微波固相合成复合金属氧化物中高温煤气脱硫材料及其性能研究

Mid- and high-temperature desulfurization is the key technology for the highly effective and clean Coal utilization, such as IGCC and MCFC, and novel coal-based poly-generation systems of synthetic oil or alcohol/ether fuels. Research emphasis has been put on the preparation of desulfurization sorbents with high capacity, high efficiency, easy regeneration and good stability. Therefore, the research is of important theoretical value and practical significance. In this proposal, desulfurization sorbents are prepared by microwave-assisted solid-phase method in a one-step heating-calcination strategy, with iron oxide and zinc oxide as active components for mid- and high-temperature coal gas desulfurization, and with kaolinite and modified active coke as support. The crystal growth mechanism of metal oxide precursor under microwave irradiation is investigated using Coats-Redfern method, Ozawa method and the phenomenological theory for crystal growth kinetics,the key factors in the performance of desulfurizer is established, the micro-structure of desulfurizer is prepared with controllable and efficient method. Fractal theory, along with textural parameters such as specific surface area, pore volume and pore size distribution, is adopted to evaluate the desulfurization performance in a fixed bed reactor, including initial sulfur capacity, recycle stability and reactivity, and thus to discusses the microscopic nature of desulfurizer preparation process at molecular level, reveal the influence of texture on desulfurization performance in depth. This project would provide a theoretical basis and effective strategy for accurate design and preparation of mid- and high-temperature desulfurization sorbents with improved desulfurization performance.

中高温煤气脱硫是实现煤炭高效、洁净利用的关键，如何制备出硫容高、效率高，易再生又性能稳定的脱硫材料一直是研究的热点，其制备方法和相关机理的研究具有重要的理论意义和实用价值。本项目以氧化铁和氧化锌作为中高温煤气脱硫剂活性组分，以高岭土或改性活性半焦作为载体，采用微波固相合成法一步微波加热焙烧制备复合金属氧化物中高温煤气脱硫剂。采用Coats-Redfern法、Ozawa法和晶粒生长动力学唯象理论，揭示脱硫剂在微波辐射作用下金属氧化物活性组分的晶粒生长机理，确定影响脱硫剂性能的关键因素，实现脱硫剂微观结构的可控性制备；以分形理论并辅以比表面积、孔容、孔径分布等参数全面表征脱硫剂的微观结构特性；以初硫容、循环稳定性、反应性作为评价脱硫性能的指标，阐明脱硫剂结构与脱硫性能之间的内在关系；有望为提高中高温煤气脱硫剂脱硫和使用性能提供理论基础，为精确设计和制备中高温煤气脱硫剂提供一种合理高效的方法。

中高温煤气脱硫时实现煤炭高效、清洁利用的关键技术之一。本项目采用Coats-Redfern法和Ozawa法明确了氧化锌和氧化铁两者前驱体的热分解过程均遵循随机成核和随后生长机理；基于晶粒生长动力学唯象理论，得到了氧化锌、氧化铁、铁酸锌在微波辐射作用下晶粒生长活化能分别为70.7、30.4和122.1kJ•mol-1；在固定床反应器上，采用单因素实验或响应面优化方法，以硫容、循环稳定性、反应性作为评价指标，同时结合微波制备脱硫剂硫化前后的微观结构表征，明确了脱硫剂的构-效关系及其最佳制备工艺参数（活性组分含量、焙烧温度、焙烧时间）；明晰了不同金属氧化物活性组分之间的协同作用，同时发现新方法制备的脱硫剂不同活性组分之间的协同作用更显著；单纯以高岭土为载体的脱硫剂，脱硫剂的吸波性能较差，而加入少量半焦或将载体换成红土后的脱硫剂均适于在微波场中焙烧，且前种脱硫剂的硫化性能好于后者，但强度低于后者；发现了微波辐射在脱硫剂制备过程中的非热效应：1) 微波焙烧所得脱硫剂具有较小的活性组分晶粒尺寸和较多的孔结构，可为硫化反应提供较多的接触面积或反应空间；2) 微波辐射有利于脱硫剂内部的金属元素（Zn、Fe）向表面迁移，使脱硫剂表面金属元素含量多于常规焙烧所得脱硫剂；3) 微波焙烧所得脱硫剂表面金属（Zn、Fe）离子的路易斯碱性略强，有利于酸性气体硫化氢的吸附。上述结果为微波辐射固相合成法制备中高温煤气脱硫剂新方法提供了坚实的技术和理论支撑，同时为丰富微波在材料制备过程中的非热效应提供了理论线索。