Abstract Biomass fast pyrolysis is potentially one of the cheapest routes toward renewable liquid fuels. Its commercialization, however, poses a multi-scale challenge, which starts with the characterization of feedstock, products and reaction intermediates at molecular scales, and continues with understanding the complex reaction network taking place in different reactor configurations, and in the case of catalytic pyrolysis and upgrading on different catalysts. In addition, crude pyrolysis oil is not immediately usable in the current energy infrastructure, due to undesirable properties such as low energy content and corrosiveness as a result of its high oxygenate content. It, therefore, needs to be upgraded and fractionated to desired specifications. While various types of pyrolysis reactors and upgrading technologies are under development, knowledge transfer and closing the gap between theory and application requires model development. In-depth understanding of the reaction mechanisms and kinetics should be combined with the knowledge of multi-scale transport phenomena to enable design, optimization, and control of complex pyrolysis reactors. Finally, underpinning economic and environmental impacts of biofuel production requires expanding the system boundaries to include the overall process and supply chain. The present contribution aims at providing a comprehensive multi-scale review that discusses the state of the art of each of these aspects, as well as their multi-scale interactions. The study is mainly focused on fast pyrolysis, although reference to other types of pyrolysis technologies is made for the sake of comparison and knowledge transfer.

中文翻译：

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生物质快速热解和生物油升级的多尺度挑战：现有技术和未来研究方向回顾

摘要 生物质快速热解可能是获得可再生液体燃料的最便宜的途径之一。然而，它的商业化带来了多尺度的挑战，首先是在分子尺度上表征原料、产品和反应中间体，并继续了解在不同反应器配置中发生的复杂反应网络，以及催化热解并在不同的催化剂上升级。此外，粗热解油不能立即用于当前的能源基础设施，这是由于其高含氧量导致的不良特性，例如低能量含量和腐蚀性。因此，它需要升级和分馏到所需的规格。各种类型的热解反应器和升级技术正在开发中，知识转移和缩小理论与应用之间的差距需要模型开发。对反应机理和动力学的深入理解应与多尺度传输现象的知识相结合，以实现复杂热解反应器的设计、优化和控制。最后，支持生物燃料生产的经济和环境影响需要扩大系统边界以包括整个过程和供应链。目前的贡献旨在提供全面的多尺度审查，讨论每个方面的最新技术，以及它们的多尺度相互作用。本研究主要集中在快速热解方面，但为了比较和知识转移也参考了其他类型的热解技术。