石 油 学 会 誌 Sekiyu Gakkaishi, 39, (3), 211-221 (1996) 211
[Regular Paper] Hydrodesulfurization of Dibenzothiophene Catalyzed by Supported Metal Carbonyl Complexes (Part 5) Catalysts for Hydrodesulfurization Prepared from Alumina- supported Ruthenium Carbonyl-Alkali Metal Hydroxide Systems
Atsushi ISHIHARA*, Masatoshi NOMURA, Nobuaki TAKAHAMA, Koichi HAMAGUCHI, and Toshiaki KABE
Dept. of Applied Chemistry, Faculty of Technology, Tokyo University of Agriculture & Technology, Nakamachi, Koganei, Tokyo 184
(Received August 10, 1995)
In hydrodesulfurization of dibenzothiophene (DBT) catalyzed by sulfided alumina-supported ruthenium compounds, the effects of addition of alkali metal hydroxide on the catalytic activity and product selectivity were investigated. When sodium hydroxide was added to catalysts derived from alumina-supported Ru3(CO)12, the conversion of DBT remarkably increased from 44 to 71%. It was essential to obtain the high catalytic activity and, therefore, that after the reaction of Ru3(CO)12 with sodium hydroxide, in advance, to give a ruthenium hydride Na[HRu3(CO)11], the hydride was supported on alumina. By the reaction of RuCl3, Ru(acac)3 (acac=acetylacetonate) and Ru3(CO)12 with cesium hydroxide and products supported on alumina, the activity increased in the order RuCl3-CsOH/ Al2O3
1. Introduction is most active for HDS of dibenzothiophene (DBT) among the transition metal sulfides, much atten- The recent air pollution in urban areas is one of tion was focused on HDS catalyzed by ruthenium serious problems in the world and deep hydro- sulfide, over the last decade2)-10). Lacroix et al.2) desulfurization (HDS) of light gas oil and develop- confirmed that unsupported RuS2 was most active, ment of the new catalysts for this purpose are even in a flow system for HDS of dibenzothiophene needed extensively. One method to prepare HDS (DBT), among the transition metal sulfides. catalysts with higher activity is to improve the Vrinat et al.3) reported, on HDS of thiophene, that traditional alumina-supported CoMo, NiMo and NixRu1-xS and CoxRu1-xS among the mixed sulfide NiW catalysts by expanding the surface area of solid solutions11), prepared from RuS2 and CoS2 or alumina and increasing the metal loading. An NiS2, exhibited activities higher than that of RuS2, alternative is to develop new generation of catalysts CoMoS or NiMoS. which have the properties different from that of the It can be expected that the deposition of ruthe- present Co, Ni, Mo and W-based catalysts. Since nium sulfide onto supports with large surface Pecoraro and Chianelli1) have given a clue to the areas, such as alumina, silica, silica-alumina, zeo- novel catalysts by reporting that ruthenium sulfide lite etc., increases catalytic activity per ruthenium atom. This approach is also economical because * To whom correspondence should be addressed. ruthenium is one of noble metals. Some groups
石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 212 have already performed HDS catalyzed by sup- In the present study, HDS of DBT, catalyzed by ported ruthenium sulfide. Harvey and Matheson alkali-promoted ruthenium catalysts, has been reported HDS of benzothiophene with catalysts investigated in a pressurized flow reactor. The derived from [Ru(NH3)6]+, Ru3(CO)12 and RuCl3 activity of the catalyst derived from the alumina- supported on alumina and zeolite in a batch supported Ru3(CO)12-alkali metal hydroxide sys- system4). Mitchell et al. performed HDS of thio- tem, where Ru3(CO)12 reacts with alkali metal phene with the catalyst derived from alumina- hydroxide to give an anionic ruthenium hydride supported Ru(III) acetate5). Kuo et al.6) and De complex M[HRu3(CO)11] (M=alkali metal), is Los Reyes et al.7) used catalysts derived from compared with that of catalysts derived from alkali alumina-supported RuCl3 and Ru3(CO)12 in HDS promoted alumina-supported Ru(acac)3 and of thiophene. With these catalysts, the HDS ac- RuCl3. It was found, that the addition of alkali tivity was rather low probably because sulfidation metal remarkably increased the activities of of ruthenium species was incomplete and that ruthenium catalysts, and that the catalyst derived RuS2 on alumina is unstable in hydrogen atmo- from the alumina-supported anionic ruthenium sphere. Chary et al.8) compared RuS2/Al2O3 carbonyl is the most active for HDS of DBT. with MoS2/Al2O3 in HDS of thiophene and O2 Characterization of ruthenium catalysts by means chemisorption. These HDS reactions, however, of NO chemisorption and XPS measurement was were performed in atmospheric pressure, and so far also performed. Preliminary results appear in the the activities of the catalysts derived from the