An efficient and safe transfer of chemistry from laboratory to plant scale requires process understanding. This understanding is provided by reaction calorimetric studies, an industrial standard practiced for years and typically done in batch operation. With emerging flow chemistry applications, this standard will be and needs to be extended with flow calorimetry. Flow chemistry typically utilizes highly reactive reagents with reaction half-life times of seconds to minutes. Continuous flow calorimetry opens up the possibility to safely measure such fast reactions as well as unstable intermediates. Especially data for process design can be obtained under steady-state operation, which is not possible in batch operation. Non-selective reactions, mainly seen by mixing limitations, may produce different products in continuous flow operation compared to batch and therefore pose a risk in the design of continuous flow processes when basing the safety considerations on batch data. In addition to thermal data, it is possible to obtain information about reaction times and kinetics in flow calorimetry by a segment-wise temperature or heat flux measurement. Another advantage of flow calorimetry is to generate data automatically at various operation conditions by adjusting flow rates and ratios to screen different stoichiometric conditions.
At Microinnova, we offer flow calorimetry in a tube-in-tube Fluitec reactor with static mixing elements, all made of Hastelloy. The coolant in an outer shell is held at constant temperature and measurements are done at isoperibolic conditions, whereby a heat profile is measured over the length of the reactor. This operation mode resembles a reaction in a commercial tubular reactor and provides awareness of heat transfer characteristics.
Operation conditions from 0 – 200°C can be used at a pressure of 10 bar. The device has 10 temperature measurement points within the static mixer to generate a temperature profile. Flow rates are recommended between 20 – 100 ml/min using Reynolds Numbers in the range of 0 < Re < 100 for a good measurement and viscosities of liquid materials from 1 – 120 mPas. Typical reaction times used for measurements are between <1 s and approximately 2 min. If the reaction time is longer than the fluidic residence time, a quench is needed to stop the reaction from progressing. For unfinished reactions, a quantitative analysis of the converted species is needed to base the reaction heat on consumed or formed reactants.
Continuous flow calorimetry is seen as a key technology for process development and safety analysis at Microinnova.
