Alkylation Of Toluene With Methanol Over Modified Catalysts

With the development of polyester industry, the demand of para-xylene has been increased quickly so that the production can't meet it. Presently para-xylene is generated through naphtha cracking, catalytic reforming, coke by-products, et al. Conventional technology of para-xylene producing has meet challenges since the decline of oil resources. So it's urgent to develop new efficient method for para-xylene. Para-xylene obtained by toluene alkylation with methanol alleviat the excess of methanol. It's a project of high practicability and promising market. It's necessary to research highly efficient catalysts for reaction of toluene alkylation with methanol. ZSM-5 is a widely used catalyst for the reaction, and catalytic performance is closely related to morphology, crystalline size, crystallinity, Si/Al, modification reagents, adding order of modification reagents of catalysts.Whether a technology applied in industry depend on its economic benefits. Firstly we adopted industrial reagents modified catalysts for the reaction of benzene alkylation with methanol. It was found that with modified steps increasing the conversion of toluene was dropping from 13.4% to 10.7%, while the selectivity of para-xylene was increasing from 33.2% to 87.7%. There is no significant difference in conversion of toluene on industrial reagents and analytical reagents modified catalysts, but selectivity of pare-xylene is little lower around 1%-4% on the former. Next, we applied Fe modified catalyst under a flow of N2 for the reaction to cut costs. Compared ferric nitrate, ferric citrate, ammonium ferric citrate modified catalysts. Catalytic performance of ferric nitrate modified catalysts is the best, while ammonium ferric citrate modified catalysts is the last. We found that utilization of methanol was very low for the reaction. Methanol is an active reactant, it tends to produce light hydrocarbon, so we studied the effect of crystalline size on the utilization of methanol. It revealed that with the increase of crystalline size the selectivity of para-xylene was dropping on both HZSM-5 and modified catalysts. When crystalline is 580 nm, the catalytic performance was superior, the more ration of methanol was used to produce pare-xylene, the less light hydrocarbon was produced.