Efforts to displace petroleum feedstocks with biomass have largely focused on fuels, but there are also numerous opportunities to reduce petroleum use in commodity chemical production. One candidate is acrylonitrile (ACN), a precursor to diverse plastics and fibers that is currently derived from propylene. An international team of researchers report development of a new catalytic method to produce renewable ACN using 3-hydroxypropionic acid (3-HP), which can be sourced from sugars.

The hybrid biological-catalytic process offers an alternative to the conventional petrochemical production method and achieves unprecedented yields. The process achieves ACN molar yields of 98 percent from 3-HP via dehydration and nitrilation with ammonia over an inexpensive titanium dioxide solid acid catalyst. The traditional ACN production process achieves yields of approximately 80–83 percent.

The new scheme also eliminates production of hydrogen cyanide — a toxic side product — and can be performed in a simpler reactor configuration. The high-yield process can utilize non-food biomass, such as agricultural wastes, as a feedstock instead of propylene.

The researchers estimate the new process could bring the selling price of biomass-derived ACN below $1 per pound from cellulosic biomass or starch-based sugars. This economic target was deemed necessary for cost competitiveness with conventionally produced ACN.

Driven in part by the interest in using carbon fiber for lightweighting vehicles and aircraft that will save money on fuel costs, the demand for carbon fibers is projected to increase 11-18 percent annually. As the carbon fiber industry is especially sensitive to price fluctuations in their base chemical ACN (it takes roughly 2 pounds of acrylonitrile to generate 1 pound of carbon fiber), there is a clear need to develop alternative cost-competitive processes.

The technology was developed by researchers from the National Renewable Energy Laboratory, Golden, Colorado; the University of Colorado, Boulder, Colorado; Johnson Matthey Technology Centre, Billingham, U.K., and MATRIC, South Charleston, West Virginia.

Conceptual process diagram for renewable ACN production from biomass sugars. Source: Eric Karp (NREL) et al.