• V R Choudhary

      Articles written in Journal of Chemical Sciences

    • Influence of O2 and H2 pretreatments on acidity/acid strength distribution and acid functions of Ga/H-ZSM-5, H-GaMFI and H-GaAl MFI zeolites

      V R Choudhary A K Kinage C Sivadinarayana M Guisnet

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      H-gallosilicate (H-GaMFI), H-galloaluminosilicate (H-GaAlMFI) and Ga, impregnated H-ZSM-5 (Ga/H-ZSM-5) zeolites pretreated with O2 and H2 (at 600°C for 10 h) have been characterized for their acidity/acid strength distribution (by chemisorption and stepwise thermal desorption of pyridine from 100°–400°C) and also for their acid functions by acid catalysed reactions [viz. isooctane cracking (at 400°C) (for characterizing external acid sites) and toluene disproportionation (at 500°C) and methanol-to-aromatics conversion (400°C)] using a pulse microreactor. The catalysts were also characterized by XPS,29Si,27Al and71Ga MAS NMR. The acidity/acid strength distribution, activity in the acid catalyzed reactions, frame-work Si/Ga ratio and surface Ga/Si ratio of the zeolites are significantly affected by their pretreatment by O2 or H2.

    • Thermal, hydrothermal and acid-base stability of highly siliceous MCM-41 mesoporous material

      V R Choudhary S D Sansare

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      Influence of various thermal, hydrothermal and acid/base treatments on the structural stability of highly siliceous MCM-41 mesoporous material has been thoroughly investigated. It has good stability towards thermal treatment up to 650°C, hydrothermal treatment at low temperatures (⩽400°C), and concentrations of steam (⩽40 mol%), mechanical grinding and acid treatment (for 1 M HC1) but poor stability towards hydrothermal treatment with liquid water (even at 150°C) and base treatment, if it is dissolved in 0.1 M NaOH.

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