Premium
Isolation, Characterization, and Identification of Catalytically Active Species in the MoO 3 /SiO 2 Catalyst during Solid Acid Catalyzed Reactions
Author(s) -
Kotbagi Trupti V.,
Biradar Ankush V.,
Umbarkar Shubhangi B.,
Dongare Mohan K.
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200662
Subject(s) - catalysis , chemistry , inorganic chemistry , acetic acid , mesoporous silica , desorption , ammonia , molybdenum , mesoporous material , adsorption , organic chemistry
We report the isolation, characterization, and identification of the catalytically active species formed during various acid‐catalyzed reactions if silica‐supported MoO 3 was used as a catalyst. We have reported previously the synthesis and extensive characterization of the silica‐supported MoO 3 catalyst prepared by the sol–gel process with ammonium heptamolybdate and ethyl silicate‐40 as molybdenum and silica precursors, respectively. The TEM images showed uniformly distributed MoO 3 nanoparticles on the high‐surface area mesoporous silica support and high acidity (0.9 mmol g −1 ) by using temperature‐programmed desorption of ammonia (NH 3 ‐TPD) analysis. This catalyst has already shown high activity for various acid‐catalyzed reactions. To understand the nature of catalytically active species formed during the reaction, the liquid‐phase esterification of acetic acid and ethanol was studied as a probe reaction with very high acid conversion (83 %) in 8 h. During esterification, the reaction mixture turned blue, which indicated a change in the nature of the catalyst under reaction conditions. These catalytically active species formed in the reaction mixture were isolated and extensively characterized by using FTIR, Raman, powder XRD, BET surface area, NH 3 ‐TPD, energy dispersive X‐ray, and TEM analysis. The characterization results revealed the in situ formation of silicomolybdic acid on the silica surface in the presence of water, which acts as catalytically active species responsible for the acid‐catalyzed reactions.