Pd/Ce基催化剂催化氧化氯苯的性能

doi:10.16085/j.issn.1000-6613.2019-0033

摘要/Abstract

摘要：

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/m³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。

关键词: 氯苯, Pd/Ce基催化剂, 活性, 产物分析

Abstract:

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/m³, 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.

Key words: chlorobenzene, Pd/Ce-based catalysts, oxidation, by-product analysis

中图分类号:

X701

梁文俊,杜晓燕,任思达,李坚,何洪. Pd/Ce基催化剂催化氧化氯苯的性能[J]. 化工进展, 2019, 38(10): 4574-4581.

Wenjun LIANG,Xiaoyan DU,Sida REN,Jian LI,Hong HE. Catalytic performance of Pd/Ce-based catalyst for oxidation of chlorobenzene[J]. Chemical Industry and Engineering Progress, 2019, 38(10): 4574-4581.

图/表 16

图1 实验装置示意图 1—空气泵；2—干燥管；3—转子流量计；4—质量流量计；5—氯苯发生瓶；6—水浴锅；7—混气瓶；8—换向阀；9—石英反应管；10—管式电炉； 11—温控仪；12—气相色谱仪；13—尾气吸收瓶

图2 不同Pd负载量的Pd/Al2O3催化剂催化氧化CB活性

图3 不同Ce负载量对0.5%Pd/Al2O3催化剂活性的影响

图4 不同焙烧温度下催化剂的催化氧化CB活性

图5 催化剂H2-TPR谱图

表1 不同Pd负载量的催化剂反应前后的比表面积数据

催化剂	比表面积/m²·g^-1
催化剂	反应前	反应后
0.1%Pd/Al₂O₃	180	177
0.2%Pd/Al₂O₃	178	174
0.3%Pd/Al₂O₃	179	172
0.4%Pd/Al₂O₃	175	175
0.5%Pd/Al₂O₃	171	171

表2 催化剂比表面积和孔结构数据

催化剂

比表面积

/m²·g^-1

0.5%Pd/ Al₂O₃

图6 催化剂扫描电镜图片

图7 催化剂扫描电镜图片

表3 两种催化剂催化氧化CB的Cl-浓度和Cl-选择性结果

反应温度/℃	0.5%Pd/ Al₂O₃		0.5%Pd-2.5%Ce /Al₂O₃
反应温度/℃	Cl^-浓度 /mg·L^-1	Cl^-选择性 /%	Cl^-浓度 /mg·L^-1	Cl^-选择性 /%
200	2.37	2.3	2.71	2.1
250	3.87	2.6	3.96	2.7
300	12.34	2.5	15.73	5.9
350	39.76	8.6	44.56	9.9
400	62.92	9.1	70.82	10.1
450	66.21	10.8	78.46	11.5

图8 两种催化剂催化氧化CB的Cl-选择性

表4 不同温度下有机副产物生成情况

样品	200℃	250℃	300℃	350℃	400℃	450℃	500℃
0.5%Pd/Al₂O₃	无	无	无	无	无	无	无
0.5%Pd-2.5%/Al₂O₃	无	无	无	苯	无	无	无

图9 350℃时有机副产物生成情况

图10 不同CB浓度下催化剂催化氧化CB活性

图11 不同空速下催化剂的催化氧化CB活性

表5 不同空速下0.5%Pd-2.5%Ce/Al2O3催化剂的T 50和T 90

空速/h^-1	T ₅₀/℃	T ₉₀/℃
15000	316	379
30000	321	389
60000	346	419
120000	373	450
240000	398	＞450

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