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This post was last edited by Shaobin Fluid on 2026-4-21 at 10:48. Hydrogen energy is a clean and efficient secondary energy source, and it will serve as a viable and effective solution to the energy crisis facing the world, particularly developing countries. A hydrogen economy powered by renewable energy will not only reduce dependence on fossil fuels but also cut greenhouse gas emissions, which are the main cause of global warming. Today, most hydrogen production comes from hydrocarbons: oil (30%), coal (18%), and natural gas (48%). The electrolysis of water produces only 4% hydrogen. Currently, steam methane reforming is the most common method for producing hydrogen. It is necessary to produce hydrogen on a large scale in a sustainable manner using non-fossil energy sources. A promising method for the sustainable production of hydrogen is the thermochemical decomposition of water using high-temperature energy from the sun or nuclear power. The iodine-sulfur thermochemical cycle is considered a promising route for hydrogen production, as it can utilize the thermal energy from high-temperature nuclear reactors as a heat source to produce hydrogen from water in a sustainable manner. As shown in Figure 1, this process includes three closed-loop reactions. Figure 1. Schematic diagram showing the thermochemical processes of three closed-loop reactions. The HIx processing stage is the most critical step that determines the overall efficiency of the entire information system process cycle. The HI mixture formed in this Bunsen section is a pseudo-azeotropic composition of HI, water, and iodine, containing only 13 M% HI. The combination of electrodialysis (EED) and membrane reactors (MR) has been identified as one of the potential alternative approaches for treating HIx streams, whereas one-step reactive distillation poses severe challenges due to high pressures (up to 30 bar) and serious corrosion issues (material selection). The low availability issue of HI obtained from this stage can be resolved by using EED, while the one-way equilibrium conversion rate of HI to hydrogen (about 22%) can be shifted by using MR. The low decomposition rate leads to an increase in the amount of circulating materials (hydrogen, iodine, H2O), making it difficult to achieve the expected thermal efficiency of the IS process (~55%). The membrane is the heart of MR; the parameters of permeability (flux) and selective permeability (to hydrogen) affect the degree of synergy between reaction and separation. In 2004, Kluiters provided a review of the current status of various hydrogen-selective permeable membranes. The hydrogen gas generated in the reaction zone can be removed from the reaction mixture via an in-situ selective permeable membrane, thereby overcoming the equilibrium limitations of the reaction. Hydrogen permeation through metal membranes is governed by the Sieverts’ law. In industry, palladium and its alloys are used to create membranes and membrane reactors for the separation and production of hydrogen. Currently, the use of Pd-based MRs is limited by the cost of these alloys. According to literature data, the hydrogen permeability values of certain metals (such as tantalum, niobium, and vanadium) are higher than those of palladium and its alloys. Furthermore, at low temperatures, hydrogen loading causes these metal (Pd) films to become brittle, resulting in the formation of defects and a loss of selectivity. In fact, under the operating conditions of the HI decomposition reaction, Pd and Pd-based alloys cannot be used because of their low corrosion resistance to peracidic acids, whereas refractory metals such as Ta and Nb-based alloys can withstand extreme high-temperature environments. Preparation and characterization of experimental tantalum membranes: The average pore size and pore size distribution of the clay-alumina tubes (250 mm long and 10 mm in outer diameter) were determined using a surface area analyzer. The alumina tube is sealed using an end cap with an internally developed sealant, as shown in Figure 2. Figure 2. Clay-alumina tube sealed with end caps (length 250 mm, outer diameter 10 mm). The coated membrane tube is shown in Figure 3. The Ta-coated membrane tubes were characterized using X-ray diffraction with Cu Ka radiation at 40 kV and 30 mA. The scanning range varies from 20° to 90°, with a step size of 0.02°. Morphological analysis of the ultra-thin skin surface was performed using a scanning electron microscope (SEM). When operating in the secondary electron mode, surface layer images are recorded at an acceleration voltage of 30 kV and a magnification of ×1000. Quantitative surface elemental analysis and mapping of the films are performed using an energy-dispersive X-ray spectrometer (EDX) in combination with SEM and microanalysis systems. Figure 3. Tantalum-coated clay alumina tube. The corrosion study of tantalum is shown in Figure 4: Ta-coated tubes were cut into 2 cm long pieces and immersed in the HI-water azeotrope (57 wt% HI in water) under reflux at temperatures of 125°C and 130°C. The tubes were characterized using X-ray diffraction (XRD) provided by the Italian GNR Analysis Instruments Group (model: EXPLORER), with Cu Ka radiation at 40 kV and 30 mA. The scanning range varies from 20° to 90°, with a step size of 0.02°. Morphological analysis of the thin skin surface was performed using a scanning electron microscope. When operating in the secondary electron mode, surface layer images are recorded at an acceleration voltage of 30 kV and a magnification of ×1000. Quantitative surface element analysis and mapping of the film are performed using an energy-dispersive X-ray spectrometer (EDX) in combination with SEM and microanalysis systems. Figure 4. Setup for the corrosion study of the HI decomposition reaction. Manufacturing of PBMR components and HI decomposition studies: As shown in Figure 5, a platinum-alumina catalyst (2% platinum coated on alumina extrudates with a diameter of 1/16 inch) was filled in the shell side (reaction zone) of the membrane reactor. The membrane tube, together with the catalyst, is assembled into a reactor assembly as shown in Figure 6. The cross-section of the MR component is shown in Figure 7. The experimental setup used for HI decomposition studies is shown in Figure 8. Nitrogen (carrier gas) at a flow rate of 30 mL min-1 was used to evaporate the HI from an evaporator (heated to 130°C) and carry it through the gas pipeline to the membrane reactor. The results regarding the preparation and characterization of the tantalum film: The specific surface area and average pore size of the clay-alumina tubes were analyzed through N2 adsorption studies at -196°C, as determined by an adsorption surface area analyzer. The surface area and porosity were calculated using the BarretteJoynereHalenda (BJH) method within the relative pressure range of P/Po 0.03 to 0.4. Figure 9 shows the pore size distribution of the clay-alumina tube. Figure 9. Pore size distribution of clay-alumina tubes. The XRD of the alumina support tube and Ta-coated film is shown in Figure 10. Figure 10. XRD peaks of clay-alumina and Ta-coated alumina tubes. Figures 11 and 12 show the SEM images of clay-alumina and Ta-coated alumina films, respectively. Figure 11. SEM image of the alumina surface. Figure 12. SEM image of the tantalum-coated surface. Conclusion A model was developed for the packed-bed tantalum membrane reactor used in HI decomposition to determine the optimal operating parameters of the membrane reactor, thereby achieving at least 95% conversion. This study provides valuable insights into the performance of metal film reactors in hydrogen decomposition reactions, and shows that tantalum-based PBMRs can serve as a tool for process intensification to achieve higher thermochemical efficiency.