Dehydration Of Cellulose Research Articles

ChemInform Abstract: Advances in the Conversion of Glucose and Cellulose to 5‐Hydroxymethylfurfural over Heterogeneous Catalysts

AbstractReview: [116 refs.

Layer-by-layer self-assembly for carbon dots/chitosan-based multilayer: Morphology, thickness and molecular interactions

Oxidized Carbon dots, prepared from the acid dehydration of cellulose, were used in the preparation of self-assembled films with the biopolymer chitosan. The morphology, thickness and molecular interactions of the films were characterized with a variety of techniques including AFM, FTIR, UV–Vis and Surface Plasmon Resonance (SPR) spectroscopy. We noticed an increase in the thickness of the bilayers with increasing ionic strength and pH provided by the increase of the amount of CD and chitosan deposited in each cycle. This increase was mainly due to higher flexibility of the biopolymer on these conditions and to the formation of agglommerates of carbon dots in high ionic strength. On the other hand, the greater flexibility together with the higher adsorption have generated films with smoother morphology due to the higher coating on the spherical particles. The results described here suggest that the structure of the film, i.e., morphology and thickness can be easily controlled and reproduced, by controlling the conditions of the biopolymer and CD solutions, in addition to the traditional number of dips. Finally, the prepared films have potential application in the development of imunosensors, functional coatings, surface photoactive and UV protection films.

The Reductive Dehydration of Cellulose by Solid/Gas Reaction with TiCl4 at Low Temperature: A Cheap, Simple, and Green Process for Preparing Anatase Nanoplates and TiO2 /C Composites.

Metal oxides and metal oxide/carbon composites are entering the development of new technologies and should therefore to be prepared by sustainable chemistry processes. Therefore, a new aspect of the reactivity of cellulose is presented through its solid/gas reaction with vapour of titanium(IV) chloride in anhydrous conditions at low temperature (80 °C). This reaction leads to two transformations both for cellulose and titanium(IV) chloride. A reductive dehydration of cellulose is seen at the lowest temperature ever reported and results in the formation of a carbonaceous fibrous solid as the only carbon-containing product. Simultaneously, the in situ generation of water leads to the formation of titanium dioxide with an unexpected nanoplate morphology (ca. 50 nm thickness) and a high photocatalytic activity. We present the evidence showing the evolution of the cellulose and the TiO2 nanostructure formation, along with its photocatalytic activity. This low-temperature process avoids any other reagents and is among the greenest processes for the preparation of anatase and also for TiO2 /carbon composites. The anisotropic morphology of TiO2 questions the role of the cellulose on the growing process of these nanoparticles.

Advances in the conversion of glucose and cellulose to 5-hydroxymethylfurfural over heterogeneous catalysts

This review provides a holistic overview of the developed heterogeneous catalysts for HMF production from dehydration of glucose and cellulose in various solvent systems.

Microwaves in Catalysis: Methodology and Applications

The hydrolysis/dehydration of glucose and cellulose to 5-hydroxymethylfurfural (HMF) catalyzed by alkaline earth phosphates was investigated under hot compressed water condition. The catalysts were synthesized by reactions of CaCO3 or SrCO3 with ortho-H3PO4 via conventional precipitation method in acetone–water media system. The experimental results revealed that the calcination temperature greatly influenced the crystalline phases of the catalysts and the catalytic activity. The calcium and strontium phosphate catalysts without calcination are Ca(H2PO4)·H2O and Sr(H2PO4)2, respectively. The calcium phosphate catalysts calcined at 600 and 900 °C are β-CaP2O6 while the strontium phosphate catalysts display Sr2(PO3)4, and α-Sr(PO3)2, respectively. The incorporation of Ca and Sr into phosphate network of calcined samples can further improve catalytic performance. Among all synthesized catalysts, the α-Sr(PO3)2 calcined at 900 °C showed the best catalytic activity, providing the HMF yield of 21.0% from glucose dehydration and total yield of glucose and HMF of 34.8% from hydrolysis coupling dehydration of cellulose.

