Environment Technology

A Newly Developed Technology Can Produce Renewable Car Tires From Trees and Grasses

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A University of Minnesota led team of researchers has pioneered a new technology to produce car tires from trees and grasses. The new process could move the tire production industry toward using renewable resources found right on our doorstep.

Conventional car tires are classified as environmentally unfriendly because they are manufactured mainly from fossil fuels. The car tires produced from biomass including trees and grasses would be undistinguishable from existing car tires and will have the same color, shape, chemical makeup and performance.

Paul Dauenhauer, a University of Minnesota associate professor of chemical engineering and materials science, is the lead researcher of the study. He explained that the team invented a new chemical process to produce isoprene, the key molecule in car tires, from natural products like corn, trees, or grasses. This research will likely have a major impact on the manufacture of automobile tires, a multi-billion dollar industry.

Carol Bessel is the deputy director for the chemistry division at the National Science Foundation (NSF), which funds the Center for Sustainable Polymers. He noted that the key to this research taking biomass to isoprene was collaboration. The collaboration and synergy among researchers from different disciplines, each having their own unique approaches and skills, is really what the NSF Centers for Chemical Innovation Program is trying to promote.

Catalytic conversion of biomass-derived chemicals to renewable polymers occurs in lab stirred-tank reactors. (Image Credit: University of Minnesota)
Catalytic conversion of biomass-derived chemicals to renewable polymers occurs in lab stirred-tank reactors. (Image Credit: University of Minnesota)

Isoprene is currently produced by thermally splitting molecules in petroleum that are similar to gasoline. This process is known as “cracking”. In the next step of the production process, the isoprene is separated out of hundreds of products and purified. The isoprene is finally reacted with itself to form long chains that makes a solid polymer. This polymer is the major component in automotive tires.

For the past decade, isoprene derived from biomass has been a major initiative of tire companies, with the majority of the effort focused on fermentation technology. This is the same technology used in the production of ethanol. Renewable isoprene has however proven a difficult molecule to generate from microbes, and attempts to make it with a process that is completely biological have not been successful.

Researchers from the Center for Sustainable Polymers, funded by NSF, have concentrated on a new process that starts with sugars derived from biomass, including corn, grasses and trees. It was found that the three-step process is optimized when it is “hybridized”. The process combines biological fermentation using microbes with conventional catalytic refining, similar to petroleum refining technology.

The first step of the new process is microbial fermentation of sugars derived from biomass to create an intermediate called itaconic acid. Itaconic acid is reacted with hydrogen in the second step. This forms a chemical called methyl-THF (tetrahydrofuran). The research team managed to optimize this step when they identified a unique metal-metal combination that functioned as a highly efficient catalyst.

The third step involves converting dehydrate methyl-THF to isoprene and this is where the process technology breakthrough was made. The team used a catalyst called P-SPP (Phosphoros Self-Pillared Pentasil), recently discovered at the University of Minnesota, and was able to demonstrate a catalytic efficiency as high as 90 percent with most of the catalytic product being isoprene. Isoprene can be renewably sourced from biomass when all three steps are combined into a process.

Dauenhauer was surprised by the performance of the new P-containing zeolite catalysts such as S-PPP. He noted that renewable isoprene is only possible because this new class of solid acid catalysts exhibits radically improved catalytic efficiency.

Frank Bates, a polymer expert and University of Minnesota Regents Professor of Chemical Engineering and Materials Science explained that bio-sourced isoprene that can be manufactured economically has the potential to increase domestic production of car tires by using renewable resources that are readily available, instead of fossil fuels.

This discovery could also have an impact on many other technologically advanced rubber-based products.

The full peer reviewed study was published in the journal ACS Catalysis.

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