Acid-catalyzed Hydrolysis Of Cellulose Research Articles

Reversible Deacidification and Preventive Conservation of Paper-Based Cultural Relics by Mineralized Bacterial Cellulose.

Paper-based cultural relics experience irreversible aging and deterioration during long-term preservation. The most common process of paper degradation is the acid-catalyzed hydrolysis of cellulose. Nowadays, deacidification has been considered as a practical way to protect acidified literature; however, two important criteria of minimal intervention and reversibility should be considered. Inspired by the superior properties of bacterial cellulose (BC) and its structural similarity to paper, herein, the mineralized BC membranes are applied to deacidification and conservation of paper-based materials for the first time. Based on the enzyme-induced mineralization process, the homogeneous and high-loaded calcifications of hydroxyapatite (HAP) and calcium carbonate (CaCO3) nanoparticles onto the nanofibers of BC networks have been achieved, respectively. The size, morphology, structure of minerals, as well as the alkalinity and alkali reserve of BC membranes are well controlled by regulating enzyme concentration and mineralization time. Compared with HAP/CaCO3-immersed method, HAP/CaCO3-BC membranes show more efficient and sustained deacidification performance on paper. The weak alkalinity of mineralized BC membranes avoids the negative effect of alkali on paper, and the high alkali reserve implies a good sustained-release effect of alkali to neutralize the future generated acid. The multiscale nanochannels of the BC membrane provide ion exchange and acid/alkali neutralization channels between paper and the BC membrane, and the final pH of protected paper can be well stabilized in a certain range. Most importantly, this BC-deacidified method is reversible since the BC membrane can be removed without causing any damage to paper and the original structure and fiber morphology of paper are well preserved. In addition, the mineralized BC membrane provides excellent flame-retardant performance on paper thanks to its unique organic-inorganic composite structure. All of these advantages of the mineralized BC membrane indicate its potential use as an effective protection material for the reversible deacidification and preventive conservation of paper-based cultural relics.

Recyclable Cu Salt-Derived Brønsted Acids for Hydrolytic Hydrogenation of Cellulose on Ru Catalyst

Bronsted acid-catalyzed hydrolysis of cellulose, the most abundant source of biomass in nature, is the critical step for its depolymerization and subsequent conversion to sugar alcohols and other i...

Adsorption mediated tandem acid catalyzed cellulose hydrolysis by ortho-substituted benzoic acids

Carboxylic acid and phenol moiety containing carbon materials are proven to catalyze cellulose hydrolysis. Experiments utilizing benzoic acid and substituted derivatives as model catalysts revealed that vicinal oxygenated group containing catalysts showed significantly higher activities regardless of acidity. However, the increase in catalytic activity was not well understood. Using density functional theory, the mechanism of catalysis was elucidated. Calculated binding energy followed the experimental turnover number suggesting that the formation and the stability of the adduct complex is imperative to catalysis. In addition to this, protonated system effectively modeled the experimental activation energy implying that a hydronium participates in the reaction. These calculations indicated that during the life time of the adduct complex, a dissolved proton assists in the overall catalytic mechanism.

Formation of cellulose-carbene complex via depolymerization in ILs: Dependence of IL types on kinetics, conformation and dispersity

This study focused on the influence of anion type on the depolymerization and its effect on the molecular state, dynamics and dispersity of cellulose. GPC and the van Gurp-Palmen plot showed that molar mass was more significantly decreased by 1-butyl-3-methylimidazolium chloride ([C4C1Im][Cl]) comparing to 1-butyl-3-methylimidazolium acetate ([C4C1Im][OAc]). Acid-catalyzed hydrolysis of cellulose in IL was proved using base titration which was monitored by conductivity and pH value. On the contrary to the depolymerization case, [C4C1Im][OAc] solution needed more base to be neutralized than [C4C1Im][Cl] solution. The generated carbene was combined with reducing ends of cellulose, which was facilitated in low molar mass consisting of a large number of reducing ends. The formation of cellulose-carbene substitution caused steric hindrance of cellulose chain, thus resulting in increased segmental friction with high molecular density. The cellulose particle combined with carbene can be dispersed stably in aqueous media.

