We report here a strategy for the facile synthesis of hierarchical MFI zeolite nanocrystals with controllable inter-crystalline mesopores by a one-step hydrothermal synthesis method using silica gel as the silica source and tetrapropyl ammonium as the microporous template without any other mesoporous templates or zeolite seeds. Powder X-ray diffraction results show the MFI structure with high crystallinity for all as-prepared zeolites. Scanning electron microscope characterization shows that 400–1000 nm zeolite aggregates are composed of the assembly of ~100 nm zeolite nanocrystals. Transmission electron microscopy results indicate the formation of inter-crystalline mesopores in the aggregated nanocrystals among the interspace of zeolite nanocrystals. The high mesopore volume (0.13 cm3 g−1) and external surface area (93 cm2 g−1) of the aggregated MFI zeolites are observed by N2 sorption measurements. The inter-crystalline porosity of MFI zeolites varies with the change in aggregation and the size of zeolite nanocrystals by changing the sodium concentration or the type of sodium salt in aluminate–silicate gels during hydrothermal crystallization. The mesoporous MFI zeolite aggregates exhibit similar light olefin selectivities and remarkably enhanced lifetime in the catalytic cracking of hexane compared to the highly dispersed MFI zeolite nanocrystals.

A facile and eco-friendly approach for the synthesis of mesopore-containing ZSM-5 zeolite with small crystal size was proposed by subtly making use of a coke-deposited spent zeolite catalyst. When used in the methanol to propylene reaction again, the refabricated ZSM-5 catalyst exhibited a much higher propylene selectivity and a longer catalytic lifetime.

A seeded approach was developed to synthesize high-silica EU-1 zeolite via inhibiting the co-crystallization of ZSM-48 in the presence of hexamethonium (HM) ions. A systematic study was carried out to determine factors such as seed content and SiO2/Al2O3 ratio, which influenced the crystallization of high-silica EU-1 and transformation of EU-1 into ZSM-48. Using EU-1 seeds, not only well-crystallized pure EU-1 zeolites with SiO2/Al2O3 ratios more than 500 were synthesized, but also the co-crystalline of ZSM-48/EU-1 or pure ZSM-48 was obtained in control from silica-rich mixture gels. Furthermore, the kinetic features of the seeded synthesis of EU-1 zeolites with SiO2/Al2O3 ratios of 55, 190, and 500 were examined. It was found that seeds played crucial roles in the decrease of apparent activation energy of EU-1 nucleation and inhibiting the transformation of EU-1 into ZSM-48. The HM and Al species performed synergistic roles to inhibit the formation ZSM-48 during high-silica EU-1 nucleation and crystal growth.Graphical abstractBy seeded approach, pure EU-1 with SiO2/Al2O3 > 240 were synthesized in HM system and the co-crystalline of ZSM-48/EU-1 or pure ZSM-48 was also tunable.Highlights► A seeded approach to synthesize of very high-silica EU-1 in HM system. ► Control of high- silica EU-1, co-crystalline of ZSM-48/EU-1 and ZSM-48. ► Role of seeds to reduce the Ea of EU-1 nucleation and inhibit ZSM-48 phase. ► HM and Al from seeds performed synergy in the crystallization of silica-rich gels.

A novel micro- and mesoporous composite molecular sieve (denoted as LMC) was synthesized by using the nanocrystal clusters of zeolite L as the precursor and a cation surfactant cetyltrimethylammonium bromide (CTAB) as the template. The physicochemical properties of samples were characterized by means of X-ray diffraction (XRD), nitrogen-adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared spectroscopy (FTIR), and Fourier transform infrared spectroscopy of pyridine adsorption (Py-FTIR). The results showed that composite molecular sieve LMC was synthesized by the self-assembly of zeolite L nanocrystal clusters under the template effect of CTAB. In addition, surface area, pore volume, and pore size of LMC significantly increased in comparison to those of conventional microporous zeolite L. The results measured by Py-FTIR showed that LMC had an appropriate acid amount and acid distribution. For evaluation of fluid catalytic cracking (FCC) gasoline hydrodesulfurization (HDS), the catalyst that introduced material LMC exhibited the excellent performances of desulfurization, isomerization, aromatization, olefin retention, and preserving the research octane number (RON) value compared to the catalyst that introduced ordinary microporous zeolite L or mesoporous Al-MCM-41 and used bare alumina as the support. The excellent catalytic performances of the catalyst should be attributed to the appropriate acidity distribution and open pore structure of material LMC.

This paper presents the direct synthesis of super-low SiO2/Al2O3 ratio zeolite beta molecular sieve through a novel route, by which some of aluminium species are added during crystaling process. The IR results show that with the increase of aluminium content in the framework, the frequency of the band in the range of framework vibration (1060–1090 cm−1) shifts to the lower wave-number; the BET surface-area decreases and the basicity of zeolite becomes stronger. In a second step, new adsorbents were obtained by solid-state ion exchanging zeolite beta with Cu(I), Ag(I) cations. The deep-desulfurization (sulfur levels of <1 ppmw) tests were performed using fixed-bed adsorption technique, the sulfur content of the treated and untreated gasoline was analyzed by microcoulometry. The experimental results show that the desulfurization performance of sorbents decreases in order: Cu(I)beta > Ag(I)beta > Na-beta. The best sorbent, Cu(I)beta, has breakthrough adsorption capacities of 0.236 mmolS/g of sorbent for model gasoline.

Ferrierite (FER) zeolites were synthesized by solid transformation at different alkalinities (OH−/Al2O3 molar ratios). The in situ delamination of FER zeolites were achieved and their catalytic performances in the catalytic cracking of C4 hydrocarbons were examined. The relationships among the OH−/Al2O3 molar ratio, FER structure, composition, surface acidity and catalytic performance in C4 hydrocarbon cracking were investigated. The results of X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, N2 adsorption, NH3 temperature-programmed desorption and catalytic cracking showed that with increasing OH−/Al2O3 molar ratio in the synthesis gel, the SiO2/Al2O3 molar ratio of the as-synthesized FER zeolite decreased, the amount of acid sites in the corresponding H-FER increased, and the acid strength weakened. Additionally, the FER zeolite was delaminated at the mesoscale. H-FER5 synthesized at the highest alkalinity had the largest number of acid sites and exhibited the highest catalytic activity in C4 hydrocarbon catalytic cracking among three of the prepared catalysts. H-FER3 synthesized at the second-highest alkalinity showed that the highest yield of benzene and toluene because of the secondary pores resulted from the gaps between the layers, which were beneficial to the diffusion and formation of large molecules.FER zeolites were synthesized using a solid-transformation method. The in situ delamination of FER zeolites at the mesoscale was achieved by adjusting the alkalinity of the synthesis gel (OH−/Al2O3 molar ratio). The FER catalysts delaminated at the mesoscale showed some of the characteristics of those delaminated at the microscale: they promoted the diffusion and formation of large molecules. This is a novel method for in situ modification of layered zeolites.Download full-size image