To achieve net-zero CO₂ emissions over the coming decades, innovative new technologies, including separation, storage, and utilization of CO₂, are indispensable. Chemical looping technology may provide effective solutions and promising energy conversion systems for power plants and industrial applications with inherent CO₂ capture, avoiding energy penalties. Combined with appropriate CO₂ storage and utilization options, chemical looping can achieve net-zero emissions. The challenges, benefits, and prospects of chemical looping systems with various oxygen carriers and reactor configurations are discussed in this review to provide insights into the development of innovative systems in terms of solid looping materials, reactions, systems, and economics.

Bimetallic alloys are widely used and studied as catalyst materials, but development of highly efficient catalysts using only two metal elements has limits. In this study, a series of multimetallic catalysts were developed for deNO_x reactions and alkane dehydrogenation based on advanced catalyst design concepts using alloy materials. Two strategies based on pseudo-binary alloys and surface modification of intermetallic compounds were employed. Pseudo-binary alloy, in which a part of the constituent metal in a binary intermetallic compound is substituted with a third metal, allows construction of trimetallic active sites with flexibly optimized atomic ratio and catalytic characteristics. Surface modification of intermetallic compounds allows selective blocking of undesirable active sites catalyzing side reactions, and construction of a sterically hindered reaction environment for selective hydrogenation. High catalytic activity, selectivity, and stability were achieved by appropriately applying these materials and design concepts. Outstandingly high stability (almost no deactivation at 600 °C for a month) was achieved for propane dehydrogenation.

A series of CoMo/Al₂O₃ catalysts with various Co/Mo mole ratios and a series of CoMo/TiO₂–Al₂O₃ catalysts supported on TiO₂ coating Al₂O₃ were prepared. The effects of Co/Mo mole ratio and TiO₂ loadings on Al₂O₃ on hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DCO) in the hydrotreating of palm fatty acid distillate (PFAD) were investigated. The catalysts were characterized by BET, XRF, pulse NO chemisorption, and H₂-TPR. The maximum yields of n-C₁₆ and n-C₁₈ was observed at Co/Mo = 0.05 for the CoMo/Al₂O₃ series, and the yield of n-C₁₅ and n-C₁₇ was increased at Co/Mo > 0.05. CoMoS phase apparently has both HDO and DCO activities. CoMo(0.05)/Ti(20)–Al showed the maximum yields of n-C₁₆ and n-C₁₈ due to the formation of TiMoS in all catalysts. TiMoS phase may be formed by adding TiO₂ on Al₂O₃ and promotes the HDO reaction, but not isomerization or cracking.

ZnZSM-5 metal oxide hierarchical composite catalysts were made using Zn-exchanged ZSM-5 and various oxides by the conventional kneading method. The effects of these oxides as matrices on the activity and selectivity for aromatics in cracking and dehydrocyclization of n-pentane were investigated. ZnZSM-5 50-85 wt% was mixed with oxide 0-35 wt% and alumina-sol binder 15 wt% using the kneading method. Al₂O₃ (A), TiO₂ (T), ZrO₂ (Zr) and kaolin (ka) were used as the oxide. Cracking and successive dehydrocyclization of n-pentane was carried out in a fixed-bed reactor under atmospheric H₂ in the range 450-550 °C. Conversions of n-pentane at 550 °C decreased in the order ZnZSM/0A (85 wt% ZnZSM-5, 0 wt% Al₂O₃, 15 wt% binder) ≥ ZnZSM/10A > ZnZSM/10T > ZnZSM/10Zr > ZnZSM/10ka ≥ ZnZSM/35A. The selectivity for aromatics at 550 °C decreased in the order ZnZSM/10A > ZnZSM/0A > ZnZSM/10Zr = ZnZSM/10T = ZnZSM/10ka > ZnZSM/35A. These results suggested that the use of both ZnZSM-5 and matrix with large porosity for this reaction would optimize the catalytic functions. The product distribution indicated that aromatization of olefins to benzene, toluene, and xylene occurred through the Diels-Alder reaction on Zn species in the ZSM-5.