镍盐前驱体对Ni/C催化剂乙醇气相羰化活性的影响

采用等体积浸渍法制备了分别以乙酰丙酮镍、氯化镍、硝酸镍和醋酸镍为前驱体负载在活性炭上的四种催化剂。用BET、金属分散度、H2-TPR、CO-TPD和XRD等方法研究了四种催化剂的结构特点和乙醇气相羰化活性。结果表明，以醋酸镍制备的Ni/C催化剂的羰化活性最高，乙醇转化率和丙酸选择性分别为96.1%和95.7%，而以乙酰丙酮镍制备的Ni/C催化剂的羰化活性最低，乙醇转化率和丙酸选择性分别为68.9%和27.1%。这种活性的差异与镍盐前驱体和活性炭之间的相互作用强弱有着密切关系。醋酸镍组分与活性炭之间的相互作用较强，浸渍组分易在活性炭表面充分吸附，活性中心Ni0在240－340 ℃温度范围内对CO吸附量最大，还原后金属镍的分散度较好且晶粒较小。

Influences of different nickel salt precursors on the catalytic performance of the Ni/C catalysts for vapor-phase carbonylation of ethanol

Different nickel salt precursors, namely, nickel acetylacetone, nickel chlorate, nickel nitrate and nickel acetate, were used to prepare Ni/C catalysts for vapor phase carbonylation of ethanol. The activity testing results revealed that the Ni/C catalyst prepared from nickel acetate showed maximal catalytic activity for carbonylation of ethanol with the ethanol conversion of 96.1% and the propionic acid selectivity of 95.7% in comparison with that prepared with other nickel precursors, but the catalyst prepared from acetylacetone nickel showed minimum activity with the ethanol conversion of 68.9% and the propionic acid selectivity of 27.1%. The Ni/C catalysts were characterized by means of BET measurement, metal dispersion test, H2-TPR and XRD. It was found that the catalytic performances of the Ni/C catalysts depended in a great degree on the interaction between nickel species and active carbon support. The nickel acetate molecule was confirmed to be easily adsorbed on the surface of active carbon, leading to a stronger interaction between nickel species and active carbon support, thereby increasing the absorption capacity of CO. Meanwhile, a better dispersion of active component and smaller nickel crystallites were found.