Determination of Reaction Parameters Using a Small Calorimeter with an Integrated FT-IR Probe and Parameter Fitting (original) (raw)
Related papers
2003
VII ABSTRACT To meet the need for a systematic and quick gathering of kinetic and thermodynamic reaction parameters in early phases of process design a small reaction calorimeter (25 to 45 ml) with an integrated IR-ATR probe was developed during this work. Such a device is of particular importance for new finechemical and pharmaceutical products, where typically only small amounts of test substance are available and time-to-market is crucial. The new prototype reaction calorimeter uses a copper block as an intermediate thermostat instead of a double wall vessel (typically glass) with a circulation fluid. The reaction temperature is controlled at isothermal conditions using the Power-Compensation principle. To allow an online measured baseline (compensate changes of the heat transfer through the reactor wall during the reaction) an additional heat-flow balance using Peltier elements is implemented and was patented. This combination shortens the time required for a reaction experiment...
Industrial & Engineering Chemistry Research, 2003
We developed a new prototype reaction calorimeter with an integrated infrared-attenuated total reflection (IR-ATR) probe that has a sample volume of 45 mL and uses a metal block as an intermediate thermostat. Isothermal conditions are maintained using the power compensation principle. An additional heat balance using Peltier elements is implemented to compensate for changes of the reactor-sided heat-transfer coefficient and to circumvent corresponding calibration steps. The new calorimeter has been tested using the neutralization of NaOH with H 2 SO 4 and the hydrolysis of acetic anhydride. These experiments showed the precision of the new calorimeter and its capability to deal with fast and highly exo-or endothermic reactions. The kinetic parameters obtained from the IR and calorimetric measurements agree well with each other and with literature values. Even for the investigated simple reaction schemes, the IR-ATR probe provided additional information from what is obtained from the calorimetric signal alone.
Isothermal reaction calorimetry as a tool for kinetic analysis
Thermochimica Acta, 2004
Reaction calorimetry has found widespread application for thermal and kinetic analysis of chemical reactions in the context of thermal process safety as well as process development. This paper reviews the most important reaction calorimetric principles (heat-flow, heat-balance, power-compensation, and Peltier principle) and their applications in commercial or scientific devices. The discussion focuses on the different dynamic behavior of the main calorimetric principles during an isothermal reaction measurement. Examples of available reaction calorimeters are further compared considering their detection limit, time constant as well as temperature range. In a second part, different evaluation methods for the isothermally measured calorimetric data are reviewed and discussed. The methods will be compared, focusing especially on the fact that reaction calorimetric data always contains additional informations not directly related to the actual chemical reaction such as heat of mixing, heat of phase-transfer/change processes or simple measurement errors. Depending on the evaluation method applied such disturbances have a significant influence on the calculated reaction enthalpies or rate constants.
Isothermal reaction calorimeters—II. Data treatment
Chemical Engineering Science, 1987
I of the present study compared different design principles for calorimeters with special emphasis on the bench scale isothermal reaction calorimeter which is characterized by:
American Journal of Engineering and Applied Sciences, 2011
Problem statement: The determination of reaction kinetics is of major importance, as for industrial reactors optimization as for environmental reasons or energy limitations. Although calorimetry is often used for the determination of thermodynamic parameters alone, the question that arises is: how can we apply the Differential Scanning Calorimetry for the determination of kinetic parameters. The objective of this study consists to proposing an original methodology for the simultaneous determination of thermodynamic and kinetic parameters, using a laboratory scale Differential Scanning Calorimeter (DSC). The method is applied to the dichromate-catalysed hydrogen peroxide decomposition. Approach: The methodology is based on operating of experiments carried out with a Differential Scanning Calorimeter. The interest of this approach proposed is that it requires very small quantities of reactants (about a few grams) to be implemented. The difficulty lies in the fact that, using such microcalorimeters, the reactants temperature cannot directly be measured and a particular calibration procedure has thus to be developed, to determine the media temperature in an indirect way. The proposed methodology for determination of kinetics parameters is based on resolution of the coupled heat and mass balances. Results: A complete kinetic law is proposed. The Arrhenius parameters are determined as frequency factor k 0 = 1.39×109 s −1 and activation energy E = 54.9 kJ mol −1. The measured enthalpy of reaction is ΔrH=−94 kJ mol−1. Conclusion: The comparison of the results obtained by such an original methodology with those obtained using a conventional laboratory scale reactor calorimetry, for the kinetics determination of, shows that this new approach is very relevant.
