Pd/Ce基催化剂催化氧化氯苯的性能

Catalytic performance of Pd/Ce-based catalyst for oxidation of chlorobenzene

采用等体积浸渍法制备Pd/Al2O3系列催化剂,考察不同Pd负载量对催化剂催化氯苯活性的影响,结果表明0.75%Pd/Al2O3催化剂活性最优,采用BET、H2-TPR、SEM等对催化剂进行表征分析,表明添加Ce后氧化能力增强,催化氧化效率提高。对催化产物进行分析,使用离子色谱分析了无机Cl-生成情况及其选择性,使用GC-MS定性分析了有机副产物,发现350℃时有少量苯生成。同时考察了焙烧温度、氯苯浓度、空速对催化活性的影响,结果表明焙烧温度过高或过低都会影响催化剂的活性,在550℃焙烧的催化剂活性更优,400℃时氯苯转化率为96%;氯苯入口处质量浓度在1500~6000mg/m^3时,浓度升高,催化氯苯活性降低;空速在15000~30000h-1时,空速对氯苯催化活性影响不大,但继续提高空速会明显降低催化活性。

Series of Pd/Al2O3 catalysts were prepared by equal volume impregnation method.The effects of different Pd loadings on the catalytic activity of chlorobenzene were investigated.The results showed that the activity of 0.75%Pd/Al2O3 catalyst was the highest.Based on the purpose of reducing the amount of precious metals by introducing rare earth metal to improve the performance of the catalyst,Ce was introduced into the catalyst of 0.5%Pd/Al2O3,and the optimal ratio of Pd/Ce catalyst was obtained.It was found that the activity was best when the Ce amount was 2.5%by weight.The characterizations of the catalyst by BET,H2-TPR,SEM,etc.confirmed that the oxidation capacity was enhanced and the catalytic oxidation efficiency was improved through the addition of Ce.In addition,the catalytic products were analyzed with ion chromatography and GC-MS.The results showed that a small amount of benzene was formed at 350℃.At the same time,the effects of calcination temperature,chlorobenzene concentration and space velocity on the catalytic activity were investigated.The results showed that the calcination temperature greatly affected the activity of the catalyst.The activity of the catalyst calcined at 550℃was the best,and the CB conversion was 96%when calcination temperature was 400℃.When the concentration of chlorobenzene was 1500—6000mg/m^3,the activity of chlorobenzene decreased with the concentration.When the space velocity was in the range of 15000—30000h-1,it had little effect on the catalytic activity of chlorobenzene.