Abstract Pyrolysis is a promising method for thermochemical conversion of forest biomass into liquid biofuels or platform/specialty chemicals. In this work, bark from silver birch (Betula pendula) was processed through slow pyrolysis with fractional condensation, and the obtained liquid fractions were analyzed by various bulk chemical analyses as well as high-resolution mass spectrometry. The process had three successive stages, drying, torrefaction, and pyrolysis, occurring at 135, 275, and 350 °C, respectively, and pyrolysis liquids were obtained at three condensing temperatures, 130, 70, and 5°C, resulting in eight liquid fractions. Most fractions had high water content, especially those obtained from the drying stage. Only the semi-solid product, obtained from the pyrolysis stage at the condensing temperature of 70°C, had a very low water content and a high carbon yield. There were major differences in the chemical compositions between the liquid fractions; the drying fractions contained mostly aliphatic and phenolic extractives as well as light hydrocarbons, while the torrefaction fractions were enriched with sugaric compounds, resulting from hemicellulose and cellulose degradation. In contrast, the pyrolysis fractions were mainly composed of suberinic fatty acids, terpenoids (e.g., betulin) and their condensation products, and phenolic compounds. Many terpenoids were dehydrated to form a plethora of condensed, water-insoluble alicyclic and aromatic hydrocarbons. Although the temperature-programmed slow pyrolysis shows potential for thermochemical processing of industrial bark residues, excessive dehydration reactions may limit its applicability especially for “in situ fractionation”.

中文翻译：

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分凝程序升温缓慢热解对桦树皮的热化学转化

摘要 热解是将森林生物质热化学转化为液体生物燃料或平台/特种化学品的一种很有前景的方法。在这项工作中，银桦 (Betula pendula) 的树皮通过分级冷凝的缓慢热解进行处理，并通过各种本体化学分析和高分辨率质谱法分析获得的液体馏分。该过程有干燥、烘焙和热解三个连续阶段，分别在 135、275 和 350 °C 下发生，并在三个冷凝温度（130、70 和 5°C）下获得热解液，从而产生八种液体。分数。大多数馏分含水量高，尤其是那些从干燥阶段获得的馏分。只有在 70°C 冷凝温度下从热解阶段获得的半固体产品，具有非常低的含水量和高碳产率。液体组分之间的化学成分存在较大差异；干燥部分主要包含脂肪族和酚类提取物以及轻质烃，而烘焙部分富含由半纤维素和纤维素降解产生的含糖化合物。相比之下，热解馏分主要由软木酸脂肪酸、萜类化合物（如桦木脑）及其缩合产物和酚类化合物组成。许多萜类化合物脱水形成过多的缩合的、不溶于水的脂环烃和芳香烃。尽管程序升温缓慢热解显示出工业树皮残留物的热化学处理潜力，