The discovery of efficient thiol oxidation catalyzed by cobalt phthalocyanine was invented at UOP over 50 years ago [1]. It is the largest industrial use of macrocycles in the hydrocarbon industry. The UOP MeroxTM process, which capitalized on this discovery, has been commercialized by UOP in over 1,700 process units worldwide, treating over 500 million gallons of hydrocarbon per day. The catalytic reaction 1 operates at mild process conditons 35 C and 100 psig in the liquid phase : 2 RSH + 1/2 O2 ---&gt; RSSR + H2O reaction 1 The key to the process is a s highly stable promoted Cobalt Phthaolcyanine catalyst which can selectivlty oxidize thiols with greater than 99% selectivity in complex fuels containing reactive diolefns, basic nitrogen compounds and other competing oxidizable hydrocarbons. In an organometallic bonding sense, Phthalocyanine is a very strong field ligand which can stabilize square planar metal complexes in less common oxidation states, for example Co(I) Pc as a d8 low-spin complex is very viable. This is very important for thiol oxidation catalysis in commercial applications for two reasons. First, H2S carry-over into the catalyst bed can occur, which will extract the metal atom from many chelates forming metal sulfide irreversibly. The stable metal- Pc ligand bonding is stable to H2S and, in fact, will catalyze H2S oxidation. Secondly, the stabilization of Co(I) state in the PC plane is important to access the correct bonding of oxygen and redox potential for thiol oxidation with O2 reduction. The phthalocyanine ligand has an additional advantage in that functional groups can easily be substituted onto the aromatic rings. Substitution on the aromatic ring is an effective approach to vary the redox potential and activity of the central metal atom as well as change the solubility and dispersibility characteristics of the active catalyst for various process configurations. For fixed bed applications, discussed herein, either carbon support or solid base supports can provide a very high surface area hydrophilic surface to disperse metal chelate and promoters. Additionally, complexities arising due to aggregation and stacking of phthalocyanine in solution are avoided. We have developed many generations of patented catalsyts , promoters, and process improvements since the original discovery. The reaction mechanism for the modified Co chelate catalysis and properties which provide for high selectivity and long life will be discussed.

Industrial selective oxidation of thiols in fuels with highly selective cobalt phthalocyaanine catalysts

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