Abstract A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural (HMF). Solid state 31P MAS NMR spectroscopic results using trimethylphosphine (TMP) as a probe molecule show that the acid strength and the ratio of Bronsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide. It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Bronsted to Lewis acid sites. Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites. The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity, especially for the catalyst with high ratio of Bronsted to Lewis acid sites. Among them, Ta7W3 oxide catalyst shows 54% HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.

中文翻译：

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在介孔 Ta 和 Ta-W 氧化物固体酸催化剂上将糖脱水成 5-羟甲基糠醛和非化学计量甲酸和乙酰丙酸

摘要 制备了一系列介孔 Ta 和 Ta-W 氧化物并将其用作固体酸催化剂，用于果糖和葡萄糖脱水生成 5-羟甲基糠醛 (HMF)。使用三甲基膦（TMP）作为探针分子的固态 31P MAS NMR 光谱结果表明，随着氧化钽中钨的加入，酸强度和布朗斯台德酸位点与路易斯酸位点的比率逐渐增加。发现在布朗斯台德酸位点与路易斯酸位点的比率相对较高的催化剂上实现了高糖转化率和HMF选择性。可以观察到甲酸相对于乙酰丙酸出乎意料的化学计量过量，这主要是因为果糖在路易斯酸位点上的直接分解。2-丁醇的加入导致糖转化率和HMF选择性的增加，特别是对于布朗斯台德酸位点与路易斯酸位点比例高的催化剂。其中，Ta7W3 氧化物催化剂通过从水相中提取 HMF 并去除沉积在催化剂表面的腐殖质，在加入 2-丁醇后显示出 54% 的 HMF 选择性和良好的可重复使用性。