Two-ring aromatic compounds were used to study catalytic hydrogenation, In the absence of coal, conventional supported catalysts resulted in higher levels of aromatic hydrogenation than unsupported (or dispersed) catalysts, In the presence of coal, the catalytic hydrogenation of the aromatic model compound is suppressed, The net result is that the catalytic hydrogenation activity and coal conversion are similar for supported and unsupported catalysts. The suppression appears to be due to a combination of competition with coal and poisoning of the catalyst. Poisoning is inferred from the results that indicate that suppression of catalytic activity is observed even after coal is removed from the system.