Integrated Electrocatalytic Processing of Levulinicacid and Formic Acid to Produce Biofuelintermediate Valeric Acid

With the world population rapidly increasing and major crude oil reserves diminishing, seeking renewable energy resources is becoming of critical importance, and thus has attracted enormous R&D attention worldwide. Abundant and renewable ligno-cellulosic biomass is expected to occupy a significant position in our future energy landscape, and one of the most important components derived from ligno-cellulosic biomass is highly polymerized cellulose (DP 7000–15 000), which can be employed as a sustainable source to produce levulinic acid (LA) through dilute acid-catalyzed hydrolysis processes. Levulinic acid can be further upgraded to a wide range of value-added chemicals and fuel additives, and has been identified as one of the top abundant, renewable building-block biomass compounds by the US-DOE. The hydrolysis of waste cellulose to levulinic acid is carried out in 0.1–0.5 M sulfuric acid aqueous solution; equal molar levulinic acid and formic acid(FA) (molFA : molLA = 1 : 1) can be cheaply produced at yields of 70% and 50%, respectively. Unfortunately, both the by-product formic acid and the residual sulfuric acid that remained in the hydrolysis downstream will bring some complexities to the subsequent transformation of levulinic acid to biodegradable chemicals or fuel additives during heterogeneous catalytic processes, such as the rapidly deactivation effect of formic acid on Ru/C for de-oxygenation of levulinic acid to gamma-valerolactone (gVL). Thus, novel processing routes and advanced catalysts have recently been explored to remove or utilize the by-product formic acid Herein, we report integrated electrocatalytic processing of simulated acid-catalyzed cellulose hydrolysis downstream (levulinic acid + formic acid) to the biofuel intermediate valeric acid (VA). This green electrobiorefining process does not require complex steps to separate levulinic acid and formic acid (FA) from H2SO4; instead it couples electrocatalytic hydrogenation (ECH) of levulinic acid in a single electrocatalytic flow cell reactor and electrocatalytic oxidation of formic acid in a proton exchange membrane-direct formic acid fuel cell (DFAFC). The presence of formic acid has shown no negative effect on the ECH of levulinic acid and a high valeric acid selectivity of >90% can be achieved on a non-precious Pb electrode while the Faradaic efficiency remains >47% during 8 hours of reaction in the single electrocatalytic flow cell reactor. This stream is fed directly to the DFAFC with a Pd/C anode catalyst to self-sustainably remove formic acid where 47% conversion of formic acid can be reached in 6 hours. However, electro-oxidation of formic acid over Pd/C appears to be reversibly inhibited by the product valeric acid produced during ECH of levulinic acid. The electro-oxidation of FA + C2–C5 alkyl carboxylic acid in the half cell study shows that such an inhibition effect could have originated from the –COOH adsorption on the Pd surface. Higher carboxylic acid concentration and longer carbon chain lead to more serious loss of the electrocatalytic surface area (ECSA) of Pd/C. Figure 1

Kinetics of Formic Acid-catalyzed Cellulose Hydrolysis

Hydrolysis is a reaction to produce sugars from lignocellulosic raw materials for biochemical production. The present study elucidates the hydrolysis of cellulose and formation of glucose decomposition products catalyzed by 5% to 20% (w/w) formic acid at 180 to 220 °C with an initial cellulose concentration of 10 to 100 g/L. Microcrystalline cellulose was used as a model compound. The experimental findings indicated that cellulose hydrolysis follows first-order kinetics in formic acid. A side reaction from cellulose to non-glucose products was required to explain the experimental results. A kinetic model was developed for the hydrolysis of microcrystalline cellulose in formic acid, based on a rate constant expression in accordance with the specific acid catalysis. The model showed good agreement with the experimental data. This study demonstrates how kinetic parameters can be fitted in a case-specific manner for the hydrolysis part of the kinetic model, while the well-established glucose decomposition model is utilized directly from literature.

