Selective hydrogenation of acetylene in an ethylene stream in an adiabaticpacked bed reactor

In earlier studies, the behaviour of single catalyst pellets of palladium o n alumina has been investigated for the reaction of acetylene in an ethylen e stream with hydrogen. Particle runaway, temperature over and undershoots and chemically induced temperature oscillations have been observed. After t hat, the steady state and dynamic behaviour of an adiabatic packed bed reac tor has been studied experimentally. Temperature profiles of both the gas a nd solid phase as well as local temperature differences between the two pha ses were measured. Also here the temperature in the reaction zone exhibited oscillatory behaviour. On addition of CO, the oscillations disappeared and the selectivity improved. For a given set of operating conditions there ex isted a relatively small range of CO contents with good selectivity and sat isfactory conversion. This range depends strongly on the inlet temperature. The dynamic response of the reactor to changes in the CO content showed a c onsiderable wrong-way behaviour. This high sensitivity to fluctuations in t he CO content, found for our experimental reactor, indicates a probable cau se for a thermal runaway in industrial practice. Recommendations for a stab le reactor operation are given.