Effect of NaCl on the conversion of cellulose to glucose and levulinic acid via solid supported acid catalysis

Cellulose is hydrolyzed to glucose, which is further converted to levulinic acid in the presence of Nafion, as a surface supported acid catalyst. The addition of simple alkali metal halide salts, including NaCl, provides significant enhancement to the yield. The catalyst can be recycled suggesting possible extension into a continuous flow reactor for the synthesis of the biofuel precursors.     

Selective conversion of cellulose to levulinic acid and furfural in sulfolane/water solvent

Direct conversion of cellulose into levulinic acid and furfural in sulfolane media with the aid of water and H₂SO₄ was performed at 140–220 °C under the pressures of 0–1.5 MPa. This approach could obtain 72.5 mol% levulinic acid and 11.5 mol% furfural formation under an optimal condition in which the mass ratio of sulfolane, water and H₂SO₄ was 90:10:1. It was found that the decrease of water content led to an increasing yield of furfural and that the maximum furfural yield (51.1 mol%) could be obtained in the absence of water. The synergism of sulfolane and water in the selective liquefied system was demonstrated to be responsible for not only reinforced effect of optimizing and isolating the target products but also for reducing re-polymerization and side reactions. Furthermore, sulfolane in our case could be recycled and re-used for the conversion of cellulose with the same yield, which shed light on the remarkable potential for future industrial application.     

Valorization of decationized newsprint to levulinic acid

Cellulose - As of today, most chemical products are fossil-based. The environmental concerns of fossil resources due to their constant misuse have led to the exploration of bio-based alternatives....     

Catalytic transformations of cellulose and its derived carbohydrates into 5-hydroxymethylfurfural,levulinic acid,and lactic acid

The catalytic transformation of cellulose into key building-block or platform chemicals such as 5-hydoxymethylfurfural(HMF),levulinic acid,and lactic acid under mild conditions,has attracted much attention in recent years,as these conversions can be operated without consumption of hydrogen or oxygen and thus are more economical compared to the hydrogenolysis or oxidation of cellulose.This review article highlights recent advances in the development of novel catalysts or catalytic processes for the conversion of cellulose and its derived carbohydrates into HMF,levulinic acid,and lactic acid or their esters under inert atmosphere.We also analyze efficient catalytic systems for HMF production,in particular Lewis acids combined with ionic liquid or biphasic systems.For the formations of levulinic and lactic acids or their esters,we focus on the reactions in aqueous and alcohol media catalyzed by multifunctional catalysts that combine the functions of hydrolysis,isomerization,and dehydration-rehydration or retro-aldol reactions.The reaction mechanism for each process will also be discussed to gain insights into the activation of C–O and C–C bonds in the absence of hydrogen or oxygen.     

Synthesis of biofuel via levulinic acid esterification over porous solid acid consisting of tungstophosphoric acid and reduced graphene oxide

Research on Chemical Intermediates - Reduced graphene oxide (rGO) was synthesized by chemical reduction of graphene oxide with hydrazine hydrate and used as supports to prepare a series of...     

Mechanism of levulinic acid formation

Based on the intermediates revealed by ¹³C-NMR spectroscopy, the mechanism of levulinic acid ($\text{6}$) formation in acid catalysed hydrolysis of 2-hydroxymethylfurane ($\text{1}$) and 5-hydroxymethylfuran-2-carbaldehyde ($\text{14}$) is proposed.     

Enantio- and diastereoselective addition of thioacetic acid to nitroalkenes via N-sulfinyl urea catalysis

The enantioselective addition of thioacetic acid to nitroalkenes was achieved using N-sulfinyl urea catalysis. In this report, the scope of the reaction was extended to the enantio- and diastereoselective thioacetic acid addition to cyclic α,β-disubstituted nitroalkenes. Additionally, the role of the sulfinyl group was investigated by replacing it with a variety of aryl and sulfonyl groups. Of 15 urea catalysts synthesized and tested, none displayed comparable selectivity to the sulfinyl catalysts, highlighting the importance of the sulfinyl group in attaining high enantioselectivity in the thioacetic acid addition.     

