Catalytic inulin conversions to biobased chemicals

Biomass is a valuable feed for the production of biofuels and biobased products. The development of efficient chemical processes for biomass conversion to biobased chemicals is high on the global research agenda. A number of promising chemicals from biomass have been identified and are known as platform chemicals. Bozell & Petersen (2010) compiled a list of 12 biobased chemicals that have the highest techno-economical potential. This top 12 list includes 5-hydroxymethylfurfural (HMF), which may be converted to versatile building blocks for polymers such as 1,6-hexanediol, 2,5-furandicarboxylic acid and fuel-additives such as 2,5-dimethylfuran.

HMF is typically obtained by reacting C6 sugars in water in the presence of a Brönsted acid. By-products of the reaction are levulinic acid (LA) and formic acid and insolubles known as humins. In water, d-fructose is the C6 sugar feed of choice and gives a maximum HMF yield of around 55 mol%, whereas the yields for d-glucose are less than 10 mol%.

However, economically viable processes for HMF have not been developed yet. Major improvements in product selectivity and yield are required. This should not lead to high costs related to, for instance, expensive catalyst and solvent recycles. In addition, there is a high incentive to use cheap biomass feeds, preferably with a high amount of d-fructose units to obtain good HMF yields.

In this thesis, the use of inulin as a carbohydrate biomass feed for HMF synthesis has been explored. Inulin is a biopolymer mainly consisting of d-fructose and minor amounts of glucose and as such is an attractive biopolymer for the synthesis of HMF. The molecular weight of inulin is by far less than typical biopolymers like cellulose, hemicellulose and starch. Degrees of polymerisation between 2 and 70 have been reported. Inulin is present in Jerusalem artichoke tubers, Chicory roots, Camas bulbs and Dahlia tubers in amounts of around 20 wt% on fresh weight.

The emphasis has been on water as the solvent as it is environmentally benign and most carbohydrates and products have a good solubility in water. A range of catalysts has been explored, examples are cheap inorganic Brönsted acids and metal salts. In addition, the reaction in the absence of a catalyst has also been explored.

Dissertation: http://hdl.handle.net/11370/75d61c3c-070e-43cf-91a4-1869baf7fbe9