Shortage leads to green route to olefins
A shortage of acrylic acid attributed to its increased use by coatings manufacturing in India and China—and for the superabsorbent polymers in disposable diapers—has led to a green route to glycerol and long-chain olefins via ultraviolet irradiation of fats and vegetable oils.
Acrylic acid—a petroleum-based product with few available biobased alternatives—is an extremely versatile chemical feedstock. Used either on its own or after esterification with various alcohols, acrylic acid is the base for acrylic polymers used in paints, coatings, detergents, sealants, adhesives, thickeners, emulsifying agents, dispersing agents, and the like. About four million metric tons of acrylic acid are produced annually, according to an industry source, with a value of $10 billion; demand is expected to increase.
“Our original interest was in the glycerol and its degradation products,” explains Douglas C. Neckers, the lead researcher and president/chief executive officer (CEO) of Biosolar LLC in Millbury, Ohio, USA. His study appeared in ACS Sustainable Chemistry & Engineering (doi:10.1021/sc400135y, 2013). “We’ve only just started down the pathway.”
Neckers and co-author Maria Muro-Small investigated a number of vegetable oils and animal fats, including olive oil, canola oil, waste cooking oil (canola oil put through at least three cycles of a small deep fryer), lard, and tallow. Irradiation with UV light (using either a Hanovia mercury lamp immersed in a quartz sleeve or a Fusion system equipped with an H-bulb) produced long-chain alkenes, dienes, trienes (such as 1-tetradecene; 1-hexadecene; 1,7-hexadecadiene; and 1,7,10-hexadecatriene) and glycerol. “The glycerol can be transformed through catalytic processes into acrylic acid and other essential raw materials for the plastic industry,” Neckers and Muro-Small write in their article.
Irradiation produced a number of photoproducts, and the results suggest that the saturated fatty acids (palmitic and stearic) are more photoreactive than the unsaturated fatty acids (oleic and linoleic); reactivity appears to depend on the position of the fatty acids on the glycerol backbone.
Neckers noted that there are two yields—the chemical yield and photochemical yield, or how much light is required. (See Table 1.) “We think the chemical yield will scale up nicely,” he added. “We are not sure about the photochemical yield.”
Next up on the docket: investigating the mechanism in order to increase the yield, producing the photoproducts from the glycerol instead of the glyceride, and processing them into a source of acrylic acid.
“I think the synthesis is well done,” commented W. Warren Schmidt, a consultant based in Cincinnati, Ohio, USA, and a member of the Inform Editorial Advisory Committee. “It may take years, but it may well become an alternate source of olefins.”
Neckers and Muro-Small are not alone in searching for a biobased route to acrylic acid. A number of companies, including Dow Chemical/OPXBIO and BASF/Cargill/Novozymes, have mounted similar efforts.
Dow Chemical and OPXBIO (see www.opxbio.com) signed a collaboration agreement in April 2011 to develop an industrial-scale process to produce BioAcrylic—acrylic acid from fermentable sugars such as corn and/or cane sugar. OPXBIO says that a life-cycle analysis conducted by Symbiotic Engineering, a greenhouse gas (GHG) and sustainability consultant, concluded that OPXBIO’s fermentation process using engineered microbes can reduce GHG emissions by more than 70% when compared to traditional petroleum-based acrylic acid production.
“The BioAcrylic process converts sugar feedstock . . . into the intermediate 3-hydroxypropionic acid (3-HP), which is then chemically dehydrated in a second step to BioAcrylic,” OPXBIO’s CEO Charles Eggert told Inform in an email. “We have successfully produced 3-HP in 3,000 liter (L) fermenters, and we anticipate pre-commercial production at the 25,000-L scale or larger beginning in 2014.
“Our plan is to start commercial-scale production and sales of BioAcrylic in 2017,” Eggert added, “with an initial plant capacity in the range of 100 million pounds [about 45,000 metric tons] per year.”
The BASF/Cargill/Novozymes partnership was formed in August 2012. The companies announced in July 2013 that they had produced 3-HP at pilot scale. Further, they reportedly have developed several technologies to dehydrate 3-HP at laboratory scale. The companies expect to reach the next level of scale-up in 2014, according to the Green Chemical Blog, although they declined to release any specific capacity goal.