RU2552525C1 - Method of regenerating cobalt-containing catalyst for obtaining synthetic hydrocarbons in accordance with fischer-tropsch method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: regeneration includes oxidation of deactivated catalyst by supply of air into reactor zone at rate 500-2000 h^-1, heating to temperature 200-270°C at heating rate 1-3°C/min and exposure at said temperature in air flow for 1-5 h. Further reduction is carried out by supply of hydrogen-containing gas at oxidation temperature with volume rate 1000-5000 h^-1, heating to temperature 300-600°C at rate 1-5°C/min and exposure at heating temperature in flow of hydrogen-containing gas for 1-5 h. Method includes carrying out additional stage of deactivated catalyst reduction with hydrogen-containing gas before redox regeneration. Hydrogen-containing gas of the similar composition with hydrogen content from 20 to 100 vol % is used in reduction.

EFFECT: increased efficiency of regeneration and increase of catalyst service duration in comparison with other methods known in technology.

4 cl, 1 tbl, 7 ex

Description

The invention relates to petrochemistry, gas chemistry, coal chemistry and relates to Fischer-Tropsch synthesis, in particular a method for regenerating a cobalt-containing catalyst to produce synthetic hydrocarbons according to the Fischer-Tropsch method.

A known method of regenerating a cobalt Fischer-Tropsch synthesis catalyst outside the reaction zone is described in application GB 2482905 A, 08/19/2010. Part of the deactivated catalyst together with liquid hydrocarbons is removed from the reactor, the catalyst is separated from hydrocarbons at a temperature below 220 ° C, oxygen-containing gas is passed through the catalyst and calcined at a temperature of 270-350 ° C for 0.1-2 hours, after which the catalyst is activated . Activation involves passing at a temperature of 300-450 ° C through a calcined catalyst of a reducing gas containing hydrogen. After regeneration of the spent 100 h catalyst, its activity becomes higher than the activity of the initial catalyst by 6 rel. %

The disadvantage of this method is the technological difficulties associated with the transport of activated catalyst and the use of additional equipment during the activation process in a separate reactor.

US Pat. No. 6,486,220 B1, 11/26/2002, proposes a method for regenerating a Fischer-Tropsch synthesis catalyst with a mixture of water vapor and hydrogen, with the content of the latter not exceeding 5%. The regeneration is carried out, preferably, at a temperature of 260-300 ° C and a pressure of 0-2.4 MPa for 5 minutes to 4 hours. It was shown that the conversion of CO in the presence of a cobalt-containing Fischer-Tropsch synthesis catalyst fell from 70% to 15 in 168 hours % After regeneration, the CO conversion increases again to 70%, but after 50 hours it drops again to 25%. After the second regeneration cycle, the CO conversion is 72%, and after the third regeneration, it increases to 77%.

The disadvantage of this method is the rapid deactivation of the catalyst after regeneration, the need for several regeneration cycles to increase the activity of the catalyst and the presence of water vapor in the regenerating gas, which can lead to irreversible cobalt-carrier interaction and a decrease in the amount of active component available for the formation of active catalyst sites.

US Pat. No. 6,878,655 B2, May 12, 2008, proposes a method for regenerating a cobalt-containing Fischer-Tropsch synthesis catalyst with a hydrogen-containing gas, which is carried out in two stages. First, the spent catalyst interacts with the regenerating gas at a temperature above 220 ° C and a pressure above 345 kPa for 4-24 hours. Then, the temperature in the reactor increases to 270-320 ° C at a rate of 1 ° C / min and is maintained for 16-24 h. Conversion of CO relative to the initial value, taken as 1, before regeneration is 0.62-0.77. After regeneration, the relative conversion of CO is in the range of 0.62-1.05.

The disadvantage of this method is the rapid drop in catalyst activity after regeneration.

In the description of patent RU 2436627 C1, December 20, 2011, a method for regenerating spent cobalt catalyst by introducing into the reaction zone a regenerating gas containing hydrogen at a temperature of 100-400 ° C for 5 minutes to 50 hours is presented. When implementing Example 13, the best indicators after regeneration. It was shown that the initial CO conversion was 63%, with a decrease in the activity and deactivation of the catalyst, the CO conversion decreased to 44%, and after regeneration with a hydrogen-containing gas it increased to 51%.

