Evaporative and exhaust VOC emission profiles from gasoline vehicles in Mexico

摘要

As a result of the opening of the gasoline market to foreign companies in Mexico at the beginning of 2018, the composition of VOCs emissions from gasoline vehicles has changed and the Ministry of Science and Technology of Mexico City (SECITI) granted a research to determine the new VOCs emission profiles from gasoline vehicles. 20 samples of VOCs collected with canisters and 28 different headspace samples of gasolines expended in the city were analyzed by gas chromatography. Exhaust emissions from tunnels were composed in average by 67% of alkanes, 17% of aromatics, 12% of olefins and 4% of acetylene and the most abundant compounds were propane, butane, isopentane, ethylene and toluene. Evaporative emissions compositions of different gasolines were 18% of alkanes, 6% of aromatics, 15% of olefins and the most abundant VOCs were isopentane, 2-methylpentane, n-pentane, 4-methyl-c-pentene-2 and n-butane. Highest variation among different gasolines vapor were for isopentane which content was from 12% to 31% in magna gasoline, for 2-methylpentane from 9.2% to 19.8%, and n-butane which varied from 1.6% to 4.7%. Gasoline premium presented higher variation among different gasoline brands, mainly with branched alkanes. VOC compositions of gasoline has changed in the last 20 years since content of aromatics diminished from 26% to 17% as well as VOC unsaturated content from 24% to 16% which is important to reduce the photochemical reactivity for ozone formation. These new profiles can be used to feed photochemical models.