ABSTRACT
Molybdenum / composite oxide catalysts play an important role in dehydrogenation –
hydrogenation process. In the present investigation, alumina-magnesia and aluminachromia
composite materials were used as supports. The structural and phase
changes of the prepared catalysts were determined using different techniques:
Fourier transform infrared spectroscopy, x-ray diffraction pattern, differential scanning
calorimetery and surface properties. X-ray diffraction pattern exhibited the formation
of MgMoO4 phase on the surface of alumina-magnesia support with small crystallite
size. Bulky crystallites Cr2(MoO4)3 were formed on alumina-chromia support. The
thermal decomposition data confirmed the formation of MoO2 (200-230oC),
Cr2(MoO4)3 (230-280oC), MoO3 (400-450oC) and MgMoO4 (450-550oC) phases.
Surface properties indicate that, the bulky crystallites formed on the surface of
alumina-chromia support, caused blocking of its pores and led to a significant
decrease in surface area from 240.2 m2/g for Mo/alumina-magnesia to 91.04 m2/g for
Mo/alumina-chromia catalyst.