Cellulose process

Many cellulose fibers, including both natural and manufactured cellulose fibers, can be made into carbon fibers by high temperature treatment. However, carbon fibers made from natural cellulose fibers, such as cotton and ramie, often have high defect contents, which limit the strength of the fibers. Currently, rayon, a manufactured cellulose fiber, is the most used cellulose-based carbon precursor. 

The formation of rayon fibers has been discussed in Chapter 10. Rayon fibers have a large number of hydroxyl groups and absorb water molecules easily. Therefore, before the carbonization process, rayon fibers are first heat-treated between 25 and 150°C to carry out the physical desorption of water. The conversion of dried rayon fibers into carbon fibers typically involves a stabilization process between 300 and 400°C in air and a carbonization process up to 1500 C in inert atmosphere. Graphite fibers can be obtained by increasing the temperature up to 3000°C in inert atmosphere. 

Carbon fibers also can be produced by the pyrolytic deposition of hydrocarbon gases. Many hydrocarbon gases, such as methane, naphthalene, and benzene, have been used to produce carbon fibers with deposition temperatures of 1000-1200°C. Dining the pyrolysis process, thin tubes of carbon are first formed on ultra-fine particles. The tubes then grow by a surface diffusion mechanism, and the subsequent high temperature treatment with a temperature up to 2500°C results in the formation of carbon fibers with diameters ranging from 10 run to mote than 100 /im. Carbon fibers produced from hydrocarbon gases often have central hollow cores. 

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The two pinenes are obtained from Crude Sulfate Turpentine (CST), which is a side product of the sulfate cellulose process from pine trees. Limonene is present in orange and lemon peels [which provide different enantiomers/ )], and is a cheap by-product of the citrus industry. 

The most promising second-generation biofuel technology - ligno-cellulosic processing - is already well advanced. In Europe, for example, three pilot plants have been established, in Sweden, Spain and Denmark. Other technologies to convert biomass into liquid biofuels (BtL) include Fischer-Tropsch biodiesel and bio-DME (dimethyl ether). Demonstration plants are in operation in Germany and Sweden. 

Typically, the raw material for cellulose processing is a lignin-hemicellulose-cellulose (LHC) complex that is not very amenable to hydrolysis. Various pretreatments involving size reduction, separation of constituents of the complex, and processes to increase the accessibility of cellulose to hydrolytic agents may be required. These activities convert a relatively intractable raw material into a cellulosic substrate. 

During 1 month, a factory for the production of simple sugars, C6H1206, by the hydrolysis of cellulose processes 1 million kg of cellulose. The percentage of cellulose that undergoes the hydrolysis reaction is 40%. How many kilograms of water are consumed in the hydrolysis of cellulose each month ... 

Among the renewable raw materials, cellulose is among the most abundant ones. In contrast to other carbohydrates, such as saccharose or starch cellulose, processing does not compete with food production. In the context of examples of the conversion of carbohydrates, the term cellulose may also include oligosaccharides and monosaccharides, such as sucrose or glucose. This is because cellulose conversion almost always includes a depolymerization to soluble fragments, which are further converted. 

Castellan et al. [171] have recently suggested that dityrosine protein residues or p-hydroxycinnamic acid are possible candidates for the fluorphores in pure cellulose. Other recent studies [172,173] have shown that typical cellulose processing conditions (e.g., hot alkali) can induce the formation of small amounts of aromatic structures from reducing end groups or hemicelluloses. However, many of the structures identified in these studies are quinones, which are at best weakly fluorescent. 

Cellulose Processing. Organic Materials Review Institute. 

Spano (2 at the U.S. Army Laboratories has reassessed the economics of cellulose process technology for production of ethanol using urban waste as a cellulosic substrate. The results of this study are encouraging. With impoved cellulose productivity and by-product credits of 0.54/gal of ethanol. Spano has been able to get the lowest estimated cost down to 0.89/gal of 95% ethanol using a unit cost of 0.11/gal of alcohol for the cellulosic material. 

Spano, L. "Revised Economic Analysis of Cellulose Process Technology", Fuels From Biomass Fermentation Newsletter Rensselaer Polytechnic Institute, Troy, N. Y., July 1978, Item 4, p 9. 

Markovits A, Chamy R, lUanes A et al. (2004) Upgrading of residues from Kraft cellulose process by the production of aromas, pharmaceuticals and nutraceuticals by enzyme biocatalysis. Final Report, Project FONDEF DOOI 1096, CONICYT, Chile. 

Sulfate 7 is a by-product of cellulose production. It forms during extraction of the wood according to the sulfate cellulose process about 10 kg/t cellulose are obtained. 

Researchers from the Finish company, Neste Oy, discovered their own cellulose process by activating cellulose with liquid ammonia at —35°C [87,88]. They then treated the activated cellulose with urea at 135-145°C which led to the formation of cellulose carbamate with the DS of 0.15 2.0. The polymer can be readily dissolved in diluted caustic soda solution. The main disadvantage of this technology is its relatively high cost. 

S. Yamanaka, E. Ono, K. Watanabe, M. Kusakabe, and Y. Suzuki, Hollow microbial cellulose, process for preparation thereof, and artificial blood... 

Cellulose oligomers containing less than ten monomers are water-soluble (Atalla et al., 2008). It is expected that the cellulose chains are hydrated at the elementary nanofibril level and that cellulose processing at high temperature reduces the hydration. Thus, an increase in temperature changes the state of aggregation of native celluloses. Water aids in the relative motion of nanofibrils, while removal of water causes dryness and stimulates formation of hydrogen bonds between nanofibrils. This... 

In Transactions of the 2001 Fundamental Research Symposium, BPBMA, Oxford, pp 897-926 Matsuda Y, Hirose M, Ueno K (2001) Super microfibrillated cellulose, process for producing the same and coated paper and tinted paper using the same. U.S. Pat. 6,214,163 Bl, Tokushu Paper Mfg. Co. Ltd, 18 pp... 

In general, dialysis is used with aqueous solutions on both sides of the membrane. The film resistances can be appreciable compared to the membrane resistance. Applications include recovery of sodium hydroxide in cellulose processing, recovery... 

Figure 18-3. Regenerated cellulose process with xanthate cellulose solution...

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