Catalytic conversion of biomass to fuels and commodity chemicals

Bagnato, Giuseppe (2020) Catalytic conversion of biomass to fuels and commodity chemicals. PhD thesis, Heriot-Watt University.

Abstract

The production of biofuels from pyrolysis of biomass is one of the alternatives to fossil fuels, but the high oxygen content, acidity and instability of the pyrolysis bio-oils still represent a challenge limiting its widespread diffusion. The aim of this research project focuses on develop further an existing technology to stabilise the pyrolytic oil by hydrogenation reaction and in evaluating the economic feasibility for industrial development. Based on literature review, new catalysts have been synthesised and tested for the bio-oil hydrogenation. By impregnation technique, the zirconia has been doped with Pd and not noble metals (Cu and Fe), characterised and their performances studied, in term of conversion and selectivity for key bio-compounds. Vanillin was completely converted after 80 min at 100°C and 50 bar, in presence of PdFe/ZrO2. Furthermore, promising results were obtained testing the PdFe/ZrO2 catalyst on a real water bio-oil fraction, where the catalyst was able to maintain ~90% of carbon in the liquid phase, reduce the polymerisation degree and the acidity of the bio-oil under mild conditions. With the idea to minimise the hydrogen consumption and lowering the energy demand for the hydrogenation, the reaction was carried out at low operating conditions using a membrane reactor. A Ru-polyethersulfone (PES) catalytic membrane was synthesised and tested for furfural hydrogenation achieving a TOF equal to 48,000 h-1 , at 70 ºC and 7 bar, but metal leaching with consequent deactivation was noticed To address the deactivation of the Ru-PES membrane, Ra u- Polyether ether ketone (PEEK -WC) membrane was developed using a green solvent and tested with a simulated water bio-oil fraction at different temperature (65-85°C), pressure (11-18 bar) and H2 flow rate (5 -25 mL/min.). The PEEK-WC membrane resulted in an enhanced stability and good hydrogenation activity. Finally, to enhance the understanding of the real feasibility at industrial level of the proposed biorefinery pathway (Pyrolysis/HDO), an economic feasibility study was designed and carried out for two different scenarios: (i) using micro algae as feedstock for producing drop-in bio-fuels, which resulted in a minimum fuel selling price of 1.418 $/L, ~ 50 % higher than fossil fuels; and (ii) pinewood bio-oil (current feedstock) orientate to for producing chemicals (for 75% of bio oil processed) and fuels achieving an economic potential of 38,234 MM$/y for 10Mt/y feedstock treated, suggestion a valid alternative for green chemicals production, with relative price decrement.