Few reports exist on the use of Diffuse Reflectance Infrared Fourier Transform Spectrometry coupled with Mass Spectrometry (DRIFTS-MS) in situ to monitor the dehydroxylation of kaolinitic clays. The use of DRIFTS-MS in situ allows study of the effect of heat treatment on the dehydroxylation, identifying intensities and temperatures at which the hydroxyl groups are released, forming metakaolinite and meta-alunite. The effluent gases from the infrared cell were analysed by mass spectrometry. The decrease in intensity of the bands at 3694, 3669, 3650 and 3621 cm⁻¹ associated with the −OH stretching vibration modes of Al^VI−OH−Al^VI of kaolinite began at 450°C. Two additional bands at 3513 and 3485 cm⁻¹ are associated with the vibration of Al^VI−OH of alunite that also began to disappear during thermal treatment. Monitoring of the fractions m/e 17 and 18 using a mass spectrometer revealed that the intensity of these fractions increased starting at 450°C. Therefore, it is possible to study the dehydroxylation process of clays during thermal treatment.Chemical and mineralogical characterization of a kaolinitic clay (KN) fromMexico showed that the clay consists of 64.8% kaolinite, 11.0% alunite and 24.4% quartz based on PXRD, EDS, TG/DTA, TEM and FTIR results, and suggested that the material might have potential for use in the manufacture of ceramics, refractory bricks or geopolymers.

A numerical study on 2D natural convection in cylindrical cavities during the sterilization of liquid foods was performed. The mathematical model was established on momentum and energy balances and predicts both the heating dynamics of the slowest heating zone (SHZ) and the lethal rate achieved in homogeneous liquid canned foods. Two sophistication levels were proposed in viscosity modelling: 1) considering average viscosity and 2) using an Arrhenius-type model to include the effect of temperature on viscosity. The remaining thermodynamic properties were kept constant. The governing equations were spatially discretized via orthogonal collocation (OC) with mesh size of 25 × 25. Computational simulations were performed using proximate and thermodynamic data for carrot-orange soup, broccoli-cheddar soup, tomato puree, and cream-style corn. Flow patterns, isothermals, heating dynamics of the SHZ, and the sterilization rate achieved for the cases studied were compared for both viscosity models. The dynamics of coldest point and the lethal rate F₀ in all food fluids studied were approximately equal in both cases, although the second sophistication level is closer to physical behavior. The model accuracy was compared favorably with reported sterilization time for cream-style corn packed at 303 × 406 can size, predicting 66 min versus an experimental time of 68 min at retort temperature of 121.1 ℃.