The disadvantage of this method of catalyst regeneration is its low efficiency, which allows you to restore the activity of only 81 rel.% Of the initial activity of the freshly restored catalyst.

The closest technical solution to this invention is the method described in patent RU 2456080 C2, 07.20.07.2012, where a method for regenerating spent cobalt catalyst is proposed, which includes sequential treatment of the catalyst to remove product residues, oxidative treatment and reduction. In order to remove hydrocarbons, it is proposed to pre-conduct their hydrocracking, washing with a solvent or extraction. The oxidizing treatment consists in calcining the catalyst particles placed in the calcining apparatus using ordinary air, i.e. containing about 21 vol% oxygen, at a volumetric air velocity of 1000-3000 ml / _n / g of catalyst / h with a heating rate of 0.1-10 ° C / min, usually at a speed of 0.5-3 ° C / min to a temperature of 250 -350 ° C, preferably, and a pressure of 0.4-1.2 MPa for 0.1-12 hours. The reduction is carried out with a hydrogen-containing gas at atmospheric or elevated pressure and elevated temperature in one or three stages. In one stage, the reduction is carried out in a recovery unit with a fixed catalyst bed at a volumetric hydrogen velocity of 1500 ml / _n / g of catalyst / h, heating rate of 1 ° C / min to 425 ° C with holding at the same temperature for 16 hours. another reduction option in the first stage, the spent catalyst is reduced with a hydrogen-containing gas at a first heating rate to a temperature of 80-180 ° C. In the second stage, the heating rate is lower compared to the first. In the third stage, the lowest heating rate. It was shown that as a result of catalyst deactivation, the activity decreases to a level below 80 rel.% Of the initial catalyst activity. After regeneration, the activity of the catalyst is restored to 92-98 rel.% From the initial value.

The disadvantage of this method is the multi-stage regeneration process, including the stages of wax hydrocracking or solvent extraction, which cannot be carried out in situ in the Fischer-Tropsch synthesis reactor and require the use of additional equipment, which will lead to an increase in capital costs. Another disadvantage of the proposed method of regeneration is the lower activity after regeneration of the catalyst compared with its initial activity.

An object of the invention is to develop a method of redox regeneration of spent cobalt Fischer-Tropsch synthesis catalyst in situ in a Fischer-Tropsch reactor with high activity after regeneration.

The technical result achieved from the implementation of the invention is to increase the efficiency of regeneration and increase the duration of the catalyst after regeneration. Moreover, the regeneration of the deactivated catalyst allows to increase the catalytic activity of the deactivated sample, restore the CO conversion to a value of more than 98 rel.% From the conversion of CO in the presence of a freshly reduced catalyst, to achieve high molecular weight hydrocarbons of 100 rel.% Or more of the productivity of the freshly reduced catalyst, and carry out the synthesis of hydrocarbons from CO and H ₂ for more than 100 hours after regeneration at values of CO conversion and productivity for high molecular weight hydrocarbons exceeding the values of these indicators for a deactivated catalyst.

The technical result is achieved by the fact that for the regeneration of the spent cobalt-containing catalyst, in-situ redox regeneration is used in the Fischer-Tropsch reactor, including oxidation by a stream of air at Fischer-Tropsch synthesis temperatures, deactivating the catalyst of carbon deposits formed during the synthesis, and subsequent recovery, which consists passing through a catalyst bed of hydrogen-containing gas at a temperature above the temperature of the Fischer-Tropsch reaction, during which roiskhodit improving dispersion of the active cobalt component and reduction to the metallic state required for formation of active centers hydrocarbon synthesis from CO and H _2. The deactivated catalyst is oxidized by supplying air to the reaction zone of the reactor at a speed of 500-2000 h ^-1 , heating to a temperature of 200-270 ° C with a heating rate of 1-3 ° C / min and keeping it at this temperature in an air stream for 1-5 h. Subsequent recovery is carried out by feeding at a temperature of oxidation of a hydrogen-containing gas with a space velocity of 1000-5000 h ^-1 , heating to a temperature of 300-600 ° C at a speed of 1-5 ° C / min and holding at a temperature of heating in a stream of hydrogen-containing gas for 1 -5 hours

