The effects of sulfur combustion products on particulate base metal vehicle emission control catalysts have been studied. Some of the factors controlling the degree and rate of deactivation of one type of UOP exhaust gas control catalyst, namely, copper-chromium alumina, are discussed. Data are presented which show how sulfur alters the chemical composition of these catalysts; how sulfur-poisoned catalysts may be regenerated in situ; and that low levels of sulfur accumulation on the catalyst are more detrimental to catalyst performance than small accumulations of lead or phosphorus. Under certain automotive operating conditions, sulfur poisoning can be minimized to the point that copper-chromium alumina catalysts offer the potential to meet 1976 EPA hydrocarbon and carbon monoxide standards for 50,000 miles. Emissions from a slave vehicle, using one such catalyst after prior use for 52,000 vehicle miles on fuel containing sulfur, were 0.34 and 3.16 grams per mile of hydrocarbon and carbon monoxide, respectively, using the 1975 EPA test procedure.Pollution from the internal combustion engine (ICE) is a problem that has concerned the automobile industry for many years. Such items as utilization of mechanical modifications (the PCV valve), manifold air injection, high air-fuel ratios, spark advance-retard, and exhaust gas recirculation (EGR) have reduced emissions from the ICE such that 1973 federal standards (Table I) for vehicle emissions for hydrocarbon (HC), carbon monoxide (CO), and oxides of nitrogen (NO*) have been met. With in tro-the HC and CO emissions from a Chevrolet Bel Air test vehicle using such catalysts increased rapidly, even after limited mileage accumulation, as shown in Table II.Initial evaluation of the physical and chemical analyses of used catalysts from vehicles (Table III) did not point to any single cause for this deactivation. Hence, detailed investigations of the effects of S, P, and Pb were initiated. This paper discusses the deleterious effects of sulfur combustion products on catalysts in vehicle exhaust environments, first reported by Hunter, 1972, and how these may be eliminated.
ExperimentalCatalyst Preparations. Copper-chromium alumina catalysts in the form of approximately %-in. diameter spheres were prepared conventionally from the metal salts and the composites calcined in a flowing stream of dry air at 6S0°C. Catalyst A, as prepared, has a copper-to-chrom-