literature21). supported ruthenium in a pressurized flow system have not yet been clarified in comparison with 2. Experimental those of Co-Mo/Al2O3 and Ni-Mo/Al2O3. Recently, Davis et al.9) reported on HDS of coal- 2.1. Materials derived naphtha catalyzed by alumina-supported Commercially available Ru3(CO)12, Ru(acac)3 metal sulfides in a pressurized flow system. (acac=acetylacetonate), RuCl3・nH2O (n=2-4) On the other hand, it was reported that catalysts (Nippon Chemcat), alkali metal hydroxides prepared from supported metal carbonyl com- (LiOH, NaOH, KOH, RbOH and CsOH), so- plexes are active in many catalytic reactions12)-14) dium salts (NaI, Na2S, NaHCO3, NaC2H3O2, and such as hydrogenation of olefin12), Fischer- NaHSO3), xylene and decalin (Kishida Chemicals) Tropsch reactions13), metathesis of olefin14) etc. were used without further purification. Tetrahy- Their reactivities in the HDS of thiophenes, drofuran (THF) was distilled from sodium benzo- especially DBT, which is a key compound in phenone ketyl. Alumina was gamma-aumina desulfurization of heavier feedstock, such as light supplied from Japan Ketjen Co., Ltd. (260m2/g) oil, have been scarcely investigated. Recently, which was crushed and screened to provide 0.84- to there have been only a few examples of catalysts, 1.19-mm granules used in this work. Alumina derived from supported molybdenum carbonyls, was dried under vacuum at 350℃ for 4h prior to being active in HDS of thiophenes15),16). The use and stored in Ar atmosphere. Commercial authors have also reported that catalysts derived Co-Mo/Al2O3 was supplied from Japan Ketjen from supported anionic molybdenum carbonyls, Co., Ltd. (KF-124: MoO3, 12.3wt%; CoO, 3.8wt%; in HDS of DBT, are more active than conventional 274m2/g). Hydrogen, nitrogen (99.99%) and sulfided supported catalysts17)-19). In the course of hydrogen sulfide were obtained from Tohei this study, the authors became interested in the Chemicals. Hydrogen sulfide in hydrogen (H2S activity of supported ruthenium carbonyls in HDS 3%) and nitrogen monoxide (NO) were obtained of DBT. It has been reported, however, that from Takachiho Chemicals. NO was washed by catalyst derived from supported Ru3(CO)12 show- condensing in a trap filled with solid KOH at ed activity lower than that from supported -196℃ before use. RuCl34),6),7), forHDS of thiophene. The authors 2.2. Catalyst Preparation tried to prepare anionic metal carbonyl complexes 2.2.1. Ru3(CO)12, Ru(acac)3 or RuCl3-MOH/ with a metal-sulfur bond, because these complexes Al2O3 (M=Li, Na, K, Rb or Cs) and were effective for HDS of DBT catalyzed by Ru3(CO)12-NaX or Na2Y/Al2O3 (X=I, supported molybdenum carbonyls. It was found HCO3, C2H3O2, HSO3; YS) that catalyst derived from the alumina-supported 0.13mmol of Ru3(CO)12 (0.39mmol of Ru(acac)3 anionic ruthenium carbonyl was the most active or RuCl3) and 0-1.2mmol of an alkali metal salt for HDS of DBT, among catalysts derived from were dissolved in methanol or distilled water alumina-supported Ru3(CO)12, Ru(acac)3 (acac= (5ml) and stirred at 25℃ for 30min. After the acetylacetonate) and RuCl320). reaction, 0.46g of gamma-Al2O3 (>20 mesh) was
石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 213
added into the reaction mixture and stirred for 2h, times per hour, No sign of catalyst deactivation Solvent was removed in vacuo, was observed during the 10h run, 2,2,2, Ru3(CO)12/Al2O3, Ru(acac)3/Al2O3, and When Co-Mo/Al2O3 was used, presulfidation RuCl3/Al2O3 was performed at 400℃ for 3h, HDS of DBT was 0,084g of Ru3(CO)12 was dissolved in THF, carried out under the following conditions: 200- 0,46g of Al2O3 was added to the solution and 260℃; 50kg/cm2, H2 18l/h; WHSV 70h-1; DBT stirred for 2h, The solvent was removed in vacuo, Concentration of DBT in decalin, 1,0wt%; Cata- In the preparation of Ru(acac)3/Al2O3, meth- lyst, 0,2g, HDS of DBT catalyzed by the Ru3(CO)12- anol was used as the solvent, In RuCl3/Al2O3, 6CsOH/Al2O3 system was also carried out under distilled water was used as the solvent, Although the same conditions, ruthenium trichloride was purchased in RuCl3・ 2,4, Analytical nH2O (n=2-4), the amount of ruthenium was Reaction products were analyzed by gas chro- weighed with n=3, Other procedures were the matography with a FID detector (Shimadzu same as those for Ru3(CO)12/Al2O3, GC-9A) using a G-100 column (ID 1,2mm; film 2,2,3, RuCl3/Al2O3-I-NaOH thickness 1,0μm; length 40m) supplied from RuCl3/Al2O3 prepared above was calcined at Chemicals Inspection & Testing Institute or an 450℃ for 24h to prevent RuCl3 dissolving in to a OV-1 capillary column (ID 0,25mm×50m), solvent (RuCl3/Al2O3 in 2,2,2, was not calcined), 2,5, Infrared Measurement Then, the RuCl3/Al2O3 