Surface properties and catalytic behavior of MoO₃/SiO₂ in esterification of acetic acid with ethanol

Abstract

A series of MoO 3 /SiO 2 catalysts was prepared by an impregnation method with Mo loadings ranging from 1 to 50 wt%. The original and calcined samples at 400• C were characterized by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, and nitrogen adsorption measurements. The surface acidity and basicity of the catalysts were investigated by the dehydration-dehydrogenation of isopropanol and the chemisorption of pyridine. The catalytic esterification of acetic acid with ethanol was carried out at 220• C in a conventional fixed-bed reactor at 1 atm using air as a carrier gas. The results clearly revealed that silica-molybdena catalysts were active and selective towards the formation of ethyl acetate. Moreover, the catalyst containing 20 wt% MoO 3 was the most active and selective one. The results emphasize the importance of the surface acid sites together with the specific surface area of the prepared catalyst, towards ester formation.

Catalyst Development for the Synthesis of Ozonides and Tetraoxanes Under Heterogeneous Conditions: Disclosure of an Unprecedented Class of Fungicides for Agricultural Application

“…This may be due to the low content of formed MoO 3 in PMA/SiO 2 ‐(E) and due to a finely dispersed, small particulate molybdenum oxide structure. According to XRD literature data the most intense diffraction patterns from crystalline molybdenum oxide become noticeable when the Mo loading level of MoO 3 on SiO 2 is increased to 20 wt %.…”

Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silica

“…Measurements of the conversion and yield (%) were recorded after 2h from the initial introduction of the reactants into the reactor to ensure the attainment of the reaction equilibrium, (steady state conditions). that the silica precursor 16,17 loses weight with heating from ambient temperature to 600 • C. This weight loss, which was accompanied by a broad band on the DTA curve peaking at 80 • C, can be attributed to the physically adsorbed water. Above 400 • C and up to 600 • C a little weight loss was observed.…”

“…This means that the proton (Brønsted acid site) is not a major selective site towards the production of ester. 16 In contrast with Brønsted acids, Lewis acids in the catalyst support give very different results. This is evidenced by the continuous decrease in catalyst selectivities when PWA loading exceeds 10% w/w.…”

Introduction to the Special Issue: JTRES 2009

“…Figure 1 shows TG and DTA curves of the pure silica, pure PWA and PWA supported on silica. It is seen that the silica precursor16, 17 loses weight with heating from ambient temperature to 600 °C. This weight loss, which was accompanied by a broad band on the DTA curve peaking at 80 °C, can be attributed to the physically adsorbed water.…”

“…To overcome this problem, gas‐phase reactions may be one alternative method. Recently, we have reported that the gas‐phase reaction of acetic acid with ethyl alcohol on supported metal oxides13–16 and phosphomolybdic acid17 showed good results towards ester formation. The main advantages of this method are the possibility of regeneration of the catalysts and reduction of the environmental impact.…”