Preparation and Performance of a Novel Bifunctional Catalyst for Autoxidation of Mercaptans

Cobalt phthalocyanine (CoPc) complexes in the presence of caustic are widely used in the refining industry for sweetening (i. e. the catalytic oxidation of mercaptans to disulfides) of petroleum products^1]. However, the use of caustic leads to the environmental and economic disadvantages because the spent caustic is recognized as a hazardous material. To set up a more environmentally friendly process, Holmgren et al. and Liu et al. recently reported that bifunctional mixed Mg-Al oxide (denoted as Mg(Al)O)-supported CoPc catalysts, which possess oxidation sites and basic sites, can effectively oxidize mercaptans to disulfides^2,3]. But for these catalysts, we found that the formation of CoPc aggregates on Mg(Al)O during the autoxidation led to their deactivation.³ It is known that the aggregation can be inhibited by anchoring CoPc to supports, such as TiO₂ and SiO₂, modified with organic functional groups. However,it is unknown whether the basic Mg(Al)O materials can be functionalized with organic compounds with no damage to their basic sites. Here we report the preparation of a novel bifunctional catalysts of cobalt tetraaminophthalocyanine CoPc(NH₂)₄ covalently bound to Mg(Al)O modified with a organosilane, as well as their catalytic performance in mercaptan autoxidation.