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首页> 外文期刊>Catalysis science & technology >SnCl4-catalyzed isomerization/dehydration of xylose and glucose to furanics in water
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SnCl4-catalyzed isomerization/dehydration of xylose and glucose to furanics in water

机译：Sncl4催化的异构化/木糖和葡萄糖脱水至水中

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摘要

A number of Lewis acid catalysts were screened for their effectiveness in converting both xylose and glucose in aqueous media to furfural and 5-HMF, respectively. While other catalysts were found to be more active, SnCl4 was identified as the most selective Lewis acid. Hydrolysis of SnCl4 was observed at various concentrations and temperatures resulting in the production of Bronsted acidic protons in a 3.5 : 1 ratio to Sn4+ at all SnCl4 concentrations above 60 degrees C. As a consequence, there was no need to add a Bronsted acid in order to promote the dehydration of either xylose or glucose. SnCl4-promoted isomerization/dehydration of xylose and glucose at 140 degrees C in water resulted in conversions of 55% and 33%, respectively, after 2 h of reaction, and furfural and 5-HMF selectivities of up to 58% and 27%, respectively. Significant conversion of sugars to humins was observed in both cases, and in the case of glucose, degradation of 5-HMF to levulinic and formic acids was also noted. The effects of secondary reactions could be greatly suppressed by extraction of the furanic product as it was produced. Using n-butanol as the extracting agent, xylose and glucose conversions of 90% and 75%, respectively, were observed after 5 h of reaction, and the selectivities to furfural and 5-HMF increased to 85% and 69%, respectively. Small additional increases in the furfural and 5-HMF selectivities were obtained by adding LiCl to the aqueous phase without much effect on the conversion of either sugar. In this case, the selectivities to furfural and 5-HMF were 88% and 72%, respectively, after 5 h of reaction at 140 degrees C.
机译：筛选了许多刘易斯酸催化剂，分别在水性培养基中转化木糖和葡萄糖分别为呋喃和5-HMF方面的有效性。尽管发现其他催化剂更活跃，但SNCL4被鉴定为最选择性的路易斯酸。在各种浓度和温度下观察到SNCL4的水解，导致在60度以上的所有SNCL4浓度下以3.5：1的比率与Sn4+的产生。促进木糖或葡萄糖的脱水。在水中2小时，SNCL4促进的异构化/脱水在140摄氏度下，在水中分别导致55％和33％的转化，以及呋喃神经和5 HMF的选择性高达58％和27％，高达58％和27％分别。在两种情况下都观察到糖向humins的显着转化，并且在葡萄糖的情况下，还发现了5-HMF向葡萄糖降解，并注意到甲酸和甲酸。通过产生的Furanic产物的提取可以极大地抑制次级反应的影响。在反应5小时后，使用N-丁醇作为提取剂，分别观察到90％和75％的木糖和葡萄糖转化率，分别对呋喃酸盐和5-HMF的选择性分别增加到85％和69％。通过将LICL添加到水相中，可以获得呋喃和5-HMF选择性的少量增加，而对任何一种糖的转化都没有太大影响。在这种情况下，在140度的反应5小时后，对呋喃的选择性和5-HMF分别为88％和72％。

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