A new understanding concerning the influence of structural changes on the thermal behavior of cellulose

A study has been made on an attempt to further expand the current knowledge in melt processing of cellulose. The basic idea is that a few zinc compounds may remain in the regenerated cellulose by formation of a zinc-cellulose complex and hydrolysis reaction when ZnCl2 molten hydrates are used as a solvent for cellulose. The chance is that zinc compounds may act as isolation agents to destroy the hydrogen bonding and reduce the crystallinity of cellulose. Interesting results revealed that the raw cellulose and regenerated celluloses in our work showed different structures and other, but specific, thermal behavior, admitting that the melting of cellulose was not detected. The results are preliminary but demonstrate that simply destroying the hydrogen bonding and reducing the crystallinity will promote the dehydration of cellulose at a lower temperature, since the activity of the cellulose hydroxyls would be improved unexpectedly in that condition. It is expected that this study will stimulate some new ideas to make some progress in the melt processing of this material.

Functionalized ionic liquids supported on silica as mild and effective heterogeneous catalysts for dehydration of biomass to furan derivatives

A series of functional ionic liquid supported silica nanoparticles with different acidity (ILs/SiO2) have been prepared by covalent bonds using novel, non-toxic ethanol as solvent. Compared with using toluene or acetonitrile as solvent in traditional prepared method, the process represents a green, environmental friendly route to synthesize supported functional ionic liquid catalysts (SFILCs). These SFILCs, with the benefits of ionic liquid and the advantages of immobilization, were first systematically utilized in biomass dehydration reactions and proved to be efficient heterogeneous catalysts for the preparation of furan derivatives from various carbohydrates. However, the supported dual acidic functional ionic liquid catalyst (3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate) was found to be more active and selective than other ILs/SiO2 and the conversion of fructose, glucose, xylose, sucrose, cellobiose was up to 99, 96, 94, 76 and 99%. Moreover, the reducing sugar (TRS) yield of microcrystalline cellulose dehydration was up to 77%.

Hybrid heterostructures based on hematite and highly hydrophilic carbon dots with photocatalytic activity

Highly hydrophilic carbon dots (HCD) prepared by dehydration and oxidation of cellulose were used in preparation of hybrid heterostructures with αFe2O3 in aqueous medium. The nanostructures were characterized by different techniques including XRD, Mossbauer spectroscopy, TG, HRTEM, FTIR, Raman, potentiommetry titration and cyclic voltammetry. The formation of a hybrid heterojunction was shown by determining the energy of the top of the valence band and the bottom of the conduction band through voltammetric measurements and electronic spectroscopy. These results indicate that the hybrid material exhibits Type II band offsets that are able to promote an efficient separation of photogenerated charges under irradiation of visible light. The photocatalytic activity of the heterojunction was evaluated in the photodegradation of indigo carmine dye. The high photocatalytic activity observed under visible light is discussed on basis of the coupling of the hybrid heterojunction band structure.

Dehydration of cellulose to levoglucosenone using polar aprotic solvents

Herein, we report an approach to produce levoglucosenone (LGO) from cellulose in yields up to 51% under mild reaction conditions (170–230 °C; 5–20 mM H2SO4) using polar, aprotic solvents such as tetrahydrofuran (THF).

Effect of calcination temperature on catalytic performance of alkaline earth phosphates in hydrolysis/dehydration of glucose and cellulose

The hydrolysis/dehydration of glucose and cellulose to 5-hydroxymethylfurfural (HMF) catalyzed by alkaline earth phosphates was investigated under hot compressed water condition. The catalysts were synthesized by reactions of CaCO3 or SrCO3 with ortho-H3PO4 via conventional precipitation method in acetone–water media system. The experimental results revealed that the calcination temperature greatly influenced the crystalline phases of the catalysts and the catalytic activity. The calcium and strontium phosphate catalysts without calcination are Ca(H2PO4)·H2O and Sr(H2PO4)2, respectively. The calcium phosphate catalysts calcined at 600 and 900°C are β-CaP2O6 while the strontium phosphate catalysts display Sr2(PO3)4, and α-Sr(PO3)2, respectively. The incorporation of Ca and Sr into phosphate network of calcined samples can further improve catalytic performance. Among all synthesized catalysts, the α-Sr(PO3)2 calcined at 900°C showed the best catalytic activity, providing the HMF yield of 21.0% from glucose dehydration and total yield of glucose and HMF of 34.8% from hydrolysis coupling dehydration of cellulose.

Cotton fabric coated with intumescent formulation containing polymers and inorganic additives: Thermal and flammability behaviour

This work was focused on the development of flame retardant cotton fabric by coating with intumescent formulations containing different polymers and inorganic additives. The thermal degradation study was carried out using thermogravimetric and differential scanning calorimeter techniques, and the flame retardancy behaviour was evaluated by auto flammability and limiting oxygen index tests. Coated cotton fabric samples give rise to high char yields on heating with lower degradation temperature at the expense of volatile products. The action of intumescent coating materials was found concurrent with the process of decomposition of cotton fabric on heating. The FTIR spectra of chars of coated cotton fabric indicated the catalyzed dehydration of cotton cellulose and contribution of phosphorus for formation of carbonaceous char. The coated cotton fabric samples have achieved better flame retardant properties and were not ignited during auto flammability test.

