RU2757365C1 - Method for reactivation of a deactivated hydrotreatment catalyst - Google Patents

Abstract

FIELD: catalysts.

SUBSTANCE: invention relates to a method for reactivation of a deactivated alumina-cobalt-molybdenum or alumina-nickel-molybdenum catalytist for hydrotreatment of hydrocarbon raw materials by calcination and contacting with the reactivating aqueous solution including citric acid, diethylene glycol, followed by drying, wherein the reactivating aqueous solution additionally comprises propylenecarbonate and compounds of Ni or Co and Mo, calcination is executed no less than once in air at a temperature of no greater than 490°C to the residual carbon content of less than 0.2 wt.%, followed by contacting with the reactivating aqueous solution of citric acid, diethylene glycol and propylenecarbonate, including compounds of Ni or Co and Mo, wherein the concentration of citric acid in the solution is within the range of 0.5 to 1.0 mol/l, the total mass fraction of diethylene glycol and propylenecarbonate is within the range of 25 to 50 wt.%, the compounds of Ni or Co are included in the reactivating solution in an amount of up to 0.25 mol/l and Mo up to 0.15 mol/l, then drying is performed at 120°C.

EFFECT: technical result of the invention consists in restoring the activity of the catalyst of deactivated alumina-cobalt-molybdenum and alumina-nickel-molybdenum catalysts to the level of 95% or more from the activity of similar fresh catalysts, while maintaining the mechanical strength of granules of more than 93% of the initial strength, while reducing the time of contact with the reactivating solution compared to the prototype, as well as reducing the temperature of precalcination to 490°C.

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Description

The invention relates to the chemical industry, in particular to the production of catalysts and the oil refining industry, and in particular to the restoration of the activity of aluminum-cobalt-molybdenum and aluminum-nickel-molybdenum hydrotreating catalysts after their regeneration.

Hydrotreating catalysts, most often nickel- and cobalt-molybdenum systems on alumina, are one of the most demanded catalysts for oil refining. Their operation in the overwhelming majority of cases involves several cycles: the spent catalyst is unloaded, subjected to oxidative regeneration with coke burning and oxidation of the active phase, after which the catalyst can be reused.

However, it is known that oxidative regeneration does not allow achieving a complete restoration of the activity of hydrotreating catalysts, due to the migration of the promoter into the support and the formation of Ni (Co) Al ₂ O ₄ spinels, which do not sulfidize at acceptable temperatures, which actually means the loss of the promoter [Teixeira da Silva VLS et al. Regeneration of a deactivated hydrotreating catalyst // Industrial & engineering chemistry research. - 1998. - T. 37. - No. 3. - C. 882-886].

A cost-effective method for increasing the activity of catalysts after regeneration is the so-called. reactivation of hydrotreating catalysts, which allows, at low-cost processing of the regenerated catalyst, to redisperse the precursors of the active phase on the catalyst surface and significantly reduce the amount of promoter contained in spinels.

The reactivation process is significantly affected by the content of residual carbon in the regenerated catalyst, even a small amount of which can significantly reduce the degree of activity recovery. This circumstance leads to the need for regeneration at elevated temperatures.

However, the amount of promoter lost during spinel formation depends, among other things, on the regeneration temperature. In addition, an increase in the regeneration temperature leads to a more complete formation of the spinel phase and an increase in its stability, which also reduces the completeness of the recovery of activity.

For hydrotreating catalysts with moderate initial activity, these circumstances do not prevent the restoration of activity upon reactivation to a level of more than 95% of the activity of the fresh catalyst; however, they should be taken into account when reactivating highly active hydrotreating catalysts, the so-called type II catalysts used for the deepest purification of raw materials.

An increase in the activity of the spent catalyst is possible due to the introduction of an additional amount of active components that compensate for their loss, incl. during the formation of spinels.

So, there is a known method of regenerating a spent catalyst for hydrotreating petroleum feedstock (RU 2299095, 20.05.2007), where after burning sulfur and carbon from the catalyst surface, mechanoactivation is carried out, grinding into powder, introducing nitric acid, promoter salts and ammonium paramolybdate, followed by molding and calcining the resulting mixture. The disadvantage of this method is its complexity and cost, as well as the need for high-temperature calcination of the catalyst after treatment, which significantly reduces the specific activity. An acceptable result in the specified method is achieved by introducing a significant amount of additional active metals, with the receipt of a new catalyst that is significantly different from the original.

There are known methods for regenerating a deactivated hydrotreating catalyst (RU 2484896, 20.06.12; RU 2627498, 08.08.2017), in which, after calcining, the regenerated catalyst is impregnated with a solution of citric acid in organic solvents (alcohols or their ethers) and water. The disadvantage of these methods is the high maximum concentration of citric acid (up to 2.5-5 mol / l), which makes the technology more expensive, as well as a high mass fraction of citric acid in the treated catalyst, which during drying can cause the granules to stick together and form a carbon-like mass on their surface. ... In cases where only an organic solvent is used to dissolve citric acid, this leads to an increase in the cost of technology. A common disadvantage of these methods is also the possibility of impregnation with an excess of solution, which can lead to the entrainment of active components of the catalyst into the excess solution.

