Pt/Al_2O_3和Pt-Cu/Al_2O_3催化CCl_4氢化脱氯反应

制备了Al2O3负载Pt单金属催化剂和负载Pt-Cu双金属催化剂,比较了二者不同还原温度对其催化CCl4氢化脱氯反应性能的影响。单金属Pt催化剂上主要生成CHCl3,而双金属Pt-Cu催化剂上产物随催化剂制备时的还原温度不同而异,当催化剂经400℃用H2还原后产物主要为CHCl3,而当催化剂经800℃用H2还原后产物主要为CCl2CCl2。由于CCl4氢化反应是强放热反应,催化剂表面局部过热使得在反应中生成的C2等产物聚合结焦,覆盖了催化剂的活性中心,导致催化剂失活。因此,通过加入甲醇作为稀释剂以带走部分反应热可提高催化剂的稳定性。同时也降低了CHCl3的选择性,提高了CCl2CCl2的选择性。

Hydrodechlorination of CCl4 over Pt/Al2O3 and Pt-Cu/Al2O3 Catalysts

Hydrodechlorination of CCl4 over Pt/Al2O3 and Pt-Cu/Al2O3 bimetallic catalysts was studied. The influence of reduction temperature of the catalysts on catalytic performance was investigated. CHCl3 was the main product over Pt/Al2O3, but products varied with reduction temperature over Pt-Cu/Al2O3. The main product was CHCl3 over Pt-Cu/Al2O3 reduced at 400 ℃, while the main product was CCl2CCl2 over the catalyst reduced at 800 ℃. Hydrodechlorination of CCl4 is a strongly exothermic reaction, which leads to local overheating on the surface of catalysts. C2 products may carbonize on overheated sites and cover the active sites, which resulted in deactivation of the catalysts. The stability of catalysts can be improved by adding CH3OH as solvent, which entrapped reaction heat. In addition, the selectivity towards CCl2CCl2 was also increased by adding CH3OH.