Heat-exchanger deposits in an inverted steam-assisted gravity drainage operation. Part 2. Organic acid analysis by electrospray ionization fourier transform ion cyclotron resonance mass spectrometry

As a complement to the bulk analyses presented in part 1 (Jennings, D. W.; Shaikh, A. Energy Fuels 2007, 21, 176-184), we report detailed compositional analysis of the organic acids from heat-exchanger deposits and produced water from an inverted steam-assisted gravity drainage (SAGD) bitumen production process. The current analyses were performed by ultrahigh-resolution negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry [(-) ESI FT-ICR MS] and reveal distributions of molecular weight, heteroatom content, aromaticity, and carbon number for several thousand organic acids in each sample. High mass accuracy combined with Kendrick mass defect analysis allows for assignment of a unique elemental composition, CcHhNnOoSs, to each mass spectral peak. Three-dimensional mass spectral images generated from the molecular formulas reveal compositional differences that may be rationalized on the basis of sample processing. In particular, we report lower overall heteroatom content, higher average carbon number, and lower aromaticity for early stage deposits and the produced bitumen compared to later stage samples that show increased water solubility. Little was previously known about those species other than the presence of organic acid/acid salt functionality. Moreover, we report the first in vacuo isolation and tandem mass spectrometry of individual components of petroleum mixtures. Tandem mass spectrometry by infrared multiphoton dissociation of trapped ions indicates dicarboxylic acid structures for predominant CcHhO4 and dicarboxylic acid structures with thiophenic sulfur for predominant CcHhSO4 species. In this manner, we provide a highly detailed landscape for the organic acid content of inverted SAGD heat-exchanger deposits, to further illuminate the nature of fouling in those systems.