Journal of Thermal Analysis and Calorimetry, 2001
A simple method for the on-line calibration, in which both the heat transfer coefficient and the heat capacity of the reactor contents are determined, is described for laboratory scale heat transfer calorimeters. The calorimeter is operated in the isoperibolic mode for the calibration and a constant power is supplied to a resistor placed inside the reactor. The reactor heat balance differential equation is used to produce a set of linear simultaneous equations with each data acquisition cycle giving one equation. The heat transfer coefficient and the heat capacity are obtained from this set of equations by linear least squares. The application of the calibration procedure is illustrated by experiments in which the heat of reaction is determined on-line fora simulated reaction with first order kinetics and for the hydrolysis of acetic anhydride.
Chemometrics and Intelligent Laboratory Systems, 2004
In order to identify parameters of a chemical reaction, such as rate constants, reaction orders, activation energies, or reaction enthalpies, we developed a new combined evaluation algorithm. In contrast to common evaluation procedures, it allows a simultaneous evaluation of online measured infrared and calorimetric data. Furthermore, a new weighting principle was developed that performs an automatic scaling of the infrared and calorimetric data in order to equalize their influence on the estimated reaction parameters. Such a scaling is of particular importance as two completely different measurement data sets are combined into one single objective function. The approach could be extended to more than two different analytical signals. The evaluation of the infrared data neither requires calibration nor knowledge of pure component spectra. Overlapping absorption bands are allowed. In addition, no calibration is needed for the calorimetric measurements. The feasibility of the new evaluation algorithm will be demonstrated based on the hydrolysis of acetic anhydride.
A new approach for isothermal calorimetric technique
Journal of Thermal Analysis and Calorimetry, 2009
Using flexible heat flux sensors mounted on the lateral and bottom of outside reactor wall, a new approach is developed for isothermal calorimetric technique to overcome the disadvantages of heat flow calorimetric methods. Although the proposed system needs a calibration procedure before or after the reaction completion to evaluate the lateral heat transfer area, the measurement is versatile and totally independent of the reaction media, jacket fluid, and the variations of heat transfer coefficient. Knowledge of the variations of the heat transfer coefficient is essential for the effective control and scale up of a reactor and can be inferred by the new method during the reaction. The stirrer power and the heat loss can be determined easily as well. No pre-calibration is needed for the sensors and no heating element is applied inside the reactor for temperature control. Experiments are carried out to validate the performance of the new proposed technique. With the help of a heater, the heat generated in the reactor is measured at various levels of power input. The predicted heater power inputs are in good agreement with the corresponding heat inputs. The relative detection limit in the range of 0.8-1 W L-1 is expected for this technique. Using the hydrolysis of acetic anhydride, the heat of reaction at 25°C is determined, which is within the range reported in the literatures. The capability of the system to deal with the variations in the overall heat transfer coefficient is also demonstrated using a simulated reaction.
A new reaction calorimeter and calorimetric tools for safety testing at laboratory scale
Thermochimica Acta, 2003
Calorimetry combined with thermal analysis is an essential tool for the evaluation of thermal risks linked with chemical reactions at industrial scale. The energies of synthesis reactions or decomposition reactions as well as the heat capacities of reaction masses can be measured using such techniques. The capacity of the SETARAM differential reaction calorimeter (DRC) to determine essential safety data has been demonstrated with the measurement of heat capacities of cyclohexane and propanoic acid. Results of an industrial reaction are also presented.