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Effects of preparation methods of support on the properties of nickel catalyst for hydrogenation of m-dinitrobenzene |
| LIU Yingxin1, WEI Zuojun2, CHEN Jixiang3, ZHANG Jiyan3 |
| 1.Department of Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, Zhejiang University of Technology, Hangzhou 310032, China; 2.Institute of Pharmaceutical Engineering, College of Materials Science and Chemical Engineering, Zhejiang University, Hangzhou 310027, China; 3.Department of Catalysis Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; |
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Abstract Using tetraethyl orthosilicate (TEOS) as the precursor of silica, the silica aerogel and xerogel, which were used as supports of nickel-based catalysts for liquid hydrogenation of m-dinitrobenzene to m-phenylenediamine, were prepared by the sol-gel method combined with supercritical drying (SCD) and conventional drying, respectively. Then, a series of nickel-based catalyst samples supported on these supports were prepared by the incipient wetness impregnation method with an aqueous solution of nickel nitrate as well as lanthanum nitrate as impregnation liquids. Based on the characterization results of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature-programmed desorption of hydrogen (H2-TPD), and catalytic activity evaluation, the physico-chemical properties and catalytic performances of the catalysts were investigated. The results show that the nickel crystallites on the binary nickel catalyst using silica aerogel as support are of smaller particle size. However, compared with the sample supported on silica xerogel, the nickel catalyst supported on the silica aerogel exhibits lower activity and selectivity for the hydrogenation of m-dinitrobenzene because it has a lesser amount of active sites and weaker absorption ability to reactants caused by sintering of the nickel crystallites. The addition of promoter La2O3 could increase the activity and selectivity of the catalysts. Among all the nickel-based catalyst samples prepared, the La2O3 promoted ternary nickel-based catalyst supported on silica xerogel exhibits the highest activity and selectivity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine, which could be attributed to its highest active surface area and appropriate absorption strength to reactants. Over this promising catalyst, the conversion of m-dinitrobenzene and the yield of m-phenylenediamine could reach 97.0% and 93.1%, respectively, under proper reaction conditions of hydrogen pressure 2.6 MPa, temperature 373 K, and reaction time 1 h.
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Issue Date: 05 September 2007
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