The isomerization of glucose-containing hydrolysates to fructose is a key step in the process from lignocellulosic biomass to the platform chemical hydroxymethylfurfural. We investigated the isomerization reaction of glucose to fructose in water catalyzed by hydrotalcite. Catalyst characterization was performed via IR, XRD, and SEM. Firstly, glucose solutions at pHneutral conditions were converted under variation of the temperature, residence time, and catalyst loading, whereby a maximum of 25 wt.% fructose yield was obtained at a 38 wt.% glucose conversion. Secondly, isomerization was performed at pH = 2 using glucose solutions as well as glucose-containing hydrolysates from lignocellulosic biomass. Under acidic conditions, the hydrotalcite loses its activity for isomerization. Consequently, it is unavoidable to neutralize the acidic hydrolysate before the isomerization step with an inexpensive base. As a neutralizing agent NaOH is preferred over Ba(OH)₂, since higher fructose yields are achieved with NaOH. Lastly, a pH-neutral hydrolysate from lignocellulose was subjected to isomerization, yielding 16 wt.% fructose at a 32 wt.% glucose conversion. This work targets the application of catalytic systems on real biomass-derived samples.

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使用水滑石将木质纤维素生物质水解产物中的葡萄糖异构化为果糖

含葡萄糖的水解产物异构化为果糖是从木质纤维素生物质到平台化学羟甲基糠醛的关键步骤。我们研究了水滑石催化水中葡萄糖与果糖的异构化反应。经由IR，XRD和SEM进行催化剂表征。首先，在pH中性条件下的葡萄糖溶液在温度，停留时间和催化剂负载的变化下转化，由此在38wt。％的葡萄糖转化率下获得最大25wt。％的果糖产率。其次，使用葡萄糖溶液以及来自木质纤维素生物质的含葡萄糖的水解产物在pH = 2下进行异构化。在酸性条件下，水滑石失去了其异构化活性。所以，在异构化步骤之前用廉价的碱中和酸性水解产物是不可避免的。作为中和剂，NaOH优于Ba（OH）_{如图2所示}，因为用NaOH获得更高的果糖产率。最后，将来自木质纤维素的pH中性水解产物进行异构化，在32wt。％的葡萄糖转化率下产生16wt。％的果糖。这项工作的目标是将催化系统应用于真实的生物质样品。