EffectsofSupportsandPromoterAgonPdCatalystsforSelectiveHydrogenationofAcetylene

SiO2,a-Al2O3,g-Al2O3,ZrO2andCeO2wereusedassupportsandAgaspromotertostudytheireffectsonPdcatalystsforselectivehydrogenationofacetylene.ThecatalystswerepreparedbyimpregnatedsynthesisandcharacterizedbyXRD,BETandTEM.Thecatalyticreactionwascarriedoutinafixed-bedreactor.Overall,thelowspecificsurfaceareasupportswerebettertoincreasetheethyleneselectivityathighconversionrateofacetylene.AmongthefourPdcatalystsonlowspecificsurfaceareasupports,thecatalystonlowspecificsurfaceareaSiO2(LSA-SiO2)retainedahighethyleneselectivityevenatcompleteconversion,whiletheothercatalystsshowedsignificantdecreaseintheselectivityatcompleteconversion.TheperformanceofPd/LSA-SiO2wasimportanttodecreasethelossofethyleneinselectivehydrogenationoftraceacetyleneinethylene.AdditionofAgtoPd/LSA-SiO2significantlydecreasedtheformationofethane,C4alkenesandgreenoil,andimprovedtheethyleneselectivityto90%whenPdAg=11and13(w).WhentheratioofPdtoAgwasabove1,theactivityofPd-AgbimetalliccatalystwassimilartothatofPdmonometalliccatalyst,andtheselectivityofethyleneincreasedwithincreasingofamountofAg.WhentheratioofPdtoAgwasbelow1,theactivityofbimetalliccatalystdecreasedwithincreasingofamountofAg,whiletheselectivityofethylenewaskeptunchanged.Theoptimumtemperaturewas200~230℃for0.02%(w)Pd-0.02%(w)Ag/LSA-SiO2togiveahighethyleneselectivityandlowformationofgreenoil.