Figure 1 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Source publication
The objective of the research was to prepare Fe-based materials for use as oxygen carriers (OCs) and investigate their reactivity in terms of their applicability to energy systems. The performance of ZrO2 supported Fe-Mn oxide oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was ana...
Contexts in source publication
Context 1
... this reason, CLC is believed to be an innovative technology that may be a solution for the mentioned energy penalty problem [1][2][3]. In essence, the CLC system is usually composed of two fluidized bed reactors, as shown in Figure 1. One of them is a fuel reactor, where fuel reacts with an oxygen carrier, usually made of a metal oxide, to produce CO2 and H2O (Equation (1)). ...
Context 2
... Moreover, the chemical microanalysis data show that Fe-Mn-Zr oxides obtained in this work display homogenous dispersion of the elements, as assumed. This proves the good quality of the OCs, since the dispersion of the Fe, Mn, Zr, and O of the scanned areas in samples was very good, which was shown in Figures 9 and 10. The element mapping for the fresh F50Mn30Zr20 (Figure 9) sample supports the presence of porous manganese ferrite and the spots of ZrO2, as previously observed in diffractograms. ...
Context 3
... element mapping for the fresh F50Mn30Zr20 (Figure 9) sample supports the presence of porous manganese ferrite and the spots of ZrO2, as previously observed in diffractograms. Furthermore, the morphology and texture of doped and undoped samples differs, for example, Figure 10 shows that F80 sample particles are more porous and irregular compared to doped materials. The XRD analyses of spent oxygen carriers (Figure 2) showed that their crystal structures have not changed significantly after cycling reactions carried out under high temperature (800-1000 °C) for about 25 h of experiments. ...
Context 4
... some morphology changes were detected during the examination of spent materials. Figure 11 shows both scanning electron microscope photomicrographs with element mapping for the sample first reacted with fuel and then with regenerated F65Mn15, while Figure 12 displays reference F80 OC. The SEM analysis proved that in the spent materials a type of shell was formed on the external surface of the OC granule. ...
Context 5
... some morphology changes were detected during the examination of spent materials. Figure 11 shows both scanning electron microscope photomicrographs with element mapping for the sample first reacted with fuel and then with regenerated F65Mn15, while Figure 12 displays reference F80 OC. The SEM analysis proved that in the spent materials a type of shell was formed on the external surface of the OC granule. ...
Context 6
... to manganese, the doped samples were used as the reference material. Figure 12 shows scanning electron microscope photomicrographs with element mapping for F80 sample reacted and subsequently regenerated with air. It is clear that both oxygen and iron are uniformly broadcasted on the internal and external surface of the granule, which is attributed to Fe2O3, while zirconia is rather outside, and seems to be separate small grains. ...
Citations
... This can be achieved by introducing functiona groups or molecules onto the catalyst surface, which can alter its electronic properties an promote the desired reactions [76]. Surface modification can also improve the stability o catalysts by providing a protective layer against degradation [77]. For example, Zhang e al. [78] developed a room-temperature synthesis to produce gelled oxyhydroxide materi als with an atomically homogeneous metal distribution (see Figure 5). ...
... This can be achieved by introducing functional groups or molecules onto the catalyst surface, which can alter its electronic properties and promote the desired reactions [76]. Surface modification can also improve the stability of catalysts by providing a protective layer against degradation [77]. For example, Zhang et al. [78] developed a room-temperature synthesis to produce gelled oxyhydroxide materials with an atomically homogeneous metal distribution (see Figure 5). ...
Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field.
... 45,46 The inactivation of Mn-rich spinels was shown in our previous works. 47,48 To improve the quality of OCs, the addition of an inert/support such as ZrO 2 , TiO 2 , Al 2 O 3, kaolin or sepiolite is frequently used. 27,49 Inerts generally improve long-term mechanical stability and prevent agglomeration tendency, but some also may improve chemical performance. ...
... 27 Successful examples of mixed Fe-Mn with Al 2 O 3 or ZrO 2 for combustion of both gaseous and solid fuels have been documented in the literature to date. 42,[45][46][47][48][50][51] The proper choice of supporting materials depends on the possible presence of side reactions between the active and supporting phases. For example, an unfavourable reaction may occur for SiO 2 , forming unreactive Fe 2 SiO 4 and leading to deactivation of the OC. ...
