Center for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
Center for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
Curr Opin Biotechnol. 2019 Apr;56:193-201. doi: 10.1016/j.copbio.2018.12.005. Epub 2019 Jan 9.
Reductive catalytic fractionation (RCF) of lignocellulose is an emerging biorefinery scheme that combines biomass fractionation with lignin depolymerisation. Central to this scheme is the integration of heterogeneous catalysis, which overcomes the tendency of lignin to repolymerise. Ultimately, this leads to a low-M lignin oil comprising a handful of lignin-derived monophenolics in close-to-theoretical yield, as well as a carbohydrate pulp. Both product streams are considered to be valuable resources for the bio-based chemical industry. This Opinion article sheds light on recently achieved milestones and consequent research opportunities. More specifically, mechanistic studies have established a general understanding of the elementary RCF steps, which include (i) lignin extraction, (ii) solvolytic and catalytic depolymerisation and (iii) stabilisation. This insight forms the foundation for recently developed flow-through RCF. Compared to traditional batch, flow-through RCF has the advantage of (i) separating the solvolytic steps from the catalytic steps and (ii) being a semi-continuous process; both of which are beneficial for research purposes and for industrial operation. Although RCF has originally been developed for 'virgin' biomass, researchers have just begun to explore alternative feedstocks. Low-value biomass sources such as agricultural residues, waste wood and bark, are cheap and abundant but are also often more complex. On the other side of the feedstock spectrum are high-value bio-engineered crops, specifically tailored for biorefinery purposes. Advantageous for RCF are feedstocks designed to (i) increase the total monomer yield, (ii) extract lignin more easily, and/or (iii) yield unconventional, high-value products (e.g. alkylated catechols derived from C-lignin). Taking a look at the bigger picture, this Opinion article highlights the multidisciplinary nature of RCF. Collaborative efforts involving chemists, reactor engineers, bioengineers and biologists working closer together are, therefore, strongly encouraged.
木质纤维素的还原催化分级（RCF）是一种新兴的生物炼制方案，它将生物质分级与木质素解聚结合在一起。该方案的核心是异相催化的整合，克服了木质素重新聚合的趋势。最终，这导致了一种低分子量木质素油，其中包含了几种接近理论产率的木质素衍生的单酚，以及一种碳水化合物纸浆。这两种产物都被认为是生物基化学工业的有价值资源。本文观点阐明了最近取得的里程碑和随之而来的研究机会。更具体地说，机理研究已经对包括（i）木质素提取、（ii）溶剂解和催化解聚以及（iii）稳定化在内的基本 RCF 步骤建立了普遍的理解。这一见解为最近开发的直通式 RCF 奠定了基础。与传统的间歇式相比，直通式 RCF 具有以下优点：（i）将溶剂解步骤与催化步骤分开，（ii）是一个半连续过程；这两者都有利于研究目的和工业操作。尽管 RCF 最初是为“原始”生物质开发的，但研究人员才刚刚开始探索替代原料。低价值生物质来源，如农业废弃物、废木材和树皮，既便宜又丰富，但也往往更复杂。在原料谱的另一端是高价值的生物工程作物，专门为生物炼制目的而设计。有利于 RCF 的是设计用于（i）增加总单体产量、（ii）更容易提取木质素、和/或（iii）产生非常规的高价值产品（例如，源自 C-木质素的烷基化儿茶酚）的原料。从更大的角度来看，本文观点强调了 RCF 的多学科性质。因此，强烈鼓励化学家、反应器工程师、生物工程师和生物学家更紧密地合作开展协作努力。