Conversion of cellulose Iα to Iβ via a high temperature intermediate (I-HT) and other cellulose phase transformations

The observation that the hydrothermal conversion of cellulose Iα to cellulose Iβ is irreversible has been assumed to be due to the relative free energy of these polymorph phases. We propose an alternative explanation: when cooling the high temperature phase, the barrier to forming Iβ is much smaller than the barrier to forming Iα, so kinetics favor the formation of Iβ. This explanation is consistent with all available experimental data, and is consistent with the general observation of polymer solid–solid phase transformations via metastable intermediate states. While cellulose Iβ may be lower in free energy than Iα, this has not been shown experimentally. Phase transformations of other cellulose polymorphs may be subject to similar kinetic effects when converted via metastable intermediate states.     

Gold catalysis on immobilized substrates: a heteroannulation approach to the solid-supported synthesis of indoles

A gold-catalyzed cyclization of immobilized 2-alkynylanilines was developed as the key step in the synthetic sequence for the preparation of 2-substituted indoles. These results demonstrate the potential of the unexplored combination of gold catalysis and solid-phase organic synthesis.     

Conformational and thermodynamic properties of gaseous levulinic acid

Molecular modeling is used to determine low-energy conformational structures and thermodynamic properties of levulinic acid in the gas phase. Structure and IR vibrational frequencies are obtained using density functional and M?ller-Plesset perturbation theories. Electronic energies are computed using G3//B3LYP and CBS-QB3 model chemistries. Computed anharmonic frequencies are consistent with reported experimental data. Population analysis shows a boat- and a chainlike structure to be most abundant at 298 K, with increasing proportions of two other conformers at higher temperatures. Population mean distribution values for thermodynamic quantities are derived. At 298 K and 1 atm, the enthalpy of formation, entropy, and heat capacity are -613.1 ± 1.0 kJ·mol(-1), 407.4 J·mol(-1)·K(-1), and 132.3 J·mol(-1)·K(-1), respectively.     

Supramolecular acid/base catalysis via multiple hydrogen bonding interaction

2-Ureidoisocytosine bearing a phosphonium ion functionality self-assembles in an anti-parallel manner, to exhibit a cooperative acid/base catalysis for the ring-opening reaction of an epoxide.     

猪去氧胆酸化学 III: 猪去氧胆酸转变成鹅去氧胆酸和熊去氧胆酸

在从猪去氧胆酸合成熊去氧胆酸和鹅去氧胆酸时, 其关键是在羟基移位的一系列反应中保留5β构型. 本文报导了应用1,2-酮基移位反应, 实现上述转化的过程.     

Oxidative decarboxylation of levulinic acid by cupric oxides

In this paper, cupric oxides was found to effectively oxidize levulinic acid (LA) and lead to the decarboxylation of levulinic acid to 2-butanone. The effects of cupric oxide dosage, reaction time and initial pH value were investigated in batch experiments and a plausible mechanism was proposed. The results showed that LA decarboxylation over cupric oxides at around 300 °C under acidic conditions produced the highest yield of butanone (67.5%). In order to elucidate the catalytic activity of cupric oxides, XRD, AFM, XPS and H(2)-TPR techniques was applied to examine their molecular surfaces and their effects on the reaction process.     

Renewable platform-chemicals and materials: Thermochemical study of levulinic acid

The standard molar enthalpy of formation in the gaseous state (?613.5 ± 2.2) kJ · mol^?1 of levulinic acid has been obtained from combustion calorimetry and results from the temperature dependence of the vapour pressure measured by the transpiration method. In order to verify the experimental data, first-principles calculations have been performed. Enthalpies of formation derived from G4 and G3MP2 methods are in an excellent agreement with the experimental results. Thermodynamic analysis of the hydrolysis of 5-hydroxymethylfurfural to the levulinic and formic acids has revealed very high feasibility of these reactions with equilibrium constants completely shifted to the desired reaction products even at T = 298.15 K.     