One-pot synthesis of 5-hydroxymethylfurfural directly from cottonseed hull biomass using chromium (III) chloride in ionic liquid

We studied the direct synthesis of 5-hydroxymethylfurfural (5-HMF) from cottonseed hull biomass under acid condition in one-pot. The influence of HCl dosage, reaction temperature and time, CrCl3·6H2O amount, and cottonseed hull loading on the yield of 5-HMF was investigated. As a result, a 5-HMF yield up to 51% was obtained using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) catalyzed with chromium (III) chloride at 130 °C for 2 h. The [Bmim]Cl/CrCl3·6H2O/HCl system was found to have high activity and selectivity for the dehydration of cellulose into 5-hydroxymethylfurfural. This work provides a low cost, environment-friendly and energy-efficient process to directly convert raw biomass into bio-fuels and chemicals.

Thermal degradation of DNA-treated cotton fabrics under different heating conditions

Our recent work has demonstrated that deoxyribose nucleic acid (DNA) can act as an effective flame retardant when applied to cotton fabrics as a thin coating. DNA acts as a Lewis acid and promotes the dehydration of cotton cellulose to form char, limiting the production of volatile species. Here, the effect of heating rates on thermal degradation behaviour has been studied in order to understand the thermo-oxidation behaviour under slow heating and fast (flash) pyrolysis. The low heating rate effect has been studied using thermogravimetry coupled with infrared spectroscopy and pyrolysis-combustion flow calorimetry, whereas high heating rate effect was obtained by performing thermogravimetry at 200–500°C/min and flash-pyrolysis tests coupled with infrared spectroscopy. The information obtained by the latter has been successfully employed in order to (i) better explain the results collected from combustion tests and (ii) demonstrate that the type of the gaseous species and their evolution, as well as the char formation, as a consequence of the fabric thermo-oxidation, are independent of the adopted heating rate.

Influence of drying method and precipitated salts on pyrolysis for nanocelluloses

The influence of bulk density and drying method on pyrolysis behavior was studied by focusing on the salt content within the nanocellulose (NC) materials. The thermogravimetric curves for NC materials were found to be almost identical between the different bulk densities via the various drying methods. It was therefore concluded that the bulk density and drying method of NC materials had little influence on pyrolysis behavior. By quantitating the remaining salt content within the sulfate-introduced cellulose nanocrystal materials, we discriminated between the sulfate groups bonded onto cellulose and precipitated sulfate from the solvent. The precipitated sulfate was found to accelerate the pyrolysis of NCs in common with the bonded sulfate groups, but in a different rate. These two types of sulfate within the NC materials should have the different catalytic ability on the dehydration of cellulose.

Common processes drive the thermochemical pretreatment of lignocellulosic biomass

Lignocellulosic biomass, a potentially important renewable organic source of energy and chemical feedstock, resists degradation to glucose in industrial hydrolysis processes and thus requires expensive thermochemical pretreatments. Understanding the mechanism of biomass breakdown during these pretreatments will lead to more efficient use of biomass. By combining multiple probes of structure, sensitive to different length scales, with molecular dynamics simulations, we reveal two fundamental processes responsible for the morphological changes in biomass during steam explosion pretreatment: cellulose dehydration and lignin-hemicellulose phase separation. We further show that the basic driving forces are the same in other leading thermochemical pretreatments, such as dilute acid pretreatment and ammonia fiber expansion.

Caseins and hydrophobins as novel green flame retardants for cotton fabrics

Despite the use of toxic and not environmentally-friendly chemicals, some proteins derived from animal or microbial sources have been investigated as novel green flame retardants for cotton fabrics. In particular, phosphorus- and sulphur-rich proteins (i.e. caseins and hydrophobins) have been homogeneously deposited on cotton fabrics starting from protein aqueous suspensions/solutions. These surface treatments, based on the use of species able to favour the dehydration of cellulose instead of its depolymerization, have strongly enhanced the production of a thermally stable carbonaceous structure ( char ), hence significantly enhancing the flame retardancy of the fabrics, as assessed by thermogravimetry and flammability tests.

