Glycerol

Glycerol is a lipids.

Synthesis and production

  Until recently, synthetic glycerol was mainly manufactured at an industrial scale from Soap-making and biodiesel production are respective examples.

Glycerol is a 10% by-product of biodiesel production (via the transesterification of vegetable oils). This has led to a glut of crude glycerol on the market, making the epichlorohydrin process no longer economical. Current levels of glycerol production are running at about 350,000 tons per annun in the USA, and 600,000 tpa in Europe. This will increase as it implements EU directive 2003/30/EC which requires replacement of 5.75% of petroleum fuels with biofuel, across all Member States by 2010^[1].

Applications

In foods and beverages, glycerol serves as humectant, solvent and sweetener, and may help preserve foods. It is also used as filler in low-fat food products (i.e., cookies), and as a E number E422.

In prochiral building block.

Feedstock

It is one of the major raw materials for the manufacture of polyurethane foams.

Glycerol is used to produce nitroglycerin, which is an essential ingredient of smokeless gunpowder and various munitions. Reliance on soap-making to supply co-product glycerine made it difficult to increase production to meet wartime demand. Hence, synthetic glycerin processes were national defense priorities in the days leading up to World War II.

Glycerol is also used to manufacture mono- and di-glycerides for use as emulsifiers, as well as polyglycerol esters going into shortenings and margarine.

Pharmaceutical and personal care applications

Glycerol is used in medical and pharmaceutical and personal care preparations, mainly as a means of improving smoothness, providing lubrication and as a humectant. It is found in soaps.

As a 10% solution, glycerol prevents tannins from precipitating in ethanol extracts of plants (glycerites.^[2][3][4]

Used as a laxative when introduced into the rectum in enema) form; irritates the bowel and induces a hyperosmotic effect.

Glycerol is a component of glycerol sodium laureth sulfate. This kind of soap is used by people with sensitive, easily-irritated skin because it prevents skin dryness with its moisturizing properties. It is possible to make glycerol soap at home.

It is also used in de-/anti-icing fluids, as in liquid nitrogen

Potential uses

A great deal of research is being conducted to try to make value-added molecules from crude glycerol (typically containing 20 % water and residual esterification catalyst) obtained from biodiesel production, as an alternative to disposal by incineration. One such program to add value to this glut of glycerol is the UK-based initiative The Glycerol Challenge. Some potential uses for glycerol include the following:

• Hydrogen gas production unit
• Glycerine acetate (as a potential fuel additive)^[5]
• Compost additive
• Citric acid production
• Conversion to propylene glycol^[6].
• Conversion to acrolein^[7][8]
• Conversion to ethanol^[9]
• Conversion to epichlorhydrin^[10], a raw material for epoxy resins.

Metabolism

Glycerol is a precursor for synthesis of triacylglycerols and of glucose by the liver and provides energy for cellular metabolism.

Before glycerol can enter the pathway of glyceraldehyde 3-phosphate in the following steps:

The enzyme glycerol kinase is present only in the liver. In adipose tissue, glycerol 3-phosphate is obtained from dihydroxyacetone phosphate (DHAP) with the enzyme glycerol-3-phosphate dehydrogenase.

Danger of contamination with diethylene glycol

On May 4, 2007, the US Elixir Sulfanilamide" incident of poisoning caused by diethylene glycol contamination of medicine.

See also

• Oleochemicals
• Nitroglycerin

References

• U.S. Health.gov dietary guidelines

1. ^ The Glycerol Challenge
2. ^ Walter S. Long. The Composition of Commercial Fruit Extracts Transactions of the Kansas Academy of Science (1903-), Vol. 28, Jan. 14, 1916 - Jan. 13, 1917 (Jan. 14, 1916 - Jan. 13, 1917), pp. 157-161 doi:10.2307/3624347
3. ^ David Winston www.herbaltherapeutics.com
4. ^ http://www.newhope.com/nutritionsciencenews/NSN_backs/Apr_99/backtalk.cfm
5. ^ J. A. Melero, R. vanGrieken, G. Morales and M. Paniagua (2007). "Acidic Mesoporous Silica for the Acetylation of Glycerol: Synthesis of Bioadditives to Petrol Fuel". Energy Fuels 21 (3): 1782-1791. doi:10.1021/ef060647q.
6. ^ Dow Chemical Company (15 Mar 2007). "Dow Achieves Another Major Milestone in its Quest for Sustainable Chemistries". Press release.
7. ^ L. Ott, M. Bicker and H. Vogel (2006). "The catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production" 8 (2): 214-220. doi:10.1039/b506285c.
8. ^ Watanabe, M. et al (2007). "Acrolein synthesis from glycerol in hot-compressed water". Bioresource Technology 98: 1285-1290.
9. ^ S. S. Yazdani and R. Gonzalez (2007). "Anaerobic fermentation of glycerol: a path to economic viability for the biofuels industry". Current Opinion in Biotechnology 18 (3): 213-219. doi:10.1016/j.copbio.2007.05.002. Lay summary – ScienceDaily (27 Jun 2007).
10. ^ Dow Chemical Company (26 March 2007). "Dow Epoxy Advances Glycerine-To-Epichlorohydrin and Liquid Epoxy Resins Projects by Choosing Shanghai Site". Press release.
11. ^ U.S. Food and Drug Administration. "FDA Advises Manufacturers to Test Glycerin for Possible Contamination." Released May 4, 2007. Last retrieved May 8, 2007.
12. ^ WALT BOGDANICH and JAKE HOOKER. "From China to Panama, a Trail of Poisoned Medicine." New York Times. Published: May 6, 2007. Last retrieved May 8, 2007.