INTERACTION OF GLYCEROL WITH ACETONE IN THE PRESENCE OF ACID-MODIFIED CLINOPTILOLITE

Abstract

Despite its wide application in industry, the effective use of glycerol growing volumes is very relevant, since «technical» glycerol with an acceptably high content of main substance can become an available and promising raw material for obtaining valuable chemical compounds, in particular cyclic glycerol ketals. Glycerol reaction with acetone in the presence of acid-modified clinoptilolite (CLI) as a catalyst for formation of cyclic ketals was studied. It was found that technology of acid modification doesn’t significantly affect the acidity of catalyst. For samples prepared by first method, with increasing time of acid modification, pH suspensions increase, namely the acidity decreases. As for catalysts prepared by second method, no such tendency is observed. The influence of modification time CLI samples has different effects on activity of prepared catalysts with different diameters. For CLI with a larger diameter (dav. = 1.5 mm) a minimum of activity is observed with increasing modification time (τH), namely the dependence of glycerol conversion (ZGL) on τH is extreme. For CLI of smaller dav. (0.05 mm and 0.75 mm) change of this factor has little effect on their activity. Comparing catalysts with same τH, but different dav. and method of preparation, it can be noted that the activity of catalyst with a higher d av. is higher than in samples with less. At the same time, two catalysts of same dav. (0.05 mm), but different methods of preparation practically don’t differ in their catalytic properties. CLI belongs to sorbents with a heterogeneous porous structure, catalytic activity of which depends on acidity, pore structure, and availability for diffusion of reagents. By method of planning two series experiments, according to a complete three-factor analysis, adequate models were obtained, according to which the pH of suspension and d av. are factors that have little influence on response function – ZGL. A linear (sympathetic) dependence is observed between glycerol conversion and initial rate of its loss, which is characteristic for most «families» of studied acid-modified CLI samples.