Kinetic Study Of Methanol Aromatization Eigenstatics On ZSM-5 Molecular Sieve

A series of nano-ZSM-5 molecular sieves for methanol aromatization(MTA)was prepared by hydrothermal synthesis,and the effect of conditions such as silica-alumina ratio on the synthesis of molecular sieves and on the catalytic performance of MTA was investigated.The relatively suitable synthesis conditions determined as a function of aromatic yield are:raw material molar ratio Si:Al:TPAOH:H2O=13:1:3.4:575,crystallization time 72h,crystallization temperature 180℃.The grain size of the prepared molecular sieve is between 400 and 600 nm.The methanol aromatization process conditions were studied using a 1.5%Zn-ZSM-5 molecular sieve prepared by the over-impregnation method as a model catalyst.The results show that the aromatic hydrocarbons are first increased and then decreased as the reaction temperature increases,and the catalyst life decreases significantly when the temperature increases to a certain temperature.The aromatic mass yield increases significantly with decreasing operating airspeed,and the catalyst life is improved.The relatively suitable process conditions were determined to be:temperature 430℃,methanol mass air velocity 7.92 h-1,and aromatic mass yield of 20.28%at this condition.The experimental characterization of MTA eigenkinetics was carried out using an isothermal fixed-bed integral reactor at a temperature of 410～460℃,an air speed of 7～95 h-1 and a methanol feed molar fraction of 40%～100%.The five sets of total eigenkinetic model of MTA were established with oxygenated compounds,olefins,aromatic hydrocarbons,alkanes and C1 and above as the target compounds.The experimental data were searched and optimized by a combination of Runge-Kutta integration method and Levenberg-Marquardt complex optimization method,and the parameters of the eigenkinetic model were determined for fitting.The results of the mathematical statistics and residual analysis showed that the proposed five-set total eigenkinetic model was well compatible with the experimental results and was appropriate and reliable.