Application of combinatorial catalysis for the direct amination of benzene to aniline

High-throughput synthesis and screening methods have been developed for the direct amination of benzene to aniline using solid cataloreactants as oxidants. The discovery libraries consisted of hundreds of samples in the primary screen, and arrays of 24 catalysts in the secondary screen. Catalysts were prepared in multi-well batch reactors and screened in parallel for catalytic activity using modified TLC detection and fast serial GC detection as primary screen and secondary screen, respectively. Around 25,000 samples were screened in about a year. Promising hits identified in the high-throughput screens were successfully scaled up and optimized in conventional autoclaves. Novel cataloreactant systems consisting primarily of a noble metal and a reducible metal oxide have been discovered. An optimized cataloreactant, Rh/Ni-Mn/K-TiO2 achieved a stable 10% benzene conversion and >95% selectivity to aniline at 300degreesC and 300 bar for a reaction time of about 2 h. Significantly, the cataloxidant can be regenerated repeatedly without a substantial loss of performance by reoxidation in air. (C) 2002 Elsevier Science B.V. All rights reserved.