CHARACTERIZATION OF UNSATURATED HYDROCARBON CONTENT FROM LIGHT AND MIDDLE PETROLEUM DISTILLATES USING DESORPTION ELECTROSPRAY IONIZATION (DESI) MASS SPECTROMETRY

摘要

Chemical composition of petroleum products, ultimately the quality as well as physicochemical properties, depends on the source of the raw material and the process streams the product undergo. Therefore, fast, versatile and accurate determination of the hydrocarbon constituents is of significant interest. However, the determination of hydrocarbon content within petroleum products presents an analytical challenge because of the complexity of the sample, which contains a wide range of isomers of different classes of compounds. In the study presented here, desorption electrospray ionization (DESI), an ambient ionization method, is applied for the direct analysis of unsaturated hydrocarbons in unseparated complex petroleum mixtures. The detection of unsaturated compounds within petroleum products is achieved using DESI-high resolution mass spectrometry (MS) with a silver doped spray. While the silver ion forms adducts with several functional groups, it demonstrates a remarkable affinity for carbon-carbon double bonds. An addition of the silver ion to the hydrocarbon molecule spurs formation of a weak charge-transfer silver-adduct complex with olefin groups in unsaturated molecules. This affinity is used in the DESI MS analysis of naphtha and diesel fuel oil distillates to evaluate the type and composition of unsaturated hydrocarbons.