A thermodynamic methodology toward an optimized methane decomposition process for enhanced hydrogen production and low carbon accumulation: Effect of non-hydrocarbon co-feeds

Abstract

Methane decomposition (MD) is emerging as a proficient technology to pure hydrogen production from a variety of methane-based feedstocks (renewables and non-renewables). Besides pure H2(g), accumulated carbonaceous materials can be extracted and used in electronic devices and catalysis. MD is far from industrialization owing to heavy carbon accumulation leading to immediate deactivation of catalysts. In this work, thermodynamic equilibrium analysis was performed using Gibbs free energy minimization. Temperature (range: 200–1000 °C), (ii) pressure (range: 1–20 bar) and, (iii) feed composition (CH4(g) along with H2O(g), CO2(g) and/or O2(g)) were tuned with an aim to identify theoretical conditions insuring maximized H2(g) generation, low C(s) accumulation and, lesser extent of by-products(g). Operating MD at 800 °C and 1 bar are requirements to achieve maximum methane conversion into H2(g) along with considerable C(s) amounts. Co-feeding of methane with any O2-baring species minimizes carbon accumulation especially in presence of O2(g), (O2+H2O)(g), (CO2+O2)(g) or (CO2+O2+H2O)(g) streams. Not all types of co-feeds are capable of yielding H2(g) in amounts exceeding those expected from pure CH4(g) decomposition. Nonetheless, co-feeding methane with H2O(g) or H2O(g)-containing feed(s) insures maximized H2(g) production. Moreover, depending on the chemistry and content of such species, thermodynamic abundance of by-products can be minimized.