Properties of Automotive Exhaust Gases

In the major catalytic processes of the petroleum and chemical industries, continuous and steady state conditions are the rule where the temperature, pressure, composition, and flow rate of the feed streams do not vary significantly. Transient operations occur during the start-up of a unit, usually occupying a small fraction of the time of a cycle from start-up to shut-down for maintenance or catalyst regeneration. 

Automobiles vary enormously in their weight from 2500 to 5500 lb, which requires an engine displacement from below 100 to above 500 cu. in. In a similar driving schedule, a 5000 lb car will emit nearly twice the 

The ideal exhaust gas composition is given in Table II, based on a fuel with an H to C molar ratio of 2.103, and assuming that the equilibrium is established and frozen at 4000°R 25). To complete the combustion in a rich exhaust, secondary air must be supplied to cover the deficiency in oxidants. 

Various aldehydes, alcohols, esters, and ketones are also found in exhaust gases, at concentrations up to several hundred parts per million. Formaldehyde and acrolein are outstanding eye irritants in the raw exhaust gases 

The oxidation reactions of hydrogen, carbon monoxide, and hydrocarbons in the temperature range of 500 to 1500°F, where the catalytic reactors can be expected to operate, are all favored thermodynamically to 

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