Ammonia (NH₃) has come to be considered having a great potential as an energy carrier. NH₃ can store and transport a large amount of hydrogen energy using existing infrastructure technology. Besides, R&D themes being conducted in the SIP “Energy Carrier” program have revealed the possibility that NH₃ can be used as relatively economical CO₂-free fuels for power generations and industrial furnaces. This article introduces those R&D outputs relating to NH₃ obtained by the SIP “Energy Carrier” program and discusses the potential of NH₃ as an energy carrier of CO₂-free hydrogen energy which is expected to play a very important role in constructing a low carbon society.

Current status of research on ammonia synthesis from water and nitrogen using renewable energy is introduced. It is expected that the synthesized ammonia will be used for large-scale energy transport as an energy carrier and as a regionally distributed local production for local fertilizer for chemical fertilizer. Introduction of research mainly focuses on research conducted domestically under public support. Electrolysis synthesis method, catalyst synthesis method, plasma synthesis method, thermoChemical cycle synthesis method, artificial photosynthesis method are introduced as synthesis methods.

Recently ammonia has attracted attentions as a candidate of energy (hydrogen) carrier, because it has a high energy density and a high hydrogen content, and carbon dioxide is not released when hydrogen is produced by ammonia decomposition. However, the current major process of ammonia production, the Haber-Bosch process, is operated under high temperature and high pressure. Therefore, Haber-Bosch process consumes a great deal of energy. Based on such background, to reduce energy consumption, a process and a substance that can catalyze ammonia synthesis under mild conditions (low temperature and low pressure) are strongly demanded. Here we show praseodymium oxide supported ruthenium catalyst (Ru/Pr₂O₃) as a candidate of new generation ammonia synthesis catalyst which shows superior ammonia synthesis activity compared with that of the supported Ru catalyst already reported. In order to investigate the origin of high catalytic activity of Ru/Pr₂O₃, we employed several characterization techniques. We found that Ru is deposited over the surface of the Ru/Pr₂O₃ in low-crystallite nano-layers and the catalyst is strongly basic. We considered that such unique surface structural and electronic characteristics synergistically accelerate the rate-determining step of NH₃ synthesis, cleavage of the N≡N bond.

Ammonia synthesis directly from nitrogen and hydrogen was attempted by use of microwave plasma. First, the ammonia yield was investigated using active alumina as a catalyst in a microwave plasma. Next, the influence of the number of microwave radiation ports on ammonia synthesis was investigated. It was found that activated alumina has the effect of improving the ammonia yield. It was also found that the efficiency of synthesis can be raised by decreasing the reaction pressure, by decreasing the microwave output power and by generating a wider range of microwave plasma.

Since first commercial plant was commissioned in early 20 centuries by F. Haber and C. Bosch, ammonia manufacturing technology has been developed continuously. Ammonia is produced by hydrogen from synthesis gas generation facility and nitrogen from the air. The synthesis gas generation process has been developed from coal to light hydrocarbon such as natural gas and naphtha because ofthe availability and the logistics of feedstock and the capital cost for synthesis gas generation facility which occupied the main portion ofthe plant. Recently most of ammonia plants in the world adopt the steam reforming technology by using light hydrocarbon such as natural gas and naphtha. In 1960’s, plant capacity was 600 tons of daily basis but at the present day, the standard daily capacity is around 2,200 tons and maximum 3,000 to 3,300 tons throughput per single train. During these periods, ammonia process has been improved from energy saving point of view and operating conditions such as lower synthesis pressure in accordance with technology development and catalyst innovation This report introduces the history and recent technology development of ammonia process.

Ammonia has been widely used as an industrial refrigerant for a long time. It is reported that fluorocarbon-based refrigerants can cause ozone depletion and global warming, but ammonia does not have such negative effect. In addition, ammonia is one of the natural refrigerants with high performance. MAYEKAWA, founded in 1924, has developed and manufactured compressors and refrigerators for ammonia. This paper introduces recent development and applications of highly efficient refrigerating, heating and other systems such as NH₃ / CO₂ indirect cooling method and ammonia high temperature heat pump.