Reaction Kinetics in Chemical Looping Processes

Dear Colleagues,

I am pleased to invite you to submit a manuscript to this Special Issue of Fire, titled “Reaction Kinetics in Chemical Looping Processes”.

Chemical looping processes are based on splitting a chemical process into two or more steps in a cyclic way. Typically, an active material is used as a carrier that connects the different stages of the chemical looping process. In the beginning, chemical looping was proposed as an advanced combustion process with the potential to increase energy efficiency in the thermochemical conversion of fuels using the principles of thermodynamics to reduce exergy loss. Thus, an oxygen carrier was used to split the combustion process into two stages. Thus, Chemical Looping Combustion (CLC) was characterized by obtaining a CO₂ stream separated from the depleted air used for fuel combustion. Due to this, CLC was shown to be one of the most promising technologies for combustion with CO₂ capture at low energy and economic costs. However, the development of chemical looping technology has been extended to diverse processes for multiple purposes. These processes may be based on the transference of one atom or compound for fuel oxidation, reducing a compound, gas separation, chemical synthesis, or circumvent thermochemical equilibrium limitations in chemical reactions.

This Special Issue aims to disseminate new and relevant research in a unique publication on the kinetics of reactions involved in different chemical looping processes, including, but not limited to, the following:

• Combustion for energy production: An oxygen carrier transport oxygen from air to fuel for its combustion. Processes include Chemical Looping Combustion (CLC) and Chemical Looping with Oxygen Uncoupling (CLOU).
• Syngas production: An oxygen carrier provides oxygen for the partial oxidation of a fuel to produce syngas. Chemical Looping Reforming (CLR) is focused on gaseous or liquid fuels, while solid fuels are used in Chemical Looping Gasification (CLG).
• CO₂ separation: A CO₂ carrier is used to separate CO₂ from a gaseous stream. Calcium carbonate has been extensively studied for this process in so-called Calcium Looping (CaL), but other CO₂ carriers may be used, including lithium orthosilicates or sodium zirconates.
• Hydrogen production: A water splitting reaction is integrated in the chemical loop to produce hydrogen by the partial oxidation of the oxygen carrier by H₂ Several configurations have been proposed, which may be described as Chemical Looping with Water Splitting (CLWS) processes. A concentrated H₂ stream is also the purpose of so-called sorption enhanced chemical looping reforming (SE-CLR) or gasification (SE-CLG) processes, where bi-functional oxygen and CO₂ carriers are used.
• CO₂ use: In chemical looping with CO₂ splitting (CLCO₂S), CO is produced by the CO₂ splitting reaction assisted by an oxygen carrier.
• Ammonia production: Nitrogen carriers are used to produce ammonia more efficiently than the traditional Haber–Bosch process.
• Circumvent limitations of thermodynamic equilibrium: Eliminating one product of the reaction, such as steam in sorption enhanced methanation (SEM) or selective hydrogen oxidation in oxidative de-hydrogenation reactions.
• Gas purification: Including processes in which a chemical loop may be used for selective oxidation of one compound in a gas mixture, or the avoidance of harmful emissions, e.g., in ventilation air methane.

• Theoretical studies, such as those based on density functional theory (DFT) or focused on unrevealing reaction mechanisms and the experimental determination of reaction kinetics involving oxygen, CO₂, water, or nitrogen carriers, such as:
• Reduction and oxidation reactions of oxygen carriers for CLC, CLOU, CLR, and CLG.
• Kinetics of catalytic reactions supported by oxygen carriers.
• Carbonation/calcination reactions of CO₂
• Splitting reactions with an oxygen carrier and H₂O or CO₂.
• Nitrogen reaction with nitrogen carriers or N-carrier reaction to form ammonia.
• Kinetics involved in fuel conversion in chemical looping processes.

I look forward to receiving your contributions.

Dr. Alberto Abad Secades
Guest Editor

Manuscript Submission Information

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• chemical looping
• kinetics
• oxygen carrier
• CO₂ carrier
• nitrogen carrier
• combustion
• reforming
• gasification
• ammonia
• CO₂ capture