Propylene Glycol, also known as 1.2 Propanediol is a chemical compound of CH3CHOHCH20H, a colorless, odorless, and tasteless liquid. It has a with specific gravity of 1.038-1.039 under a temp. of 20 C. It is hygroscopic soluble in water, alcohol and organic solvent with a boiling point of 187.3 C, with refraction index of 1.429 under a temp. of 27 C.
This chemical is used mainly as a basic material in UPR and as an auxiliary material in various inds, such as cigarette, perfume, essence, carbonated soft drink and pharmaceutical inds. It is also used as a solvent, antioxidant, etc.
There are two products of propylene glycol generally found in the market industrial grade and USP ( Pharmaceutical and food ) grade. The difference between the two grades lies in arsenic ( As2O3 0 and Pb contents and humidity.
The industrial grade has a zero arsenic and Pb content, and the USP grade has an arsenic content of 1 ppm and Pb content of 5 ppm maximum.
Process of Production
One method of producing propylene glycol is throught hydrolysis of propylene oxide. This method was first used by Wwurtz in 1859 before it was expanded commercially in 1931.
The process of producing propylene glycol is not very complex, only by putting in a reaction propylene oxide with water ( hydrolysis ) under a high pressure and temp. without catalysts. This method will turn out not only propylene glycol but also dipropylene glycol and higher adduct. The proportion of the products could be controlled based moll reactant ratio. Under comparable ration, the reaction will turn out propylene glycol making up 85%, dipropylene glycol making up 13% and higher adduct 1.5 %
There are a number of corporations having the technology to produce propylene glycol. Among them are Arco, Dow Chemical, Polybur and Chiyoda.
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