velocity (GHSV) of 4000 h− , where υ0 is the volumetric flow rate of the reactants entering into the reactor and V is the volume of the catalyst bed. By using an optimized operation condition, long-term reforming tests of each catalysts was carried out at 1127 K for 25 h. The reformates of H2, CO2, CO, and C1,2,3Hn (CH4 + C2H4 + C2H6 + C3H6) were periodically measured at the online GC (Younglin-6000, Younglin, Anyang-si, Gyeonggi-do, Korea) equipped with TCD and FID, which were programmed to operate under high-sensitivity conditions. The fuel conversions at the liquid base were measured by the outflow of LCO after tests by certain running time and the distributions of the products were averaged from the steady state. - Product distribution: (%) (i: H2, CO, CO2, and C1,2,3Hn (CH4 + C2H4 + C2H6 + C3H6)):

( mole i) out P 100 (1) mole iout ×

4. Conclusions

Motivated by the urgent need for a development of the efficient H2 production system, a feedstock of LCO is firstly utilized at an autothermal reforming system. Due to economical reasons, we found that LCO could be a promising candidate as a fuel when an effective catalyst is developed with a high tolerance on deactivation at severe reaction conditions. From the LCO characterization, a high content of C–H compounds that are mainly consisted of 3–4 ring bonds were detected. Moreover, large amount of sulfur species with nitrogen compounds were also measured, which caused outstanding catalysts deactivation from the LCO-ATR results by Pt based reference catalyst. Two different micro-tubular perovskite catalysts were prepared with a comparable amount of Ru doping (around 5 wt %). Both LaCo0.85Ru0.15O3 and LaCr0.85Ru0.15O3 catalysts were finely synthesized without any impurities and show typical perovskite structure. The doped Ru was stabilized into the B-site, but revealed a different Ru chemical bonding phase at the two different perovskite lattices, which closely correlated to the O chemical structure. These modified chemical structures provided the good stability with a comparable capability of H2 extraction from the LCO-ATR reactions. The greater stability was also confirmed by post-characterization of the used perovskite catalysts, analyzing the relatively low amount of the deposited C, S, N species. From all the results, we can insist that the proposed catalyst structure may demonstrate a clue on utilizing LCO as feedstock on H2 production through an autothermal reforming reaction, in the future.

Supplementary Materials: The following is available online at http://www.mdpi.com/2073-4344/10/9/1039/s1, Figure S1: Additional SEM image and EDX mapping images of (a) LaCr0.85Ru0.15O3 and (b) LaCo0.85Ru0.15O3, including elemental analysis results. Author Contributions: Conceptualization, Y.J. and J.-i.P.; methodology, Y.J.; validation, Y.J., J.-i.P. and Y.S.; formal analysis, H.-K.J. and C.-I.P.; investigation, H.-K.J. and C.-I.P.; resources, J.-i.P.; data curation, Y.J.; writing—original draft preparation, Y.J.; writing—review and editing, J.-i.P.; visualization, H.-K.J. and C.-I.P.; supervision, Y.S. and J.-i.P. All authors have read and agreed to the published version of the manuscript. Catalysts 2020, 10, 1039 14 of 16

Funding: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1F1A107320111), and was also carried out within the framework of the NRF-2019R1F1A1060122. Conflicts of Interest: The authors declare no conflict of interest.

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