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Single-step process to convert cellulose biomass into PET intermediate chemical |
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Scientists at Pacific Northwest National Laboratory (Washington) have discovered a highky effective method to convert cellulose biomass that is abundantly found in plants to 5-hydroxymethylfurfural (HMF), a chemical that can be used as a raw material for plastics and fuels currently made from crude oil. This breakthrough one-step process for converting cellulose to HMF promises to turn plants into eco-friendly and renewable replacement for crude oil. Previously, researchers at the Department of Energy at PNNL produced HMF from simple sugars derived from cellulose. The new single-step process builds upon the earlier two-step process of conversion.
In this new work, researchers developed a way to bypass the sugar-forming step and go straight from cellulose to HMF. This simple process generates a high yield of HMF and allows the use of raw cellulose feed material. The feed chemical HMF thus formed can be used for producing polyesters, biofuels like green diesel. In previous work, PNNL researchers used a chemical and a solvent known as an ionic liquid to convert the simple sugars like glucose and fructose into HMF. The chemical, a metal chloride known as chromium chloride, converted sugar into highly pure HMF. This first required breaking down of cellulose into glucose and fructose and finally, conversion of these simple sugars into HMF. NPPL research team wanted to bypass the sugar-forming step thereby reducing the whole Cellulose-to-HMF conversion process to a single step. After trying different metal chloride catalysts in the ionic solvent, they found a pair of catalysts that worked well: A combination of copper chloride and chromium chloride under 120� C broke down the cellulose without creating a lot of unwanted byproducts.
Other methods used for converting simple sugars to HMF involved use an acidic catalyst, in an aqueous solution, which resulted in high levels of unneeded byproducts. The research team evaluated how well their method worked compared to acid, a common way to break down cellulose. The metal chlorides-ionic liquid system worked ten times faster than the acid and at much lower temperatures.
Optimizing their method, the team found that they could consistently achieve a high yield of HMF. This newly developed process converted about 57% of the sugar content in the cellulose feedstock to HMF in a single step process. In addition, the team recovered more than 90% of the HMF formed, and the final product from the process was 96% pure. Besides being a one-step method, the metal chlorides and ionic liquid employed in the process could be reused multiple times without losing their effectiveness. Being able to recycle the materials will lower the cost of HMF production.
This path-breaking development can help to lessen reliance on crude oil for plastic intermediates. Oxidation of HMF gives 2,5-furandicarboxylic acid, which has been proposed as a replacement terephthalic acid for the production of polyesters like polyethylene terephthalate (PET). The high expenses for manufacturing HMF hindered its commercial use in production of polyesters. On the other hand, experts believe that conversion of this feed material into plastics is practically simple. Substituting crude-derived products with biomass alternatives derived from waste plants will go a long way to reduce global warming potential. |
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