gamma-Al2O3-supported XMo6 Anderson heteropolyoxomolybdates: Adsorption studies for X = Te-VI, Al-III, Co-III, Cr-III and Ni-II by DR spectroscopy and TPR analysis

The support-overlayer adsorptive interactions, generated when solutions of Anderson heteropolyoxomolybdates were supported as a monolayer on gamma-Al2 O3 by means of the equilibrium adsorption method, were studied by XRD analy sis, DR spectroscopy, electron microscopy (SEM-EDAX) acid TPR methods. The adsorption isotherms and corresponding adsorption parameters (number of act ive sites and adsorption constants) of the gamma-Al2O3-supported ammonium h eptamolybdate were obtained and discussed. The following sequence of adsorp tion strength was suggested: CoMo6 > CrMo6 > TeMo6 similar to AlMo6 > NiMo6 . The effectiveness of the TPR technique as a tool for elucidating interact ion effects was clearly demonstrated. The formation of a gamma-Al2O3-suppor ted Te-Mo mixed valence oxide appears to provide new and interesting cataly tic possibilities.