Reactions of oxovanadium(IV) salen and phthalocyanine with sulphur compounds and reducing agents. Relevance to catalytic demetallisation

Abstract The nature of the vanadium compounds in some petroleum crudes is reviewed. Oxovanadium(IV) phthalocyanine and oxovanadium(IV) Schiff base complexes are proposed as models of vanadium coordination in porphyrins and asphaltenes. Reactions of these compounds with hydrogen sulphide, thiols and other organosulphur compounds, sulphur dioxide, and triethylaluminium are described. The Schiff base complex readily undergoes demetallisation, the vanadium being converted to V 2 S 3 . Demetallisation of the phthalocyanine (and porphyrin) complexes is more difficult. With H 2 S and thiols, in the presence of nitrogen bases, the VO(phthalocyanine) was reduced with loss of terminal oxygen but without sulphur insertion. With Triethylaluminium, the vanadium was reduced and the phthalocyanine ring system was attacked. The VO(phthalocyanine) catalysed the aerial oxidation of H 2 S, thiols, and SO 2 . The results are relevant to the problem of catalytic demetallisation.