| Combinatorial method is a very effective tool for discovery, development and optimization of a desired material. The method was applied to selective oxidation of propylene to propylene oxide (PO), which is one of the most essential feedstock in petrochemical industry. Direct oxidation of propylene by oxygen in gas phase was performed, in atmospheric pressure and at a temperature range of 150°C∼350°C, feed gas with 20,000 GHSV, 40% propylene, 10% oxygen, and balance helium. Most of the commercially available metals on the periodic table were impregnated on various support materials including alumina, ceria, silica, titania, and zirconia. Multi-metallic catalysts were also investigated, with varying compositions. Parameters to be optimized in this project include operating conditions, namely reaction temperature, feed gas composition and concentration, as well as catalyst properties, such as supported element and its loading level, and support materials. In the first stage, preliminary screening of the periodic table was performed, with discovery of some lead elements. PO yield and selectivity was significantly improved by addition of promoters, and the highest yield achieved was 5∼10 times as high as the original lead catalysts. Other than catalytic activity such as PO yield, propylene and oxygen conversion, and PO selectivity as parameters of investigation, activation energy, extent of combustion process, was examined as secondary information to evaluate the material and analyze the underlying mechanisms of the reaction. With progressive data collection and analysis through high-throughput screening, catalytic database concerning gas phase oxidation of propylene was established, starting from "scratch," where such comprehensive information was non-existent. From primary to secondary screening and to the last stage of optimization, the result had made revolutionary improvement, an order of a magnitude difference. |
