Regeneration of the Catalyst Precursor for Hydroconversion of a Blend of Petroleum Tar and Polymer Waste

A procedure for regenerating the hydroconversion catalyst precursor was studied. The procedure involves separation of the catalyst concentrate from the hydrogenizate vacuum residue by filtration, heat treatment of the concentrate to obtain the ash residue, and leaching of compounds of Mo and other metals from the ash residue with aqueous ammonia and nitric acid. As shown by X-ray diffraction analysis, the ash residue after the oxidation of the catalyst concentrate contains both individual molybdenum oxide (MoO₃) and mixtures of double (NiMoO₄, V₂MoO₈, NiV₂O₆, Na_0.76V₆O₁₅) and triple (Fe₄V₂Mo₃O₂₀) oxides in the form of alloys. An efficient procedure is the pretreatment of the ash residue with 65% HNO₃, followed by the treatment of the resulting suspension with a mixture containing 10% NH₄OH and 5% (NH₄)₂CO₃. In so doing, up to 88–90% of Мо compounds are extracted into the resulting catalyst precursor solution.