Alkylation Of Benzene With Methanol And Kinetics Study On Surface Modified HZSM-5

Toluene and para-xylene,as important upstream raw materials for the chemical industry,have been in short supply in China.Due to the vigorous development of the petro chemical industry in recent years,the production capacit y of benzene has increased year by year,and its situation of supply and demand in market was relativel y loose.In addition,with the rapid development of China's coal chemical industry,the capacity of coal-to-methanol has increased significantl y,and there has been a serious excess of methanol.Therefore,the use of benzene and methanol alk ylation reaction to produce toluene and para-x ylene with higher added value has been of great significance for reasonable integration of resources.However,the technology development and the catal ysts research of benzene and methanol alkylation are still immature.There are several key difficulties that restrict the development and design of benzene and methanol alkylation in industry.At present,the low activity of the catalyst,the limited selectivity of para-x ylene,the large amount of by-products,as well as the catalyst's easy deactivation with carbon deposition were the burning issues in alkylation of benzene with me thanol The catal ysts of alk ylation benzene and methanol were researched against these issues in this paper.The performance of benzene and methanol alkylation was effectively improved by modif ying ZSM-5 zeolites with SiO₂.The specific research content was as follows:?1?The HZSM-5 molecular sieve was modified with SiO₂ using a simple method,and the physicochemical properties of modif ication catal ysts were characterized b y XRD,SEM,TEM,N₂ physical adsorption/desorption,NH ₃-TPD,and Py-IR,respectively.The alk ylation performance of the catalysts with a series of SiO₂ loading was also investigated.The experimental results show that under the optimal reaction conditions,the catalyst 10TSZ showed the best performance,and the selectivity of toluene and p ara-x ylene were 57.5%and 26.2%,respectively.Based on the results of characterization and reaction performance,a vivid reaction path of modified HZSM-5 was assumed—SiO₂was deposited on the surface of the catalysts,resulted in covering the B acid site on surface and narrowing.the pore opening-size.?2?Duo to the hierarchical pore catalyst s have excellent catalytic performance,the ZSM-5 molecular sieve was treated with 0.2 mol·L^-1 NaOH to obtain a hierarchical por ous HZSM-5 catal ysts in this paper.The expected catal ysts were obtained by SiO₂ modified hierarchical porous HZSM-5,and the relationship between the ph ysical and chemical properties of the modified catal ysts and the reaction performance was researched by using SEM,N₂physical adsorption/desorption,NH ₃-TPD,and Py-IR.The catal yst with the best alkylation performance was 14TS-ATZ,and the selectivit y of toluene and para-x ylene up to 60.5%and 19.1%,respectively,and the total selectivity of toluene and x ylene achieved 94.5%.?3?Based on eliminating the effect of internal and external diffusion for alkylation reaction,a single factor experiment was performed using 10TSZ.The effects of reaction temperature,mass space velocit y,and the molar ratio of methanol to benz ene in the feed on the performance of the alkyla tion reaction were investigated,providing reference date for s ubsequent orthogonal experiments in intrinsic dynamics.The simulated calculations showed that the activation energies of the main alk ylation rea ctions of benzene and met hanol were 4970 J·mol^-1 and 200 J·mol^-1,respectively.Model tests showed that the calculated values of the model and the experimental data fit well.