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Ultimate heat of reaction

Two variables of primary importance, which are interdependent, are reaction temperature and ch1orine propy1ene ratio. Propylene is typically used ia excess to act as a diluent and heat sink, thus minimising by-products (eqs.2 and 3). Since higher temperatures favor the desired reaction, standard practice generally involves preheat of the reactor feeds to at least 200°C prior to combination. The heat of reaction is then responsible for further increases in the reaction temperature toward 510°C. The chlorine propylene ratio is adjusted so that, for given preheat temperatures, the desired ultimate reaction temperature is maintained. For example, at a chlorine propylene molar ratio of 0.315, feed temperatures of 200°C (propylene) and 50°C (chlorine) produce an ultimate reaction temperature of approximately 500°C (10). Increases in preheat temperature toward the ultimate reactor temperature, eg, in attempts to decrease yield of equation 1, must be compensated for in reduced chlorine propylene ratio, which reduces the fraction of propylene converted and, thus aHyl chloride quantity produced. A suitable economic optimum combination of preheat temperature and chlorine propylene ratio can be readily deterrnined for individual cases. [Pg.34]

If CH4 and air at the stoichiometric ratio (9.5% CH4 in air) at atmospheric pressure are ignited at one end of a pipe, the pressure will ultimately rise by a factor of 10, and this pressure wave will travel at 300 m/sec down the pipe. The heat of reaction is -192 kcal/mole of CH4, and all this heat will be released and the pressure will rise very quickly. [Pg.433]

For thermosets, Hu is the total heat of reaction of the matrix. For thermoplastics, Hu is the theoretical ultimate heat of crystallinity. [Pg.401]

When a reaction is composed of sub-steps, the total enthalpy change will be the sum of the changes for each step. Even if a reaction in reality contains no substeps, we may still write any number of reactions in series that lead from the same reactants to the same products and their sum will be the heat of the reaction of interest. The ability to add together these enthalpies to form ultimate products from initial reactants is known as Hess s Law. It is used to determine one heat of reaction from others ... [Pg.157]

The effect of the system s properties on the steady state behavior is conveyed in the next subsection. As the level of detail might be considerably increased, three physical properties are considered heat of reaction, activation energy and relative volatility. The ultimate goal of this analysis involves the definition of trends in the steady state behavior, rather than a rigorous quantitative classification. For the sake of comparison, the system introduced in table 7.3 is labelled as reference case. [Pg.137]

Applications of DTA for Polymers. Table 2 (Ref 5, Chapt. l) describes some of the many applications of DTA and DSC. Both DTA and DSC can be used to determine the temperature of the transitions, cited in Table 2. However, the DSC peak area, in addition, gives quantitative calorimetric information (heat of reaction, transition, or heat capacity). DTA can only do so when calibration with a standard material allows the quantitative conversion of AT to heat flow and, ultimately, heat of transition (AH) or heat capacity (Cp). Also, the response of DTA with increasing temperature may be affected by poor heat transfer in the system, detector sensitivity, etc (4). For these reasons, when there is a choice between DSC and DTA, DSC is the preferred method. The illustrations shown below for applications of DSC in characterization of polymers also generally apply for DTA, with the limitations mentioned above. Therefore, DTA applications will not be considered here. Illustrations of polymer applications for DTA can be found in the Thermal Analysis section by Bacon Ke (6) in the previous edition of this encyclopedia. [Pg.8312]

Novolac oligomers obtained in the presence of HCl develop with violent heat of reaction. This is why the introduction of HCl (37% solution) is performed step by step. In the acid catalysis achieved with sufuric acid, the reaction product is brown-colored, and ultimately H2SO4 neutralization with Ba(OH)2 or Ca(OH)2 is required. [Pg.493]

We estimated reaction formula of gasification, heat of reaction, and gasification temperature of UCG carried out at Fuxin mine, Xinghe mine, Liuzhuang mine, Ezhuang mine, and Xiyang mine in China. The results of ultimate analysis and molecular formulae estimated for five coals were shown in Table 4 with their heating values. [Pg.428]

Operators were told to add a reactant at 45°C over a period of 1-11/ hours. They believed this to be impossible, as the heater was not powerful enough, so they decided to add it at a low er temperature and heat the material in the reactor. They did not tell anyone. This went on for a long period of time and, unknown to the supervisor, became the accepted practice. Again they were on the edge of a precipice, and ultimately a runaway reaction occurred with emission of toxic fumes. [Pg.387]

The potential of these reactions for methane production can be compared in terms of theoretical yields and heat recovery efficiencies. Theoretical methane yield is defined by the chemical equations. Theoretical heat recovery efficiency is defined as the percent of the higher heating value of the coal which is recovered in the form of methane product. These idealized parameters provide a measure of the ultimate capability of conversion systems and are useful for evaluating actual conversion processes. [Pg.303]


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