Kinetics: the key to process understanding

In order to scale-up a batch process, data is required on the rates of reaction. These cannot be predicted and must be measured. Calculating the kinetic parameters (rate constants, Arrhenius constants and reaction order) from experimental measurements can in itself provide considerable insight into the reaction mechanisms. Many people working in batch process development view the determination of reaction kinetics for complex chemical systems as totally impractical. Using modern regression techniques coupled with a process simulator this need no longer be the case.

Sources of Data for Kinetic Fitting

We can determine reaction kinetics from surprisingly few measurements. Composition of the final work up of a routine laboratory synthesis can be sufficient to discriminate between complex parallel reactions. From a reaction calorimeter, the Qr curve alone can establish kinetics for many systems. Many commercial laboratory reactor systems exist which are capable of supplying data suitable for kinetic fitting, particularly instruments used for thermal safety analysis.

       
    Sources of data for kinetic fitting  
       

These instruments operate in batch, semi-batch or continuous mode, under isothermal, adiabatic or controlled temperature profiles. Their measured outputs to which reaction kinetics can be related include concentrations, Qr, reaction volume and temperature. Reaction calorimeters are particularly useful in providing controlled operating conditions and high quality data output on which to base kinetic fitting.

Advanced regression and integration methods combined with sophisticated reaction modelling allows us to determine rate constants, Arrhenius constants, reaction orders and ΔHr for chemical systems involving multiple simultaneous reactions in parallel or in series. Composition, temperature, heat flow, volume changes or mixed data from batch, semi-batch or continuous experiments operated isothermally, adiabatically or with varying temperature can be used. LyraChem has considerable experience in dealing with non-trivial reaction systems. Networks of series, parallel and equilibrium reactions are quickly constructed. To summarise, kinetics can be fitted automatically from a number of different types of measurements including concentration, Qr, volume change and temperature either separately or using more than one data type.

For more background into kinetic fitting, click [here]

 

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