In this paper five bimetallic Fe2O3‐MnO2 oxygen carriers supported on TiO2 were evaluated for direct hard coal combustion via chemical looping path. The oxygen carriers were obtained via mechanical mixing and high‐temperature calcination. The samples contained varying amounts of Fe2O3 (20–50 wt.%) and MnO2 (65–30 wt.%) but an identical amount of inert material (15 wt.%). Both the impact of the oxygen carrier's composition and the process temperature on their reactivity with the selected hard coal were evaluated. The amount of manganese in the oxygen carriers correlated positively with their reactivity toward the fuel. It was concluded that after eight reaction cycles the oxygen carriers remained resilient for side reactions with the ash residue. Thus, the physicochemical stability of the presented oxygen carriers was proved. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.
... The reactivity and stability of the oxygen carrier are critical for the CLOU process applicability [7]. Many materials appropriate for CLOU have been studied to date, including perovskite-type oxides [8], natural ores [9], synthetic materials [10], and transitional metal oxides [11]. As a consequence of advanced research, transitional metal oxides in a variety of forms, such as nickel, cobalt, iron, manganese, or copper oxides, were confirmed as potential candidates for oxygen carriers [11][12][13][14][15][16]. ...
... Many materials appropriate for CLOU have been studied to date, including perovskite-type oxides [8], natural ores [9], synthetic materials [10], and transitional metal oxides [11]. As a consequence of advanced research, transitional metal oxides in a variety of forms, such as nickel, cobalt, iron, manganese, or copper oxides, were confirmed as potential candidates for oxygen carriers [11][12][13][14][15][16]. Among these metal complexes, copper-based oxygen carriers are appealing due to their high reactivity, high oxygen capacity, and environmental friendliness [17]. ...
The Cu-based oxygen carrier is a promising material in the chemical looping with oxygen uncoupling (CLOU) process, while its performance in the CLOU is significantly dependent on the oxygen release properties. However, the study of oxygen release mechanisms in CLOU is not comprehensive enough. In this work, the detailed oxygen release mechanisms of CuO(110) and CuO(111) are researched at an atomic level using the density functional theory (DFT) method, including the formation of O2, the desorption of O2 and the diffusion of O anion, as well as the analysis of the density of states. The results show that (1) the most favorable pathway for O2 formation and desorption occurs on the CuO(110) surface of O-terminated with energy barriers of 1.89 eV and 3.22 eV, respectively; (2) the most favorable pathway for O anion diffusion occurs in the CuO(110) slab with the lowest energy barrier of 0.24 eV; and (3) the total density of states for the O atoms in the CuO(110) slab shifts to a lower energy after an O vacancy formation. All of the above results clearly demonstrate that the CuO(110) surface plays a significantly important role in the oxygen release reaction, and the oxygen vacancy defect should be conducive to the reactivity of oxygen release in a Cu-based oxygen carrier.
... Lack of direct contact between fuel and atmospheric nitrogen limits the creation of thermal NO x ; therefore, the fumes coming from this process contain mostly H 2 O and CO 2 [5]. CLC technology could be applied for the combustion of a large variety of fuels such as solids (hard coal [7], lignite, biomass [8][9][10], liquid [11] or gaseous (syngas, natural gas, methane or hydrogen etc.) [12][13][14]. ...
... TiO 2 were synthesized by mechanical mixing and calcination. Their CLC properties were tested with the application of model gaseous fuel 4% H 2 and thermogravimetric analyzer period, The aim of this work is to broaden our knowledge of bimetallic Fe-Mn OCs and natural continuation of our research on supported low cost oxygen carriers with CLC and CLOU properties [14]. Hydrogen is an environmentally friendly energy carrier derived from biomass or coal [32]. ...
... For the reference sample, the X-ray diffraction peaks can be attributed to the presence of hausmannite (Mn 3 O 4 ) and manganese titanate (MnTiO 3 ), since the manganese (III) oxide, observed in the fresh samples, completely transformed into hausmannite. The presence of iwakiite in manganese-rich samples and bixbyite to spinel transition in reacted Fe-Mn OC systems were also reported in our previous works [7,14]. ...
