Experimental methods in chemical engineering: Thermogravimetric analysis—TGA

Abstract

Thermogravimetric analysis (TGA) is a quantitative analytical technique that monitors the mass of a sample from 1 mg to several g as a furnace ramps temperature to as high as 1600°C under a stable or changing gas flow. The first gravimetric test was in 27 BC when Vitruvius measured limestone's change of mass as it calcined to lime. In modern chemical engineering, researchers apply the technique to derive conversions, kinetics, and mechanisms for any process with a change of mass by isothermal, non‐isothermal, and quasi‐isothermal methods. The mass drops as the sample decomposes, volatile compounds evaporate, or the oxidation state decreases, while in reactive environments (with O2, for example), the mass of transition metals may increase. TGA is incapable of detecting phase transitions, polymorphic transformations, or reactions for which mass is invariant. DSC or DTA couple with TGA to help deconvolute a DSC plot by separating physical changes from chemical changes. Evolved gas analysis techniques monitor the gaseous products exiting the TGA furnace on‐line as the temperature ramps. A bibliometric map of keywords from articles citing TGA indexed by Web of Science in 2016 and 2017 identified five research clusters: nanoparticles, performance, and films; crystal structures, acid, and oxidation; composites, nanocomposites, and mechanical properties; kinetics, pyrolysis, and temperature; and adsorption, water and wastewater, and aqueous solutions. This review provides an overview of the basic principles of modern TGA.

Issue Highlights

“…Fluidized bed TGA, induction heating fluidized bed TGA, and microwave TGA are emerging configurations to maximize heat transfer rates to better characterize kinetics. The major research clusters that apply TGA include: nanoparticles and films; crystal structures and oxidation; nanocomposites and mechanical properties; kinetics and pyrolysis; and adsorption, wastewater, and aqueous solutions …”

Uso de nano y micro formulaciones orales de pectina, funcionalizadas con hierro, en la conservación de bacterias lácticas

“…Un tubo protector aísla tanto los elementos calefactores como los serpentines de refrigeración del plato de muestra. Un gas de purga dinámico pasa sobre la muestra, con un flujo de entre 20 y 200 mL/min (Figura IA3) (Saadatkhah, et. al, 2020).…”

“…Figura IA3. Representación esquemática de un analizador termogravimétrico (Saadatkhah et. al, 2020).…”

“…De manera general, los termogramas se pueden analizar de la siguiente manera (Saadatkhah et. al, 2020):…”

“…Figura IA4. Cinco posibles secciones de un termograma (curva TGA (verde), curva DTG, primera derivada (rojo), curva DDTG, segunda derivada (azul) de Mn(CH3CO2)2.4H2O calentado hasta 900 °C en aire) (Saadatkhah et. al, 2020).…”