(439b) High Purity Syngas and Hydrogen Coproduction from Natural Gas Using Cu-Fe Based Metal Oxides in a Chemical Looping System

The increased availability of natural gas as a cheap and readily available resource in the future makes it an ideal raw material for the petrochemical industry. Production of syngas and hydrogen is important because the former is a critical building block for valuable commodity chemicals and the latter is a source of clean energy in addition to being a widely used reactant. Chemical Looping technology presents an attractive alternative to the conventional processes for chemicals and energy production from natural gas with significant reduction in carbon emissions and high exergy efficiency. In a chemical looping system, metal oxide particles undergo sequential reactions, while circulating through different reactors to produce the desired products. In this paper, a three reactor chemical looping system is proposed where syngas is produced from methane in the reducer reactor, the reduced metal oxide particles from the reducer are then partially oxidized by steam to produce hydrogen in the oxidizer reactor and finally they are fully oxidized via air in a combustor reactor. Cu-Fe based oxides were investigated for use in the above mentioned process where different compositions of CuO and Fe₂O₃, with Al₂O₃ as the support, were tested to find a balance between their high reactivity towards natural gas and high selectivity towards syngas, respectively. The reactivity and recyclability of all the compositions was first tested in a Thermogravimetric analyzer (TGA) and then their selectivity towards syngas was tested in a U-tube fixed bed reactor. The Cu-Fe composition producing the highest syngas yields was demonstrated to produce high purity (97.5% dry basis) syngas and high purity (>99.5% dry basis) hydrogen while undergoing multiple reduction-oxidation (redox) cycles in a U-tube fixed bed reactor. X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) surface area and pore volume analysis was done to determine the chemical and morphological changes in the metal oxides at different stages of reaction in the redox cycle. The advantage of using a co-current moving bed reactor for syngas production using Cu-Fe oxides was also demonstrated through experiments in a simulated fixed bed reactor. Experimental results from the fixed bed experiments were used in ASPEN Plus simulation software to perform detailed mass and heat balance and compare the overall energy efficiency of the chemical looping system against the conventional auto-thermal reforming (ATR) process.