Abstract
The sustainable green chemistry associated with lignocellulosic biomass is of current interest for producing various chemical feedstocks via multi-step transformation processes. Here we introduce a chemical platform system for the multicomponent cascade transformation of natural lignocellulosic biomass resources. We demonstrate the concept by developing an integrated continuous two-step microfluidic system as a tandem transformation platform for direct conversion of fructose to diverse furan chemicals with excellent yields up to 99% via decarbonylation, etherification, oxidation and hydrogenolysis of a 5-hydroxymethylfurfural (HMF) intermediate. A sequential two-step process is utilized to complete the dehydration of fructose in the surface acid catalyst at 150 °C for 6 min, which is followed by the four types of HMF conversion in a binary or ternary phase to produce furfuryl alcohol (94% yield), 5-ethoxymethylfurfural (99%), 2,5-diformylfuran (82%) and 2,5-dimethylfuran (90%) with magnetic-based heterogeneous catalysts at 70–150 °C for 6–60 min. This innovative tandem microfluidic platform enables precise control of the reaction temperature and time for each individual biomass conversion step in a one-flow manner with no separation and purification steps for intermediates and catalysts.
Highlights
We demonstrate the concept by developing an integrated continuous two-step microfluidic system as a tandem transformation platform for direct conversion of fructose to diverse furan chemicals with excellent yields up to 99% via decarbonylation, etherification, oxidation and hydrogenolysis of a 5-hydroxymethylfurfural (HMF) intermediate
Fructose and glucose are suitable for the use as an economical chemical feedstock for producing heterocyclic furan chemicals such as 5-hydroxymethylfurfural (5-HMF),4 furfuryl alcohol (FFA),5 2,5-diformylfuran (2,5-DFF)6 and 2,5-dimethylfuran (2,5-DMF)
5-HMF, a dehydration product of fructose, is an important renewable chemical intermediate that can be used as a starting material for producing diverse furan building blocks, which can be used as fuel or replacements of oil-derived chemicals
Summary
The efficient transformation of abundant biomass resources such as carbohydrates, lignin, fatty acids, lipids and cellulose into organic chemicals has received much attention as a path to green chemistry that is environmentally friendly. Among six-carboned carbohydrates, hexoses are the most abundant monosaccharides existing in nature. Of these, fructose and glucose are suitable for the use as an economical chemical feedstock for producing heterocyclic furan chemicals such as 5-hydroxymethylfurfural (5-HMF), furfuryl alcohol (FFA),5 2,5-diformylfuran (2,5-DFF) and 2,5-dimethylfuran (2,5-DMF). It is known that the catalytic transformation of hexoses into these furanic products involves several chemical steps such as dehydration, hydrolysis, isomerization, condensation, hydrogenation and oxidation. In general, 5-HMF, a dehydration product of fructose, is an important renewable chemical intermediate that can be used as a starting material for producing diverse furan building blocks, which can be used as fuel or replacements of oil-derived chemicals. The synthesis of furan derivatives from carbohydrates typically involves multiple reaction steps, such as dehydration for HMF production, followed by further transformation in the presence of heterogeneous catalysts. The synthesis of furan derivatives from HMF in a single step is well documented. The synthesis of furan derivatives from carbohydrates typically involves multiple reaction steps, such as dehydration for HMF production, followed by further transformation in the presence of heterogeneous catalysts.. The direct synthesis of the derivatives from carbohydrates is rarely reported and remains challenging because it requires a two-step process involving the isolation and purification of HMF as an intermediate and separation of the catalyst from the main stream, which is a time-, cost- and labor-consuming process.. We reported the concept and method for continuous and integrated in situ generation on the demand, separation and reaction of malodor, toxic and/or explosive reagents utilizing microfluidic systems.12–14 These approaches illustrated the advantages of forming and immediately utilizing the intermediates for subsequent reactions in a continuous-flow system. The successful outcome suggests that an integrated continuous-flow system is suitable for direct conversion of carbohydrate resources into organic chemicals in Received 11 January 2015; revised 5 February 2015; accepted 9 February 2015
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