Conventional car tires are made from fossil fuels. The process would be more environmentally friendly if they could be made from biomass instead. Technology patented by the University of Minnesota offers a new chemical process to make isoprene, which is the key molecule in car tires. The isoprene would be made from natural products like trees, grasses, or corn.

A method for producing tires from biomass has been patented by the University of Minnesota. In the current process, isoprene is produced by thermally breaking apart molecules and petroleum, a process called cracking. Although tire companies have been seeking a method to derive isoprene from biomass they have thus far been unsuccessful. Most of their efforts have been focused on fermentation technology, but renewable isoprene has been difficult to generate from microbes.

Researchers from the Center for Sustainable Polymers developed a three-step process that combines biological fermentation using microbes with conventional catalytic refining similar to petroleum refining technology.

The first step of the process is microbial fermentation of sugars derived from biomass to an intermediate called itaconic acid. The acid is then reacted with hydrogen to produce a chemical called methyl-THF (tetrahydrofuran), using a metal-metal combination as a catalyst.

The final step, which was the breakthrough, is to dehydrate methyl-THF to isoprene. This was done using a recently discovered catalyst called P-SPP (phosphorous self-pillared pentasil). The team achieved a catalytic efficiency as high as 90%, with most of the catalytic product being isoprene.

"This new class of solid acid catalysts exhibits dramatically improved catalytic efficiency and is the reason renewable isoprene is possible," says Paul Dauenhauer, of the University of Minnesota.

Economically bio-sourced isoprene has the potential to expand domestic production of car tires by using renewable, readily available resources instead of fossil fuels, says Frank Bates, University of Minnesota expert on polymers.