Volatile hydrocarbons in exhaust from alkylate-based petrol

Abstract

The non-methane hydrocarbon composition was studied for emissions from new alkylate-based fuels marketed for applications of special concern to human health and the environment. Proportions of 27 selected C2–C8 hydrocarbons were determined in moped exhaust for an alkylate-based fuel and a conventional reformate-based fuel. Samples were taken on an adsorbent cartridge behind the moped during driving, and were analyzed by thermal desorption and gas chromatography on an alumina column. About 90% of the hydrocarbons emitted from the two-stroke moped engine were unburnt fuel hydrocarbons. Benzene, alkylbenzenes and alkenes were virtually absent in the alkylate fuel, making it particularly advantageous for two-stroke and other engines with inefficient combustion. The proportions of combustion-formed hydrocarbons from the alkylate fuel were low for benzene, 1,3-butadiene and ethene and high for methylpropene, as compared with conventional petrol. The combustion products were similar for a lawn mower with a four-stroke engine. Their proportions are explained by the combustion chemistry of the major branched alkylate octanes. Low exposure levels of the genotoxic components benzene, 1,3-butadiene and ethene make the alkylate fuels especially favourable with respect to health for power saws, gardening machines and mopeds. Low emissions of alkenes and alkylbenzenes make them especially favourable with respect to photooxidant formation for outboard motors and other two-stroke engines used mainly in the critical spring and summer season.