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Hydrotalcite-Impregnated Copper and Chromium

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Hydrotalcite-Impregnated Copper and Chromium Brazilian Journal ISSN 0104-6632 of Chemical Printed in Brazil www.scielo.br/bjce Engineering Vol. 35, No. 02, pp. 669 - 678, April - June, 2018 dx.doi.org/10.1590/0104-6632.20180352s20160703 HYDROTALCITE-IMPREGNATED COPPER AND CHROMIUM-DOPED COPPER AS NOVEL AND EFFICIENT CATALYSTS FOR VAPOR-PHASE HYDROGENATION OF FURFURAL: EFFECT OF CLAY PRETREATMENT Mohammad Ghashghaee1,2*, Samira Shirvani1,2, Vahid Farzaneh1,2 and Samahe Sadjadi2,3 1 Faculty of Petrochemicals, Iran Polymer and Petrochemical Institute, P.O. Box 14975-112, Tehran, Iran 2 Biomass Conversion Science and Technology (BCST) Division, Iran Polymer and Petrochemical Institute, P.O. Box 14975-115, Tehran, Iran 3 Gas Conversion Department, Faculty of Petrochemicals, Iran Polymer and Petrochemical Institute, P.O. Box 14975-112, Tehran, Iran (Submitted: December 18, 2016; Revised: March 20, 2017; Accepted: March 24, 2017) Abstract - A series of novel catalysts based on immobilization of copper and chromium-doped copper on calcined and uncalcined hydrotalcite support have been developed and used for promoting vapor-phase hydrogenation of furfural. The results indicated that a pre-calcination of the support has a negative role in changing the structural features and catalytic activity of the final catalysts. Moreover, the presence of the Cr promoter can improve the catalyst performance. The best performance (furfuryl alcohol selectivity of 94% and furfural conversion of 89%) was obtained over the Cr-doped copper catalyst supported on as-synthesized hydrotalcite material. Keywords: Hydrotalcite, Furfuryl alcohol, Hydrogenation, Copper catalysts, Biomonomers. INTRODUCTION numerous chemicals and fuels, including furfurylamine, maleic acid, linear alkanes, furoic acid, 2-methyl Furfural (FF) is an important biomass-derived tetrahydrofuran, 2-methylfuran, furan, cyclopentanone, starting material and chemical building block tetrahydrofurfuryl alcohol, 1,5-pentanediol, and (Taylor et al., 2016; Li et al., 2016c) which can be furfuryl alcohol (Yan et al., 2013; Zhu et al., 2014; easily obtained through fast pyrolysis of biomass or Yuan et al., 2015; Yan and Chen, 2014; Sulmonetti et dehydration of xylose (Sulmonetti et al., 2016). The al., 2016; Halilu et al., 2016; Vargas-Hernández et al., increasing attention to this important platform stems 2014; Jiménez-Gómez et al., 2016; Manikandan et al., unequivocally from its potential (Marcotullio, 2011, 2016a; Yan et al., 2014). Among various conversions, 2013; De Jong and Marcotullio, 2010) to convert it to catalytic hydrogenation of FF to furfuryl alcohol (FFA) * Corresponding author. Tel.: +98 21 48662481; fax: +98 21 44787032. E-mail address: [email protected] 670 Mohammad Ghashghaee, Samira Shirvani, Vahid Farzaneh and Samahe Sadjadi has earned a noticeable interest because of its utility the above-mentioned process was not reported in the for synthesis of value-added products such as farm literature. chemicals, adhesives, furan fiber-reinforced plastics, Taking into account the outstanding properties of foundry resins, thermostatic resins, liquid resins, hydrotalcite support and the importance of conversion lubricants, dispersing agents, ascorbic acid and lysine of FF, in this paper we wish to report the utility of (Xu et al., 2015; Nagaraja et al., 2007; Yuan et al., 2015; hydrotalcite for supporting copper and chromium- Taylor et al., 2016). doped copper species for developing novel catalysts Catalytic conversion of FF to FFA can be achieved for promoting catalytic hydrogenation of FF to FFA. either in the gas phase (Nagaraja et al., 2007; Li et al., Moreover, for the first time we study the effect of the 2015; Yan and Chen, 2013; Jiménez-Gómez et al., 2016) pretreatment (pre-calcination) of hydrotalcite on the or the liquid phase (Yuan et al., 2015; Sharma et al., catalytic activity of the final catalyst to highlight the 2013; Villaverde et al., 2015; Li et al., 2016b; O'Driscoll importance of the hydrotalcite pretreatment on its et al., 2016; Li et al., 2016a). However, the gas-phase performance as a support. process is favored as it can be run under milder reaction conditions (Vargas-Hernández et al., 2014). In industry, EXPERIMENTAL the gas-phase hydrogenation is carried out at pressures up to 30 bar and temperatures ranging between 130 and 200 ºC under copper chromite catalysis (Kijeński Materials et al., 2002). Although the catalytic activity of copper The chemicals used for the synthesis of catalysts chromite is acceptable, its moderate selectivity still included Mg(NO ) .6H O (ACS reagent, 99%), remains a challenge. In this regard, many attempts have 3 2 2 Cu(NO3)2.3H2O (99.5%), Na2CO3 (99.9%), NaOH been devoted to developing alternative catalysts such as (ACS reagent, 98%), Al(NO ) .6H O (99%) and Cu, Ni, Pd, Co, Ru, Ir, and