The structure and properties of porous mixed metal oxide
catalysts
(Ga
x
Al2–x
O3 and Pt/Ga
x
Al2–x
O3) derived from calcination
treatment of bimetallic MIL-53(Ga, Al) precursors were comprehensively
characterized using XRD, N2 adsorption–desorption
isotherms, TEM, and solid-state NMR. Both Ga and Pt species are highly
dispersed in Pt/Ga0.1Al1.9O3 and
Pt/Ga0.5Al1.5O3 catalysts with low
Ga content, whereas Ga2O3 particles are present
in Ga1.0Al1.0O3 and Ga1.5Al0.5O3 catalysts with high Ga content. Well-mixed
Al and Ga species in the calcined Ga0.1Al1.9O3 and Ga0.5Al1.5O3 samples
are identified from 1H–71Ga S-RESPDOR
and 1H–27Al TRAPDOR NMR experiments.
The coordination states and relative amounts of Al and Ga species
in the MIL-53(Ga, Al) derivatives are determined by 27Al
and 71Ga MAS NMR measurements. It is found that Pt species
are readily anchored with pentacoordinate Al, favoring the formation
of tetrahedral GaIV species, and the synergy between highly
dispersed Pt and tetrahedral GaIV active species in Pt/Ga0.1Al1.9O3 and Pt/Ga0.5Al1.5O3 catalysts renders their superior catalytic
performance with high conversion and good recyclability toward the
propane dehydrogenation reaction.