The method provides for additional reduction of the deactivated catalyst with a hydrogen-containing gas before redox regeneration. In this case, during the recovery, a hydrogen-containing gas of the same composition with a hydrogen content of 20 to 100 vol.% Is used. These distinguishing features are significant.

After catalyst deactivation, the reactor is cooled in a stream of synthesis gas to a temperature of less than 100 ° C and the supply of synthesis gas is turned off, then regeneration is carried out.

The regeneration of the spent catalyst according to this invention is carried out in two or three stages by supplying a regenerating gas to the reaction zone of the Fischer-Tropsch synthesis reactor.

Regeneration is carried out by oxidizing a deactivated catalyst by feeding air into the reaction zone at a space velocity of 500-2000 h ^-1 immediately after turning off the synthesis gas and cooling the reactor to a temperature below 100 ° C or after an additional reduction stage, when the oxidation is carried out in an air stream at a temperature of 200-270 ° C for 1-5 hours after cooling the catalyst in a stream of hydrogen to a temperature of the oxidizing stage. In the first case, the oxidation is carried out by supplying air at a space velocity of 500-2000 h ^-1 , heating the catalytic zone of the reactor to 200-270 ° C with a heating rate of no higher than 3 ° C / min and then keeping it in a stream of air for 1-5 hours. In order to maintain the required temperature during the oxidation process, air consumption may be reduced. After oxidation is complete, the air supply is shut off. To carry out the oxidation, ordinary air containing about 21% by mass of oxygen is used.

Then carry out the recovery process. For this, a hydrogen-containing gas is supplied at a temperature of the oxidizing stage at a space velocity of 1000-5000 h ^-1 and the catalytic zone of the reactor is heated to 300-600 ° C with a heating rate of no higher than 5 ° C / min. After stabilization of the temperature, the mixture is kept in a hydrogen stream for 1-5 hours, then the reactor is cooled in a hydrogen stream to a temperature of less than 100 ° C and synthesis gas is supplied to carry out the hydrocarbon synthesis process. The volumetric rate of a hydrogen-containing reduction gas is greater than the volumetric rate of air at the oxidation stage.

When conducting additional recovery, after cooling the deactivated catalyst in a stream of synthesis gas, hydrogen or a hydrogen-containing gas is supplied to the reaction zone. After stabilization of the flow to 1000-5000 h ^-1 , the catalytic zone of the reactor is heated to a temperature of 300-600 ° C with a heating rate of not higher than 5 ° C / min and maintained at this temperature for 1-2 hours. Then the reactor is cooled in a stream of hydrogen-containing gas to the temperature of the oxidizing stage and shut off the supply of hydrogen-containing gas.

As a hydrogen-containing gas, a gas with a hydrogen content of 20-100 vol.% Is used, the rest is an inert gas, for example helium or argon. For the recovery using hydrogen-containing gas of the same composition.

The efficiency of the regeneration of deactivated cobalt-containing catalysts was evaluated as a result of a study of the catalytic properties of regenerated cobalt-containing catalysts in the synthesis of hydrocarbons from CO and H ₂ according to the Fischer-Tropsch method. Cobalt-containing catalysts, to restore the efficiency of which, after deactivation, the present invention was applied, are represented by Catalyst A and Catalyst B. Catalyst A is a cobalt-containing catalyst containing zeolite and prepared in accordance with patent RU 2493913 C1. Catalyst B - cobalt-containing catalyst based on metal oxides of groups III and IV of the Periodic table Mendeleev prepared in accordance with patent RU 2493914 C1.

The calculation of CO conversion is carried out according to the following formula:

, где

where

- масса моноксида углерода в 1 м³ входящего в реактор газа;

- mass of carbon monoxide in 1 m ^{3 of} gas entering the reactor;

- масса моноксида углерода в 1 м³ выходящего из реактора газа.