Preparation and characterization of nanocrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis

Nanocrystalline cellulose (NCC) was extracted from microcrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis process. NCC samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size distribution (PSD) analysis, Fourier-transformed infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and rheological measurement. It was found that NCC yield reached 40.4 % under the optimum process of low-intensity ultrasonic-assisted sulfuric acid hydrolysis, while it was only 33.0 % in the absence of ultrasonic treatment. Furthermore, the results showed that the two NCC samples obtained from ultrasonic-assisted hydrolysis and conventional hydrolysis were very similar in morphology, both exhibiting rod-like structures with widths and lengths of 10–20 and 50–150 nm, respectively. XRD result revealed that the NCC sample from ultrasonic-assisted hydrolysis contained a small amount of cellulose II and possessed a Segal Crystallinity Index of 90.38 % and a crystallite size of 58.99 Å, higher than those of the NCC sample from conventional hydrolysis. Moreover, PSD analysis demonstrated that the former exhibited a smaller value in average particle size than the latter. In addition, rheological measurements showed that the NCC suspensions from the ultrasonic-assisted process exhibited a lower viscosity over the range of shear rate from 0.1 to 100 s^?1 in comparison with that prepared in the absence of ultrasonic treatment.     

Reactions of levulinic acid and pseudolevulinic esters with various C-nucleophiles

The reactions of levulinic acid and its pseudo esters, which are readily available from carbohydrate-containing raw materials, with various C-nucleophiles are described. Different reaction pathways were demonstrated depending on the nature of the leaving groups and nucleophiles. For 5-methyl-5-methoxydihydrofuran-2(3H)-one, the reaction was found to proceed by a route giving hept-6-enoic acid derivatives. In contrast, the reaction of 2-methyl-5-oxotetrahydrofuran-2-yl acetate proceeds via intramolecular cyclization to form γ-valerolactone derivatives.     

Esterification of levulinic acid to n-butyl levulinate over heteropolyacid supported on acid-treated clay

Levulinic acid has been identified as a promising green, biomass-derived platform chemical. n-Butyl levulinate is used as an important intermediate having diverse applications. The present work focuses on the synthesis of n-butyl levulinate by esterification of levulinic acid with n-butanol using heteropolyacid (HPA) supported on acid-treated clay montmorillonite (K10). 20% (w/w) dodecatungestophosphoric acid (DTPA) supported on K10 was found to be the most efficient catalyst with 97% levulinic acid conversion and 100% selectivity towards n-butyl levulinate. Effects of various process parameters were studied to examine the efficacy of 20% (w/w) DTPA/K10 for optimization of the activity.     

A new method for the synthesis of levulinic acid

A two- step method is described for the synthesis of levulinic acid from ethyl acetoacetate and ethyl chloroacetate in 70% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 474–475, February, 1990.     

钼多金属氧酸盐催化微晶纤维素水解制备葡萄糖的研究

合成了8种基于Mo₈O₂₆的钼多金属氧酸盐,采用红外(FT-IR)和核磁共振(NMR)对其结构进行表征,并将其应用于催化纤维素水解。以离子液体1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)为溶剂进行微晶纤维素(MCC)水解反应,考察催化剂及其用量、反应温度、反应时间等条件对水解反应的影响。研究结果表明,本文所制备的钼多金属氧酸盐对微晶纤维素水解反应均具有较好的催化活性。在微波辅助加热条件下,当催化剂[(CH₃)₄N]₄Mo₈O₂₆用量为10 wt%,在170 ℃反应20 min时,纤维素可完全转化,微晶纤维素TRS和葡萄糖收率最高分别为84.5% 和41.5 %。     

Simple and efficient synthesis of 3,4-dihydro-2-pyridones via novel solid-supported aza-annulation

A diverse array of 3,4-dihydro-2-pyridones 13 were produced utilizing the unique properties of solid-supported reactions to both drive the reactions to completion and isolate the desired products. The pyridones were synthesized in high purity by a simple sequence of novel steps commencing from an acetophenone-functionalized resin. The para-substituted acetophenone 9 could be anchored to the resin through either a sulfonamide or a carboxamide linkage. The sulfonamide resin 9a, which gave the best results, was treated with several aryl aldehydes and ethoxide to give a variety of chalcones 10a-k in excellent yield (82-99%) upon TFA cleavage. Addition of either methyl or allyl malonate and DBU to 10a-k afforded smoothly the Michael adducts 11a-j (70-99%) which were subsequently cyclized in one step employing acetic acid as a catalyst and several diverse amines to give pure 3,4-dihydro-2-pyridones 13a-p in moderate to excellent yields (30-98%).