生物质催化热解制备先进液体燃料中催化剂积碳行为及其调控研究

Biomass catalytic pyrolysis over zeolite catalysts with micropores is one of the most promising utilization technologies to produce advanced liquid fuels. However, there are some obstacles which limit its development, such as low target product yields and rapid deactivation of the catalysts because of coke formation. These problems are mainly relevant to the existing forms of carbon deposition on the catalyst. The carbon deposition in the pores of the catalysts forms the catalytic active centers (hydrocarbon pool) which determine the conversion efficiency of biomass to target products, whereas that on the surface of the catalysts would forms coke and result in deactivation of the catalysts. The carbon deposition behaviors of the catalysts is studied in this project, and then the formation of the hydrocarbon pool, its catalytic mechanism and evolution rules are investigated using isotopic tracing and molecular simulation and some advanced analysis methods. The relationship between the components of the hydrocarbon pool and product yields is disclosed. The carbon deposition kinetic models considering its source are built on the base of the above studies. On one hand, a good hydrocarbon pool is tried to form via carbon pre-depositing and the complex adjustments of compound compatibility and functional structure. On the other hand, some methods such as atomic layer deposition and liquid phase deposition are used to weak the acid sites on the outer surface of the catalysts, which can reduce the carbon deposition to form coke and enhance the target product yields and catalyst stability. Finally, the theory fundamention of carbon deposition behaviors and its regulation of the micropore zeolite catalysts in biomass catalytic pyrolysis to produce advanced liquid fuels would be built. The project also offers some scientific references for designing and preparing high-efficient and low-coking catalysts.

生物质在微孔沸石催化剂作用下热解制备先进液体燃料是最有前途的利用技术之一，但目前仍存在目标产物产率低，催化剂易于结焦失活等问题。这主要与催化剂的积碳形态有关：催化剂孔道内积碳形成的催化活性中心-"烃池"的好坏决定着生物质能否向目标产物高效转化，而表面积碳形成的结焦则会堵塞孔道导致其失活。本项目从催化剂的积碳行为出发，采用同位素示踪、分子模拟并结合多种现代分析方法研究烃池的形成、催化机理和演变规律，揭示烃池组分与产物之间的内在关联，构建包含积碳来源的动力学模型。提出一方面通过催化剂复方配伍和功能结构的络合调变以及高品质原料的预积碳优化孔道内"烃池"的组成，另一方面通过表面脱铝协同表面沉积方法弱化表面酸位点，减少结焦，实现提高目标产物产率和催化剂稳定性的研究思想。最终构建生物质催化热解制备先进液体燃料过程中微孔沸石催化剂积碳形成与调控的理论基础，为高效低结焦率催化剂的设计与制备提供科学参考。

催化热解一步法制取先进液体燃料是生物质最有前途的利用技术之一，但由于生物质中氧含量多，极易造成催化剂结焦失活，已成为限制生物质催化热解f发展的瓶颈问题。本项目重点研究催化剂的积碳行为和调控机制，探索高稳定、高活性、高效率催化剂的制备方法。通过三年的项目研究，取得如下重要成果：（1）积碳行为研究方面，改变了传统上认为积碳即为不好结焦的观念，创新性的将催化剂积碳分为对反应有利的活性积碳（反应后的实际催化中心）和引起结焦失活的惰性积碳（焦），并应用原位红外技术捕捉到不同反应物下催化剂活性积碳物种，并揭示了它们的微观形成机制，获得了积碳的演变规律，采用改进Froment模型和Coats-Redfem模型，建立了包含积碳的反应动力学模型，实现了对结焦过程的精准预测；（2）活性积碳优化方面，一方面，通过催化剂复方配伍络合调变，特别是添加活性组元，调控活性积碳形成孔道场所，发现Ga和Fe改性下的催化剂最好，目标产物产率提高20%，另一方面，提出采用能够形成优质活性积碳的原料预积碳，然后进行生物质催化热解的新思路，揭示了生物质和高品质原料共催化过程中C和H原子转移机理和协同作用机制，发展了生物质和废塑料、废弃油脂和醇类共催化热解体系；（3）惰性积碳抑制方面，分别采用化学液相沉积和表面脱铝两种方法对催化剂外表面酸位点进行钝化和部分脱除，改性催化剂在生物质热解中显著提高了烃类产物产率，大幅提升了抗结焦能力；（4）催化剂循环再生方面，对制备的抗结焦催化剂进行循环再生长时间运行实验研究，提出采用15%氧气/5%水蒸汽再生和再生后2%左右的催化剂积碳保有量（活性积碳为主）为最佳运行条件，以上研究为生物质高效转化为先进液体燃料奠定了理论基础，具有重要科学意义。本项目共发表高水平论文20篇（其中SCI 收录12篇，EI 收录13篇次，会议论文6篇，ESI高被引和封面文章各1篇），参编专著1部，参加国内外会议9次，培养研究生6名（其中博士1名），申请发明专利7件（授权4件），超额完成研究任务。