Combinatorial Study of Zeolites in Catalyzing the Acylation of Benzene via Laser-Induced Fluorescence Imaging

Abstract

Laser-induced fluorescence imaging (LIFI) has been developed into a high-throughput screening (HTS) technique for heterogeneous catalysis. A laser beam is focused into a sheet parallel to the surface of the solid catalyst. Fluorescence from selected gaseous products formed immediately above the surface is imaged by a charge-coupled device (CCD) camera. Here, in situ LIFI was used to simultaneously screen the catalytic properties of a 15-member library consisting of mordenites (MOR), ferrierites (FER), ZSM-5 (MFI), zeolite γ-(gamma) (FAU), and beta zeolites (BEA) with various Si/Al ratios in the acylation of benzene with phthalic anhydride. Only beta zeolites were found to be active in this reaction over the temperature range of 190 to 340 °C. Substantial deactivation of beta zeolites was observed within less than one minute at higher temperature and the degree of deactivation varied with reaction temperature and the composition of the reactant mixture, as well as the Si/Al ratio of the beta zeolites. The deactivated beta zeolites can be regenerated partially by heating in a flow of oxygen. Up to 80% recovery of the catalytic activity was obtained. Similar recovery was observed after several deactivation–regeneration cycles.