Remarkable acceleration of the fructose dehydration over the adjacent Brønsted acid sites contained in an MFI-type zeolite channel

• Space proximities of acid sites are predominant in HZSM-5 with low Si/Al ratio.
• Reactant molecule suffers increased positive charge from multi Brønsted acid sites.
• Fructose dehydration is accelerated by cooperative catalysis of adjacent acid sites.
• The measured activation energies decrease with increased adjacent acid sites.

5-Hydroxymethylfurfural (HMF) is an important platform chemical that can be obtained from biomass by acid catalysis. In the current investigation, an acceleration of the dehydration of fructose to HMF with an increased reaction rate and decreased activation energy is identified over the adjacent acid sites in MFI-type zeolites. The spatial proximities of these sites become prominent with the decrease of the Si/Al ratio in HZSM-5 and increase the charge density on the adsorbed reactant molecule according to 13C MAS NMR results. The cooperative catalysis by the adjacent acid sites is deduced and it is very important to develop new effective acid catalysts.

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