Ammonia synthesis reaction over Co 3 Mo 3 N/SiO 2 catalyst Mustafa Aslan and Justin Hargreaves University of Glasgow, UK
Two-thirds of the ammonia produced by Haber-Bosch process, which is operated at high temperature and pressure (400 – 500 o C, 100-300 bar), all around the world 1 . Ammonia production process consumes ca. 2% of energy production of the world annually 2 . When process economics is taken into consideration, the cost of hydrogen production is responsible for approximately 70% of cost of ammonia production 3 . Therefore, a more sustainable way for producing ammonia is needed to decrease the carbon footprint and the cost of the production process. Molybdenum nitrides are getting attraction due to their stability, atomic nitrogen transfer ability and ammonia synthesis activity 4 . Nominally 10 wt% SiO 2 supported Co 3 Mo 3 N catalyst was synthesized to investigate the effect of H 2 :N 2 ratio on the ammonia synthesis rate. Co 3 Mo 3 N/SiO 2 catalysts were prepared using incipient wetness impregnation and wet impregnation methods. The XRD patterns of the samples that was prepared using two different methods showed that Co 3 Mo 3 N phase on the sample prepared using wet impregnation has sharper crystalline peaks than the sample prepared using incipient wetness impregnation method. SEM analysis of Co 3 Mo 3 N/SiO 2 sample synthesized using wet impregnation showed that Co-Mo crystallites were located on top of SiO 2 particles. Activity studies for both samples were performed under different H 2 :N 2 flow ratios at 400 o C and atmospheric pressure. It was shown that Co 3 Mo 3 N/SiO 2 synthesized using wet impregnation method showed better NH 3 synthesis activity than Co 3 Mo 3 N/SiO 2 synthesized using incipient wetness impregnation method. In addition to this, it was observed that when H 2 :N 2 ratio decreased, NH 3 synthesis rate decreased for both catalysts. The present study showed that preparation method affected the surface distribution of the Co 3 Mo 3 N phase over SiO 2 support and thus influenced the activity and stability of the catalyst. References 1. C.P. Owens, F.E.H. Katz, C.H. Carter, V.F. Oswald, F.A. Tezcan, The Journal of American Chemical Society, 138 (2016), 10124−10127 2. N. Saadatjou, A. Jafari and S. Sahebdelfar, Chemical Engineering Communications, 202 (2015), 420 3. www.ammoniaenergy.org/articles/the-cost-of-co2-free-ammonia/last accessed 16.01.2023 4. D. Mckay, D. H. Gregory, J. S. J. Hargreaves, S. M. Hunter and X. Sun, Chemical Communications, 29 (2007), 3051
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