Potentiometric determination of trace amounts of elemental sulphur in crude oil and petroleum fractions

Abstract

A potentiometric method is described for the determination of elemental sulphur in petroleum and petroleum fractions over all concentration ranges. The method involves the conversion of elemental sulphur into a homogeneous thiosulphate solution, followed by potentiometric titration using mercury(l1) chloride as titrant with a sulphide-selective indicator electrode.The accuracy and reproducibility of the method were established by titrating several synthetic standards dissolved in heptane in which the free sulphur, at levels ranging between 1.0 x 10-3 and 1.0 x 10-1 g, was converted quantitatively into homogeneous thiosulphate solutions containing from 4.0 x 10-6 to 4.0 x 10-4 g ml-l of elemental sulphur. The results obtained, expressed in the form of a Gran plot, showed an error ranging from 0.88 to 2.33% by mass. The range of concentrations of elemental sulphur in crude oil and eleven petroleum fractions ranged from 1.83 x lO-3% by mass in heavy naphtha to 4.62 x lO-5% by mass in hydrotreater kerosene, with a relative standard deviation ranging from 1.20 to 5.61%.

Electrochemical determination of elemental sulfur in Brazilian naphtha: method and validation

“…Therefore, methods for determining trace amounts of elemental sulfur have been a great challenge in the area of chemical analysis. The large number of analytical methods that have been proposed for determination of elemental sulfur indicates that there is no established quantitative method for the direct determination of trace quantities of elemental sulfur in petroleum matrices [11][12][13][14][15][16]. In fact, the most common methods found in the literature were developed to quantify total sulfur [5] and sulfide [1,8] compounds.…”