RU2261143C2 - Cobalt-based catalysts - Google Patents

Abstract

FIELD: industrial organic synthesis catalysts.

SUBSTANCE: cobalt-based Fischer-Tropsch catalyst includes porous carrier and metallic cobalt crystallites imbedded therein. Catalyst is characterized by content of cobalt in reducible form expressed as Ω wt % of the total catalyst mass before reduction. Catalyst in freshly reduced state is further characterized by Gauss distribution of cobalt crystallite size, surface area of metallic cobalt equal to 0.14 Ω to 1.03 Ω m²/g catalyst, and catalyst geometry providing stabilized efficiency factor in Fischer-Tropsch synthesis equal to 0.9 or higher.

EFFECT: achieved preparation of effective stabilized catalyst.

28 cl, 12 dwg, 17 tbl

Description

This invention relates to cobalt based catalysts. Specifically, the present invention relates to a cobalt-based Fischer-Tropsch catalyst, to a precursor of such a cobalt-based catalyst, to a method for producing a precursor of such a cobalt-based catalyst, to a method for producing such a cobalt-based catalyst, and to a method for producing hydrocarbons using such a catalyst based cobalt.

Known methods for producing cobalt-based catalyst precursors, which include impregnating a suspension of a catalyst support with a cobalt salt, drying the impregnated catalyst support and calcining the dried impregnated catalyst support to achieve the desired cobalt content on the support. The precursors obtained are then activated by reduction to obtain cobalt-based Fischer-Tropsch catalysts. These catalysts can exhibit a fairly high characteristic activity when used in Fischer-Tropsch synthesis reactions; however, it is not possible by known methods to easily obtain catalysts having enhanced or superior characteristic activity. Therefore, the aim of the present invention is to provide a Fischer-Tropsch catalyst having an increased initial and / or stabilized characteristic activity in Fischer-Tropsch synthesis reactions, as well as a method for producing such a catalyst.

According to a first aspect of the invention, there is provided a cobalt-based Fischer-Tropsch catalyst comprising a porous catalyst support and cobalt metal crystallites in said support and characterized by:

(i) a specific amount of cobalt in a reducible form, expressed as Ω wt.% based on the total weight of the catalyst before reduction;

(ii) in a freshly reduced state, cobalt metal crystallites characterized by a monomodal Gaussian distribution;

(iii) in a freshly reduced state, the surface area of the particles of metallic cobalt equal to from 0.14 Ω to 1.03 Ω m ² / g of catalyst;

(iv) in a freshly reduced state, the geometric form of the catalyst, which provides a stabilized activity factor in the Fischer-Tropsch reaction of 0.9 or more.

It has been unexpectedly found that the cobalt-based catalyst according to the first aspect of the invention exhibits increased initial and stabilized Fischer-Tropsch characteristic activity.

The term "stabilized activity factor in Fischer-Tropsch reactions" refers to the efficiency factor of a stabilized catalyst. A stabilized cobalt-based Fischer-Tropsch catalyst is defined as a catalyst that was fully conditioned during the Fischer-Tropsch reaction in suspension under real conditions of the Fischer-Tropsch reaction using ultra-pure synthesis gas, i.e. synthesis gas that does not contain in addition to H ₂ and CO contaminants, which can cause catalyst deactivation.

By “real Fischer-Tropsch reaction conditions” is meant reaction conditions of 225 ± 5 ° C. and a pressure of 20 bar,% conversion (H ₂ + CO) of 60 ± 10% when using a source gas containing about 50 vol.% H ₂ , about 25 vol.% CO, the rest is Ar, N ₂ , CH ₄ and / or CO ₂ .

By “freshly reduced” is meant a catalyst that has been activated and has not been used in the Fischer-Tropsch reaction.

In this specification, unless otherwise indicated, the weight of the catalyst refers to the weight of the calcined catalyst or the weight of the catalyst before reduction, that is, the weight of the catalyst before it is reduced.

Preferably, the surface area of the cobalt metal in the catalyst in the fresh state is equal to from 0.28 Ω to 0.89 Ω m ² / g of catalyst.

The size of most cobalt crystallites may be more than 8 nm.

