Effects of Hydrocarbons, Carbon Monoxide, and Oxygen on Sulfuric Acid Emission from an Automotive Catalyst

Abstract

The results of a flow reactor study of the sulfur dioxide oxidation over a 1975 production Pt/Pd monolithic catalyst are described. The effects of catalyst temperature, space velocity, oxygen concentration, sulfur dioxide concentration, and feedgas composition have been studied. The sulfur dioxide oxidation is kinetically limited below approximately 475 °C and approaches thermodynamic equilibrium at higher temperatures. In the kinetically limited region and in the absence of reducing gases, sulfur dioxide conversion is relatively independent of oxygen concentration (~0.01-5% O2). When the reducing gases, carbon monoxide, propylene, or hydrogen, are present, they are oxidized more readily than sulfur dioxide and hence serve to inhibit its oxidation at oxygen concentrations of less than ~1.0%. There is a range of oxygen concentrations which gives high conversion of carbon monoxide and propylene simultaneously with low conversion of sulfur dioxide. Catalyst aging causes significant reductions in sulfur dioxide oxidation activity while still maintaining moderate to high carbon monoxide and propylene oxidation activities.

Sulfate and particulate emissions from an oxidation catalyst equipped engine

“…Mikkor et al (18), Hammerle and Mikkor (19), and Hammerle and Truex (20) also measured sulfur conversion. Their data are not included here because instead of an engine they used a simulated exhaust system.…”

Reaction of sulfur oxides with alumina and platinum/alumina

“…It has now become evident that treatment of drinking and wastewaters with chlorine leads to the formation of a variety of organochlorine compounds. Chloroform (CHC13), other haloforms, chlorinated phenols and phenolic acids, and chlorinated quiñones, benzoic acids, and heterocyclic com-pounds are only a few of the many structural types which have been identified (1)(2)(3)(4). Much of the organically bound chlorine has not been fully characterized; a large fraction is associated with macromolecular organics (5).…”