RU2157728C1 - Method for regeneration alumina- or sulfurized alumina-based reforming catalyst - Google Patents

Abstract

FIELD: petroleum processing catalysts. SUBSTANCE: regeneration of gasoline reforming catalyst includes hydrogen activation, burning out coke, oxidative chlorination, and reduction, one of those stages also including treatment of catalyst with sulfur-containing compounds until concentration of sulfate ion 0.15 to 3 wt % is attained before reduction stage. Additionally, after burning out coke or after oxidative chlorination, catalyst is treated with sulfur-containing in circulating hydrogen-containing gas medium at 400-200 C. EFFECT: increased activity and stability of catalyst due to conservation in catalyst required amount of sulfur in the form of sulfate ion. 2 dwg, 1 tbl, 4 ex

Description

 The invention relates to the field of oil refining, and in particular to methods of regeneration of catalysts for reforming gasoline fractions.

 As the reforming process develops, the composition of the catalysts becomes more complicated due to the introduction of additives that regulate certain functions of the catalysts.

 The basis of reforming catalysts is platinum, uniformly distributed over the surface of the carrier - aluminum oxide. To enhance and control the acidity of the support, an acid promoter, fluorine or chlorine, is introduced into the composition of the catalysts.

 Most of the currently used catalysts also contain metal promoters - rhenium, tin, cadmium, zinc and others. The purpose of metal promoters is to increase the stability of catalysts either by hydrogenation of polycyclic structures - coke precursors, or by redistributing coke on the surface of catalysts with a weakening of the blocking of active metal centers and an increase in the overall coke consumption of catalysts (G.N. Maslyansky, R.N. Shapiro Catalytic reforming gasoline. Publishing house "Chemistry", 1985, pp. 94-104).

 On the metal centers of reforming catalysts, especially catalysts containing rhenium, in addition to the main reactions of dehydrogenation of naphthenes and dehydrocyclization of paraffins, hydrogenolysis reactions take place - the decomposition of hydrocarbons from raw materials to methane, accompanied by coke deposits directly on the metal centers with catalyst deactivation. To suppress hydrogenolysis when starting up fresh and regenerated catalysts, they are treated with hydrogen sulfide or organosulfur compounds, metering these reagents into a stream of hydrogen-containing gas at the reduction stage (USSR patent N 1094178 publ. 27.12.96). Some fresh catalysts are produced in sulfided form, treating them at the final stage of production with hydrogen sulfide.

 Industrial reforming catalysts containing sulfate ion have received a notable distribution (USSR patent N 775880, publ. 07.02.83). When these catalysts are launched, aluminum sulfate is reduced; the resulting hydrogen sulfide blocks active metal centers and inhibits hydrogenolysis.

 The sulfate ion introduced into the catalyst during its manufacture is fully used at the initial start-up and must be reintroduced into the composition of the catalysts. This disadvantage is eliminated in the closest analogue of the proposed method (USSR patent N 1359957, publ. 12/27/96 - prototype).

Так, если обработка катализатора сераорганическими соединениями (R₁-S-R₂) производится ибо в конце сырьевого цикла, либо на стадии водородной активации (фиг. 1, поз.1-2), то образуется сероводород, адсорбирующийся на металле (Pt, Re) и на оксиде алюминия. При выжиге кокса происходит окисление сульфидной серы с образованием окислов серы и фиксацией их носителем.The method of regeneration of the catalyst according to the prototype is presented in figure 1. The entire regeneration process is conventionally divided into 8 stages, and the treatment of the catalyst with sulfur-containing compounds can be carried out at any of the first seven stages so that by the end of the entire cycle the regenerated catalyst contains sulfonated aluminum oxide according to the following reaction scheme:

So, if the treatment of the catalyst with organo-sulfur compounds (R ₁ -SR ₂ ) is performed either at the end of the feed cycle or at the stage of hydrogen activation (Fig. 1, pos. 1-2), then hydrogen sulfide adsorbed on the metal is formed (Pt, Re) and on alumina. When burning coke, sulfide sulfur is oxidized with the formation of sulfur oxides and their fixation by the carrier.

