The Catalyst Review December 2024 - 15

Experimental Abstracts
Toward Efficient Biofuel Production: A Review of
Online Upgrading Methods for Biomass Pyrolysis
Biomass and its fast pyrolysis derivative bio-oil have
emerged as prominent candidates for use as sustainable
and renewable energy sources. Although bio-oil can be
used as a fuel for heat and power generation as well as
a source of biodiesel and green gasoline, its complex
composition limits its direct application in engines or as
a drop-in replacement for petroleum-based fuels. Specifically,
these bio-oil compounds promote aging and
degradation, leading to increased viscosity and phase
separation over time. Herein, the authors comprehensively
analyze recent advancements in biomass fast pyrolysis
and bio-oil upgrading.
Fast pyrolysis (FP) is an efficient process characterized by
a high heating rate and short residence time. It decomposes
biomass into biofuels and chemical raw materials
at elevated temperatures (400−800°C) and quickly
(0.5−3 s) in an oxygen-free environment to maximize
bio-oil production. Various methods can enhance the
physicochemical properties of bio-oil, with chemical
upgrading techniques receiving the most attention. These
methods encompass catalytic processes such as ketonization, aldol
condensation, esterification, hydrodeoxygenation (HDO), and catalytic cracking and deoxygenation using zeolites.
Novel technologies like catalytic plasma reactors and solid oxide electrolyzer cells (SOEC) are also emerging. Physical
upgrading methods such as solvent addition, vacuum distillation, filtration, emulsification, liquid−liquid extraction
(LLE), and solid-phase extraction have also proven effective. Of the techniques mentioned above, hydrodeoxygenation
(HDO) has proven to be the most mature and effective process, significantly reducing oxygen content and improving
fuel properties (Figure 1). On the other hand, among the emerging methodologies under development, microwave-assisted
pyrolysis (MAP) offers a promising and sustainable approach to converting biomass into bio-oil and valuable
chemicals. This conversion process has been extensively studied in laboratories and has shown potential for producing
high-quality bio-oil (Figure 2).
Figure 1. Advantages and disadvantages of the catalysts utilized in the
HDO process. Reproduced with permission from ref 50.
This study concludes with a discussion of key challenges that need to be addressed in order to advance biofuel
production from biomass pyrolysis, including existing research gaps, future directions, and potential developments in
experimental and modeling methodologies. Specifically, the authors focus on catalyst innovation and durability, process
integration and optimization, techno-economic and environmental assessments, scalability and industrial implementation,
and exploring synergies with other energy
technologies. Analysis of these considerations
indicates that despite substantial progress, achieving
efficient and sustainable biofuel production
through online upgrading of biomass pyrolysis will
require ongoing interdisciplinary efforts. In addition,
efforts must focus on developing cost-effective
processes for efficiently separating and converting
the compounds found in upgraded bio-oil (esters,
acids, and furans) into fuels. Pan X, Wu S, Chen, J,
et al. (2024). Energy Fuels, 38, 19414−19441.
Figure 2. A streamlined reaction pathway is postulated for a typical MAP process.
Reproduced with permission from ref 124.
The Catalyst Review
December 2024
15

https://pubs.acs.org/doi/10.1021/acs.energyfuels.4c04131

The Catalyst Review December 2024

Table of Contents for the Digital Edition of The Catalyst Review December 2024