It has been unexpectedly found that supported cobalt-based catalysts according to the invention with their large cobalt crystallites, that is, when the size of most cobalt metal crystallites is greater than 8 nm and therefore the surface area of the cobalt metal particles is small, do not undergo significant damage during oxidation. These catalysts for which the characteristic activity in the Fischer-Tropsch synthesis reactions at time 0 (i.e., at the beginning of the reaction) may be lower than the corresponding indicator for supported cobalt catalysts having smaller cobalt crystallites (i.e., which have most cobalt crystallites have a size less than 8 nm), have excellent or increased initial and stabilized characteristic activity, since new catalysts are deactivated to a much lesser extent than catalysis ry cobalt based on carriers, in which the size of the majority of crystallites of metallic cobalt is smaller than or equal to 8 nm.

The porous catalyst support may be calcined. Therefore, the supported cobalt-based catalyst according to the first aspect of the invention can be obtained by impregnating the porous catalyst support with cobalt or a catalyst precursor, in particular cobalt nitrate, calcining the impregnated carrier to obtain a cobalt-based catalyst precursor, and reducing the catalyst precursor to obtain a cobalt-based catalyst on carrier.

The catalyst carrier may be modified. The modified catalyst carrier may contain catalyst carrier particles containing a coating based on a modifying agent, which may be carbon or one or more metals of group IA and / or group IIA of the Periodic Table of the Elements, namely, one or more metals selected from Li, Na, K , Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, and mixtures thereof. It was found that when using a modified catalyst support, especially when there is a coating based on carbon or barium, the catalyst has a significantly increased initial characteristic activity when used in Fischer-Tropsch reactions.

When used to coat a barium support, the maximum amount of barium that can be used is determined by the effect of barium on the pore volume of the support, as well as on the solubility of the barium compound. The pore volume of the carrier must be large enough to hold the required amount of cobalt nitrate and obtain a cobalt-based catalyst carrier with the desired cobalt content. The solubility of the barium compound must be sufficient so that the barium compound can be added in one step of impregnation of the carrier. In practice, the maximum amount of barium can be 10 wt.% Based on the weight of the catalyst. The minimum amount of barium is determined by the minimum amount of barium, which leads to an increase in the stabilized characteristic Fischer-Tropsch activity of cobalt-based catalysts, and may be 0.2% by weight of the catalyst.

When used to obtain a carbon coating, the maximum amount of carbon that can be used to obtain an effective coating is determined by the effect of the carbon coating on the pore volume of the initial catalyst carrier, since the pore volume of the catalyst carrier determines the amount of cobalt introduced by impregnation into the carrier. This is especially important when a catalyst with a relatively high cobalt content is desired. Similarly, the minimum amount of carbon that can be used to obtain an effective coating is determined by the minimum amount of carbon that still provides the desired positive effect on the behavior of the cobalt catalyst in Fischer-Tropsch synthesis reactions. Thus, the maximum amount of carbon may be 40 g C / 100 g of the carrier, preferably 20 g C / 100 g of the carrier, even more preferably 10 g C / 100 g of the carrier, the minimum amount of carbon may be 0.1 g C / 100 g of the carrier preferably 0.5 g C / 100 g of carrier and more preferably 1.2 g C / 100 g of carrier.

In principle, coating the catalyst carrier particles can be accomplished by any suitable method. For example, a carbon-coated catalyst carrier can be prepared by coating the preformed porous particles of the catalyst carrier in the form of a uniform carbon layer according to the method described in EP 0681868.

According to a second aspect of the invention, there is provided a cobalt-based catalyst precursor comprising a porous catalyst support and cobalt oxide crystallites in this support, the precursor containing cobalt in a reducible form, and the amount of this cobalt is expressed as Ω wt.% Based on the weight of the catalyst, and this precursor is capable of producing a freshly reduced catalyst with a monomodal Gaussian crystallite distribution of cobalt metal in size with an area overhnosti particles of cobalt metal from 0,14 Ω m ² / g of catalyst to 1,03 Ω m ² / g catalyst and with the geometric shape factor value providing the catalyst activity in the Fischer-Tropsch reaction is 0.9 or more.

The porous catalyst support in the form of a precursor may be the same as according to the first aspect of the invention, and may be modified as described above.

