Analysis of tert-butyldimethylsilyl derivatives in heavy gas oil from Brazilian naphthenic acids by gas chromatography coupled to mass spectrometry with electron impact ionization.

Naphthenic acids, C(n)H(2n+Z)O(2), are a complex mixture of alkyl-substituted acyclic and cycle-aliphatic carboxylic acids. The content of naphthenic acids and their derivatives in crude oils is very small, which hinders their extraction from matrixes of wide and varied composition. In this work, liquid-liquid extraction, followed by solid phase extraction with an ion exchange resin (Amberlyst A-27) and ultrasound desorption were used to isolate the acid fraction from heavy gas oil of Marlim petroleum (Campos, Rio de Janeiro, Brazil).

Identification of alkyl carbazoles and alkyl benzocarbazoles in Brazilian petroleum derivatives.

Carbozoles are important compounds in crude oils, as they may be used as geochemical tracers, being the major type of nitrogen compounds in petroleum. At the same time, they are regarded as undesirable due to the problems they may cause in the refining process, such as catalyst poisoning, corrosion, gum or color formation in final products. As separation and identification of carbazoles are challenging goals, this work presents a chromatographic method, made of a pre-fractionation on neutral alumina followed by the separation and identification of two classes of carbazoles using FeCl(3)/Chromossorb W and gas chromatograph with mass spectrometer (GC/MS) (SIM-single ion monitoring mode) analysis.

Ion-exchange resins in the isolation of nitrogen compounds from petroleum residues.

In this work, preparative liquid chromatography was used for the separation of the nitrogen compounds in a sample of heavy gas oil from a Brazilian petroleum. Initially it took place a pre-fractionation by neutral aluminium oxide and the compounds were separated in different classes such as: hydrocarbons, resins (compounds of low molecular mass and intermediate polarity) and asphalthenes (polar compounds with high molecular mass). A comparison of the fraction of resins was performed by re-fractionating with modified silica (with potassium hydroxide and hydrochloric acid), or with ion exchange resins (Amberlyst A-27 and A-15), being isolated the basic and neutral compounds, that were analyzed by GC-MS in the scan and selected ion monitoring modes.