Investigation of a molybdenum-containing silica catalyst synthesized by the sol–gel process in heterogeneous catalytic esterification reactions using methanol and ethanol

Molybdenum-containing silica easily synthesized by the sol–gel process was evaluated as catalyst for heterogeneous esterification reaction of fatty acids using methanol and ethanol. The molybdenum content depended on the conditions employed during the synthesis. The solids were characterized by X-ray powder diffraction, textural analysis, X-ray photoelectronic spectroscopy, and inductively coupled plasma optical emission spectroscopy. The strength and distribution of the acid sites were assessed by the adsorption–desorption of n-butylamine as monitored by Fourier transform infrared spectroscopy and thermogravimetric analysis. Kinetic studies revealed high fatty acid conversion for both alcohols and diminished activity upon decreasing concentration of acid sites. Monitoring of the acid sites during the recycling experiments indicated association of the catalytic activity with Mo oxide species on the surface and with the availability of molybdenum-active sites displaying Brønsted–Lowry acidity in the silica structure.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Preparation of solid catalyst based on Mo-containing silica by the sol–gel process. ► Catalyst based on Mo-containing silica for heterogeneous esterification reaction. ► Fatty acids catalytic heterogeneous esterification reaction using CH3OH and CH3CH2OH. ► Activity is associated with Mo atoms sites displaying Brønsted acidity in the silica. ► Catalyst with efficiency and recyclability capacity.