I am looking for kinetics of hydrogen production via ammonia decomposition with valid reaction constant values to be used in chemkin or cantera. Do you know any reliable model?
Hydrogen production by ammonia decomposition using high surface area Mo2N and Co3Mo3N catalysts†
High surface area bulk molybdenum nitride catalysts were synthesized via temperature-programmed ammonolysis of an ammonium heptamolybdate and citric acid (CA) composite. The synthesized materials were tested for COx-free H2 production via ammonia decomposition for fuel cell application. Cobalt was added at different loadings (1, 3, and 5 wt%) as a promoter for the bulk molybdenum nitrides. The chemical composition and surface morphology of the nitride catalysts were studied by means of XRD, XPS, SEM-EDAX and TEM techniques. Addition of cobalt increased the formation of the γ-Mo2N phase and cobalt existed as the Co3Mo3N phase, which was uniformly distributed over Mo2N as evidenced by TEM and SEM analyses. A drastic increase in Mo2N crystal size was observed when the Co loading exceeded 3 wt%, which in turn decreased the catalyst activity for ammonia decomposition reaction. All catalysts exhibit higher activity than the reported nitride catalysts at low temperatures. All catalysts showed stable activity for 30 hours. The activation energy calculated for ammonia decomposition was decreased drastically from 131.2 to 99 kJ mol−1 by the addition of cobalt (1 wt%) in Mo2N preparation.
The hydrogen can be extracted via thermal catalytic decomposition or electro-oxidation. Alternatively ammonia may be oxidized directly in fuel cells without the need for a separate reactor. Hydrogen has a very low energy density (per volume) because of its low density.
Catalytic decomposition of ammonia
2NH3+92.4kJ→N2+3H2
Ammonia is unstable at high temperatures and begins to decompose at 200 C .The slightly endothermic decomposition reaction is shown in above equation. Thermodynamically, 98-99% conversion of ammonia to hydrogen is possible at temperatures as low as 425 C. However in practice, the rate of conversion depends on temperature as well as catalysts.
Various metals, alloys, and compounds of noble metal characters have been tested for ammonia decomposition. These include Fe, Ni, Pt, Ru, Ir, Pd, Rh; alloys such as Ni/Pt, Ni/Ru, Pd/Pt/Ru/La; and alloys of Fe with other metal oxides including Ce, Al, Si, Sr, and Zr. Various catalysts have been used for decomposing ammonia to produce hydrogen for alkaline fuel cells. These include WC, Ni/Al2O3, NiCeO2/Al2O3, Cr2O3, Ru/ZrO2, and Ru on carbon nano-fibres. Caesium-promoted ruthenium supported on graphite was also found to be very promising . For these catalysts, a minimum temperature of 300 C is required for efficient release of ammonia for hydrogen production.
https://cyberleninka.ru/article/n/poluchenie-vodorodsoderzhaschego-gaza-iz-ammiaka-i-ispolzovanie-ego-v-kachestve-topliva-dlya-dvs
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Energy