Cellulose exothermic reactions

Solution Process. With the exception of fibrous triacetate, practically all cellulose acetate is manufactured by a solution process using sulfuric acid catalyst with acetic anhydride in an acetic acid solvent. An excellent description of this process is given (85). In the process (Fig. 8), cellulose (ca 400 kg) is treated with ca 1200 kg acetic anhydride in 1600 kg acetic acid solvent and 28—40 kg sulfuric acid (7—10% based on cellulose) as catalyst. During the exothermic reaction, the temperature is controlled at 40—45°C to minimize cellulose degradation. After the reaction solution becomes clear and fiber-free and the desired viscosity has been achieved, sufficient aqueous acetic acid (60—70% acid) is added to destroy the excess anhydride and provide 10—15% free water for hydrolysis. At this point, the sulfuric acid catalyst may be partially neutralized with calcium, magnesium, or sodium salts for better control of product molecular weight. 

Peguy, A. el al., J. Appl. Poly, Science, 1990, 40(3/4), 429 Solutions of cellulose in wet methylmorpholine oxide can undergo exothermic reaction to the point of explosion if confined at elevated temperatures from about 120°C or if otherwise heated to 180°C. The reaction is catalysed by some metals, notably copper. 

O-Nitration is an exothermic reaction. Approximate calculations which have been made (Kagawa [70] Calvet and Dhers-Pession [71]) on the basis of esterifying methyl alcohol and cellulose indicate that the esterification of one hydroxyl group is accompanied by the development of 2 0.2 kcal of heat (see pp. 46, 147). 

SAFETY PROFILE Poison by ingesdon and subcutaneous routes. Moderately toxic by skin contact and inhalation. Corrosive. A severe skin and eye irritant. Mutation data reported. Flammable liquid when exposed to heat or flame can react with oxidizing materials. To fight fire, use alcohol foam, foam, CO2, dry chemical. Exothermic reaction with cellulose nitrate does not proceed to ignition. When heated to decomposition it emits toxic fumes of NOx. 

In wood pyrolysis, it is known that several parameters influence the yield of pyrolytic oil and its composition. Among these parameters, wood composition, heating rate, pressure, moisture content, presence of catalyst, particle size and combined effects of these variables are known to be important. The thermal degradation of wood starts with free water evaporation. This endothermic process takes place at 120 to 150 C, followed by several exothermic reactions at 200 to 250°C, 280 to 320 C, and around 400 C, corresponding to the thermal degradation of hemicelluloses, cellulose, and lignin respectively. In addition to the extractives, the biomass pyrolytic liquid product represents a proportional combination of pyrolysates from cellulose, hemicelluloses. 

RUBIDIUM HYDROXIDE (1310-82-3) RbOH Extremely basic substance more basic than potassium hydroxide. Extremely hygroscopic. Violent, exothermic reaction with water. Violent reaction with acids, acrylonitrile, glycidol, nitrobenzene, TNT. Exothermic decomposition with maleic anhydride. Hydrolyzes angiotonin. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Increases the explosive sensitivity of nitromethane. Reacts with nitroalkanes, forming explosive products. Attacks glass, metals, plastics, and mbbers. 

Because of their size-related large specific surface area, fine and ultrafme solid wastes, especially metallic fines or those containing metals or cellulosic dusts, are very reactive. Even at ambient conditions they combine easily with oxygen in an exothermic reaction that may cause accelerated, catastrophic heating or dust explosions . Size enlargement by agglomeration, accompanied by densification, sometimes... 

Violent exothermic reaction can occur when concentrated sulfuric acid is mixed with acrylonitrile, picrates, bromine penta-fiuoride (Mellor 1956), and chlorine trifluoride. Reactions with caustic alkalies, amines, alcohols, aldehydes, epoxides, vinyl and ally compounds, cellulose, and sugar are vigorously exothermic. 

Acetylation of cellulose is a highly exothermic reaction using acetic anhydride and acid catalyst. Therefore, it is necessary to control the temperature during acetylation, or the rate of depolymerization will become excessive resulting in a loss of target viscosity. However, the extent of cooling needed depends on the particular process. 

Precaution Corrosive flamm. exposed to heat, flames incompat. with oxidizing agents (risk of fire/explosion), strong acids, acid chlorides, acid anhydrides (violent reactions possible) exothermic reaction with cellulose nitrate does not proceed to ignition... 

It has been suggested [107-109] that the volatilization of moisture and endothermic pyrolysis usually precedes the exothermic decomposition of cellulose thus the endothermic reactions occur at lower temperatures than the exothermic reactions. 

Glacial acetic acid acts as the solvent in an excess of 10-40%. Sulfuric acid (2-15% based on cellulose) catalyzes the exothermic reaction. Temperature is kept below 50 °C. A highly viscous solution of the triester is obtained. 

G. Nitrierung F. nitration N. is the introduction of a nitro group as an -C-NO2 bond into an organic compound. This type of reaction is not practiced much in context with RR. The ->esterification of alcohols with nitrous acid (-C-O-N-bond) is sometimes incorrectly called nitration. This exothermic reaction is carried out in the presence of sulfuric acid. Nitrates of interest are - cellulose nitrate (nitrocellulose) and - glyceryl trinitrate (nitroglycerine). 

Nitrations are highly exothermic, ie, ca 126 kj/mol (30 kcal/mol). However, the heat of reaction varies with the hydrocarbon that is nitrated. The mechanism of a nitration depends on the reactants and the operating conditions. The reactions usually are either ionic or free-radical. Ionic nitrations are commonly used for aromatics many heterocycHcs hydroxyl compounds, eg, simple alcohols, glycols, glycerol, and cellulose and amines. Nitration of paraffins, cycloparaffins, and olefins frequentiy involves a free-radical reaction. Aromatic compounds and other hydrocarbons sometimes can be nitrated by free-radical reactions, but generally such reactions are less successful. 

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