Utilization of CO2 for syngas production by CH4 partial oxidation using a catalytic membrane reactor

In this research, a synthetic flue gas mixture with added methane was used as the feed gas in the process of dry reforming with partial oxidation of methane using a laboratory scale catalytic membrane reactor to produce hydrogen and carbon monoxide that can present the starting point for methanol or ammonia synthesis and Fischer-Tropsch reactions. 0.5% wt% Rh catalyst was deposited on a γ-alumina support using rhodium (III) chloride precursor and incorporated into a shell and tube membrane reactor to measure the yield of synthesis gas (CO and H₂) and conversion of CH₄, O₂ and CO₂ respectively. These measurements were used to determine the reaction order and rate of CO₂. The conversion of CO₂ and CH₄ were determined at different gas hourly space velocities. The reaction order was determined to be a first-order with respect to CO₂. The rate of reaction for CO₂ was found to follow an Arrhenius equation having an activation energy of 49.88 × 10⁻¹ kJ mol⁻¹. Experiments were conducted at 2.5, 5 and 8 ml h⁻¹ g⁻¹ gas hourly space velocities and it was observed that increasing the hourly gas velocities resulted in a higher CO₂ and CH₄ conversions while O₂ conversion remained fairly constant. CO₂ had a high conversion rate of 96% at 8 ml h⁻¹ g⁻¹. The synthesized catalytic membrane was characterized by Scanning Electron Microscopy (SEM) and the Energy Dispersive X-ray Analysis (EDXA) respectively. The micrographs showed the Rh particles deposited on the alumina support. Single gas permeation of CH₄, CO₂ and H₂ through the alumina support showed that the permeance of H₂ increased as the pressure was increased to 1 × 10⁵ Pa. The order of gas permeance was H₂ (2.00 g/mol) > CH₄ (16.04 g/mol) > N₂ (28.01 g/mol) > O₂ (32 g/mol) > CO₂ (44.00 g/mol) which is indicative of Knudsen flow mechanism. The novelty of the work lies in the combination of exothermic partial oxidation and endothermic CO₂ and steam reforming in a single step in the membrane reactor to achieve near thermoneutrality while simultaneously consuming almost all the greenhouse gases in the feed gas stream.