Hydrolysis Of Cotton Research Articles

Гидролиз целлюлозы с использованием газовоздушных смесей хлористого водорода

Abstract. Microcrystalline cellulose (MCC) is a common product used in pharmaceutical, food and other industries. MCC is obtained by liquid-phase hydrolysis of cotton or wood bleached pulp with diluted 0.5–10.0 % mineral acids at a temperature of 100–140 °C. This process requires significant consumption of acid, water, and heat energy. Production of MCC in general is very expensive, which determines its high cost and the need to find alternative methods of cellulose hydrolysis. It is proposed to hydrolyze cellulose with concentrated hydrochloric acid produced by absorption of hydrogen chloride. We studied the processes of hydrogen chloride adsorption by bleached wood pulp with 8–18 % humidity. It is shown that adsorption of hydrogen chloride is determined by pulp humidity and is 3–5 % of the dry pulp mass. The sorption of hydrogen chloride leads to the formation of hydrochloric acid with a concentration of 25–40 % in the raw material moisture, significant heating of the mass and rapid hydrolysis of the amorphous cellulose fraction. It has been found that the use of pure hydrogen chloride for saturation causes strong darkening and humification of pulp. We recommend the use of hydrogen chloride gas-air mixtures to saturate the pulp, which will significantly reduce the sorption temperature and eliminate the strong darkening of the pulp during hydrolysis. The adsorption of hydrogen chloride by cellulose proceeds at an extremely high rate and is accompanied by the formation of a clearly visible sorption front at a temperature of 45–60 °C. Hydrolysis occurs for 15–30 min at 40–60 °C until the amorphous cellulose fraction is completely decomposed. A very small amount of monosaccharides is formed (4 % of dry pulp). The yield of MCC is high, more than 95 %. These circumstances are probably related to the recrystallization of a part of the amorphous fragments of cellulose macromolecules, which is a characteristic of hydrolysis with concentrated acids. The product obtained by cellulose hydrolysis is identical to MCC according to the data of IR spectroscopy, X-ray diffraction and viscometry. The article shows the high efficiency of cellulose hydrolysis with hydrogen chloride gas-air mixtures compared to traditional methods of MCC production.

Phase Behaviour of Cellulose Nanocrystal Dispersion in Aqueous Sulphuric Acid and Development of an Energy Efficient Separation Technique for the Acid-Cellulose Nanocrystal System

In this paper, the phase behaviour of a cellulose nanocrystal (CNCs) dispersion in sulphuric acid solutions was investigated, aimed at the development of an energy efficient separation method for this mixture. The system in consideration was a mixture of 30 wt% aqueous sulphuric acid (ρl = 1219 kg/m3) containing 12.6 mg/ml of cellulose nanocrystals (CNCs) (ρs = 1590 kg/m3, volume fraction of CNCs less than 1%). This volume filling mixture was obtained directly from a CNC extraction process, as obtained after the hydrolysis of cotton using 64 wt% sulphuric acid at ca. 45 ̊C for 45 minutes (this condition was required for the extraction of CNCs from cotton) followed by quenching the hydrolysis with water. The CNCs form the desired product and need to be separated from the acid that can then be recycled. Conventionally this separation has been difficult and requires a large input of energy. This work addresses this problem by investigating into the phase behaviour and physicochemical and hydrodynamic character of this mixture. This understanding led to the development of a very energy efficient separation mechanism for this mixture, which is 5 orders of magnitude more energy efficient than the most widely used centrifugation systems.

Ultrahigh intercalation pseudocapacitance of mesoporous orthorhombic niobium pentoxide from a novel cellulose nanocrystal template

A facile biotemplating method has been developed to prepare mesoporous orthorhombic nobium pentoxide (T-Nb2O5) films with ultrahigh lithium ion (Li+) intercalation pseudocapacitance. Nanorod-like cellulose nanocrystals (CNs) with 5–10 nm in width and 100–300 nm in length are produced by the hydrolysis of cotton, which can serve as a novel soft templating agent enabling the straightforward synthesis of mesoporous T-Nb2O5 films. By varying the niobic-to-template ratio, it is possible to tune the surface area and crystallite dimension of the Nb2O5 films. The obtained T-Nb2O5 films show typical capacitive-dominated behaviour in the sweep rate range of 1–20 mV s−1. It delivers an initial intercalation capacity of 644 C g−1 at a current density of 0.625 A g−1, corresponding to x = 1.83 for LixNb2O5, and can still keep relatively stable capacity of 560 C g−1 after 300 cycles. Moreover, its excellent high-rate capability (450 C g−1 at 12.5 A g−1) and wider temperature adaptability present here suggests the promising of T-Nb2O5 as high-energy pseudocapacitor electrode with superior intercalation capacitive behaviour.

Electron microscopic observation of cotton cellulose degradation by exo- and endo-type cellulases from Irpex lacteus.

