Sulfuric acid: properties, production and applications

Sulfuric acid (H₂SO₄) is a strong dibasic inorganic acid and one of the most important and largest-volume products of the modern chemical industry. Anhydrous sulfuric acid is a colourless, highly viscous and hygroscopic liquid with no odour. Its melting point is 10.4 °C, and its density is 1831–1834 kg/m³ at 20 °C. When heated, the acid partially decomposes with the release of sulfur trioxide SO₃, and distils as an azeotropic mixture with a mass fraction of H₂SO₄ of 98.3% and a boiling point of 338.8 °C. At higher temperatures, complete decomposition occurs. Sulfuric acid is infinitely miscible with water and SO₃; in aqueous solutions, it almost completely dissociates to form H₃O⁺, HSO₄⁻ and SO₄²⁻ ions, and forms two series of salts — sulfates and hydrosulfates. The technical mixture of concentrated H₂SO₄, SO₃ and disulfuric acid H₂S₂O₇ is called oleum. Sulfuric acid displaces other acids from their salts and is neutralised by alkalis. Concentrated H₂SO₄ is a strong oxidising agent: when heated, it oxidises almost all metals (except gold and platinum metals), non-metals, HBr, HI and other compounds. In the cold, some metals, such as cobalt and iron, are passivated in concentrated sulfuric acid. Dilute H₂SO₄ reacts with metals located to the left of hydrogen in the electrochemical series, releasing H₂. Peroxo derivatives are also known: H₂SO₅ (peroxomonosulfuric acid, or Caro's acid) and H₂S₂O₈ (peroxodisulfuric acid).

Historical Background and Production Technologies

The production of "oil of vitriol" (concentrated sulfuric acid) by calcining iron or copper sulfate is described in the works of alchemists. The oldest industrial method for producing sulfuric acid was proposed in 1690 and involved burning a mixture of sulfur and saltpetre and absorbing the product in water in a glass bottle. In 1746, English technologist J. Roebuck proposed replacing glass bottles with chambers made of sheet lead — this gave rise to the chamber process. The nitrous process was developed in 1860 by English chemist J. Glover. The principle of the contact process for sulfuric acid production was discovered in 1831 by English chemist P. Phillips and became widespread in the early 20th century.

Currently, the main industrial method for producing sulfuric acid is the contact process. The process includes three stages: production of sulfur dioxide SO₂ by burning elemental sulfur or roasting iron pyrite; catalytic oxidation of SO₂ to sulfur trioxide SO₃ on a vanadium catalyst; and absorption of SO₃ by water to form sulfuric acid. The raw materials used are elemental sulfur, pyrite (FeS₂), hydrogen sulfide, and off-gases from metallurgical production.

Applications

Sulfuric acid is one of the most widely used industrial chemicals and is sometimes called the "blood of the chemical industry" because of its use in key syntheses. According to Statista, the global market volume of sulfuric acid in 2020 amounted to 256 million tonnes, and it is forecast to increase to approximately 295 million tonnes by 2026. The main consumption areas are distributed as follows: about 32% — production of phosphoric acid and fertilizers; about 58% — basic chemical synthesis, pigment production and petroleum refining; about 2% — metal extraction and processing; about 0.8% — battery production; about 7% — other industrial applications, including pulp and paper. Agricultural use of sulfuric acid accounts for a minor share (about 0.025%) and is primarily for use as a desiccant for potato crops.

Sulfuric acid is used in the production of mineral fertilizers (phosphoric acid, superphosphate, ammonium sulfate), as an electrolyte in lead-acid batteries, in hydrometallurgy for opening complex ores, for producing phosphoric acid, various mineral acids and salts, chemical fibres, dyes, explosives, plastics, synthetic detergents, pharmaceuticals, for refining petroleum products, and in the production of titanium dioxide and caprolactam. According to GOST 2184-2013, technical sulfuric acid is intended for the production of fertilizers, artificial fibres, caprolactam, titanium dioxide, ethyl alcohol, aniline dyes and a number of other industries.

Global Production and Market

The global sulfuric acid market demonstrates steady growth. According to Fortune Business Insights, the market was valued at USD 35.13 billion in 2025, projected to reach USD 36.61 billion in 2026 and USD 52.86 billion by 2034 at a CAGR of 4.7% during the 2026-2034 forecast period. The Asia-Pacific region dominated the global market with a share of 50.58% in 2025. Key companies operating in the market include BASF SE, Nouryon, The Mosaic Company, PVS Chemicals and OCP Group.

According to other estimates, the sulfuric acid market was valued at USD 17.23 billion in 2025 and is expected to grow to USD 18.86 billion in 2026 at a CAGR of 9.4%, reaching USD 26.36 billion by 2030. The main market growth drivers are increasing fertilizer consumption, expanding mining activity, growth in petroleum refining, development of the chemical industry, and growing demand for lead-acid batteries for electric vehicles. The Asia-Pacific region continues to expand capacity, while Europe focuses on recycling and acid regeneration.

Production in Russia

In Russia, about 85% of the total volume of sulfuric acid is produced by five largest plants. Over 60% of sulfur-containing raw materials are obtained from gas processing, and more than 80% of this raw material is used in the production of oleum and sulfuric acid. More than 60% of the sulfuric acid produced is used in the manufacture of phosphate fertilizers. In the period up to 2035, over RUB 4 trillion will be invested in projects related to the production of sulfur and sulfuric acid, with 61% of these investments falling on the oil refining sector.

In 2025, at the facilities of the PhosAgro group, the SK-714 sulfuric acid unit in Cherepovets was modernised, which will allow an additional 16,000 tonnes of acid per year to be produced. Also, in Balakovo, the second technological line of the SK-20/1 sulfuric acid unit was commissioned, increasing sulfuric acid output by 750,000 tonnes per year with full self-sufficiency of the production complex.

Safety and Regulatory Framework

Sulfuric acid is a corrosive and hazardous substance. Inhalation of sulfuric acid mist causes a reflex increase in respiratory rate and bronchoconstriction, and acute exposure can lead to severe bronchospasm and non-cardiogenic pulmonary oedema. Strict safety measures must be observed when working with sulfuric acid, including the use of personal protective equipment and effective ventilation.

Requirements for technical sulfuric acid in Russia and CIS countries are regulated by GOST 2184-2013 "Sulfuric acid for industrial use. Specifications", which applies to contact acid (improved and technical), oleum (improved and technical) and regenerated acid. For high-purity sulfuric acid, GOST 14262-78 applies, and for reagent-grade acid — GOST 4204-77.

Conclusion

Sulfuric acid remains one of the key products of the global chemical industry, providing for the production of fertilizers, chemical fibres, dyes, explosives, batteries and many other products. Growing demand for phosphate fertilizers, the development of electric vehicles and the expansion of the mining industry are creating sustained demand for this essential chemical. Russia, possessing significant production capacities and implementing large investment projects, maintains its position as one of the leading players in the global sulfuric acid market.