Sulfur Oxides Removal – Heterogeneous

Abstract

This article describes the significant progress made in recent years in the development and fundamental understanding of catalysts for the reduction of sulfur dioxide by CO, synthesis gas, or methane. The direct catalytic reduction of SO 2 to elemental sulfur offers several advantages to power plants and industrial boilers using heavy fossil fuels, the main one being a simple process flowsheet for exhaust gas desulfurization with incorporated sulfur recovery. The environmental benefit is the recovery of sulfur in an innocuous form, which can be safely disposed of. Combined SO 2 /NO x removal can also be envisioned with such catalysts with ensuing overall system efficiency gains. Several high activity and high selectivity catalysts are presently available for SO 2 reduction by CO or syngas (CO + H 2 ), while under development are also catalysts for the reduction of sulfur dioxide with natural gas. These catalysts and the particulars of the associated SO 2 reduction processes are described in the article. Emphasis is given to catalysts based on cerium oxide which show promise for SO 2 reduction by either CO or methane, over a wide temperature window and in the presence of water and NO x . Mechanistic explanations are offered for the observed activity and selectivity of several of these catalyst compositions.