- the mass of carbon monoxide in 1 m ³ leaving the reactor gas.

The calculation of productivity is carried out according to the following formula:

, где

where

m _{C5 +} is the mass of high molecular weight hydrocarbons formed as a result of Fischer-Tropsch synthesis over time τ, kg;

τ is the duration of the synthesis, h;

V _cat - the amount of catalyst loaded in the Fischer-Tropsch synthesis reactor, m ³ .

The determination of the content of the starting and forming substances in the gases leaving the Fischer-Tropsch synthesis reactor can be carried out by any known method, for example, gas-liquid chromatography.

The freshly prepared catalyst is ground to a fraction of 0.1-0.2 mm, 2.5 ml of the catalyst are loaded into a Fischer-Tropsch synthesis reactor and activated. After activation, the reactor is cooled in a stream of hydrogen or a hydrogen-containing gas to a temperature of less than 160 ° C and the stream of activating gas is replaced by a stream of a mixture of carbon monoxide and hydrogen at a space velocity of 1000 h ^-1 and the working pressure in the reactor is set to 2.0 MPa. Then the catalyst is heated to a temperature that allows to achieve maximum performance of the process for high molecular weight hydrocarbons in its presence.

After deactivation of the catalyst, which consists in reducing the conversion of CO and high molecular weight hydrocarbons under constant process conditions, the redox regeneration according to the present invention is carried out, with or without a preliminary reduction step with hydrogen-containing gas. After regeneration, the reactor is cooled in a stream of hydrogen to a temperature of less than 100 ° C and synthesis gas is supplied at a space velocity of 1000 h ⁻¹ and a working pressure in the reactor of 2.0 MPa. Then, the synthesis of hydrocarbons is carried out in the presence of a regenerated catalyst at a temperature necessary to achieve maximum performance for high molecular weight hydrocarbons.

The regeneration efficiency was estimated by the ratio of the CO conversion after regeneration to the initial CO conversion at the beginning of the synthesis (K _CO reg. / K _CO ex.) And to the CO conversion of the deactivated catalyst (K _CO reg. / K _CO des.), The ratio of the productivity values by macromolecular hydrocarbons after regeneration to the initial productivity at the beginning of the synthesis (Reg. / Fig.) and to the productivity of the deactivated catalyst (Reg. / Res.), the duration of the process after regeneration, during which the conversion of CO after regeneration exceeds the con ersiyu CO prior to regeneration (τ _K, h), and the processing time after the regeneration within a regeneration after performance of high molecular weight hydrocarbons exceeds the performance of high molecular hydrocarbons deactivated catalyst (τ _P, h).

The method is implemented in accordance with the specified examples.

Example 1

The catalyst And composition 4.0% Ni / [65% {(30% Co + 0.5% Re) / TiO ₂ } + 35% Hβ] was deactivated at a temperature of 250 ° C, a pressure of 2.0 MPa, H ₂ / CO = 2 after 230 hours of hydrocarbon synthesis from CO and H ₂ .

Redox regeneration of spent catalyst is carried out in two stages. At the first stage, oxidation is carried out by supplying air to the reactor with a space velocity of 1500 h ⁻¹ when heated to a temperature of 270 ° C at a rate of 3 ° C / min and keeping at this temperature for 3 hours. At the second stage, they restore by supplying a hydrogen-containing gas of composition 80 vol.% H ₂ +20 vol.% Not with a space velocity of 2000 h ^-1 when heated to a temperature of 500 ° C at a speed of 5 ° C / min, incubated for 3 hours

Example 2

The catalyst And composition 2.0% Fe / [40% {(30% Co + 0.5% Re) / (Al ₂ O ₃ -SiO ₂ )} + 60% Y] was deactivated at a temperature of 250 ° C, pressure 2 , 0 MPa, H ₂ / CO = 2 after 250 h of synthesis of hydrocarbons from CO and H ₂ .

