(474c) Conversion of Carbohydrates to Chemicals in Hot Water Using SO2 As a Recoverable Catalyst

Carbohydrates, such as cellulose, hemicellulose, cellobiose, starch and sucrose are the most widely distributed sources of natural biomass, which hold impressive potential as alternatives to fossil fuels for sustainable production of fuels and chemicals. Current industrial processes to convert carbohydrates are typically catalyzed by either enzyme or mineral acid catalyst. The enzyme hydrolysis has no pollution and by-products, but is of low efficiency and high costs, while the latter process is efficient and technical maturely except that the acid recovery is difficult, the environmental pollution and the equipment corrosion is serious. Efficient conversion of carbohydrates to a variety of chemicals is important for a sustainable future.

In this work, sulphur dioxide (SO₂) dissolved in hot water is shown to be an efficient catalyst for the selective conversion of carbohydrates (cellulose, xylan, starch, inulin and sucrose) to chemicals such as glucose and levulinic acid. The selectivity of products can be tuned by SO₂ composition, temperature and reaction time. SO₂ acts both as a supply of H⁺ ions through the ionization of H₂SO₃ when dissolved in water and as a catalyst that breaks the hydrogen bonds in cellulose. Importantly, the SO₂ can be recovered thoroughly by stream stripping, thus avoiding the formation of acidic waste water.