What are the methods for reactivating deactivated catalysts?

I. High-Temperature Calcination Regeneration Method: Targeted Solution for Carbon Deposition Deactivation

Through high-temperature oxidation reactions, carbon deposits and organic sediments on the catalyst surface and in the pores are converted into CO₂ and H₂O and discharged, restoring the active centers and pore structure. This method is suitable for carbon-deposited deactivated catalysts, such as denitrification catalysts and hydrogenation catalysts. It is simple to operate and low in cost.

1. Pre-treatment: Remove surface dust and impurities from the catalyst, and crush it to 20-40 mesh to facilitate heat transfer;
2. Gradient temperature calcination: In a muffle furnace or dedicated calcination equipment, gradually increase the temperature from room temperature to 350-550℃ (avoiding sudden high-temperature increases that could lead to catalyst sintering), and maintain the temperature for 4-6 hours;
3. Cooling and discharge: Naturally cool down to below 100℃ to prevent secondary oxidation.

A certain base used this method to treat deactivated denitrification catalysts from a coal-fired power plant. Through a combined process of "ash removal + gradient calcination + activity implantation," a total of 20,000 cubic meters of waste catalysts were regenerated. The regenerated catalyst activity was restored to more than 90% of that of fresh catalysts, and the regeneration cost per ton of catalyst was 60% lower than that of new purchases, serving 48 enterprises and achieving green recycling. In another case, a deactivated carbonyl sulfide hydrolysis catalyst from a methanol synthesis plant showed an increase in COS conversion rate from 7.83% to 63.98% after calcination at 550°C for 5 hours.

II. Solvent Washing-Impregnation Regeneration Method: Addressing Poisoning and Active Component Loss

This method involves first washing the catalyst with a solvent to remove soluble poisons on the surface (such as alkali metals and sulfur and chlorine impurities), and then replenishing the lost active components through impregnation to restore catalytic performance. It is suitable for deactivated catalysts due to poisoning or loss of active components, such as carbonyl sulfide hydrolysis catalysts and vanadium-based catalysts.

1. Calcination Pretreatment: Calcination at 350-450°C for 4 hours to remove surface organic matter;
2. Washing and Purification: Washing with deionized water or dilute ammonia water by boiling for 2-3 times, 30 minutes each time, followed by filtration and drying;
3. Active Impregnation: Immersing the catalyst in an impregnating solution containing alkali metal or alkaline earth metal compounds at room temperature (metal compound to catalyst support aluminum ratio of 2.0-6.0%), soaking for 4-6 hours;
4. Drying and Curing: Drying at a constant temperature of 120°C for 4 hours to complete regeneration.

A 10,000 tons/year methanol synthesis plant used this method to regenerate its carbonyl sulfide hydrolysis catalyst. After treatment with "550°C calcination + ammonia water washing + potassium carbonate impregnation," the COS conversion rate reached 94.72%, which is basically the same as that of the fresh catalyst (94.92%), and it operated stably for more than one year, saving over 800,000 yuan in catalyst procurement costs annually. A chemical plant used a deionized water washing + sulfuric acid impregnation process for its vanadium-based poisoned catalyst, achieving a 100% removal rate of alkali metal poisoning elements and a catalyst activity recovery rate exceeding 90%.

III. Gas Purging and Reduction Regeneration Method: Suitable for Sintering and Metal Contamination Deactivation

This method involves purging with an inert gas to remove surface impurities, and then using a reducing gas (such as a H₂/N₂ mixture) to redisperse the sintered metal active components and repair the active centers. This method is suitable for catalysts deactivated by mild sintering and metal contamination, such as platinum-alumina catalysts and zeolite catalysts.

1. Inert gas purging: Nitrogen gas is introduced into a fixed-bed reactor and purged at 280-320°C for 2 hours to remove surface-adsorbed impurities; 2. Reduction treatment: A mixed gas of H₂ and N₂ (H₂ content 5-10%) is introduced and maintained at 255-455°C for 3-4 hours;
3. Cooling and replacement: Heating is stopped, and nitrogen gas is continuously introduced until room temperature is reached to prevent secondary oxidation of the catalyst.

A certain petroleum company used a fixed-bed nitrogen purging and hydrogen reduction process for deactivated platinum-alumina catalysts, with the maximum temperature controlled at 450°C. After 3 cycles of purging and reduction, the carbon removal rate of the catalyst reached 98%, and the activity recovered to more than 85% of that of a new catalyst, allowing it to be continuously used in petroleum cracking reactions, extending the service life by 18 months per batch. A certain chemical enterprise used this method to treat sulfur-poisoned zeolite catalysts, combined with Brønsted acid solution pretreatment, resulting in a 40% increase in noble metal dispersion and a stable reaction conversion rate of over 90%.

When selecting a catalyst regeneration technology, it is necessary to first determine the cause of deactivation (carbon deposition, poisoning, sintering, etc.) and then match the corresponding method. The above three methods cover most industrial scenarios, with low operating thresholds and controllable costs. Through regeneration treatment, not only can catalyst procurement costs be reduced by more than 60%, but solid waste emissions can also be reduced, achieving a win-win situation for environmental protection and economic benefits.

Author: Hazel
Date: 2025-12-19