"Influence of support on concentration profiles in alumina pellets impregnated with molybdenum solutions"

P. VÁZQUEZ, C. CÁCERES AND M. BLANCO

INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER

Elsevier

Lugar: Amsterdam; Año: 1993 vol. 20 p. 631 - 635

0735-1933

Theoretical models of diffusive impregnation in spherical and cylindrical pellets were employed to predict concentration profiles of molybdenum that would result from the impregnation of two different commercial alumina supports with molybdenum solutions. The ALC alumina support (cylinder) possesses greater pore volume and less pellet radius than the ALS alumina (sphere). The effective diffusivity coefficient is greater for the impregnation of ALC alumina than in the case of ALS alumina. Adsorption parameters for both supports are similar. For an initial concentration of impregnating solution of 0.05 g MoO3/ml, impregnation time of 1440 min and a ratio of impregnating solution volume to support mass of 5 ml/g, the same flat molybdenum profile was observed in both cases. For a shorter time (60 min), initial concentrations of impregnating solution of 0.05 and 0.15 g MoO3/ml, and ratios of impregnating solution volume to support mass of 0.6, 5 and 50 ml/g, it was observed that the ALC support allowed more molybdenum penetration than the ALS. Greater molybdenum penetration in the ALC support is favored by a greater effective diffusivity coefficient and smaller pellet radius with respect to the ALS. An increase of molybdenum concentration in the solution external to the pores and of the ratio of impregnating solution volume to support mass make the penetrating molybdenum concentration increasingly different between the supports. The greater the driving force for diffusion the more important the difference of molybdenum concentration profiles between both supports.