The objective of the research was to prepare Mn-based materials for use as oxygen carriers and investigate their reactivity in terms of their applicability to energy systems. The family of Fe2O3-MnO2 with the addition of TiO2 was prepared by mechanical mixing method and calcination. Five samples with addition of Fe2O3 (20, 30, 35, and 50 wt.%) to MnO2 (65, 55, 50, 35, and 85 wt.%) with constant amount of inert TiO2 (15 wt.%) were prepared. The performance of TiO2 supported Fe-Mn oxides oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was evaluated. Thermogravimetric analysis was used for reactivity studies within a wide temperature range (800–1000 °C). Comprehensive characterization contained multipurpose techniques for newly synthesized materials. Moreover, post-reaction experiments considered morphology analysis by SEM, mechanical strength testing by dynamometry, and crystal phase study by XRD. Based on wide-ranging testing, the F50M35 sample was indicated as the most promising for gaseous fuel combustion via CLC at 850–900 °C temperature.
... The parameter is important for the application of OCs materials in industrial scale CLC plant, and may be tailored by increasing the lifespan of OC [4]. Also, ZrO 2 as an inert material does not negative effect on the reactivity of Fe-Mn based materials [14,20]. As was stated earlier [13,18], OCs that exhibit CLOU properties show better performance during reaction with coal. ...
... As was stated earlier [13,18], OCs that exhibit CLOU properties show better performance during reaction with coal. Fe-Mn OCs were successfully tested as an effective and promising materials for hydrogen combustion, which was reported in paper [14]. ...
... To explain that phenomenon additional work was carried out. Based on FactSage thermodynamic calculations, it was predicted that spinel will be formed instead of bixbyite when the partial pressure of O 2 will decrease, together with increase of temperature [13,14]. To prove possible negative impact of some spinel formation on oxygen carrier reactivity, which was reported previously [11,17], two different Fe:Mn spinels with ratio of 1:2 and 2:1 were additionally synthesized. ...
This paper contains the results of research on a promising combustion technology known as chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU). The remarkable advantages of CLC are, among others, that concentrated CO2 stream can be obtained after water condensation without any energy penalty for its separation or significant decrease of NOx emissions. The objective of this work was to prepare a novel bi-metallic Fe–Mn supported on ZrO2 oxygen carriers. Performance of these carriers for the CLOU and CLC process with nitrogen/air and hard coal/air was evaluated. One-cycle CLC tests were conducted with supported Fe–Mn oxygen carriers in thermogravimetric analyzer utilizing hard coal as a fuel. The effects of the oxygen carrier chemical composition and process temperature on the reaction rates were determined. Our study proved that for CLOU, properties formation of bixbyite and spinel forms are responsible. Among iron ferrites, we concluded that iron-rich compounds such as Fe2MnO4 over FeMn2O4 spinel type oxides are more effective for CLOU applications.
Ni-based oxygen carriers (OCs) are considered promising materials in the chemical looping combustion (CLC) process. However, the reactivity of Ni-based OCs still offers the potential for further enhancement. In this work, the Li doping method has been employed for the modification of Ni-based OCs. The reactivity and microreaction mechanisms of different concentrations of Li-doped Ni-based OCs with CO in CLC are clarified using density functional theory (DFT) simulation. The structures, energy, and density of states are obtained through computational investigation of the reaction path in elementary reactions. The results show that (1) the adsorption energies of CO molecules on NiO surfaces with 4, 8, and 12% Li doping concentrations are −0.53, −0.48, and −0.54 eV, respectively, demonstrating an enhanced reactivity compared to that of pure NiO (−0.41 eV); (2) the calculation of the transition state indicates that the most favorable pathway for CO oxidation takes place on the surface of NiO with an 8% Li doping concentration, exhibiting the lowest energy barrier of 0.51 eV; and (3) the oxygen vacancy formation energies on the surface of NiO are 3.05, 2.30, and 2.10 eV for 4, 8, and 12% doping concentrations, respectively. Additionally, the decrease in oxygen vacancy formation energies exhibits a gradual decline with an increasing Li doping concentration. By comprehensive analysis, 8% is considered to be the optimal doping concentration of NiO for chemical looping combustion.
