Use of Alumina-Coated Filaments in Catalytic Mufflers Testing with Single Cylinder Engine Robert J Leak, John T. Brandenburg, and Milton D. Behrens Texaco Inc., Beacon, N. Y. 12501.{ • A novel aluminu-,·oated metal mesh structure was used as a support for catalytic agents for the oxidation of hydrocarbons in automotive exhaust gas. The filamentary catalyst structures were evaluated in the exhaust stream of a single cylinder engine. Copper chromite on the alumina-coated mesh had the highest initial activity, but vanadia on the same support had the best resistance to lead deactivation. Phosphate and chromate filters on the alumina-coated mesh were elfective in trapping lead compounds and extending the life of the l'atalysts. The mesh with an adherent alumina coating had a much greater resistance to attrition in use than any conventional particulate form of catalyst.
T h e photolytic oxidation of hydrocarbons contributes to the formation of smog in some areas, such as the Los Angeles Basin (Air Pollution Foundation, 1954--1957). Both state and federal agencies have required installation of devices to reduce automotive hydrocarbon emissions to 275 p.p.m. and carbon monoxide to 1.5 volume":;;. Improvements in engine design have been made to burn the gasoline more completely, and hence to reduce the amount of hydrocarbon and CO expelled with the exhaust gas. Such engine modifications on some cars, and manifold air oxidation on others. have been certified to lower the hydrocarbon and carbon monoxide emissions to the legislated levels (Faith, 1966). Further mandatory reductions of emissions are anticipated, and may be achieved by catalytic oxidation. This paper reports initial testing of a novel alumina-coated filamentary structure which may have utility in catalytic treatment of exhaust gas.
coating had been deposited and calcined, is shown in Figures 1 and 2. Catalytic agents were dispersed on the alumina-coated mesh by conventional impregnation and drying procedures (Ciapetta and Plank. 1954). The volume of each cartridge was about 310 cc. In the work with filters two metal mesh cartridges, 5.1 X 7.6 em .. were formed, coated with alumina by autohydrolysis of alkaline aluminate, and calcined. Half was then impregnated with a filtering agent, and half with a catalytic agent. Test Procedure. A single cylinder CFR L-head engine was used as an exhaust gas generator for testing catalysts. A fuel with 2.2 cc. of tetraethyllead per gallon was used. The engine was operated at 1000 r.p.m. with an oxygen to hydrocarbon mole ratio of 12.6 (stoichiometric = 12.25). These conditions provided adequate oxygen for complete combustion of the hydrocarbon without the necessity of addiitg secondary air to the exhaust system. The catalysts were placed in a removable section of a 2-in
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Figure 4. Endurance runs with copper chromite and vanadium pent' oxide at stocc.
Endurance characteristic::. for a pho::.phate filter and copper chromite catalyst are shown in Figure 4. The activity star\ed at a lower level because only one-half the usual amo~nt of catalyst was present---i.e., the space velocity was increased by a factor of two. However, the endurance was better for:the half-filter half-catalyst system, which is attributed to reaction of the volatile lead compounds with the phosphate filter to form pyromorphite and other compounds; (Brandenb'urg and Leak, 1966). Similar protection of a vanadium pentoxide catalyst by a chromate filter is also shown in Figure 4. In most cases identification of compounds by x-ray ·diffraction patterns was difficult because of the fine disperSed nature of the phosphates and other compounds on the high area ~lu mina coating. However, pyromorphite was detected. Attrition Data. Several catalysts with a more conventional particulate form of spheres or pellets were tested_ and compared with the alumina-coated structures as su11'1:qtarize
