Autocatalytic Hydration of Dihydropyran to 1,5-Pentanediol Precursors via in situ Formation of Liquid- and Solid-Phase Acids

作者：Barnett Kevin J; McClelland Daniel J; Huber George W^*

来源：ACS Sustainable Chemistry and Engineering, 2017, 5(11): 10223-10230.

DOI：10.1021/acssuschemeng.7b02208

• Dihydropyran
• Biomass
• Autocatalysis
• Hydration
• Catalysis
• Coke
• Acid

Dihydropyran (DHP) undergoes autocatalyzed hydration to 2-hydroxytetrahydropyran (2-HY-THP) by carboxylic acids formed in situ in both batch and continuous flow reactors. NMR, GC-MS, and pH analysis corroborate the presence of carboxylic acids in the hydration products. Carboxylic acids, likely in the form of 5-hydroxy-valeric acid, are made as low as 25 degrees C, increasing solution acidity and autocatalyzing DHP hydration. 1,5-Pentanediol precursors 2HY-THP and C10 dimers are produced from DHP at similar to 98% yields at temperatures <= 100 degrees C. At >= 140 degrees C, byproducts are formed, including acidic solid coke and a C10 dimer likely made via aldol condensation-cyclodehydration of the ring opened tautomer of 2-HY-THP, 5-hydroxyvaleraldehyde. DHP hydration rates continuously increased up to 50 h time-on-stream in continuous reactors demonstrating that the acidic byproducts catalyze this reaction. Activation rates rose with temperature due to increased acidic solid coke formation. The coke formed is soluble in water and its formation is reversible. Solid coke formed at high temperatures and retained in the reactor upon drying increased DHP 'hydration rates by up to 28x.

• 出版日期2017-11