Volume change during reaction

Constant-volume batch reactors are found very frequently in industry. In pai -ticular, the laboratory bomb reactor for gas-phase reactions is widely used for obtaining reaction rate information on a small scale. Liquid-phase reactions in which the volume change during reaction is insignificant are frequently carried out in batch reactors when small-scale production is desired or operating difficulties rule out the use of continuous systems. For a constant-volume batch reactor. Equation (2-5) can be arranged into the form... 

So far only the case of an isothermal reaction without volume change has been considered. A volume change during reaction (isothermal case) has no effect on if if only Knudsen diffusion is operative but has a small effect if bulk diffusion is... 

One other problem, which is not unique for zeolites, but occurs in many zeolite catalyzed reactions, is the fact that gas volumes change during reaction. This makes it more difficult to ensure equal space velocity over all zeolites. If the flow restrictors, for instance capillaries, are placed in front of the catalyst bed, the influence of changing volumes can be minimized. If the restrictors are downstream of the catalyst, additional flow controlling elements have to be incorporated, such as a mass flow controller in the analysis line (to a first approximation not sensitive to changed volume flow). 

Calculate overall rates during the entire course of reactions, the initial rate being taken as unity. Neglect minor volume changes during reaction. Plot, versus time, the overall rate as well as the composition of the system. 

Densities of the various compounds were determined by picnometry, at temperatures between 110 and 150 C, from which values the molar concentration can be deduced, by assuming that there was no volume change during reaction, it was possible to calculate the rate constants of the various reactions. 

In these equations, AS° represents the standard entropy of reaction and AV° the volume change during reaction. AS° is obtained from (2.53), where S° is the entropy of formation of the individual neutral and ionic species that participate in the reaction (the standard entropy of a perfect solid at 0 K is defined as having the value of zero) and yp represents their molar volumes ... 

If the relation between the density of the reaction mixture and the reactant concentration is known, the latter can be calculated as a function of time. However, if we describe the progress of the reaction in terms of the degree of conversion, see eq. (3.8), we d the same solution as eq. (3.15), which indicates that volume changes during reaction do not influence the rate of conversion of first order reactions. 

Here, we represent concentrations on a per-mass basis, due to volume changes during reaction. M is the total mass of the reaction medium in the reactor. and are the inlet... 

The above equations are valid only when there is no volume change during the course of reaction. 

Work (w) is defined as the distance moved times the force that produces the motion. In chemistry, most work is expansion work (PV work) done as the result of a volume change during a reaction when air molecules are pushed aside. The amount of work done by an expanding gas is given by the equation w = —PAV, where P is the pressure against which the system must push and AV is the change in volume of the system. 

Assume negligible volume change during the reaction so that C, = Cs( 1 Xs). 

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