The effect of the initial water of lignite on its liquefaction reactivity
In this paper, the effect of different initial water content of lignite on its direct liquefaction reactivity was studied. The results show that: initial water content in lignite can be used as hydrogen supplier and promote direct liquefaction reaction inducing higher total conversion rate, higher oil yield and lower pre-asphaltene / asphaltene yield, when the water content of lignite is of 20 ~ 30%. And the maximum of total conversion rate and oil yield is achieved 85.12% and 51.72%, respectively, when the water content of lignite is 25.33%. While the gas product yield and the pre-asphaltene /asphaltene yield is relatively lower, which is of 11.16% and 3.93%, respectively. This can be of practical significance to optimize the coal pre-treatment technology of direct liquefaction industry.
INTERACTIVE EFFECTS BETWEEN SOLVENT COMPONENTS : POSSIBLE CHEMICAL ORIGIN OF SYNERGY IN LIQUEFACTION AND COPROCESSING
The traditional mechanism for coal liquefaction ties liquefaction ability of a solvent with its scavenging ability and cannot explain synergistic effects between solvent components. Such effects are naturally anticipated by mechanisms that involve interaction between components to generate reactive components. This paper discusses three recent papers, in which beneficial effets of adding nondonor species to the donor solvent were reported, in light of the solvent-mediated hydrogenolysis model for coal liquefaction-a model we have previously proposed. The nondonor species, which in these cases are polycyclic aromatic hydrocarbons, are good acceptors of hydrogen and react with hydroaromatic donors to give cyclohexadienyl radicals, which are capable of engendering hydrogenolysis, thereby increasing the overall rates. The PCAH species also help minimize wasteful transfer of hydrogen that would otherwise lead to reduced but uncleaved products. In this case the beneficial effect is reflected in the efficiency of hydrogen utilization. Finally, we extend this line of reasoning to the context of coprocessing coals and heavy oils. We use semiquantitative estimates for the fate of aliphatic radicals in the presence and absence of PCAH components to suggest that the PCAH components provided by coals convert aliphatic radicals, which are ineffective in causing bond scission, into cyclohexadienyl radicals that can do so
LIQUEFACTION OF A SUBBITUMINOUS COAL WITH STEAM AND AMMONIA.
Liquefaction of coal with a solvent mixture of steam and ammonia was investigated. Concentrations of ammonia in the solvent mixture ranged from 0 to 30 wt %. Ammonia was found to catalyze the conversion of coal. The highest conversion for a Wyodak subbituminous coal was obtained with 2.5% ammonia at 400/sup 0/C and 750 psig. This conversion was 42.5 wt %, on a moisture- and ash-free basis (MAF), representing a 39% increase over the conversion obtained with pure steam at these conditions. The coal liquid obtained is enriched in hydrogen and has low molecular weight (number-averaged (M/sub n/) = 293, weight-averaged (M/sub w/) = 338.