Professional Quality Control of Petroleum Products

Quality assurance of petrochemical raw materials and products is crucial. But how is quality measured? 

One important parameter to judge the quality of olefin containing organic material is the Bromine index. The coulometric method according to Karl Fischer shows how it can easily be determined.

Important quality criteria – The degree of unsaturation of organic compounds influences different specifications of the compound as viscosity, boiling point or the polymerization characteristics. It defines its tendency to form harmful gums that can clog fuel ports and filters e.g. How can the degree of unsaturation be determined? Bromine will react with double bonds under certain conditions. The more double bonds a molecule offers the more bromine is consumed in this reaction. The Bromine number is the amount of bromine in grams absorbed by 100 grams of a sample. The number indicates the degree of unsaturation. The Bromine number is determined by titration of the sample with a Bromide-Bromate (Br^-/BrO₃^-) solution. For lower Bromine consumption the result is given as consumption of mg Bromine per 100g sample and called Bromine Index.

Bromine Index – clean and elegant – A more clean, elegant and accurate determination of the Bromine Index is the coulometric method. Here the Bromine is not added in solution with a burette, but generated directly in the titration vessel by a current applied by an electrolysis cell. Fewer chemicals need to be handled and the current generates Bromine even more accurately than a typical burette could dose a solution. Typical industry samples are in the Bromine Index range of 2 to 50 for clean aromatic samples such as Benzene, Toluene, or Xylene. Raffinates, which are cracked hydrocarbons destined for gasoline, can be much higher, several hundred to several thousand. The METTLER TOLEDO Coulometer C30 determines the water content of a variety of sample of the petrochemical industry according to Karl Fischer. It also offers a dedicated method for the fast and accurate determination of Bromine Index. The control is fast for high Bromine Index values and cautious for small values. This allows accurate and reproducible determination of even low one-digit Bromine Indices. The simple method allows determinations without much method development, as the predefined method template can be applied. The solvent is blanked out and subsequent samples analyzed all with the same method.

…and in One Click™ – The One Click™ user interface offers direct access to all routine tasks. To start a method, run a sample or exchange the solvent One Click™ is enough. The clever design of the coulometric current electrolysis cell makes cleaning easy and offers highest accuracy. In order to empty and refill the titration vessel the Solvent Manager is simply activated by the titrator. Contact with chemicals is avoided. The C30 Coulometer supports you making sure your samples meet the specifications.