Use of modified enzymes for the solubilization/liquefaction of bituminous coal in a fluidized-bed reactor

Abstract

Biocatalysts allow the solubilization/liquefaction of coal at nearambient temperatures. This research has focused on the chemical modification of enzymes to enhance their solubility and activity in organic media, and on optimal reactor design for a biocatalyst coal liquefaction process. Modification of hydrogenase and cytochrome c using dinitrofluorobenzene (DNFB) or methoxypolyethylene glycolp-nitrophenyl carbonate (PEG-n) has effected increased solubilities up to 20 g/L in organic solvents ranging from dioxane to toluene. Use of these modified enzymes in a small fluidized-bed reactor (with H₂ sparge) resulted in >40% conversion of bituminous coal in 24 h. Research using model compounds suggests that the conversion process may be in part owing to splitting at methyl or ethyl bridges, and perhaps saturation of ring structures. A new class of continuous columnar reactors will be necessary to achieve the high throughput and low inventory necessary for biocatalyst processes. The controlling mechanisms of particle transport in fluidized-bed systems using very small coal particulates are being studied. This has included the hydrodynamic modeling of coal segregation in fluidized-bed reactors, with direct microscopic visualization using fluorescence microscopy. A summary of our previously published work on enzyme modification and fluorescence visualization is presented.