Zeolites are a large group of silicate minerals that contain some Aluminum atoms and are known for their ability to remove hardness from water.zeolite hy This is accomplished by trapping calcium and magnesium salts in the pores of the zeolite.zeolite hy Once the ions are trapped, they are easy to remove and the hardness of the water is reduced. Zeolites are also used for a number of other applications including the removal of toxins and the treatment of wastewater.
Alkylation is a chemical reaction that converts saturated hydrocarbons to unsaturated hydrocarbons.zeolite hy The catalysts used in this reaction are usually solid acids and the activity of the catalyst is closely related to its acidity and surface area.zeolite hy Moreover, the pore structure and structure of the catalyst is also important as it affects the selectivity of the reaction.
In order to improve the performance of existing alkylation catalysts, we have developed a new type of zeolite hy that has excellent catalytic activity for this reaction.zeolite hy zeolite hy The zeolite was prepared by treating a sodium form of the zeolite with ammonium chloride at a temperature of 80degC for 2 h, followed by calcination at 550degC to give the hydrogen form of the zeolite. The zeolite was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and TG/DTG.
The zeolite was found to be highly active in the alkylation of naphthalene and a-tetradecene at 100degC.zeolite hy The optimum amount of the zeolite used for this reaction was 5 mol% and the yield of the desired product was 63%.zeolite hy This result is much higher than the activity of other solid acid catalysts such as clay and sulfated zirconia.
This work also demonstrates that the high N2 activation ability of the zeolite is due to its cooperation between multiple molybdenum sites.zeolite hy This was evidenced by the N cleavage observed in the FT-EXAFS spectra, where two peaks were observed indicating the presence of the molybdenum cluster.
The angstrom-size Mo metal cluster on HY was converted from a hexanuclear molecular halide complex through impregnation and activation with H2.zeolite hy The size of the Mo cluster was preserved after H2-activation, despite the loss of halide ligands. Moreover, the XAFS and FT-EXAFS spectra showed that the angstrom-size Mo cluster was located on the surface of HY, which is consistent with the model based on cooperation of multiple molybdenum sites. This supported hexanuclear Mo cluster is an efficient catalyst for ammonia synthesis. The Mo cluster can effectively cleave the N-N bond in the gaseous state by leveraging its coordination with the silanols of HY. This is the first report on the formation of a supported angstrom-size Mo metal cluster on porous supports with high N2 activation ability. The results suggest that the HY molecule can be an effective support for the formation of molybdenum-based octanuclear clusters and provide an approach to the development of high-performance ammonia synthesis catalysts.
Tags:beta zeolite
