Conversion Of Microcrystalline Cellulose Research Articles

One-pot conversion of cellulose to HMF under mild conditions through decrystallization and dehydration in dimethyl sulfoxide/tetraethylammonium chloride

As a crucial bio-based platform chemical, the production of 5-hydroxymethylfurfural (HMF) from the abundant substrate cellulose has garnered significant attention. However, tedious reaction steps are inevitable because of the complex tandem conversions of dissolution, hydrolysis, and dehydration. Furthermore, due to the ultralow solubility of cellulose, harsh reaction conditions are inevitable, which can exacerbate HMF degradation. To this end, we investigated the structural changes in microcrystalline cellulose (MCC) after its dissolution and regeneration in various dimethyl sulfoxide (DMSO)/deep eutectic solvents (DESs) to clarify the mechanisms underlying its dissolution. The results revealed that the highly crystalline cellulose I in MCC was converted into amorphous cellulose II after treatment with DMSO/tetraethylammonium chloride (TEAC), which led to the complete dissolution of MCC. Accordingly, a dissolution-catalysis coupling reaction strategy was proposed for converting MCC to HMF via a one-pot method in DMSO/TEAC, simultaneously reducing the number of steps necessary for the reaction and achieving mild reaction conditions. In addition, the pathway for the one-pot reaction was clarified by analyzing the intermediate yields. The combination of AlCl3 as a catalyst and DMSO/TEAC resulted in a notable MCC conversion of 93.3 wt% and a high HMF yield of 53.1%. Remarkably, the reaction conditions employed in this study (130 °C, 1 h) were milder in terms of shorter reaction times and lower temperatures than those reported in most current literature. This was attributed to the complete dissolution of MCC resulting from decrystallization. Therefore, the proposed reaction strategy enabled the efficient production of HMF from cellulose.

Tunable Photoluminescence Properties of Microcrystalline Cellulose with Gradually Changing Crystallinity and Crystal Form.

Nonconventional luminogens with persistent room temperature phosphoresce (p-RTP) are attracting increasing attention owing to their momentous significance and diverse technical applications in optoelectronic and biomedical. So far, the p-RTP emission of some amorphous powders or single crystals has been studied in depth. The p-RTP emission of amorphous and fully crystalline states and their emission properties are widely divergent, while the difference of their p-RTP emission mechanism is still controversial. The relevance between crystallinity change and p-RTP properties is rarely studied. Furthermore, there is almost no research on the photoluminescence (PL) property change and emission mechanism under the crystal form transformation of semi-crystalline polymer. Herein, microcrystalline cellulose (MCC) is chosen as a model compound to explore its crystallinity and the change in luminescence during the crystal form transformation to make up for this gap. By precisely adjusting the crystallinity and crystal cellulose conversion of MCC, the changing trend of quantum efficiency, and p-RTP lifetime is consistent with the change of crystallinity, and the cellulose I may be more beneficial to PL emission than cellulose II. Clustering-triggered emission mechanism can reasonably explain these interesting photophysical processes, which also can be supported by single-crystal analysis and theoretical calculations.

Modulation of cellulase activity by lignin-related compounds

Pretreatment of lignocellulosic biomass generates a wide variety of lignin-related compounds (LRCs) derived from lignin depolymerization, which inhibit the enzymatic saccharification. Here, the effects of different LRCs were evaluated on cellulase activity for the hydrolysis of microcrystalline cellulose. Maximum activation of 110% on microcrystalline cellulose conversion by cellulases was observed with 30 mM syringic acid, whereas 20 mM ferulic acid increased it by 68%. Conversely, maximum inhibition of 40% was observed with 50 mM syringaldehyde. Furthermore, all phenolic acids had their maximum stimulatory effects on cellulase activity before the first 4 h of enzymatic hydrolysis, while syringaldehyde had the maximum inhibition after 12 h of hydrolysis. Activation of cellulases by phenolic acids emerges as a potential tool for lignocellulosic biomass processing for bioenergy and biorefinery.

