Tiwari Garima, Sharma Gunjan, Verma Rishi, Gakhad Pooja, Singh Abhishek Kumar, Polshettiwar Vivek, Jagirdar Balaji R
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560 012, India.
Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, 400 005, India.
Chemistry. 2023 Nov 13;29(63):e202301932. doi: 10.1002/chem.202301932. Epub 2023 Oct 4.
A reaction of fundamental and commercial importance is acetylene semi-hydrogenation. Acetylene impurity in the ethylene feedstock used in the polyethylene industry poisons the Ziegler-Natta catalyst which adversely affects the polymer quality. Pd based catalysts are most often employed for converting acetylene into the main reactant, ethylene, however, it often involves a tradeoff between the conversion and the selectivity and generally requires high temperatures. In this work, bimetallic Pd-Zn nanoparticles capped by hexadecylamine (HDA) have been synthesized by co-digestive ripening of Pd and Zn nanoparticles and studied for semi-hydrogenation of acetylene. The catalyst showed a high selectivity of ~85 % towards ethylene with a high ethylene productivity to the tune of ~4341 μmol g min , at room temperature and atmospheric pressure. It also exhibited excellent stability with ethylene selectivity remaining greater than 85 % even after 70 h on stream. To the best of the authors' knowledge, this is the first report of room temperature acetylene semi-hydrogenation, with the catalyst effecting high amount of acetylene conversion to ethylene retaining excellent selectivity and stability among all the reported catalysts thus far. DFT calculations show that the disordered Pd-Zn nanocatalyst prepared by a low temperature route exhibits a change in the d-band center of Pd and Zn which in turn enhances the selectivity towards ethylene. TPD, XPS and a range of catalysis experiments provided in-depth insights into the reaction mechanism, indicating the key role of particle size, surface area, Pd-Zn interactions, and the capping agent.
具有重要基础意义和商业价值的一个反应是乙炔半加氢反应。聚乙烯工业中使用的乙烯原料中的乙炔杂质会使齐格勒-纳塔催化剂中毒，从而对聚合物质量产生不利影响。钯基催化剂最常用于将乙炔转化为主要反应物乙烯，然而，这通常涉及转化率和选择性之间的权衡，并且一般需要高温。在这项工作中，通过钯和锌纳米颗粒的共消化熟化合成了由十六烷基胺（HDA）包覆的双金属钯-锌纳米颗粒，并对其进行乙炔半加氢研究。该催化剂在室温和大气压下对乙烯表现出约85%的高选择性，乙烯生产率高达约4341 μmol g⁻¹ min⁻¹。它还表现出优异的稳定性，即使在连续运行70小时后，乙烯选择性仍保持大于85%。据作者所知，这是室温乙炔半加氢的首次报道，该催化剂在所有已报道的催化剂中，能实现大量乙炔转化为乙烯，同时保持优异的选择性和稳定性。密度泛函理论计算表明，通过低温路线制备的无序钯-锌纳米催化剂的钯和锌的d带中心发生了变化，这反过来提高了对乙烯的选择性。程序升温脱附、X射线光电子能谱和一系列催化实验为反应机理提供了深入见解，表明了粒径、表面积、钯-锌相互作用和包覆剂的关键作用。
