Environmental Catalysis: Gas Phase Hydrodechlorination of Chlorophenols

本提案提出了一项基础研究，其重点是探索催化加氢脱氯活性/选择性与催化剂结构之间的联系。PI先前的工作已经确定，在氢存在的情况下，纳米分散镍在无定形二氧化硅上对高浓度氯化气流的脱氯非常有效；被除去的氯仅以易于捕获的HCl形式存在。现有的催化剂活性/选择性数据库将以战略方式加以扩展，重点放在氯化苯酚作为模型反应物的处理上；后者代表了一类具有商业意义和剧毒的工业废物。初步结果表明，氯苯和氯酚在Ni/SiO2上的加氢脱氯是结构敏感的，较大的Ni颗粒（在1 ~ 4 nm范围内）具有较高的特定脱氯率，但更容易失活。催化剂衰变的问题将通过反应前后催化剂表征的综合方案来解决。这将涉及体结构研究（x射线衍射），高分辨率透射电子显微镜（TEM），分析TEM（包括EDX和EELS），表面积/孔隙度测量，化学吸附/TPD/TPO研究和x射线光电子能谱来探测Ni电子结构的变化。此外，反应物/生成物与催化剂表面相互作用的性质将使用光谱（FTIR-DRIFT）和色谱技术进行探测。工业废水中存在的氯化芳烃现已被确定为环境污染的主要来源。这项工作可以为更有效的污染预防方法奠定基础。PI以前曾在国际背景下与研究生和本科生合作。在这个项目中，他还将与化学专业的学生一起工作，并提供工程研究方面的培训。

This proposal sets out a fundamental study that is focused on probing the link between catalytic hydrodechlorination activity/selectivity and catalyst structure. Previous work by the PI has established that nano-dispersed nickel on amorphous silica in the presence of hydrogen is highly efficient in the dechlorination of concentrated chlorinated gas streams; the chlorine that is removed is solely in the form of HCl that is easy to trap. The existing catalyst activity/selectivity database will be extended in a strategic fashion, focusing on the treatment of chlorinated phenols as model reactants; the latter represents a class of commercially significant and highly toxic industrial waste. Preliminary results have revealed that chlorobenzene and chlorophenol hydrodechlorination over Ni/SiO2 is structure sensitive in that larger Ni particles (in the range 1-4 nm) exhibit higher specific dechlorination rates but are more susceptible to deactivation. The issue of catalyst decay will be addressed through a comprehensive program of catalyst characterization before and after reaction. This will involve bulk structural studies (x-ray diffraction), high-resolution transmission electron microscopy (TEM), analytical TEM including EDX and EELS, surface area/porosity measurements, chemisorption/TPD/TPO studies and x-ray photoelectron spectroscopy to probe changes in Ni electronic structure. Moreover, the nature of the reactant(s)/product(s) interaction with the catalyst surface will be probed using spectroscopic (FTIR-DRIFT) and chromatographic techniques. The presence of chlorinated aromatics in industrial effluent is now established as a major source of environmental pollution. This work may form the basis for a more efficient pollution prevention method. The PI has previously worked with both graduate and undergraduate students in an international context. In this project he will also work with chemistry students and provide training in engineering research.