Catalytic conversion of chlorite to chlorine dioxide using water-soluble heme and non-heme manganese complexes
The chlorine oxyanions (ClOn-, n = 1-4) spanning oxidation states of +1 to +7 have found diverse uses over several decades as oxidants. Their uses range from making bleaching agents to propellants used in rocket fuels. The chlorine oxyanion of interest herein is chlorite (ClO2-) where the oxidation state of chlorine is +3. This oxyanion is used for the production of ClO2 in the pulp bleaching industry; however, chlorate is preferred for cost reasons (e.g. less corrosive conditions and byproducts). Therefore a catalytic method for the production of chlorine dioxide from chlorite is of interest from an industrial standpoint. Originally, the goal of the chlorite project was to synthesis a small molecule mimic of an enzyme known as chlorite dismutase that converts chlorite to dioxygen and chloride. This is explained in depth in the first chapter. The second chapter herein describes the synthesis of a water-soluble manganese heme complex and its catalytic activity for chlorite conversion to chlorine dioxide as opposed to dioxygen in ambient conditions. The conversion is; however, not simply to chlorine dioxide as chloride and chlorate are also formed over the course of the reaction. Detailed kinetics and a proposed mechanism for this transformation are presented within this chapter. The third chapter herein describes the catalytic activity of two water-soluble manganese non-heme complexes for chlorite conversion to chlorine dioxide as opposed to dioxygen. This chapter highlights the fact that porphyrin is not necessarily unique to this transformation. The postulated formation of oxidized buffer offers a new direction for future studies. Detailed kinetics and a proposed mechanism for this transformation are presented within this chapter. The final chapter expands upon the use of peroxyacetic acid as an added oxidant when using the water-soluble manganese heme complex. Here the rate of conversion and yield of chlorine dioxide are greatly increased as a result of the rapid formation of the active catalyst. Detailed kinetics and a proposed mechanism for this transformation are presented within this chapter.
Abu-Omar, Purdue University.
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