Boron Species Promoting the Isobutene Production

Abstract

The impregnation of boron species on ferrierite in the acid form promotes the catalytic activity in the linear butene skeletal isomerization reaction. Nevertheless, more important is that the presence of boron on potassium ferrierite and alumina, both materials inactive for that skeletal isomerization, allows to produce isobutene. Catalysts prepared following the wet impregnation show a better catalytic performance than the ones obtained by the incipient wetness technique. Boron on both potassium ferrierite and alumina promotes active sites with a suitable acidity to selectively enhance the skeletal isomerization reaction, minimizing the undesirable side ones such as dimerizationoligomerization, cracking, disproportion, and hydrogen transfer. By FTIR characterization, boron-promoted catalysts display a medium-intensity band at 3450-3470 cm-1 which is associated to Si−OH???O groups corresponding to boron-containing units. On B-KFER, which corresponds to boron impregnated on potassium ferrierite by the wet technique, the 3466 and 3635 cm-1 bands have medium and weak intensity, respectively. Both kinds of hydroxyl groups are necessary to give an active material for the isobutene production. For catalysts prepared by wet impregnation, boron on acid-ferrierite displays a qualitative behavior similar to unpromoted zeolite, improving both linear butene conversion and isobutene yield but showing the high activity with a low isobutene selectivity at a short time. B-K-FER maintains its performance with time-on-stream showing the best catalytic stability, without the high activity at a short time. At 450ºC, the highest isobutene selectivity is reached.-1 which is associated to Si−OH???O groups corresponding to boron-containing units. On B-KFER, which corresponds to boron impregnated on potassium ferrierite by the wet technique, the 3466 and 3635 cm-1 bands have medium and weak intensity, respectively. Both kinds of hydroxyl groups are necessary to give an active material for the isobutene production. For catalysts prepared by wet impregnation, boron on acid-ferrierite displays a qualitative behavior similar to unpromoted zeolite, improving both linear butene conversion and isobutene yield but showing the high activity with a low isobutene selectivity at a short time. B-K-FER maintains its performance with time-on-stream showing the best catalytic stability, without the high activity at a short time. At 450ºC, the highest isobutene selectivity is reached.