was suspended in meth- FTIR spectra of catalyst precursors were re- anol and 0,39mmol of NaOH was added, After corded on FT/IR-5300, Japan Spectroscopic Co,, the mixture was stirred for 2h, methanol was Ltd, removed in vacuo, 2,6, NO Chemisorption and XPS Measurement 2,2,4, Ru3(CO)12/Al2O3+3NaOH Volumetric measurements of NO chemisorption Ru3(CO)12/Al2O3 prepared above was suspended were carried out in a conventional Pyrex glass high in water and 0,39mmol of NaOH was added, vacuum adsorption system, A typical procedure After the mixture was stirred for 2h, water was was as follows: Each samples of 250mg was placed removed in vacuo, in a glass reactor, heated at 5℃/min and activated 2,2,5, 3NaOH/Al2O3+Ru3(CO)12 at 300℃ under a flow of 3% H2S/H2 (30ml/min) 0,39mmol of NaOH and 0,46g of Al2O3 were for 3h, After this treatment, the sample was stirred for 2h in methanol, After methanol was evacuated at 300℃ under vacuum(10-3 Torr) for removed in vacuo, 5cc of THE was added, Into 1h and then cooled to 25℃, For RuCl3/Al2O3, the resulted suspension was added 0,13mmol of the sample was sulfided at 400℃ for 3h, evacuated Ru3(CO)12 and the mixture was stirred for 2h, at 400℃ for 1h and then cooled to 25℃, The solvent was removed in vacuo, Adsorption of NO was always carried Out at 25℃ 2,3, Apparatus and Reaction Procedures as follows: For each sample, an adsorption A catalyst precursor was placed in a pressurized isotherm was determined between 30 and 200 Torr, fixed-bed flow reactor(10mm ID×300mm), heated allowing 1h for equilibration of the gas with the at 5℃/min and activated at 300℃ under a flow of sample at each measurement point, Extrapola- H2S in H2 (H2S 3%) for 3h, For the activation of tion of each isotherm to zero pressure provided the the catalyst, H2, N2, H2S (100%), H2S in N2 (H2S measure of the total amount of gas adsorbed, 50%) or H2S in H2 (H2S 50%) was also used instead After a first isotherm, the sample was evacuated of H2S in H2 (H2S 3%), When RuCl3/Al2O3 was under vacuum (10-3 Torr) at 25℃ for 1h, After used, presulfidation with H2S in H2 (H2S 3%) was this treatment, a second isotherm was obtained,
performed at 400℃ for 3h, After the treatment, The difference in the uptakes between the first the reactor was adjusted to 300℃ and was pres- (total adsorption) and the second (reversible surized with hydrogen, Then, the solution con- adsorption) isotherm was assumed to be the taining DBT was supplied with a feed pump amount of the irreversibly chemisorbed NO, (Kyowa Seimitsu KHD-16), HDS of DBT was After NO chemisorption and HDS reaction, XPS carried out under the following conditions: tem- of the sampled catalyst was measured without perature, 300℃; 50kg/cm2; H2 18l/h; WHSV, exposing the catalyst to air, Each sample was 16,5h-1; initial concentration of DBT in xylene, mounted on a sample holder with a commercially 1,0wt%; catalyst, 0,5g; Ru 8wt%, The weight of available conducting tape, The XPS was re- the catalyst includes the weights of metal and corded on a Shimadzu ESCA-850 photoelectron support, Conversion of DBT reached a steady spectrometer using Mg Kα radiation, Before the state within about 3h, Then samples of products XPS measurement, etching, i,e, sputtering by were collected from a gas-liquid separator, four argon ion, was carried out by an ion gun equipped
石 油 学 会 誌 Sekiyu Gakkaishi, Vol, 39, No, 3, 1996 214 with ESCA-850 to obtain a clean surface of significant increase in the catalytic activity was not ruthenium sulfide (conditions: 2kV, 20mA). In observed (runs 7, 8). This suggests that the loca- this procedure, it was regarded that adsorbed tion of sodium close to ruthenium species by the species on the catalysts such as carbon material, presulfidation of Na[HRu3(CO)11] supported on solvent, hydrogen sulfide etc. could be removed. alumina may be intrinsic for high catalytic Binding energies (BE) were referenced to the Ols activity. The addition of NaOH increased the band at 532.0eV. selectivity for BP in every catalyst, independent of the activity. Presence of NaOH seems to poison 3. Results and Discussion the active sites for hydrogenation of an aromatic ring, without affecting those for desulfurization. 