## 1 Introduction  
The main contributors to global warming are power plants through the emission of greenhouse gases, especially CO\({}_{2}\), from the combustion of fossil fuels [1]. Recently, in the 21 st United Nations conference on climate change (COP21), 195 countries attended with the aim of curbing CO\({}_{2}\) emissions in the atmosphere [2]. Several options are needed in order to minimize these medium-term emissions, including CO\({}_{2}\) capture and storage [3; 4; 5]. In this context, chemical looping combustion (CLC) is a promising technology to capture CO\({}_{2}\) at low economic and energy cost [6]. CLC is an advanced combustion technology which inherently separates CO\({}_{2}\). It includes the use of a metal oxide as an oxygen carrier (OC), which transfers oxygen to the fuel during combustion; therefore, direct contact between the fuel and the air is avoided. The most commonly proposed configuration is two interconnected fluidized bed reactors. The reduction reactor, in which the metal oxide is reduced upon reaction with the fuel and the oxidation reactor and where the reduced metal oxide is oxidized with air [7; 8; 9], has an outlet stream consisting of CO\({}_{2}\) and H\({}_{2}\)O, while the output stream from the oxidation reactor contains N\({}_{2}\) and O\({}_{2}\)[10]. The net chemical reaction over the two reactors is the same as that in normal combustion with the same amount of heat released, but with an important difference: the carbon dioxide is inherently separated from the nitrogen, and no extra energy is required for this separation [6; 10]. The review carried out by [PERSON] et al. [6] shows that studies carried out so far have synthesized more than 700 oxygen carriers, obtaining materials with promising characteristics in terms of reactivity and stability [11]. However, due to the high cost of synthetic materials, it would be less expensive to use minerals in their natural form or industrial waste. This would be very promising for use with solid and gaseous fuels [12; 13; 14; 15; 16; 17; 18; 19; 20; 21]. In several areas of Colombia, metal oxides can be found in their natural form or as waste from industries and mining, which could be used in the implementation of CLC technology, or even in in situ gasification with CLC (iG-CLC) [22; 23]. In the literature, chromite is the least studied material for use as an oxygen carrier. In Colombia, there are reports of chromite mineralization east of Medellin (deposits in Santa Elena); around Ituango, Yarumal, and Serrania de Baudo; and in the upper part of the Guapi river [24]. Ilmenite is an attractive low-cost material that could be used as an OC because it has a high CO conversion rate and a moderate CH\({}_{4}\) conversion rate [25]. Although the pre-oxidized and activated ilmenite initially presented low reactivity, after several redox cycles, it undergoes an activation process that increases its porosity and reactivity, notably when using H\({}_{2}\), CO, and CH\({}_{4}\) as fuels [6; 26]. However, the segregation of Fe from TiO\({}_{2}\), causes the oxygen transport capacity to decrease after 100 redox cycles when solid fuel is used [27; 28]. From the reduced ilmenite form (FeTiO\({}_{3}\)) and the oxidized form (Fe\({}_{2}\)TiO\({}_{5}\) + TiO\({}_{2}\)), the reduction/oxidation of ilmenite is carried out. The probable intermediate phases of the reaction are Fe\({}_{2}\)O\({}_{3}\), Fe\({}_{2}\)O\({}_{3}\).TiO\({}_{2}\), though this does not totally exclude the presence of other intermediate stages [25]. Due to their low cost and environmental compatibility, iron-based carriers are considered an attractive option for applications with CLC technology [29], despite their weak redox characteristics, such as low methane conversion and low oxygen transport capacity [30]. In these carriers, different states of oxidation can be found when Fe\({}_{2}\)O\({}_{3}\) is reduced to Fe\({}_{3}\)O\({}_{4}\), FeO, or Fe.