Exothermic processes description

This is a step in a process that was recently developed at AstraZeneca. The original process description specified 10 mole equivalents of chlorine to be used. A reaction mechanism was postulated suggesting that only 3 mole equivalents were required, therefore the rest was effectively wasted. Attention was focused around improving the mass transfer of the chlorine. Laboratory experiments showed that the reaction kinetics is extremely fast and highly exothermic. Scale-up mixing utilities, provided with DynoChem, were used to provide required agitation rates in the laboratory to ensure the gas was fully dispersed. 

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. 

A description is given of a comparative study of the glycolysis of PETP waste soft drinks bottles by various mixtures of EG and DEG with subsequent polyesterification of the glycolysed products by maleic anhydride in order to obtain unsaturated polyesters suitable for the production of varnishes. The processing characteristics such as viscosity, exotherm temperatures of curing, compatibility of resins with monomers was investigated with respect to the type and amount of reactive monomers. The mechanical properties of varnishes produced were analysed. 13 refs. 

The example simulation THERMFF illustrates this method of using a dynamic process model to develop a feedforward control strategy. At the desired setpoint the process will be at steady-state. Therefore the steady-state form of the model is used to make the feedforward calculations. This example involves a continuous tank reactor with exothermic reaction and jacket cooling. It is assumed here that variations of inlet concentration and inlet temperature will disturb the reactor operation. As shown in the example description, the steady state material balance is used to calculate the required response of flowrate and the steady state energy balance is used to calculate the required variation in jacket temperature. This feedforward strategy results in perfect control of the simulated process, but limitations required on the jacket temperature lead to imperfections in the control. 

The raw data obtained for each dose of probe molecule that is, the evolution of the pressure above the sample (P) and the exothermic heat evolved signal (0 as a function of time (Figure 13.5a). The study of the time constant of the heat evolution for each dose provides a description of the kinetics of the adsorption process. 

Predictive hazard evaluation procedures may be required when new and different processes, designs, equipment, or procedures are being contemplated. The Dow Fire and Explosion Index provides a direct method to estimate the risks in a chemical process based upon flammability and reactivity characteristics of the chemicals, general process hazards (as exothermic reactions, indoor storage of flammable liquids, etc.) and special hazards (as operation above the flash point, operation above the auto-ignition point, quantity of flammable liquid, etc.). Proper description of this index is best found in the 57-page Dows Fire and Explosion Index, Hazard Classification Guide, 5 th ed., AIChE, New York, 1981. 

Detonation is universally defined as a chemically supported shock wave. It is a cooperative process in which the shock wave activates an exothermic chem reaction and the chem reaction, in turn, supports the shock. The products generated in such detonation reactions are the subject of this article. A very, cursory description of detonation products was given in Vol 4, D494-R. Below we will consider the main equilibria that control the compn of detonation products, and... 

Description The technology encompasses three main processing areas reactor section, product distillation and PX recovery. Fresh toluene and recycled toluene from the product distillation area are mixed with hydrogen. The hydrogen to toluene ratio is about 1 to 1.5. The mixed stream is then heated against reactor effluent and sent through a process furnace. This heated vapor stream flows to the reactor, which produces the benzene and xylenes. The toluene disproportionation reactions are mildly exothermic. 

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