(380p) Exploring Particle Modification Strategies to Improve Yields for Oxidative Coupling of Methane in a Chemical Looping System

Direct valorization of methane to value added products is a challenging and highly sought-after technology. Oxidative coupling of methane (OCM) is one such attractive technology, where methane molecules under the presence of an oxygen species, couple to form ethylene and water. Chemical looping oxidative coupling of methane (CL-OCM) provides this oxygen via lattice oxygen from a catalytic oxygen carrier (COC). CL-OCM has several advantages over the traditional OCM and thus is the focus of this study. Detailed energy analysis has been performed previously on the CL-OCM process over a proprietary Mg₆MnO₈ based COC, which gave a hydrocarbon yield of 23.2%. The objective of this study is to intuitively develop COCs which can achieve high yields in OCM by modifying the base COC.

The particle modifications are carried out using density functional theory (DFT) calculations, which would help in the screening of different metal oxide dopants that can increase the OCM hydrocarbon yield. These results have been coupled with experimental verification to develop an optimal COC configuration. Thermogravimetric analysis (TGA) has been used to investigate the reactivity of these COC’s under methane reduction. These results have been combined with fixed bed tests of the COCs, which provide gas-composition data as the reduction proceeds. A Fourier transform infrared (FTIR) gas analyzer along with a gas chromatography analyzer has been used for this purpose. Parametric studies have been carried out to find the optimal reaction temperature and space velocity to obtain the highest hydrocarbon yield. Additionally, the recyclability of the modified COC has also been tested for 50 redox cycles. Solid characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscope (SEM) were used to understand the changes in the solid phase. Results from this study provide key insights into the development of such COCs for CL-OCM technology.