Cellulose carbonates, preparation

Cellulose esters of aromatic acids, aUphatic acids containing more than four carbon atoms and aUphatic diacids are difficult and expensive to prepare because of the poor reactivity of the corresponding anhydrides with cellulose Httle commercial interest has been shown in these esters. Of notable exception, however, is the recent interest in the mixed esters of cellulose succinates, prepared by the sodium acetate catalyzed reaction of cellulose with succinic anhydride. The additional expense incurred in manufacturing succinate esters is compensated by the improved film properties observed in waterborne coatings (5). 

The subject of Figs. 4-6 involves another difficult topic the examination of carbonaceous materials. In order to obtain carbons prepared under controlled conditions, the pyrolysis of cellulose was studied. Fig. 4 shows just three of many spectra of pyrolysis sequences. The numerous changes in the spectra, e.g., the decline of aliphatic C-H stretching absorptions just... 

The boron-containing cellulose esters prepared to date have been readily hydrolyzable, evoi in air (37). The use of lithium derivatives of barenes makes it possible to produce boron-containing derivatives of cellulose in which the boron atoms are stably bount to the carbon atoms of the repeating unit of the macromolecule. 

Katoh et al. [145] showed that H2S, methanethiol, and dimethylsulfide could be removed simultaneously from gaseous streams at room temperature over wet activated carbon fibers, while Dalai et al. [142] reported on the oxidation of methanethiol over an activated carbon. More recently, an activated carbon prepared from a cellulosic precursor by CO2 activation was found to exhibit outstanding performance in the oxidation of H2S (1000 ppm) in a hydrogen stream at 423 K namely, 100% conversion for more than 10 hours, and 100% selectivity to sulfur [146]. The selectivity aspects in the oxidation of H2S to sulfur were addressed in a paper by Bashkova et al. [147]. These authors reported... 

This chapter details the technical procedures used to prepare and analyze lake sediment samples for cellulose carbon and oxygen isotope composition, considers important factors in the interpretation of cellulose isotope data, briefly highlights key results from recent applications, and outlines future research needs and directions. 

Methods for lake sediment sample preparation for cellulose carbon and oxygen isotope analyses have been developed at the University ofWaterloo - Environmental Isotope Laboratory (UW-EIL), (Heemskerk Diebolt, 1994 Edwards et al, 1997 Elgood et al., 1997). 

Figure 3. Flow diagram illustrating steps involved in preparing lake sediment for cellulose carbon and oxygen...

Calcium carbonate, prepared. See. Whiting Calcium carboxymethyl cellulose CAS 9050-04-8... 

The third, probably major commercial process used today, forms a material that is known as Viscose rayon. The regenerated cellulose is prepared and sold as a fiber as well as a film, known as cellophane. The viscose, or more properly referred to as the xanthate process, consists of forming cellulose xanthate by reacting alkali cellulose with carbon disulfide ... 

Figure 9.5. Density of cellulose aerogels prepared by Innerlohinger et al. [19] using NMMO as a solvent and supercritical drying with carbon dioxide (redrawn on the basis of their data using different units).

The coupling of 6-AP acid on CICMC, cellulose carbonate and BIOZAN R led to the preparation of macromolecular semisynthetic penicillins. 

M. Fleischer, H. Blattmann, R. Mulhaupt, Glycerol-, pentaerythritol- and trimethylol-propane-based polyurethanes and their cellulose carbonate composites prepared via the non-isocyanate route with catalytic carbon dioxide fixation. Green Chem. 15 (2013) 934-942. 

Wei W, Qin G, Hu H, You L, Chen G (2007) Preparation of supported carbon molecular sieve membrane fiom novolac phenol-formaldehyde resin. J Membr Sci 303 (1-2) 80-85 Lie JA, Hagg MB (2005) Carbon membranes from cellulose and metal loaded cellulose. Carbon 43 (12) 2600-2607... 

CH2CI2. A colourless liquid with a chloroform-like odour b.p. 4I°C. Prepared by heating chloroform with zinc, alcohol and hydrochloric acid manufactured by the direct chlorination of methane. Decomposed by water at 200°C to give methanoic and hydrochloric acids. Largely used as a solvent for polar and non-polar substances, particularly for paint removal (30%), dissolving cellulose acetate and degreasing (10%). It is more stable than carbon tetrachloride or chloroform especially towards moisture or alkali. It is somewhat toxic. U.S. production 1981 280000 tonnes. 

Several cellulose esters (qv) are prepared commercially. Cellulose xanthate [9032-37-5] is made by reaction of cellulose swollen in 8.5—12% sodium hydroxide solution (alkaU cellulose [9081-58-7J) with carbon disulfide and is soluble in the alkaline solution in which it is made. When such a solution, termed viscose, is introduced into an acid bath, the cellulose xanthate decomposes to regenerate cellulose as rayon fibers or cellophane sheets (see Fibers, REGENERATED CELLULOSICS). 

Cellulose esters are commonly derived from natural cellulose by reaction with organic acids, anhydrides, or acid chlorides. Cellulose esters of almost any organic acid can be prepared, but because of practical limitations esters of acids containing more than four carbon atoms have not achieved commercial significance. 

In an integrated continuous process, cellulose reacts with acetic anhydride prepared from the carbonylation of methyl acetate with carbon monoxide. The acetic acid Hberated reacts further with methanol to give methyl acetate, which is then carbonylated to give additional acetic anhydride (100,101). 

Diaziridines also show slow nitrogen inversion, and carbon-substituted compounds can be resolved into enantiomers, which typically racemize slowly at room temperature (when Af-substituted with alkyl and/or hydrogen). For example, l-methyl-3-benzyl-3-methyl-diaziridine in tetrachloroethylene showed a half-life at 70 °C of 431 min (69AG(E)212). Preparative resolution has been done both by classical methods, using chiral partners in salts (77DOK(232)108l), and by chromatography on triacetyl cellulose (Section 5.08.2.3.1). 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Graded Adsorbents and Solvents. Materials used in columns for adsorption chromatography are grouped in Table 12 in an approximate order of effectiveness. Other adsorbents sometimes used include barium carbonate, calcium sulfate, calcium phosphate, charcoal (usually mixed with Kieselguhr or other form of diatomaceous earth, for example, the filter aid Celite) and cellulose. The alumina can be prepared in several grades of activity (see below). 

Marino, B.D. and DeNiro, M.J. 1987 Isotopic analysis of archaeobotanicals to reconstruct past climates Effects of activities associated with food preparation on carbon, hydrogen and oxygen isotope ratios of plant cellulose. Journal of Archaeological Science 14 537-548. 

Fig 1. Electron micrograph of a platinum/carbon replica prepared by the fast-freeze, deep-etch, rotary-shadow replica technique printed in reverse contrast. Cell walls of onion parenchyma have an elaborate structure with many thin fibres bridging between thicker cellulosic microfibrils. Scale bar represents 200nm. 

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