Deactivation of a coal liquefaction catalyst: Characterization by measurements of catalytic activity and catalyst physical properties

Abstract

Alumina-supported Co-Mo catalysts that had been used for liquefaction of Illinois No. 6 coal at 404°C, 171 atm, and weight hourly space velocity (WHSV) of 1.5 h −1 were characterized to provide measures of the deactivation. The intrinsic activities of the fresh and used catalysts were measured in catalytic flow microreactor experiments characterizing the simultaneous hydrogenation of phenanthrene, hydrodesulfurization of dibenzothiophene, and hydrodenitrogenation of quinoline at 350°C and 136 atm; rate constants estimated from the data for the individual reactions provided measures of the degree of activity loss. The catalysts were also characterized by X-ray photoelectron spectroscopy, surface area measurements, and chemisorption of NO. The catalytic reaction data showed that the catalyst retained about half of its initial hydrodesulfurization activity and about one fourth of its hydrogenation activity after operation in liquefaction for 31 days. There were substantial losses in catalyst surface area accompanied by accumulation of coal mineral components on the catalyst surface. The various data are qualitatively in agreement, but there is no single measure of the catalyst deactivation that is of general validity.