Production of renewable fuels and chemicals from bio-oil using fluids near the critical point

Abstract

The production of energy and chemicals using dwindling fossil feedstock reserves (oil, gas and coal) has generated global environmental and energy security concerns. This has motivated research into alternative energy technologies and sustainable products and processes. Over the past few decades, research and interest in biomass as a renewable feedstock has exponentially grown. Bio-oil from biomass is particularly interesting as it can be used for energy, chemicals, or as an energy carrier. However, crude bio-oil possesses certain physical and chemical properties which prevent its direct application and integration into existing fuel infrastructures. For example, the high acidity of untreated bio-oil can cause corrosion of vessels and pipework.Therefore, a detailed study which aimed to improve the properties of bio-oil using methanol, ethanol and isopropanol for bio-oil blending and supercritical upgrading was conducted. The results showed supercritical methanol treatment eliminated the acids and improved the pH of the bio-oil. However, the crude bio-oil contained 37.03 % phenols which did not transform after blending with alcohols or after supercritical upgrading. Therefore, the research aimed to convert phenol to less reactive compounds such as cyclohexanol in order to improve the bio-oil properties. A process of in situ catalytic hydrogenation of phenol using aqueous phase reforming of methanol for the hydrogen source achieved high cyclohexanol yield (93.35 %) and selectivity (94.23 %).A new process of producing industrially desirable and valuable chemicals including methyl isovalerate and a mixture of monoterpenes (p-Mentha-1,4(8)-diene, D-Limonene, and y-Terpinene) from a bio-oil based compound (geranyl isovalerate) was reported in Chapter 6. No catalyst was used, and subcritical water performed the role of catalyst and co-solvent with supercritical methanol. Very high geranyl isovalerate conversions was achieved as less than 3 % of it was detected in the products and methyl isovalerate and the monoterpenes accounted for 97 %.