3.1. The Effects of the Addition of Alkali Metal Further, the result indicates that the active sites for Salts on the Hydrodesulfurization Reac- hydrogenation of an aromatic ring are different tivities of Alumina-supported Ruthenium from those for hydrodesulfurization. Catalysts The effects of the addition of sodium salts other Initially, the effects of the addition of NaOH to than NaOH were investigated and listed in the alumina-supported ruthenium catalysts were Table 2. Use of sodium iodide decreased the investigated under the following condition: 300℃; catalytic activity and did not affect the selectivity 50kg/cm2; H2 18l/h; WHSV, 16.5h-1; initial con-for BP. The use of sodium hydrogen carbonate, cebtration of DBT, 1.0wt% in xylene; catalyst, sodium acetate and sodium hydrogen sulfite did 0.5g. Alumina-supported rutheniuln catalysts not reveal any remarkable change in the catalytic examined were activefor HDS and products were activity, but slightly increased the selectivity for biphenyl, cyclohexylbenzene and a trace amount BP. While both activity and selectivity increased of hexahydrodibenzothiophene. The resultsare with use of sodium sulfide, the conversion of DBT shown in Table 1. In the absence of NaOH (runs was less than that with NaOH. It is suggested 1-3), the catalytic activities of catalysts derivedthat fromthe catalytic activity in HDS did not in- alumina-supported ruthenium decreased in the crease since these compounds can not react with order Ru3(CO)12>Ru(acac)3>RuCl3. When Ru3(CO)12 to give Na[HRu3(CO)11]. Ru3(CO)12 was reacted with NaOH and then When an alkali metal was changed in the supported on alumina(run 4), the catalytic activityalumina-supported Ru3(CO)12-alkali metal remarkably increasedand the conversion of DBT hydroxide system, as shown in Table 3, the con- was 71%. At the preparation of the catalyst in thisversion of DBT increased in the order Li Table 1 Hydrodesulfurization of Dibenzothiophene Catalyzed by Alumina-supported Ruthenium Catalystsa) a) Reaction temp. 300℃, pressure 50kg/cm2, WHSV 16.5h-1, cat. 0.5g, H2 18l/h, Amount of Ru3(CO)12 0.13mmol; Presulfided by H2S in H2 at 300℃ (H2S 3%). b) acac=acctylacetonate. c) Presulfided by H2S in H2 at 400℃ (H2S 3%). d) Initially RuCl3 was supported on Al2O3 and then NaOH was added at Ru/Na=1. e) Initially Ru3(CO)12 was supported on Al2O3 and then NaOH was added at Ru/Na=1. f) Initially NaOH was supported on Al2O3 and then Ru3(CO)12 was added at Ru/Na=1. 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 215 Table 2 Hydrodesulfurization of Dibenzothiophene Catalyzed by Alumina Supported Ruthenium Carbonyl-Alkali Metal Compound Systemsa) a) Readion temp. 300℃, pressure 50kg/cm2, WHSV 16.5h-1. cat. 0.5g. H2 18l/h; concentration of DBT 1.0wt%. Presulfided by H2S in H2 at 300℃ (H2S 3%). Table 3 Hydrodesulfurization of Dibenzothiophene Catalyzed by Alumina-supported Ruthenium Catbonyl-Alkali Metal Hydioxide Systemsa) a) Readion temp. 300℃, pressure 50kg/cm2, WHSV 16.5h-1, cat. 0.5g, H2 18l/h; concentration of DBT 1.0wt%. Presulfided by H2S in H2 at 300℃ (H2S 3%) for 3h. Ru3(CO)12-3MOH/Al2O3(M=Li, Na, K, Rb or Cs), Conversion of DBT: ○ Cs, △ Na. 300℃; 50kg/cm2; H2 18l/h; WHSV, 16.5h-1; initial Selectivity for BP: ● Cs, ▲ Na. concentration of DBT in xylene, 1.0wt%; catalyst, 0.5g; Ru3(CO)12-nMOH/Al2O3 (M=Na or Cs), 300℃; 50kg/ Ru 8wt%. cm2; H2 18l/h; WHSV, 16.5h-1; initial concentration of DBT in xylene, 1.0wt%; catalyst, 0.5g; Ru 8wt%. Fig. 1 Rate of HDS vs. 1/(Ion radius) Fig. 2 Effect of M/Ru Ratio on the Conversion of DBT and Selectivity for BP Na in every M/Ru value. Further, the former showed that the maximum at M/Ru=2 which was greater than the amount of alkali metal hydroxide concentration of DBT, 1.0wt% in decalin; catalyst, needed to form M[HRu3(CO)11] (M/Ru=1), sug- 0.2g. The results are shown in Fig. 3. Al- gesting that excess of alkali metals were consumed though the conversion of DBT over the ruthenium by alumina. Further addition of alkali metals catalyst was slightly less than that over Co-Mo/ decreased the conversion, probably because such Al2O3, HDS rate of DBT per the supported amount large amount of alkali metal would shield active of transition metal of the former was greater than ruthenium species. that of the latter. To compare the activities between catalysts 3.2. The Effects of the Addition of Cesium Hydrox- derived from Ru3(CO)12-6CsOH/Al2O3 and a com- ide on the Hydrodesulfurization Reactivities mercial Co-Mo/Al2O3, HDS of DBT were per- of Alumina-supported Ruthenium Catalysts formed under the following conditions: 200- When Ru3(CO)12, Ru(acac)3 and RuCl3 were 260℃; 50kg/cm2; H21 8l/h; WHSV, 70h-1; initial treated with CsOH and then supported on 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 216 Conversion of DBT: ○ Ru-Cs/Al, △ Co-Mo/Al. Rate of DBT IIDS: ● Ru-Cs/Al, ▲ Co-Mo/Al. Ru3(CO)12-6CsOH/Al2O3 (Ru, 8wt%); Co-Mo//Al2O3 (Mo, 8wt%, Co/Mo=0.58); 50kg/cm2; H2 18l/h: WHSV, 70h-1; initial concentration of DBT in decalin, 1.0wt%; catalyst, 0.2g. Fig. 3 Effect of Temperature on the Conversion of DBT and the Rate of DBT HDS alumina, catalytic activity and selectivity for BP a) Ru3(CO)12/Al2O3; b) Ru3(CO)12-3CsOH/Al2O3 remarkably