Natural gas is an important energy resource, accounting for 29% of the total energy consumed in 2017. Natural gas is composed predominantly of methane, but it can include other C<sub>2</sub> to C<sub>5</sub> hydrocarbons such as butane. It is used primarily as a fuel to generate electricity, and as feed stock for plastic materials. For more convenient storage and transportation, natural gas is often pressurized to a liquid state, known as liquefied petroleum gas (LPG). Fluorine, chlorine, and sulfur are a concern in LPG, but gas samples are not easily analyzed by ion chromatography. Pyrohydrolytic combustion coupled with ion chromatography (CIC) is an ideal approach to eliminate the sample matrix and increase sample homogeneity. A single 30-µL aliquot or multiple 30-µL aliquots of LPG were combusted under inert and oxygen gas aerated with water at 800 °C to 900 °C. Total fluorine, chlorine, bromine, and sulfur were determined by the pyrohydrolytic combustion and absorbed in 50 mg/L peroxide solution, whereas total iodine was absorbed in 50 mg/L peroxide, 1000 mg/L hydrazine solution. The resulting anions in the absorption solution (i.e. fluoride, chloride, bromide, iodide, and sulfate) were analyzed by CIC using either a large volume injection or after preconcentration of a larger sample volume. The anions were separated by anion-exchange chromatography and detected by suppressed conductivity. Both methods had good precision and sensitivity. The calibration curves were generated using incremental combustions of one standard. CIC allows an automated safe analysis of LPG samples for their fluorine, chlorine, bromine, iodine, and sulfur contents.

Determination of total fluorine, chlorine, bromine, and sulfur in liquefied petroleum gas by pyrohydrolytic combustion ion chromatography with large loop or sample preconcentration

ACS Fall 2020 Virtual Meeting

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