 At the oxidizing stages (Fig. 1, pos. 4-6), various sulfur compounds, including oxides, can be supplied, afterburning them on the catalyst and directly fixing the carrier. It is possible to process the catalyst at intermediate stages during nitrogen circulation with the supply of hydrogen sulfide at the stage (Fig. 1, pos. 3) or sulfur oxides at the stage (Fig. 1, pos. 7).

 Sulfurization of the catalysts in the oxidation stages (Fig. 1, items 4-6) requires a dispersed supply of sulfur compounds and can be carried out by regenerating the catalysts outside the reactors in rotary or belt furnaces.

 In reforming plants, treatment options for the catalyst are used with hydrogen sulfide or organosulfur compounds at the end of the feed cycle at the stage of hydrogen activation (Fig. 1, items 1-2).

The disadvantages of this method is that during subsequent oxidative stages of regeneration (coke burning, 300 - 500 ^o C, 60-80 hours; oxidative chlorination, 500-520 ^o C 4-8 hours; oxidative calcination 520 ^o C, 4-8 hours) sulfur oxides formed during the combustion of adsorbed hydrogen sulfide are not only absorbed by alumina, but are also largely removed with regeneration gases.

 The concentration of sulfate ion before the reduction of the catalyst is insufficient.

 The aim of the invention is to increase the activity and stability of reforming catalysts containing platinum or platinum and metal promoters, a halogen and a carrier - aluminum oxide or sulfonated aluminum oxide.

This goal is achieved by regeneration of the catalysts, including hydrogen activation, coke burning, oxidative chlorination, oxidative calcination and reduction with the treatment of the catalysts at one of the stages with sulfur-containing compounds until the concentration of sulfate ion in the catalyst is reached before reduction of 0.15-3.0 wt.% and additional processing of the catalysts with sulfur-containing compounds in a circulating hydrogen-containing gas at a temperature of 400-200 ^o C after burning coke or after oxidative chlorine vania.

An essential distinguishing feature of the proposed method is the treatment of the regenerated catalyst after coke burning or oxidative chlorination with a hydrogen-containing gas with a sulfur-containing compound at a temperature of 400-200 ^o C.

It should be noted that the procedure for the regeneration of reforming catalysts according to the prototype and the proposed method gives a positive result in cases of normal operation of the catalysts. When sulfur catalysts are poisoned in the feed cycle, in the first stage of reforming, products of hydrogen sulfide corrosion accumulate, in particular iron sulfides FeS _x , which during regeneration and the subsequent feed cycle are a constant source of catalyst poisoning (R.N. Shapiro, B. B. Zharkov, G.A. Lastovkin, Chemical and technology of fuels and oils, 1984, No. 1, pp. 12-14). To exhaustively remove sulfur from sulfur-poisoned reforming catalysts (USSR author's certificate N 1720708, publ. 23.03.92), an additional stage of treating the catalyst with a hydrogen-containing gas between the stages of coke burning and oxychlorination is introduced. The treatment is carried out with a gas with a hydrogen concentration of 90-100 mol% with a hydrogen sulfide content of not more than 1.5 mg / nm ³ , at a temperature of 500-520 ^o C, for 20-50 hours, i.e. under conditions that differ sharply from the conditions of metered sulfurization of the catalyst according to the proposed method.

 Analysis of the known technical solutions in the field of regeneration of reforming catalysts indicates the absence of features similar to the essential distinguishing features of the proposed method, that is, the compliance of the claimed technical solution with the requirements of an inventive step.

The proposed method is as follows (figure 2):
At the end of the raw material cycle (item 1), without stopping the circulation of hydrogen-containing gas, they lower the temperature, turn off the feed, free the gasoline reforming system.

Hydrogen activation (item 2) is carried out during the circulation of a hydrogen-containing gas with a temperature increase to 480-500 ^o C. The purpose of the operation is the desorption of hydrocarbons from the catalyst.

