THE MECHANISM OF DEPOLYMERIZATION OF PARALDEHYDE CATALYZED BY SOME MIXED OXIDE CATALYSTS

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Pore opening size alteration of zeolite and its alkylation activity stabilization by coking

319-323<span style="font-size:11.0pt;line-height: 115%;font-family:Calibri;mso-fareast-font-family:" dejavu="" sans";mso-bidi-font-family:="" mangal;color:#00000a;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">Medium pore, ZSM-5 zeolite was subjected to chemical vapour deposition to alter its pore opening size. The extent of alteration and its effect on shape selectivity during toluene ethylation has been investigated. The time on stream behaviour of the pore size altered zeolite showed a deactivating trend with enhancement in hours on stream. The stabilization of the alkylation activity of the catalyst has been achieved by controlled coking and the details are discussed.</span

The effect of cyclic dealumination on the catalytic activity of beta zeolite

690-692The acidity of zeolite beta is decreased by dealumination with (NH4)2SiF6 The effect of change in zeolite acidity on catalytic activity for benzene isopropylation has been studied. The reasons for change in the product pattern over zeolite beta dealuminated cyclically have been discussed. The cyclic dealumination of zeolite beta can be effectively used to achieve a predesired product pattern of benzene isopropylation

Alkaline hydrolysis of poly(ethylene terephthalate) in presence of a phase transfer catalyst

173-177Poly(ethylene terephthalate) (PET) powder was hydrolyzed at atmospheric pressure in 5-10 wt% aqueous NaOH at 95°C for 100 min using some phase transfer catalysts (PTC) with an intention to recover the starting monomers from the waste PET. The intent behind attempting new PTC was to carry out the reaction at milder conditions than those reported in the literature. One of the monomers, terephthalic acid (TPA) was produced in the presence of a PTC during the alkaline hydrolysis of PET. The TPA yield agreed with the degree of hydrolysis of PET. Benzalkonium chloride (BKC) was found to be the most effective catalyst among the ones studied. Operating parameters such as NaOH concentration, catalyst concentration and reaction temperature were optimized

Kinetics of toluene alkylation with methanol on HZSM-8 zeolite catalyst

A detailed kinetic study of the alkylation of toluene with methanol on HZSM-8 zeolite was carried out in a fixed bed reactor. The catalyst showed high activity, selectivity, and stability. An attempt has been made to relate the overall changes taking place during the reaction. The experimental data are analyzed, and a reaction mechanism proposed based on the product pattern. The Langmuir-Hinshelwood-Hougen-Watson model with dual-site mechanism was used to derive the rate equation. The unknown parameters in the rate equations are estimated by a nonlinear regression method. The kinetic model based on the proposed reaction mechanism has predicted the conversion values, which are in close agreement with the experimentally observed values

Kinetics of ethylacetate hydrolysis on mordenite

881-885Liquid phase hydrolysis of ethylacetate on mordenite catalyst has been studied. The performance of this zeolite is compared with ion exchange resin, other zeolite like H-Y, H-ZSM-5 and conventional catalyst used in homogeneous phase, viz., HCl. Attempts have been made to use mordenite repeatedly after reactivating it. Based on estimated activation energy and related thermodynamic parameters, Si/Al ratio effect and zeolite acidity, the observed results have been explained

Application of the thermo-gas-titrimetric technique for the estimation of ammonia content in ammonium exchanged zeolites

The application of the thermo-gas-titrimetric (TGT) technique for estimating the ammonia content in ammonium X-, Y- and L-type zeolites is described. The values of ammonia content in different zeolites determined by the TGT method are in good agreement with those obtained by other conventional methods. The use of the TGT method enables one to distinguish between the ammonium ions physically adsorbed and those exchanged by the zeolite. The details of this method and its specific advantage are described in detail