Effect of Ammonia In Syngas On the Fischer–Tropsch Behavior of a Precipitated Iron Catalyst

Effect of ammonia in syngas on the Fischer¨CTropsch behavior of a precipitated iron catalyst

Wenping Ma, Gary Jacobs, Jungshik Kang, Dennis Sparks, and Burtron H. Davis^*

Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, Kentucky, 40511, USA

Abstract

The effect of ammonia in syngas in the concentration range of 100 ppbw ¨C 200 ppmw on Fischer¨CTropsch reaction over 100 Fe/5.1 Si/2.0 Cu/3.0 K catalyst was studied at 260 ^oC, 175 psig, H₂/CO = 0.67 and 10 Nl/g-cat/h  in a 1-L slurry phase reactor. The ammonia added in syngas originates from concentrated ammonia and ammonia nitrate soution. Three concentrations of ammonia in syngas feed,  i.e. 100 ppbw, 20 ppmw and 200 ppmw, were employed to examine the sensentivty of the iron catalyst to NH₃. The examinion of the impact of each NH₃ concentration on the iron catalyst FTS performance lasted for 144 or 168 h. The results indicated that  the iron catalyst  was quite resistant to NH₃ poisoning at the FTS conditions used. During 950 h of testing, no changes on the catalyst selectivities to CH₄, C₅₊ , and CO₂, the selectivities to C₄ olefin and paraffin,  and the selectivities to straight C₄ olefin and internal C₄ olefin was observed. The catalyst displayed a slight increase in CO conversion while adding 100 ppbw solution in the first 96 h, which might be partly due to a slight increase in the water-gas shift activity for the catalyst. Afterwords, the iron catalyst  displayed a stable CO conversion (~56.3%) regardless of the concentrations of NH₃ used.  

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* Corresponding author:  Burtron H. Davis, davis@caer.uky.edu, Tel: 859-257-0251.