Temperature Exothermic processes

Adsorption is invariably an exothermic process, so that, provided equilibrium has been established, the amount adsorbed at a given relative pressure must diminish as the temperature increases. It not infrequently happens, however, that the isotherm at a given temperature Tj actually lies above the isotherm for a lower temperature Ti. Anomalous behaviour of this kind is characteristic of a system which is not in equilibrium, and represents the combined effects of temperature on the rate of approach to equilibrium and on the position of equilibrium itself. It points to a process which is activated in the reaction-kinetic sense and which therefore occurs more rapidly as temperature is increased. 

Acrolein a.s Dienophile. The participation of acrolein as the dienophile in Diels-Alder reactions is, in general, an exothermic process. Dienes such as cyclopentadiene and l-dieth5laniino-l,3-butadiene react rapidly with acrolein at room temperature. 

The work of Thiele (1939) and Zeldovich (1939) called attention to the fact that reaction rates can be influenced by diffusion in the pores of particulate catalysts. For industrial, high-performance catalysts, where reaction rates are high, the pore diffusion limitation can reduce both productivity and selectivity. The latter problem emerges because 80% of the processes for the production of basic intermediates are oxidations and hydrogenations. In these processes the reactive intermediates are the valuable products, but because of their reactivity are subject to secondary degradations. In addition both oxidations and hydrogenation are exothermic processes and inside temperature gradients further complicate secondary processes inside the pores. 

A plot of the solubility of a certain compound (g/100 g H20) against temperature (°C) is a straight line with a positive slope. Is dissolving that compound an exothermic process ... 

Radical additions lo double bonds are, in general, highly exothermic processes and rates increase with increasing temperature. The rcgiospccificity of addition to double bonds and the relative reactivity of various olefins towards radicals are also temperature dependent. Typically, specificity decreases with increasing temperature (the Reactivity-Selectivity Principle applies). However, a number of exceptions to this general rule have been reported. 8 63... 

Differential scanning calorimetry (DSC) experiments on the various dimeric carbocycles indicated that, depending on the length of the alkyl groups, thermal polymerization had occurred between 100 and 125°C as an abrupt, exothermic process. The narrow temperature range for each exotherm was suggestive of a chain reaction however, IR spectroscopy revealed the absence of acetylene functionalities in the polymerized material. Consequently, none of the substi-... 

This is a useful expression for calculating equilibrium concentrations. One can easily see that for an exothermic process (AH negative) the equilibrium concentration of products decreases with temperature, while it will also increase with pressure if the process consumes gas (vc + t A - < ) ... 

Describe the anticipated temperature change of a system in which an exothermic process is taking place. 

Qs = heat generated in the system. If heat is evolved (exothermic processes) Qs is taken as positive, and if heat is absorbed (endothermic processes) it is taken as negative. Qp = process heat added to the system to maintain required system temperature. 

While subtle differences between gels synthesized with different initiators may exist, they are not easy to anticipate. The most important concern is usually the polymerization rate induced by a given initiator concentration [7], Polymerization reactions are highly exothermic, so a fast initiation rate can lead to a rapid temperature increase since the initiation and polymerization rate both increase rapidly with temperature, this process becomes autocatalytic. Poor quality, irre-producible gels result on a production scale such a runaway reaction could be-... 

The sample temperature is increased in a linear fashion, while the property in question is evaluated on a continuous basis. These methods are used to characterize compound purity, polymorphism, solvation, degradation, and excipient compatibility [41], Thermal analysis methods are normally used to monitor endothermic processes (melting, boiling, sublimation, vaporization, desolvation, solid-solid phase transitions, and chemical degradation) as well as exothermic processes (crystallization and oxidative decomposition). Thermal methods can be extremely useful in preformulation studies, since the carefully planned studies can be used to indicate the existence of possible drug-excipient interactions in a prototype formulation [7]. 

This is another example of a highly exothermic process which requires strict temperature control to ensure appropriate selectivity to gasoline, while limiting the production of lighter hydrocarbons. Again, the enhanced temperature control provided by a fluidized-bed system greatly improves the feasibility of this process. 

The word exothermic comes from two Greek roots thermo, meaning energy or temperature, and exo meaning outside or beyond. An exothermic process therefore gives out energy. 

Chemical facilities have to be operated safely during normal operation as well as during deviations from the specified process and equipment parameters. Chemical reactions that go to completion can only become a hazard for humans and the environment when process pressures or temperatures rise beyond the equipment design parameters of a facility e.g., as result of a runaway reaction. For example unacceptable pressure increases can develop as a result of exothermic processes with inadequate heat sinks or reactions that produce gaseous products (e.g., decompositions). 

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