There is also known a method for regenerating a deactivated catalyst for hydrotreating petroleum products (RU 2640655, 01/11/2018) by burning coke in a double-circuit regeneration reactor at 500-600 ° C, followed by impregnation with solutions of several acids with heat treatments, including drying and calcining. The method involves the use of several substances as reactivating agents: inorganic, organic acids, organic additives, depending on the type of catalyst.

The disadvantage of this method is the lack of a technique for choosing the composition of the reactivating solution, as well as high-temperature treatment of the reactivated catalyst at 400-650 ° C, during which the re-formation of spinel is possible.

The closest, from the point of view of the obtained technical result and economic indicators, to the proposed invention is a method for regenerating a deactivated catalyst for hydrotreating hydrocarbon feedstock (RU 2674157, 05.12.2018). This method involves calcining the deactivated catalyst at a temperature of no more than 650 ° C, contacting it with a solution of citric acid in a mixture of water, butyldiglycol and diethylene glycol for at least 3 hours, and subsequent drying at a temperature of no more than 220 ° C.

The main disadvantages of this method include:

- high permissible pre-calcination temperature (up to 650 ° C), leading to the formation of well-crystallized spinel, which necessitates prolonged treatment with an acidic solution, which leads to a significant decrease in the strength of the finished catalyst, the formation of dust and crumbs, reducing the catalyst resource;

- high maximum concentration of citric acid in the reactive solution, up to 2.7 mol / l, which can lead to sticking of the granules during drying and the subsequent formation of a carbon-like mass on the surface of the granules;

- the inability to compensate for the loss of the promoter during spinel formation.

The objective of the present invention is to develop a method for the reactivation of deactivated alumo-cobalt-molybdenum and alumina-nickel-molybdenum hydrotreating catalysts to a level of 95% or more of the activity of similar fresh catalysts, without a significant decrease in strength while reducing the contact time with the reactivating solution, as well as reducing the pre-calcination temperature to 490 ° C.

To solve this problem, a method is proposed for reactivating a deactivated alumo-cobalt-molybdenum or alumina-nickel-molybdenum catalyst for hydrotreating hydrocarbon feedstock by calcining and contacting with a reactivating aqueous solution including citric acid, diethylene glycol, and subsequent drying.

The method is characterized in that the reactivating aqueous solution additionally contains propylene carbonate and compounds of Ni or Co and Mo, calcination is performed at least once in air at a temperature of not more than 490 ° C to a residual carbon content of less than 0.2 wt%, then the catalyst is contacted with a reactive aqueous solution of citric acid, diethylene glycol and propylene carbonate, including compounds of Ni or Co and Mo, and the concentration of citric acid in the solution is in the range of 0.5-1.0 mol / l, the total mass fraction of diethylene glycol and propylene carbonate is in the range 25- 50 wt%, Ni or Co compounds are included in the reactivating solution in an amount of up to 0.25 mol / L and Mo up to 0.15 mol / L, and then the resulting catalyst is dried at 120 ° C.

The composition obtained after oxidative regeneration can be re-calcined at a temperature not exceeding 490 ° C to a residual carbon content of less than 0.1 wt%.

The calcined composition obtained after oxidative regeneration is kept in an impregnating solution for 1-2 hours, dried and dried for 10-15 hours with a stepwise rise in temperature to 110-120 ° C.

The reactivating aqueous solution contains Ni or Co and Mo in the form of citrates and phosphomolybdic acid, respectively.

A reactivated hydrotreating catalyst is obtained with an activity of 95% of the activity of a similar fresh catalyst or more.

The implementation of the proposed method is illustrated by the following examples, which, however, do not limit the scope of the invention.

Example 1

The deactivated aluminum-cobalt-molybdenum catalyst for hydrotreating was subjected to oxidative regeneration at a temperature of 450 ° C. The carbon content in the composition obtained after oxidative regeneration was 1.0 wt%, molybdenum trioxide 25.8 wt%, cobalt oxide 5.1 wt%. The catalyst was re-calcined in air at a temperature of 490 ° C until a carbon content of 0.05 wt% was reached. The resulting composition had a pore volume of 0.53 cm ³ / g, a crushing strength of 100 N / granule.

The calcined composition was impregnated with a reactivating aqueous solution containing 0.5 mol / L citric acid, 30 wt%, diethylene glycol, 20 wt%, propylene carbonate, 0.25 mol / L Co in the form of citrate, 0.15 mol / L molybdenum in the form of phosphoromolybdic acid.

The impregnation was carried out according to moisture capacity, the holding time in the wet state was 1 hour. The impregnated composition was dried in air at 120 ° C for 15 hours. The reactivated catalyst had a crush strength of 98 N / pellet.

