Preparation Of Palladium Alloy Membrane And Catalytic Performance Of Membrane Reactor

The palladium-based membrane reactor can effectively catalyze the one-step oxidation of benzene to produce phenol in H₂-O₂ reaction system,but how to further improve the product yield and stability still needs to be solved from the point of view of the design optimization and preparation technology of membrane reactor.Compared with pure palladium membrane,palladium alloy membrane has improved hydrogen permeability selectivity and stability,and has a good application prospect in the fields of hydrogen separation,CO₂ capture and catalytic reaction involving hydrogen.In this paper,palladium-silver alloy（Pd Ag）membrane and palladium-gold alloy（Pd Au）membrane with excellent hydrogen permeation selectivity were prepared to solve the problems of palladium-base membrane reactor,and palladium alloy membrane reactor was constructed to improve the catalytic reaction performance and stability of the membrane reactor.The main research contents of this paper are as follows:（1）Pd Ag membrane with thickness of about 5μm was prepared on the surface of pencil-modified ceramic tube（α-Al₂O₃）by sequential deposition electroless plating（Se-ELP）method.The hydrogen permeation flux of Pd Ag/α-Al₂O₃ membrane at 823 K and 100 k Pa is 0.31 mol·m^-2·s^-1,and the ideal selectivity of H₂/N₂ is 745.It was found that when the benzene flow rate was 3.5m L·min^-1 and the H₂-O₂ feed ratio was 1.8,the catalytic effect was the best,and the benzene conversion and phenol selectivity reached 1.49%and 71.21%.（2）Yttrium stabilized zirconia（YSZ）alumina（Al₂O₃）hollow fiber was prepared by phase conversion sintering technology.Compared with two electroless plating methods,Co-ELP and sequential deposition,it was found that Pd Ag membrane prepared by Se-ELP method had higher thermal stability and H₂/N₂ selectivity.The ideal selectivity of H₂/N₂remains around 750 in 100 h test at 823 K hydrogen atmosphere.The Pd Ag/YSZ-Al₂O₃membrane reactor catalyzed benzene to phenol.When the benzene flow rate was 2 m L·min^-1 and the H₂-O₂ feed ratio was 1.67,the catalytic effect was the best,and the benzene conversion and phenol selectivity reached 10.49%and 81.22%.（3）Pd Au membrane with thickness of 4μm were prepared onα-Al₂O₃ and YSZ-Al₂O₃hollow fibers by Se-ELP method,respectively.After alloying at 823 K and 100 k Pa hydrogen atmosphere for 100 h,the Pd Au/YSZ-Al₂O₃ membrane still maintains an ideal H₂/N₂selectivity of 750 and a hydrogen permeation flux of 0.11 mol·m^-2·s^-1.The catalytic performance of Pd Au membrane showed that the catalytic effect of Pd Au membrane was better than that of Pd Ag membrane,and the catalytic effect of Pd Au/YSZ-Al₂O₃ membrane was the best when the hydrogen-oxygen feed ratio was 1.8,the benzene conversion rate was17.74%,and the selectivity of phenol was 93.56%.The membrane reactor has the advantages of high hydrogen permeability and good reaction stability of Pd Au membrane,which can effectively improve the reaction performance of one-step oxidation of benzene to phenol.