increased for all of the catalysts. This c) Ru3(CO)12-6CsOH/Al2O3; d) Ru3(CO)12-9CsOH/ meant that to obtain the high activity and Al2O3. selectivity, it may be important to prepare alkali metal salts of ruthenium compounds at the initial Fig. 4 FTIR Spectra of Ru3(CO)12-nCsOH/Al2O3 stage. Activity for the same amount of cesium increased in the order RuCl3-CsOH/Al2O3< Ru(acac)3-C5OH/Al2O3 Table 4 Hydrodesulfurization of Dibenzothiophene Catalyzed by Ru3(CO)12-nCsOH/Al2O3 Systems and Characterization of the Catalysts by Means of XPS a) Readion temp. 300℃, pressure 50kg/cm2, WHSV 16.5h-1, cat. 0.50g, H2 18l/h; concentration of DBT 1.0wt%. Presulfided by H2S in H2(H2S 3%). b) XPS spectra were measured for samples used in HDS of DBT. Before the measurement, the samples were sputtered by Ar+ ion for 10min. Every binding energy was referenced to Oxygen O 1s 532.0eV. c) Ratio of peak areas between Al 2p, S 2p, and Ru 3p3/2. 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 217 Table 5 Characterization of Alumina-supported Ruthenium Catalysts by Means of NO Chemisorption and XPS a) Amounts of NO chemisorption was measured at 25℃. b) Calculated as 100% at NO/Ru=1mol/mol. In this calculation. the amount of ruthenium is 7.9×102μmol/g-cat. c) XPS spectra were measured for samples used in NO adsorption. Before the measurement, the samples were sputtered by Ar+ ion for 10min. Every binding energy was referenced to Oxygen O 1s 532.0eV. d) Ratio of peak areas between Al 2p, S 2p, and Ru 3 p3/2. After Cs[HRu3(CO)11] was supported on alumina, catalyst, CsOH seems to obstruct the coordinative- however, three peaks at 2000 (s), 2030 (vs) and ly unsaturated sites on the catalyst, at least at the 2062 (s) cm-1 were observed, indicating that presulfidation step. On the contrary, the use of Cs[HRu3(CO)11] had reacted with acid sites on CsOH for the alumina-supported ruthenium alumina to reproduce Ru3(CO)12 on alumina. carbonyl increased the amount of NO chemisorp- The result shows that the location of cesium close tion. It is assumed that the dispersion of ruthenium to ruthenium species is intrinsic to increase the species may increase with an increase in Cs/Ru activity, even when Ru3(CO)12 is reproduced. ratio, because the anionic ruthenium complex may When Ru3(CO)12 was treated with 6 fold of CsOH have interaction with acid sites to be anchored to in methanol and was supported on alumina, alumina at the presulfidation step. As shown in Ru3(CO)12 was not reproduced and anionic species FTIR measurement, the anionic ruthenium car- were maintained on alumina, since peaks with bonyls were maintained on alumina only in wavenumbers lower than those of Ru3(CO)12 were Ru3(CO)12-6CsOH/Al2O3 and Ru3(CO)12-9CsOH/ observed. The result shows that the maintenance Al2O3 systems. In these systems, the dispersion of the anionic species on alumina as well as the exceeded 100%, indicating that there may be location of cesium close to ruthenium species is dinitrosyl species where two molecules of NO are also essential to increase the activity. When adsorbed on one ruthenium atom. Further, it is Ru3(CO)12 was treated with 9 fold of CsOH in also suggested that there may be stable ruthenium methanol and was supported on alumina, anionic sulfide because dinitrosyl species were often species were also maintained as shown in Fig. 4d. observed for metal sulfide20b),23),24). In order to It seems, however, that the trinuclear anionic confirm the presence of ruthenium sulfide, XP [HRu3(CO)11]- can not be maintained on alumina, spectra of the catalysts were measured before and probably because the amount of CsOH added was after HDS. too much to maintain the structure. Although it 3.2.3. XPS Measurement of the Catalysts before is not clear whether or not the trinuclear structure and after HDS Reaction is needed to obtain the high catalytic activity, the XP spectra were measured for the catalysts before addition of excess amount of cesium would shield and after HDS reaction and the results are shown the active ruthenium species and decrease the in Tables 4 and 5, respectively. The catalysts be- activity. fore HDS were the samples used for NO chemi- 3.2.2. NO Chemisorption of the Catalysts sorption. The S 2p and Ru 3p3/2 XP spectra from It can be considered that the amount of NO the alumina-supported ruthenium used for HDS chemisorption is proportional to that of coor- showed peaks in the ranges 160.5-162.8eV and dinatively unsaturated sites on a catalyst. The 461.3-462.2eV, respectively. These results sug- amount of NO chemisorption was measured gest that ruthenium species for every catalyst are because the amount of coordinatively unsaturated between ruthenium metal (461.0eV) and