Crude pyrolysis bio-oils are recognized as a potential source to replace conventional fuels and chemicals. However, their high water content, viscosity and acidity significantly hinder industrial applications. Hydrodeoxygenation Upgrading (HDO) of pyrolysis bio-oil, can remarkably improve their quality and advanced the application of being as an alternative fuel or chemical. During the upgrading, the high contents of water and acids in of the crude bio-oil may introduce unwanted corrosion damage to the processing equipment. This paper investigated the corrosion performance of two candidate constructional steels (UNS S31603 and UNS S30400) under the HDO processes using supercritical ethanol solvent, NiMoW/Al2O3 catalyst and different hydrogen resources (hydrogen gas or formic acid) at 325 °C. The introduction of H2 gas or formic acid application of formic acid could effectively improve upgrading efficiency. The application of formic acid led to a less aggressive upgrading environment to the steels. UNS S31603 exhibited a better corrosion resistance under the catalytic HDO process compared to UNS S30400.


Biofuels are renewable energy resources to replace fossil fuels since the latter are depleting and their application lead to serious environmental impacts.1 Fast pyrolysis is an industrial approach to convert a larger amount of raw biomass into bio-oils in a timely fashion. However, their poor qualities, such as low thermal stability, high water and acid contents, and low heating value, make them not ready f to be as transportation fuels directly.2,3 Moreover, their high water content and acidity can introduce corrosion concern during handling, storage , transportation and upgrading.4

To address the above challenges, catalytic hydro-de-oxygenation (HDO) technology is being developed to upgrade the crud-oil in a cost-effective manner, Pervious studies showed that it could efficiently reduce oxygen content in the crude oil and achieve high oil yield target.5 Due to its liquid-like density, gas-like high diffusivity, and low viscosity, supercritical ethanol (Tc: 241 °C, Pc: 63 bar) can be employed as an effective solvent in the catalytic HDO process.6 More importantly, ethanol also can act as an in-situ hydrogen donor through the ability of generating hydroxyl and hydrogen radicals to interact with the crude oils.7-9 The HDO processes are usually required to operate in high pressure hydrogen environments. Such requirements can be achieved by charging high pressure hydrogen gas, which raise safety concerns and process costs and other alternative pathways (such as the application of formic acid). Formic acid can be derived from bioresources and used as a sustainable alternative source for hydrogen charging under the HDO upgrading.

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