Discovery from combinatorial heterogeneous catalysis: A new class of catalyst for ethane oxidative dehydrogenation at low temperatures

Abstract

Combinatorial methodologies are emerging as powerful tools in heterogeneous catalysis. Previously, we have established a strong correlation between catalysts prepared as thin films for high-throughput primary screening to those prepared in bulk for secondary screening in a multi-channel fixed bed (MCFB) microreactor for the ethane oxidative dehydrogenation process [Proc. Natl. Acad. Sci. U.S.A. 96 (1999) 11077]. Numerous catalysts with improved performance over literature compositions were also reported. With this high-throughput technology, tens of thousands of new compositions have been synthesized and tested. In this paper, we describe in detail the discovery of a new class of catalysts with extraordinary performance improvements. These catalysts contain Ni, Nb, and Ta or Co mixed oxides. The respective ternary systems were first screened in a thin film form (∼200 μg catalyst loading). Then they were scaled up to 50 mg level and screened in an MCFB microreactor. The optimal compositions were Ni 0.62Ta 0.10Nb 0.28O x and Ni 0.62Ta 0.20Nb 0.18O x . They convert 20.5% of ethane with 86.2% selectivity to ethylene and 20.0% of ethane with 86.1% selectivity to ethylene at 300 °C, respectively, as compared to 3.3% conversion of ethane with 82.9% selectivity to ethylene for the state-of-the-art catalyst Mo 0.72V 0.26Nb 0.02O x under identical testing conditions. One of these compositions, Ni 0.62Ta 0.10Nb 0.28O x , was further scaled up to 5 g and tested in a conventional bench scale reactor. The performance improvement is consistent with measurements made on the MCFB microreactor.