Temperature programmed oxidation of coked H-gallosilicate (MFI) propane aromatization catalyst: Influence of catalyst composition and pretreatment parameters

Temperature programmed oxidation (TPO) of H-gallosilicate (MFI) coked in the propane aromatization at 550 degrees C for a time-on-stream of 7-8 h has been investigated by measuring point to point the consumption of oxygen and also the formation of the both CO and CO2 (by GC analysis using a 16-loop gas sampling valve) during the TPO run from 50 degrees to 900 degrees C at a linear heating rate of 20 degrees C min(-1) in a flow (50 cm(3) min(-1)) of a O-2-He mixture (8.0 mol% O-2). The Si/Ga and Na/Ga ratios, calcination temperature, and hydrothermal pretreatments of the zeolite and also the presence of binder (silica or kaolin) in the catalyst have a strong influence on the TPO of coked zeolite. The influence is attributed to changes in the zeolite properties (viz., zeolitic acidity or framework Ga and non-FW Ga-oxide species), which affect the coke oxidation both directly and/or indirectly, by controlling the nature of coke formed during the coking process. (C) 1997 Academic Press.