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

Abstract

Temperature programmed oxidation (TPO) of H-gallosilicate (MFI) coked in the propane aromatization at 550°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° to 900°C at a linear heating rate of 20°C min^-1in a flow (50 cm³min^-1) of a O₂-He mixture (8.0 mol% O₂). 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.