Catalytic Conversion of Carbohydrates to Levulinate Ester over Heteropolyanion‐Based Ionic Liquids

Abstract

An efficient one-pot approach for the production of levulinate ester from renewable carbohydrates is demonstrated over heteropolyanion-based ionic liquid (IL-POM) catalysts with alcohols as the promoters and solvents. The relationships between the structure, acidic strength, and solubility of the IL-POM in methanol and the catalytic performance were studied intensively. A cellulose conversion of 100 % could be achieved with a 71.4 % yield of methyl levulinate over the catalyst [PyPS] PW O [PyPS=1-(3-sulfopropyl)pyridinium] at 150 °C for 5 h. This high efficiency is ascribed to the reasonably high activity of the ionic liquid (IL) catalyst and reaction coupling with rapid in situ esterification of the generated levulinic acid with the alcohol promoter, which allows the insolubility of cellulose encountered in biomass conversion to be overcome. Furthermore, the present process exhibits high feedstock adaptability for typical carbohydrates and handy catalyst recovery by a simple self-separation procedure through temperature control.

Biomass valorisation over polyoxometalate-based catalysts

“…44 Furthermore, various POMs have been evaluated for the production of LA or levulinate ester from carbohydrates in consecutive reactions. [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] 46 As shown in Fig. 1, the Brønsted acid sites are proposed to facilitate hydrolysis, isomerization and dehydration/rehydration pathways, while Lewis acid sites are beneficial for isomerization of glucose to fructose.…”

Selective conversion of biomass catalyzed by ionic liquids

“…[PyPS] 3 PW 12 O , PyPS=1-(3-sulfopropyl)pyridinium (其结构如图 中所示)为催化剂, ℃, 反应 5 h 的条件下, 乙酰丙酸甲酯的收率可达到 71% [15] . [16,17] Figure 2 Catalytic conversion of cellulose to platform chemicals in the presence of ionic liquids [16] 除酸性离子液体外, 其它酸和离子液体构成的 复合体系在催化纤维素转化方面的研究也得到了世 界各国研究者的重视.…”

Synthesis and Characterization of Corn Stover-Based Cellulose Triacetate Catalyzed by Ionic Liquid Phosphotungstate

“…During the past decades, the application of heteropolyanion-based ionic liquid (IL-POM) catalysts (including phosphotungstic acid, silicotungstic acid, and phosphomolybdic acid) in the field of catalytic reactions such as esterification, hydrogenation, and oxidation has received extensive attention due to their excellent catalytic performance and the consideration of environmental protection [ 18 , 19 , 20 ]. It is noteworthy that phosphotungstic acid has stronger Brønsted acidity than sulfuric acid; thus, it can show stronger catalytic activity than some traditional inorganic acids in some acid catalytic systems [ 21 ].…”

“…Meanwhile, owing to their inherent structures and physiochemical properties, IL-POMs are usually not miscible with polar solvents at room temperature but miscible at high temperatures [ 22 ]. Therefore, IL-POMs can be used as homogeneous catalysts at appropriate temperatures and then precipitate into a gelatinous solid at low temperatures, providing significant convenience for the separation and recovery of catalysts [ 19 ]. The use of IL-POMs is an effective and sustainable method for the conversion of cellulose and lignocellulosic biomass [ 23 ], and most of the current research on the esterification reaction focuses on the catalytic conversion of cellulose to levulinic acid or levulinic acid ester using IL-POM [ 19 , 22 , 24 ].…”