RuS2 sites on a catalyst often relates to the catalytic (462.7eV). The binding energies of Ru 3p3/2 for activity. No irreversible chemisorption of NO the Ru3(CO)12-6CsOH/Al2O3 system before and was observed on CsOH/Al2O3. As shown in after HDS were highest among examined catalysts, Table 5, the addition of CsOH to RuCl3/Al2O3 while those for some catalysts were not affected by and Ru(acac)3/Al2O3 did not increase the amount the addition of alkali metal. This shows that of NO chemisorption. Especially, in the former ruthenium species for the Ru3(CO)12-6CsOH/ 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 218 Al2O3 system may be close to RuS2, rather than ruthenium metal. Further, the binding energies of S 2p decreased with alkali metal for both catalysts before and after HDS, indicating that the sulfur atom in the catalysts with alkali metal would have higher electron density than that without alkali metal. The values of Ru 3p/Al and S/Ru 3p were obtained from the peak areas of XP spectra. Although the values of Ru 3p/Al for alumina-supported RuCl3 and Ru(acac)3 catalysts were higher than those for alumina-supported Ru3(CO)12, the catalytic activities for the former catalysts were lower than those for the latter, indicating that the dispersion of the former Fig. 5 Plots of S, Ru Ratio in XPS vs. Conversion of ruthenium species were not as high as that of the DBT latter while the bulk of the ruthenium species for the former catalysts existed with higher con- centration. Most important phenomenon was can be suggested that in this catalyst system, not observed with the S/Ru 3p ratio values. When only ruthenium species are sulfurized completely, cesium existed in the catalysts, the values of S/Ru but also a significant amount of sulfur formed by 3p remarkably increased, as shown in Table 4, for the HDS reaction may be accommodated on the the catalysts after HDS, indicating that the catalyst and coat ruthenium atoms, because HDS presence of cesium could stabilize ruthenium of DBT is much more rapid than the formation of sulfide to accommodate sulfur on the catalyst hydrogen sulfide by the reaction of surface sulfur surface. These values of S/Ru 3p were plotted with hydrogen. The coating of the ruthenium against the conversions of DBT shown in Fig. 5. atoms by large amounts of sulfur may result in Figure 5 shows the tendency of the conversion of higher value of S/Ru 3p and lower value of Ru 3p/ DBT increasing with increase in the S/Ru 3p ratio. Al. The further addition of cesium decreased S/ The result suggests that the catalytic activity Ru 3p ratio, however, indicating that excess of increases when ruthenium sulfide is stabilized in CsOH would prevent the formation of ruthenium the presence of cesium. Further, it seems that the sulfide by shielding the coordinatively unsaturated presence of alkali metal strengthen the bond of sites on ruthenium species. Although the for- ruthenium and sulfur to stabilize ruthenium mation of cesium sulfide can be also considered, sulfide, where the carbon-sulfur bond scission the amount of sulfur accommodated on a catalyst may proceed more easily than ruthenium species as cesium sulfide may not be significant, since the sulfided less and close to low valent ruthenium value of S/Ru 3p at Cs/Ru=3 was lower than that metal. at Cs/Ru=2. It has been reported that when alumina- 3.3. Effects of the Conditions of Activation on supported ruthenium chloride was presulfided by Hydrodesulfurization Using Catalyst Derived H2S/H2. H2S and H2S/N2, the treated catalysts from Ru3(CO)12-6CsOH/Al2O3 revealed 1.8, 3.6 and 4.2 of S/Ru in XPS measure- It has been reported that method to activate the ment, respectively7). The latter two catalysts were catalyst precursor largely affects HDS activity7). sulfurized completely and showed catalytic activity The authors investigated the effects of the con- in HDS of thiophene higher than the former one, ditions of activation on the activity by using which was not sulfurized completely. In this Ru3(CO)12-6CsOH/Al2O3 and measured XPS spec- case, the value of S/Ru in XPS was also much tra of the catalysts used for HDS. The results are greater than the stoichiometric value of ruthenium shown in Table 6. When the Ru3(CO)12-6CsOH/ disulfide, 2. In the present study, when alumina- Al2O3 system was activated with H2S in H2 (H2S supported ruthenium chloride was presulfided by 50%), the conversion of DBT was 98%, similar to H25/H2, the treated catalyst revealed 2.31 of S/Ru that in Run 24, where H2S in H2 (H2S 3%) was used. in XPS measurement, as shown in Table 5. It seems that the concentration of H2S does not Further, in cesium promoted Ru3(CO)12/Al2O3 affect the activity. When H2S