Kinetics Of Methanol Aromatization On Modified ZSM-5 Molecular Sieve

Methanol aromatization technology（MTA）is of great significance for improving the added value of methanol products and alleviating the contradiction between supply and demand of aromatics products in China.At present,the research on MTA at home and abroad mainly focuses on the development and application of catalysts,while the related thermodynamic analysis and kinetic research are less reported,which is not conducive to the in-depth research of MTA technology.Based on the experimental data of fixed bed reactor,this paper carried out the preparation of efficient catalysts Thermodynamic analysis and intrinsic kinetics study of MTA process.The paper prepared nano molecular sieves with different silicon to aluminum ratios using in-situ synthesis method.TEM analysis results showed that the particle size of the prepared ZSM-5 nano molecular sieve increased with the increase of silicon to aluminum ratio.The smaller the silicon to aluminum ratio,the smaller the particle size of the molecular sieve nanoparticles and the tighter the stacking.Under the conditions of 450℃,atmospheric pressure,and WHSV of 5 h^-1,the effects of silicon aluminum ratio and Zn loading content on the MTA performance of Zn/ZSM-5molecular sieve were experimentally investigated.The optimal silicon aluminum ratio and Zn loading content were ultimately determined to be 23%and 0.3%,respectively.Through GC-MS analysis of the distribution of MTA products,it was found that the reaction products were mainly composed of 32 substances.Excluding products with concentrations below 1000ppm in olefins and alkanes,there were a total of 26 substances.Atomic matrix analysis was conducted on these 26 substances,and 23 stoichiometric independent chemical reactions of the reaction system were determined.Thermodynamic analysis was conducted under atmospheric pressure,623 K-873 K conditions,and the results showed that the MTA reaction is a strong exothermic process,The equilibrium constant of most chemical reactions decreases with the increase of temperature,and a few reactions can not occur spontaneously with the increase of temperature.The 0.3%Zn-ZSM-5 molecular sieve prepared by in-situ synthesis method was used as a model catalyst.Under normal pressure,375℃～500℃,and methanol mass space velocity（WHSV）of 20 h^-1～45 h^-1,the reaction tube size was determined in an isothermal fixed bed reactor（reaction tube size:reaction tube size）Φten×A study on the intrinsic kinetics of MTA was conducted at 3 mm（L=300 mm）,and a total of 36 sets of intrinsic kinetic experimental data were obtained.The Runge Kutta integration method and Levenberg Marquardt optimization method were used to search and optimize experimental data,and a ten lumped intrinsic dynamics model of MTA was established.The statistical test results indicate that the decisive indicators of the ten lumped dynamic model obtained from the estimation are².Both are greater than 0.9 and the F-statistic is greater than 10F_0.05;The residual distribution results indicate that the deviation between the experimental and calculated values of the model is mostly within 10%,indicating that the established ten lumped intrinsic dynamics model is suitable and reliable.