August 12, 2013
Make acrylic acid from the glycerol in biodiesel. Using renewable feedstocks for making “petrochemical”-based chemicals is attractive from the environmental and marketing points of view. In concept, chemicals made from renewables are environmentally friendly; and from a marketing perspective they allow end users to put a “green” label on their products.
Biodiesel byproduct glycerol is an attractive feedstock for making renewable chemicals. Because glycerol is a very high-boiling, viscous liquid, however, purifying glycerol from the biodiesel reaction stew by distillation is very energy-intensive.
Inventors T. Aoki and N. Arai disclose a process in which vegetable oil–based glycerol can be converted to acrylic acid with much less energy consumption. They found that a crude glycerol mixture can be used without purification to make acrylic acid.
In an example, the mixture shown in the table is fed at a rate of 8 g/h to a first-stage reactor filled with 5 mL KHSO4/SiO2 catalyst and heated to 300 °C. The effluent is directed to a second-stage reactor that contains 5 mL MoVWCuOx/α-Al2O3 catalyst maintained at 280 °C. Oxygen is supplied to the second reactor at the rate of 600 mL/h (normalized).
The exit port of the second-stage reactor is cooled, and the reaction gas is condensed and analyzed. GC showed that glycerol conversion is 100%, and the acrylic acid yield is 51%. (Showa Denko KK [Tokyo]. US Patent 8,461,380, June 11, 2013; Jeffrey S. Plotkin)
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