The Microkinetic Modeling Of Acetylene Hydrogenation Over Pd/Al₂O₃Catalyst

The ethylene produced from steam cracking process contains small amont of acetylene. In order to prohibit the detoriate effect of C2H2on the following process, C2cut-out hydrogenation is used genarally in industry to lower the C2H2content less than5ppm. Acetylene hydrogenation kinetics is of great significance to the optimization of reactor operation. In this thesis, a series of Pd/Al2O3catalyst was prepared and charaterized. The steady-state kinetic experiment and microkinetic simulation was carried out, and the catalyst deactivation phenomenon was studied. The microkinetic simulation results show that the most abundant surface species is H*, rate determing steps for acetylene conversion into ethylene are C2H2adsorption and hydrogenation of C2H3*to C2H4*and RDS for acetylene conversion into ethane is hydrogenation of C2H5*to C2H6*over different catalyst in the range of experimental conditions. The change of temperature, C2H2pressure and H2/C2H2has no influence on the most abundant surface species and RDS for acetylene conversion into ethylene, while have some effect on the RDS for acetylene conversion into ethane. The change of Pd particle size has no influence on C2H2and H2reaction order, while the C2H2activation energy decreases as the particle size decreases. The simulation results also show that high C2H4selectivity can obtain under higher reaction temperature and lower H2/C2H2. The deactivation rate is mainly influenced by C2H2concentration and reaction temperature. The lower deactivation rate can be obtained under lower C2H2concentration and reaction temperature. The steady-state reaction rate is mainly controlled by temperature and H2/C2H2, and higher steady-state reaction rate is obtained under higher temperature and higher H2/C2H2.