Thermochemical lignin conversion processes can be described as complex reaction networks involving not only de-polymerization and re-polymerization reactions, but also chemical transformations of the depolymerized mono-, di-, and oligomeric compounds. They typically result in a product mixture consisting of a gaseous, liquid (i.e., mono-, di-, and oligomeric products), and solid phase. Consequently, researchers have developed a common strategy to simplify this issue by replacing lignin with simpler, but still representative, lignin model compounds. This strategy is typically applied to the elucidation of reaction mechanisms and the exploration of novel lignin conversion approaches. In this review, we present a general overview of the latest advances in the principal thermochemical processes applied for the conversion of lignin model compounds using heterogeneous catalysts. This review focuses on the most representative lignin conversion methods, i.e., reductive, oxidative, pyrolytic, and hydrolytic processes. An additional subchapter on the reforming of pyrolysis oil model compounds has also been included. Special attention will be given to those research papers using “green” reactants (i.e., H₂ or renewable hydrogen donor molecules in reductive processes or air/O₂ in oxidative processes) and solvents, although less environmentally friendly chemicals will be also considered. Moreover, the scope of the review is limited to those most representative lignin model compounds and to those reaction products that are typically targeted in lignin valorization.

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木质素模型化合物的多相催化热化学转化：概述

木质素热化学转化过程可以描述为复杂的反应网络，不仅涉及解聚和再聚合反应，还涉及解聚的单，二和低聚化合物的化学转化。它们通常产生由气态，液态（即，单，二和低聚产物）和固相组成的产物混合物。因此，研究人员开发了一种通用的策略来简化此问题，方法是用更简单但仍具代表性的木质素模型化合物代替木质素。该策略通常用于阐明反应机理和探索新型木质素转化方法。在这篇评论中，我们对使用多相催化剂转化木质素模型化合物的主要热化学方法的最新进展进行了概述。这篇综述着重于最具代表性的木质素转化方法，即还原，氧化，热解和水解过程。还包括有关重整热解油模型化合物的其他子章节。将特别关注那些使用“绿色”反应物（即H₂或还原过程中的可再生氢供体分子，或氧化过程中的空气/ O ₂）和溶剂，尽管也会考虑使用对环境不太友好的化学物质。而且，本综述的范围限于那些最具代表性的木质素模型化合物和通常以木质素增价为目标的那些反应产物。