水热溶剂热技术低压转化植物性生物质废弃物为低氧生物油的基础研究

In this project, we focus on converting plant biomass wastes into bio-crude oil with low oxygen content under low pressure condition by combination of hydrothermal and solvo-thermal route. The oil can be finally catalysis updated into oxygen-free engine fuel oil. A novel combination of alkaline soaking and extrusion technique before liquefaction is used to pretreat the bio-mass, which can degrade and destruct the strong network combination of cellulose, hemi- cellulose and lignin to speed up the further liquefaction. Then, the liquefaction experiments of model cellulose and lignin are conducted by using water or organic solvents like tetralin as hydro or solvo-thermal media in a batch autoclave under 200-300oC. The intermediates and final products in the liquefaction process are monitored and quantified by GC, GC/MS，NMR and CHNS/O elemental analyzer. Effect of pretreatment conditions, solvents, ratio of solid mass to solvent, liquefaction time and temperature, catalyst on liquefaction processing pressure, formation of CO2 and CO, intermediates and final products, C/H/O ratio of final products are carefully discussed. The liquefaction mechanisms through different solvent are summarized to point out the keys for controlling the C/H/O ratio of products and producing the bio-crude oil with low oxygen content under low processing pressure. Based on the optimized low processing pressure and specific solvo-thermal conditions derived from the model compounds liquefaction, the typical plan bio-mass wastes, such as fast growing eucalyptus, bagasse, etc., are liquefied in the batch autocalve to produce the low oxygen bio-oil. The hydrodeoxygenation (HDO) experiments are carried out to investigate the feasibility of upgrading the oxygen-low bio-oil products to oxygen-free engine fuel oil.Through this study, a useful guideline is provided on how to convert the bio-mass wastes into oxygen-free fule oil by applying this novel low pressure liquefaction technique and the HDO process.

本项目拟采用水热和溶剂热技术，进行低压连续转换植物性生物质废弃物为低氧生物原油的基础研究。首先以纤维素和木质素为模型原料，通过碱浸和挤压膨化的预处理过程，使用间歇型反应釜进行水热和溶剂热液化基础实验，借助GC，GC-MS,NMR和元素分析仪等手段对反应产物进行定性定量分析，实时监测各产物组分的变化，考察不同预处理条件，溶剂，固液比，反应时间，反应温度和催化剂的添加，对液化过程压力变化和生物原油生成的影响，进而探讨其液化的基本动力学规律, 寻求低压可选择性生成低氧生物原油的控制机制，为实现植物性生物质废弃物高效低压转化为生物原油提供理论依据。在此基础上，采用代表性的植物性生物质如速生桉，甘蔗渣等，使用间歇型反应釜进行低压液化实验，寻求以廉价生物质资源为原料，低压，连续生产低氧生物原油的新途径。进一步考察加氢催化剂对获得的生物油进行脱氧的可行性，为低氧生物原油转变成的无氧燃料油提供科学依据。

本项目针对传统水热液化工艺中高温高压的条件导致工业化困难的问题，将四氢萘等供氢剂引入液化工艺中，以期待进一步提高液化效率，改善工艺条件。以纤维素、木质素、蔗渣，桉木屑等为原料，通过碱浸预处理，使用间歇型反应釜进行水热-溶剂热液化实验，考察了预处理条件，溶剂（水，四氢萘，乙醇，丙酮，苯酚），固液比，液化温度，时间和催化剂的添加等对液化过程压力及生物油生成的影响，进而探讨了不同溶剂的液化机理及液化反应动力学规律，寻求低压选择性生成低氧生物油的控制机制。（1）蔗渣，桉木屑的液化研究表明，与水作溶剂相比，四氢萘作为溶剂时，原料转化率和生物油产率更高。四氢萘液化需要较高的温度（280-300 ºC），而液化反应压力较低（低于2 MPa），操作条件更温和。碱浸预处理极大地促进了水作溶剂时的液化效率。（2）纤维素和木质素的液化研究表明，与水作溶剂相比，纤维素和木质素在四氢萘中液化均获得了较高的原料转化率和生物油产率；同时，纤维素和木质素在四氢萘中300 ºC液化1h，转化率分别为96%和65%，证明木质素较纤维素更难液化；（3）多种催化剂（NaOH、ZnCl2、ZSM-5，氧化铝）催化液化反应的研究表明，NaOH对提高水液化作用显著，而对四氢萘液化作用甚微，其他的催化剂均无显示明显的催化效果。（4）制备了高效的NiMo/r-Al2O3-beta-zeolite催化剂，以硬脂酸和废油脂作为生物油的模型化合物，在供氢剂（四氢萘）中进行催化加氢反应研究。在300 ºC，H2 压力0.8 MPa，反应2 h，硬脂酸转化率达到90%，液体产物中C15-C18的烷烃和烯烃含量达98%，异构组分含量达到40%；当H2压力增加至3 MPa，反应时间延长至3 h，废油脂转化率达到99%，产物组分与柴油相似，证明了生物油催化加氢制备发动机燃油工艺路线的可行性。