Selective etherification of glycerol to polyglycerols over impregnated basic MCM-41 type mesoporous catalysts

In the general context of the development of the use of agricultural products for non-food applications, and particularly in the field of the glycerol valorisation (co-product of the triglycerides hydrolysis or methanolysis process), the selective etherification of glycerol was studied. The objective of this work is the direct and selective synthesis, from glycerol and without solvent, of polyglycerols having a low polymerisation degree (di- and/or triglycerol), in the presence of solid mesoporous catalysts. The main part of this study consists in the synthesis and the impregnation of mesoporous solids with different basic elements in order to make them active, selective and stable for the target reaction. The catalytic results obtained show that this impregnation method gives important activity, which must be correlated to an important active species incorporation. Concerning the selectivity of the modified mesoporous catalysts, the best value to (di- + tri-) glycerol are obtained over solids prepared by caesium impregnation. The re-use of these caesium impregnated catalysts does not affect the selectivity to the (di- + tri-) glycerol fraction. In the presence of lanthanum or magnesium containing catalysts, the glycerol dehydration to acrolein is very significant whereas this unwanted product is not formed when caesium is used as impregnation promoter, (C) 2002 Elsevier Science B.V. All rights reserved.