Method for the purification of alumina

A method for recovering reusable catalyst and alumina from a hydroprocessing operation comprising:

• washing a granular, vanadium- and oil-contaminated, alumina-based catalyst with an oil-dissolving solvent sufficiently to render the catalyst free-flowing [non-sticky];
• separating the washed catalyst into a first, higher density portion and a second, lower density portion;
• returning the second, lower density portion to the hydroprocessing operation;
• purifying alumina contaminated with iron-, titanium-, and/or magnesium-containing compounds in the first, higher density portion by
• digesting the contaminated alumina in sulfuric acid to produce a first solution comprising aluminum sulfate, ferric sulfate, titanyl sulfate, and/or magnesium sulfate;
• passing the first solution over metallic iron to reduce any ferric sulfate to ferrous sulfate and produce a second solution;
• adding ammonia to the second solution to precipitate hydrated titania from any titanyl sulfate;
• filtering the second solution to remove any hydrated titania and produce a third solution;
• adding ammonium sulfate to the third solution to form a fourth solution comprising ferrous ammonium sulfate and ammonium aluminum sulfate;
• crystalizing ammonium aluminum sulfate from the fourth solution;
• dissolving the crystalized ammonium aluminum sulfate to form a fifth solution;
• adding ammonium bicarbonate to the fifth solution to precipitate basic ammonium aluminum carbonate;
• recovering the basic ammonium aluminum carbonate;
• heating the recovered basic ammonium aluminum carbonate for a time and at a temperature sufficient to produce alumina, ammonia, and carbon dioxide;
• adding ammonia or ammonium sulfate to the fourth solution to adjust to equimolar conditions to form a sixth solution;
• adding oxalic acid to the sixth solution to form insoluble ferrous oxalate;
• filtering the fifth solution to remove any ferrous oxalate and produce a seventh solution;
• adding oxalic acid to the seventh solution to precipitate magnesium oxalate;
• recovering any magnesium oxalate from the seventh solution;
• heating the magnesium oxalate to form magnesium oxide;
• heating the ferrous oxalate to produce ferrous oxide and carbon monoxide;
• and,
• reducing any ferrous oxide to metallic iron.