Cheaper, more sustainable way to produce plastic precursors

Kevin Barnett works in a lab at the department of energy bioenergy technologies office at UW-Madison to better the procedure for deriving 1,5-pentanediol, a possible substitute for a petroleum-like chemical.

Image By: Yingshan Deng

Scientists and engineers at UW-Madison developed an economically feasible process to synthesize a possible substitute for petroleum-derived chemicals from non-edible biomass.

This substitute, called 1,5-pentanediol, is a type of alpha, omega-diol that has two alcohol groups attached at the beginning and the end of a long carbon chain, which is mostly synthesized as a byproduct of other commercially produced diols.

The research was published this April in the journal, ChemSusChem.

“We hope to be able to make larger quantities and volumes and be able to put it in the applications that are currently used for other molecules,” said Zachary Brentzel, a graduate research assistant in college of engineering at UW-Madison and the first author of this paper. “If it’s not a direct substitute, we hope that we can actually find new applications where its properties are more beneficial.”

The old route to synthesize 1,5-pentanediol has only one step but requires expensive noble metals like Rhodium and Rhenium to work as catalysts, or compounds that accelerate chemical reactions but do not interact with the reaction itself, and break the ring of tetrahydro-furfuryl alcohol, or THFA.

However, the new route adds two more steps and uses Ruthenium, a metal that is 50 times cheaper than the catalysts used in the old route, said Kevin Barnett, a graduate student in the department of energy and bioenergy technologies office at UW-Madison and another leader on this project.

“The overall operating costs [of the new route], including catalysts and energy for separating compounds, are six times lower than the old route,” said Barnett.

He also pointed out that energy required in the new pathway is lower because the concentration of the final product is four to ten times higher than that of the old pathway, which makes it easier to separate 1,5-pentanediol from solvent.

In this new process, the five-membered ring—THFA—is catalyzed by a highly porous solid acid and become dihydropyran, or DHP, a six-membered ring. DHP becomes highly active with water and the ring opens without catalysts.

Brentzel said that one of the key steps was to find the equilibrium of the chemical in the ring form and chain structure, while another obstacle was to find the right catalyst.

“We are still testing for other non-noble metals as catalysts and our goal is to develop a catalyst for the process to use in industry,” said Barnett.

Besides economical benefits, Barnett said, 1,5-pentanediol could be a renewable alternative to current chemicals produced by petroleum.

Current industries use 1,4-butanediol and 1,6-hexanediol, two alpha, omega-diols synthesized from petroleum, to make polyesters and polyurethanes. Every year, 2,500,000 tons of 1,4-butanediol and 138,000 tons of 1,6-hexanediol are produced in the market, Brentzel said.

“The projected market price ranges for 1,4-butanediol and 1,6-hexanediol are $1,600−2,800 and $2,500−4,500 per ton, respectively, and the minimum selling prices of 1,5-pentanediol, assuming a pioneer plant economic model, for the old and new routes were $4,105 and $2,488 per ton, respectively,” the researchers explained.

And if biofuels could be co-produced with 1,5-pentanediols from biomass like wood, the costs of biofuel production would be reduced so it could be competitive with petroleum, Barnett said.

The team is currently in the process of patenting this technology and looking for companies to license it. The research is still ongoing in the labs of George Huber and James Dumesic at UW-Madison.

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