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Another step forward for new technologies for ammonia synthesis

| By Gerald Ondrey

In late February, Yokogawa Electric Corp. (Toyko; announced that it has invested in and signed a memorandum on a business partnership with Tsubame BHB Co., Ltd. (Yokohama, Japan; Yokogawa is the latest to partner with Tsubame BHB, joining Heraeus Group, Idemitsu Kosan Co., Ltd., Inpex Corp., Nishinippon Plant Engineering and Construction Co., Ltd. and others.

Tsubame BHB is a university-based startup that was founded in 2017 by a group headed by professor emeritus Hideo Hosono of the Tokyo Institute of Technology (TiTech; Yokohama, Japan; Professor Hosono and colleagues first developed an ammonia synthesis method that makes use of electride catalysts (for more information about the catalyst, see Chem. Eng., December 2012, p. 12).

Tsubame BHB’s electride catalysts enable the synthesis of hydrogen and nitrogen at relatively low temperature and pressure levels (300–400°C, 3–5 MPa) compared to the conventional iron-based catalyst of the Haber-Bosch process (400–500°C, 10–30 MPa). The catalyst is made by attaching ruthenium atoms to nanometer-sized cages of a calcium aluminate electride, which confines electrons within the cage. The electride — 12CaO . 7Al2O3 (hereafter C12A7) — is a component found in cement. Hosono’s group developed the C12A7 electride system and professor Michikazu Hara’s group (both at TiTech’s Materials and Structures Laboratory) first applied the electride as a catalyst for NH3 synthesis.

Since 2019, Tsubame BHB has been operating a 20-ton/yr pilot plant at the site of its major stockholder, Ajinomoto Co., Inc. in Kawasaki City. In December 2022, the company received its first commercial plant order to supply a small distributed ammonia-production plant. This first plant is scheduled to start commercial production in 2025.