Study On Amylation Of Benzene With Isopentene Over Zeolite Catalysts

tert-Amylbenzene (t-AB) is an important intermediate chemical in the production of 2-amylanthraquinon (AMQ) which serves as an efficient working solution in the manufacture of H₂O₂. The conventional manufacturing methods for t-AB are based on two kinds of catalytic reactions. One is the Friedel-Crafts alkylation of benzene with 2-methyl-2-butene catalyzed by homogeneous catalysts such as H₂SO₄, AlCl₃, and FeCl₂ etc. The other is the side-chain alkylation of cumene or ethylene performed on the solid base catalysts such as alkali metals and alkali metal hydrides. Both methods suffer the problems such as hard handling, danger, corrosion, and waste disposal, thus becoming a bottleneck restraining its wide application.Zeolites have been applied successfully to the commercial processes for the clean production of alkylbenzenes such as cumene and ethylbenzene. Analogously, it is desirable to develop zeolite-based innovative, green and heterogeneous chemical process for t-AB synthesis via benzene alkylation.We communicate here for the first time the catalytic properties and product distribution of benzene alkylation with isopentene over zeolite catalysts. The major results are as follows:(1) Catalytic activity and product selectivity among ZSM-5, USY, Beta and MWW series zeolites are compared here. The results show that large-pore zeolites of 12-membered ring (MR) have been found to be promising catalysts for the selective formation of t-AB. Beta zeolite appears to be the most efficient catalysts with high alkylation reacivity.(2) The influence of temperature, Benzene/C₅⁼ molar ratio, time on stream (TOS), and contact time (Ï„) on the performance of Beta catalysts were investigated to achieve a better alkylation condition: WHSV, 36h^-1; B/C₅⁼, 30; Temp., 175℃; Pressure, 3.5MPa. Otherwise, the results help to comprehend how the reactions going on.(3) Zeolites Beta with various Si/Al ratio and phosphorus modified are characterized by XRD, IR, NH₃-TPD, ICP and BET measurements. Their catalytic activity of benzene alkylation shows that increase of framework Al content producesan slight increase in both conversion and selectivity in amylbenzene synthesis. Phosphorus impregnation of Beta would reduce its isomerization at higher temperature. Appropriate acid strength and enough acid sites are essential for the benzene alkylation.(4) Based on the above findings and plenty of literature research, a major alkylation mechanism has been clarified to understand the complicated reaction pathways.