Operation of fixed bed reactors with periodic flow reversal as proposed by
Matros and co-workers is an unconventional mode of operation for exothermic
, equilibrium limited catalytic reactions. In the present paper, reverse fl
ow ammonia synthesis at 240-300 bar over a promoted iron catalyst is consid
ered. The catalyst had a particle size of 1.0-1.5 mm to neglect the intra-
and interparticle transport intrusions. Temperature profiles, which develop
ed and moved back and forth through the laboratory scale reactor, depending
upon the direction of the flow, and the exit ammonia concentration were mo
nitored. The time average ammonia concentration observed in the non-steady-
state of operation was exceeded by 5-27% the ammonia concentration obtained
in similar but under steady-state conditions. The enhancement in the ammon
ia production was mainly due to the transient state of the catalyst surface
and the dynamic behavior of the reactor bed.