Speciation of Silicon Compounds in Fuel Gases


Some of the most damaging contaminants in naphthas, gasoline, other distillates, and biogas are silicon compounds, specifically siloxanes. Speciation of these compounds can be challenging using conventional GC/MS, requiring multiple standards and calibrations. Using GC–ICP–MS simplifies this process with the use of compound independent calibration (CIC) since a species respond on the basis of atomic concentration of silicon in the compound. Both sensitivity and selectivity are excellent when using appropriate tuning with either a single quad or triple quad instrument.

Silicon compounds, typically siloxane, present in naphtha, gasoline, biogas and other fuels are particularly offensive since they essentially form sand when the fuel is burned and subsequently damage engine parts due to their abrasive nature.

Some of the most damaging contaminants in naphtha, gasoline, and biogas are silicon compounds. In particular, siloxanes are the most significant offenders.


Characteristics of several common siloxane contaminants in naphtha, gasoline, and biogas

Compound Abb. Formula

Siloxanes are typically introduced to liquid fuels from silicon based anti-foaming agents used in the refinery process. If not well controlled and monitored they can crack and carry over through the refinery process and contaminate catalysts downstream or even end user’s engines ultimately.

Siloxanes make their way into landfill in large quanities in consumer products. They can be removed by filtration, but careful monitoring of the filters is critical to avoid breakthrough.

GC/MS has traditionally been used for this analysis, but the method requires calibration for each compound that might be present and will not detect silicon containing compounds that are not anticipated. GC–ICP–MS is much more specific, can be calibrated using a single silicon containing compound, and is nearly interference free by virtue of CIC capability.

Detection limits for silicon compounds are about 0.025 to 0.10 ppm by weight for liquid fuels and about 0.04 ppm molar for gas samples. Much lower detection limits for gases can be achieved by trapping and thermally desorbing gas phase samples.

Using state of the art GC–ICP–MS technology, CONSCI can achieve exceptionally low detection limits with excellent accuracy, linearity and reproducibility.


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