Cellulose, which is the largest component of renewable biomass raw materials, can be transformed into a series of top value-added molecular organic acids, such as glycolic acid (GlycA), formic acid (FA), lactic acid (LacA), etc. Hexoses are intermediates in cellulose conversion, among which glucose is a key component in controlling the formation of GlycA. Selective conversion of glucose into GlycA remains a challenge because glucose–fructose isomerization followed by fructose dehydration and [3 + 3] retro-aldol reactions occurs easily in a thermodynamic reaction in acidic catalytic systems, resulting in the formation of 5-HMF, FA, LacA, levulinic acid (LevA), etc. In this study, density functional theory (DFT) results verified that D-glucopyranose (as a model of cellulose) was easily converted to fructose and then dehydrated to 5-HMF without a catalyst. Subsequently, the effects of different reaction conditions on glucose conversion were compared with or without a catalyst. The results showed that the Wells–Dawson phosphomolybdic heteropolyacid H₆P₂Mo₁₈O₆₂ (PMo), a green solid acid, had high activity and selectivity in the epimerization of glucose into mannose and the [2 + 4] retro-aldol reaction of glucose/mannose in water, and the highest yield of GlycA was 13.58% over 0.03 g PMo at 180 °C for 60 min, which was far higher than that without a catalyst (<2% yield). This study lays a foundation for biomass conversion into GlycA in the chemical industry using Wells–Dawson heteropolyacids.

中文翻译：

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Wells-Dawson 磷钼杂多酸对葡萄糖转化为乙醇酸的影响

纤维素是可再生生物质原料的最大成分，可转化为一系列高附加值的分子有机酸，如乙醇酸（GlycA）、甲酸（FA）、乳酸（LacA）等。己糖是纤维素转化的中间体，其中葡萄糖是控制 GlycA 形成的关键成分。葡萄糖选择性转化为 GlycA 仍然是一个挑战，因为葡萄糖 - 果糖异构化，随后果糖脱水和 [3 + 3] 逆羟醛反应在酸性催化系统的热力学反应中很容易发生，导致形成 5-HMF、FA、 LacA、乙酰丙酸（LevA）等本研究中，密度泛函理论（DFT）结果验证了D-吡喃葡萄糖（作为纤维素的模型）很容易转化为果糖，然后在没有催化剂的情况下脱水为 5-HMF。随后，比较了不同反应条件对葡萄糖转化率的影响，有无催化剂。结果表明，Wells-Dawson 磷钼杂多酸 H ₆ P ₂ Mo ₁₈ O ₆₂(PMo)是一种绿色固体酸，在葡萄糖差向异构化为甘露糖和葡萄糖/甘露糖在水中的[2+4]逆羟醛反应中具有较高的活性和选择性，GlycA的最高产率为13.58%，超过0.03 g PMo 在 180 °C 下保持 60 分钟，远高于没有催化剂的情况（<2% 产率）。该研究为化学工业中使用 Wells-Dawson 杂多酸将生物质转化为 GlycA 奠定了基础。