Energy
Interview with thought leader Peter Fristrup about Sustainable Chemistry

Peter Fristup (Technical University of Denmark, Department of Chemistry) has given an interview to Projects about his obsession with trying to turn biomass into useful scientific products. This study has taken place for decades, and the difficulties vary with converting raw plant materials into commodity chemicals still presenting many problems. However, if the Dane is successful biomass would become an invaluable raw material for future industry.

“At some point oil is either going to run out or become very expensive,” says Fristrup, “that’s why we have to make an effort to understand how to use other resources to generate the products we enjoy now, like fuels, plastics and pharmaceuticals.”

The issues with biomass are already apparent and take form in the the fact that it’s hard to generate industrial chemicals from the hydrogen-rich oil. Fristrup offers that “there are big problems with lignin” as an example, citing that “ot’s really difficult to break it down, and normally the solution is just to burn it off. Unfortunately it constitutes about 40% of the mass, so that’s a real issue.” After the processing has produced molecules like glucose, more trouble surfaces and Fristrup has been interested in understanding how best to convert these into valuable compounds. These are invaluable materials in the chemical industry, and are responsible for plastics and medicines. There are a wide variety of such compounds, and the synthetic routes to them from biomolecules are yet to be discovered.

In a recent breakthrough, Fristrup has identified the issue of turning glucose into a molecule known as 5-(hydroxymethyl)furfuryl (HMF) whilst working with DTU Chemistry colleague Anders Riisager. Take a look at the revealing spider diagram from their recent paper on the subject here:

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It shows six vital chemicals which the materials industry currently makes from HMF. These serve as solvents, fuels and building blocks for the industry. Whilst before it was an achievable feat (to make HMF from Glucose) only is it now far less expensive and bereft of toxic metal catalysts. However, when the team added boric acid, it increased the speed;“we wanted to investigate how that worked mechanistically, in detail” he said. Boric acid, both non-toxic and sustainble, is a naturally in abundance and thus is a perfect discovery.

“We did extensive modelling on these structures, to figure out where the boric acid would coordinate to the carbohydrate” says Fristrup. “In the next step you need to eliminate water to get to HMF,” Fristrup continues, “but we couldn’t see how the boric acid would help that part.”

In a test of whether it was involved in both steps of the reaction, an experiment was designed to compliment the theoretical studies. The reaction was run starting instead from fructose using different amounts of boric acid. “We get 70 or 80 per cent yield with 0.2 or 0.3 equivalents of boric acid, but once we go to one, two or three equivalents, we start to get less HMF produced”

What does this mean for the industry?

If Fristrup manages to develop a sustainable “reverse dihydroxylation” reaction and thus rid of  hydroxyl groups in the process, the procedure would then represent a tool to introduce biomass into the pre-existing infrastructure. This pertinent research isn’t only enlightening, but absolutely applicable, maybe soon chemical feedstocks will change irreversibly.

 

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