Study On The Reaction Performance Of Selective Alkylation Of Toluene With Methanol Over Modified HZSM-5 Zeolite

The para-xylene is an important chemical,which originates from naphtha cracking and catalytic reforming processing.As we all known,the oil routes for para-xylene are limited to the lack of oil resource.Relatively surplus toluene for its use far less than benzene and xylene and the low cost of methanol with the development of C₁ chemical,currently,the alkylation of toluene with methanol is receiving increased attention due to its non-oil feeds.In the present research,HZSM-5 zeolite catalyst modified by Ca was first used as research object.The reaction conditions,such as reaction temperature,WHSV and flow of carrier gas,were investigated to optimize the reaction performance on a fixed bed reactor.The experimental results show that the optimum reaction operational condition is reaction temperature:460 ^oC,WHSV:4.8 h^-1,n?N₂?/n?T+M?:8,n?H₂?/n?T+M?:8.Then,the effect of Ca and P alone modified HZSM-5 catalysts on the alkylation reaction performance was investigated.The experimental results show that the moderate impregnation of Ca and P could regulate acidity and pore size to increase para-selectivity,which is attributed to the inhibition of isomerization of para-xylene on the acid sites,and the para-selectivity reached 97.87%and 96.23%.Besides,the reaction performance of compound modified HZSM-5 with Ca and P could be obtained.The results show that the para-selectivity of Ca and P compound modified HZSM-5 is lower than Ca or P alone modified HZSM-5,and the increase extent of reactivity of Ca and P compound modified HZSM-5 is limited in comparison of Ca or P alone modified HZSM-5.It investigated that the Ca and P compound modified HZSM-5 played a negligibly synergistic effect in toluene alkylation.The narrower pore size owing to the modification easily resulted in deactivation although the process could significantly enhance the para-selectivity in the methylation reaction,and the worse stability was obtained.In the present research,the addition of Ni to 5.0Mg-ZSM-5zeolite which has high para-selectivity promoted ethylene hydrogenation to ethylene in the condition of hydrogen,which inhibited the formation of coke,and the stability of zeolite was improved.The results show the stability of modified 5.0Mg-ZSM-5 zeolite remains excellent when the loading of Ni is 3.0%,in here,toluene conversion fell from 14%?initial toluene conversion?to 7%in the reaction period of 29 h.