Sustainable hydrogen and value-added chemical production: pyrolysis oil enhancement methods and electrolysis of the by-products

Brueckner, Tobias Michael (2019) Sustainable hydrogen and value-added chemical production: pyrolysis oil enhancement methods and electrolysis of the by-products. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Pyrolysis oils of forest residues can be used as renewable fuels for burner applications. However, some produced oils do not meet the ASTM standard for pyrolysis oil in boiler applications and must be upgraded. The scope of this work was to enhance pyrolysis oils via distillation and pervaporation to improve its properties as a fuel and produce value-added by-products. The main value still remains in the burner fuel, however the separated by-product can be used for a sustainable hydrogen production via electrolysis or the value-added chemicals can be used for other applications [1]. Distillation and pervaporation have been studied. Distillation was used as a reference case to compare with the pervaporation results. To find the optimal pervaporation process conditions to separate water from the aqueous phase of bark pyrolysis oil a 2³ factorial design experiment study with commercial polyacrylonitrile-supported polyvinyl alcohol membranes was carried out. The conditions of 80°C and a feed flow rate of 0.1 mL min⁻¹ resulted in an enhancement of the pyrolysis bark oil aqueous phase from an incomplete combustion to a heating value of 16.07 MJ kg⁻¹ and lowered the water content from 70.2 to 21.4 mass% to meet the ASTM D7544-12 standard in the investigated lab-scale pervaporation unit. Simultaneously low molecular weight components were isolated in the permeate. Electrolysis of these low molecular weight organics, such as methanol, ethanol, ethylene glycol, and glycerol can produce hydrogen at much lower potentials than water electrolysis, and yields useful oxidation products such as acetic acid and glyceric acid [2]. Efficient use of biofuels in electrolysis and fuel cells requires anode catalysts with both high activities and high selectivity for the preferred product. A catalyst screening was carried out to identify a highly selective catalyst for the complete oxidation of the fuel to carbon dioxide. A novel experimental method for determining catalyst activities based on transferred electrons was developed.

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