PEFTEC 2019 - Abstract

Abstract Title: High-precision sulfur and nitrogen concentration analysis in fuel and oil
Abstract Type: Oral
Session Choice: Analytical Techniques: Elemental Analysis and Speciation
Presenter Name: Dr Fabian Alt
Co-authors:Ms Almut Loos
Dr Lutz Lange
Company/Organisation: Elementar Analysensysteme GmbH
Country: Germany

Abstract Information :

Understanding the concentrations of sulfur and nitrogen in liquid materials are of critical importance in refining operations for two main reasons: regulatory purposes and process optimization. In most markets world-wide regulatory agencies, such as the Environmental Protection Agency (EPA), limit the total amount of sulfur and nitrogen in refined products for environmental reasons. As regulations push for cleaner fuels, greater pressure will be placed on manufacturers to better monitor pollutant materials such as SO2 and NOx. In addition, degradation of high cost catalysts utilized in refining processes happens much faster in the presence of high sulfur and nitrogen concentrations.

Accordingly, monitoring of these elements starts in upstream feed stocks, where concentrations in the high ppm range are typical. As these crudes get refined, measurements of how much S and N pass through catalytic reactors are carefully considered, maximizing the overall lifetime of catalysts. Downstream, these refined products will often be mixed with ethanol, further lowering the total S and N in final products. For the manufacturer to know the final concentrations it is imperative that analytical technology is capable of detecting such low levels.

High temperature combustion for the determination of sulfur and nitrogen is still the matter of choice if sensitivity really counts. No other method delivers equally sensitive, matrix-independent results. By means of UV fluorescence detection for sulfur and chemoluminescence for nitrogen determination, detection limits of as low as 10 ppb can be achieved.

Oil, fuel, diesel, and biofuel samples were analyzed with the trace SN cube of Elementar Analysensysteme GmbH for S and N. The samples were automatically injected. The results show that the S and N content of the samples could be determined with a very high precision, even for sulfur concentrations well below 1 ppm.

The reason of the high precision is that the trace SN cube works with two independent furnaces and combustion tubes. Thus, it is possible to adjust all parameters which may influence the results, such as temperature, injection volume, injection speed etc. of both channels completely independently. This results in an outstanding sample flexibility at always highest precision. Another well-known problem in high temperature combustion of oil and petrochemical samples is soot formation, caused by incomplete combustion. By using special developed accelerants, the oxidation process can be optimized dramatically.

Also, the known problem of interference in UV fluorescence detection by NO (higher N concentrations simulate too high sulfur contents) is solved by means of a unique N Excess module. SO2 is collected at an adsorption column and released after the decay of the signal caused by NO. This technique allows the precise determination of 0.1 mg / kg S in the presence of more than 100 mg / kg N.