Sulfur, the tenth most abundant element in the universe, has been known since ancient times. Sometime around 1777, Antoine Lavoisier convinced the rest of the scientific community that sulfur was an element. Sulfur is a component of many common minerals, such as galena (PbS), gypsum (CaSO4·2(H2O), pyrite (FeS2), sphalerite (ZnS or FeS), cinnabar (HgS), stibnite (Sb2S3), epsomite (MgSO4·7(H2O)), celestite (SrSO4) and barite (BaSO4). Nearly 25% of the sulfur produced today is recovered from petroleum refining operations and as a byproduct of extracting other materials from sulfur containing ores. The majority of the sulfur produced today is obtained from underground deposits, usually found in conjunction with salt deposits, with a process known as the Frasch process.
Sulfur is a pale yellow, odorless and brittle material. It displays three allotropic forms: orthorhombic, monoclinic and amorphous. The orthorhombic form is the most stable form of sulfur. Monoclinic sulfur exists between the temperatures of 96°C and 119°C and reverts back to the orthorhombic form when cooled. Amorphous sulfur is formed when molten sulfur is quickly cooled. Amorphous sulfur is soft and elastic and eventually reverts back to the orthorhombic form.
Most of the sulfur that is produced is used in the manufacture of sulfuric acid (H2SO4). Large amounts of sulfuric acid, nearly 40 million tons, are used each year to make fertilizers, lead-acid batteries, and in many industrial processes. Smaller amounts of sulfur are used to vulcanize natural rubbers, as an insecticide (the Greek poet Homer mentioned “pest-averting sulphur” nearly 2,800 years ago!), in the manufacture of gunpowder and as a dying agent.
In addition to sulfuric acid, sulfur forms other interesting compounds. Hydrogen sulfide (H2S) is a gas that smells like rotten eggs. Sulfur dioxide (SO2), formed by burning sulfur in air, is used as a bleaching agent, solvent, disinfectant and as a refrigerant. When combined with water (H2O), sulfur dioxide forms sulfurous acid (H2SO3), a weak acid that is a major component of acid rain.
Petroleum products – Determination of sulfur content – Energy-dispersive-X-ray fluorescence method
This International Standard specifies a method for the determination of the sulfur content of hydrocarbons such as naphthas, distillates, fuel oils, residues, lubricating base oils only, unleaded gasolines and components. The method is applicable to products having sulfur contents in the range 0,03 % (m/m) to 5 % (m/m).
Why we need to know?
- Sulfur in crude oil is very important because it causes difficulties, such as corrosion of metals, in processing the oil and because air pollution results from the burning of high-sulfur fuels processed from crude oils having a high sulfur content.
- At a time when sulfur content restrictions on the use of fossil fuels are causing shortages and making it more difficult for industry to achieve air quality standards, data are needed regarding the quality of available world crude oil supplies.