Microwave-assisted synthesis of solketal from glycerol and acetone in the presence of SAPO-34 and SAPO-5

Solketal is one of the most promising additives improving the properties of motor fuels. Investigations related to process intensification of synthesis of solketal from glycerol and acetone is gaining importance. The present work illustrates the use of the microwave mode for intensification of this process in the presence of silicoaluminophosphates (SAPO) as catalysts. The main focus of the study was placed on tuning the textural, acidic, and catalytic properties of SAPO-34 and SAPO-5 via variation of the synthesis parameters, such as the nature of Al and Si sources and the structure-directing agent. The catalytic properties of SAPO materials were investigated in the synthesis of solketal from glycerol and acetone under microwave assistance at the acetone/glycerol molar ratio of 2.4 in a methanol solution (glycerol/methanol: 1 g/1 mL) and 56 °C. It was demonstrated that the selectivity towards solketal was 91.1–98.6 % in the presence of the studied materials. The activities of mesoporous SAPO-34 and SAPO-5 prepared in the presence of triethylamine were higher as compared with microporous SAPO-34 prepared in the presence of tetraethylammonium hydroxide due to the high mesoporosity and a larger content of acid sites. The 90.4 % conversion of glycerol and 98.6 % selectivity towards solketal were observed in the presence of mesoporous 7.6%SAPO-34 for 90 min. The advantage of using microwave technology is shown. The solketal yield in the reaction under microwave irradiation was 3 times higher than that in the process performed under thermal heating conditions.