Reaction Calorimetry
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We deliver more than just the characteristic data for your substances.
For every product produced by an exothermic chemical reaction, the exact determination of the reaction behaviour by reaction calorimetric measurements is absolutely necessary. The methods and technologies of reaction calorimetry differ, however, both in terms of their suitability for the substances under investigation and in terms of measurement accuracy and the resulting costs.
CSE-Engineering is your partner in all questions concerning reaction calorimetric measurements. From sampling, sample preparation, evaluation of the measurements and safety assessment of the measurement results, we are at your disposal.
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Dr.-Ing. Natalie Schmidt
Process Safety Engineer
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Differential Scanning Calorimetry
Thermogravimetric Analysis
Accelerating Rate Calorimetry
TAM – Thermal Activity Monitoring
DSC – Differential Scanning Calorimetry
Dynamic differential calorimetry (DSC) or differential thermal analysis (DTA) is a method for measuring the amount of heat emitted or absorbed by a sample during heating, cooling or an isothermal process. ARCA crucible with a sample and a reference sample are exposed together in a heat bath to a defined temperature change. Due to the heat capacity of the sample and the exothermic or endothermic processes or phase changes, temperature differences occur between the sample and the reference. This method is used as a screening method to characterize the heat release or absorption of chemical substances.
The DSC is a simple and cost-effective method to evaluate chemical reactions. A DSC should be elaborated for each production and is the basis for further, more precise methods or also the design of safety devices.
Measurement principle:
The sample (1 – 10 mg) is subjected to a constant heating rate and the heat flow into or out of the sample is recorded.
Measured quantities:
- Phase transitions
- Glass transition temperature
- Melting temperature and enthalpy
- Decomposition temperature and enthalpy
- Onset
Standard parameters:
- Temperature range from -100 °C to 600 °C
- Measurement under air or inert gas atmosphere
- Open, perforated or closed crucibles (not pressure-resistant) made of aluminium
Options:
- High-pressure crucible for the determination of the decomposition enthalpy made of stainless steel or gold-plated
- Measurements at different heating rates to investigate decomposition kinetics
TGA – Thermogravimetric Analysis
Thermogravimetric analysis (TGA) is used to characterize temperature-dependent physical and chemical material properties in a precisely controlled atmosphere. ARCIn TGA, the mass of a sample is measured while it is heated or cooled in a specified atmosphere. It is mainly used to characterize materials with regard to their composition. With a TGA/DSC instrument it is even possible to measure thermal events that do not lead to a change in mass, such as melting processes, glass transitions or other solid-solid transitions.
Thermogravimetric analysis (TGA) is often used in combination with DSC, TMA and DMA. The system can be connected online to a mass spectrometer or FTIR spectrometer to determine the type of gas products produced. In combination with a moisture generator, it can also be used to investigate sorption processes.
Measurement principle:
The sample (1 – 10 mg) is subjected to a constant heating rate and the mass and mass change over temperature is recorded.
Measured quantities:
- Mass change over time and temperature
- Pressure and temperature curve during reaction
Standard parameters:
- Temperature range from ambient to 1000 °C
- Measurement under air of nitrogen flow
Options:
- Coupling with mass spectrometry
- Measurements at different heating rates to investigate decomposition kinetics
ARC – Accelerating Rate Calorimetry
The Accelerating Rate Calorimeter provides adiabatic data of a runawy reaction in a safe, controllable laboratory environment. This information contributes to a profound understanding of the basic processes involved. ARCThe exothermicity of a reaction, thermal stability of substances, gas formation processes and also the start of decomposition reactions are very precisely detectable. On this basis, various safe operating modes and procedures could be developed to reduce the risks associated with a reactive system.
The ARC belongs to the adiabatic measuring systems where temperature and pressure are measured simultaneously under malfunction conditions, similar to the pressure heat accumulation apparatus, VSP, RSST or PhiTeC. Sampling and test preparation are decisive for a representative measurement. In the closed system, gases can be superimposed and substances added in order to reproduce the malfunction scenario in a production plant as well as possible. In addition to the runaway or a decomposition reaction, possible subsequent reactions may be characterized. The measurement results of the ARC are then used to size safety devices to safeguard runaway reactions.
Sample preparation and testing is possible in an oxygen-free environment (glove box). Gaseous reaction products can be analyzed at the end of a test to improve the understanding of the reaction mechanisms.
Measurement principle:
The sample (50 – 5000 mg) is heated stepwise until an exothermic reaction is measured. The oven temperature is then adjusted to the sample temperature so that no heat flow to the outside occurs, i.e. a pseudo-adiabatic measurement.
Standard parameters:
- Temperature range from ambient to 400°C
- Measurement under air atmosphere
- Sample container made of Hastelloy, stainless steel or titanium
Measured quantities:
- Self-heating rate in exothermic reactions
- Pressure and temperature curve during reaction
- Vapour pressure curve of reaction mixtures
- Pressure rise rate in exothermic reactions
- Onset of the reaction
Options:
- Measurement under inert gas (e.g. nitrogen or argon)
- Gas sampling and analysis of reaction gases
- Reaction kinetics, Arrhenius parameters, reaction order
- Measurements of solutions
TAM – Thermal Activity Monitoring
Chemical, physical and biological processes often either lead to heat generation or they absorb heat, for example in melting processes. Such processes often start very slowly at low temperatures and accelerate increasingly. It can take days, or sometimes even weeks, for a slowly starting reaction to turn into a dangerous runaway. TAMOnly with extremely accurate measuring instruments is it possible to reliably determine such starting reactions in so-called ” warm-storage experiments”. One of these is the TAM – Thermal Activity Monitoring a versatile technique for investigating the thermal activity of processes.
Storage takes place at different temperatures and over long periods of time in order to reliably exclude the possibility of undesired reactions occurring over longer periods of time. Through direct and continuous measurement of the process under investigation, Thermal Activity Monitoring provides precise real-time data over the entire course of the process – in contrast to other analytical techniques that only provide “snapshots” of data.
Measurement principle:
The sample is kept at a constant temperature over a long period of time with a reference sample in an oil bath and all incoming and outgoing heat flows are measured very precisely, i.e. the measuring principle is isothermal.
Measured quantities:
- Onset of chemical reactions, storage temperature
- Temperature curve during reaction
Standard parameters:
- Temperature range from 15 °C to 150 °C
- Measurement in an oil bath
- Sample container made of stainless steel or glass
Options:
- Measurement under inert gas
- Reaction kinetics, Arrhenius parameters, reaction order
- Measurements of solutions
Images courtesy of TA Instruments, Eschborn, Germany
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