Integrated electrocatalytic processing of levulinic acid and formic acid to produce biofuel intermediate valeric acid

Herein, we report integrated electrocatalytic processing of simulated acid-catalyzed cellulose hydrolysis downstream (levulinic acid + formic acid) to the biofuel intermediate valeric acid (VA). This green electro-biorefining process does not require complex steps to separate levulinic acid and formic acid (FA) from H2SO4; instead it couples electrocatalytic hydrogenation (ECH) of levulinic acid (LA) in a single electrocatalytic flow cell reactor and electrocatalytic oxidation of formic acid in a proton exchange membrane-direct formic acid fuel cell (DFAFC). The presence of FA has shown no negative effect on the ECH of LA and a high VA selectivity of >90% can be achieved on a non-precious Pb electrode while the Faradaic efficiency remains >47% during 8 hours of reaction in the single electrocatalytic flow cell reactor. This stream is fed directly to the DFAFC with a Pd/C anode catalyst to self-sustainably remove FA where 47% conversion of FA can be reached in 6 hours. However, electro-oxidation of FA over Pd/C appears to be reversibly inhibited by the product VA produced during ECH of LA. The electro-oxidation of FA + C2–C5 alkyl carboxylic acid in the half cell study shows that such an inhibition effect could have originated from the –COOH adsorption on the Pd surface. Higher carboxylic acid concentration and longer carbon chain lead to more serious loss of the electrocatalytic surface area (ECSA) of Pd/C.

Heterogeneous Acid-Catalyzed Hydrolysis of Cellulose

With the world’s focus on reducing our dependency on fossil fuel resources, one of the challenges will be the development of efficient catalysts for selective transformation of cellulosic biomass. Hydrolysis of cellulose to glucose is a key technology for effective use of lignocellulose because glucose can be efficiently converted into various chemicals, biofuels, foods, and medicines. Thus far, substantial efforts have been devoted to the degradation of cellulose but these processes have significant drawbacks. Some of these problems can potentially be overcome with the application of solid acid catalysts. In this paper, recent studies on heterogeneous acid-catalyzed hydrolysis of cellulose are summarized.

Kinetic study of acid-catalyzed cellulose hydrolysis in 1-butyl-3-methylimidazolium chloride

In this paper, the kinetics of acid-catalyzed cellulose hydrolysis in ionic liquids (ILs) was investigated by using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as the model IL. General kinetic equations for the formation of glucose as well as cellooligomers were constructed at a molecular level, assuming that cellulose is fully dissolved to form a homogenous solution and that the scission of the glycosidic bond occurs randomly within the cellulose chain. Experimental data were well fitted according to these equations. Variations of kinetic parameters in the presence of different water content indicated that water behaved also as a base to decrease the acidity of the reaction medium. More importantly, it offered a profile of the evolution of cellooligomers. These results provided insights into the detailed mechanisms of cellulose hydrolysis in a non-aqueous, homogenous environment and should be valuable for developing strategies to depolymerize lignocellulosic biomass.

Distinct Effect of Formic and Sulfuric Acids on Cellulose Hydrolysis at High Temperature

Acid-catalyzed hydrolysis of cellulose is a starting point for producing glucose-based fuels and chemicals. According to the mechanism of cellulose hydrolysis, hydrogen ions are responsible for the reaction. This study aims to elucidate the phenomena in cellulose hydrolysis at 180–220 °C using 5–20% (w/w) formic acid or 0.09–0.50% (w/w) sulfuric acid as catalyst. A significant difference between the reaction rates in formic and sulfuric acids was found despite the same hydrogen ion concentration. The findings could not be explained unambiguously through changes in the crystallinity of cellulose. It is suggested that, in addition to hydrogen ions, cellulose hydrolysis is affected by other species found in reaction media. A kinetic model based on specific acid catalysis combined with the effect of bisulfate ions was developed for cellulose hydrolysis in sulfuric acid.

