Identifying the coking of bio-oil in pyrolysis: An in-situ EPR investigation

IF 7.2 2区 工程技术 Q1 CHEMISTRY, APPLIED
Liqun Ma , Wei Deng , Xun Hu , Kai Xu , Jun Xu , Long Jiang , Yi Wang , Sheng Su , Song Hu , Jun Xiang
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引用次数: 0

Abstract

Serious coking from the bio-oil polymerisation is a bottle-neck challenge for bio-oil thermal upgrading. Probing the mechanism of bio-oil coking is the first step to achieve high carbon conversion efficiency. In this study, in-situ electron paramagnetic resonance (EPR) spectroscopy was used to characterise the stable free radical generation during bio-oil pyrolysis at 250–350 °C with reaction time of 2–10 min, which identify the coking process of bio-oil. The liquid and solid products were characterised using gas chromatography-mass spectrometer (GC–MS), ultraviolet fluorescence (UV-F) and Raman spectroscopy. The results indicate that the coking of bio-oil in pyrolysis can be divided into three stages of varied characteristics. The coke formation precedes with an initial induction period that lasts for 2–8 min and shortens with increasing pyrolysis temperature. In the period, light components polymerise into heavy ones, including polycyclic aromatics as the essential coke precursors. After the induction period, significant amounts of stable free radicals are generated with coke formation, and the content increases from 0.2 to 1.6–7.8 μmol/g bio-oil in the early stage of coking. Meanwhile, the coke precursors, polycyclic aromatics, are rapidly depleted. Afterwards, in the late stage, the nascent coke gradually condenses and the stable free radical content increases slowly.

识别热解过程中生物油的结焦:原位 EPR 调查
生物油聚合产生的严重结焦是生物油热能升级的瓶颈难题。探究生物油结焦的机理是实现高碳转化效率的第一步。本研究利用原位电子顺磁共振(EPR)光谱分析了生物油在 250-350 ℃、反应时间为 2-10 分钟的热解过程中产生的稳定自由基,从而确定了生物油的结焦过程。使用气相色谱-质谱(GC-MS)、紫外荧光(UV-F)和拉曼光谱对液体和固体产物进行了表征。结果表明,生物油在热解过程中的结焦可分为三个阶段,其特征各不相同。焦炭形成之前有一个初始诱导期,持续时间为 2-8 分钟,随着热解温度的升高而缩短。在此期间,轻质成分聚合成重质成分,包括作为焦炭基本前体的多环芳烃。诱导期结束后,大量稳定的自由基随焦炭的形成而产生,其含量从焦化初期的 0.2 μmol/g 生物油增加到 1.6-7.8 μmol/g。与此同时,焦炭前体多环芳烃迅速耗尽。随后,在后期阶段,新生焦炭逐渐凝结,稳定自由基含量缓慢增加。
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来源期刊
Fuel Processing Technology
Fuel Processing Technology 工程技术-工程:化工
CiteScore
13.20
自引率
9.30%
发文量
398
审稿时长
26 days
期刊介绍: Fuel Processing Technology (FPT) deals with the scientific and technological aspects of converting fossil and renewable resources to clean fuels, value-added chemicals, fuel-related advanced carbon materials and by-products. In addition to the traditional non-nuclear fossil fuels, biomass and wastes, papers on the integration of renewables such as solar and wind energy and energy storage into the fuel processing processes, as well as papers on the production and conversion of non-carbon-containing fuels such as hydrogen and ammonia, are also welcome. While chemical conversion is emphasized, papers on advanced physical conversion processes are also considered for publication in FPT. Papers on the fundamental aspects of fuel structure and properties will also be considered.
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