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
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.
* Corresponding author: Burtron H. Davis, firstname.lastname@example.org, Tel: 859-257-0251.