•Uniform intracrystalline mesopores were introduced in MCM-49 zeolite.•A CTAB micelle directed desilication mechanism was proposed.•The extra-framework aluminum of MCM-49 could be selectively removed.•The prepared hierarchical MCM-49 zeolite showed improved alkylation stability.Hierarchical MCM-49 zeolite with intracrystalline mesopores was prepared through post-treating the conventional MCM-49 zeolite in hexadecyltrimethylammonium bromide (CTAB) and NaOH mixed solution. N2 adsorption and desorption, XRD, TEM, XRF, ICP and Py-IR techniques were applied to characterize the obtained samples. It was found that uniform intracrystalline mesopores were distributed in the MCM-49 crystals, and the intracrystalline meso-porosity could be modified by changing the post-treatment conditions such as CTAB concentration, NaOH concentration, temperature and time. Based on the characterization results upon the hierarchical MCM-49 zeolite samples obtained by post-treating different time, the formation of intracrystalline mesopores in MCM-49 zeolite was proposed, which followed a CTAB micelle directed desilication mechanism. By virtue of the intracrystalline mesopores, the hierarchical MCM-49 zeolite prepared under proper post-treatment condition exhibited superior stability than the conventional MCM-49 zeolite in liquid alkylation of benzene with ethylene.

The interzeolite conversion of zeolite MCM-49 into zeolite ZSM-35 in “cyclohexylamine (CHA)–hexamethyleneimine (HMI)–Na2O–H2O” systems, consisting of “CHA–Na2O–H2O”, “HMI–Na2O–H2O” and “Na2O–H2O”, was investigated in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) characterization techniques. Both CHA and HMI play important roles in directing the interzeolite conversion of MCM-49 into ZSM-35, and the conversion speed is much faster in systems containing CHA than those containing HMI. Even in the Na2O–H2O system without any organic amine, MCM-49 can still transform into some other zeolites with more stable topological structures than itself, such as ZSM-35, ZSM-5, and mordenite, but the product of the interzeolite conversion is more complicated than that in the systems containing organic amines (CHA and/or HMI). In the Na2O–H2O system, alkalinity has been proved to be a crucial factor influencing the conversion trend of MCM-49. Zeolites ZSM-5 and mordenite will appear in the products besides ZSM-35 with the increase of the alkalinity. The conversion process of zeolite MCM-49 in the systems investigated accords well with the solution-mediated transformation mechanism.

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.

A novel route for synthesis of MCM-49/ZSM-35 composite zeolites with different compositions in a mixed amine system containing hexamethyleneimine (HMI) and cyclohexamine (CHA) has been developed. Furthermore, both MCM-49 zeolite and ZSM-35 zeolite can be successfully synthesized by adjusting the synthesis conditions in the same system. Especially, the MCM-49/ZSM-35 composites with more content of ZSM-35 zeolite can be produced under conditions of larger CHA/HMI molar ratio, higher Na2O/Al2O3 molar ratio and longer crystallization time. The structure characterization, acid distribution and morphology of the MCM-49/ZSM-35 composite zeolites are characterized by X-ray diffraction, N2 adsorption isotherms, NH3-TPD, scanning electron microscopy as well as HP-129Xe NMR technology. These characterizations give obvious different pore structure of the MCM-49/ZSM-35 composite zeolites from the mechanical mixing counterpart.