in N2 (H2S 50%) and systems, both catalysts, before and after HDS, H2S 100% were used instead of H2S in H2, the showed the maximum value of S/Ru 3p at Cs/ conversions of DBT slightly decreased to 89 and Ru=2, which was also much larger than the 82%, respectively, compared with that in Run 24. stoichiometric value of ruthenium disulfide, 2. It When N2 and H2 were used, the conversions de- 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 219 Table 6 Hydrodesulfurization of Dibenzothiophene Catalyzed by Ru3(CO)12-6CsOH/Al2O3 Systems and Characterization of the Catalysts by Means of XPS a) Reaction temp. 300℃, pressure 50kg/cm2, WHSV 16.5h-1, cat. 0.50g, H2 18l/h: concentration of DBT 1.0wt%. b) Presulfided by H2S in H2 (H2S 50%). c) Presulfided by H2S in N2(H2S 50%). ob Treated with H2S(100%) stream. e) Treated with 112 stream. f) Treated with N2 stream. g) XPS spectra were measured for samples used in HDS of DRT. Before the measurement, the samples were sputtered by Ar+ ion for 10min. Every binding energy was referenced to Oxygen O 1s 532.0eV. h) Ratio of peak areas between Al 2p, S 2p, and Ru 3p3/2. creased remarkably. In XPS measurement of these catalysts, S/Ru 3p ratios also decreased in comparison with that in Run 24. It is likely that the catalyst precursor can not be sulfurized in the absence of H2S to release carbon monoxide ligands. In contrast, in the presence of H2S, it is suggested that anionic ruthenium carbonyls such as [HRu3(CO)11]- etc. in Ru3(CO)12-6CsOH/Al2O3 would react with H2S to release carbon monoxide ligands easily and form the ruthenium-sulfur bonds at the preparation of the catalyst. In this process, H2S adsorbed on ruthenium would oxi- dize Ru(0) species to the oxidation state close to Ru(IV) for RuS2 with the release of hydrogen molecule. In the presence of alkali metals, the ruthenium-sulfur bonds formed may become Scheme 1 Mechanism of Hydrodesulfurization Cata- lyzed by Alumina-supported Ruthenium- stable to keep active ruthenium sulfide even under Alkali Metal Systems hydrogen pressure. 4. Concluding Remarks stabilization of ruthenium sulfide. In alumina-supported ruthenium catalysts, the Although HDS of thiophenes using ruthenium HDS activity was often rather low4)-7), in com- sulfide catalysts were reported, the effects of parison with that of commercial catalysts, probab- addition of alkali metals in those catalysts on the ly because sulfidation of ruthenium species is HDS reactions were not well-known. Gobolos et incomplete and RuS2 on alumina is unstable in al. compared the activities in HDS of thiophene hydrogen atmosphere. It has also been reported catalyzed by ruthenium catalysts supported on that the catalyst derived from supported Ru3(CO)12 NaY, KY, HY and Na2S-doped KY zeolites10). showed the lower activity for HDS of thiophene in The activity decreased in the order Na2S-doped atmospheric pressure of hydrogen than that KY>KY>NaY>HY and the Na2S-doped KY show- derived from supported RuCl34),6),7). In contrast, ed activity three times higher than that of KY. the authors reported that in pressurized flow The order of the activity was explained by the system, the catalysts derived from alumina- strength of Bronsted acids. They concluded that supported ruthenium carbonyls showed activity in the addition of Na2S neutralized the Bronsted HDS of DBT higher than those from alumina- acidity of zeolite to increase the activity, as a result. supported RuCl3 and Ru(acac)320). Alumina- The effects of kind and amount of alkali metal, supported ruthenium carbonyls gave the active however, were not examined, and the activity was species, which shows the high activity for HDS rather low in comparison with a commercial one7) under high pressure, more easily, at the presul- because the amount of ruthenium loaded on a fidation step, than alumina-supported RuCl320) support was too low, 2wt%. Further, there was In the present paper, however, it has been clarified no reference to the effect of alkali metal on the that the modification of Ru3(CO)12 with alkali 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 220 metal hydroxides improved the activity and b) Phillips, J., Dumesic, J. A., Appl. Catal., 9, 1 (1984). c) selectivity of the catalyst obtained. Ruthenium Howe, R. F., ed. by Iwasawa, Y., "Tailored Metal species on the catalyst, in the presence of alkali Catalysts," Reidel, Dordrecht (1986), p. 141. d) Ichikawa, M., ed. by Iwasawa, Y., "Tailored Metal Catalysts," metal, existed in the oxidation state close to RuS2 Reidel, Dordrecht (1986), p. 183. rather than ruthenium metal. The mechanism of 13) a) Ishihara, A., Mitsudo, T., Watanabe, Y., Sekiyu reaction is illustrated in Scheme I. It is suggested Gakkaishi, 33, (1), 28 (1990) and literature cited therein. that RuS2 which could be stabilized on alumina b) Ishihara, A., Mitsudo, T., Morita, N., Watanabe, Y., with alkali metal, even in pressurized hydrogen, Sekiyu Gakkaishi, 33, (5), 327 (1990). c) Mitsudo, T., Ishihara, A., Watanabe, Y., Ind. Eng. Chem. Res., 29, 163 would reveal activity comparable to that of (1990). Co-Mo/Al2O3. 