Analysis of the role of Cu for improving the reactivity of Cu-modified Fe2O3 oxygen carriers in the chemical looping gasification process with coal. (1st December 2021)

• Record Type: Journal Article
• Authors: An, Mei; Yuan, Nini; Guo, Qingjie
• Is Part Of: Fuel. Volume 305(2021)
• Publication Date: 2021-12-01
• Subjects: CuO -- Fe2O3 -- Density functional theory -- Reaction mechanism -- Reaction pathway -- Reaction energy barrier; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2021.121619
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Mechanisms of the addition of CuO enhanced activity with H2 were studied using DFT. The roles of synergy in CLG were analyzed by theory and experiments. CuxFe3-x O4 is the key to the synergy of Cu modified Fe2 O3. Changing the reaction path is the root cause of improving the reactive of Fe2 O3 after adding CuO. Abstract: The design and optimization of high-performance oxygen carriers (OCs) are the key to the industrialization of chemical looping gasification processes. The addition of Cu to Fe-based OCs has been demonstrated to improve their reaction performance. However, the operative mechanisms behind this improvement, which must be understood for making accurate predictions and designing optimum Fe-Cu composite OCs, remain poorly understood. The present work addresses this issue by systematically investigating the gasification reactivity of Cu-modified Fe2 O3 OCs with molar ratios of CuO/Fe2O3 in the range of 0.2–1.8 fabricated by mechanical mixing and calcination. The obtained Cu-modified Fe2 O3 OCs are characterized by an array of methods, and employed in a fluidized bed reactor for conducting chemical looping gasification experiments with coal. The results indicate that the replacement of Fe with Cu atoms in the Fe2 O3 lattice, resulting in the formation of Cu x Fe3- x O4, is the key feature in the improved reaction performance of Cu-modified Fe2 O3 OCs. The effect of introducing Cu into the Fe2 O3 OCs on the H2 -OC reduction reaction is analyzed computationally from a molecular perspective based on density functional theory. The introduction of Cu is thereby demonstrated to improve the reactivity of Fe2 O3 fundamentally by altering the reaction pathway of Fe2 O3 and decreasing the reaction energy barrier between H2 molecules and the OC. This understanding of the mechanisms by which Cu affects the reactivity of Cu-modified Fe2 O3 OCs provides significant support for the controllable preparation of highly active OCs, and thereby facilitates the industrial development of chemical looping gasification processes.