Ce modified Cu/Zn/Al catalysts for direct liquefaction of microcrystalline cellulose in supercritical methanol

Conventional Cu/Zn/Al catalysts were modified by the incorporation of cerium (Ce) through co-precipitation method, and were then applied to the catalytic liquefaction of microcrystalline cellulose (MCC) in supercritical methanol at 300 °C for 1 h. Catalyst Cu1.2Zn4.8Al1.9Ce0.1 exhibited the best activity, with the MCC conversion of 87.6% and the selectivity of alcohols in liquid products of 88.3% (mainly C4–C7 alcohols), compared with Cu1.2Zn4.8Al2.0 (MCC conversion of 69.62% and alcohol selectivity of 31.37%). The incorporation of CeO2 improved the dispersion of active CuO and its interface interaction with catalyst support, which made the dispersed CuO easier to be reduced at lower temperature, and thus significantly improved catalyst activity and MCC conversion. CeO2 also promoted the performance of the catalyst both in the methanol reforming reaction and the dehydration of intermediates to ketones, which benefited the production of C4–C7 alcohols through the synergism of CeO2 with CuO and ZnO in the Cu-based catalysts. However, excess addition of Ce generated bulk CeO2 crystals on the catalyst surface, which inversely reduced catalyst activity and the production of C4–C7 alcohols.

Hydrolysis of microcrystalline cellulose isolated from waste seeds of Leucaena leucocephala for glucose production

The waste seeds of Leucaena leucocephala (LLS) used in this study were unused residues obtained after oil and polysaccharides extraction. The microcrystalline cellulose (MCC) was isolated from LLS by acid treatment. MCC produced was, then, further converted to glucose by using sulphuric acid at 121 °C by varying the acid concentration and reaction time. The sugar composition was analyzed by using the phenol-sulfuric acid method and pre-column derivatization HPLC technique. The yield of glucose ranging from 70–85% could be obtained from MCC hydrolyzates, depending on the hydrolysis factors, which corresponding to around 57-75% of the percentage conversion of MCC to glucose.Cellulose isolated from LLS was, therefore, potentially suitable to be utilized in liquid biofuels and other value-added chemicals such as bioethanol, 5-hydroxymethylfurfural(HMF), and levulinic acid.

Influence of a Lewis acid and a Brønsted acid on the conversion of microcrystalline cellulose into 5-hydroxymethylfurfural in a single-phase reaction system of water and 1,2-dimethoxyethane.

5-Hydroxymethylfurfural (HMF) is a typical dehydration product of C6 carbohydrates, and it can be converted into a series of chemicals and liquid fuels. In this study, an advanced low-boiling single-phase reaction system consisting of water and 1,2-dimethoxyethane (DMOE) was proposed for the production of HMF from microcrystalline cellulose (MCC). AlCl3 and H3PO4 were selected as the Lewis acidic catalyst and Brønsted acidic catalyst, respectively, and the influence of these two catalysts on the conversion behavior of MCC was studied. The results showed that MCC could be selectively converted into HMF or levulinic acid (LA) by altering the solvent composition. As for the composition of the catalyst, high AlCl3 content favored the generation of HMF, whereas high H3PO4 content could decrease the HMF yield and promote the formation of glucose and fructose. The highest HMF yield of 49.42% was obtained at an AlCl3–H3PO4 ratio of 1 : 0.8. GC-MS analysis suggested that much MCC was transformed into furans and cyclopentenones in the presence of AlCl3, while anhydrosugars tended to be generated with a high H3PO4 proportion in the catalyst. Besides, FTIR analysis of the insoluble humin formed during MCC conversion indicated that AlCl3 could also facilitate the depolymerization of MCC.

Metal-Oxide-Catalyzed Efficient Conversion of Cellulose to Oxalic Acid in Alkaline Solution under Low Oxygen Pressure

Conversion of cellulose into value-added chemicals and/or fuels has attracted worldwide attention due to the dwindling fossil fuel reserves and concerns over global warming. Herein, the conversion of microcrystalline cellulose into oxalic acid in homogeneous NaOH solution catalyzed by metal oxides under low oxygen pressure was reported. The effects of metal oxides, reaction temperature, reaction time, and oxygen pressure on the yields of the major products were studied. The results showed that a high yield of organic acids, mainly including oxalic acid, formic acid, glycolic acid, lactic acid, and acetic acid, could be obtained. Catalytic amounts of CuO could effectively improve the yield of oxalic acid. The yield of the oxalic acid could be as high as 41.5% with catalytic amount of CuO at oxygen pressure of 0.3 MPa and 200 °C for 2 h. A tentative reaction pathway for the selective oxidation of cellulose into small molecular organic acids in aqueous NaOH solution was investigated and proposed.

