Zhen Huang

Chemical looping combustion (CLC) is a promising technology for low-emission energy conversion because it enables the inherent separation of CO2 from the combustion products. However, contaminants released from complex fuels, including nitrogen, sulfur, chlorine, arsenic, and mercury-containing species, can induce the deactivation and poisoning of oxygen carriers (OCs), thereby compromising their long-term redox performance and hindering the practical deployment of CLC. This review critically examines the molecular-level interactions between representative pollutants and commonly investigated OCs by integrating insights from density functional theory calculations with relevant experimental observations. The principal poisoning pathways are identified as the occupation or blockage of redox-active sites, consumption or redistribution of lattice oxygen, formation of stable surface compounds, and pollutant-induced structural or phase transformations. Particular attention is given to the roles of oxygen vacancies, surface electronic structure, lattice oxygen mobility, and competitive adsorption in determining the reactivity and stability of OCs. On the basis of these mechanistic insights, three classes of strategies for developing poisoning-resistant OCs are summarized: structural engineering to establish physical and chemical barriers; compositional and doping modifications to regulate oxygen transport, defect chemistry, and pollutant adsorption; and the incorporation of competitive or sacrificial additives to mitigate multipollutant interactions. This Review provides a mechanistic framework for understanding pollutant-induced OC deactivation and offers guidance for the rational development of OCs with high redox activity, structural stability, and broad-spectrum resistance to poisoning.

The shale revolution has reshaped the global energy landscape, making ethane an efficient feedstock for ethylene production, which has created a market scarcity of higher α‐olefins, such as butene and hexene. Therefore, the ethylene oligomerization of abundant ethylene to produce higher α‐olefins offers significant advantages. However, substantial challenges remain in enhancing the product separation and catalyst recyclability during ethylene oligomerization. We propose a directed coordination strategy based on covalent organic framework (COF) structures, wherein metal active centers are precisely anchored to yield atomic‐level degrees of dispersion within the frameworks. This approach effectively avoids catalyst deactivation induced by aggregation while exposing a higher number of active sites. The highly dispersed single‐atom catalyst NPP@Ni exhibits an exceptional activity (10.96 × 10 ⁵ g/(mol Ni⋅h) ⁻¹ ) and a high selectivity toward hexene (>66.5%) across multiple catalytic cycles. The rational design of COF topologies enables the systematic regulation of the coordination environments and electronic structures of Ni sites. The catalytic performance and theoretical density functional theory calculations suggest that the coordination environment of Ni correlates directly with the selectivity toward α‐olefins. This study provides novel insights into the design of highly efficient and stable ethylene oligomerization catalysts.

Chemical looping technology utilizes the redox process and catalytic effects of metal oxides to convert carbon‐containing fuels and carbon dioxide into value‐added chemicals. Currently, cation diffusion, sintering, agglomeration, and the inactivation of metal oxides during cyclic redox reactions are the key challenges hindering the widespread industrialization of the chemical looping. While encapsulation strategies using supports have shown potential for prolonging redox catalyst lifespan, the fundamental mechanisms of support‐redox catalyst interactions and deactivation pathways under prolonged cycling remain elusive. In this study, the varying structural evolution pathways of redox catalysts from in situ transmission electron microscopy (TEM) indicate that the SiO ₂ shell can suppress Ostwald ripening during the reduction process through a confinement effect, thereby preventing the agglomeration of metal particles. Moreover, the activity‐related size‐dependent of Ni nanoparticles is elucidated through density functional theory (DFT) simulations. SiO ₂ support affects the migration path during the oxidation process. Finally, redox catalysts struggle to remain stably embedded within support or securely anchored on their surfaces. The continuous separation between Ni‐Fe and support may serve as a critical factor in deactivation in the long‐term. This study offers new insights into designing hierarchical redox catalysts with enhanced thermal and redox stability through in situ observation of the actual reaction process under high‐temperature.

In the process of fuel utilization, traditional combustion technologies result in the conversion of nitrogen elements in fuels into nitrogen oxides, which are released into the atmosphere, posing serious threats to the environment and human health. The chemical looping process (CLP) is an effective technology for reducing nitrogen-containing (N-containing) pollutants during fuel utilization. During the CLP, the oxygen carrier (OC) can oxidize nitrogen oxide precursors (NH₃ and HCN) released from the fuel to N₂, while the reduced OC can reduce nitrogen oxides to N₂. The achievement of efficient nitrogen pollutant removal relies on the development of highly active oxygen carriers (OCs). This review summarizes the recent progress in the removal of nitrogen pollutants within chemical looping processes (CLPs). It delineates the formation pathways of N-containing pollutants (NH₃, HCN, NO, NO₂ and N₂O) and highlights the performance of various OCs. The influence of reaction conditions and feedstock characteristics is also discussed. Ni-based OCs have demonstrated superior performance in the removal of N-containing pollutants, exhibiting strong oxidation capabilities and excellent catalytic properties. Moreover, iron ore, as a cost-effective and environmentally friendly feedstock, holds promise for wide-scale application. Future research should focus on further optimizing OCs strategies and refining reaction conditions to achieve more efficient and economical N-containing pollutant removal, thereby fostering the widespread application of chemical looping technology in the energy sector.

Traditional fossil energy sources still dominate the world energy structure. And fully utilizing biomass is a viable approach for energy transition. A bubbling fluidized bed has better heat and mass transfer, while particle agglomeration limits the development of its industrial application. In this paper, two-phase flow characteristics of a bubbling fluidized bed are investigated by combining numerical simulations and fluidized bed gasification experiments. Numerical simulations found that the bed fluidization height reached twice the initial fluidization height at the 0.054 m initial fluidization height with uniform particle distribution. Fluidized bed gasification experiments found that syngas yield increased with increasing temperature. The carbon conversion efficiency reached 79.3% and the effective gas production was 0.64 m³/kg at 850 °C. In addition, when the water vapor concentration reached 15%, the carbon conversion efficiency and effective gas production reached the maximum values of 86.01% and 0.81 m³/kg, respectively.