制备方法和条件对Rh-Mn-Li-Ti/SiO_2催化剂CO加氢制C_2含氧化物性能的影响

Influence of Preparation Method and Conditions on Performance of Rh-Mn-Li-Ti/SiO_2 Catalyst for CO Hydrogenation to C_2-oxygenates

采用CO加氢反应、程序升温还原(TPR)和CO脱附(CO-TPD)等技术,研究了TiOx/SiO2焙烧温度和Rh-Mn-Li-Ti/SiO2干燥温度对CO加氢合成C2含氧化合物的影响。结果表明,不同温度焙烧对Rh-Mn-Li-Ti/SiO2(ω(Ti)=0.005%)催化剂的C2含氧化合物的生成具有明显不同的促进作用。经873K焙烧的催化剂C2含氧化合物的时空产率达395.0g/(kg(cat)·h),C2含氧化合物的碳数选择性达46.1%;适当延长干燥时间,可将C2含氧化合物的时空收率增加到425.8g/(kg(cat)·h),而选择性无明显变化。TPR结果表明,TiOx/SiO2焙烧温度和催化剂干燥时间可调节RhMn相互作用,而只有当Rh-Mn相互作用处于较弱的状态,催化剂才具有较高的催化性能。CO-TPD的研究表明,随TiOx/SiO2焙烧温度的升高,催化剂上的2个CO脱附峰都逐渐向低温移动,脱附峰面积随焙烧温度不同而变化。

The effects of the calcination temperature of precursor TiO_(x)/SiO_(2) and the drying time for catalyst Rh-Mn-Li-Ti/SiO_(2)(ω(Ti)=0.005%) on its performance for the synthesis of C_(2)-oxygenates from syngas were (investigated) by means of CO hydrogenation, temperature-programmed reduction(TPR), and temperature-(programmed) desorption(CO-TPD). The results obtained show that the calcination temperature of the precursor TiO_(x)/SiO_(2) has a significant effect on the catalytic activity of Rh-Mn-Li-Ti/SiO_2 in the formation of C_(2)-oxygenates. The catalyst calcined at 873 K yielded 395.0 g/(kg(cat)·h) C_(2)-oxygenates with 46.1% selectivity toward C_(2)-(oxygenates) based on carbon. When the drying time of the catalyst was prolonged properly, the yield of C_(2)-oxygenates reached 425.8 g/(kg(cat)·h), with little change in the C_(2)-(oxygenates) selectivity. The TPR results suggest that the calcination temperature of TiO_(x)/SiO_(2) and the drying time of the catalyst Rh-Mn-Li-Ti/SiO_2 could regulate the interaction between the Rh species with the Mn species, and weak interactions between the Rh species and the Mn species would lead to higher catalytic performance. CO-TPD results indicate that both CO desorption peaks shifted to lower temperatures when the (calcination) temperature of TiO_(x)/SiO_2 was higher.