Study of C/Doped δ-Bi₂O₃ Redox Reactions by in Operando Synchrotron X-ray Diffraction: Bond Energy/Oxygen Vacancy and Reaction Kinetics Relationships

Abstract

One major technical and economic hurdle on the sequestration of CO2 is its separation from nitrogen when fossil fuels are burned in air. An alternative, thermodynamically equivalent approach is to use a metal oxide as an oxygen carrier (oxidizer) and then recycle the carrier following its reduction by exothermic reoxidation in air. This process, termed chemical looping combustion (CLC), places many requirements on the oxygen carrier. Here, we explore how to evaluate the relationship between the microscopic properties of an oxygen carrier and its performance in CLC. In this paper, systematically doped Bi2O3 were synthesized as oxygen carriers for the oxidation of carbon. In operando synchrotron X-ray diffraction and online mass spectrometry enable us to monitor both the phase evolution in the solid and the production of gaseous products. Initiation temperature and reaction kinetics were deduced on the basis of the X-ray diffraction peak intensity change. Results show that lower metal–oxygen bond energy and higher oxygen vacancy concentration of doped Bi2O3 led to lower onset temperature, faster reaction rate, and smaller activation energy for carbon oxidation. These results provide important insights into manipulating the atomic properties of oxygen carrier for CLC applications.

Insights into Syngas Combustion on a Defective NiO Surface for Chemical Looping Combustion: Oxygen Migration and Vacancy Effects

“…Since the addition of metal promoters contributes to the distribution and concentration of oxygen vacancies, the vacancy effects are usually valued in the studies of mixed metal OCs. Zachariah et al 9 reported that the activation energy and the reaction rate of carbon doped with δ-Bi 2 O 3 were improved due to a high oxygen vacancy concentration of the doped Bi 2 O 3 . Fan et al 10 showed that Li doping-induced oxygen vacancies would benefit the adsorption of methyl radicals while suppressing the C−H decomposition.…”

Virtual Issue on Combustion Chemistry

“…11 In papers that extend beyond traditional notions of combustion, there are those that describe work on catalyzed combustion of methane 12 and toluene 13 and solid-state oxygen sources for chemical looping combustion. 14 Finally, three of the publications in this Virtual Issue take up the subject of nanoparticle-enhanced combustion, investigating Al nanoparticles 15,16 and Ni-CeO x hybrid nanoparticles. 17 Theoretical papers also cover many topics, ranging from accurate 18,19 and approximate 20 studies of molecular properties, interaction potential energy surfaces, 21−23 transition state theory calculations of rate coefficients, 24 and master equation simulations 25 to sensitivity of kinetic models.…”

“…In papers that extend beyond traditional notions of combustion, there are those that describe work on catalyzed combustion of methane and toluene and solid-state oxygen sources for chemical looping combustion . Finally, three of the publications in this Virtual Issue take up the subject of nanoparticle-enhanced combustion, investigating Al nanoparticles , and Ni-CeO x hybrid nanoparticles …”