Automotive Hydrocarbon Emission Patterns in the Measurement of Nonmethane Hydrocarbon Emission Rates

Non-methane organic composition in the Lincoln Tunnel

“…Acetylene and m-xylene concentrations changed most significantly over the 12-year period. Very likely the significant change in acetylene concentration from 1970 to 1982 is due to the presence of catalyst-equipped automobiles and the reported preferential oxidation of the acetylene compound by the catalytic surface (9,21). However, the similar significant drop of m-xylene concentration over the 12-year period may have resulted from changes in gasoline compositions instead of selective catalytic oxidation.…”

“…Surprisingly the olefins fraction showed the least change over the 12-year period. A decreased olefinic fraction was expected since dynamometer studies of Black and High (9) and Jackson (10) reported low olefin levels from tailpipe emissions of catalyst-equipped vehicles. These researchers (9, 10) concluded preferential oxidation of the olefinic compounds by the catalytic surfaces.…”

“…The HC composition for catalytic-converter-equipped cars averaged 56.5% paraffin, 15.5% olefins, and 26.2% aromatic (10). Black and High's (9) results indicated large variation in percent paraffin, olefin, and aromatic composition for various types of control system devices, e.g., lean combustion and oxidation catalysts. Their data also show low olefin content in the exhaust of catalytic-converter-equipped vehicles.…”

“…Their data also show low olefin content in the exhaust of catalytic-converter-equipped vehicles. Both Black and High (9) and Jackson (10) reported significant decreases in percent acetylene contribution to HC totals for catalytic-converter-equipped cars. Acetylene percentages decreased from 7.9% to 2.2% (10).…”

“…Such drastic changes in vehicles and gasoline types are expected to have had a significant impact on vehicular tailpipe NMOC composition, likewise, on the NMOC compounds and sum of NMOC compounds to acetylene ratios. Indeed Black and High (9) and Jackson (10) have reported significant differences in HC composition between catalytic-converterequipped and -nonequipped automobiles from dynamometer simulations of roadway driving conditions. Jackson (10) reported an average HC for nonconverter-equipped cars of 33.4% paraffin, 26.6% olefin, and 32.1% aromatic.…”