Synthesis and catalytic application in isobutane dehydrogenation of the mesoporous chromia/alumina catalysts based on a metal–organic framework

• The mesoporous Cr2O3/Al2O3 catalysts were successfully synthesized using MIL-101.
• The inorganic aluminium sources had significant effects on structure of catalysts.
• The surface Cr species existed mainly as Cr6+ and Cr3+ over the catalysts.
• Cr2O3/Al2O3–N exhibited higher selectivity and stability than the reference catalyst.
• Cr2O3/Al2O3–N exhibited high regenerative ability in isobutane dehydrogenation.

The mesoporous chromia/alumina (Cr2O3/Al2O3) catalysts were successfully synthesized using a porous metal–organic framework MIL-101 (Cr3F(H2O)2O(BDC)3·nH2O, BDC = 1,4-benzenedicarboxylate) as a molecular host and chromium precursor, inorganic aluminium salt as the aluminium precursor. The aluminium sources had the significant effects on the structure of the products. The formation of α-Cr2O3 phase was observed in the mesoporous catalyst (Cr2O3/Al2O3–C) prepared by AlCl3·6H2O, whereas additional chromia alumina solid solution CrxAl2−xO3 phase was produced in the catalyst (Cr2O3/Al2O3–N) using Al(NO3)3·9H2O as the aluminium precursor. The surface Cr species existed in the Cr6+ and Cr3+ state over the mesoporous catalysts. The Cr species had a strong interaction with the alumina support. Preliminary catalytic studies showed that the Cr2O3/Al2O3–N catalyst exhibited much higher isobutene selectivity and higher stability than the reference catalyst in the isobutane dehydrogenation. The maintainable dehydrogenation activity during the five dehydrogenation-regeneration cycles indicated high regenerative ability of the catalyst Cr2O3/Al2O3–N. Consequently, this study represents a feasible way toward the facile synthesis of the mesoporous chromia/alumina catalyst. Moreover, this work proposes a novel application of metal–organic framework.

The mesoporous chromia/alumina (Cr2O3/Al2O3) catalysts were successfully synthesized using a porous metal-organic framework MIL-101 as a molecular host and chromium precursor, inorganic aluminium salt as the aluminium precursor.Figure optionsDownload as PowerPoint slide