Department of Organic Chemistry, Institute for Research in Fine Chemistry and Nanochemistry, IUIQFN, Universidad de Córdoba, Campus de Rabanales, Marie Curie Building, E-14014 Córdoba, Spain.
Molecules. 2017 Dec 18;22(12):2257. doi: 10.3390/molecules22122257.
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.
两组催化剂分别通过溶胶-凝胶法和微乳液合成法（SG 和 ME）制备。每个系列均包含纯 Mg 和 Zr 固体，以及具有 25%、50%和 75%名义 Zr 含量的 Mg-Zr 混合固体。整套催化剂从热、结构和表面化学角度进行了表征，随后应用于液相木糖脱水制糠醛。反应在高压釜或常压多反应器中进行，在两相（有机/水）反应混合物中进行。丁醇和甲苯被用作有机溶剂。通过微乳液制备的催化剂保留了合成过程中使用的部分表面活性剂，主要与固体的 Zr 部分有关。MgZr-SG 固体具有最高的表面酸度，而 Mg3Zr-SG 混合体系具有最高的表面碱度。在高压体系和甲苯/水溶剂混合物中进行木糖脱水反应，糠醛产率最高。此外，催化剂的 Zr 含量越高，糠醛的产率越高。因此，尽管 MgZr 混合固体也可能适合具有附加反应步骤的整体过程，但由纯 ZrO₂（尤其是 Zr-SG）组成的催化剂最适合进行所研究的过程。
