Selective hydrogenation of 1,4-butynediol to 1,4-butenediol:Pd/ZrO2 catalyst and alkali metals modification
Pd/ZrO2 and alkali metals(M)modified Pd/M/ZrO2 catalysts were prepared by incipient-wetness impregnation with ZrO2 obtained from Zr(OH)4 calcination as support,and characterized by XRD,BET,TEM and HRTEM,CO2-TPD,XPS.The activity,selectivity and stability of the catalysts in the selective hydrogenation of 1,4-butynediol(BYD)to 1,4-butenediol(BED)were evaluated,and the influence of reaction atmosphere and alkali metals modification on the activity and stability of the catalysts were analyzed.The results showed that under 50℃and 2.40 MPa H2 pressure,1.0%Pd/ZrO2(1.0%being the mass fraction of Pd)exhibited high catalytic activity of 0.048 molBYD/(gPd·s),and BED selectivity of 91.2%with complete conversion of BYD.The introduction of ammonia into the reaction mixture inhibited the hydrogenation activity and improved the BED selectivity to 95.6%with complete conversion of BYD.Modification of Pd/ZrO2 with alkali metals(Li,Na,K,Rb,Cs)improved the selectivity of BED with Rb the most effective modifier showing BED selectivity up to 94.1%.