Search

The isomerization of glucose to fructose is the rate determining step in many techniques for chemo‐catalytic conversion of cellulosic biomass to highly value‐added biochemicals. However, current techniques are generally challenging by poor process efficiency, low fructose yield and selectivity, etc. Therefore, the exploitations of novel catalytic systems for the efficient isomerization of glucose are important and highly desired. Herein, a series of biodegradable guanidinium ionic liquids were synthesized and employed in the selective isomerization of glucose to fructose. The results demonstrated that the performance of the isomerization of glucose was significantly influenced by the basic strength of the ionic liquids and the reaction conditions involving catalyst dosage, reaction temperature, time, and solvent. At the optimized conditions of 80 °C for 30 min, an impressive fructose yield of 34.1 % could be obtained in the presence of tetra methyl guanidinium proline ([TMG]Pro). Furthermore, the kinetic behavior of the process was further studied, and the apparent activation energy was 57±2 KJ/mol, which is lower than most current base‐catalyzed glucose isomerization systems. Moreover, the results of isotope labeling experiments showed that this aqueous isomerization of glucose was proceeded via a deprotonation mechanism. Therefore, this work provides a new insight on the selective isomerization of glucose. [ABSTRACT FROM AUTHOR]

Catalytic valorization of renewable aromatic lignin is attracting increasing attention. In this study, an efficient method for direct liquefaction of sugarcane bagasse lignin using acidic ionic liquid (IL) 1-(4-sulfobutyl)-3-methyl imidazolium hydrosulfate ([C4H 8 SO 3 Hmim]HSO 4 ) is presented. The relationships between catalyst dosage, reaction condition parameters and degree of liquefaction, and the structure and elemental composition of liquefaction residue were investigated. The transformation performances of three molecular structural units (guaiacyl, syringyl, and hydroxyphenyl units) of bagasse lignin were also intensively examined using gas chromatography-mass spectrometry, elemental analysis, Fourier transform infrared spectrometry, and proton nuclear magnetic resonance characterization. The results demonstrated that the dual-functionalized acidic IL exhibited excellent catalytic performance in the direct liquefaction process. More than 65% degree of liquefaction was achieved under optimized conditions, yielding 13.5% of useful aromatic fine chemicals such as phenol, 4-ethylphenol, and guaiacol. The p- hydroxyphenyl unit of lignin was the most flexible, followed by the guaiacyl unit, whereas the syringyl group was the most refractory. Furthermore, the catalytic mechanism was proposed. [ABSTRACT FROM AUTHOR]

Abstract: Esterification of aliphatic acids with alcohols was studied using a series of Brønsted acidic ionic liquids as catalysts. The results indicate that five SO3H-functionalized ionic liquids show high catalytic activity and fair reusability even at very low catalyst loadings, while the conventional non-functionalized ionic liquids show poor activity. Hammett method was used to determine the acidity of the ionic liquids and the results were found to be relevant to the catalytic activity observed in the esterification reactions. [Copyright &y& Elsevier]

Highlights • An efficient strategy is provided for methyl levulinate production from duckweed. • Dual functionalized IL [C 3 H 6 SO 3 HPy]HSO 4 is effective for duckweed conversion. • 88.0% conversion and 73.7% methyl levulinate yield are shown at 170 °C for 5 h. • Duckweed liquefaction and methyl levulinate yield are highly temperature dependent. • Solvent has an obvious intensified effect on process efficiency via esterification. Abstract In this study, an efficient strategy is proposed for selective methyl levulinate production from duckweed, a typical fast-growing aquatic microalgae in warm and humid regions, in the presence of acidic ionic liquids (ILs). The results show that IL structure has a significant effect on its acidic strength, which finally determines the process efficiency for levulinate methyl generation. With the optimized catalyst of [C 3 H 6 SO 3 HPy]HSO 4 , 88.0% duckweed is consumed, resulting in a comparable methyl levulinate yield of 73.7% and a process efficiency of 81.8% at 170 °C for 5 h. Furthermore, this process is substantially influenced by the reaction condition, particularly, it is significantly temperature-dependent. In addition, solvent has a remarkable intensified effect on the process efficiency, which dramatically decreases from 81.8 to 53.7% when methanol is replaced by water. [ABSTRACT FROM AUTHOR]

Lignin has been considered as a promising sustainable feedstock for high value-added aromatic chemical production. Here, we propose a novel and efficient process for lignin depolymerization in the presence of cooperative ionic liquid pair, which affords excellent catalytic activity and char inhibition capability. Under the optimized reaction condition, 66.7% lignin conversion is achieved, yielding 14.5 wt.% phenolic monomer, numerous volatile products (identified by GC–MS) and negligible char formation. The structural evolution of the sugarcane lignin was intensively investigated via comparative characterization of raw and regenerated lignin using HSQC, 1 H NMR, FT-IR, GPC and elemental analysis. All three structural lignin units are degraded in this process, where, H-lignin is found to be the most susceptible. Satisfactory lignin depolymerization performance was found for the cooperative ionic liquid system, even after the fifth run, demonstrating a reasonable reusability. [ABSTRACT FROM AUTHOR]