September 26, 2011
Can oxygenated organics be made from sugars? Sugars are at one extreme of feedstocks for producing industrially useful oxygen-containing chemicals such as alcohols, ketones, and carboxylic acids. Natural gas and petroleum fractions are at the other extreme. Sugars are overly oxygenated relative to the desired products, whereas hydrocarbons are underoxygenated. In the petrochemical industry, it is common for olefins and even alkanes to be subjected to oxidation reactions to produce useful industrial oxygen-containing chemicals such acrylic acid, adipic acid, and propylene oxide.
In the past several years, there has been a strong push to make so-called “renewable” chemicals from biofeedstocks. Converting feedstocks such as sugars, starches, and natural oils to chemicals will necessarily rely on reduction chemistry, mostly likely hydrogenolysis.
R. D. Cortright and P. G. Blommel disclose catalysts and operating conditions that allow sugars to be hydrogenated to mixtures of paraffins and mono-oxygenated materials in good yields. In one example, a tubular reactor is sequentially loaded with a hydrogenation catalyst (2.5% Ru/C) and an aqueous phase–reforming (APR)–deoxygenation catalyst (1.8% Pt/6.3% Rh/Zr). A solution of sucrose in water is passed over the catalyst beds at a weight hourly space velocity of 1.5–1.8. Hydrogen is then added to the reactor at rates of 3.4–4 mol H2/mol sucrose. The temperatures range from 110 to 150 °C over the hydrogenation catalyst bed and 150 to 265 °C over the APR catalyst bed.
The reaction products consist of 17.7–19.4% CO2, 10.8–14.1% paraffins, and 30.8–31.5% monooxygenates . The mono-oxygenate product distribution is ≈11% alcohols, ≈8% ketones, and ≈10% THF. This patent shows that sugars may well be a good source of oxygenated industrial chemicals. (Virent Energy Systems [Madison, WI]. US Patent 8,017,818, Sept. 13, 2011; Jeffrey S. Plotkin)
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