Solid Acid‐Catalyzed Cellulose Hydrolysis Monitored by In Situ ATR‐IR Spectroscopy

The solid acid-catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR-IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and other compounds, were measured in water under ambient and elevated temperatures. A combination of spectroscopic and HPLC analysis revealed that the cellulose hydrolysis proceeds first through the disruption of the glycosidic linkages of cellulose to form smaller cellulose molecules, which are readily observed by their distinctive C-O vibrational stretches. The continued disruption of the linkages in these oligomers eventually results in the formation and accumulation of monomeric glucose. The solid-acid catalyst accelerated the isomerization of glucose to fructose, which then rapidly reacted under hydrothermal conditions to form degradation products, which included HMF, LA, formic acid, and acetic acid. The formation of these species could be suppressed by decreasing the residence time of glucose in the reactor, reaction temperature, and contact with the metal reactor. The hydrolysis of regenerated cellulose proceeded faster and under milder conditions than microcrystalline cellulose, which resulted in increased glucose yield and selectivity.

Efficient acid-catalyzed hydrolysis of cellulose in organic electrolyte solutions

A novel method for cellulose hydrolysis catalyzed by mineral acids have been developed in organic electrolyte solutions at 70 °C under atmosphere pressure without pretreatment. Several reaction parameters including reaction time, temperature, catalyst loading and the ratio of ionic liquids to organic solvents have been evaluated and optimized. Under optimal conditions, the maximum total reducing sugars (TRS) yield in 68.8% and glucose yield in 39.2% were obtained in 1.0 g NMP/3.0 g [Bmim]Cl system at 70 °C. Due to the low temperature of cellulose hydrolysis, this method shows a promising potential as an energy-efficient and cost-effective approach for the biorefinery of lignocellulosic biomass.

Acid-catalyzed hydrolysis of cellulose and cellulosic waste using a microwave reactor system

A microwave reactor system was investigated as a potential technique to maximize sugar yield for the hydrolysis of municipal solid waste for ethanol production. Specifically, dilute acid hydrolysis of α-cellulose and waste cellulosic biomass (grass clippings) with phosphoric acid was undertaken within the microwave reactor system. The experimental data and reaction kinetic analysis indicate that the use of a microwave reactor system can successfully facilitate dilute acid hydrolysis of cellulose and waste cellulosic biomass, producing high yields of total sugars in short reaction times. The maximum yield of reducing sugars was obtained at 7.5% (w/v) phosphoric acid and 160 °C, corresponding to 60% of the theoretical total sugars, with a reaction time of 5 min. When using a very low acid concentration (0.4% w/v) for the hydrolysis in the microwave reactor, it was found that 10 g of total sugars/100 g dry mass was produced, which is significant considering the low acid concentration. When hydrolyzing grass clippings using the microwave reactor, the optimum conditions were an acid concentration of 2.5% (w/v), 175 °C with a 15 min reaction time, giving 18 g/100 g dry mass of total sugars, with xylose being the sugar with the highest yield. It was observed that pentose sugars were more easily formed but also more easily degraded, these being significantly affected by increases in acid concentration and temperature. Kinetic modeling of the data indicated that the use of microwave heating may account for an increase in reaction rate constant, k1, found in this study in comparison with conventional systems described in the literature.

Solid acid and microwave-assisted hydrolysis of cellulose in ionic liquid

Solid acid-catalyzed hydrolysis of cellulose in ionic liquid was greatly promoted by microwave heating. H-form zeolites with a lower Si/Al molar ratio and a larger surface area showed a relatively higher catalytic activity. These solid catalysts exhibited better performance than the sulfated ion-exchanging resin NKC-9. Compared with conventional oil bath heating mode, microwave irradiation at an appropriate power significantly reduced the reaction time and increased the yields of reducing sugars. A typical hydrolysis reaction with Avicel cellulose produced glucose in around 37% yield within 8 min.

