Microemulsion and Sol-Gel Synthesized ZrO2-MgO Catalysts for the Liquid-Phase Dehydration of Xylose to Furfural

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Author
Montes, Vicente
Hidalgo-Carrillo, J.
Marinas, Alberto
Urbano, Francisco José
Parejas, A.
Sánchez-López, Elena
Publisher
MDPIDate
2017Subject
Xylose dehydrationFurfural
MgO-ZrO2 mixed catalysts
Microemulsion synthesis
Sol-gel synthesis
Solvent effect
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Two series of catalysts were prepared by sol-gel and microemulsion synthetic procedure
(SG and ME, respectively). Each series includes both pure Mg and Zr solids as well as Mg-Zr mixed
solids with 25%, 50% and 75% nominal Zr content. The whole set of catalysts was characterized from
thermal, structural and surface chemical points of view and subsequently applied to the liquid-phase
xylose dehydration to furfural. Reactions were carried out in either a high-pressure autoclave or in
an atmospheric pressure multi-reactor under a biphasic (organic/water) reaction mixture. Butan-2-ol
and toluene were essayed as organic solvents. Catalysts prepared by microemulsion retained part
of the surfactant used in the synthetic procedure, mainly associated with the Zr part of the solid.
The MgZr-SG solid presented the highest surface acidity while the Mg3Zr-SG one exhibited the
highest surface basicity among mixed systems. Xylose dehydration in the high-pressure system
and with toluene/water solvent mixture led to the highest furfural yield. Moreover, the yield of
furfural increases with the Zr content of the catalyst. Therefore, the catalysts constituted of pure ZrO2
(especially Zr-SG) are the most suitable to carry out the process under study although MgZr mixed
solids could be also suitable for overall processes with additional reaction steps