Biomass to chemicals: process design and kinetic studies for the conversion of sugars into 5-hydroxymethylfurfural

Abstract

Biomass is an abundant resource that represents a promising, renewable, alternative for the production of fuels and chemicals. In this context, the concept of biorefinery has emerged as the future substitute of the petroleum refinery. Its economic viability will largely depend on integrating the production of biofuels with high-value chemicals. Hence, considerable research effort is devoted to the development of laboratory scale strategies to obtain chemicals from biomass. Systems-type analyses ranging from techno-economic studies to the development of kinetic models are required to evaluate the different process alternatives, and these are the focus of this thesis.In the first part, the production of 5-hydroxymethylfurfural (HMF), a sugar-derived furanic compound that acts as a precursor of building blocks for polymers, is addressed. Two flowsheets for the production of HMF from fructose were developed and evaluated. Rigorous material balances and kinetics, coupled with mathematical optimization were used to calculate the minimum price at which HMF has to be sold in order to balance raw materials (fructose), energy and capital costs. Sensitivity analysis was performed to evaluate the effect of relevant parameters. Based on these, advances that are required to reduce HMF production costs were identified and experimental research directions proposed.The second part of the thesis studies of the isomerization of glucose into fructose using tin containing zeolites (Sn-beta). This step, traditionally done with enzymes, is known to account for a substantial portion of fructose cost, thus alternative processes have the potential to reduce the production costs of sugar-derived molecules. Analysis of preliminary experimental data showed that the conventional kinetic model developed for the enzyme catalyzed reaction breaks down when the reaction is catalyzed by Sn-beta. Motivated by this, a plan that combines design of experiments, modeling and parameter estimation was proposed to elucidate the mechanism. It was found that the catalyst deactivates and that formation of by-products cannot be neglected. A phenomenological model that describes the isomerization reaction in the presence of deactivation was developed, and the corresponding kinetic parameters estimated from experimental data. The model thus obtained was used to assess the economics of glucose to HMF processes.