A Study on the Coking Sites of γ-Alumina Surface Using 1-Methylnaphthalene as the Model Reactant

The support gamma-Al2O3 was treated with 1-methylnaphthalene as the model reactant by respectively using the chemical static adsorption method and the accelerated coking method to study the coking sites of gamma-Al2O3 surface. The carbon species formed on gamma-Al2O3 surface were analyzed by CAT-CS, TG-MS, IR-OH, and Py-IR techniques. The results of characterization by CAT-CS and TG-MS techniques indicated that the carbon species formed during the chemical static adsorption process is mainly composed of the reversibly adsorbed coke precursors with a lowly-condensed state, while that formed after the accelerated coking process is probably related with the irreversibly adsorbed coke deposits with a highly-condensed state. The results of characterization by IR-OH and Py-IR techniques further implied that the formation of the two kinds of carbon species, i.e., coke precursors and coke deposits, are closely related with the basic hydroxyl groups and the strong Lewis acid sites on gamma-Al2O3 surface. The results lead to a deep insight into the coking mechanism on the alumina surface.