Study On Alkylation Of Benzene With Methanol Over Modified ZSM-5 Zeolite

P-xylene is the material bases of polyester fiber industry with humorous demand. The demand has an upward tendency. China, the world’s largest consumer of PX, is facing the contradiction between supply and demand of PX. As benzene and methanol are plentiful and cheap, it has great economic value to produce xylene and toluene which has high additional value by alkylation of benzene with methanol. It shows great promise for the future.According to this study, modified ZSM-5 zeolite was prepared and was applied to alkylation of benzene with methanol. ZSM-5 zeolite was modified by alkaline treatment, metal oxides loading and composite modification. The idea is to adjust structural channels to increase efficiency for mass transfer and selectivity, but also adjust acidity to improve pertinence of target reaction and to avoid isomerization of para-compound. The modified zeolites were characterized by XRD, SEM, FT-IR, nitrogen adsorption and NH3-TPD. The results showed HZSM-5 zeolite was still MFI structural characteristics with some meso-pore after alkaline treatment. Benzene conversion was 45.31% and xylene selectivity reached 31.06% while the total selectivity of xylene and toluene was 81.35%. Co3O4-La2O3/ZSM-5 kept good structure and morphology. Some strong acidic sites were covered with La2O3 in pore channel and a lot of acidic sites in the surface were covered by La2O3. Besides, Co3O4-La2O3 could increase channel curvature and contract bore. All is good at selectivity and catalytic activity. The total selectivity of toluene and xylene reaches 89.02%after the HZSM-5 was loaded with CO3O4 and La2O3, especially the selectivity touched 36.58%, which is an excellent performance. The specific gravity of PX was 60.7% in xylene.This paper studied conditions of alkylation of benzene with methanol over Co3O4-La2O3/ZSM-5 Zeolite. Research suggests that the best result comes at the temperature of 723K under the pressure of 0.1 Mpa when the feed is introduced as the ratio of 1:1 at a space velocity of 3h-1. The conversion of benzene was 51.36%, the total selectivity of toluene and xylene reached 90.66%, and the selectivity of xylene was 38.07%.