A review on Chemical Looping Water Splitting (CLWS) as a potential alternative to Steam Methane Reforming (SMR) for hydrogen production

Abstract

Hydrogen is the fuel of the future as it is a clean fuel and its utilization doesn’t emit greenhouse gases. It is used in various industries from petroleum, fertilizers to pharmaceuticals and even electronics. There are numerous established processes for hydrogen production each having its advantages and disadvantages. The current benchmark is Steam Methane Reforming (SMR). Despite giving a stable output, it releases harmful gases in the environment and has other challenges. Therefore, there was a need to find an inexpensive, efficient and environmentally friendly process with possible CO2 sequestration. CLWS, an alternative to SMR is a three step process where a transition metal oxide, preferably an iron-based oxide undergoes reduction, steam iron process and oxidation to produce hydrogen. This process has many advantages like the production of separate H2 and CO2 streams, no need to have additional units like acid gas removal and pressure swing adsorption. The only challenge is to perform process simulations such that we obtain maximum H2 yield with minimum carbon deposits which reduce the efficiency and purity of the hydrogen produced. CLWS has been studied in detail and optimum parameters for each of the underlying processes have been compiled along with suitable reactor design schemes, thermodynamics etc.