乙炔氢氯化PdCl_2/C催化剂失活原因分析

采用浸渍法制备了PdCl2/C催化剂,考察了PdCl2/C催化剂用于乙炔氢氯化反应制取氯乙烯的催化性能,并用微结构分析仪、扫描电子显微镜、热重分析和电感耦合等离子体发射光谱等表征方法对PdCl2/C催化剂的失活原因进行了分析。实验结果表明,PdCl2/C催化剂具有很高的初活性,在反应温度110~180℃、常压、空速120h-1、V(HCl)∶V(C2H2)=1.15的条件下,乙炔的转化率大于90%,氯乙烯的选择性大于97%,但该催化剂使用寿命很短,失活迅速。表征结果表明,催化剂表面积碳和活性组分PdCl2流失(损失率达40%以上)是导致PdCl2/C催化剂失活的主要原因。通过加入KCl助剂有效地抑制了活性组分PdCl2的流失,PdCl2/C催化剂的性能得以改善。将失活PdCl2-KCl/C催化剂用硝酸氧化除积碳后,催化剂的活性可以恢复。

Deactivation of PdCl2/C Catalyst in Hydrochlorination of Acetylene

Deactivation of PdCl2/C catalyst in hydrochlorination of acetylene to vinyl chloride was studied.The catalyst was prepared by impregnation.BET,SEM,TG and ICP-AES were used to observe the cause of catalyst deactivation.Under reaction conditions of temperature range of 110-180 ℃,pressure 0.1 MPa,space velocity 120 h-1 and feed ratio V(HCl) ∶V(C2H2) 1.15,conversion of acetylene and selectivity to vinyl chloride were more than 90% and more than 97% respectively.The initial activity of catalyst was high,but it declined rapidly along with reaction time.Characterizations proved that a loss of more than 40% active component PdCl2 after reaction of several hours only and surface carbon deposition greatly decreased the specific surface area and pore volume,which were two main reasons of catalyst deactivation.Addition of KCl to PdCl2/C catalyst as a promoter not only reduced the loss of active component PdCl2 dramatically but also enhanced the conversion of acetylene and selectivity to vinyl chloride,so catalytic activity of PdCl2-KCl/C could be maintained.The carbon deposited on surface of the deactivated PdCl2-KCl/C catalyst can easily be removed by oxidation with nitric acid solution and catalyst can be reused.