自水解过程中木素缩合反应机制及其对后续过氧酸制浆性能的影响

Extraction of hemicelluloses from raw material as much as possible prior to pulping is the fundamental to realize the biorefinery of the biomass. Autohydrolysis has been paid more attention, because of its economic, effective and eco-friendly properties. However, lignin condensation reaction (repolymerization) occurring in the autohydrolysis is becoming the key factor which hinders the application of the autohydrolysis of hemicelluloses in the Integrated Forest Products Biorefinery. The lignin condensation and degradation reactions originate from the deacetylation during the autohydrolysis. In the present work, the environment and conditions on which the carbonium ions formed during the autohydrolysis would be discussed in order to discover the mechanisms of lignin repolymerization. Severity factor in autohydrolysis, a function of reaction temperature and reaction time, characterizes the treatment intensity. One of the aims in the work is to discover the relationship between the lignin repolymerization and severity factor in the autohydrolysis. In addition, lignin dissolved in autohydrolysates tends to acid-catalysed condensation reactions leading to sticky precipitates of high molecular weight during storage or reprecipitation onto the surface of raw materials. Therefore, the condensation reaction and reprecipitation of lignin dissolved in autohydrolysates would be also studied so as to discover the rule of suppression of lignin repolymerization and reprecipitation. The final goal of this study is to discover the relationship of lignin repolymerization and subsequent peroxyformic acid pulping properties, in order to provide theory evidence for the application of hemicelluloses autohydrolysis in the Integrated Forest Products Biorefinery.

制浆前对原料进行预处理，尽可能抽提出原料中的半纤维素是实现生物质精炼的前提。自水解技术由于其经济性、有效性和环保性，日益受到人们的青睐。然而，木素在自水解过程中发生的缩合反应（再聚反应）已成为制约自水解技术在生物质精炼平台上应用的瓶颈和关键！自水解过程中，脱乙酰作用是导致纤维原料发生木素降解与木素缩合的根源。项目以杨木和竹子为原料，从自水解过程中脱羧动力学的研究入手，探讨木素大分子在弱酸性条件下发生缩合反应的环境、条件和途径，确定自水解强度因子与木素缩合反应的关系，明确降解小分子如乙酸和糠醛在木素缩合反应中的作用和行为，从而揭示木素缩合的反应规律。此外，研究自水解过程中溶出木素在原料表面的吸附性能及水解液的沉积性能。在此基础上，揭示木素在自水解条件下缩合反应的调控机制，及其对后续过氧甲酸蒸煮和漂白的影响，为自水解提取半纤维素的产业化和生物质精炼平台的构建奠定理论基础。

制浆前对原料进行预处理，尽可能抽提出原料中的半纤维素是实现生物质精炼的有效途径。自水解技术由于其经济性、有效性和环保性，日益受到人们的青睐。然而，木素在自水解过程中发生的缩合反应（再聚反应）已成为制约自水解技术在生物质精炼平台上应用的瓶颈和关键！项目以杨木和竹子为原料，探讨了木素大分子在弱酸性条件下发生缩合反应的环境、条件和途径，确定了自水解强度因子与木素缩合反应的关系，从而揭示了木素缩合的反应规律。研究了自水解过程中溶出木素和糖组分在原料表面的吸附沉积性能，揭示了木素在自水解条件下缩合反应的调控机制，及其对后续甲酸蒸煮和漂白性能的影响。此外，还研究了水解液中木素的存在状态及其物化性能，提出了水解液中木素和糖组分有效分离的技术与原理，构建了高温甲酸法高效分离生物质组分的原理与技术，并对甲酸分离木素的性能进行了表征。以上研究，为自水解提取半纤维素的产业化和生物质精炼平台的构建奠定理论基础。