Renewable Biomass Could Make Less Expensive, More Sustainable Carbon Fiber Possible

December 7, 2017

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The U.S. Department of Energy’s (DOE’s) National Renewable Energy Laboratory’s (NREL’s) groundbreaking work on producing biobased renewable acrylonitrile was recently published in the peer-reviewed journal Science. Funded by DOE’s Bioenergy Technologies Office (BETO) through the Renewable Carbon Fibers funding opportunity, NREL’s process not only offers a cost-competitive, sustainable alternative to the conventional industrial petroleum-based production method, but also achieves unprecedented acrylonitrile yields.

You may not know it by name, but you likely use acrylonitrile every day. That’s because it’s a major commodity in the chemical industry with many diverse commercial applications. Today, acrylonitrile is used in the production of acrylic fibers for carpets, clothes, and fabrics, and in plastics such as food containers, packaging materials, and even children’s’ toys. It is also the primary building block in carbon fiber composites, which are used for lightweighting applications in automotive and air transportation—that is, replacing heavier materials like steel with lightweight carbon fibers to lower costs and improve fuel efficiency.

Nearly all commercial acrylonitrile is manufactured through a process called ammoxidation, during which propylene, ammonia, and air are fed through a catalyst at high temperatures. However, this process is energy-intensive and relies on expensive and complex catalysts. What’s more, it is often subject to price volatility in the propylene market.

An alternative manufacturing process, one that relies on renewably sourced biobased feedstocks, could help stabilize acrylonitrile prices and lead to broader market adoption of carbon fiber–based materials. This would be an important step forward for lightweighting transportation applications, which ultimately helps save money on fuel-related costs. 

Cue NREL’s new production method. Rather than using petroleum-derived propylene to produce acrylonitrile, NREL’s method uses biomass. Plant sugars are fermented into the intermediate 3-hydroxypropionic acid and then catalytically upgraded into acrylonitrile. Researchers were able to achieve a 98% yield of acrylonitrile compared to the decades-old ammoxidation method, which typically achieves approximately 80%–83%. Moreover, the process eliminates the production of a toxic byproduct (hydrogen cyanide), uses a simpler and less-expensive catalyst, and can be performed in a simpler reactor configuration. 

Based on NREL’s techno-economic analysis, biomass-derived acrylonitrile produced via this route was estimated at a modeled cost of less than $1 per pound—enabling this route to be cost-competitive with conventional acrylonitrile. NREL has filed an international patent application on this research, and the NREL Technology Transfer Office will be working with researchers to identify potential licensees of the technology.

NREL’s research paves the way for cost-competitive, sustainable acrylonitrile and carbon fibers from renewable biomass. This is especially significant considering the demand for carbon fibers is projected to increase 11%–18% annually. BETO supports early-stage applied research and development like NREL’s to enable cost-competitive biobased fuels and chemicals that can benefit Americans. A thriving, sustainable U.S. bioeconomy can help America fully utilize its abundant biomass resources, reduce reliance on foreign imports, and advance U.S. competitiveness in global energy and bioproduct markets. Read more in the NREL press release.