The regeneration of the spent catalyst is carried out as follows. The deactivated catalyst is preliminarily reduced by feeding hydrogen at a space velocity of 3000 h ⁻¹ when heated to 400 ° C at a speed of 4 ° C / min and kept at this temperature for 1 h. Then, the reactor is cooled to a temperature of 250 ° C, the hydrogen supply is shut off. and carry out oxidation. Why air is supplied at a volumetric rate of 1000 h ⁻¹ _{, it is} held at a temperature of 250 ° C for 1 h and the catalyst is restored by supplying hydrogen at a volumetric rate of 3000 h ⁻¹ when heated to a temperature of 400 ° C at a rate of 2 ° C / min and holding for 1 h

Example 3

The catalyst And composition 4.0% Ni / [30% {(26% Co + 0.5% Re) / Al ₂ O ₃ } + 70% Hβ] was deactivated at a temperature of 250 ° C, a pressure of 2.0 MPa, H ₂ / CO = 2 after 220 hours of hydrocarbon synthesis from CO and H ₂ .

The spent catalyst is regenerated in three stages. At the stage for preliminary reduction of the catalyst, a hydrogen-containing gas of a composition of 50 vol.% H ₂ + 50 vol.% Ar is supplied with a space velocity of 1000 h ⁻¹ when heated to a temperature of 600 ° C at a speed of 5 ° C / min and kept at this temperature for 2 hours. Then the reactor is cooled to a temperature of 250 ° C, the hydrogen-containing gas supply is shut off and air is supplied for oxidation at a volumetric rate of 500 h ⁻¹ , it is held at 250 ° C for 2 hours. At the last stage, the catalyst is restored by supplying a hydrogen-containing gas. same composition with a bulk velocity of 4000 h ^-1 when heated to a temperature of 600 ° C at a speed of 3 ° C / min, incubated for 2 hours

Example 4

The catalyst A composition of 1.5% Fe / [30% {(27% Co + 0.5% Ru) / (Al ₂ O ₃ -ZrO ₂ )} + 70% Hβ] was deactivated at a temperature of 250 ° C, pressure 2 , 0 MPa, H ₂ / CO = 2 after 240 h of synthesis of hydrocarbons from CO and H ₂ .

The spent catalyst was regenerated in three stages. At the stage for preliminary reduction, a hydrogen-containing gas of 20% H ₂ + 80% N _{2 is} supplied with a space velocity of 5000 h ^-1 when heated to 300 ° C at a speed of 1 ° C / min and kept at this temperature for 5 hours. Then the reactor is cooled to a temperature of 200 ° C, the hydrogen-containing gas is shut off and air is supplied for oxidation at a volumetric rate of 2000 h ⁻¹ , it is held at 200 ° C for 4 hours. At the last stage, the catalyst is restored by supplying a hydrogen-containing gas of the same composition with a volumetric speed w 5,000 h ^-1 while heating to a temperature of 300 ° C at 1 ° C / min, held for 5 hours.

Example 5

Catalyst B of 10% Co / (90% Al ₂ O ₃ + 10% CeO ₂ ) was deactivated at a temperature of 250 ° C, a pressure of 2.0 MPa, H ₂ / CO = 2 after 270 h of synthesis of hydrocarbons from CO and H ₂ .

The spent catalyst is regenerated in two stages. At the stage of oxidation, air is supplied to the reactor at a volumetric rate of 500 h ⁻¹ when heated to a temperature of 230 ° C at a rate of 2 ° C / min and kept at this temperature for 5 hours. At the stage of reduction, hydrogen is supplied at a volumetric rate of 1000 h ⁻¹ when heated to a temperature of 450 ° C at a rate of 2 ° C / min, incubated for 2 hours

Example 6

Catalyst B of 10% Co / (88% ZrO ₂ + 12% La ₂ O ₃ ) was deactivated at a temperature of 250 ° C, a pressure of 2.0 MPa, H ₂ / CO = 2 after 260 hours of synthesis of hydrocarbons from CO and H ₂ .

