Kshudiram Mantri

Influence of zeolite factors affecting zeolitic acidity on the propane aromatization activity and selectivity of Ga/H-ZSM-5

Abstract The influence of zeolite factors, such as Ga loading (0–3%), Si/Al ratio (35–132), degree of H + exchange (2–98%) and calcination temperature (600–800°C), affecting zeolitic acidity on the activity and selectivity of Ga/H–ZSM-5 in the aromatization of propane has been investigated. The activity and selectivity in propane-to-aromatics conversion are found to be influenced strongly by the above zeolite factors. The aromatization activity and selectivity of the zeolite shows a close relationship with its strong acidity (measured in terms of pyridine chemisorbed at 400°C). The propane aromatization activity and selectivity increases sharply with the increase in the strong acid sites of the Ga/H–ZSM-5.

AlClx-grafted Si-MCM-41 prepared by reacting anhydrous AlCl3 with terminal Si-OH groups:an active solid catalyst for benzylation and acylation reactions

Abstract A liquid phase reaction between anhydrous AlCl3 and terminal Si–OH groups of mesoporous Si-MCM-41 in dry CCl4 results in a AlClx-grafted Si-MCM-41 (with Cl/Al ratio=1.43, Al(tetrahedral)/Al(octahedral)=ratio=0.84 and Al/Si ratio=0.17). This catalyst shows high catalytic activity in Friedel–Crafts type benzylation (by benzyl chloride) and acylation (by benzoyl chloride) of benzene and toluene.

Thermal Activation of a Clayzic Catalyst Useful for Friedel–Crafts Reactions: HCl Evolved with Creation of Active Sites in Different Thermal Treatments to ZnCl2/Mont-K10

Thermal activation of clayzic catalyst has been thoroughly investigated by calcining anhydrous ZnCl2 impregnated on Mont-K10 with different ZnCl2 loadings (0.5-2.0 mmol g-1) under static or flowing air at 270 °C and also under N2 flow at different temperatures (150-400 °C). Depending upon the ZnCl2 loading and calcination temperatures, an appreciable amount of HCl is evolved in the thermal activation, indicating an occurrence of reaction between the ZnCl2 and the surface hydroxyl groups of the clay (- OH + ZnCl2→ - O - Zn - Cl + HCl), leading to formation of new Lewis acid sites (- O - Zn -Cl). The Cl/Zn ratio, surface area and catalytic activity (in the benzene benzylation by benzyl chloride at 80 °C) of the clayzic formed in the thermal activation are influenced markedly by the ZnCl2 loading and calcination conditions (temperature and gas atmosphere). The maximum catalytic activity for the clayzic is observed at the optimum ZnCl2 loading (about 1.0 mmol g-1) and calcination temperature (about 270 °C). The thermal activation at 270 °C under flowing N2 led to a most active clayzic catalyst for the benzene benzylation. A temperature-programmed evolution of HCl in the calcination of ZnCl2/Mont-K10 with different ZnCl2 loadings from 25 to 400 °C at a linear heating rate of 2 °C min-1 has also been investigated.

Highly selective Si-MCM-41 supported InCl3, GaCl3, FeCl3 and ZnCl2 catalysts for low temperature esterification of tert-butanol by acetic anhydride

Abstract Si-MCM-41 supported InCl3, GaCl3, FeCl3 and ZnCl2 catalysts (metal chloride loading = 1.1 mmol g −1 ) have very small activity for the dehydration of tert-butanol and hence show very high selectivity (>99%) for the esterification of tert-butanol by acetic anhydride, producing acetic acid as a by-product, at ⩽50°C. The esterification activity of the supported metal chloride catalysts is in the following order: InCl3> GaCl3> ZnCl2> FeCl3.

Influence of catalyst binder on the acidity and activity/selectivity of Ga/H-ZSM-5 zeolite in propane aromatization

The acidity and initial and time-on-stream activity in propane aromatization (at 550°C, space velocity of 3100 cm3g−1(zeolite)h−1) of Ga-impregnated H-ZSM-5 zeolite without or with binders (50 wt%), such as silica, alumina and kaolin, have been investigated. Both the acidity and catalytic activity of the zeolite are influenced by the presence of binder in the catalyst, depending upon the binder. The influence is found to be lowest for alumina and highest for kaolin. Among the binders, alumina is the most preferred binder for the zeolite catalyst.