In coal-based chemical looping combustion (CLC) technology, relatively cheap metal oxides, referred to as oxygen carrier materials (OCMs), are required because some of the OCMs will be removed together with the residual ashes after combustion. CLC technology will have an estimated loss in efficiency of around 2% compared to standard combustion technology without capture if a proper OCM is found that can give full combustion, removing the need of an air separation unit (ASU). Materials with a chemical looping oxygen uncoupling (CLOU) effect will even give further benefits in faster gasification and combustion of the fuel. One can already find produced materials that can give such a desirable effect, but fabrication and material cost are still an issue in these cases. If such a material can be delivered by the mining industry, cost savings and plant efficiency will be high. Before selection of the natural minerals with strong inert inherent support that contain Fe and Mn, the need for a better understanding of the Fe−Mn system is needed. This pre-study combined with other literature findings of the Fe−Mn system shows that a Mn content of up to 25−33% will increase the CLOU effect, increase the conversion of CH 4 , and give possibilities for full combustion in a CLC plant.

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Redox stable SrFe 0.75 Mo 0.25 O 3-δ and SrFe 0.5 Mn 0.25 Mo 0.25 O 3-δ electrode materials were studied in terms of their physicochemical properties and electrochemical performance in symmetrical SOFCs, with focus on their tolerance toward carbon deposition and sulfur poisoning. Both materials possess cubic, B-site cation-disordered Pm-3m structure in air up to high temperatures. SrFe 0.5 Mn 0.25 Mo 0.25 O 3-δ was found to transform to a B-site cation-ordered structure after reduction in dry 5 vol% H 2 /Ar at 1100 • C, while no structural changes were observed for SrFe 0.75 Mo 0.25 O 3-δ . Weight change upon annealing up to 850 • C in air and in dry 5 vol% H 2 /Ar indicated an increase in oxygen deficiency on the order of δ = 0.2. Seebeck coefficient and conductivity dependence on the oxygen partial pressure pO 2 showed that both oxides exhibit p-type conductivity in air and n-type conductivity under reducing conditions. Carbon deposition was found to depend on temperature, gas composition (CO or CH 4 ), and presence of Ce 0.8 Gd 0.2 O 1.9 electrolyte in the composite-type electrode. Stable fuel cell performance, without carbon deposition, was obtained for SrFe 0.75 Mo 0.25 O 3-δ -based SOFC in 10 vol% of CO in CO 2 . Also, SOFC operation with CH 4 as fuel was achieved without coking at temperatures ≤ 700 • C. However, both oxides suffer from sulfur poisoning-related effects in atmosphere with 800 ppm H 2 S. Compatibility of Solid Oxide Fuel Cells (SOFCs) with nonhydrogen fuels represents their important advantage over other types of fuel cells. Versatile fuel utilization can be an essential factor for future development and commercial adoption of SOFC technology in power generation, for instance, from biogas used as a renewable energy source.1,2 One of the main challenges with SOFCs running directly on carbon containing fuels, such as syngas, methane/biogas or other hydrocarbons, is carbon deposition occurring on the anode, which results in a significant, and sometimes detrimental decrease of the performance. In the case of well-established Ni-YSZ cermet anode, the performance degradation upon coking arises mainly from a decrease in length of the Triple Phase Boundary (TPB) on the anode, which limits the number of catalytic sites needed for fuel oxidation.1,2 Furthermore, the deposited carbon may expand and destroy mechanical integrity of the electrode. Also, the considered nonhydrogen fuels usually contain sulfur (in a form of H 2 S), which can irreversibly poison Ni-YSZ cermet anodes.1-3 It may be stated that construction of robust SOFCs with fuel versatility relies upon a development of the anode materials with improved tolerance towards carbon deposition and sulfur poisoning. Mo-containing perovskitetype oxides have shown promise in this respect.3,4 The considered family of materials possesses crystal structure that can be either B-site cation disordered, denoted as AM 1-x Mo x O 3-δ (A: Sr, Ba; M: 3d metals) or B-site cation-ordered one (so called double perovskite structure), A 2 M 2-x Mo x O 6-δ . 3,5 T...

Power generation using chemical looping combustion (CLC) technology has emerged as a promising CO 2 -capture-based alternative to conventional technology. In this study, the performance of a Ca 0.9 Mn 0.5 Ti 0.5 O 3−δ perovskite-type oxygen carrier material for use in fixed-bed CLC reactors is investigated. The main focus of the study is on the material's oxygencarrying capacity and reactivity with and conversion of syngas in the fixed-bed reactor. Pressurized thermogravimetric analysis in model gases indicates neither Boudouard coking nor reactivity of the oxygen-carrier material toward CO 2 . A fuel gas conversion of 95% was achieved in the fixed-bed reactor using this oxygen-carrier material.