Abstract
We have investigated the synthesis and application of Au-Cu/CeO2 (Cu: Au = 2) in the continuous gas phase (P = 1 atm; T = 498 K) coupled hydrogenation of 5-hydroxymethyl-2-furaldehyde (HMF) with 2-butanol dehydrogenation. STEM-EDX analysis revealed a close surface proximity of both metals in Au-Cu/CeO2 post-TPR. XPS measurements suggest (support → metal) charge transfer to form Auδ− and strong metal-support interactions to generate Cu0 and Cu+. Au-Cu/CeO2 promoted the sole formation of 2,5-dihydroxymethylfuran (DHMF) and 2-butanone in the HMF/2-butanol coupling with full hydrogen utilisation. Under the same reaction conditions, Au/CeO2 was fully selective to DHMF in standard HMF hydrogenation (using an external hydrogen supply), but delivered a lower production rate and utilised less than 0.2% of the hydrogen supplied. Exclusive -C=O hydrogenation and -OH dehydrogenation is also demonstrated for the coupling of a series of m-substituted (-CH3, -CH2CH3, -CH2OH, -CF3, -N(CH3)2, -H) furaldehydes with alcohol (1-propanol, 1-butanol, 2-propanol, 2-butanol, cyclohexanol) dehydrogenation over Au-Cu/CeO2, consistent with a nucleophilic mechanism. In each case, we observed a greater hydrogenation rate and hydrogen utilisation efficiency with a 3–15 times lower E-factor in the coupling process relative to standard hydrogenation. Our results demonstrate the feasibility of using hydrogen generated in situ through alcohol dehydrogenation for the selective hydrogenation of m-furaldehydes with important industrial applications.
Highlights
Our results demonstrate the feasibility of using hydrogen generated in situ through alcohol dehydrogenation for the selective hydrogenation of m-furaldehydes with important industrial applications
5-hydroxymethyl-2-furaldehyde (HMF) has emerged as a promising biomass-derived platform chemical [1] that can be readily obtained from C6 carbohydrates by dehydration in the presence of acid catalysts [2,3]. 2,5-Dihydroxymethylfuran (DHMF), a reduction product of HMF, is used as a precursor in the manufacture of polymer plastics resins and artificial fibres [5,6]
In the gas-phase coupled 2-butanol dehydrogenation with HMF hydrogenation, Au-Cu/CeO2 was 100% selective towards the production of targets 2-butanone and DHMF (Figure 1(II)). These two products can be readily separated by distillation due to the (195 K) difference in boiling points [28]
Summary
Au-Cu/CeO2 promoted the sole formation of 2,5-dihydroxymethylfuran (DHMF) and 2-butanone in the HMF/2-butanol coupling with full hydrogen utilisation. Under the same reaction conditions, Au/CeO2 was fully selective to DHMF in standard HMF hydrogenation (using an external hydrogen supply), but delivered a lower production rate and utilised less than. Exclusive -C=O hydrogenation and -OH dehydrogenation is demonstrated for the coupling of a series of m-substituted -N(CH3 )2 , -H) furaldehydes with alcohol (1-propanol, 1-butanol, 2-propanol, 2-butanol, cyclohexanol) dehydrogenation over Au-Cu/CeO2 , consistent with a nucleophilic mechanism. Our results demonstrate the feasibility of using hydrogen generated in situ through alcohol dehydrogenation for the selective hydrogenation of m-furaldehydes with important industrial applications.
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