Project 5 is related to the catalytic conversion of sugars to provide useful chemicals at low cost.

The main focus of the project has been related to the use of a particular type of catalysts, namely zeolites, for the transformation of sugars. By studying the synthesis of the catalyst it was found that alkali metals have a profound impact on the shape of the crystals formed and in their catalytic performance. It has for instance been found that by adding just a few ppm of potassium carbonate, the selectivity of the catalyst increases for the formation of lactic acid derivatives from 25% to 75%. This surprising finding was further examined by the use of high-resolution NMR spectroscopy and the reaction pathways were found. It was found that the alkali ions alter the reaction pathway to increase the degree of retro-aldol reactions that takes place. This makes the C6 sugar convert more easily to two C3 sugars, thereby increasing the yield of lactic acid derivatives. Thus, activities in the project has helped to explain the reason for this effect.

In an up-scaled production run, approximately 100 kg of sugar was converted using this kind of catalyst, and alkali ions were added to benefit from this effect leading to higher yields of lactic acid derivatives. Following this, a study was carried out in the absence of added alkali ions which leads to the formation of new bio-based products that have not been reported before. Some of these products can be made from C5 sugars, which otherwise are difficult to utilize for the production of useful chemical building blocks.

In another study, the conversion of glycolaldehyde to useful chemicals were carried out. Several different ideas were tested, and it has been shown that by reaction using a shape-selective zeolite, C4 sugars can be formed in high yields from this substrate. These scientific findings have all been published in peer reviewed journals and presented at conferences.

Figure: cover page of ChemSusChem featuring Tolborg et al. (2016): Shape-selective Valorization of Biomass-derived Glycolaldehyde using Tin-containing Zeolites.