Development and optimization of the siloxanes sampling from biogas matrix and the formation of analytical silicon specie

Katarina Hafner, Institute of Metrology of Bosnia and Herzegovina (BA)

Siloxane compounds are considered as one of the most relevant impurities in biogas matrices due to their affinity towards non-polar carbon species and the formation of abrasive SiO2 upon combustion. Silicone species and levels found in biogas matrices depend highly on the feed-stock and the surroundings during the production process. Information on total silicon content is however the most valuable input for normative documents prescribing desired quality of biogas through setting the maximum permissible values of the relevant impurities. Microwave plasma coupled with atomic emission spectrometer is proved to be a method of choice for the analysis of silicon extracted from gas samples. The conversion of organic silicon species into the form suitable for the analysis by application of atomic emission spectrometry, in this case hexafluorosilicate ion, presents a challenge. Biogas sample is passed through the series of impingers containing known amount of concentrated nitric acid. This conserving environment traps siloxanes for further derivatization step including neutralization with alkali hydroxide solution providing favourable environment for Si-O-Si skeleton cleavage and the addition of fluoric acid as a source of chelating fluoride ion. Derivatization is performed with close monitoring of pH value of the solution which is a critical parameter for monitoring the efficiency of derivatization because of the tendency of silicon to hydrolyze. The results of the studies on selected chain and cyclic siloxanes, as well as mixtures of the two are presented.


Pen Profile

From 2005 to 2011 active in the field of environmental protection in the laboratory for testing the quality of surface and ground water, soil and sediment by application of GC/FID, GC/ECD, GC/FPD, GC/MS, FTIR, AAS, UV-Vis, ICP/MS, etc. Since 2011 working as an expert advisor and QA manager in the Department of Chemistry of Institute of Metrology of Bosnia and Herzegovina using various instrumental techniques such as gas chromatography, atomic emission spectrometry, fluorescent X-ray spectrometry, etc. Active in the field of testing the quality of liquid and gaseous fuels by establishing a method for testing the composition and contaminants. Worked as RMG at VSL at EMRP JRP Characterisation of energy gases for 6 months. Work within JRP ENG54 Biogas project on the total silicon measurement in biogas matrices.

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