Waste Management In Petroleum Refinery Spent Catalyst

Solid catalysts containing metals, metal oxides or sulfides supported on an alumina
carrier, which play a key role in the refining of petroleum to clean fuels and many other
valuable products, become solid wastes after use. In many refineries, the spent catalysts
discarded from hydro processing units form a major part of these solid wastes. Disposal
of spent hydro processing catalysts requires compliance with stringent environmental
regulations because of their hazardous nature and toxic chemicals content. Various
options such as minimizing spent catalyst waste generation by regeneration and reuse,
metals recovery, utilization to produce useful materials and treatment for safe disposal,
could be considered to deal with the spent catalyst enviromnental problem.
In the present work, attention was focused on the recovery of alumina as aluminium
trihydroxide from spent Nil Al203 catalyst. More than 93% recovery of alumina in the
form of aluminium trihydroxide was achieved using the dry roasting method. Alumina
reacted with NaOH forming sodium aluminate from which aluminium trihydroxide was
precipitated. The effect of temperature with constant I :3 mole ratio to the amount of
aluminium trihydroxide recovered was studied.