95/00344 Biomimetic solubilization of brown coal by oxygenase model with hydrogen peroxide

Abstract

As an alternative processing of coal conversion, biosolubilization has been intensively studied. Most of the studies in 1980`s involve the oxidative solubilization of preoxidized coal or lignite to render the coal water soluble. The products contain primarily polycarboxylic compounds and are suggested to be of lower quality than the materials derived from conventional thermochemical conversion. Thus there has been arguments about the biological processes for the production of alternate fuels or chemicals from coal. Current reductive solubilization of coal under anaerobic conditions could provide more desirable products. On the other hand, these biological processes imply a potential route to liquefy coal catalytically under considerably mild conditions. The elucidation of mechanisms involved in the biosolubilization and the application of the catalyst systems in analogous to enzymes or microorganisms may offer an attractive processing for coal conversion. During the past decade, numerous studies on oxidation reaction catalyzed by synthetic metalloporphyrin have been reported. These catalysts have been synthesized as the models for cytochrome p450 and peroxidase, and some of them exhibit extremely high turn over number in the oxidations of alkenes and alkanes. To date the mechanisms of oxidation reactions catalyzed by synthetic metalloporphyrins are fairly well understood and the utilization ofmore » the catalyst for the oxidations of various stable compounds is of great interest. Preliminary attempt using a simple iron porphyrin complex for coal conversion, however, did not show a significant effect on the solubilization. In addition, the contamination of catalyst and residual oxidant affected the evaluation of the products. Therefore as the first step, we developed a new supported biomimetic catalyst capable of using hydrogen peroxide as an oxidant. In this paper we describe the solubilization of coal by the oxygenase model, immobilized iron porphyrin catalyst.« less