Efficient conversion of glucose and cellulose to 5-hydroxymethylfurfural in DBU-based ionic liquids

Development of an efficient catalytic system for the dehydration of carbohydrates to produce 5-hydroxymethylfurfural (HMF), which is a platform molecule for biomass transformation, is a very attractive topic. In this work, three DBU-based ionic liquids (ILs) were prepared and used as the solvent for the conversion of carbohydrates into HMF. It was found that all these new ILs were excellent solvents for the dehydration of glucose, cellulose, fructose, sucrose, inulin, and cellobiose to form HMF using CrCl3·6H2O as the catalyst. The effects of temperature, reaction time, catalyst amount, and substrate/solvent weight ratio on the dehydration of glucose in CrCl3·6H2O/Bu-DBUCl were studied systematically. It was shown that the yield of HMF could reach 64% from glucose. In addition, the CrCl3·6H2O/Bu-DBUCl system could be easily separated from the product, and could be reused five times without considerably decreasing in activity and selectivity.

Effect of sulfuric acid concentration on the yield and properties of the bio-oils obtained from the auger and fast pyrolysis of Douglas Fir

The effect of sulfuric acid concentration on the yield and composition of bio-oils obtained from the auger and fluidized bed pyrolysis of Douglas Fir at 500°C have been investigated as a mean to enhance the production of fermentable sugars. The concentration of sulfuric acid in the feedstock was varied between 0 and 0.6mass%. The overall yield of pyrolysis products (gas, bio-oil and char) was comparable for both reactors. The presence of sulfuric acid decreases bio-oil yield and increases water and char yields. The yield of pyrolytic water produced in the auger reactor was higher due to the lower heating rates achieved which favor dehydration reactions. Maximum yields of levoglucosan and fermentable sugars were obtained at concentrations of sulfuric acid of 0.3mass% in the auger reactor and 0.05mass% in the fluidized bed reactor. Dehydration reactions responsible for water and cross linked sugars formation, as observed by the increase in the band at 1654cm−1 fitted in the FTIR, were enhanced as sulfuric acid concentration increases. The dehydration of cellulose in the presence of sulfuric acid also causes a reduction in the yield of acetic acid and acetol. The yields of some lignin derived compounds (lignin oligomers and guaiacols) also decreased substantially when sulfuric acid was added. Potential mechanisms responsible for the phenomena observed are discussed.

Research on the Mechanism of a Novel Si/P Flame Retardant

A novel Si/P flame retardant was prepared using tetraethyl orthosilicate (TEOS) and phosphoric acid (H3PO4). Cotton fabric treated with the flame retardant was characterized by cone calorimetry, thermogravimetric analysis (TGA), X-ray fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The peak heat release rate (pHRR) and total heat release (THR) of the fabric treated with TEOS/H3PO4 are lower than those of the fabric treated with TEOS or H3PO4 alone. The HRR and THR of the treated fabric decrease from 145.66 kW/m2 and 1.68 MJ/m2 to 70.76 kW/m2 and 0.67 MJ/m2, respectively. Total smoke production decreases from 0.080 to 0.014 m2/m2. TGA revealed that cellulose dehydration increases at low temperatures because of the addition of phosphoric acid and the production of charcoal. The generated charcoal is dense. The P and Si contents markedly increase, and exist in the charcoal in the form of P-O-C and Si-O bonds, respectively. On the basis of these results, we conclude that the main mechanism of TEOS/H3PO4 is that of a condensed-phase flame retardant. Good flame retardant synergism occurs between TEOS and H3PO4.

Density Functional Theory (DFT) Study on the Dehydration of Cellulose

Pyrolysis is a very important platform for the use of cellulose; however, the mechanism for the pyrolysis of cellulose is still not clear. A density functional theory (DFT) study was thus conducted to investigate the dehydration of cellulose using cellotriose as a model compound. The DFT study confirms that the location of hydroxyl groups has a significant influence on the dehydration of cellulose. The most active hydroxyl group is −O2H, followed by −O3H and −O6H. The pinacol rearrangement is a more likely mechanism for hydroxyl groups to be dehydrated. However, the barriers for dehydration are so high that dehydration reactions are difficult to occur. To obtain chemical products directly from the pyrolysis of cellulose, species with hydroxyl groups remaining might be targeted. Future studies are needed to explore the mechanism of cellulose pyrolysis, especially on the breaking of the glycosidic linkage and the opening of pyran rings.