BaO催化纤维素转化制备乳酸的研究

通过探索水热条件下不同类型固体碱催化剂催化糖及纤维素等转化制乳酸的反应，优选出了直接由Ba（OH）₂焙烧制备的高效固体碱BaO催化剂，进而对反应温度、催化剂用量、底物浓度等实验条件进行了优化，结果表明，在220℃、0.6 MPa N₂压力的水热条件下，BaO（0.8 g）催化纤维素（0.25 g）分解得到的乳酸收率可达75%，反应时间仅7 h。通过傅里叶红外光谱分析及X射线衍射（XRD）表征确定了催化剂组成，进而明确了催化剂的活性组分。最后，对纤维素催化转化机制进行推导后认为：BaO及其水解产生的Ba²⁺作用于纤维素分子间及分子内氢键，促进其断裂，而BaO水合生成的Ba（OH）₂提供了纤维素单体间糖苷键断键、葡萄糖异构及果糖分子内C3-C4键断键所需的碱条件。

Catalytic conversion of cellulose to lactic acid over BaO

The catalytic conversion of sugars and cellulose to lactic acid over solid base catalysts has been investigated. It was found that BaO prepared by direct calcination of Ba(OH)₂ showed the most promising results, and the reaction conditions, such as temperature, catalysts dosage, and substrate concentration, were optimized. The results showed that the lactic acid yield reached 75% when 0.25 g of cellulose and 0.8 g of catalyst were added to 100 mL deionized water under 0.6 MPa N₂ pressure at 220 ℃ after 7 h. FT-IR and XRD analysis were used to confirm the composite of the catalyst and the active components were identified. Finally, a mechanism for cellulose conversion was proposed:1) BaO and Ba²⁺ derived from hydration reactions of BaO facilitated the cleavage of intra- and inter-modecular hydrogen bonds in cellulose, 2) Ba(OH)₂ served as an alkaline catalyst that catalyzed the cleavage of glycosidic linkages between cellulose monomers, isomerization of glucose, and cleavage of the C3-C4 bond in fructose.