Example 2

The deactivated aluminum-cobalt-molybdenum catalyst for hydrotreating was subjected to oxidative regeneration at a temperature of 440 ° C. The carbon content in the composition obtained after oxidative regeneration was 1.1 wt%, molybdenum trioxide 24.9 wt%, cobalt oxide 4.0 wt%. The composition was re-calcined in air at a temperature of 430 ° C until its carbon content reached 0.15 wt%. The resulting composition had a pore volume of 0.55 cm ³ / g, a crushing strength of 110 N / granule.

The calcined composition was impregnated with a reactivating aqueous solution containing 1.0 mol / L citric acid, 20 wt%, diethylene glycol, 10 wt%, propylene carbonate, 0.25 mol / L Co in the form of citrate, 0.15 mol / L molybdenum in the form of phosphoromolybdic acid. The impregnation was carried out according to moisture capacity, the holding time in the wet state was 2 hours. The impregnated composition was dried in air at 120 ° C for 10 hours. The reactivated catalyst had a crush strength of 102 N / pellet.

Example 3

The deactivated aluminum-nickel-molybdenum hydrotreating catalyst was subjected to oxidative regeneration at a temperature of 400 ° C. The carbon content in the composition obtained after oxidative regeneration was 1.7 wt%, molybdenum trioxide 22.9 wt%, and the nickel oxide content 5.3 wt%. The composition was re-calcined in air at a temperature of 430 ° C until a carbon content of 0.08 wt% was reached. The resulting composition had a pore volume of 0.47 cm ³ / g, a crushing strength of 131 N / granule.

The calcined composition was impregnated with a reactivating aqueous solution containing 0.8 mol / L citric acid, 16 wt.%, Diethylene glycol, 9 wt.%, Propylene carbonate, 0.02 mol / L Ni as citrate, 0.01 mol / L molybdenum in the form of phosphoromolybdic acid. The impregnation was carried out according to moisture capacity, the holding time in the wet state was 2 hours. The impregnated composition was dried in air at 120 ° C for 10 hours. The reactivated catalyst had a crush strength of 124 N / pellet.

Thus, three reactivated hydrotreating catalysts were obtained, the decrease in strength as a result of reactivation was 2%, 7%, 5% for examples 1, 2, 3, respectively.

The reactivated catalysts were tested in comparison with their corresponding fresh catalysts in the process of hydrotreating a mixed diesel fraction containing 70% straight run diesel fraction, 15 vol% catalytically cracked light gas oil and 15% delayed coking light gas oil. The sulfur content in the mixed raw material was 0.92-1.37 wt.%, 95 vol.% Of the fraction is distilled at a temperature of 352 ° C. The catalysts were preliminarily sulfided with dimethyl disulfide (DMDS). Determination of activity was carried out at a pressure of 4 MPa, a temperature of 340-350 ° C, a hydrogen-containing gas / raw material ratio of 400 Nl / L, and a feed space velocity (SPF) of 1 h ^-1 .

The results are shown in the table.

The degree of recovery of the activity of the reactivated hydrotreating catalyst in comparison with the fresh catalyst was estimated by the equation:

where k is _react. , k _fresh is the rate constant of the hydrotreating process for the reactivated and fresh catalyst, respectively.

Taking the reaction order as pseudo-first, the rate constant of the process was determined by the expression:

where S _ƒ , S _p is the sulfur content (wt%) in the feedstock and reaction products, respectively.

The technical result of the invention is the restoration of the activity of the catalyst of deactivated aluminocobalt-molybdenum and aluminum-nickel-molybdenum catalysts to a level of 95% or more of the activity of similar fresh catalysts, while maintaining the mechanical strength of the granules of more than 93% of the original, while reducing the contact time with the reactivating solution in comparison with the prototype, as well as reducing pre-calcination temperatures up to 490 ° C.

Claims (3)

1. A method of reactivating a deactivated alumocobalt-molybdenum or alumino-nickel-molybdenum catalyst for hydrotreating hydrocarbon feedstock by calcining and contacting with a reactivating aqueous solution including citric acid, diethylene glycol, and subsequent drying, characterized in that the reactivating aqueous solution additionally contains propylene or cobalt carbonate and compounds calcination is carried out at least once in air at a temperature of not more than 490 ° C to a residual carbon content of less than 0.2 wt%, then contact is carried out with a reactivating aqueous solution of citric acid, diethylene glycol and propylene carbonate, including compounds of Ni or Co and Mo, and the concentration of citric acid in the solution is in the range of 0.5-1.0 mol / l, the total mass fraction of diethylene glycol and propylene carbonate is in the range of 25-50 wt.%, Ni or Co compounds are included in the reactivating solution in an amount of up to 0.25 mol / l and Mo up to 0.15 mol / l, and then carried out They are dried at 120 ° C. 2. The method according to claim 1, characterized in that the contact with the reactive aqueous solution is carried out for no more than 2 hours. 3. The method according to claim 1, characterized in that the reactivating aqueous solution contains Ni or Co and Mo in the form of citrates and phosphoromolybdic acid, respectively.