The Microkinetic Analysis Of Acetylene Hydrogenation Over Pd/Al₂O₃ Catalyst With Different Particle Sizes

Selective hydrogenation of acetylene over Pd based catalysts is an important reaction for production of polymer grade ethylene. Microkinetic method is helpful for efficiently building kinetic models and providing more precise basic data for operation and optimization the industrial hydrogenation process. Pd/Al2O3 with different particle sizes was prepared by the incipient wetness method and acetylene hydrogenation kinetic experiments were carried out over these samples. A microkinetic modeling was carried out based on the sequential hydrogenation mechanism and its applicability over catalysts with different Pd particle sizes and green oil formation amount was testified.It’s found that the exposed surface Pd number of catalysts after reaching stable measured from CO chemisorption agrees with that of Pd(111) surface well calculated from Hardeveld’s model and could be used as the number of active sites for microkinetic modeling. The DFT results based microkinetic parameters is tuned according to kinetic experiments results and the relationship between micro-and macrokinetics. The developed The microkinetic analysis results show that the microkinetic model can fit the kinetic experiment results quite well on catalysts with different Pd particle sizes.Microkinetic simulation results show hydrogenation over all the catalyst tested here has the same most abundant surface species(MASS), C2H4*, and rate determining step, hydrogenation of vinyl group to form ethylene after stable performances are reached. During the initial operation stage, the MASS could be gradually changed from H* to C2H4*. The green oil has great influence on the selectivity and activity. The developed microkinetic models would underestimate the kinetic experiment results, which suggests that the change of catalytic mechanism.