Cellulose preparations, pretreatments

Some part of the cellulose fraction is redirected to make cellulose derivatives, such as cellulose acetate, methyl and ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. These derivatives find multiple applications, for instance, as additives in current products (e.g., paints, lacquers) of chemical industry. Typically, the preparation of cellulose derivatives takes place as a two-phase reaction cellulose is pretreated, for example, with alkali, and a reagent is added to get the substitution. Usually no catalyst is needed [5]. 

The acetylation reaction of cellulose is often prepared by forming a solution in a mixture of acetic anhydride and sulfuric acid. This results in the formation of a triacetate. When a lower degree of esterification is desired, the triacetate is partially hydrolyzed. A two-step procedure is needed, because it is not possible to control the degree of esterification in the reaction with acetic anhydride and sulfuric acid. In a typical process, dry cellulose is pretreated with 300 parts acetic anhydride, one part sulfuric acid, and 400 parts methylene chloride. The reaction mixture is agitated while the temperature is maintained at 25-35 for 5-8 eight hours. By the end of that period all the cellulose... 

Ethyl Cellulose. Pretreated cellulose (100 g) was charged into a two liter stirrer pipe bomb, combined with NaOH (80 g, 2.0 M), ethyl chloride (250 g, 4.0 M) and 300 mL toluene and the mixture was heated to 130 for two hours. After cooling to 5 , the bomb was opened, excess ethyl chloride was allowed to evaporate and the residue poured into two liters of water. The toluene was steam distilled from the suspension and the ethyl cellulose was recovered by filtration. Approximately 46 g of ethyl cellulose, D.S. = 1.56, was obtained. A sample of ethyl cellulose prepared under identical conditions except omitting the catalyst was obtained in reduced yield (21 g) due to the higher water... 

A more radical approach to pretreatment reverses the conventional reactive dyeing concept by preparing a reactive cotton cellulose capable of reacting covalently with suitable dyes containing, for example, aliphatic amino groups. In an initial attempt, cotton was... 

Very similar results to those described in Fig. 3-6 were obtained when sodium cholate solubilized hepatic microsomes from DBA-treated female little skates were subjected to chromatography on DEAE-cellulose as described above (data not shown). Also not shown are the results obtained with hepatic microsomes from untreated male and female little skates. With untreated animals, 80-90% of the cytochrome P-450 eluted from the DEAE-cellulose column only at higher ionic strength (i.e., with the KC1 gradient). However, in all preparations studied, an appreciable amount of cytochrome P-450 (10-20%), having its absorption maximum in the carbon monoxide-ligated and reduced state at 450 nm, was eluted from the column with buffer II, as was observed with cytochrome P-448 of hepatic microsomes from DBA-treated skates. The further purification of the various forms of cytochrome P-450 from control and DBA-pretreated little skate livers is currently in progress in our laboratory. 

The effective pretreatments for enzymatic hydrolysis of cellulose in hardwoods and agricultural residues have been developed over the past 90 years and new or improved ones are still being developed. The initial impetus for pretreatment research was the expansion of a feed base for ruminants (i.e., cattle and sheep). The concentration of pretreatment research on animal feed preparation placed an additional burden on researchers, because the product must be not only fully convertible to animal live-weight, but also nontoxic and palatable. Early feeding trials of pretreated fine sawdust to cattle produced very dismal results (55). This may be the reason, besides the... 

Substrate and Pretreatment. Sweet corn (hybrid Lingodor) of W.H. Perron Laval, Quebec was grown in well prepared soil in a plot of 3 x 2 meters. Corn stalks were ground to 20 mesh to be used as a substrate. It was pretreated with 1.5% sodium hydroxide (NaOH) wt/vol with substraterwater ratio of 1 10 at 121 C for 60 minutes. The substrate was not washed after the pretreatment, and all the solubilized polymers (hemicelluloses and lignin) were retained along with the insoluble polymer (cellulose) in the fermentation medium. The composition of corn stalk is presented in Table 1. 

In the late fifties Regie Nationale des Usines Renault (86) described the preparation of allyl ethers through reaction of alkali cellulose with allyl halides in carbon tetrachloride or benzene. With products having degrees of substitution between 0.2 to 0.8 graft copolymerization could be achieved when activated by pretreatment with air or ozone or by initiation with peroxide catalysts with styrene, acrylonitrile, vinyl acetate, or acrylates. 

A dispersion of graphite in ceresin wax has been suggested as a way to prepare an electrode suitable for use in nonaqueous solvents. The hot paste is tamped into a Teflon tube and allowed to solidify. No pretreatment is necessary, and the surface can be renewed by wiping with cellulose tissue. 

A mathematical model has also been proposed for evaluating cellulase preparations. Sattler et al.209 describe a relationship between hydrolysis extent, reaction time, and enzyme concentration. This procedure permits the effectiveness of different enzymes and of different pretreatment methods to be ranked. This method examines cellulose hydrolysis data collected from hyperbolic functions of substrate concentration versus cellulase enzyme concentration at various timed incubations. The model is based on a double reciprocal plot of the relationship... 

Chemical modification reactions continue to play a dominant role in improving the overall utilization of lignocellulosic materials [1,2]. The nature of modification may vary from mild pretreatment of wood with alkali or sulfite as used in the production of mechanical pulp fibers [3] to a variety of etherification, esterification, or copolymerization processes applied in the preparation of wood- [4], cellulose- [5] or lignin- [6] based materials. Since the modification of wood polymers is generally conducted in a heterogeneous system, the apparent reactivity would be influenced by both the chemical and the physical nature of the substrate as well as of the reactant molecules involved. 

Presented are the examinations of the multifimctional mineral-earbon and zeolite-carbon sorbents prepared from kaolinite with an admixture of carbonaceous materials industrial waste deposits, municipal sewage sludge and cellulose. The mixture of raw materials was thermally and hydrothermally pretreated in order to facilitate their specific structure. The parameters of capillary structure (micro and mesopores) were determined. For examinations of porous structure the mereury porosimetry method was used. In order to evaluate the solid phase transformation during the each step of sorbent preparation the SEM observation with quantitative X-ray mieroanalysis were made. 

The adsorbents have been prepared fi-om the halloysite (H) - mineral fi-om kaolinite group with an admixture of carbonaceous materials refinery waste deposits (RSI), sediment communal sewage (CSew) and cellulose (Ce), and the fiaction of these mixtures were within 30 - 70 wt.%. The mbcture of raw material was thermally (carbonaceous materials carbonization, 973 K) and hydrothermally (crystallization of the amorphous metahalloysite in alkaline solution to zeolitic structure of NaA type, 373 K) pretreated in order to cilitate their specific structure [1,2]. 

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