Reclamation of alumina as boehmite from an alumina-supported spent catalyst

Increasing emphasis has been placed in recent years to recycle spent catalyst wastes generated in the petroleum industries to minimize their environmental problem. Since most of the spent catalysts contain metals in the form of oxides or sulfides supported on an alumina carrier, recovery of the metals and other valuable materials is an economically attractive option for handling the spent catalyst environmental problem. In the present work, attention was focused on the recovery of alumina as boehmite from a spent NiO/Al2O3 catalyst. More than 99% recovery of Al2O3 from the spent catalyst was achieved by treating with caustic soda. Alumina reacted with NaOH forming sodium aluminate from which bayerite [Al(OH)3] was precipitated. Bayerite was converted to boehmite by hydrothermal treatment and then to γ-Al2O3 by calcination at 500 °C. The γ-Al2O3 recovered from the spent catalyst had a large surface area (213 m2/g) and bimodal pore size distribution with a total pore volume of 0.31 ml/g.