A team of researchers has invented a new technology to produce automobile tires from trees and grasses. Conventional car tires are viewed as environmentally unfriendly because they are predominantly made from fossil fuels. The car tires produced from biomass that includes trees and grasses would be identical to existing car tires, with the same chemical makeup, color, shape, and performance.
The team created a new chemical process to make isoprene, the key molecule in car tires, from natural products like trees, grasses, or corn. Currently, isoprene is produced by thermally breaking apart molecules in petroleum that are similar to gasoline in a process called “cracking.” The isoprene is then separated out of hundreds of products and purified. In the final step, the isoprene is reacted with itself into long chains to make a solid polymer that is the major component in car tires.
Biomass-derived isoprene has been a major initiative of tire companies for the past decade, with most of the effort focused on fermentation technology (similar to ethanol production). However, renewable isoprene has proven a difficult molecule to generate from microbes, and efforts to make it by an entirely biological process have not been successful.
The new process begins with sugars derived from biomass including grasses, trees, and corn. A three-step process is optimized when it is “hybridized” — it combines biological fermentation using microbes with conventional catalytic refining that is similar to petroleum refining technology.
The first step of the new process is microbial fermentation of sugars, such as glucose, derived from biomass to an intermediate, called itaconic acid. In the second step, itaconic acid is reacted with hydrogen to a chemical called methyl-THF (tetrahydrofuran). This step was optimized when the team identified a unique metal-metal combination that served as a highly efficient catalyst.
The process technology breakthrough came in the third step to dehydrate methyl-THF to isoprene. Using a catalyst recently discovered at the University of Minnesota called P-SPP (Phosphorous Self-Pillared Pentasil), the team demonstrated a catalytic efficiency as high as 90 percent, with most of the catalytic product being iso-prene. By combining all three steps into a process, isoprene can be renewably sourced from biomass. The process could also impact other technologically advanced rubber-based products.