Determination of total hydroxyls and carboxyls in petroleum and syncrudes after chemical derivatization by infrared spectroscopy

Article abstract of DOI:10.1021/ac00186a017

Oxygen-containing functional groups (hydroxyl and carboxyl) in fuels or crude oils, or fractions thereof, are determined by IR spectroscopy. The approach is based on chemical derivatization followed by measurement of IR bands of the corresponding derivatives. The chemical derivatization procedure involves two steps: (1) esterification of carboxylic acids with 2,2,2-trifluoroethanol and (2) acylation of alcoholic and phenolic hydroxyls with trifluoroacetyl chloride. The aryl trifluoroacetates absorb at 1800 cm^-1; the 2,2,2-trifluoroethyl esters absorb in the region 1760-1740 cm^-1. Variation of molar absorptivity of the derivatives as a function of structure is determined by using pure compounds and well-defined fractions from actual fuel samples.