Читать книгу High-Performance Materials from Bio-based Feedstocks - Группа авторов - Страница 45

Recently, sugars such as D‐glucose, sucrose, and cellulose have been reported as promising carbon sources for the preparation of catalysts or catalyst supports through various biomass conversion pathways [146]. A solid acid catalyst synthesized from sugar, also known as a sugar catalyst, was shown to be stable and active in many reactions. In particular, a sulfonated carbon‐based solid acid catalyst had outstanding physical properties and was very active in both esterification and hydrolysis reactions. The formation of water‐soluble saccharides could be achieved via the hydrolysis of microcrystalline cellulose (see Figure 2.10) using the sugar‐derived sulfonated solid catalyst. Despite its relatively low surface area of approximately 2 m² g⁻¹, the obtained sulfonated solid catalyst was capable of producing soluble saccharides consisting of 64% β‐1,4‐glucan and 4% glucose even at a low reaction temperature of 100 °C. Its intrinsic adsorption proficiency to attach the β‐1,4‐glucan on the surface likely prompted the catalytic activity, an ability that other solid acid catalysts did not possess. Meanwhile, typical solid acid catalysts, for instance, Amberlyst‐15, H‐mordenite, Nafion, and niobic acid were inactive for this reaction [146].

Figure 2.10 Hydrolysis of cellulose.

Aside from the hydrolysis reaction, a sugar‐derived solid catalyst was found to have potential in biodiesel production by esterification. The D‐glucose‐derived sugar acid catalyst was compared with conventional solid catalysts (sulfated zirconia, Amberlyst‐15, and niobic acid) for its effectiveness to esterify a short‐chain aliphatic alcohol with palmitic acid and oleic acid [147]. The sugar‐derived acid catalyst presented superb thermal stability and the highest activity among other acid catalysts, and its activity was almost the same as a homogeneous acid catalyst. To contribute to the cost‐competition, the sugar catalyst was used in biodiesel production from waste oil with high free fatty acid content (27.8%). It showed prominent performances in the reactivity with a yield of higher than 90%, in spite of the oil containing high amounts of free fatty acids.