The interaction of two highly purified cellulases, exo- and endo-type cellulases from Irpex lacteus, with pure cotton and amorphous cellulose was investigated by electron microscopy. The morphological observations indicated that exo- and endo-type cellulases are both strongly adsorbed on the internal microfibril of cotton fiber before enzymatic hydrolysis, and then initiate their action toward the internal cellulose microfibrils with retention of the original shape. The two cellulases, however, caused considerably different morphological changes in cotton cellulose, and each cellulase seems to degrade native cellulose with a distinct mode of action. In the hydrolysis of cotton with exo-type cellulase, deep transverse cracks were produced and they extended from the fiber surface to the lumen structure located inside the fibers. In contrast, it was found that there were no deep cracks on fibers treated with endo-type cellulase, but severe internal erosion and cavitation occurred along fibril or microfibril layers inside the fibers. Thus, the degradation of cotton by exo- and endo-type cellulases yielded quite different morphological patterns, while little difference was found for regenerated celluloses. The mode of enzymatic hydrolysis of cellulose shown by cellulases with different degrees of randomness (exo and endo types) appears to be markedly affected by the fine structure of cellulose fibers.

Production and cross-synergistic action of cellulolytic enzymes from certain fungal mutants grown on cotton and straw

Significant levels of cellulase and β-glucosidase, capable of saccharifying cotton fiber and wheat straw cellulose, were excreted by the selected mutantsAspergillus ustus M35 andTrichoderma harzianum M5 grown on these cellulosic materials. Cross-synergism was observed between the cellulolytic system of certain fungl upon hydrolysis of cotton. A maximum enhancement of 282% in the saccharification rate of cotton was obtained when this material was incubated withAlternaria alternata M7 andA. ustue M35. culture fluids mixed in certain proportions.

Effect of pretreatment on the hydrolysis of cellulose by Penicillium funiculosum cellulase and recovery of enzyme

Penicillium funiculosum produces a complete cellulase which brings about 97% hydrolysis of cotton and has high beta-glucosidase, xylanase, laminarinase, and lichenase activities. This article deals with the effect of different pretreatments on the hydrolysis of sugarcane bagasse by P. funiculosum enzymes and the recovery of enzyme from the insoluble residues. Enzymic saccharification of bagasse pretreated with hot 1N NaOH followed by neutralization with HCI and steam treated under pressure (7 kg/cm(2)) gave 63 and 59% saccharification, respectively, in 48 h. Hemicellulose is not lost in these pretreatments. With a 30% slurry of steam-treated bagasse, a semisolid mass containing 14% sugar was obtained. A 90% recovery of CMCase, beta-glucosidase, and filter paper activity from the hydrolysates was obtained under the following conditions: (1) maintaining the ratio of enzyme to substrate high by stepwise addition of substrate, (2) brief grinding of the residual substrate with glass powder, and (3) addition of 0.4% Tween-80 to the eluting buffer. The high recovery of cellulolytic enzymes indicates that the adsorption of these enzymes on cellulose is not irreversible.

The Temperature Dependence of the Rate of Crosslinking with Formaldehyde and of the Hydrolysis of Cotton Cellulose

The kinetics of the crosslinking of cotton fabrics in aqueous solution with formaldehyde using hydrochloric acid as catalyst, and the acid degradation (hydrolysis) of cotton were measured simultaneously at 67.4°C, 77.6°C, and 87.0°C. Some related kinetic measurements of these two reactions were also carried out with the pad-dry-cure process, catalyzed by MgCl2, at 140°C, 160°C, and 180°C. The apparent activation energies of crosslinking and hydrolysis were calculated. They are discussed with reference to the improvement in the dry crease-recovery angle/tensile strength relation at lower reaction temperatures. For the reaction in aqueous solution the rate of degradation of the accessible as well as the highly-ordered fractions of cellulose were determined. Finally, the apparent reaction enthalpy of the crosslinking reaction was estimated.

Urea-Phosphoric Acid Hydrolysis of Cotton Modified with N-Methylolated Ethylene Ureas

Native and mercerized cotton cellulose, modified with N-methylolated derivatives of ethylene urea, were examined before and after urea-phosphoric acid hydrolyses. Fine structural changes accompanying chemical reactions were evaluated by infrared absorption spectroscopy, x-ray diffraction, and electron microscopy. Final fabric properties and extent of restoration of original tensile properties after urea-phosphoric acid hydrolysis varied with the reagent applied and the lattice structure of the cotton control.

The Hydrolysis and Catalytic Oxidation of Cellulosic Materials. III. The Rates of Hydrolysis of Cotton Mercerized with and without Tension

The Hydrolysis and Catalytic Oxidation of Cellulosic Materials. III. The Rates of Hydrolysis of Cotton Mercerized with and without Tension