Reaction Calorimeters

A high-temperature and high-pressure reaction calorimeter. 

The SIMULAR, developed by Hazard Evaluation Laboratory Ltd., is a chemical reactor control and data acquisition system. It can also perform calorimetry measurements and be employed to investigate chemical reaction and unit operations such as mixing, blending, crystallization, and distillation. Ligure 12-24 shows a schematic detail of the SIMULAR, and Ligure 12-25 illustrates the SIMULAR reaction calorimeter with computer controlled solids addition. 

Figure 12-26. The SIMULAR reaction calorimeter. Features include pumped liquid feed, gas mass flow control, gas evolution measurement, and distillation equipment. (Source Hazard Evaluation Laboratory Ltd.)...

In order to investigate the kinetics, heat of reaction and other aspects of the system, the RCl reaction calorimeter was employed. This system allows to perform the reaction in a 2 liters glass reactor, while controlling the reactor and jacket temperatures. Following the reaction, the heat released at any time period can be determined. The operation and application of this system has been discussed in numerous publications (refs. 5,6). 

Reaction calorimetry is a technique which uses data on the rate of heat evolution or consumption to evaluate the thermokinetic reaction characteristics needed for reactor scale-up and/or optimization and safety. Since the late seventies, the application of this technique has been steadily growing and reaction calorimeters are now commercially available. Probably the first commercial reactor calorimeter was developed by CIBA-GEIGY (Bench Scale Calorimeter BSC) (see Beyrich et al, 1980 and Regenass et al., 1978, 1980, 1983, 1984, 1985, 1997))... 

Figure 5.4-23. Bench scale reaction calorimeter (adapted from Brogli et a/., 1981).

At present, several companies offer reaction calorimeters. Below, the specifications of the most commonly used commercial calorimeter (RKl of Mettler) are given ... 

Reaction calorimeter Wide variety of operations Useful for thermal parameters Heat is non-specific source of information for multireaction systems... 

Generally, the temperature changes with time or, equivalently, with distance from the reactor inlet (for flow reactors). This change is usually controlled well in reaction calorimeters but can become uncontrolled in other conventional laboratory flow or (semi)batch reactors. The balance equations of a batch reactor for a single reaction of a-th order kinetics are given by ... 

Thermal methods in kinetic modelling. Methods for the estimation of thermokinetic parameters based on experiments in a reaction calorimeter will be discussed below. As mentioned in section 5.4.4.3, instantaneous heat evolved due to a single reaction is directly proportional to the reaction rate. Assume that the reaction is of first order. Then for isothermal operation ... 

Example 5.4.4.3a. Kinetics of R-hydroxynitrileformation by using a reaction calorimeter. 

More complex kinetic expressions can be analysed, either in a manner similar to that shown in the above example or using methods discussed in the previous section. More complex reaction systems can also be studied if the reaction mixture is analysed during the course of reaction Tufano (1993) presented a theoretical analysis of such a case. Several examples of the use of a reaction calorimeter for kinetic studies were presented at RC User Forum (see, e.g.. 

Figure 5.4-63. Nitration isothermal runs in reaction calorimeter (adapted from Hoppe and Grob, 1990).

Experimental data can be obtained from the DSC and from reaction calorimeters for the conditions of the desired reactions, and from the DSC, the ARC, the Reactive System Screening Test (RSST—Fauske and Associates) and from the Vent Size Package (VSP) for conditions allowing undesired reactions. The pressure effect can be studied using the ARC or DIERS methods. From the results of these tests, the rate of temperature rise and the maximum acceptable conditions for specific equipment can be calculated. The same holds for the pressure rise rate. 

The RC1 Reaction Calorimeter is marketed by Mettler-Toledo. The heat-flow calorimetric principle used by the RC1 relies on continuous measurement of the temperature difference between the reactor contents and the heat transfer fluid in the reactor jacket. The heat transfer coefficient is obtained through calibration, using known energy input to the reactor contents. The heat trans-... 

A sketch of the quantitative reaction calorimeter is shown in Figure 3.14. 

If agitation fails during a semi-batch operation, the transfer of heat will essentially stop. The resulting increase in temperature depends on the concentration of the reactants at that moment, the global kinetics, and the mass transfer rate. The effect of the temperature increase is easily simulated in a reaction calorimeter both with and without addition of reactants. 

In the course of a long and thorough study of the polymerisation of isobutene (IB) by syncatalytic systems based on aluminium-organic compounds (Magagnini et al., 1977 and preceding papers) measurements were made by a Biddulph-Plesch type reaction calorimeter fitted with conductivity (k) electrodes on polymerisations of IB by Et2AlCl + Cl2 in MeCl at -45 °C, from which a kp+A value could be obtained. The reactions and procedures can be summarised as follows ... 

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