Abstract
Detailed results are presented of the effect of the concentration of the promoter on the activity and selectivity of the Sm2O3-based catalysts and an examination is made of the effect of the promoters on the phase transition in more detail. We also show that there is an optimum in the behaviour as a function of the promoter content for each of the systems studied. For ease of presentation, although different oxides, carbonates or hydroxides of the promoter metals may be present, depending on the conditions we refer throughout to the promoters as Na, Li, or Ca. XRD measurements show that the presence of Li causes the structure of the Sm2O3 to change from cubic to monoclinic. The latter material has negligible activity and selectivity compared with the former and this is therefore probably responsible for the poor behaviour of the Li-promoted samples. Nevertheless, the increase of the yield with the higher Li contents must indicate a promotion of the monoclinic material by Li species. Whether the decrease in activity associated with the formation of the monoclinic phase is associated with the lower area of this phase or also with a new surface structure is not clear.
Original language | English |
---|---|
Pages (from-to) | 437-442 |
Number of pages | 6 |
Journal | American Chemical Society, Division of Petroleum Chemistry, Preprints |
Volume | 33 |
Issue number | 3 |
Publication status | Published - Aug 1988 |
Externally published | Yes |
Event | Symposium on Direct Conversion of Methane to Higher Homologues - Los Angeles, CA, USA Duration: 28 Sep 1988 → 30 Sep 1988 |