Jinghong Ma

Synthesis and characterization of ordered mesoporous zeolite LTA with high ion exchange ability

An ordered mesoporous zeolite LTA is prepared by using organofunctionalized silica as Si-source. The mesoporous zeolite LTA has nano-cages of 3 nm interconnected to each other through 0.8–1.2 nm channels. A Jacobsen salen complex can be encapsulated successfully in the supercages of the zeolite. 29Si, 27Al-MAS NMR and in situFT-IR spectra reveal a new crystallization mechanism. The mesostructure and nano-supercages in the zeolite result from the bond-blocking action during the crystal growth. The zeolite has connatural micropore and ordered mesopore systems within the zeolite particles. The mesoporosity of the mesoporous zeolite can be rationally controlled by the degree of silanizing. The diffusion rate of hydrated Mg2+ in the synthesized submesoporous zeolite is 170 times higher than in a traditional zeolite at 308 K.

De novo assembly of a mesoporous beta zeolite with intracrystalline channels and its catalytic performance for biodiesel production

A mesoporous beta zeolite was hydrothermally prepared directly by silanizing silica without any mesoporous template via the bond-blocking principle. Si–C bond-blocking arose during the crystalline growth. The crystallization took more than 10 days, but the material had a fairly stable structure and could even be processed up to 32 days later in the hydrothermal system. XRD, N2-adsorption/desorption and TEM/SEM characterization of the materials indicated that the beta zeolite is truly a sponge-like mesoporous zeolite with a BEA topological structure, which consists of self-sustaining macroscopic sized zeolitic aggregates assembled from nanosized crystalline domains of beta zeolite with intracrystalline mesopores. The mesoporous beta zeolite possessed an extremely large external surface area and adjustable mesoporosity. Compared to conventional beta zeolite, FTIR results of pyridine (Py) and 2,6-di-tert-butylpyridine (DTBPy) demonstrated an increase of the Lewis-site contribution and a large improvement for the accessibility of bulky molecules in the mesoporous beta zeolite. Finally the mesoporous beta zeolite exhibited significant activity in the transesterification reaction of triolein to afford methyl oleate (biodiesel) due to the accessibility increase and diffusion-limitation reduction of large lipids to acid sites in the H-beta zeolite framework.

Availability and interconnectivity of pores in mesostructured ZSM-5 zeolites by the adsorption and diffusion of mesitylene

Probing the mesopore architecture in mesoporous zeolites is of importance for large scale applications of the materials. In this work, the adsorption and diffusion of mesitylene with larger molecule size in mesoporous ZSM-5 zeolites were carried out, in order to acquaint the availability and interconnectivity of mesopores in zeolite crystals. The comparisons of the shape of adsorption isotherms and the mesopore volume calculated from mesitylene and N2 adsorption in mesoporous ZSM-5 zeolites with different mesoporosities can be used to discriminate two cases of mesopores: accessible mesopores connected to external surface of the zeolite crystals and non-accessible meso-voids that are occluded in the microporous matrix. Furthermore, the effective diffusivity and activation energy of mesitylene in mesoporous ZSM-5 extracted from ZLC desorption curves as a function of mesopore volume calculated from mesitylene adsorption reveal the enhancement of mesopore interconnectivity to molecule diffusion in zeolite crystals.

Acidity and hydrogenation performance of Beta zeolite aluminated by Na2AlO2 solution

Abstract Zeolite HBeta was treated by an aqueous solution of NaAlO2 and characterized by XRD, N2 adsorption, IR framework vibration, 29Si MAS NMR spectra and benzene adsorption. The results revealed the zeolite HBeta retained its parent structure after alumination. FTIR spectra of silanol groups and adsorbed pyridine showed that the treatment increased the number of both Bronsted and Lewis acid sites in the aluminated zeolite. Both the insertion of Al species into the framework occupying the structural vacancies and the isomorphic substitution of framework Si(0Al) sites by Al ions during the treatment, resulted in decrease of the Si/Al ratio in the zeolitic frameworks. The Ru catalysts supported on the aluminated zeolite indicated higher benzene hydrogenation activity than on parent HBeta, due to the high acidity in the aluminated zeolite.

Synthesis and characterization of zeolitic composite ZSM-5/MOR with multi-modal pores

Abstract ZSM-5/MOR zeolitic composite was prepared by a two-step synthetic route and characterized by SEM, N 2 adsorption and NH 3 -TPD. The results showed the composite has different acid property and multi-modal pore structure from the physical mixture of two zeolites, and a strong acid center is formed in the composite. In the catalytic cracking reaction of n-octane, the composite ZSM-5/MOR has higher conversion and longer life than their physical mixture.