Advanced Chemical Looping Materials for CO2 Utilization: A Review

Abstract

Combining chemical looping with a traditional fuel conversion process yields a promising technology for low-CO2-emission energy production. Bridged by the cyclic transformation of a looping material (CO2 carrier or oxygen carrier), a chemical looping process is divided into two spatially or temporally separated half-cycles. Firstly, the oxygen carrier material is reduced by fuel, producing power or chemicals. Then, the material is regenerated by an oxidizer. In chemical looping combustion, a separation-ready CO2 stream is produced, which significantly improves the CO2 capture efficiency. In chemical looping reforming, CO2 can be used as an oxidizer, resulting in a novel approach for efficient CO2 utilization through reduction to CO. Recently, the novel process of catalyst-assisted chemical looping was proposed, aiming at maximized CO2 utilization via the achievement of deep reduction of the oxygen carrier in the first half-cycle. It makes use of a bifunctional looping material that combines both catalytic function for efficient fuel conversion and oxygen storage function for redox cycling. For all of these chemical looping technologies, the choice of looping materials is crucial for their industrial application. Therefore, current research is focused on the development of a suitable looping material, which is required to have high redox activity and stability, and good economic and environmental performance. In this review, a series of commonly used metal oxide-based materials are firstly compared as looping material from an industrial-application perspective. The recent advances in the enhancement of the activity and stability of looping materials are discussed. The focus then proceeds to new findings in the development of the bifunctional looping materials employed in the emerging catalyst-assisted chemical looping technology. Among these, the design of core-shell structured Ni-Fe bifunctional nanomaterials shows great potential for catalyst-assisted chemical looping.

Hydrogen‐rich syngas production from chemical looping steam reforming of bio‐oil model compound: Effect of bimetal on LaNi 0.8 M 0.2 O 3 (M = Fe, Co, Cu, and Mn)

“…The characteristic of Co‐based is similar to Ni‐based while it exhibits minor resistance to agglomeration. Fe‐based is one of the normal metals, and its characteristic, such as environment‐friendly, abundant, and creaking of C―C bond, was focused . On the other hand, it shows poor reactivity and weak reducibility .…”

“…Also, the characteristics of Mn‐based and Cu‐based are similar with Fe‐based. Compared with Fe‐based, Cu‐based easily creaks the C―H bond, while the Mn‐based is easily poisoned by sulfur …”

“…Fe-based is one of the normal metals, and its characteristic, such as environment-friendly, abundant, and creaking of C-C bond, was focused. 21,22 On the other hand, it shows poor reactivity and weak reducibility. 23 Also, the characteristics of Mn-based and Cu-based are similar with Fe-based.…”

“…Compared with Febased, Cu-based easily creaks the C-H bond, while the Mn-based is easily poisoned by sulfur. 21 The deactivation of active sites was a main problem in the process of acetic acid production hydrogen, such as formation of coke deposition and active metal sintering. Deactivation can resist by raising oxygen content from water, support, and oxygen, enhancing the dispersion of catalyst.…”

Catalyst Deactivation, Poisoning and Regeneration

“…Not surprisingly, there is considerable motivation to understand and treat catalyst deactivation, poisoning and regeneration, which causes this research topic to continue to grow [1]. The complexity of catalyst poisoning obviously increases along with the increasing use of biomass/waste-derived/residual feedstocks [2,3] and with requirements for cleaner and novel sustainable processes, such as those implementing a catalytic assisted chemical looping approach [4,5].This Special Issue provides insight for several specific scientific and technical aspects of catalyst poisoning and deactivation, proposing more tolerant catalyst formulations and exploring possible regeneration strategies. In particular, 14 research articles focus on heterogeneous catalysts by investigating thermal [6-8], physical [9,10] and chemical [11][12][13][14][15][16][17][18][19] deactivation phenomena, and also exploring less conventional poisons related to the increasing use of bio-fuels [17].…”