Oh O H2ccch3
FIGURE 8-12 Preparation of propylene glycol and acetol from glycerin. In the absence of H2/ acetol can be isolated as the major product by distillation as it is formed.
Propylene glycol has many desirable properties, including its low toxicity, which allow it to be used in a number of different products. Propylene glycol is the only glycol approved by the U.S. Food and Drug Administration for use in products meant for human consumption. It can be found in alcoholic beverages, confections and frostings, ice cieam, nuts and nut products, and seasoning and flavorings. This compound may also be present in cosmetics, pharmaceuticals, pet food, tobacco, paints, detergents, fragrances, resins, and antifreeze. Propylene glycol's many functions include preservative, moisturizer, wetting agent, coolant, and solvent. Currently, the bulk of automobile antifreeze is composed of ethylene glycol, which is acutely toxic. The economical production of large quantities of propylene glycol from the glycerin waste product of biodiesel production offers the potential to replace ethylene glycol in antifreeze with a significantly less toxic substance.
The Suppes group also discovered that glycerin could be reacted with copper chromite in the absence of hydrogen to produce acetol (Figure 8-12). They believe that this discovery could be even more important than the formation of propylene glycol, since acetol can act as precursor to many other organic compounds. Thus these other organic compounds could ultimately be formed from biomass rather than the petroleum-based precursors from which they are presently made. This would not only decrease the dependence on crude oil but would also lower the price of biodiesel by making the glycerin by-product more valuable.
Continue reading here: Hydrogen Fuel of the Future
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