Upgrading of Oils from Biomass and Waste: Catalytic Hydrodeoxygenation

Abstract

The continuous demand for fossil fuels has directed significant attention to developing new fuel sources to replace nonrenewable fossil fuels. Biomass and waste are suitable resources to produce proper alternative fuels instead of nonrenewable fuels. Upgrading bio-oil produced from biomass and waste pyrolysis is essential to be used as an alternative to nonrenewable fuel. The high oxygen content in the biomass and waste pyrolysis oil creates several undesirable properties in the oil, such as low energy density, instability that leads to polymerization, high viscosity, and corrosion on contact surfaces during storage and transportation. Therefore, various upgrading techniques have been developed for bio-oil upgrading, and several are introduced herein, with a focus on the hydrodeoxygenation (HDO) technique. Different oxygenated compounds were collected in this review, and the main issue caused by the high oxygen contents is discussed. Different groups of catalysts that have been applied in the literature for the HDO are presented. The HDO of various lignin-derived oxygenates and carbohydrate-derived oxygenates from the literature is summarized, and their mechanisms are presented. The catalyst’s deactivation and coke formation are discussed, and the techno-economic analysis of HDO is summarized. A promising technique for the HDO process using the microwave heating technique is proposed. A comparison between microwave heating versus conventional heating shows the benefits of applying the microwave heating technique. Finally, how the microwave can work to enhance the HDO process is presented.

Advances in the Pyrolysis Process and the Generation of Bioenergy

“…Esses processos podem ser de natureza física ou físico-química, promovendo alguma melhoria na qualidade do bio-óleo bruto na pirólise. Dentre esses, pode se citar: [76][77][78]. Although there are several strategies to improve the quality of bio-oil, the most studied processes, aiming at the industrial potential, are hot vapor filtration (HVF), catalytic hydrodeoxygenation (HDO) and steam reforming.…”

“…H2 is a gaseous fuel with high added value due to its energy density and its combustion is free of carbon emissions. In this process, bio-oil, as well as fossil fuels, react with H2O vapor at temperatures in the range of 700-1000°C, in the presence of a catalyst (usually nickel-based) offering as main product the H 2 -rich syngas, along with CO 2 [76][77][78]. The main advantage of this process is the simultaneous production of high value-added fuel (H2), and it allows the assimilation of CCSU (Carbon Capture Storage and Utilization) technologies.…”

Advances and Challenges in the Valorization of Bio-Oil: Hydrodeoxygenation Using Carbon-Supported Catalysts

“…239 The design of the optimal catalyst will also require a better understanding of HDO mechanisms. Although HDO pathways of model compounds are widely studied and established, 120 there is a big gap when mixtures of compounds (contained in bio-oil) or raw bio-oil are used as a feedstock and how these compounds interact with each other affecting the global reaction network.…”

Biorefinery via Catalytic Upgraded Fast Pyrolysis of Biomass

“…This technology is the realization of biomass pyrolysis followed by hydrodeoxygenation used to upgrade fast pyrolysis bio-oil, as oxygenates present in bio-oil react with hydrogen to produce a stable hydrocarbon fuel and water, which is removed by separation. Single stage HDO of condensed bio-oil is unsuited for commercial scale bio-oil upgrading, as the coking and polymerization, which occurs upon re-heating of the bio-oil, rapidly deactivates the catalyst and plugs the reactor [42][43][44][45]. Dual or multiple stage HDO has shown more promising results, as the most reactive oxygenates can be stabilized at low temperature prior to deep HDO for full deoxygenation.…”