 In the next stage (item 3), hydrogen and gaseous hydrocarbons are removed, the system is filled with nitrogen.

Coke burning (item 4) is carried out during the circulation of nitrogen, into the flow of which air is dosed. The burning temperature of coke is 300-500 ^o C, the oxygen concentration gradually rises from 0.5 to 5.0 vol.%. Usually, after this stage, the installation is cooled and an internal inspection of the reactors is carried out, overloading and partial replacement of the catalyst, repair work.

 As our studies showed, the treatment of the catalyst with sulfur compounds after coke burning is completed gives significantly better results than the prototype method.

For this treatment (pos. 4A), the system is washed with nitrogen, filled with hydrogen-containing gas, and when the circulation is established, the temperature is raised to 400 ^° C. Then, the calculated amount of the organosulfur compound is fed to the reactors inlet and the catalyst is sulfided for 2-8 hours. It was found that a gradual decrease in sulfidation temperature in the range of 400-200 ^o C increases the efficiency of the treatment.

Then the system is washed with nitrogen, air is supplied and at a temperature of 500-520 ^o C, oxygen concentration of 3-10 vol.%, Oxidative chlorination of the catalyst is carried out with a flow of 0.8-1.0% chlorine based on the weight of the catalyst (item 5). Organochlorine compounds (carbon tetrachloride, dichloroethane, etc.) are used as chlorinating agents. Oxychlorination time 2-8 hours.

If the installation did not carry out repair work after burning coke, then sulfidation of the catalyst can be carried out after oxychlorination (item 5A). Additional operations are the same as in the case of pos.4A. For oxidative chlorination (item 5) or for sulfidation of the catalyst (item 5A), oxidative calcination (item 6) is carried out at a temperature of 500-520 ^o C, an oxygen concentration of 5-10 vol.%, A supply of 0.2% chlorine ( in the form of organochlorine compounds). The time of oxidative calcination is 4-8 hours. Then, the reforming system is cooled, washed with nitrogen (item 7), take the WASH and carry out the restoration of the catalyst in the range of 200-400 ^o C (item 8). At a temperature of 400-430 ^o C serves hydrotreated raw materials and the installation is brought to the specified technological mode.

 The advantage of the proposed method is the maximum approximation of operations for the sulfidation of the catalyst to start the installation.

 According to the prototype, between the treatment of the catalyst with sulfur-containing compounds and start-up, the catalyst is in an oxidizing atmosphere at high temperature for 80-100 hours. According to the proposed method, the residence time of the catalyst under these conditions is reduced to 4-16 hours. This solution allows you to save in the composition of the catalyst the required amount of sulfur in the form of a sulfate ion, which increases the activity and stability of the catalyst.

 Examples of industrial applicability of the proposed method are given below (see table. 2).

 Example 1

 In an industrial three-reactor catalytic reforming unit, the combined loading of the catalysts shown in Table 1 is used.

 The installation is operated in a mode that ensures the production of catalysis with an average octane number of 93.2 points according to the research method.

The average characteristic of the processed raw materials: boiling range 90-175 ^o C, aromatics content of 8.0 wt.%, Naphthenes 33.0 wt.%) Paraffins 59.0 wt.%; octane number 56 points; sulfur content less than 1 mg / kg.

The technological mode of reforming: pressure 25 kg / cm ² , the consumption of raw materials 160-170 m ³ / h, the flow rate of circulating hydrogen-containing gas 200-220 thousand nm ³ / h At the beginning of the cycle (the first 10 days), the temperature at the inlet to the reactors was equal to 492 ^o C, the hydrogen concentration in the circulating Hash was 82 vol.%, The yield of catalysis was 85.0 wt.%.

As the catalyst is developed to maintain the octane number at a constant level, the temperature at the inlet to the reactors is increased to 505 ^° C., the hydrogen concentration decreases to 72 vol.%, The yield of catalysis decreases to 83.0 wt.%.

 After 11 months of operation at the facility, a scheduled catalyst regeneration is carried out.

