Kinetic Model Study On Naphtha Catalytic Cracking For Ethylene And Propylene Production

It is an energy-saving process with higher propylene selectivity and higher feedstock adaptability of catalytic cracking naphtha to ethylene and propylene. According to lumping theory, a six-lump kinetic model was proposed and its mathematic expression was also given. The experimental data for solving model obtained from a fixed bed micro-reactor and the reaction rate constants of every reaction temperature was evaluated by the nonlinear least square theory with MATLAB. Finally we solved the frequency factors and apparent activation energies. According to the test, it was revealed that the relative errors between the calculated values and the experimental values were less than 14%. Based on the test of the proposed model, the variety laws of the yields of ethylene and propylene with reaction temperature and WHSV were predicted. The results showed that they fit well with the experimental results. The experimental results showed that the yield of propylene is obviously more than the yield of ethylene. The mass ratio of propylene to ethylene is between 1.0 and 2.0. It is obviously better than the traditional processes.The influences of different reaction temperature, WHSV, the mass ratio of water to oil on cyclohexane, normal-hexane, normal-heptane were investigated. The results showed that the catalytic cracking ability of normal-alkanes decreased with the increase in the number of carbon atoms; in the higher reaction temperature (reaction temperature higher than 640℃), with the same carbon atoms of alkanes, the reaction capacity of cyclohexane was better than normal-alkanes.