summaryThree strains of Trichodermu-T. reesei C30. T. reesei QM9414. and Trichodernia species ES8-were used to study the enzymatic hydrolysis of pretreated wood substrates. Each of the culture filtrates was incubated with a variety of commercially prepared cellulose substrates and pretreated wood substrates. Solka floc was the most easily degraded commercial cellulose. The enzyme accessibility of steam-exploded samples which had been alkali extracted and then stored wet decreased with the duration of the steam treatment. Air drying reduced the extent of hydrolysis of all the samples but had a greater effect on the samples which had previously shoun the greatest hydrolysis. Mild pulping using 2% chlorite increased the enzymatic hydrolysis of all the samples. Steam explosion was shown to be an excellent pretreatment method for aspen wood and was much superior to dilute nitric acid pretreatment. The results indicate that the distribution of the lignin as well as the surface area of the cellulosic substrate are important features in enzymatic hydrolysis.
synopsisA bleached sulfite pulp (85.0% a-cellulose) was dissolved in dimethylformamide containing anhydrous chloral and pyridine as catalyst. The clear cellulose solution was then reacted with acetic anhydride under various conditions. The reaction products contained both acetyl groups and chlorine in amounts varying from 20% to 38%. Curves of reaction rates with respect to chlorine and acetyl groups under various conditions of temperature and reactant ratios were similar in appearance, and all the products contained approximately 2 moles of acetyl groups per mole of chloral. Yields varied from 180% after treatment at room temperature (25OC) for 1 hr to 250% after 4 hr. The products could be hydrolyzed in acid with some difficulty but very easily in dilute alkali.Films cast from acetone solutions had higher permittivity and lower a.c. conductivity than similar films made from cellulose diacetate.The products had low flammability and hygroscopicity. INTRODUCTIONIt was recently reported that cellulose could be dissolved in dimethyl sulfoxide, dimethylformamide (DRIF) , dimethylacetamide, and N-methyl-2-pyrrolidone in the presence of 5-10 moles anhydrous chloral per glucose residue.' These solutions were found to be miscible with synthetic high polymers. Tepteleva2 reported on the reaction of free hydroxyl groups in cellulose acetate with chloral in methylene chloride and in chloroform. I n DMF, little reaction was found to take place. In previous work,3 modified cellulose triacetates were prepared by reacting either secondary cellulose acetate or cellulose with chloral in methl lene chloride, benzene, or acetic acid followed by acetylation of the reaction product in the same reaction medium. Products with interesting properties were obtained containing up to 17% chlorine.I n the present work, cellulose was first dissolved in DMF containing chloral and pyridine and reacted with a mixture of acetic anhydride and pyridine. Reaction rates were studied and the products were characterized as to their acetyl and chlorine contents, elementary composition, and degree of polymerization (D.P.). The anhydrous chloral (bp 97-98"C), acetic anhydride, methylene chlolose was used. dried, and fluffed in a small hammer mill. 2773vacuum a t 60°C. could also be used as a medium for the reactions described in this work.ride, acetic acid, and pyridine used were reagent-grade chemicals. AnalysesChlorine analyses were carried out by the microcombustion method described by White.4Acetyl groups were determined by a modification of the semimicromethod described by Lin and S c h~e r c h .~ A sample (20-30 mg) was weighed into a 25-ml flask. Then, 3 ml of 7Oy0 2,2,2-trifluoroethanol solution containing 0.195 meq/ml sodium hydroxide was added to the sample, and the flask was heated loosely stoppered for 10 min at 60°C. Pyridine, 3 ml, was then added, and the solution was saponified for 3 hr a t 60°C. The excess alkali was back-titrated to a phenolphthalein endpoint with 0.05 N HCI. Blanks were run with every batch of samples.The D.P. of the ori...
synopsisCellulose derivatives soluble in water and in dilute alkali were prepared by dissolving a bleached sulfite pulp in solutions of nitrogen dioxide in dimethylformamide (DMF) and heating at 70-90°C for 1-3 hr. No cellulose oxidation was detected. Nitrite esters and apparently also, nitrate esters, were formed with degrees of substitution (DS) ranging from 0.18 to 0.55 and with nitrogen contenb ranging from 1.47 to 4.320J0. Solution viscosities in water increased with increasing nitrogen content. The degree of polymerization (DP) decreased rapidly in the initial stages of the reaction followed by a slow, gradual decrease with increasing reaction times. 1669
SynopsisWater-soluble films of cellulose nitrate-nitrite were prepared by dissolving bleached sulfite pulp in a solution of nitrogen dioxide in dimethylformamide (DMF) at room temperature and heating the solution at 70°C for about 3 hr. Their water sorption, fine structure, and electrical properties were measured and compared with those of three other films-ne water soluble (poly(viny1 alcohol)) and two water insoluble (cellophane and a film prepared from a cellulose solution in the nitrogen dioxideDMF mixture and cast immediately after the cellulose had dissolved a t room temperature). A comparison between the properties of water-soluble films and the poly(viny1 alcohol) film showed that the former had higher crystaIIinity, lower moisture absorption in the 0-80% relative humidity region, lower permittivity and a.c. conductance, and higher d.c. resistance. The DMF-cast water-insoluble film adsorbed less moisture than the cellophane film.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.