Pt catalysts supported on 3 3 2 Cr(NO3)3.9H2O (97%). All were provided from Merck a relatively inert material such as silica and alumina except the latter that was purchased from Scharlau. (Halilu et al., 2016; Nagaraja et al., 2011; Nakagawa et The starting materials were used as received without al., 2014; Lesiak et al., 2014; An et al., 2013; Aldosari any further purification. The materials employed in the et al., 2016). Among these catalysts, Cu-MgO has been catalytic runs included FF (98.90%, Merck) and high subjected to many studies because of its low cost, high purity hydrogen (99.99%) and nitrogen (99.99%). activity and selectivity to FFA (Vargas-Hernández et al., 2014; Nagaraja et al., 2007; Nagaraja et al., 2003; Cui Catalyst preparation et al., 2015; Estrup, 2015; Liu et al., 2015; Nagaraja et al., 2011; Sadjadi et al., 2017; Ghashghaee et al., 2017; Preparation of support Shirvani et al., 2017; Farzaneh et al., 2017). Layered double hydroxides (LDHs), also referred to A conventional co-precipitation method was used as hydrotalcite-like compounds (Xu et al., 2011), are a for the synthesis of hydrotalcite (abbreviated as HT) 2+ 3+ class of clays with the general formula of [M 1-x M x (Li et al., 2006). Briefly, to a stirred mixture of 1 mol of (OH) ][A n-] ·mH O, in which M2+ and M3+ are divalent 2 x/n 2 Mg(NO3)2.6H2O and 0.5 mol of Al(NO3)3.9H2O (with and trivalent metal cations, and A n- is a counter anion an Mg/Al molar ratio of 2) in 700 mL of deionized (Liu et al., 2016). Although LDHs have been widely water a solution of 3.5 mol of NaOH and 0.943 mol used in catalysis (Thirumalaiswamy et al., 2015; Basini of Na2CO3 was added dropwise to adjust the final pH et al., 2002; Wei et al., 2010; Baskaran et al., 2015; to 13. Subsequently, the mixture was heated at 65 ºC Thangaraj et al., 2016; Wang et al., 2017; Karthikeyan for 18 h. The resulting precipitate obtained by vacuum and Karuppuchamy, 2017; Hernández et al., 2017; filtration was washed thoroughly with deionized D'Oca et al., 2017; Eskandari et al., 2017; Santos et al., water to reach a neutral pH and then dried overnight 2017), there are only a few reports on their utility as at 130 ºC. Half of the solid was further used without the catalyst support for the gas-phase hydroconversion calcination and the remaining part was calcined at 550 of FF to FFA (Manikandan et al., 2016b; Sangeetha ºC for 5 h to obtain the final oxide catalyst. et al., 2009); in none of them copper and chromium- doped copper species were supported (impregnated) Supporting the catalytic species on Mg-Al hydrotalcite. To the best of our knowledge, the effect of a pre-calcination of the hydrotalcite Wet impregnation was used for supporting the support on the catalytic activity of copper catalysts for copper and copper chromite species on the prepared Brazilian Journal of Chemical Engineering Hydrotalcite-Impregnated Copper and Chromium-Doped Copper as Novel and Efficient Catalysts forVapor-Phase Hydrogenation of Furfural: 671 Effect of Clay Pretreatment supports. In a typical procedure, the HT support was bed was cooled down to the reaction temperature in suspended in deionized water and stirred vigorously. pure hydrogen. Afterwards, FF was injected into the Subsequently, a solution of Cu(NO3)2.3H2O 11% (wt/ reactor using a motorized syringe pump. The reaction wt) in deionized water was added dropwise to the was carried out at the temperature of 180 ºC and -1 aforementioned suspension. The obtained mixture was WHSV of 1.7 h with a hydrogen-to-feed (H2/HC) then impregnated for 24 h at ambient temperature. volumetric ratio of 10. The hydrogenation process was Upon completion of the process, the catalyst was dried followed by collecting the liquid products in an ice trap in an oven at 150 ºC for 12 h and afterward calcined and analyzing on a gas chromatograph (GC) equipped at 550 ºC for 5 h. The obtained catalysts were denoted with a capillary column and a flame ionization detector as CHT1 and CHT3 for the calcined and uncalcined (FID). The carbon balance was higher than 95% in all supports, respectively. The hydrotalcite-supported experiments unless otherwise stated. The outlet molar chromium-copper catalysts were prepared via the flow rates were accordingly normalized assuming a same procedure except that Cr(NO3)3.9H2O 5.5% (wt/ closed carbon balance for the interpretations. Finally, wt) was added together with the copper precursor the performance of the catalyst was estimated using during the impregnation. These two catalysts were the following definitions: named CHT2 and CHT4 as the counterparts of CHT1 and CHT3, respectively. moles of FF consumed Con version % = x100 (1) Characterization of the catalysts Q V moles of FF fed The analytical methods employed for the moles of desired product Sele ctivity mol% = x100 (2) characterization of the synthesized catalysts included Q V moles of FF consumed SEM, EDX, BET, XRD, and TGA.
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