Experimental methods in chemical engineering: Temperature‐programmed oxidation— TPO

Abstract

Temperature‐programmed oxidation (TPO) probes the oxidative capacity and redox properties of solid materials—catalysts, metal oxides, perovskites, and carbonaceous deposits. It identifies coke type, distribution, and reactivity. TPO instruments pass an oxidizing gas (diluted , air, or less commonly , , or CO) through a micro‐reactor loaded with 20 mg to several 100 mg of solids, housed in a furnace. As the furnace ramps temperature up (), a thermal conductivity detector, mass spectrometer, or infrared detector monitors effluent concentration. Operating conditions determine peak position, shape, and intensity‐input parameters to derive consumption, kinetics, and surface reactivity: Increasing the heating rate shifts oxidation peaks to higher temperatures, whereas increasing the concentration accelerates oxidation and shifts peaks to lower temperatures. Changing sample mass and gas flow modify signal resolution; kinetics rather than mass transfer govern reaction rates with less than 100 mg for slow reactions and small particles. TCDs are adequate to characterize simple metal oxide chemistry (). For complex oxides, perovskites, and coked catalyst, complementary analytical techniques like X‐ray diffraction, Raman spectroscopy, and mass spectrometry improve TPO's capability to identify phase changes, reaction kinetics, and mechanisms. Standard deviation on repeat runs approach 1%. In 2025, articles in journals Web of Science assigns to physical chemistry mention TPO most, followed by chemical engineering, energy & fuels, then multi‐disciplinary chemistry. A bibliometric analysis assigned keywords into four categories: catalyst, Ni, , ; oxidation, mechanism, ; oxide, reduction, nanoparticle, CO; and, NOX, selective catalytic reduction, Cu.