Improved in situ saccharification of cellulose pretreated by dimethyl sulfoxide/ionic liquid using cellulase from a newly isolated Paenibacillus sp. LLZ1

A cellulase producing strain was newly isolated from soil samples and identified as Paenibacillus sp. LLZ1. A novel aqueous-dimethyl sulfoxide (DMSO)/1-ethyl-3-methylimidazolium diethyl phosphate ([Emin]DEP)-cellulase system was designed and optimized. In the pretreatment, DMSO was found to be a low-cost substitute of up to 70% ionic liquid to enhance the cellulose dissolution. In the enzymatic saccharification, the optimum pH and temperature of the Paenibacillus sp. LLZ1 cellulase were identified as 6.0 and 40°C, respectively. Under the optimized reaction condition, the conversion of microcrystalline cellulose and bagasse cellulose increased by 39.3% and 37.6%, compared with unpretreated cellulose. Compared to current methods of saccharification, this new approach has several advantages including lower operating temperature, milder pH, and less usage of ionic liquid, indicating a marked progress in environmental friendly hydrolysis of biomass-based materials.

Preparation of high crystallinity cellulose nanocrystals (CNCs) by ionic liquid solvolysis

High crystallinity cellulose nanocrystals (CNCs) were successfully prepared from microcrystalline cellulose (MCC) by utilization of 1-butyl-3-methylimidazolium hydrogen sulfate (BmimHSO4) as both catalyst and solvent. Interestingly, it was found that crystallinity of CNCs was improved with increase in temperature which attributed to selective removal of the amorphous phase of cellulose performed at a higher rate with higher temperature. The successful conversion of MCC to CNCs was supported by HRTEM in which the uniform rod-like shape of CNCs was obtained. CNCs with diameter range from 15 to 20 nm and length range from 70 to 80 nm were successfully produced at 90 °C with BmimHSO4. In the present work, CNCs synthesized at different temperatures from 70 °C to 100 °C were investigated. The application of BmimHSO4 as both catalyst and solvent introduced a green chemistry approach as it does not produce any hazardous waste products and is an economical process because the recovery of ionic liquid is high (>90%).

Selective Decomposition of Cellulose into Glucose and Levulinic Acid over Fe-Resin Catalyst in NaCl Solution under Hydrothermal Conditions

The selective decomposition of microcrystalline cellulose (MCC) by Fe-resin (a modified Dowex 50 by cation-exchange) solid catalyst in 5 wt % NaCl solution under hydrothermal conditions has been investigated. The conversion of MCC increases from 24.4% (without catalyst) to 90.9%, and the yield of glucose and levulinic acid (LA) increases from 0.6% and 1.1% (without catalyst) to 38.7% and 33.3%, respectively, under 200 °C for 5 h. The role that Fe-resin/NaCl played in the system is discussed in detail: NaCl could disrupt the hydrogen-bond matrix among cellulose fibers to change highly crystalline cellulose into an amorphous form; Lewis acids on the Fe-resin further boost the depolymerization of amorphous cellulose into water-soluble sugars (WSSs); Fe ions on Fe-resin progressively released into NaCl solution are beneficial to the conversion of WSSs to glucose and LA. A three-step degradation scheme reflecting the main pathways of MCC degradation in the reaction is proposed.

Microwave-assisted conversion of microcrystalline cellulose to 5-hydroxymethylfurfural catalyzed by ionic liquids.

