Catalytic reactions of products from the rapid hydropyrolysis of coal at atmospheric pressure

The catalytic reactions of hydropyrolysis tars from a subbituminous coal have been studied at atmospheric pressure in a two-stage reactor. The first stage consisted of a fluidized-bed reactor that produced hydrocarbon gas and tars at high particle heating rates. The gas and tars were separated from char and ash and passed to a second-stage fixed-bed catalytic reactor, packed with a NiMo/ γ-Al₂O₃ hydrotreating catalyst. It was found that interactions of the tars with the catalyst resulted in liquid products of increased volatility and lower heteroatom content but decreased total liquid yields due to gas formation, oxygen removal as water, and carbon laydown on the catalyst. Detailed analyses of the compositions of the liquid products showed that the catalyst was responsible for cracking reactions of long-chain aliphatic groups to light hydrocarbon gases and aromatization reactions that produce highly condensed polycyclic aromatic hydrocarbons.