Measurement of coke levels in catalysts using a portable neutron source

In a previous study, Byrne et al. measured quantitative coke concentration profiles in fixed-bed catalytic reactors in situ by the attenuation of a neutron beam aligned perpendicular to the axis of the reactor. The experiments were performed using a collimated neutron beam from the DIDO reactor at the Harwell Laboratory (UK). In this communication, the authors present some initial results on the in situ measurement of coke profiles using a portable neutron source. The advantages of such a source include its transportability and its availability to the nonnuclear industries. However, a possible problem in using a portable source is the low flux of neutrons compared to that of a nuclear reactor. In order to test the applicability of such a source over a range of coke levels on different catalysts, three reactions were studied. The first of these was the isomerization of xylenes over a silica-alumina catalyst. The second reaction studied was the dehydrogenation of butene to butadiene over a chromia-alumina catalyst. The third reaction considered was the cracking of cumene over a zeolite catalyst. While the silica-alumina catalyst used was a powder, the last two catalysts were in the form of the pellets. The reactions studied also represent different coking processes, i.e., parallel to the main reaction in the case of xylene isomerization reaction, consecutive to the main reaction in the case of butene dehydrogenation, and a complex series-parallel coking process in the case of the cumene cracking reaction.