Development of mixed-metal oxide catalyst on propane selective oxidation by using combinatorial chemistry

Abstract

Combinatorial methods are now being widely used to develop advanced functional materials for catalysis, fuel cell, polymers, electronic, sensors and display. When these exists a huge experimental variable space, millions of samples should be rapidly prepared, characterized and evaluated to find the quantitative structure-activity relationship (QSAR). Library work-up and library design should be done by data mining and artificial intelligence. Combinatorial synthesis and screening technique have been applied to investigate the catalytic activity and selectivity of quaternary mixed-metal oxide catalysts for the selective oxidation of propane. The 32-channel sequential/parallel fixed bed reactor system (SUPER-Ⅱ) was developed with all the operations were computer-controlled. The error in the flow in each channel was 1.5% and temperature distribution in each reactor was 1%. The catalyst libraries were prepared via a modified slurry method using a synthesis robot and library design software, and examined for the catalytic activities in the high-throughput reactor system connected to a mass spectroscopy and/or GC for product analysis. Several researcher reported that a proper Mo-V-Te-Nb metal composition alone can not guarantee the formation of an effective catalyst with the desirable structures and catalytic performance. Among the preparation methods examined, the formation of a solution, amount of solvent and aging of prepared precursor solution have effect on different crystal structure and morphology of catalysts. Quaternary Mo-V-Te-Nb oxide based catalysts with diverse chemical treatment have been selected for potential candidate by composition spread approach. In a next generation composition spread library the composition space of this quaternary composition has been sampled. Screening of this 32-member library provides substantial evidence that each quaternary system has its own state with optimum chemical treatment composition where acrylic acid formation is highest. At the first screening using mass spectrometer, some of the catalysts treated by $I_2$, $HIO_3$, $NH_4OH$ shows better catalytic activity. We conducted the single exprimental of propane oxidation over these catalysts and found that the Mo-V-Te-Nb oxide based catalyst treated by $HIO_3$ (pH 2.8) shows the highest yield to the desired product (acrylic acid) which was about 23%.