Determination of hydrate inhibitor in crude oil by nanoextraction–gas chromatography

Abstract

This work focused on the quantitation of methanol as a hydrate inhibitor in crude oil. The novelty is nanoextraction of a polar compound from a complex non-polar matrix and selection of the proper fiber with maximum selectivity, loading percent, and lifetime. This approach not only does not require specific instrumentation, such as multiple columns and selective detectors, but also has eliminated the use of organic solvent and avoids the insertion of water inside the GC columns. The objective is optimization of extraction conditions, GC adjustments, and data processing. Experiments were conducted on the real sample of Iranian offshore crude oil by a carboxen/PDMS fiber via GC equipped with a cross-linked polyethylene glycol column and flame ionization detector. The results revealed that this fiber adsorbed the alcohols among other light non-polar compounds of crude oil. Moreover, the interference effects of ethanol were solved by proper selection of the thermal program. The LOD, LOQ, and linear range of this approach were determined to be 3.9, 12.9, and 14-229 ppm for methanol, respectively. Using the standard calibration and the standard addition methods, the relative errors of 1.6-7.2 and 5.3-14.0% were determined.

Quantitative measurement of Mono-Ethylene Glycol (MEG) content using low-field Nuclear Magnetic Resonance (NMR)

“…The ability to use low-field NMR to determine MEG concentrations within 1 wt% accuracy over a range of concentrations improves upon the errors associated with the current onsite monitoring techniques of FTIR (5%) (Shoukat et al, 2019), and Velocity and Conductivity (2-3 wt%) sensors (Sandengen and Kaasa, 2006) (note these studies were performed under comparable ambient temperature conditions to the experiments presented here). Whilst its accuracy has been demonstrated to be comparable to that of Gas Chromatography (1 wt%) (Mokhtari and Pourabdollah, 2012) in the presence of an array of impurities, benchtop NMR spectrometers have the advantage of being easily transportable which facilitates on-site monitoring of samples. The improvement in concentration measurement accuracy may translate to an improvement of MEG re-injections by the same factor.…”