Larger-scale calorimetry

The use of DSC and ARC provides for characterization of the electrodes and cells and the response to thermal transients. Larger-scale calorimetry (e.g., oxygen... 

The scale of the sample micro-calorimetry (mg), macro-calorimetry (g), preparative or bench scale (hg-kg). This classification is essentially useful when the amount of available reactants is limited, or when dangerous reactions have to be studied. In such a case, using only small amounts allows one to run the experiments safely. Of course, larger scales perform more realistic experiments in the sense that they mimic the manufacturing process. 

Of course, not all methods of cocrystal production require the use of auxiliary solvents. Thermal microscopy was used to determine if a particular carboxylic acid could cocrystallize with 2-[4-(4-chloro-2-fluorophe-noxy)phenyl]pyrimidine-4-carboxamide, with positive interactions being detected as crystalline material being produced at the binary interface [35]. Once identified, authentic cocrystal systems were prepared on a larger scale using solution-phase methods. In a similar study, hot-state microscopy was used to screen the possible interactions of nicotinamide with seven compounds of pharmaceutical interest that contained carboxylic acid groups [36]. A screening method for cocrystal formation based on differential scanning calorimetry has also been described, and used to demonstrate cocrystal formation in 16 out of 20 tested binary systems [37],... 

In this chapter we have presented an overview of scale-up considerations involved as one moves from bench-scale reaction calorimetry to larger scale pilot plant and production reactors. Our focus has been on heat transfer and single-phase processes, addressing primarily the problem that the heat transfer area per unit reactor volume decreases with scale. Clearly, there are many challenging problems associated with multiphase vessels, with evaporation/distillation and crystallization as obvious examples, but these topics are beyond the scope of this chapter. 

The set-up gives the opportunity to work at larger scale with reaction conditions close to those of industrial reactors. In fact, most of the studies related to SCF chemical reaction applications are reahzed in small-scale batch or tubular reactors (1-60 mL). So far, very few pubhcations deal with calorimetry applied to the supercritical phase. 

One of the main advantages of reaction calorimetry on the larger scale is the possibility of inserting into the reactor special analytical probes for on-line measurements. Some preliminary results obtained by coupling an ultrasonic sensor with calorimetry are presented in Fig. 5.17. The sensor is directly inserted into the reactor, its contribution in terms of heat accumulation having been previously determined so that the calorimetric signal is only related to the chemical reaction and process. At the moment, only the sound wave measurement is compared to the... 

Table 4.1 also gives the half life, which is the time taken for the temperature to fall to half its original value, and the time required for a 1 K temperature drop. It can be seen that the heat losses from the typical small-scale tests used are far greater than occurs in plant items. The data obtained therefore has to be extrapolated. Tests using simple glass Dewars can simulate small plant reactors, up to 12.7 m. However, to obtain data under conditions that represent larger reactors it is necessary to use adiabatic Dewar calorimetry. ... 

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