Ionic liquid (IL) has been widely investigated in 5-HMF production from biomass. However, most of studies employed IL as reaction solvent which requires a large amount of IL. In the present study, IL was utilized as catalyst in the conversion of microcrystalline cellulose (MCC) to 5-HMF under microwave irradiation (MI) in N,N-dimethylacetamide (DMAc) containing LiCl. 1,1,3,3-tetramethylguanidine (TMG)-based ILs, including 1,1,3,3-tetramethylguanidine tetrafluoroborate ([TMG][BF4]) and 1,1,3,3-tetramethylguanidine lactate ([TMG]L) which were commonly used in the absorption of SO2 and CO2 from flue gas, were synthesized and applied in the conversion of MCC to 5-HMF for the first time. Of the catalysts employed, [TMG]BF4 showed high catalytic activity in 5-HMF production from MCC. The condition including the ratio of IL to MCC, temperature and time for MCC conversion was optimized using Central Composite Design (CCD) and Response Surface Methodology (RSM). The highest 5-HMF yield of 28.63% was achieved with the optimal condition.

InCl3-ionic liquid catalytic system for efficient and selective conversion of cellulose into 5-hydroxymethylfurfural

In recent decades, 5-Hydroxymethylfurfural (HMF) has been considered as a green platform molecule with a wide range of applications in manufacturing fine chemicals and biofuels. As the most abundant organic material on earth, cellulose has received increasing attention as a potential material for the production of biofuels and bio-based chemicals. Efficient methods for transforming cellulose into HMF need to be developed to achieve the successful commercialization of HMF in the near future. A new process for the efficient and selective conversion of microcrystalline cellulose (MCC) to HMF was developed by using an InCl3-ionic liquid catalytic system. The effect of reaction conditions, such as reaction time, temperature, catalyst dosage, and various acidic ionic liquids were investigated in detail. The results showed that 45.3% HMF yield and 84.6% MCC conversion were obtained with the presence of 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate ([C3SO3Hmim][HSO4]) and dimethylsulphoxide (DMSO) by adding a catalytic amount of InCl3 under atmospheric pressure within 5 h at 160 °C. Recycling of the [C3SO3Hmim][HSO4] and InCl3 catalyst exhibited an almost constant activity during five successive trials. A mechanism was proposed to explain the high activity of InCl3 in [C3SO3Hmim][HSO4].

Catalytic conversion of cellulose to 5-hydroxymethyl furfural using acidic ionic liquids and co-catalyst

Efficient catalytic conversion of microcrystalline cellulose (MCC) to 5-hydroxymethyl furfural (HMF), is achieved using acidic ionic liquids (ILs) as the catalysts and metal salts as co-catalysts in the solvent of 1-ethyl-3-methylimidazo-lium acetate ([emim][Ac]). A series of acidic ILs has been synthesized and tested in conversion of MCC to HMF. The effect of reaction conditions, such as reaction time, temperature, catalyst dosage, metal salts, water dosage, Cu2+ concentration and various acidic ILs are investigated in detail. The results show that CuCl2 in 1-(4-sulfonic acid) butyl-3-methylimidazolium methyl sulfate ([C4SO3Hmim][CH3SO3]), is found to be an efficient catalyst for catalytic conversion of MCC to HMF, and 69.7% yield of HMF is obtained. A mechanism to explain the high activity of CuCl2 in [C4SO3Hmim][CH3SO3] is proposed. To the best of our knowledge, this report first proposes that the Cu2+ and [C4SO3Hmim][CH3SO3] show better catalytic performance in catalytic conversion of MCC to HMF.

Efficient conversion of cellulose into furans catalyzed by metal ions in ionic liquids

5-Hydroxymethylfurfural (HMF) and furfural, two of the most important intermediates derived from biomass, were directly produced from the hydrolysis of microcrystalline cellulose (MCC) with metal ions in ionic liquids as catalyst under mild conditions. Various ionic liquids were tested to obtain the most efficient catalyst, 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1) showed the highest catalytic activity than others, and SO3H-functionalized ionic liquids exhibited better activity than non-functionalized ILs. The co-catalysis effect of Cr3+, Mn2+, Fe3+, Fe2+, Co2+ were much better than other metal ions, with a catalytic amount of these metal ions, MCC conversion increased by 10–19%, and the selectivities of products were also improved obviously. The promoting catalysis of metal nitrates were not as expected as that of chlorides and sulfates, we suggested that nitrate anion may have a negative effect on the hydrolysis of MCC. Reaction conditions were optimized and reaction mechanism was proposed to explain the improved catalysis of metal chlorides and sulfates. Also, the recycling of catalyst was put forward in our system for MCC hydrolysis and these catalysts maintained good performances even after five runs. This simple and effective catalytic system may be valuable to facilitate energy-efficient conversion of cellulose into biofuels and platform chemicals.

