Microbially Formed Catalysts for Enhancement of Direct Coal Liquefaction

The present study examines the potential to biologically precipitate active catalytic compounds on the surface of coal particles in a water slurry. These compounds could be active forms of iron, an element abundant in coal, or active forms of molybdenum added as a soluble salt. The acidophilic microorganisms Thiobacilitis ferrooxida/ns and Acidianus brierlyi were added to a 5% coal slurry at a pH of 3.0 or less. Experiments were carried out for 21 days in shake flasks/automated fermentor at constant temperature and pH. Deposition of iron and molybdenum compounds on the particle surface was confirmed by several spectroscopic methods. After bio-treatment, the coal was removed by filtration and dried. A sample was then liquified in a bomb at 385°C in tetralin and hydrogen for 15 minutes. In some runs the sulfiding agent dimethyl disulfide (DMDS) was added to the mixture. Separation of the products was by soxhlet extraction. Total conversion, gas + oil + asphaltenes + preasphaltenes, of the pretreated coal was compared with the conversion of raw, untreated coal. Statistically significant increases in conversion were achieved for various pre-treatment methods. The maximum conversion achieved was with coal pre-treatment in the presence of Acidianus brierieyi and with the addition of 200 mg/1 of ammonium molylxlate to the slurry. Under these conditions, liquefaction of 2 separate runs, in the presence of DMDS, produced conversion of 78 and 81 %, This compared with 48% conversion for the raw coal under the same liquefaction conditions.