Nearly all of the currently produced building-block chemical acrylonitrile (AN) results from the ammoxidation of propylene, a process that requires precise heat control and generates several toxic side products, such as hydrogen cyanide. The startup company Mars Materials (Houston, Tex.; marsmaterials.tech) has developed an alternative process that utilizes captured CO2 or bio-based feedstocks, improves the yields of AN and eliminates production of key toxic byproducts.
“In the incumbent process, side reactions generate toxic impurities that end up creating problems in the final AN products,” explains Mars Materials CEO Aaron Fitzgerald. “Our carbon-negative AN process improves yields and safety while producing an impurity-advantaged AN product.”
AN is used in a wide range of products, including polymers like acrylonitrile-butadiene-styrene (ABS) and nitrile rubber (NBR). Also, when AN is polymerized, it can be used as a matrix for carbon-fiber composites. But Mars will initially focus on bio-converting its AN into acrylamide and water-soluble polymers, which can be used in drinking water purification and paper products. This is a unique advantage for Mars’ pathway. The company recently announced it overcame a decades-long incumbent barrier to demonstrate that its AN can serve as a drop-in feedstock for global acrylamide industry leader, SNF (Andrézieux, France; www.snf.com).
Mars Materials’ AN technology was licensed from the National Renewable Energy Laboratory (NREL; Golden, Colo.; www.nrel.gov) for commercialization, and has been adapted to utilize CO2 by Mars Materials.
Mars’ process converts three- to five-carbon ester and acid intermediates — derived from CO2 or biomass — into AN with high selectivity. “The underpinning technology, known as nitrilation, leverages decades-old thermocatalysis and off-the-shelf equipment, along with Mars’ proprietary process parameters, to produce impurity-advantaged AN,” Fitzgerald explains. The AN then enters a series of distillation columns, where ammonia and solvent are recovered and recycled, to produce high-purity AN (see diagram). The main byproduct is water. By leveraging an endothermic reaction pathway, the process enhances safety while reducing capital intensity.
Fitzgerald says the Mars renewable AN process is currently producing kilogram-scale amounts at a pilot plant located at the Shell Technology Center, a research and development facility in Houston.