gh SULFUR IN GASOLINE - ON-LINE ANALYSIS

The small device invented and developed by the St. Petersburg chemists can be easily hold in hand. It allows to perform real-time control of mercaptans content in petroleum derivatives - these sulfur compounds are extremely undesirable in gasoline.

In general, nobody likes these sulphur compounds. Besides, they reek - but fortunately, we rarely come across this property. More often they play mean tricks remaining unrecognized since even a small doze of these harmful substances is capable of corroding with time through insides of motor-cars, pipelines and practically any tanks coming into long contact with petroleum and petroleum refining products, including gasoline. Mercaptans - are actually a disguised acid, certainly it is not so strong as sulphuric acid, but it is unsafe for metals. Alas, these compounds are ususally available in petroleum and petroleum refining products, therefore, it is necessary to clean them from mercaptans and to control the refinement quality as precisely as possible.

So far, the mercaptan analysis in light oil, i.e. in gasoline and other types of petrol, has been performed manually. The procedure is in all cases labour-intensive and frequently not too precise either, because the most widespread method provides understated results. Samples always have to be selected to make analysis in the laboratory, so immediacy of this method can not be relied upon. That accounts for delayed response of production engineers: if mercaptans get suddenly multiple, and production engineers do not yet know about that, necessary measures will be taken late.

The technique developed by chemists of St. Petersburg State University jointly with colleagues from the EKROS Scientific Production Association (St. Petersburg) allows to perform such determination within several minutes. This can be done automatically, if required - in a literal sense without moving way from the pipeline. Chemists call such methods flow-injection ones, i.e. they allow to automatically select samples from the flow of analyzed liquid.

The "heart" of a new method is the so-called chromatography-membrane cell, which was designed by chemists under the guidance of Professor Leonid Moskvin. The cell combines main advantages of the two processes: chromatographic one (high efficiency of mass exchange) and the membrane division of substances (continuous mode of the process). It is in the cell that mercaptans meet with the special reagent flow, due to that they are distinguished from the gasoline stream and form a brightly coloured compound, the content of which is easy to determine - it's a trivial analytical task. This can also be done automatically.

It is interesting to note that for each determination the device requires four minutes and less than a tea-spoonful of gasoline. The analysis is so precise that it allows to determine mercaptans in tiny quantities - in millionth parts. Now production engineers will be able to learn about sulfur in gasoline practically instantly. So, they will be able to react in time by changing parameters of cleansing process.

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