According to a third aspect of the invention, there is provided a method for producing a cobalt-based catalyst precursor, comprising:

at the stage of carrier impregnation, impregnation of the particles of the porous modified catalyst carrier with a cobalt salt and partial drying of the impregnated carrier to obtain a partially dried impregnated carrier and

at the calcination step, calcining the partially dried impregnated support to obtain a cobalt-based catalyst precursor, the precursor comprising particles of a calcined porous modified catalyst support containing cobalt oxide crystallites, contains a certain amount of cobalt in a reducible form and this amount is expressed as Ω wt.% based on the mass of the catalyst, and said precursor is capable of producing a freshly reduced catalyst, with monomodal m Gaussian distribution of crystallites of metallic cobalt in size with a surface area of particles of metallic cobalt from 0.14 Ω m ² / g of catalyst to 1.03 Ω m ² / g of catalyst and with a geometric shape that provides the value of the catalyst activity factor in the Fischer-Tropsch reactions, equal to 0.9 or more.

The obtained cobalt-based catalyst precursor is reduced to obtain a cobalt-based catalyst that is characterized by increased or excellent initial and stabilized catalytic activity.

According to a fourth aspect of the invention, there is provided a method for producing a cobalt-based Fischer-Tropsch catalyst, which comprises:

at the stage of carrier impregnation, impregnation of the particles of the porous modified catalyst carrier with a cobalt salt and partial drying of the impregnated carrier to obtain a partially dried impregnated carrier;

in the calcining step, calcining the partially dried impregnated support to obtain a cobalt-based catalyst precursor, the precursor comprising calcined porous modified catalyst support particles containing cobalt oxide crystallites and

in the reduction step, recovering the cobalt-based catalyst precursor to obtain a cobalt-based catalyst which (i) contains a certain amount of cobalt in a reducible form, this amount being expressed as Ω wt.% based on the total weight of the catalyst before reduction; (ii) in a freshly reduced state is characterized by a Gaussian distribution of crystallite sizes of metallic cobalt; (iii) in a freshly reduced state has a surface area of particles of metallic cobalt from 0.14 Ω to 1.03 Ω m ² / g of catalyst; and (iv) in a freshly reduced state, has a geometry that allows one to obtain a stabilized activity factor in Fischer-Tropsch reactions of 0.9 or more.

The cobalt salt may be cobalt nitrate Co (NO ₃ ) ₂ · 6H ₂ O.

The modified catalyst support may be any commercially available porous oxide catalyst support such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), mixed silica — alumina (SiO ₂ · Al ₂ O ₃ ), titanium oxide ( TiO ₂ ) and magnesium oxide (MgO) containing a coating based on carbon or one or more metals of group IA and / or group II of the Periodic Table of the Elements as a modifying agent, as described above.

The carrier may be a protected modified carrier containing, for example, silicon as a modifying component, as described in WO 99/42214.

The methods according to the third and fourth aspects of the invention may, if necessary, include obtaining a modified carrier, that is, they may include modifying the particles of the carrier by coating them with a coating based on a modifying agent.

The impregnation of the carrier can, in principle, be carried out by any known method of impregnation, for example by impregnation in the wet state or in suspension. Similarly, calcination can be carried out in any known means, for example in a fluidized bed, in a fixed layer, in a furnace, in a rotary kiln and / or in a calciner, preferably at temperatures between 150 ° C and 400 ° C, more preferably between 200 ° C and 300 ° C. In particular, calcination can be carried out in accordance with the method described in application US 60/168604. Calcination can be carried out in a fluidized bed, as described in application US 60/168604.

The cobalt-based catalyst precursor can be obtained by a two-stage method of suspension impregnation, drying and calcination. The two-stage method includes, in the first stage, impregnating the catalyst carrier with cobalt salt, partially drying the impregnated carrier, and calcining the partially dried carrier to obtain a calcined product, and then, in the second stage, impregnating the calcined product with cobalt salt, partially drying the impregnated product and calcining the partially dried product to obtain the precursor catalyst.

The method may include partial restoration of the calcined product before impregnation with a cobalt salt. Partial reduction of the calcined product can be carried out at a temperature of from 100 ° C to 300 ° C, more preferably at a temperature of from 130 ° C to 250 ° C. Partial reduction of the calcined product can be carried out by contacting the calcined product with a gas containing hydrogen and / or carbon monoxide as a gaseous reducing agent.

