Study On Preparation And Catalyst Property Of Palladium Loaded Egg-Shell Nano-Catalyst

The preparation of egg-shell type Pd-loaded catalysts with hollow nano silica and the microstructure of catalysts were studied systematically. And the catalytic properties of these Pd-loaded catalysts in acetylene hydrogenation reaction were investigated thoroughly.Hollow silica nano particles (HSNP) were synthesized by sol-gel method with nano CaCO3as template and sodium silicate as the silica source. HSNP have a diameter of60-100nm, specific surface area of300-1000m2/g and pore diameter of2-7nm. And egg-shell structured Pd-loaded catalysts were prepared by an impregnation method using HSNP as the support and PdCl2as the precursors. The structure of catalysts was remarkably affected by the preparation conditions, and the optimal calcinations temperature was400℃. By using analytic instruments such as TEM, XRD, ICP etc. it was found that PdO was loaded on the surface of HSNP with the size of about lOnm in pre-reduced catalysts. And the Pd particle size in reduced catalysts was determined by the rising speed of reduction temperature. The slower of the rising speed of reduction temperature, the smaller the Pd particle size it will be. And the Pd particle size of catalysts prepared in this experiment was about 4-6nm.The catalytic properties of Pd loaded catalysts were investigated in acetylene hydrogenation reaction. And different Pd content catalysts were tested by high press micro-reactor. It was reported that the Pd loaded catalysts with0.04%Pd content were the best one for this reaction. The reaction temperature was40-50℃, the speed of gas flow was3900mL/h and the press was0.1MPa. The selectivity of ethylene can reach98%while the conversion of acetylene is100%. The result indicated that the egg-shell Pd loaded catalysts has a good activity.