One-pot synthesis of high silica MCM-22 zeolites and their performances in catalytic cracking of 1-butene to propene

MCM-22 zeolites with high SiO2/Al2O3 (Si/Al2) ratios were synthesized by a one-pot procedure with the assisting of boron. Based on this boron-containing method, the Si/Al2 ratios of the MCM-22 zeolites could be greatly extended from 30 to 600 in control by tuning the Si/Al2 ratios of the starting gels. ICP-AES and 11B MAS NMR results demonstrated that a small part of the boron still existed in the framework of the MCM-22 after calcination and ammonium exchange. However, the residual boron species had little influence on the physicochemical properties of the MCM-22 samples evidenced by XRD, BET, TG–DTA, NH3–TPD, and Py-IR determinations. The reaction of catalytic cracking of 1-butene to propene was carried out to study the performances of the high silica MCM-22 catalysts. Increasing of the Si/Al2 ratios in the MCM-22 zeolites suppressed the formation of byproducts such as propane and aromatics effectively, and the optimal selectivity towards propene was obtained on the sample with a Si/Al2 ratio of 158.