According to a fifth aspect of the invention, there is provided a method for producing a cobalt-based catalyst precursor, which comprises:

in the first stage of impregnation of the support, impregnation of the particles of the porous catalyst support with a cobalt salt and partial drying of the impregnated support, and at the calcination step, calcining the partially dried impregnated support to obtain a calcined product;

at least partial recovery of the calcined product; and then

in the second stage of impregnation of the carrier, impregnation of at least partially reduced product with cobalt salt and partial drying of the impregnated product and in the calcination step, calcining the partially dried impregnated product to obtain a cobalt-based catalyst precursor, this precursor comprising a calcined porous catalyst carrier with cobalt oxide crystallites contained in the carrier contains a certain amount of cobalt in a reducible form, and this amount expressed as Ω wt.% based on the total weight of the precursor, while the specified precursor is capable of producing a freshly reduced catalyst, characterized by a monomodal Gaussian distribution of crystallite sizes of metallic cobalt, a surface area of particles of metallic cobalt equal to 0.14-1,03 Ω m ² / g of catalyst and geometry, which provides the value of the stabilized activity factor in the Fischer-Tropsch synthesis reactions equal to 0.9 or more.

As indicated above, the obtained cobalt-based catalyst precursor is reduced to obtain a cobalt-based catalyst that is characterized by increased or excellent initial and stabilized catalytic activity.

According to a sixth aspect of the present invention, there is provided a method for producing a cobalt-based catalyst, which comprises:

in the first stage of impregnation of the support, impregnation of the particles of the porous catalyst support with a cobalt salt and partial drying of the impregnated support, and at the calcination step, calcining the partially dried impregnated support to obtain a calcined product;

at least partial recovery of the calcined product; and then

in the second stage of impregnation of the carrier, impregnation of at least partially reduced product with cobalt salt and partial drying of the impregnated product and in the calcination step, calcining the partially dried impregnated product to obtain a cobalt catalyst precursor, this precursor comprising a calcined porous catalyst carrier with cobalt oxide crystallites contained in the carrier, contains a certain amount of cobalt in a reducible form, and this amount it is expressed as Ω wt.% based on the total weight of the precursor, while the specified precursor is capable of producing a freshly reduced catalyst characterized by a monomodal Gaussian distribution of crystallite sizes of metallic cobalt, a surface area of particles of metallic cobalt equal to 0.14-1,03 Ω m ² / g of catalyst and geometry, which provides a value of the stabilized activity factor in Fischer-Tropsch synthesis reactions equal to 0.9 or more; and

at the reduction stage, reduction of the cobalt-based catalyst precursor to obtain a cobalt-based catalyst, which (1) contains a certain amount of cobalt in a reducible form, this amount being expressed as Ω wt.% based on the total weight of the catalyst before reduction; (ii) in a freshly reduced state is characterized by a Gaussian distribution of crystallite sizes of metallic cobalt; (iii) in a freshly reduced state has a surface area of particles of metallic cobalt from 0.14 Ω to 1.03 Ω m ² / g of catalyst; and (iv) in a freshly reduced state, has a geometry that allows the factor of stabilized activity in Fischer-Tropsch reactions to be equal to 0.9 or more.

The catalyst carrier may be a modified catalyst carrier, as described above. The carrier may even be a protected modified catalyst carrier, as described above. The methods in accordance with the fifth and sixth aspects may, if necessary, include obtaining a modified carrier.

The cobalt salt used in the methods according to the fifth and sixth aspects of the invention may be cobalt nitrate.

Impregnation of the carrier, drying and calcination can, in particular, be carried out according to the method described in application WO 00/20116. The preparation of the precursor may therefore include a two-stage suspension impregnation, drying and calcination, as described in WO 00/20116, this method depends on the desired content of the active component and the pore volume of the porous oxide catalyst support.

The impregnation and drying of the carrier is usually carried out in a conical vacuum dryer with a rotating screw or in a drum vacuum dryer.

The catalyst precursor may contain 5-70 g Co / 100 g of carrier, preferably 20-50 g Co / 100 g of carrier.

During any stage of impregnation in the suspension, a water-soluble salt of palladium (Pd) or platinum (Pt) or a mixture of such salts may be added as a dopant to promote cobalt recovery. It is preferable to add a dopant in a weight ratio of palladium, platinum or a mixture of palladium and platinum and cobalt from 0.01: 100 to 0.3: 100.

The present invention also relates to a cobalt-based catalyst obtained by the method according to the fourth or sixth aspect of the invention, and to a catalyst precursor obtained by the method according to the third or fifth aspect of the present invention.

The invention also covers hydrocarbons obtained by the above method.

The invention will now be described in more detail with reference to examples and drawings.

Figure 1 shows the progress of the process of deactivation of catalyst B during the Fischer-Tropsch synthesis and the effect of introducing a protective layer of ZnO in the initial APG on the decontamination process.

