Thermochimica Acta 500 (2010) 93–99 Contents lists available at ScienceDirect Thermochimica Acta journal homepage: www.elsevier.com/locate/tca Effect of temperature gradient in sample cells of adiabatic calorimeters on data interpretation Arcady Kossoy ∗ , Irina Sheinman ChemInform St. Petersburg (CISP) Ltd., 14, Dobrolubov Ave., 197198 Saint Petersburg, Russia article info Article history: Received 16 July 2009 Accepted 4 January 2010 Available online 13 January 2010 Keywords: Adiabatic calorimeter Mathematical simulation Temperature gradient Reaction kinetics Reaction hazard abstract The thermal behavior of sample cells (bombs) of the ARC and VSP adiabatic calorimeters has been inves- tigated by applying mathematical simulation. Influence of temperature gradient in a calorimetric bomb on the inaccuracy of kinetic parameters evaluated from adiabatic data has been analyzed. Then possi- ble errors in kinetics-based predictions caused by the inaccuracy of kinetic parameters were identified by the example of two important hazard indicators – adiabatic time to maximum rate, TMR, and the self-accelerating decomposition temperature, SADT. A new control method for maintaining sample adi- abaticity is proposed that provides obtaining the most correct experimental data suitable for creation of reliable kinetics. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Adiabatic calorimetry is well known as one of the main meth- ods for investigation of reaction hazards. It can be very useful for initial screening of reactive chemicals and mixtures and for getting more detailed data necessary for evaluation of potential reaction hazards. An important advantage of the method is that the results obtained can be scaled-up relatively easily to simu- late unwanted behavior of a large reactor or the whole process. Furthermore adiabatic calorimetry gives valuable information that can be successfully used for evaluation of reaction kinetics. Esti- mation of some basic kinetics is required for implementing such typical procedures as correction of experimental results due to thermal inertia [1], assessment of adiabatic TMR [2,3], evaluation of SADT (e.g. [4,5]). More detailed kinetics can be successfully used for simulation-based assessment of reaction hazards. One of the primary ideas the adiabatic data interpretation is based on is that the temperature and concentration gradients within the sample are negligible (that is, the system close to uni- form). This allows simple determination of the reaction heat, easy evaluation of basic kinetics, etc. The main origin of possible devia- tion from uniformity is heat loss from the sample to the cell (bomb) material – the thermal inertia. This violates adiabaticity of the sam- ple and causes appearance of temperature gradients in a sample. The gradient may result in errors even when performing such sim- ∗ Corresponding author. Tel.: +7 812 499 90 85; fax: +7 812 703 05 89. E-mail address: Kossoy@cisp.spb.ru (A. Kossoy). ple data analysis as estimation of reaction heat. More serious errors can be made when evaluating kinetics from experimental data. Though thermal processes in an adiabatic calorimeter were con- sidered to a certain extent in several articles [6–8] this subject needs further more detailed analysis with the specific focus on the influence of the temperature gradient on the correctness of data interpretation in general and on reliability of kinetics in particular. Nowadays the latter aspect is increasingly important because adi- abatic data are more and more often used as a source for creation of complex kinetic models (e.g. [9–12]). This paper represents the results of such in-depth analysis. First, the correlation between the non-uniformity and conditions of heat exchange between calorimetric bomb and external oven/heater that maintains adiabaticity for the bomb will be discussed. The assessment of possible errors of kinetic parameters evaluated under the assumption that temperature is uniform will follow. Effect of these errors on accuracy of hazard assessment will be demonstrated by the example of estimating the adiabatic TMR and SADT. Direct experimental investigation of this problem is very dif- ficult if not impossible. Therefore the alternative mathematical simulation approach has been used. All calculations presented in the article are based on the abstract kinetic models of an N-order and autocatalytic reactions to reveal the peculiarities of thermal behavior and avoid superfluous complications. Furthermore ide- alized instruments are considered, that is, possible heat losses along the construction elements of a calorimeter are not taken into account and the ideal retardation-free control system that main- tains adiabaticity is assumed. 0040-6031/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.tca.2010.01.003