Lignocellulosic Biomass Fractionation and Depolymerization with Sub/Supercritical Fluids

开发新的环境友好型技术对于从巨大的木质纤维生物质(以下称为生物质)中产生附加值产品至关重要。亚/超临界条件下的流体是农业副产品(滞销的农作物秸秆)和食品工业副产品(土豆皮)生物质加工的通用溶剂。加压液体(PL，例如亚临界水)和超临界流体(SCF)，如超临界水和超临界二氧化碳(SC-CO2)，为利用分馏技术获得新的增值产品提供了一个绿色加工平台。近年来，利用PL/SCF作为反应介质进行解聚反应引起了人们的关注。有报道表明，通过优化反应温度和压力，可以控制水解，以实现特定应用的目标增值化合物。然而，所涉及的反应机理以及它们的活化能和体积还需要进一步的研究。到目前为止，申请人的研究计划侧重于使用亚临界水和超临界二氧化碳来确定选定糖和酚类化合物的溶解度，提取生物活性物质，如酚类、碳水化合物、青蒿素等，以及在超临界二氧化碳介质中和高压下通过热处理进行反应，以及对化合物在新溶剂混合物中的相平衡进行建模。因此，未来的工作将继续建立在这一专门知识的基础上，进一步促进PL/SCF媒体的新颖组合处理开发。这项建议的主要目标是扩展关于增值化合物在PL中的溶解行为的基础知识，并确定热力学变量和传输性质如何影响PL/SCF介质中的分级、反应、颗粒形成和这些过程的组合，以进一步开发新的绿色技术，以获得可在食品和非食品工业应用中具有多种用途的生物质增值产品。在拟议的研究计划中，将通过实验测量热力学性质，如溶解度。平衡研究将允许选择分馏和反应过程的最佳压力和温度。在反应过程中，以土豆皮和秸秆为原料，测定其在PL/SCF处理前后的纤维素、半纤维素和木质素的含量。将对新的工艺组合进行实验研究。分馏后，将对进一步解聚进行评估，以获得各种增值化合物。半纤维素中发现的增值化合物可以首先被去除，然后通过特定的反应或丰富纤维素中的残留物将残留物转化为附加值化合物。然后，通过新的工艺开发，获得纳米纤维/晶体。依靠创新的加工技术开发增值化合物的总体目标将通过实验室规模的概念验证基础研究来实现。一旦建立了这一新工艺，将对涉及不同生物量的谷物作物的应用进行调查。对于批处理和半连续系统，将获得关于工艺参数影响的有价值的信息，并且未来的目标是在连续系统上实施它。使用PL/SCF技术可以最大限度地减少或消除有机溶剂和催化剂的使用，从而最大限度地减少对环境的影响，满足注重环境和健康的消费者日益增长的需求，并通过探索可用的大量生物质来促进加拿大的生物经济。

Development of new environmentally friendly technologies is crucial to generate value-added products from vast lignocellulosic biomass, herein after referred to as biomass. Fluids under sub/supercritical conditions are versatile solvents for biomass processing of agricultural by-products (unmarketable crop straw) and food industry by-products (potato peel). Pressurized liquid (PL, e.g. subcritical water) and supercritical fluids (SCF), such as supercritical water and supercritical carbon dioxide (SC-CO2) provide a green processing platform to obtain new value-added products using fractionation techniques. Recently, the use of PL/SCF as reaction media has attracted attention for depolymerization. Reports have shown that by optimizing the reaction temperature and pressure, hydrolysis can be controlled to achieve targeted value-added compounds for specific applications. However, the reaction mechanisms involved need to be further investigated as well as their activation energy and volume. The applicant's research program to date has focused on the use of subcritical water and SC-CO2 to determine solubility of selected sugars and phenolics, extraction of bioactives, such as phenolics, carbohydrates, artemisinin, etc, as well as reactions in SC-CO2 media and under high pressure assisted by thermal processing, and modeling of phase equilibria of compounds in new solvent mixtures. Future work would therefore continue to build on this expertise by further contributions to novel combined processing development in PL/SCF media. The main objectives of this proposal are to expand fundamental knowledge on solubility behavior of value-added compounds in PL, and to determine how thermodynamic variables and transport properties influence fractionation, reaction, particle formation and the combination of these processes in PL/SCF media to develop further new green technologies to obtain value-added products of biomass that can have a number of uses in food and non-food industrial applications. In the proposed research program, thermodynamic properties, such as solubility will be measured experimentally. Equilibrium studies will allow the selection of optimum pressure and temperature for fractionation and reaction processes. For the reaction process, potato peel and straw will be used where their contents of cellulose, hemicellulose and lignin will be determined before and after treatments with PL/SCF. Novel combination of processes will be experimentally investigated. After fractionation, further depolymerization will be assessed to obtain a diverse range of value-added compounds. Value-added compounds found in hemicellulose can be first removed and then the residues can be converted to value-added compounds through specific reactions or enriching the residue in cellulose. Then, nano-cellulose fiber/crystal will be obtained by novel process development. The overall goal of developing value-added compounds relying on innovative processing technologies will be accomplished through fundamental research at laboratory scale for proof-of-concept. Once the novel process is established, applications involving diverse biomasses of cereal crops will be investigated. Valuable information on the effect of process parameters will be obtained for a batch and semi-continuous system with a future goal to implement it on a continuous system. The use of PL/SCF technology minimizes or eliminates the use of organic solvents and catalysts, thus minimizing environmental impact and meeting the growing demands of environment- and health-conscious consumers as well as boosting Canada’s bioeconomy with the exploration of vast biomass available.