碳基非金属催化乙炔法制氯乙烯的基础研究

The industry of vinyl chloride synthesis via acetylene hydrochlorination faces significant challenges because of environmental pollution and deficiency in mercury resources, which is currently used as the catalyst in industry. Therefore, this project proposes to design and develop a non mercury catalyst based on heteroatom doped carbon materials. Our previous research and knowledge about carbon catalytic materials has laid a good basis for this proposal. The project will set out developing techniques for controlled synthesis of carbon materials selectively doped with specific structured heteroatoms or predominant with a specific doping structure. Using these materials as model catalysts, we will investigate the modification effects of these heteroatoms with different structures on the electronic structure of carbon materials, and further on the catalytic conversion of acetylene to vinyl chloride. Experimentally, special attention is paid to the development of in situ characterization capability for carbon materials and corrosive reaction systems with soft X-ray absorption spectroscopy. Theoretical simulations are to be carried out, helping to understand the modulation effect of the electronic structure of carbon materials on catalysis from molecular level. Furthermore, we intend to bring the research achievements from fundamental studies into practice. By using commercial SiC materials as substrates, which are easy to shape and possess good heat conductivity and mechanical strength, we explore fabrication of heteroatom-doped C-SiC catalysts. This will help realizing the goal of vinyl chloride synthesis with no mercury.

本项目针对目前乙炔法制备氯乙烯行业所面临的环境污染和汞资源匮乏的双重压力，利用本组前期关于碳催化方面的研究积累和基本认知，提出设计研制杂原子掺杂的碳基非金属催化剂，用于氯乙烯合成。针对本领域的难点，拟从创建具有特定构型或者特定构型占优的杂原子掺杂碳材料的制备方法入手，并以此为模型催化剂，研究不同构型杂原子对碳层电子结构的调变作用，及其催化氯乙烯合成的作用机理。实验方法上，注重发展适合于碳材料和腐蚀性反应体系的同步辐射软X-射线吸收谱原位表征技术等，并结合理论计算，从分子水平理解碳材料电子结构调控催化反应的原理，丰富碳催化的基础理论，努力在本领域形成影响。进一步，与实际应用相结合，拓展基础研究成果，以具有易成型、高导热性、化学稳定和机械稳定性的SiC为基底，力争创制出高效、稳定的杂原子掺杂C-SiC实用催化剂，以进一步推进乙炔制氯乙烯无汞化生产的目标。

针对目前乙炔法制氯乙烯行业面临的环境污染和汞资源匮乏的双重压力，本项目开发了两类无汞非金属的催化剂，一类为氮掺杂的碳催化剂，分别以SiC为基底的类核壳结构的氮掺杂纳米碳催化剂以及以生物质为原料制备的氮掺杂碳小球催化剂，另一类催化剂是与石墨烯类似的二维片层结构的多孔氮化硼催化剂。这两类催化剂均表现出优异的催化活性和氯乙烯选择性，其中多孔氮化硼催化剂在稍高温度（280 ºC）下表现出更优的活性和稳定性，在优化条件下乙炔单程转化率和氯乙烯选择性均为99%，1000小时后转化率仍保持95%，选择性不变，具有一定的应用前景。更重要的是，从材料制备入手，合成出了一种或两种结构氮物种占优的氮掺杂碳材料作为模型催化剂，通过多种表征手段包括XPS、红外光谱、拉曼光谱、电子显微镜等，结合理论计算，对氮掺杂碳基催化剂的催化作用机理进行了深入研究。对碳氮基催化剂的工业应用进行了前期探索，包括催化剂的放大制备，利用企业现场气对催化剂进行了1000多小时的反应性能评价，取得了一定成果；研究了这两类非金属催化剂的稳定性和失活原因，并依此开发了简单的再生方法。本项目取得的研究成果为无汞催化剂的设计、实现氯乙烯绿色合成提供了一条新思路。