Natural gas (NG) production in Brazil has shown a significant increase in recent years. Oil and natural gas exploration and refining activities indicate circa 86% carbon dioxide content in NG, representing a serious problem for environmental issues related to greenhouse gas emissions and increases in global warming. New technologies using CO₂ capture materials have been shown to be more efficient than conventional processes. In this work, a bimodal meso–macroporous silica adsorbent for CO₂ adsorption in NG was synthesized and evaluated as a promising material for use in natural gas treatment systems, as silica has specific textural properties that facilitate the capture and storage of this gas. The adsorbent was obtained from silica via the hydrothermal method with n-dodecane emulsion and characterized by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and the BET specific surface area. Adsorption capacity tests were performed for CO₂, methane, and their mixtures by the gravimetric method, demonstrating that the adsorbent was selective for CO₂ and obtained a good adsorption capacity. The experimental values obtained were compared and adjusted to the models of Langmuir and Freundlich. Thus, the bimodal silica adsorbent developed in this research proved to be excellent for CO₂ adsorption and is a promising material for the treatment of NG.

This work aimed to study nickel-based oxygen carriers (OC) for Chemical Looping Combustion (CLC) using H2 and CH4 as fuel. The reactivity and reaction kinetics of the OC were investigated, applying the shrinking core, nucleation and diffusion models in three dimensions, as well as whether the OC is thermodynamically favorable for the reaction. The results showed that the OC achieved high conversion for both fuels, proving to be quite reactive, while the fuel gas concentration and the temperature have a strong effect on the solids conversion. For the H2 combustion, the reaction rate can be described well by the shrinking core model, whereas for CH4 the nucleation model may better represent the experimental data. With respect to reactions that occur in the reduction reactor with the NiO/Ni redox system, it was observed that, for the investigated temperatures used in CLC, high values of the equilibrium constant were obtained, showing that practically complete conversion of the fuels is possible.

Chemical looping combustion (CLC) processes have been shown to be promising and effective in reducing CO2 production from the combustion of various fuels associated with the growing global demand for energy, as it promotes indirect fuel combustion through solid oxygen carriers (SOC). Thus, this study aims to synthesize, characterize and evaluate mixed copper and titanium oxide as a solid oxygen carrier for use in combustion processes with chemical looping. The SOC was synthesized based on stoichiometric calculations by the polymeric precursor method and characterized by: X-ray fluorescence (XRF), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-FEG) with EDS, and Programmed Temperature Reduction (PTR). The oxygen carrying capacity (ROC) and the speed index of the reduction and oxidation cycles were evaluated by Thermogravimetric Reactivity (TGA). The main reactive phase identified was: The CuO phase for the mixed copper and titanium oxide were identified and confirmed by X-ray diffraction using the Rietveld refinement method. The reactivity of the CuO-TiO2 system was high, obtaining a CH4 conversion rate above 90% and a speed index of 40%/min. Due to the structural characteristics and the reactivity tests of this material, it is concluded that mixed copper and titanium oxide have the necessary requirements to be used in chemical looping combustion (CLC) processes.