This disclosure describes a method for regenerating a semi-regenerated reforming catalyst. The method comprises adjusting the reaction temperature to 250-480 C., introducing a sulfur-containing naphtha into the reforming reactor, or stopping introducing a feedstock into the reforming reactor, and introducing a sulfur-containing hydrogen into a recycle gas, until the sulfur content in the catalyst is 0.32-0.8 mass %, then the catalyst is subject to coke-burning, oxychlorination and reduction. Alternatively, the method first subjects the spent catalyst to coke-burning followed by introducing sulfate ions thereinto; and then performing oxychlorination and reduction. Disclosed is still another method for regenerating a platinum-rhenium reforming catalyst, which comprises coke-burning the spent catalyst; introducing sulfur and chlorine in the catalyst by impregnation; and then drying, calcinating and reducing.

This disclosure describes a method for regenerating a semi-regenerated reforming catalyst. The method comprises adjusting the reaction temperature to 250-480 C., introducing a sulfur-containing naphtha into the reforming reactor, or stopping introducing a feedstock into the reforming reactor, and introducing a sulfur-containing hydrogen into a recycle gas, until the sulfur content in the catalyst is 0.32-0.8 mass %, then the catalyst is subject to coke-burning, oxychlorination and reduction. Alternatively, the method first subjects the spent catalyst to coke-burning followed by introducing sulfate ions thereinto; and then performing oxychlorination and reduction. Disclosed is still another method for regenerating a platinum-rhenium reforming catalyst, which comprises coke-burning the spent catalyst; introducing sulfur and chlorine in the catalyst by impregnation; and then drying, calcinating and reducing.

A process for the regeneration of a supported noble metal catalyst comprising contacting the catalyst with a liquid aqueous system at a temperature in the range of from 90 to 160 C., wherein the pH of the aqueous system is outside the range of from 6 to 8, separating the aqueous system from catalyst; and subjecting the catalyst to calcination.

A process for the regeneration of a supported noble metal catalyst comprising contacting the catalyst with a liquid aqueous system at a temperature in the range of from 90 to 160 C., wherein the pH of the aqueous system is outside the range of from 6 to 8, separating the aqueous system from catalyst; and subjecting the catalyst to calcination.

The invention refers to a process for rejuvenating a hydrotreating catalyst comprising a group VIB hydrogenation metal and/or a group VIII hydrogenation metal, which comprises the steps of: (a) regenerating the catalyst by contacting said catalyst with an oxygen containing gas at a temperature from about 300 C. to 550 C. to obtain a regenerated carbon-reduced catalyst, (b) impregnating the regenerated carbon-reduced catalyst with a solution which consists of a mixture of water and citric acid, (c) aging the impregnated catalyst for at least 6 hours and (d) drying the aged catalyst. The invention also refers to the rejuvenated catalyst obtained and its use for hydrotreating hydrocarbon feedstocks.

The invention refers to a process for rejuvenating a hydrotreating catalyst comprising a group VIB hydrogenation metal and/or a group VIII hydrogenation metal, which comprises the steps of: (a) regenerating the catalyst by contacting said catalyst with an oxygen containing gas at a temperature from about 300 C. to 550 C. to obtain a regenerated carbon-reduced catalyst, (b) impregnating the regenerated carbon-reduced catalyst with a solution which consists of a mixture of water and citric acid, (c) aging the impregnated catalyst for at least 6 hours and (d) drying the aged catalyst. The invention also refers to the rejuvenated catalyst obtained and its use for hydrotreating hydrocarbon feedstocks.

A metal contaminated spent catalyst or regenerated catalyst from a biomass conversion unit may be subjected to an ammonium wash in order to remove potassium. The ammonium wash may include ammonium sulfate, ammonium nitrate, ammonium hydroxide, ammonium acetate, ammonium phosphates, and mixtures thereof. Acidity and catalytic activity of the biomass conversion catalyst is restored by the removal of potassium contaminants.

A metal contaminated spent catalyst or regenerated catalyst from a biomass conversion unit may be subjected to an ammonium wash in order to remove potassium. The ammonium wash may include ammonium sulfate, ammonium nitrate, ammonium hydroxide, ammonium acetate, ammonium phosphates, and mixtures thereof. Acidity and catalytic activity of the biomass conversion catalyst is restored by the removal of potassium contaminants.

The invention relates to a method of regenerating the catalytic activity of a spent catalyst comprising nickel on a refractory oxide support, said method comprising the steps of contacting the spent catalyst with a nitric acid solution, heat-treating the spent catalyst, calcining and reducing the catalyst.

The invention relates to a method of regenerating the catalytic activity of a spent catalyst comprising nickel on a refractory oxide support, said method comprising the steps of contacting the spent catalyst with a nitric acid solution, heat-treating the spent catalyst, calcining and reducing the catalyst.