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Ammonia (NH3), which has a 17.7 wt% gravimetric hydrogen density, has been considered as a potential hydrogen storage material. This study looked at the thermocatalytic decomposition of NH3 using a bulk Mo2N catalyst that was boosted by alkali metals (AM: 5 wt% Li, K, Cs). The K-Mo2N catalyst outperformed all other catalysts in this experiment in terms of catalytic performance. At 6000 h−1 GHSV, 100% conversion of NH3 was accomplished using the K-Mo2N, Cs-Mo2N, and Mo2N catalysts. However, when compared to other catalysts, K-Mo2N had the highest activity, or 80% NH3 conversion, at a lower temperature, or 550 °C. The catalytic activity exhibited the following trend for the rate of hydrogen production per unit surface area: K-Mo2N > Cs-Mo2N > Li-Mo2N > Mo2N. Up to 20 h of testing the K-Mo2N catalyst at 600 °C revealed no considerable deactivation. [ABSTRACT FROM AUTHOR]

Herein, we report on the activity and selectivity of bulk γ‐Mo2N catalysts for Fischer–Tropsch lower olefin (FTO) synthesis. An increase in surface area and a decrease in crystallite size were observed for γ‐Mo2N catalysts prepared with the increased molar amount of citric acid (CA), used as a chelating agent during the catalyst synthesis. The reaction products were mainly C2–C3 hydrocarbons in the temperature range of 230–300°C at 2 MPa with a reactant feed composition of CO:H2:Ar = 42.7:34.6:20.8 and a gas hourly space velocity (GHSV) of 1.3 mol/(gcat.h). The catalytic activity of the γ‐Mo2N catalysts increased with increased CA:Mo molar ratio and with temperature. However, the hydrogenation activity of the catalysts also increased, resulting in increased selectivity to paraffins. Selectivity to olefins prefers low CA:Mo, that is, low surface area and large crystallite size of γ‐Mo2N. The γ‐Mo2N catalyst prepared with a CA:Mo ratio of 1 had 56.4 C atom% C2+ hydrocarbon selectivity, 62.4% of which was olefin with 37.8 C atom% selectivity to propylene at 275°C. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to understand the catalytic behaviour of Li and Cs promoted Mo2N for CO hydrogenation to hydrocarbons and oxygenates at the reaction conditions 275–325 °C, 7 MPa, and 30 000 h−1 GHSV. Molybdenum nitrides were synthesized via temperature programmed treatment of ammonium heptamolybdate (AHM) and alkali metal (AM) precursors under continuous gaseous ammonia flow. Unpromoted Mo2N and AM‐Mo2N catalysts were characterized using BET‐pore size, X‐ray diffraction, TPD‐mass of CO, HR‐TEM, and XPS techniques. Nominal loadings of 1, 5, and 10 wt% of Li and Cs were selected for these studies. At a 10 % CO conversion level, the total oxygenate selectivity of 28, 11, and 6.5 % was observed on 5Cs‐Mo2N, 5Li‐Mo2N, and unpromoted Mo2N, respectively. The decreased oxygenate selectivity for unpromoted Mo2N was mainly associated with CO dissociative hydrogenation on Moδ+ sites. On the other hand, improved molecular CO insertion into −CxHy intermediate accelerates the total oxygenate formation on the Cs‐Mo‐N catalyst. However, during nitridation, crystal structure changes were observed in Li‐Mo‐N and the obtained oxygenates selectivity was attributed to the Li2MoO4 phases. At lower AM loadings, the active sites corresponding to oxygenates formation were inadequate, and at higher AM loadings, surface metallic molybdenum decreased the total oxygenate selectivity. [ABSTRACT FROM AUTHOR]

Hydrogen production from ammonia decomposition was studied using a series of unsupported high surface area molybdenum nitride (Mo 2 N) and cobalt promoted molybdenum nitride (3%Co-Mo 2 N) catalysts prepared with citric acid (CA) as a chelating agent. To elucidate the influence of citric acid amount in preparation conditions on the structure and catalytic activity, we prepared catalysts with different citric acid to Mo molar ratios i.e. CA/Mo = 1, 2, 3 and 4. The catalytic activity was evaluated in the temperature range of 300–600 °C at atmospheric pressure. The catalytic activity of the tested samples has changed in the following order of CA/Mo atomic ratio of 1 < 2 < 3 > 4. Therefore, the catalyst prepared by using CA/Mo ratio = 3 showed the highest catalytic activity. BET, XRD, XPS, SEM and TEM-EDS techniques were been used to characterize the catalysts. The increased activity of Mo 2 N-3:1 and 3%Co-Mo 2 N-3:1 catalysts was due to increased surface area, decreased particle size and increased relative proportions of Mo 2 N and Co 3 Mo 3 N phases. The ammonia conversion for 3%Co-Mo 2 N catalyst was increased from 75 to 97% at 550 °C with the increase of CA/Mo ratio from 1 to 3. This enrichment of activity in 3%Co-Mo 2 N-3:1 catalyst is due to increased dispersion of Co 3 Mo 3 N microstructure on γ-Mo 2 N platelets confirmed by SEM and TEM results. No deactivation was observed for any catalysts investigated in this study for ammonia decomposition. [ABSTRACT FROM AUTHOR]

The catalytic performance of Mo 2 N and K-Mo 2 N were assessed in hydrogenation of carbon monoxide in the reaction temperature range of 275–325 °C, 7 MPa and 60,000 h −1 . The nitrides were synthesized via temperature-programmed treatment of ammonium heptamolybdate (AHM) and K-AHM precursors under continuous NH 3 flow. The influence of potassium loading (0.45–6.2 wt.%) on the Mo nitride phase and its resultant effect on the catalytic properties were been investigated. The nitride catalysts were characterized in terms of BET/pore size, powder X-ray diffraction, DRIFTs, CO-TPD-mass, HR-TEM and XPS measurements. The formation of cubic γ-Mo 2 N and monoclinic K 2 MoO 4 phases were confirmed by XRD and TEM. Platelet morphology with particle size in the range of 5–10 nm was observed for γ-Mo 2 N. CO-TPD-mass results mainly revealed molecular CO sorption on Mo 2 N and K-Mo 2 N surface. The highest total oxygenate selectivity (44%, 300 °C) was observed on 1.3K-Mo 2 N with a K/Mo δ+ surface ratio of 0.06. This is associated with well distributed K in the matrix of γ-Mo 2 N. Distribution of K was reduced due to K 2 MoO 4 formation at 3 and 6.2 wt.% K loading. DRIFTs results clearly demonstrates greater hydrocarbon formation on unpromoted Mo 2 N due to (i) CO dissociative hydrogenation (ii) water-gas shift reaction. Further, addition of K to Mo 2 N significantly improved the oxygenate selectivity by promoting the molecular CO insertion into −CHx intermediate. [ABSTRACT FROM AUTHOR]