Figure 2 shows the rate of deactivation of catalyst B during the Fischer-Tropsch CSTR microsynthesis due to the introduction of H ₂ S in an amount of 190 parts / billion. and a space velocity of 2.22 m ³ / (kg of catalyst · h).

Figure 3 shows the overlap of the profiles of the factor relative characteristic activity of 5 experiments on the synthesis of CSTR Fischer-Tropsch in micro suspensions with catalyst B.

Figure 4 shows a bimodal Gaussian crystallite size distribution in freshly reduced catalyst B.

Figure 5 shows a bimodal Gaussian possible distribution of the content of metallic cobalt in freshly reduced catalyst B.

Figure 6 shows the effect of oxidation as a deactivation factor during the Fischer-Tropsch synthesis in suspension under real reaction conditions in the presence of catalyst B.

Figure 7 shows the relationship between the factors of relative characteristic activity (Fischer-Tropsch) and the specific surface area of cobalt metal particles in freshly reduced catalysts on a carrier with 19.5 wt.% Cobalt, characterized by a monomodal Gaussian crystallite size distribution.

Figure 8 shows the relationship between the factors of relative characteristic activity (Fischer-Tropsch) and the specific surface area of cobalt metal of freshly reduced cobalt-based catalysts on a support, characterized by a monomodal Gaussian crystallite size distribution.

Figure 9 shows the superposition of recovery profiles at the programmed temperature of the fully calcined catalyst precursors B and catalyst F.

Figure 10 shows the imposition of recovery profiles at the programmed temperature of the fully calcined catalyst precursors B and catalyst E.

11 shows an overlay of programmed temperature recovery profiles of fully calcined catalyst precursors B and catalyst G.

12 shows the correlation between the observed factors of the initial relative characteristic activity of the catalyst E - CO / Al ₂ O ₃ in the synthesis reaction in a Fischer-Tropsch suspension and the total content of Co (NO ₃ ) ₂ · 6H ₂ O in m ^{2 of} SASOL Germany GmbH carrier Puralox SCCa 5/150.

Example 1

Catalyst B (30 g Co / 100 g Al ₂ O ₃ ) (not according to the invention).

1.1. Receiving.

The platinum-promoted catalyst was obtained on a carrier — preformed Al ₂ O ₃ — trademark of Puralox SCCa 5/150, SASOL Germany GmbH, in accordance with the method of impregnation in aqueous suspension and vacuum drying, followed by calcination in a fluidized bed; as in Example 1 of WO 00/20116 or as one of the catalysts D, E, G or H in US application 60/168604.

For use in a continuously stirred reactor (CSTR) for Fischer-Tropsch synthesis, this calcined product was reduced and waxed on it using the following procedure:

27.5 g of the catalyst was reduced with pure hydrogen at a pressure of 1 bar (space velocity ≥200 ml H ₂ / g of catalyst / hour), at which time the temperature was raised from 25 ° C to 380-425 ° C at a speed of 1 ° C / min, after which the temperature was kept constant at 380-425 ° C for 16 hours.

The reduced catalyst was allowed to cool to room temperature when hydrogen was replaced with argon and the catalyst was discharged into Fischer-Tropsch molten wax in an argon atmosphere. This wax coated catalyst was placed in a reactor.

The catalyst had the following characteristics: composition 30 g Co / 100 g Al ₂ O ₃ , the mass of the catalyst (before reduction) was 153.8 g, the weight of the freshly reduced catalyst was 133.8 g.

1.2. Fischer-Tropsch synthesis reaction in CSTR.

The test (number 106F) for the Fischer-Tropsch reaction in the CSTR was carried out using catalyst B. This test lasted about 90 days under the following conditions:

The temperature in the reactor: 220.5 ° C Reactor pressure: 20.3 bar Catalyst loading: 20.8 g Volumetric rate (H ₂ + CO) 2169 ml / g of catalyst / h APG space velocity 2452 ml / g of catalyst / h,

where APG stands for Arge pure gas, that is, commercial synthesis gas obtained from Schïmann-Sasol (Pty) Limited in Sasolburg, South Africa, using coal gasification followed by purification of Rectisol (trademark).

The composition of the source gas:

H ₂ : 49.1 vol.% WITH: 25.9 vol.% CH ₄ : 9.3 vol.% CO ₂ : 0.5 vol.% Ar: 15.2 vol.%

The results of the reaction (i.e., experiment 106F) led to the following conclusions:

- the initial RIAF is 2.6, a _i = 2.6;

- the profile of characteristic activity (ex t _i , where t = time) can be divided into three phases, characterized by two break points.

