Reactions in High-Temperature Aqueous Media

Mechanisms leading to process improvements in lignite liquefaction using CO and H2S

The effect of alkali metal carbonate catalysts on the liquefaction of Victorian brown coal using carbon monoxide and steam

Fe(CO)5-sulfur-catalysed coal liquefaction in H2OCO systems

Hydrogenolysis of coal-related model compounds by carbon monoxide-water mixture

Hydroliquefaction is a well-known technique for coal liquefaction. Work with carbon monoxide, however, showed unexpectedly high liquefaction activity and indicated that the presence of both hydrogen and carbon monoxide (as in synthesis gas) could lead to improved liquefaction, particularly for low rank coals. The objective of the work reported here was to develop a better understanding of the chemistry of liquefying coal with synthesis gas plus water and to assess the potential of such a process. The effects of changing gas composition, temperature, pressure, solvents, catalysts and coal types were studied to better understand the process fundamentals and to lay the groundwork for studies in continuous reactors on a larger scale. A variety of coals were converted in batch autoclaves to a low-sulfur fuel oil at temperature of 425 to 450/sup 0/ C and pressures of 2200 to 2400 psig, using 1:1 (H/sub 2/:CO) synthesis gas at reaction times of 30 to 60 minutes at temperature. Although early work suggested that lignites could be readily liquefied without added catalytic agents, later experiments showed that a greatly improved product could be obtained by adding pyrite, which is normally present only in small amounts. Pyrite or, in particular, its reduction product pyrrhotite,more » appear to be important catalysts for coal liquefaction, and, in general, the reactivity of coals correlates well with the pyrite (or iron plus sulfur) content. An important consideration is the optimum temperature for reacting carbon monoxide or its (catalytic) intermediates with coal. This temperature is below 400/sup 0/C, and it is necessary to allow for some reaction time between 380 and 400/sup 0/C. Finally, coal liquefaction with synthesis gas appears to be compatible with the type of processing used to produce Solvent Refined Coal or SRC-II.« less

Coal liquefaction with synthesis gas

Lignite may be hydrogenated to a Jow-sulfur, low-ash, heavy fuel oil in the absence of added catalysts by use of synthesis gas and the moisture in the coal as the reducing agent. Conversions of 90-94% and oil yields near 60% (moisture, ash-free basis) have been obtained routinely at temperatures of 425-450°C and pressures of 3000-4000 psig. These conversions and oil yields are higher than those obtained with hydrogen at the same conditions. The effectiveness of carbon monoxide in hydrogenating lignite is, in part, due to the presence of the carbonates of the alkali and alkaline earth metals which react with carbon monoxide, in the presence of water, yielding formates, the active reducing agents.

E. C. Moroni

Papers

Coal liquefaction with synthesis gas

Hydrogenation of lignite with synthesis gas