性能优异的Pd-[DBU][Cl]/AC无汞催化剂在乙炔氢氯化中的应用  

Enhanced performance of Pd-[DBU][Cl]/AC mercury-free catalysts in acetylene hydrochlorination

作　　者：董兴宗 刘广业[1] 陈兆安[1] 张权 徐云鹏[1] 刘中民[1,2] Xingzong Dong;Guangye Liu;Zhaoan Chen;Quan Zhang;Yunpeng Xu;Zhongmin Liu(National Engineering Research Center of Lower‐Carbon Catalysis Technology,Dalian National Laboratory for Clean Energy,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China;School of Chemical Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院大连化学物理研究所,大连洁净能源国家实验室,低碳催化技术国家工程研究中心,辽宁大连116023 [2]中国科学院大学,化学工程学院,北京100049

出　　处：《Chinese Journal of Catalysis》2023年第3期137-147,共11页催化学报（英文）

基　　金：国家重点研发计划(2016YFB0301603);辽宁振兴人才计划(XLYC1905017).

摘　　要：氯乙烯单体(VCM)作为重要的有机化工原料,主要用于聚氯乙烯(PVC)生产,在煤炭资源丰富的国家和地区氯乙烯单体的制备很大程度上依赖乙炔氢氯化反应.目前工业乙炔氢氯化过程仍然使用传统的活性炭负载氯化汞(HgCl_(2)/AC)作为反应的催化剂,但该催化剂的易挥发性和高毒性对人类健康和生态环境造成了极大的危害,因此探索和发展性能优异且环境友好的无汞催化剂尤为重要.Pd基催化剂展现出较好的乙炔氢氯化活性,但较差的化学稳定性限制了其工业应用.因此,通过调节Pd(Ⅱ)活性中心的电子结构、配位状态和微环境去提升Pd基催化剂的化学稳定性是当前的研究热点和挑战.相关的文献结果表明, Pd基催化剂的快速失活主要归因于Pd(Ⅱ)被乙炔分子还原成Pd(0),导致催化剂表面大量积碳的形成以及活性Pd物种流失,根本原因是催化剂活性位点对乙炔的吸附较强而对氯化氢的吸附较弱,这种不匹配的吸附会造成吸附态的乙炔无法与氯化氢发生有效碰撞生成产物氯乙烯,因此如何促进氯化氢的高效吸附和活化是阻止催化剂失活的关键因素.基于我们前期的工作(Mol.Catal.,2022,525,112366)和相关文献调研发现, 1,8-二氮杂二环十一碳-7-烯氯盐([DBU][Cl])对氯化氢分子有较强的吸附和活化能力,而且[DBU][Cl]作为配体能与Pd(Ⅱ)金属中心配位构建一个稳定的活性位点.本文制备了一系列Pd-[DBU][Cl]/AC催化剂去提升Pd基催化剂在乙炔氢氯化过程中的化学稳定性,催化剂的乙炔氢氯化活性和化学稳定性在固定床微反应器上评价.采用N_(2)物理吸附、X射线光电子能谱(XPS)、电感耦合等离子体发射光谱(ICP-OES)、程序升温脱附(TPD)和热重分析(TGA)等表征方法研究了Pd基催化剂的失活原因以及Pd-[DBU][Cl]/AC催化剂稳定性增强的原因.通过DFT理论模拟分析了乙炔、氯化氢和C_(2)H3Cl在Pd活性位点上的吸附行�Compared with the rapid deactivation of the Pd/AC catalyst, an eco-friendly Pd-[DBU][Cl]/AC([DBU][Cl], 1,8-diazabicyclo[5.4.0]undec-7-ene hydrochloride) catalyst with enhanced stability was synthesized and applied in the hydrochlorination of acetylene. The Pd-20[DBU][Cl]/AC catalyst exhibits 96.7% acetylene conversion and 98.9% selectivity of vinyl chloride within the 24 h evaluation under the conditions of T = 180 ℃, GHSV(C_(2)H_(2)) = 360 h^(-1)and V(HCl)/V(C_(2)H_(2)) = 1.2. The enhanced stability of the Pd-[DBU][Cl]/AC catalyst is attributed to the prevention of the reduction of Pd(Ⅱ) to Pd(0), the inhibition of the formation of coke deposition on the catalyst surface, and the reduction of the loss of Pd species during the reaction. TPD characterization and DFT theoretical simulations confirmed that the PdCl_(2)-[DBU][Cl] complex has stronger adsorption of HCl and weaker adsorption of C_(2)H_(2)and C_(2)H3Cl compared to PdCl_(2). Furthermore, the catalytic mechanism of acetylene hydrochlorination over the PdCl_(2)and PdCl_(2)-[DBU][Cl] site was put forward based on theoretical simulations. The good activity and stability of Pd-20[DBU][Cl]/AC in the 60 h lifetime test indicates that it is likely to be a promising alternative to HgCl_(2)catalysts.

关 键 词：乙炔氢氯化 无汞催化剂 Pd复合物催化剂 提升稳定性 吸附能 

分 类 号：TQ222.423[化学工程—有机化工] TQ426