Platinum and palladium are used in small but essential quantities in a variety of advanced industrial sectors. Platinum and palladium are used as catalysts in various industrial sectors, especially in the car industry. However, their sources are typically concentrated in South Africa and Russia, and there are concerns about supply security. In terms of resource security, it is important to verify domestic platinum and palladium consumption trends and future demand. In order to understand the domestic platinum and palladium consumption trends in Japan, we tracked the historical platinum and palladium consumption structures from 2001 to 2013, applying a bottom-up approach, and illustrated recent domestic platinum and palladium flow by using a substance flow analysis. The results showed that catalytic converters (9.1-12.8 t) and jewelry (5.3-15.5 t) for platinum, and catalytic converters (14.2-20.0 t) and dental use (9.5-16.4 t) for palladium, have marked the biggest consumption sectors during 2001-2013, where the total consumption of platinum and palladium have fluctuated by 18.4-31.6 t for platinum and from 33.0-46.3 t for palladium. We also forecasted the demand for each end-use of both up to the year 2025 using multiple regression analysis. Our results suggest that platinum demand could decrease from 18.9 t in 2013 to 11.9 t in 2025 and palladium demand could slightly decrease from 33.0 t in 2013 to 13.8 t in 2025.
With the increasing demand for energy-saving technologies, neodymium-iron-boron magnets have been widely utilized in high-efficiency motors. However, the reserves of neodymium, which is a rare earth element (REE), are limited; thus, a strategy for scaling up the REE supply is highly required. In this study, a scenario assessment was conducted to evaluate the effect of material recycling of neodymium from final product waste. Domestic substance flow analysis of neodymium was conducted by focusing on the waste flow of the final product. Moreover, the demand and waste of neodymium until 2050 were forecasted using various multivariate analysis methods. The results showed that the domestic waste of neodymium was forecasted to be 3866–4217 tons/year by 2050. However, material recycling of neodymium from final product waste may cause an additional increase in production by “circular economy rebound”. Considering that CO2 reduction has also been a global challenge to prevent global warming, the rebound effect was calculated. Therefore, a scenario assessment was conducted to evaluate the influence of this rebound effect by estimating the CO2 reduction. The results of this study are expected to make a significant contribution to the establishment of a new strategy for neodymium recycling.
The possibility of a new ammonia synthesis process has been investigated by utilizing V-based alloy membrane under moderate temperature and pressure conditions. Three membrane samples with different coating conditions of Pd-Ag alloy on the outlet side surface have been tested. It is found that the deposition of Pd-Ag alloy on the outlet side surface is needed for V-based alloy membrane for hydrogen permeation at 623 K. While keeping the hydrogen permeation condition, nitrogen gas is flowed to the outlet side surface of the membrane samples, and the reaction gas is bubbled into distilled water to detect ammonia formation by using Nessler's reagent. Ammonia is not synthesized for the membrane sample coated thickly with Pd-Ag alloy on the outlet side surface, indicating that Pd-Ag alloy does not have a dissociation ability of nitrogen molecule. In contrast, ammonia is formed for the membrane sample coated in a grid pattern with Pd-Ag alloy on the outlet side surface. In this case, both V-based alloy and Pd-Ag alloy coexist on the outlet surface, and hydrogen atoms permeating through the membrane and nitrogen atoms dissociated on the surface of V-based alloy probably react with each other to form ammonia.
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