Читать книгу Engineering Solutions for CO2 Conversion - Группа авторов - Страница 48

As previously mentioned, the impact of the CO₂ emissions on Earth is triggering the energetic transition from fossil fuels to environmentally friendly energy sources. H₂ is a promising energy carrier allowing the storage of chemical energy; nowadays, its main use is as a reactant for the synthesis of NH₃ and CH₃OH, in the refining and other industrial applications. H₂ can be used in fuel cell cars, as feed into the natural gas network, and in H₂/O₂ fuel cells among others [66–69].

Therefore, H₂ separation is an important process and its utility has been demonstrated over the past years. Pressure gradient is the main driving force for H₂ separation in these type of membranes, giving a large H₂ partial pressure, hydrogen will migrate across the membrane. These membranes operate at a wide range of temperatures, and they can be divided into six different types depending on their properties, temperature ranges, and H₂ permeation performance. Table 3.1 shows a comparison between H₂‐selective membranes.

Among these membranes, mixed protonic–electronic conductor (MPEC)‐based membranes are the most appropriate candidates for application to high‐temperature H₂ (>500 °C) separation‐based processes. These membranes allow to separate H₂ because of their ambipolar conductivity (electronic and protonic) when a hydrogen partial pressure difference is applied across the membrane [72–76]. This technology is the focus of many research groups worldwide because it offers the advantage of process intensification by shifting the thermodynamic equilibrium of a reaction [77–79].