(69e) Utilisation of Heterogeneous Catalysts for the Selective Synthesis of Di- and Triglycerol

Glycerol becomes more and more interesting because of the surplus arising from the biodiesel production. Thus the chemical industry looks for advanced utilisation of glycerol. Telomers could be used as surfactants whereas oxidation and carbonylation could lead to interesting chemicals via new catalytic pathways. In this contribution the focus is on the oligomerisation of glycerol. Di- and triglycerol, which are the main products, are of increasing interest especially for body care products or as starting materials for polyglycerol esters, which can be applied as emulsifiers. The following scheme shows the reactions taking place. Scheme 1: Oligomerisation of glycerol By today glycerol oligomers are produced homogeneously catalysed using alkali hydroxides as catalysts. Such catalysts reveal two big disadvantages. The first one is the fact that the catalyst is homogeneously solved in the reaction mixture. To get rid of the catalyst expensive separation steps have to be used, for example distillation. The second problem arising through utilisation of homogeneous catalysts is the product spectrum of the reaction. Short oligomers such as di- and triglycerol are of large interest whereas the utilisation of higher oligomers is not so interesting. The selectivity of homogeneous catalysts is by far too bad. This problem can be handled using heterogeneous catalysts. Their separation is easy and their selectivity towards di- and triglycerol is quite good. However, so far heterogeneous catalysts are not as active as homogeneous catalysts but much more selective. The presentation deals with the description of appropriate heterogeneous catalysts. Information is given about the conversions as well as the selectivity at optimum reaction conditions. Moreover, experiments under continuous conditions were performed and their results will also be shown.