Presentation Profile
ASTM D1159 Bromine Number – Proposed Back Titration
Currently Scheduled: 10/11/2023 - 1:30 PM - 2:30 PM
Room: Bluebonnet
Main Author
Alan Cummings - Lummus Technology
- Tore Fossum - Tor Systems
Abstract:
Bromine number is used to measure the aliphatic unsaturation in petroleum samples up to 315°C distillation temperature. It measures the amount of bromine that reacts with the olefinic double bonds in a hydrocarbon sample under specific acidic condition and is reported as mg of bromine per 100 grams of sample. Olefin saturation is an undesirable side reaction during the hydrogen desulfurization process. It increases the exothermic reaction, consumes more hydrogen and reduces octane rating. Thus reporting accurate bromine numbers are vital to unit design and operations.
Repeatability (r) and reproducibility (R) is unsatisfactory for the current ASTM D1159 forward titration. This has prompted investigation into the feasibility of a back titration method to ensure all olefinic compounds are reacted with bromine.
The current method measures the amount of bromine uptake to a diminishing rate at the end point. The measurement of this point is influenced by the geometry of the platinum electrode, by the applied voltametric current and by the steric hindrance of the olefin. Results can be variable.
Thus, the proposed rewrite of ASTM D1159 adds a known excess of bromine reagent to the titration vessel, allows the reaction to happen, and then back titrates the remaining bromine by a redox reaction to an inflection. The result is compared to a blank titration of bromate in the solvent to give the actual bromine number. Studies have been completed by Lummus Technology, Mettler Toledo, Metrohm and Tor Systems on a variety of hydrocarbon samples and the results are promising. A discussion will follow with plans for an ILS. Interested participants are encouraged to attend.