The spent catalyst was regenerated in three stages. At the preliminary reduction stage, a hydrogen-containing gas of 40 vol.% H ₂ + 60 vol.% He is supplied with a space velocity of 4000 h ^-1 when heated to a temperature of 500 ° C at a speed of 3 ° C / min and kept at this temperature for 3 hours Then the reactor is cooled to a temperature of 240 ° C, the hydrogen-containing gas is shut off and air is supplied for oxidation at a volumetric rate of 1000 h ⁻¹ , it is held at a temperature of 240 ° C for 1 hour. At the reduction stage, a hydrogen-containing gas of the same composition with a volumetric speed of 3000 h ^-1 when heated to t temperatures of 600 ° C at a rate of 1 ° C / min, incubated for 1 h

Example 7

Catalyst B with a composition of 20% Co / (99% ZrO ₂ + 1% Y ₂ O ₃ ) was deactivated at a temperature of 250 ° C, a pressure of 2.0 MPa, H ₂ / CO = 2 after 250 h of synthesis of hydrocarbons from CO and H ₂ .

The spent catalyst was regenerated in two stages. At the stage of oxidation, air is supplied to the reactor with a space velocity of 2000 h ⁻¹ when heated to a temperature of 200 ° C at a rate of 1 ° C / min and kept at this temperature for 3 hours. At the stage of reduction, a hydrogen-containing gas of 50 vol% H _{2 is} fed + 50 vol% Ar with a space velocity of 3000 h ^-1 when heated to a temperature of 400 ° C at a speed of 4 ° C / min, incubated for 4 hours

Regeneration efficiency indicators achieved as a result of the implementation of the described examples are presented in table 1.

The conversion of CO after regeneration is 98-115 rel.% Of the values for the initial activated sample and increases by 1.33-2.19 times compared with the deactivated sample. For the prototype, these indicators are 92-98 rel.% And 1.15-1.23 times, respectively. The performance of the catalyst after regeneration is 100-114 rel.% Of the maximum value for the freshly restored catalyst and is 1.22-2.21 times higher than for the deactivated sample. The duration of the process after regeneration, during which the conversion of CO after regeneration exceeds the conversion of CO before regeneration, is 105-132 hours, the operating time of the catalyst after regeneration with performance values exceeding the values of the deactivated catalyst is 117-154 hours. According to the degree of recovery of activity after regeneration this invention is superior to the closest method for the regeneration of cobalt-containing catalysts, known in the art (RU 2456080 C2, 07.20.07.2012). Another advantage of this invention in comparison with the closest analogue is the implementation of the in situ regeneration method in a Fischer-Tropsch reactor.

This method of regeneration of a cobalt-containing catalyst for the synthesis of hydrocarbons can increase the catalytic activity of a deactivated catalyst, contributes to long-term operation while maintaining high values of conversion and productivity and is more efficient compared to regeneration methods known in the art.

Claims (4)

1. The method of regeneration of a cobalt-containing catalyst for the production of synthetic hydrocarbons according to the Fischer-Tropsch method, comprising oxidizing a deactivated catalyst by supplying air to the reaction zone of the reactor at a speed of 500-2000 h ^-1 , heating to a temperature of 200-270 ° C with a heating rate of 1-3 ° C / min, keeping at this temperature in a stream of air for 1-5 hours and subsequent recovery by feeding at a temperature of oxidation of a hydrogen-containing gas with a space velocity of 1000-5000 h ^-1 , heating to a temperature of 300-600 ° C with a speed of 1-5 ° C / min and in holding at a heating temperature in a stream of hydrogen-containing gas for 1-5 hours 2. The method according to claim 1, characterized in that before the redox regeneration, the deactivated catalyst is restored with a hydrogen-containing gas at a space velocity of 1000-5000 h ^-1 , heating to a temperature of 300-600 ° C at a speed of 1-5 ° C / min and keeping at this temperature for 1-5 hours 3. The method according to claim 1, characterized in that use a hydrogen-containing gas with a hydrogen content of from 20 to 100 vol.%. 4. The method according to claim 2, characterized in that the recovery is carried out using a hydrogen-containing gas of the same composition.