14) a) Banks, R. L., Bailey, G. C., Ind. Eng. Chem., Prod. Res. Dev., 3, 170 (1964). b) Banks, R. L., Chemtech, 112(1986). 15) a) Maezawa, A., Kitamura, M., Wakamoto, K., Okamoto, Y., Imanaka, T., Chem., Express, 3, 1 (1988). b) Okamoto, References Y., Maezawa, A., Kane, H., Imanaka, T., J. Mol. Catal., 52, 337 (1989). 1) Pecoraro, T. A., Chianelli, R. R., J. Catal., 67, 430 (1981). 16) Vrinat, M. L., Gachet, C. G., de Mourgues, L., ed. by 2) Lacroix, M., Boutarfa, N., Guillard, C., Vrinat, M., Imelik, B., "Catalysis by Zeolite," Elsevier, Amsterdam Breysse, M., J. Catal., 120, 473 (1989). (1980), p. 219. 3) Vrinat, M., Lacroix, M., Breysse. M., Mosoni, L., Roubin, 17) a) Ishihara, A., Azuma, M., Matsushita, M., Kabe, T., M., Catal. Lett., 3, 405 (1989). Sekiyu Gakkaishi, 36, (5), 360 (1993). b) Ishihara, A., 4) Harvey, T. G., Matheson, T. W., J. Catal., 101, 253 (1986). Nomura, M., Matsushita, M., Shirouchi, K., Kabe, T., 5) Mitchell, P. C. H., Scott, C. E., Bonnelle, J. P., Grimblot, "New Aspects of Spillover Effect in Catalysis," eds. by J. G., J. Catal., 107, 482 (1987). Inui T. et al., Elsevier Science B. V., (1993), p. 357. 6) Kuo, Y., Cocco, R. A., Tatarchuk, B. J., J. Catal., 112, 250 18) a) Ishihara, A., Shirouchi, K., Kabe, T., Chem. Lett., 589 (1988). (1993). b) Ishihara, A., Shirouchi, K., Kabe, T., Sekiyu 7) De Los Reyes, J. A., Gobolos, S., Vrinat, M., Breysse, M., Gakkaishi, 37, (4), 411 (1994). Catal. Lett., 5, 17 (1990). 19) Ishihara, A., Matsushita, M., Shirouchi, K., Zhang, Q., 8) Chary, K. V. R., Khajamasthan, S., Vijayakumar, V., J. Kabe, T., Sekiyu Gakkaishi, 39, (1), 26 (1996). Chem. Soc., Chem. Commun., 1339 (1989). 20) a) Ishihara, A., Nomura, M., Kabe, T., J. Catal., 150, 212 9) Liaw, S.-J., Raje, A., Lin, R., Davis, B. H., ACS Prep. Div. (1994). b) Ishihara, A., Nomura, M., Kabe, T., Sekiyu Petrol. Chem., 636 (1994). Gakkaishi, 37, (3), 300 (1994). 10) Gobolos, S., Breysse, M., Cattenot, T., Decamp, M., 21) Ishihara, A., Nomura, M., Kabe, T., Chem. Lett., 2285 Lacroix, M., Portefaix, J. L., Vrinat, M., eds. by Occelli, (1992). M. L., Anthony, R. G., "Advances in Hydrotreating 22) Johnson, B. F. G., Lewis, J., Raithby, P. R., Suess, G., J. Catalysts," Elsevier Science Publishers B. V., Amsterdam Chem. Soc., Dalton Trans., 1356 (1979). (1989), p. 243. 23) Lopez Agudo, A., Gil Llambias, F. J., Tascon, J. M. D., 11) Bellaloui, A., Mosoni, L., Roubin, M., Vrinat, M., Fierro, J. L. G., Bull. Soc. Chim. Belg., 93, 719 (1984). Lacroix, M., Breysse, M., C. R. Acad. Sci. Paris, 304, 1163 24) Topsoe, N., Topsoe, H., J. Catal., 84, 386 (1983). (1987). 12) a) Bailey, D. C., Langer, S. H., Chem. Rev., 81, 109 (1981). 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996 221 要 旨 担持金属 カル ボニル錯体 を用い たジベ ンゾチ オフェンの水素化脱硫反応 (第5報) アル ミナ担持 ル テニウムカルボ ニル-ア ルカ リ金属 水酸化 物系よ り調製 した水素化脱硫触媒 石原 篤, 野村 正敏, 高浜 伸昭, 浜口 浩一, 加部 利明 東 京 農 工 大 学 工 学 部 応 用 化 学 科, 184東 京 都 小 金 井 市 中 町2-24-16 硫 化 し た ア ル ミ ナ 担 持 ル テ ニ ウ ム 触 媒 を 用 い た ジ ベ ン ゾ チ オ ボ ニ ル系 触 媒 に お い て, ア ル カ リ金 属 水 酸 化 物 の添 加 量 を増 加 フ ェ ン (DBT) の 水 素 化 脱 硫 反 応 に お い て, ア ル カ リ 金 属 水 させ た 時, DBTの 転 化 率 は 向 上 し, M/Ru=2 (M=Naあ るい 酸 化 物 の 触 媒 活 性 お よ び 生 成 物 選 択 性 に 及 ぼ す 影 響 を 検 討 し はCs) の 時 最 大 値 を示 した。 さ ら に, ア ル カ リ金 属 を添 加 す た。 ア ル ミ ナ 担 持 ル テ ニ ウ ム カ ル ボ ニ ル か ら得 ら れ る 触 媒 へ 水 る と活 性 は低 下 した。Ru3(CO)12-nCsOH/Al2O3系 触 媒 にお い 酸 化 ナ ト リ ウ ム を 加 え る と, DBTの 転 化 率 は41%か ら71% て, ビフ ェ ニ ル が選 択 的 に生 成 した。 こ れ らの現 象 を説 明 す る に 著 し く 向 上 し た。 こ の 触 媒 系 で は, ル テ ニ ウ ム カ ル ボ ニ ル が た め に, NOの 化 学 吸 着 お よ びX線 光 電 子 (XP) スペ ク トル 予 め 水 酸 化 ナ ト リ ウ ム と 反 応 し, ル テ ニ ウ ム の ヒ ド リ ド錯 体 を 脱硫 反 応 前 と後 の 触 媒 につ い て測 定 した。Ru3(CO)12/Al2O3 Na[HRu3(CO)11] が 生 成 し た 後, ア ル ミ ナ 上 に 担 持 す る こ と へ の セ シ ウ ム の 添 加 はNOの 化 学 吸 着 量 を 増 加 させ た。 この が 高 活 性 を 得 る た め に 重 要 で あ る こ と が 分 か っ た。RuCl3, こ とは, 触 媒 に は硫 化 後 もま だ 多 くの配 位 不 飽 和 サ イ トが あ る Ru(acac)3 (acac=ア セ チ ル ア セ ト ナ ー ト) お よ びRu3(CO)12 こ と を示 した。XPス ペ ク トル よ り, 適 当 な 量 の セ シ ウ ム を加 を 水 酸 化 セ シ ウ ム と 反 応 さ せ ア ル ミナ に 担 持 さ せ た 時, 活 性 は え る と水 素加 圧 下 で さえ ア ル ミナ上 に硫 化 ル テ ニ ウ ムが 安 定 に RuCl3-CsOH/Al2O3 3CsOH/Al2O3の 順 に 増 加 し た。 ア ル ミ ナ 担 持 ル テ ニ ウ ム カ ル れ る触 媒 は, Co-Mo/Al2O3に 匹敵 す る触 媒 活 性 を示 した。 Keywords Hydrodesulfurization, Dibenzothiophene, Ruthenium carbonyl, Alkali metal hydroxide, Catalyst preparation, Pressurized flow system 石 油 学 会 誌 Sekiyu Gakkaishi, Vol. 39, No. 3, 1996