Hydrolysis of cellulose in SO3H-functionalized ionic liquids

Influence of acidity and structure of ionic liquids on microcrystalline cellulose (MCC) hydrolysis was investigated. MnCl2-containing ionic liquids (ILs) were efficient catalysts and achieved MCC conversion rates of 91.2% and selectivities for 5-hydroxymethyl furfural (HMF), furfural and levulinic acid (LA) of 45.7%, 26.2% and 10.5%, respectively. X-ray diffractometry indicated that catalytic hydrolysis of MCC in ionic liquids resulted in the changes to MCC crystallinity and transformation of cellulose I into cellulose II. SO3H-functionalized ionic liquids showed higher activities than non-functionalized ILs. The simplicity of the chemical transformation of cellulose provides a new approach for the use this polymer as raw material for renewable energy and chemical industries.

Cellulose Reactivity in Supercritical Methanol in the Presence of Solid Acid Catalysts: Direct Synthesis of Methyl-levulinate

Supercritical MeOH and MeOH−H2O (90/10) mixtures were used as reaction media for one-pot dissolution−conversion of microcrystalline cellulose. In the absence of catalyst, the cellulose dissolution was almost complete under supercritical conditions (300 °C/10 MPa/1 min) but relative low amounts of value-added chemicals were obtained. Addition of solid acid catalysts such as CsxH3−xPW12O40 or sulfated zirconia led in the same conditions to formation of valuable methyl-levulinate in remarkable yields close to 20%.

Catalytic conversion of cellulose to chemicals in ionic liquid

A simple and effective route for the production of 5-hydroxymethyl furfural (HMF) and furfural from microcrystalline cellulose (MCC) has been developed. CoSO 4 in an ionic liquid, 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1), was found to be an efficient catalyst for the hydrolysis of cellulose at 150 °C, which led to 84% conversion of MCC after 300 min reaction time. In the presence of a catalytic amount of CoSO 4, the yields of HMF and furfural were up to 24% and 17%, respectively; a small amount of levulinic acid (LA) and reducing sugars (8% and 4%, respectively) were also generated. Dimers of furan compounds were detected as the main by-products through HPLC-MS, and with the help of mass spectrometric analysis, the components of gas products were methane, ethane, CO, CO 2, and H 2. A mechanism for the CoSO 4-IL-1 hydrolysis system was proposed and IL-1 was recycled for the first time, which exhibited favorable catalytic activity over five repeated runs. This catalytic system may be valuable to facilitate energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.

Hydrolysis of Cellulose by Using Catalytic Amounts of FeCl2 in Ionic Liquids

Microcrystalline cellulose (MCC) is hydrolyzed to an appreciable extent (70 %) by using 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1) as effective catalyst. Valuable chemicals, such as 5-hydroxymethyl furfural (HMF) and furfural, are obtained in relatively high yields (15 % and 7 %, respectively). Interestingly, the introduction of FeCl₂ as catalyst into IL-1 further enhances the catalytic activity, as proved by the higher conversion of MCC (84 %) and higher yields of HMF and furfural (34 % and 19 %, respectively) under the same experimental conditions, although small amounts of levulinic acid (LA) and total reducing sugars (TRS) were also found. The hydrolysis of MCC scarcely proceeded, or showed a lower efficiency, in the absence of catalyst (4 %) or with Al₂O₃ (7 %), inorganic acids (≤65 %), or several other ionic liquids (≤24 %) as catalyst. Dimers of furan compounds were detected as the main byproducts, as analyzed by HPLC-MS; from the mass spectrometry analysis, the components of the gas-phase products were determined to be methane, ethane, CO, CO₂, and H₂. A mechanism to explain the high activity of FeCl₂ in the IL-1 system is proposed. Recycling of the IL-1 catalyst showed an almost constant activity during five successive trials. The simple and effective catalyst system may prove valuable in facilitating the energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.