Monocyclic and monoaromatic naphthenic acids: synthesis and characterisation

Abstract

Characterisation of the complex mixtures of carboxylic acids (naphthenic acids) occurring in crude oils and in degraded oil sands is environmentally important. Indeed some acids in waters from oil platforms are apparently hormonally active, and the oil sands acids are said to be toxic to a wide range of biota. Previous attempts to identify monocyclic and monoaromatic naphthenic acids have been hampered by the lack of authenticated synthetic reference compounds. Some studies have indicated that acids with ethanoic acid side chains are present in the naphthenic acids mixtures, so in the present study, we synthesised and characterised by mass spectrometry, a range (C 8-14 ) of monoaromatic and monocyclic ethanoic acids. Using 2-D comprehensive gas chromatographymass spectrometry, we then compared the retention times and mass spectra of the synthetic acids with those of a commercial naphthenic acids mixture. Some alicyclic and numerous aromatic acids were successfully identified.

Can two‐dimensional gas chromatography/mass spectrometric identification of bicyclic aromatic acids in petroleum fractions help to reveal further details of aromatic hydrocarbon biotransformation pathways?

“…resulted in highly resolved chromatograms allowing electron ionisation (EI) mass spectra containing molecular and fragment ions of many individual aromatic acids to be obtained. The aromatic fraction was dominated by a range of C 8 –C 16 alkylbenzoic acids (as methyl esters), reported previously, but a range of bicyclic mono‐ and diaromatic acids was also present. We now provide details of these identifications.…”

“…Examination of an aromatic NA fraction (F5) (as methyl esters) isolated from petroleum by Ag + SPE followed by GCxGC/MS in both nominal and accurate mass modes (cf …”

Occurrences and Behaviors of Naphthenic Acids in a Petroleum Refinery Wastewater Treatment Plant

“…The MDLs of the model compounds ranged from 0.7 to 15 ng/ L in wastewater samples and from 0.1 to 1.0 ng g −1 dw in suspended solid samples. Mass ions of 119 and 105 were selected for semiquantification of aromatic NAs relative to the surrogate (1-pyrenebutyric acid), 26 and percentages of aromatic NAs in total NAs were estimated assuming that the responses for NAs and aromatic NAs were similar to that of 1-pyrenebutyric acid in UPLC-QTOF-MS and GC-MS analysis, respectively. The data analysis including the calculation of mass flow, solid−water partition coefficient (K d , L/kg), and contribution of sorption and degradation to the removal of NAs in the plant is provided in the SI.…”

Identification of individual thiophene-, indane-, tetralin-, cyclohexane-, and adamantane-type carboxylic acids in composite tailings pore water from Alberta oil sands

“…Detailed studies by Rowland et al . have identified several cyclohexane‐type carboxylic acids in a commercial naphthenic acid mixture derived from petroleum.…”