浸渍溶剂对Rh-Mn-Li/SiO_2催化剂CO加氢性能的影响

采用CO加氢反应、CO-TPD、TPSR和XPS等技术,考察了水、甲醇、乙醇和异丙醇等浸渍溶剂对Rh-Mn-Li/S iO2催化剂CO加氢性能的影响。结果表明,以乙醇为浸渍溶剂的催化剂表现出最高的C2含氧化合物时空收率(YC2-oxy)和C2含氧化合物选择性(SC2-oxy),分别达686.1 g/(kg-cat.h)和73.8%;以甲醇和异丙醇为浸渍溶剂的催化剂上YC2-oxy也较高,但是SC2-oxy都比前者低;水溶液浸渍制备的催化剂有着较高的SC2-oxy,但是其YC2-oxy较低。以醇类为浸渍溶剂的催化剂的高活性与金属活性组分在催化剂表面富集而导致的更多活性中心的形成有关。催化剂表面非解离的CO比率增加有利于C2含氧化合物选择性的提高。

Effect of Impregnation Solvents on CO Hydrogenation over Rh-Mn-Li/SiO2 Catalysts

Effect of impregnation solvents on the catalytic properties of Rh-Mn-Li/SiO2 catalyst was investigated by means of the following techniques: CO hydrogenation reaction,temperature-programmed desorption of absorbed CO(CO-TPD),temperature-programmed surface reaction(TPSR) and X-ray photoelectron spectroscopy(XPS).The results showed that the choice of impregnation solvents had a striking influence on the activity and selectivity of Rh-Mn-Li/SiO2 catalyst.The catalyst prepared with ethanol as solvent displayed 686.1 g/(kg·h) of space time yield(STY) of C2-oxygenates and 73.8% of selectivity towards C2-oxygenates.The catalysts prepared with methanol or i-propanol as solvent displayed higher STY of C2-oxygenates,but selectivities towards C2-oxygenates were lower.Also,the catalyst prepared with deionized water as solvent exhibited higher selectivity towards C2-oxygenates,but lower STY of C2 oxygenates.It was proposed that the enrichment of Rh,Mn et al.and the formation of more active sites on the catalyst surface prepared using lower-carbon alcohols as impregnation solvents are responsible for the higher STY of C2-oxygenates.In addition,the selectivities towards C2-oxygenates were well correlated with the proportion of absorbed non-dissociatively CO.The catalyst prepared with deionized water or ethanol as solvent had higher proportion of absorbed non-dissociatively CO and thus displayed higher selectivity towards C2-oxygenates.