After the feed is stopped at 450 ^° C, the catalyst is treated with a circulating hydrogen-containing gas with a temperature increase of up to 480 ^° C, then the unit is cooled, the WAG is replaced with nitrogen, the temperature is again raised to 350 ^° C, air is supplied and coke is burned with a gradual increase in temperature to 500 ^o C.

 After burning coke, the catalyst in the reactors is cooled, purged with nitrogen, and the reforming section is stopped for repair.

After completion of the repair work, the reactors are purged with nitrogen, filled with hydrogen-containing gas, the temperature during gas circulation is increased to 400 ^o C, and at this temperature the catalyst is sulfurized. 460 liters of sulfur-containing reagent — a mixture of dialkyl disulfides, R ₁ —SSR ₂ (TU 38.4018-87, density 1.13 g / cm ³ , sulfur content 40 wt.% Or 0.45, are fed to the inlet stream for 6 hours in the first reactor; kg / l). The dosage of the reagent in terms of sulfur is 0.3 wt.% By weight of the catalyst in the reactors.

After sulphurization and cooling of the catalyst, the WASH is replaced by nitrogen, air is supplied at 300 ^° C and the temperature is increased to 500-520 ^° C, setting the oxygen concentration to 10 vol.%. Under these conditions, oxidative chlorination of the catalyst is carried out. Within four to four hours, carbon tetrachloride was dosed at the entrance to each reactor based on the supply of 1% chlorine based on the weight of the catalyst in each reactor. Then, at a temperature of 520 ^o C and an oxygen concentration of 10 vol.%, Oxidative calcination of the catalyst is carried out with a dosage of 0.2% chlorine of the total weight of the catalyst through the first reactor. Duration of calcination is 6 hours.

After the completion of calcination, the temperature is reduced to 100 ^° C., the system is washed with nitrogen, nitrogen is replaced by the WASH, the catalyst is reduced, and the feed is supplied.

In the feed cycle, the installation is operated in a mode similar to that described above (pressure 25 kg / cm ² , volumetric feed rate of 1.5 h ^-1 , the circulation rate of the Wash - 1200 nm ³ / m ^{3 of} catalyst per hour).

 The cycle duration was 12 months with an average octane rating of 93.5 points.

The temperature at the inlet of the reactor at the beginning of the cycle is 495 ^o C, at the end of 510 ^o C, the hydrogen concentration at the beginning of the cycle is 80 vol.%, At the end of 68 vol.%. The yield of catalyzate during the cycle was changed from 85.5 wt.% To 82.5 wt.%.

Thus, at a fresh loading of catalysts, the initial activity — the temperature for producing catalate with an octane rating of 93.5 points — was 492 ^° C, and the stability of the catalyst — the rate of rise of the reforming temperature — was 1.2 deg / month.

The catalyst regenerated by the proposed method had an initial activity of 495 ^° C. and a stability of 1.25 degrees / month.

 Example 2

The regeneration of the catalysts in the reforming unit is carried out in the same sequence as described in example 1, only the activation of the catalysts with a mixture of dialkyl disulfides is carried out not at a constant temperature of 400 ^o C, but in a temperature range of 400-200 ^o C. The reagent is fed through the first reactor and after 6 hours lower the temperature in the first reactor from 400 to 300 ^o C, and in the second and third reactors from 400 ^o C to 200 ^o C. The total dosage in terms of sulfur is maintained, as in example 1, equal to 0.3% by weight of the catalyst.

 In the feed cycle, the installation is operated in the mode of example 1.

The cycle duration was 14 months with an average octane rating of 93.5 points. The temperature at the inlet of the reactors at the beginning of the cycle is 490 ^o C, at the end of the cycle 505 ^o C the hydrogen concentration at the beginning of the cycle is 84 vol.%, At the end of the cycle 75 vol.%, The yield of catalysis at the beginning of the cycle is 85.5 wt.%, At the end cycle 83.5 wt.%.

