载钯量对轻质烷烃异构化催化剂(Pd/HM)性能的影响

采用MR-GC80型压力微反装置,在空速2h~(-1)、氢油分子比8:1、氢压2MPa、反应温度260℃和280℃反应条件下,考察了钯/氢型丝光沸石(Pd/HM)催化剂的含钯量对正己烷异构化反应活性,选择性,稳定性的影响,并结合脉冲激反装置对反应机理进行了探讨。结果表明:钯含量在0.025—0.25%范围内,活性和选择性均随含钯量的增加而提高;超过0.85%,则呈下降趋势;HM载钯后稳定性有明显的改善。催速失活试验表明:0.25%Pd/HM和0.5% Pd/HM催化剂具有相同的稳定性。在Pd/HM上正己烷异构化反应的机理为酸性和双功能结合的复合机理。

Effect of palladium concentration on the behaviour of Pd/HM alkane isomerization catalysts

The effect of palladium concentration on the activity and selectivity of alkane isomer- ization Pd/HM catalysts has been investigated under conditions nearly the same as in in- dustrial practice. It has been concluded that both the activity and selectivity increase li- nearly with metal concentration in the range of 0. 025-0. 25% Pd. The optimal metal concentration lies in the range of 0. 25-0. 5% Pd; beyond 0. 85% Pd, however, the ac- tivity and selectivity decrease again. The behaviours of HM and Pd/HM catalysts are rather different from each other. Incorporation of even very small amount of palladium into HM will largely improve the stability. It remains unchanged in the whole reaction time longer than 10 h in our experiments. Even for long time (1000h) running in industrial practice, the catalysts prove as efficient as in our laboratory tests. Based on experimental results and beha- viours of metal and mordenite, the mechanism of the isomerization of light paraffin hydrocarbons has been proposed. It was revealed that both the bifunctional and acidic mechanism are involved in alkane isomerization with Pd/HM catalysts.