The Chemistry of Paper Preservation. Part 5. Permanent Paper

The acid-catalyzed hydrolysis of cellulose accounts for the deterioration of paper in library books and other written records. To combat this threat to our written heritage, new permanent papers have been developed that are relatively chemically stable and undergo a very slow rate of deterioration. Many of these new papers are manufactured from mechanical pulps that contain large amounts of lignin, and are stable when a calcium carbonate buffer is present. Based on the performance involving accelerated aging of the papers, the inclusion of lignin has been accepted in the standards for permanent paper by Canada and Germany, providing that a calcium carbonate buffer is present. Other countries are still reluctant to make the change in standards to include lignin. Research needs to be done to define optical properties and their requirements for the standards. The applications of the chemistry of paper preservation to teaching are also discussed.

Kinetic Study on the Acid-Catalyzed Hydrolysis of Cellulose to Levulinic Acid

A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is reported in this paper. The kinetic experiments were performed in a temperature window of 150−200 °C, sulfuric acid concentrations between 0.05 and 1 M, and initial cellulose intakes between 1.7 and 14 wt %. The highest yield of levulinic was 60 mol %, obtained at a temperature of 150 °C, an initial cellulose intake of 1.7 wt %, and a sulfuric acid concentration of 1 M. A full kinetic model covering a broad range of reaction conditions was developed using the power-law approach. Agreement between the experimental data and the kinetic model is good. The kinetic expressions were used to gain insights into the optimum process conditions for the conversion of cellulose to levulinic acid in continuous-reactor configu...

Cellulose-based chromatography for cellooligosaccharide production.

The potential of using cellulose stationary phases for the chromatographic fractionation of cellooligosaccharide preparations has been explored. The impetus for the work is the current interest in using cellooligosaccharides as functional nondigestible oligosaccharides in foods. The conceptual studies illustrate the potential of using ethanol-water mobile phases in conjunction with cellulose stationary phases for cellooligosaccharide fractionation. Cellooligosaccharide solubility in ethanol-water mixtures and their elution order from cellulose-based columns using ethanol-water mobile phases were shown to be in line with their degree of polymerization (DP), with the higher DP cellooligosaccharides being less soluble and having longer retention times. The retention volume for all COS increased with increased temperature. Both microcrystalline and fibrous cellulose preparations were shown to work as chromatographic stationary phases. The application experiments demonstrate the potential of using cellulose stationary phases for the cleanup and fractionation of cellooligosaccharide mixtures generated via acid-catalyzed hydrolysis of cellulose.

Comments on "Productive and Parasitic Pathways in Dilute Acid-Catalyzed Hydrolysis of Cellulose" and "Kinetics of Dilute Acid Hydrolysis of Cellulose Originating from Municipal Solid Wastes"

Comments on "Productive and Parasitic Pathways in Dilute Acid-Catalyzed Hydrolysis of Cellulose" and "Kinetics of Dilute Acid Hydrolysis of Cellulose Originating from Municipal Solid Wastes"

Productive and parasitic pathways in dilute acid-catalyzed hydrolysis of cellulose

Cellulose hydrolysis experiments were conducted in a percolating reactor at 34.5 MPa. A glucose yield of 71% of the theorical maximum was obtained at 215°C with 0.05% by weigth of sulfuric acid in percolating solution. The classical model of glucose formation from cellulose followed by secondary sugar degradation did not describe the reaction chemistry under these conditions. A parasitic pathway which leads to the formation of nonhydrolysable oligomer was discovered in the absence of acid. In the presence of acid, kinetic modeling of the measured, temperature-dependent rates of glucose evolution indictaes that an acid-catalized parasitic pathway operates in competition with the glucose production pathway. No chemical change were detecte in the solid phase during the course of reaction

COUNTER-CURRENT REACTOR IN ACID CATALYZED CELLULOSE HYDROLYSISdagger;

A mathematical model was developed for a counter-current reactor to investigate its performance in acid catalyzed cellulose hydrolysis. The results indicated that use of this reactor would be advantageous particularly in obtaining high product yield. The predicted yield of above 70% under normal reaction conditions was substantially higher than those achievable from plug flow (28%) or percolation reactor (54percnt;).