Ni基催化剂协同溶剂化作用解聚木质素产物调控规律的基础研究

Lignin is the second abundant natural polymer in nature. Its unique styrene acrylic make its can be aromatic ring structure high value-added chemicals and high calorific value of bio-oil renewable raw materials. But the density and complex three-dimensional stereoscopic structure of lignin lead to that the repolymerizations happen in the process of depolymerization, the depolymerization products are so complex, the target products are hard to be controlled and separated and purified. Based on the problems mentioned above, the project puts forward a series of method to resolve these problems. First, different acid-base, different size and structure of the carrier will be made, loading Ni active as catalyst center. Different reaction medias will be chosen and prepared in the deploymerization using its solvation effect coupling with the catalytic activity of the Ni based catalyst, promoting the swelling/dissolution of lignin in the reaction system and strengthening the mass transfer between lignin and the catalysts and breaking ether bonds selectively in order to realize the depth of the lignin depolymerization and product selectivity control. Modern means of in situ sampling and characterization will be used in the process of lignin depolymerization to capture the intermediate. Lignin depolymerization reaction characteristics in different reaction medium will be studied. The regulation mechanism of synergy and matching between the parameters of solvent and catalyst structure-activity will be obtained also including the product selectivity mechanism. Product separation and purification of depolymerization of single phenol will be investigated and further consideration the usage of residual oligomers.

木质素是自然界中含量仅次于纤维素的天然高分子聚合物，其独特的苯丙烷结构使其具有生产生物燃油和化工品的巨大潜力，但木质素解聚过程中易发生重聚、产物不可调控等问题制约其能源化和资源化利用。针对以上问题，本项目提出利用Ni基催化剂协同反应介质的溶剂化作用对木质素解聚产物进行调控，阐明木质素催化解聚过程中化学键活化与断裂的演变规律，揭示木质素的转化历程及产物选择性调控机理。主要研究内容如下：①纳米或介孔Ni基木质素解聚催化剂制备、表征和在不同传热传质及流动过程的性能研究；②研究在不同反应介质中，Ni基催化剂的木质素解聚活性，获得催化剂协同反应介质对木质素解聚产物调控的影响规律；③利用先进的检测手段对木质素解聚过程进行原位及原位取样表征，明确反应介质、催化剂构效对活泼中间产物重聚反应的抑制作用，提出产物选择性调控机理。本研究将为木质素高效定向催化解聚与资源化利用提供基础理论与工艺参数。

本项目针对木质素解聚难、解聚产物易重聚等问题，分别在木质素提取、解聚催化剂开发、反应溶剂对木质素解聚影响、木质素解聚目标产物芳香类化合物的分离、芳香类化合物加氢脱氧等方面开展了研究。研究结果表明：.1）不同碳数、不同羟基数的醇溶剂对木质素提取率、木质素结构均有较大的影响；以1，4-丁二醇为溶剂时，木质素的提取率最高为91.73%，而且该木质素官能团最丰富，在解聚过程中，解聚单环芳香类化合物收率最高；.2）开发了4类Ni基催化剂，建立其木质素解聚构效关系；高分散Ni/SBA-15催化剂可使木质素解聚积碳率从20%降至3%以下，介孔孔道可为活泼中间产物提供微环境以抑制木质素解聚过程积碳反应的发生；碱性环境下，Ni/MLC催化剂将碱木质素单环芳香类化合物收率从17%提高至36%以上;.3）开展了反应介质溶剂化的研究，包括甲醇、乙醇、异丙醇、丁醇、十氢萘、四氢呋喃、二氧六环、水等单一溶剂及乙醇-水、乙酸乙酯-水、十氢萘-乙醇、二氧六环-水等双溶剂体系；在众多溶剂中，以乙醇/水为反应体系（3：2）时，目标产物收率最高达37.51%，原因可能与木质素在该体系中的溶解/溶胀有关，木质素在该体系中更易打开内部氢键、暴露木质素醚键，利于催化剂与木质素待断化学键的接触，让催化剂进行选择性断键；.4）通过木质素解聚产物的极性、沸点以及在不同溶剂中溶解度的差异，通过减压蒸馏、不同比例配比溶剂的萃取等工艺探索，实现了木质素解聚酚类化合物的提取，研究结果优选溶剂为体积比在1: 1~2:1的乙醚/乙酸乙酯/石油醚与水中，可实现单环芳香类化合物84wt%的提取率；.5）开发了木质素解聚产物加氢脱氧系列催化剂，发现SS-Ni/SiO2催化效果最佳，可在120℃下实现愈创木酚的完全转化，产物为环己醇，加氢性能远远优于一般的负载型和共沉淀型的Ni/SiO2催化剂。.木质素解聚、单环芳香类化合物分离至芳香类化合物加氢脱氧等研究对于木质素制备化学品的机理分析及实际应用具有重要的作用和意义.