Thermodynamic Calculation And Study On Conditions Of Catalytic Reaction For Isobutane Dehydrogenation

Our country has rich resources of C4, which widely exists in the petroleum gas, natural gas, and FCC gas and other C4 fraction, of which 40% of isobutane that has a great commercial value. But, our country C4 fractions of chemical utilization rate is only 7.8%, and over 60% in developed countries, most used as civil liquefied petroleum gas fuel, whose utilization rate is low. Its downstream products is dependent on foreign imports. The catalytic dehydrogenation of isobutene to isobutylene is an important developing direction in our country at present, as the industrial demand is growing rapidly, there is no reports about industrialized production in the degeneration of isobutane to isobutylene.First of all, starting from the reaction mechanism, the basic principle of chemical thermodynamics and literature data were used in the paper. By using the EXCEL software the six independent reactions were carried out on the detailed calculation. The reaction system was given based on a thermodynamic parameters and the reaction temperature, pressure, and the ratio of isobutane to hydrogen and inert gas. The influence of them on the chemical reactions predicts the optimal reaction conditions:isobutane dehydrogenation is endothermic reaction and at 850k the AHr=245kJ/mol, and equilibrium conversion is 80%. To rise temperature, reduce the pressure and the ratio of hydrogen and isobutane can make the equilibrium conversion increase.Based on existing mini-bed reactor controlled by computer. With chromatography in laboratory for the experiments of isobutane dehydrogenation to isobutylene. With multiple impregnation method and blending method the preparation of catalysts over a single carrier and the double carriers was finished loading oxide V-Fe-K compound. For the catalytic dehydrogenation reaction of isobutane, the influences of reaction temperature and gas space velocity and the types of catalyst supports as the independent variables on conversion and selectivity were studied. The main and side effects of reaction mechanism of the reaction system were studied and the relationship between the activation energy was compared in order to investigate the influence of temperature on the selective rule.The experimental results show that the order of activity from big to small for the five kinds of catalyst carrier is ZSM-5>’Y-A12O3> MgO> TiO2> SiO2. The order of selectivity for isobutene is completely reverse. The catalysts with double carrier are better than the single carrier catalysts. The best catalyst carrier for V-Fe-K/MgO+ZSM-5. The yield of isobutylene is 34.3% and the selectivity of isobutane is above 95%; The activation energy of the main reaction is smaller than that of R2 and more than that of R3. The raise of temperature makes the deep cracking reaction increase and C1 and C2 increase, but C3 and isobutylene decrease.