Changing Temperature Control Parameters

More and more scientists routinely use reaction calorimetry thanks to the wider availability and affordability of advanced process calorimetry instruments,  their larger volume range (from ml to multi-liter), and ease of use of intuitive software (iControl ). Reaction calorimeter technologies that used to be for specialists are now becoming mainstream. However, in some cases more advanced expertise is needed when the safety and reliability of a process scale-up is at stake.

When running heat flow calorimetry in EasyMax, OptiMax or RC1e, reaction temperature (Tr) control parameters (PI) don’t usually need to be adjusted or changed unless needed.

But how can you tell?
iControl software has PI parameters optimized for a fill volume at least 75 % of the nominal volume. In case the fill volume and/or heat capacity of the reaction mixture are small, noise in the heat flow trend (Tr-Tj) will be observed (Figure 1)

Heat Flow (Tr-Tj) Profile

Figure 1. Heat flow (Tr-Tj) profile as a function of time and reaction volume for P=3.0

Using the default P=3.0 for a fill volume of 60 ml and heat capacity of 1.35 J/g.˚C causes the temperature control system to overly react, which results in a noisy (Tr-Tj) trend and sub-optimal  accuracy and precision when measuring heat capacity (Cp) and heat transfer coefficient (U). As THF is added, up to 105 ml reaction volume, the default P variable matches the reactor content better, which results in a fine temperature control behavior as seen during the calibration step (expected square wave response).

How to deal with a small fill volume and/or heat capacity?

P can be turned down to improve the quality of the (Tr-Tj) signal, and the entire heat evaluation as a result (Figure 2).

Figure-2-Heat-Flow-Profile

Figure 2. Heat flow (Tr-Tj) profile as a function of time and reaction volume for P=2.0

P=2 works nicely in this case. Sometimes, more iteration is needed to find an optimum P value.

Further Resources

Depending on the development stage, different types of information is required. The small heat flow calorimeter, EasyMax HFCal, provides reaction safety information early in development while the larger heat flow calorimeter, OptiMax HFCal, determines heat and scalability details to safely scale processes. The industry standard RC1 reaction calorimeter is suitable for comprehensive investigations in process safety.

Download the Guide to Reaction Calorimetry.