Acetylene hydrogenation over Ni-Cu nanoparticles supported on silica prepared by aqueous hydrazine reduction.

Non conventional nickel (1%) and nickel (1%)-copper (0.2-0.75%) catalysts supported on silica, prepared by aqueous hydrazine reduction of nickel acetate at 70 degrees C, were studied in acetylene hydrogenation, mainly at 60 degrees C. The obtained results show that the metal dispersion decreases whereas the conversion passes through a maximum with increasing copper content. The reaction produces ethylene, benzene, ethane, n-butane, small amounts of higher hydrocarbons and a paraffinic product. Ethylene and benzene are rather low temperature products (below 80 degrees C) whereas the saturated hydrocarbons, mainly ethane, are rather formed at higher temperature. The presence of water in the feed gas changed the catalyst performances. The carbonaceous deposit during acetylene hydrogenation was studied by means of temperature programmed surface reaction (TPSR). Analysis of the results obtained showed that the changes observed in conversion/selectivity may be correlated with changes in Ni-Cu interactions, chemisorption equilibria or/and coke deposit. A comparative study of classical/non classical Ni/SiO2 catalysts is reported.