Huihui Mao

Synthesis of mesoporous silica-pillared clay by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using quaternary ammonium surfactants as gallery templates

Mesoporous silica-pillared montmorillonite (MMT) materials were synthesized by intragallery ammonia-catalyzed hydrolysis tetraethoxysilane (TEOS). The reaction involved hydrolysis and condensation of tetraethoxysilane in the presence of intragallery surfactants templates. Powder X-ray diffraction (XRD), N(2) adsorption-desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infra-red (FT-IR) spectra were employed to characterize the mesoporous silica-pillared montmorillonite. These novel materials exhibited reflections corresponding to a basal spacing of 4.76-5.62 nm, a uniform pore size of 3.75-4.51 nm and large surface areas of 597.2-712.4 m(2)/g. And the porous structure and physical properties of silica-pillared montmorillonite derivatives remained stable after heating for 5 h at 700 degrees C in air. Our results indicate that surfactants play a decisive role in pore formation, because they act as micelle-like template during the hydrolysis of TEOS. These mesoporous silica-pillared montmorillonite materials exhibit excellent catalytic activity and selectivity for coker gas oil cracking reaction in comparison to normal MCM-41 and Al-MCM-41.

Synthesis of mesoporous zeolite Ni-MFI with high nickel contents by using the ionic complex [(C4H9)4N]2(+)[Ni(EDTA)]2- as a template.

Ni-MFI zeolites with high percentage of Ni (5-15 wt%) were prepared by using an ionic complex [(C(4)H(9))(4)N](2)(+)[Ni(EDTA)](2-) by one step synthesis. These molecular sieves were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), differential scanning calorimeter (DSC) and nitrogen adsorption-desorption isotherms. The results showed that heteroatom Ni was successfully introduced into the MFI framework up to 15 wt%. Moreover, this Ni-MFI possessed regular and stable structure with high specific surface area and average pore diameter of 388-439 m(2) g(-1) and 2.566-3.828 nm, respectively, compared to MFI prepared by traditional methods. These samples also showed good thermal and hydrothermal stability.

Restructuring of silica-pillared clay (SPC) through posthydrothermal treatment and application as phosphotungstic acid supports for cyclohexene oxidation.

A facile posthydrothermal treated process has been successfully established for restructuring of silica-pillared clay. This approach involves the hydrothermal treated process utilizing octadecylamine as structural agency followed by calcination at high temperatures. The formation of expanded interlayered mesopores is a result of treatment with octadecylamine hydrothermal conditions. The following calcination at higher temperatures gives silica-pillared clay larger pore volume and conserved high surface area. The kind of pore expansion process has been confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms and transmission electron microscopy (TEM). The pore expansion mechanism of silica-pillared clay is proposed. The pore expanded silica-pillared clay has been used as the catalytic supports for H3PW12O40 loading as high as 26.9%, 35.8% and 48.2% for oxidation reaction of cyclohexene using H2O2 as oxidant. The stable charge force between H3PW12O40 and negative charged clay layers, together with big and open porous structure, large pore volume, and high loading of H3PW12O40 contributes to the efficiency conversion, high selectivity toward cyclohexene epoxide and brilliant reusability.