A regenerated spent hydroprocessing catalyst treated with a chelating agent and having incorporated therein a polar additive.

Methods of activating and/or reactivating a catalyst composition comprising a porous metal oxide (MO.sub.x) catalyst are disclosed. Methods of catalyzing a reaction using a catalyst composition comprising a porous metal oxide catalyst activated and/or reactivated by such a method are also disclosed.

Provided are a copper-zinc alloy catalyst, and a preparation method and use thereof. The method for preparing the copper-zinc alloy catalyst includes: subjecting copper-zinc alloy particles to pretreatment to obtain the copper-zinc alloy catalyst; alternatively, subjecting copper-zinc alloy particles to pretreatment and partial dezincification in sequence to obtain the copper-zinc alloy catalyst.

Provided are a copper-zinc alloy catalyst, and a preparation method and use thereof. The method for preparing the copper-zinc alloy catalyst includes: subjecting copper-zinc alloy particles to pretreatment to obtain the copper-zinc alloy catalyst; alternatively, subjecting copper-zinc alloy particles to pretreatment and partial dezincification in sequence to obtain the copper-zinc alloy catalyst.

A process for preparing a catalyst by selecting an active catalyst and contacting the active catalyst with one or more fluids containing an organic solvent or mixture of organic solvents. In one embodiment, each organic solvent has a dielectric constant within a range of about 5 to about 55 when measured at a temperature of 20 C. to 25 C. The catalyst thus prepared may be used in a process for preparing maleic anhydride.