Hydroconversion of Furan Derivatives over Bifunctional Metal Acid Catalysts in the Gas Phase

Abstract

The conversion of biomass to chemicals and fuels has attracted much academic and industrial interest. Such interest has increased due to the decline of fossil fuel reserves affecting the energy supply. Biomass-derived furanic compounds are a low-cost renewable feedstock that could be applied to produce value-added chemicals, which can boost the supply of green energy. 2,5-Dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) are recognised as important intermediates within bio-oil upgrading transformation. However, furanic compounds have a high content of oxygen, which influences their acidity, homogeneity, polarity and heating value. Bifunctional metal-acid catalysts could promote furan ring-opening and oxygen removal in the hydrodeoxygenation (HDO) upgrading process. Nevertheless, the kinetics and mechanism of HDO of furanic compounds, particularly at the gas-solid interface, have not been studied in detail yet. Moreover, to the best of our knowledge, no research has been done on the use of heteropoly acids (HPAs) as catalysts in these reactions so far. The main purpose of this thesis is to investigate the conversion of DMF and DMTHF as model furanic compounds to produce value-added products at the gas-solid interface under mild conditions via catalytic hydrogenation, hydrogenolysis and hydrodeoxygenation reactions in the presence of bifunctional metal-acid catalysts comprising Pt and cesium salt of Keggin-type tungstophosphoric heteropoly acid Cs2.5H0.5PW12O40, hereinafter referred to as CsPW. This cesium salt has a large surface area, high thermal stability (~500 °C decomposition temperature) and high tolerance to water, with proton sites almost as strong as those in the parent heteropoly acid H3PW12O40. The mechanism and kinetics of these reactions on the catalyst surface were also investigated. All reactions were carried out in a fixed-bed continuous flow reactor using H2 as a carrier gas at ambient pressure (1 bar) in the temperature range 70–100 °C. Our results demonstrate the high efficiency of bifunctional metal-acid catalysis for the hydroconversion of furanic compounds to alkanes that can be used as fuel components