Heating of reactants

Six successive units are visible on the Fig. 1.19 (left) and they are set to obtain the heating of reactants in a vertical glass pipe. Each applicator is constituted by a parallelepiped metallic box (200 x 200 x 300 mm3). The reactor is a dielectric pipe with diameter between 70 and 100 mm. This pipe passes through the box following the electric field direction within the excitation waveguide. This waveguide can be seen... 

The specific heats of reactant and product depend on temperature, according to... 

Knowing the heat of reaction at any one temperature as well as the specific heats of reactants and products in the temperature range concerned allows us to calculate the heat of reaction at any other temperature. From this the heat effects of the reaction can be found. 

The quality of the reduced kinetic models, as compared to the detailed model, has been evaluated in simulation by comparing their ability in tracking a few assigned temperature profiles. For the sake of simplicity, only the results obtained for the temperature profile shown in Fig. 3.2 are presented. The test profile considered consists of three steps heating of reactants up to a set-point temperature, reaction phase at constant temperature, and cooling down to ambient conditions. 

The formation of p-CjS from lime and quartz is moderately exothermic, but that of C3S from lime and p-CjS is endothermic, with A// = + 59 kj kg" All these calculations refer to reactants and products at 25°C and 0.1 MPa. The enthalpy changes at the temperatures at which the reactions occur are somewhat different, because the specific heats of reactants and products are not the same. The reaction of lime with CjS giving C3S changes from endothermic to exothermic at 1430°C (J4). For the decomposition of calcite at 890°C, A// is + 1644 kJ kg" (L6). 

According to (3.52), the larger the heat of reactant adsorption (larger the larger the overall rate of reaction. A larger heat of adsorption enhances the surface coverage (and changes the reaction order), and consequently, the reaction rate, e.g. to (3.51). 

In general, AGF (Tref) values are based on calculations from direct experimental reactions of the elements to form the compound and from specific heat and related calorimetric measurements on each species, which allows correction of the data from Texp (the experimental reaction temperature) to Tref. Tabulations of AG j (0 K) or AG j (298 K) for reactions and of the specific heats of reactants and products to allow temperature corrections form the source from which many chemical thermodynamic calculations are made (Ref 2). 

Heat capacities are clearly involved in the heating of reactants and cooling of products between 600 and 298 K. The simplest analysis is as follows. The change of AH with temperature is ... 

The thermodynamic data (standard enthalpy and entropy of formation, specific heats of reactants) can be taken from collections of tabulated data or estimated by methods of approximation [Ullmann, Knapp 1987]. 

Earlier it was shown that aminoarylation of the iV-methylacridinium ion by action of 7/,7/-dialkylanilines proved to proceed on heating of reactants in DMFA, DMSO (120-130°C), or BuOH (105-110°C) in the presence of air bubbling through the reaction mixture (Scheme 62) [136, 137]. 

T = reactor temperature, °F T = wall temperature, °F Wi = weight of reactants, lb Cl = specific heat of reactants, Btu/(lb)(°F) Rearranging in the standard form,... 

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