Synthesis, Characterization and Catalytic Performance of Well-ordered Crystalline Heteroatom Mesoporous MCM-41

The mesoporous heteroatom molecular sieve MCM-41 bulk crystals with the crystalline phase were synthesized via a one-step hydrothermal method using an ionic complex as template. The ionic complex template was formed by interaction between cetyltrimethylammonium ions and metal complex ion [M (EDTA)]2- (M=Co or Ni ). The materials were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, N2 adsorption–desorption isotherms, and X-ray absorption fine structure spectroscopy. The results showed that the materials possess a highly ordered mesoporous structure with the crystalline phase and possess high uniform ordered arrangement channels. The structure is in the vertical cross directions with a crystalline size of about 12 µm and high specific surface areas. The metal atoms were incorporated into the zeolite frameworks in the form of octahedral coordinate and have a uniform distribution in the materials. The amount of metal complexes formed by metal ion and EDTA is an essential factor for the formation of the vertical cross structure. Comparing to Si-MCM-41, the samples exhibited better conversion, higher selectivity for cumene cracking.

Preparation of Alumina Pillared Montmorillonite Clays Employing Ultrasonics and Their Catalytic Properties

<p>An accelerated diffusion of alumina precursor species in-between the gallery region of montmorillonite clays by the use of ultrasonic technique is described. This method offers a faster, efficient and attractive route for the synthesis of alumina-pillared clay catalysts. Out of the several preparative parameters studied, the role of pre-exchanged cations influenced the optimum duration of ultrasonic agitation and treatment for the pillaring process. By comparing ultrasonic route and conventional preparation procedure, it is revealed that uniform spacing of alumina pillars in the clay means homogeneously distributed acid centers. The influence of calcination temperature on the acidity and hence the catalytic activity is described. The choice of three different montmorillonite clays with different cation exchange capacities enables one to tune the pore dimensions of the pillared clays. The catalytic applications include studies on cumene cracking, dehydration of propan-2-ol and alkylation of benzene with linear olefins. </p>

Cubic and Hexagonal Mesoporous Aluminosilicates Assembled from Secondary Building Units Characteristic of Zeolite Beta

To improve the structure order and catalytic activity of mesoporous materials, cubic (SBU-MCM-48) and hexagonal (SBU-MCM-41) mesoporous aluminosilicates containing secondary building units characteristic of zeolite Beta have been prepared, and characterized by means of XRD, N2 adsorption, IR spectroscopy, catalytic cracking reaction compared with the corresponding MCM-41. We found that the introduction of secondary building units characteristic of zeolite Beta into the mesopore wall could be an effective route to improve the acidity of mesoporous materials. Moreover, cubic SBU-MCM-48 has been more active than hexagonal SBU-MCM-41 for cumene cracking reaction.

Friedel-Crafts Alkylation of o-xylene over V2O5 / ZrO2 Catalysts

The present study has undertaken the Friedel-Crafts benzylation of aromatics over the V2O5/ZrO2 catalysts systems. Catalysts with different V2O5 content (0-15wt %) was prepared by wet impregnation method and characterized by XRD, BET surface area, FTIR and 5’V NMR techniques. The surface acidic properties were determined by temperature programmed desorption of NH3, cumene cracking and perylene adsorption. Under the optimized reaction conditions, these catalysts are found to be very effective and considerably more selective than the conventional homogeneous Lewis acid catalysts. The investigation of vanadia systems-catalyzed benzylation of o-xylene with benzyl chloride revealed that the catalytic activity and product selectivity are sensitive to the precise reaction parameters and can be related to the Lewis acidity of the systems. The reaction is found to be very clean and produces the desired monoalkylated product with high yield.