Polish version

Separation and purification of salicylic acid

Salicylic acid is an ortho-hydroxybenzoic acid. It is produced in big quantities and constitutes an important precursor to produce numerous pharmaceutical preparations.

A brief description of the technology

Salicylic acid is produced mainly from phenol. The post-reaction mixture contains: sodium salicylate, excess sodium hydroxide or sodium carbonate, small amounts of phenol and a number of unidentified by-products of tarry character. Salicylic acid is isolated from this solution by thinning with water and separation with hydrochloric or sulfuric acid. This way obtained raw acid has brown color and is much polluted. The developed technology to purify raw salicylic acid comprises selective absorption and desorption.

Advantages of the technology offered

The method of selective absorption and desorption employed to remove pollution and by-products from the salicylic acid is less power-consuming and cheaper than the traditionally used sublimation method.


  • three column sets (three columns each) filled with the same absorbent (in the production process two columns in each set operate connected in series and the third one is then regenerated),
  • agitators,
  • filtration press.


Patent No P-192 178 „Method to purify raw salicylic acid”.

Market competitiveness

The method is much cheaper and more efficient than the sublimation method.


The technology was developed on the half-technical scale and has not been implemented so far. Half-technical trials have been performed on the installation mounted in a production hall at the PSA branch of the „Polpharma” Pharmaceutical Plant in Starogard Gdański.


Irena Grzywa-Niksińska, Ph.D., Chem. Eng.

phone: + 48 22 568 20 05