Green heterogeneous catalysts for cleaner solvent-free production of acetates

Abstract

AbstractThe development of new chemical synthetic methodologies that transform industrial chemical processes into more sustainable ones, constitutes one of the challenges and objectives of chemical research both in academia and in industry. The use of activated carbons as heterogeneous catalysts represents one of the most beneficial options for process efficiency in terms of reaction rate, yield, and ease of work-up. We have produced six new activated carbons by treatment of three affordable commercial carbons with either nitric acid, or with sulfuric acid. The complete characterization of these nine activated carbons has been carried out through the measurement of nitrogen adsorption capacity, porosimetry, elemental organic analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and determination of the point of zero charge; transmission electron microscopy was also performed on two of them. The catalytic activity of these nine catalysts has been tested in the acetylation reaction of hydroxyl groups, undoubtedly one of the most versatile and widely used chemical transformations both at the laboratory and industrial scale. The results show that by means of a simple and affordable modification of commercial xerogel with sulfuric acid, a more efficient catalyst is formed. Acetylation with the best catalyst is completed in 90 min at room temperature and the product is easily isolated in quantitative yield. The system can be reutilized for five runs with only a small loss of catalytic activity.