Catalytic Routes to Renewable Polymer Building Blocks

Abstract

This PhD thesis is entitled “Catalytic Routes to Renewable Polymer Building Blocks – and renewable chemicals from biomass” and focuses on future challenges related to alternative energy sources, materials and the environment. Current concerns about fossil fuel depletion and rising global warming have sparked a profound research effort toward the development of alternative renewable and carbon neutral technologies. Despite heavy research activities within these areas, still only few technologies within e.g. renewable chemicals have been implemented on an industrial scale. The work presented herein describes an alternative chemical platform for the production of chemicals derived from a biomass origin and suited for substitution of the current petrochemicals. The molecule 5-hydroxymethylfurfural (HMF) has been identified as a possible platform chemical for the production of numerous industrially valuable bio-based chemicals. Especially interesting are oxidized derivatives of HMF, which are suited for polymer production. HMF is derived from the consecutive dehydration of hexose sugars, a process that has been known for years, however still no industrial production methods are able to compete with today’s petrochemicals. The thesis is divided into two main sections; HMF synthesis and synthesis of valuable derivatives from HMF. Three methods for producing HMF were developed during this PhD study and are shown in chapter 2. The first method relies on the power of microwaves for efficient control of the reaction parameters in the aqueous dehydration of fructose to HMF. The second method draws advantage of the synergy between boric acid and salts for the promotion of HMF synthesis from aqueous fructose, glucose and sucrose solutions. The third method uses only salts and the inherent promoting effect of hot saline solutions on the dehydration of aqueous fructose and mixed fructose/glucose solutions. Two methods for the oxidation of HMF to 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDA), respectively, were also developed during this PhD study and are shown in chapter 3. The first method is a modification of an existing oxidation protocol relying on CuCl and (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) radicals for the oxidation of alcohols to aldehydes. The protocol has been modified to afford excellent DFF yields and to proceed with high selectivity toward DFF in previously non-suited solvents by introducing nitrogen containing promoters (NCPs). In the second slightly different protocol, HMF is oxidized to FDA by a combination of CuCl and tert-butyl hydroperoxide. Although the scope of this thesis was to develop polymer building blocks a leap into alternative fuels production is rounding-off this thesis with the synthesis of 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) from HMF.