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Surface microstructure investigation of calcined θ‐Al 2 O 3 ‐supported molybdena catalyst
Author(s) -
Zaki M. I.,
Ismail H. M.,
Fahim R. B.
Publication year - 1986
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740080502
Subject(s) - calcination , thermogravimetric analysis , adsorption , catalysis , monolayer , aqueous solution , microstructure , scanning electron microscope , differential thermal analysis , chemical engineering , infrared spectroscopy , materials science , thermogravimetry , inorganic chemistry , chemistry , analytical chemistry (journal) , diffraction , crystallography , nanotechnology , organic chemistry , composite material , physics , engineering , optics
Samples of θ‐ and α‐Al 2 O 3 ‐supported molybdena catalyst of various loading levels (0.5–16 wt% MoO 3 ) were prepared by impregnation of the support from a dilute aqueous solution (at pH 6) of ammonium paramolybdate. After drying at 80°C, they were calcined at 550°C for 16 h. The effect of support nature and Mo loading level on surface microstructural characteristics, namely physicochemical identity of the supported Mo‐O species and consequent textural modifications of the calcination products thus yielded, were investigated by means of differential thermal and thermogravimetric analyses, x‐ray diffraction, infrared spectroscopy, scanning electron microscopy and N 2 adsorption. The results obtained show that during the thermal treatment of the impregnated samples the adsorbed paramolybdate anions interact preferentially with the thermally most stable surface OH groups (relatively most basic) which reside at the interior and/or entrances of fine pores of the support. They further show that α‐Al 2 O 3 stabilizes the molybdates loaded at up to 12% level in monolayer‐like structures, however α‐Al 2 O 3 does not do likewise giving way to the formation of Al 2 (MoO 4 ) 3 and bulk MoO 3 at a loading level as low as 4%.