Solid solution for catalytic ammonia synthesis from nitrogen and hydrogen gases at 50 °C

Abstract

The lack of efficient catalysts for ammonia synthesis from N 2 and H 2 gases at the lower temperature of ca. 50°C has been a problem not only for the Haber-Bosch process, but also for ammonia production toward zero CO 2 emissions. Here, we report a new approach for low temperature ammonia synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF 2 and CaH 2 formed at low temperatures. The catalyst produced ammonia from N 2 and H 2 gases at 50°C with an extremely small activation energy of 20 kJ mol −1 , which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca 2+ and H − ions in the solid solution and the facile release of hydrogen atoms from H − sites.

Development and Recent Progress on Ammonia Synthesis Catalysts for Haber–Bosch Process

“…Extremely low‐temperature ammonia synthesis from H 2 and N 2 has been recently demonstrated using a Ru‐based catalyst by Hattori et al [ 107 ] Solid solution CaFH was used as the Ru catalyst support with an activity of 50 μmol g −1 h −1 achieved at ambient pressure and a near‐ambient temperature of 50 °C. CaFH support can be formed at low temperature from the solid solution of CaF 2 and CaH 2 ; the week ionic bonds in this solid solution between Ca 2+ and H − were attributed to the excellent catalytic performance by Hattori et al, [ 107 ] with the H − sites facilitating the release of hydrogen atoms.…”

Gas-phase amination of aromatic hydrocarbons by corona discharge-assisted nitrogen fixation

“…Misawa et al 9 developed a plasmon-induced technique for ammonia synthesis from N 2 that responded to visible light through a strontium titanate (SrTiO 3 ) photoelectrode loaded with gold nanoparticles. Masashi Hattori 10 et al reported a stable electron-donating heterogeneous catalyst, cubic CaFH to produce ammonia from N 2 and H 2 gases at 50 °C with an energy of 20 kJ·mol −1 .…”

Recent Advances in Heterogeneous Catalysis for Ammonia Synthesis

“…Recently, Hosono group developed a novel cubic CaFH solid solution(a kind of hydride), which has ability to form NH 3 at 50 °C with very low activation energy of 20 kJ/mol [62] . This is the first report of any catalyst in NH 3 synthesis at lower temperature and pressure.…”

“…[21,[63][64][65][66][67] In this regard, several binary nitrides of Mo, U, V and Re were explored. [58][59][60][61][62] Detailed mechanism of binary nitride in NH 3 synthesis is well documented in review by J Hargreaves. [21,68] Hence, current section is devoted to more recently explored ternary nitrides that are more stable and active compared to binary nitrides in NH 3 synthesis.…”

“…In late 20 th century, high N 2 adsorption properties of early transition metal predicted nitrides as probable catalysts for NH 3 synthesis [21,63–67] . In this regard, several binary nitrides of Mo, U, V and Re were explored [58–62] . Detailed mechanism of binary nitride in NH 3 synthesis is well documented in review by J Hargreaves [21,68] .…”