Toward an Economical Production of Propane and Propylene from Biomass

Biomass can be fermented to produce butyric acid or 3-hydroxybutyrate, which can then be decarboxylated to produce propane or propylene. Here's the abstract from research done at MIT chemical engineering dept. describing their more economical process of producing propane and propylene from butyric acid :

We demonstrate a route for the production of C3 hydrocarbons from renewable biomass by the hydrothermal conversion of well-known fermentation end-products. Specifically, the major commercial C3 hydrocarbons, propane and propylene, can be obtained from butyric acid and 3-hydroxybutyrate (3HB) in substantial yields and industrially relevant productivities by hydrothermal decarboxylation. Butyric acid decarboxylates in supercritical water to give propane as the major product at 454 °C and 25 MPa. 3HB undergoes joint dehydration and decarboxylation in subcritical water to yield propylene at 371 °C and 25 MPa with yields of up to 48 mol %. Although catalysts may be found that increase yields and selectivities, these processes were demonstrated without any added heterogeneous catalysts, and have the further advantage of requiring no external H2 source. _ACS

This follows an earlier report from U. Michigan and Zhejiang U. (China) describing the synthesis of longer chain hydrocarbons by decarboxylation from fatty acids, without added hydrogen.

Propylene has many industrial uses, and propane is the third most commonly used fuel in the world. If these 3 chain hydrocarbons can be made cheaply enough from biomass, they will find a ready market.

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