(421bm) Novel Catalyst Use In Glycerin Dehydration Chemistry

Traditionally in biodiesel production vegetable oils such as soy, canola, or corn oil are reacted with a mono-alcohol in order to cleave fatty acids from a glycerol backbone.  Glycerol is produced as a co-product from this reaction and has lead to a glut in the glycerol market.  In order to further increase the usefulness of this co-product, a catalytic gas dehydration of pure glycerol is performed in order to produce acrolein which is a more valuable precursor chemical in the production of acrylic acid and other specialty chemicals.  There are many catalysts that can be used in this dehydration process; typically phosphoric acid is used but this has led to problems with coking and fouling due to its overly acidic nature.  To alleviate this issue the catalyst sodium dihydrogen phosphate is used.

Glycerol that is produced as a co-product from biodiesel production is typically unsellable due to impurities in the product (soap, catalyst, and methanol).   A process used in order to purify the glycerol is to add small amounts of phosphoric acid in order to break the bond between the soap and the free fatty acid.  This in turn creates a mixture that can be separated by use of simple density separation.  The least dense material floats to the top and is primarily composed of free fatty acids, a mixture of methanol and glycerin sink to the bottom, and precipitate forms in between the layers.  This precipitate is sodium dihydrogen phosphate the very same chemical used as a catalyst in the dehydration process.

By using sodium dihydrogen phosphate as the catalyst for the glycerol dehydration the overall lifecycle of the biodiesel process can be improved; by using dihydrogen phosphate as the catalyst in the purification process, products and reactants are created during a single step of the process.  By using byproducts of the biodiesel process to create specialty chemicals further down stream  the economic and enviornmental viability of the process is increased.