Chromium-modified cobalt molybdenum nitrides as catalysts for ammonia synthesis

Abstract

The influence of chromium compounds on the properties of cobalt molybdenum nitrides was studied. CoMoO4 obtained by precipitation from cobalt and molybdenum salts was modified by the addition of chromium(III) nitrate. A mixture of cobalt-molybdenum nitrides, Co2Mo3N and Co3Mo3N, was formed by ammonolysis of modified CoMoO4. The concentration of Co2Mo3N decreases with increasing chromium content. The specific surface area of cobalt molybdenum nitrides consisting of 2 wt% of Cr atoms increased by 50% in comparison to pure cobalt molybdenum nitrides. The catalytic activity of obtained catalysts in ammonia synthesis process decreases with rising of chromium concentration.

Synthesis of Cobalt Molybdenum Nitrides From Precursors Precipitated at Different pH

“…As mentioned earlier, the initial sample material has a structure corresponding to phase NH 4 Co 2 OH(MoO 4 ) 2 ⋅ H 2 O [21] . The diffraction patterns collected at the 100 °C, and 200 °C do not indicate the change in the phase composition.…”

“…[23] Metallic cobalt and molybdenum nitride Mo 2 N were on the other hand observed only after prolonged thermal treatment, as a result of decomposition. [9b,15] Previous studies of our research group [14,24] pointed out the coexistence of two cobalt molybdenum nitrides phases, Co 3 Mo 3 N and Co 2 Mo 3 N, in the final ammonolysis product. It was also considered if Co 2 Mo 3 N phase is a product of Co 3 Mo 3 N phase decomposition or an intermediate state.…”

“…The ammonolysis process of this precursor was studied in detail in our previous work [16] . The precursor obtained in basic conditions (pH=7.5) was ascribed to a compound with NH 4 Co 2 OH(MoO 4 ) 2 ⋅ H 2 O formula [21] . The refined structure was submitted to the ICDD PDF4+ database with a 00‐071‐0747 number [21] .…”

“…The precursor obtained in basic conditions (pH=7.5) was ascribed to a compound with NH 4 Co 2 OH(MoO 4 ) 2 ⋅ H 2 O formula [21] . The refined structure was submitted to the ICDD PDF4+ database with a 00‐071‐0747 number [21] . It is an example of layered molybdates of transition metals with the Φ y structure, and general formula AT 2 OH(MoO 4 ) 2 ⋅ H 2 O, where A=NH 4 + , Na + or K + , T=Co, Ni, Cu or Zn [22] .…”

Influence of Magnesium Oxide on the Structure and Catalytic Activity of the Wustite Catalyst for Ammonia Synthesis

“…To this day, the iron catalyst obtained as a result of magnetite reduction is the best-known catalyst in the world [ 3 ]. Current trends in the development of catalytic ammonia synthesis encompass the catalysts obtained from magnetite [ 4 ], wustite [ 5 , 6 ], hematite [ 7 ], ruthenium [ 8 , 9 ], cobalt [ 10 ], and cobalt molybdenum nitrides [ 11 , 12 ].…”