改善Rh基催化剂上CO加氢生成C_2含氧化物性能的本质及途径

Approaches and Nature of Improving Rh-Based Catalyst Performance for CO Hydrogenation to C_2-Oxygenates

从CO加氢反应的热力学出发,分析了C2含氧化合物生成反应的途径和机理,阐述了改善Rh基催化剂上生成C2含氧化合物性能的本质以及实现的途径.结果显示,相对于CO加氢生成烃类的反应,乙醇、乙醛和乙酸等C2含氧化合物的生成在热力学上是极为不利的;最重要、最有效的提高C2含氧化合物生成活性的手段是开发具有高选择性的催化剂.通过对浸渍方法和还原条件的选择,适当地抑制了Rh-Mn-Li-Fe/SiO2催化剂加氢活性,最终改善了催化剂的加氢性能,使得甲烷选择性降至6·3%,而生成C2含氧化合物的选择性达到91·6%,且保持有较高的时空收率.

Thermodynamic analysis results revealed that the formation of C2-oxygenates from syngas is much more unfavorable than the formation of hydrocarbons. Therefore, the crucial and effective method to promote the C2-oxygenate synthesis is to develop high selective catalysts. According to the mechanism of C2-oxygenate formation, the natures and the approaches to improve the catalytic performance of the Rh-based catalyst for CO hydrogenation to C2-oxygenates were the improvement and the balance in CO dissociation and insertion activity, the proper hydrogenation activity, and the optimal Rh size on the catalyst surface. The impregnation and reduction conditions were optimized to suppress correctly the catalytic activity of the Rh-Mn-Li-Fe/SiO2 catalyst for CO hydrogenation. Consequently, CO insertion competed favorably with hydrogenation, resulting in a maxirnum selectivity （91.6 % in mass fraction） for C2-oxygenates with a high yield and a much low methane selectivity （6.3% in mass fraction）.