Application Of Supported Ionic Liquid-bimetallic Catalyst In Selective Hydrogenation Of Acetylene

Ethylene,as a common chemical raw material and an important part of the national economy,plays an important role in chemical production.In the process of producing ethylene,1.0%of acetylene is often produced.These trace amounts of acetylene will poison the catalyst of the downstream polyethylene industry,which will not only reduce the activity of the catalyst,but also reduce the quality of polyethylene products.Therefore,it is particularly important to remove trace acetylene in ethylene.The most common method in industry is to choose the hydrogenation method.Always,palladium catalysts have high activity,but have extremely low ethylene selectivity and stability.Because the ethylene produced during the reaction was not desorbed from the active center in time,resulting in excessive hydrogenation of ethylene.Therefore,the palladium-based catalyst is modified to improve the ethylene selectivity of the catalyst,which is also the research focus of acetylene hydrogenation reaction.In this paper,Cu is used to build a supported ionic liquid-bimetallic catalyst system,and further modified and supported ionic liquid palladium-based catalyst.During the selective hydrogenation of acetylene,the performance of the palladium-based catalyst is significantly improved,including catalytic activity,ethylene selectivity,and stability.The experimental data of selective hydrogenation evaluation of acetylene shows that when the reaction temperature is 170?and the space velocity is 6000 h^-1,the Pd-Cu-IL/Al₂O₃catalyst?Ionic Liquid,IL?obtains nearly 100.0%conversion of acetylene,At this time,the ethylene selectivity can be as high as 96.5%.On the other hand,the effects of space velocity,reaction temperature,reduction temperature,ionic liquid loading and copper loading on the acetylene hydrogenation of Pd-Cu-IL/Al₂O₃catalyst were further studied.The XRD and TEM characterization results indicate that both Pd and Cu are well dispersed on the catalyst.In addition,the H₂-TPR analysis shows that the main valence state of Cu species in the Pd-Cu-IL/Al₂O₃catalyst prepared under this 170?reduction condition is Cu⁺.The XPS results indicate that Cu and Pd have electronic effects and may have alloying effects,which leads to an increase in selectivity.Further DFT calculation results show that acetylene is easily adsorbed on Cu⁺,and the adsorbed acetylene molecules tend to undergo a hydrogenation step and desorb the ethylene molecules,which is why Pd-Cu-IL/Al₂O₃catalysts have excellent catalytic performance.In addition,the experimental data also shows that the addition of Cu can also improve the activity of the palladium-based catalyst.In addition,the Pd-Cu-IL/Al₂O₃catalyst showed stable catalytic performance in the post-acetylene hydrogenation process.It maintained a high conversion rate of acetylene in the long-term reaction evaluation within 250 h,and maintained a high of 96.5%during this period Ethylene selectivity.Therefore,this work also provides a Pd-Cu-IL/Al₂O₃catalyst with excellent performance for industrial ethylene production.In addition,Pd-Au-IL/Al₂O₃and Pd-Ag-IL/Al₂O₃catalysts were also prepared in this paper,and the process conditions of the catalyst in acetylene hydrogenation reaction were optimized.Next,the performance of Pd-Cu-IL/Al₂O₃catalyst was also compared in the acetylene selective post-hydrogenation process,including space velocity,reaction temperature,metal loading and ionic liquid loading;in the research process of Pd-Ag-IL/Al₂O₃catalysts,screened types of ionic liquids,among which Pd-Ag-IL/Al₂O₃catalysts made by[PY₁₄][NTF₂]and[Bmim][PF₆]have excellent catalytic performance under low temperature conditions of 90?,with ethylene selectivity up to 83.4%the above.Finally,the characterization also shows that the electronic effect is the main reason that affects the performance of the supported ionic liquid-bimetallic catalyst.The greater the electronic effect,the greater the performance improvement of the palladium-based catalyst.