Thus, the sulfurization of the catalysts in the proposed temperature range of 400-200 ^o C helps to reduce the initial reforming temperature to 490 ^o C and reduce the rate of catalyst deactivation to 1.1 deg./month.

 Example 3

The regeneration of the loading of catalysts in the reforming unit is carried out in the same sequence as in example 2, only the sulfurization of the catalyst in the medium of the circulating Hash is carried out after the stage of oxidative chlorination. The installation is cooled to 100 ^o C, flue gases are displaced with nitrogen, take the WASH, increase the temperature to 400 ^o C and begin to sulfurize the catalyst.

330 liters of technical ethyl mercaptan (TU 6-02-511-80, C ₂ H ₂ S; sulfur content 48 wt.% Or 0, is fed into the flow of circulating Hash with a hydrogen concentration of 90 - 70 vol.% At the entrance to the first reactor in 4 hours , 41 kg / liter). The dosage of ethyl mercaptan in terms of sulfur is 0.2% by weight of the catalyst in all three reactors. As in example 2, the temperature in the first reactor in 4 hours is reduced to 300 ^o C, and in the second and third reactors to 200 ^o C.

Then the temperature is reduced to 100 ^o C, the installation is washed with nitrogen, the temperature is increased to 350 ^o C, air is taken in, the temperature is increased to 520 ^o C, and the oxygen concentration is up to 10 vol.% And oxidative calcination is carried out, as in Example 1. Cooling follows installations, flushing with nitrogen, reception of the WASH, recovery of the catalyst and supply of raw materials.

 The duration of the subsequent feed cycle was 17 months with an average octane rating of 93.5 points.

The temperature at the inlet of the reactor at the beginning of the cycle is 490 ^o C at the end of the cycle 508 ^o C, the hydrogen concentration at the beginning of the cycle 84 vol.%, At the end of the cycle 70 vol.%, The yield of catalysis at the beginning of the cycle 86.0 wt.%, At the end cycle 84.0 wt.%.

 The stability of the catalyst — the rate of its deactivation — was 1.05 degrees / month.

 Example 4 (prototype).

 The regeneration of the loading of catalysts in the reforming unit described in example 1 is carried out by the method provided by the prototype - patent N 1359957.

After the feed has been cut off, the catalysts are treated for 6 hours with a hydrogen-containing gas with a hydrogen concentration of 50-70 vol.% At a temperature of 480 ^o C. Then the temperature drops to 400 ^o C and the catalyst is activated with sulfur, for which 460 liters are fed to the inlet of the first reactor dialkyl sulfides, which is 0.3% sulfur by weight of the catalyst in all reactors.

 Further regeneration includes the replacement of the WASH with nitrogen, coke burning, oxidative chlorination and oxidative calcination. After the reduction of the catalyst with a hydrogen-containing gas, they pass to the feed cycle.

 The installation is operated in a mode similar to that described in example 1. The octane number is maintained at the level of 93.0-93.5 points according to the research method.

At the beginning of the cycle (first 10 days), the temperature at the inlet to the reactors is 500 ^o C, the hydrogen concentration of 78 vol.%. After 10 months, the feed cycle ends at a temperature at the inlet of the reactors 515 ^o C, the hydrogen concentration in the WASH is 68 vol.%. The yield of catalysis in 10 months. decreased from 85.0 to 83.0 wt.%.

 The stability of the catalyst in this cycle was 1.5 degrees. / month

Claims (1)

A method of regenerating a reforming catalyst on alumina or on sulfonated alumina containing platinum, metal promoters and a halogen comprising the steps of hydrogen activation, coke burning, oxidative chlorination, oxidative calcination and reduction, with the catalyst being treated at one of the stages with sulfur-containing compounds to a sulfate ion concentration in the catalyst before reduction of 0.15 to 3.0 wt.%, characterized in that between the stages of coke burning and oxidative chlorination or between the stages of oxidation chlorination and oxidative calcination, the catalyst is additionally treated with hydrogen-containing gas and sulfur-containing compounds at a temperature of 400 - 200 ^o C.

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