The relative (Fischer-Tropsch) characteristic activity factor (RIAF) was determined as follows.

The Fischer-Tropsch catalyst based on cobalt was characterized in the Fischer-Tropsch synthesis process:

r _FT = Z moles of CO, converted into Fischer-Tropsch synthesis products per gram of catalyst per second, at T = γ Kelvin at the following partial pressure:

P _HZ = ν bar

P _CO = τ bar

R.I.A.F. is equal to:

RIAF = [Z (1 + 1.82 τ) ² ] / [49480.9 e ^{(-11113.4 / γ)} ντ]

The initial Fischer-Tropsch characteristic activity (a _i ) of a cobalt-based catalyst in suspension is determined as follows:

a _i = RIAF after 15 hours (i.e., t _i = initial time) of continuous gradientless synthesis in suspension:

220 ° C, 20 bar,% conversion (H ₂ + CO) above 50%, the initial gas mixture had a composition of about 50 vol.% H ₂ and about 25 vol.% CO and the rest was Ar, N ₂ , CH ₄ and / or CO ₂ .

It can be concluded that all four phases of deactivation (namely, phases I, II, III, and IV) completely describe the profile of the characteristic activity of catalyst B under real synthesis conditions in a Fischer-Tropsch suspension.

1.2.1. Phase IV decontamination is part of an experiment that lasts after initiation for 40-60 days under real Fischer-Tropsch synthesis conditions.

This decontamination is a continuous and irreversible process.

Sulfur poisoning dominates during phase IV decontamination.

The correlation between the density of the active sites of the Fischer-Tropsch catalyst and the RIAF is as follows.

Consider the effect of a well-conditioned cobalt-based catalyst in suspension in a CSTR, that is, only minor sulfur poisoning is responsible for catalyst deactivation.

Assumptions:

- sulfur-containing compounds present in pure synthesis gas are all monatomic with respect to sulfur;

- the poisoning coefficient is one sulfur atom per active site;

- sulfur absorption is quantitative and occurs selectively on metallic cobalt.

Nomenclature:

b = the observed linear deactivation rate of a well-conditioned cobalt-based catalyst, expressed in RIAF units, which decreased over an hour;

c = sulfur content in pure synthesis gas, expressed in volume parts per billion;

X = feed rate of pure synthesis gas, expressed in m ³ / kg of catalyst / hour.

Thus, moles of sulfur per kg of catalyst per hour are introduced into the CSTR (XB 4.459 × 10 ^-8 ). Therefore, RIAF b corresponds to the density of active sites (Xb 4.459 × 10 ^-8 ) moles per kg of catalyst. One RIAF unit corresponds to [(xv 4.459 × 10 ^-11 ) / b] moles of sites / kg of catalyst.

During the Fischer-Tropsch synthesis experiment WPP54, APG was used, which was not purified by passing through adsorbents and a significant phase IV deactivation was observed (Figure 1). After the introduction of an S-protective ZnO layer, the characteristic activity in the Fischer-Tropsch synthesis stabilized, which indicates that the deactivation observed before the introduction of the ZnO layer was mainly caused by sulfur.

A sample of the conditioned catalyst was taken after about 120 days of operation, that is, after stabilization and conditioning, from the Fischer-Tropsch reactor, where an experiment was carried out which was carried out using the initial synthesis gas, which was passed through a sulfur-absorbing ZnO layer. This catalyst sample was tested in a laboratory microCSTR for the degree of deactivation with the introduction of a known amount of H ₂ S during this experiment, using a system with a tube for penetration (Figure 2). A deactivation rate during phase IV of 1.09 × 10 ⁻³ units was observed. RIAF / h at a gas volumetric velocity (containing 190 v / v H ₂ S) of 2.22 m ³ / (kg cat. · Hour). Using the aforementioned correlation for this data, it can be determined that the RIAF unit corresponds to 1.72 × 10 ⁻⁵ ) mol sites / g of catalyst.

1.2.2. The decontamination phase III is part of the experiment, which takes place approximately 5- (40-60) days after the start, under real conditions of the Fischer-Tropsch synthesis reaction in suspension.

At this stage, decontamination is caused by sulfur poisoning as in 1.2.1. In addition, there is a slow oxidation of crystallites of metallic cobalt, the size of which is less than the threshold value. This particular decontamination mechanism is described: ex t _i oxidation.

“Threshold size value” is defined as the maximum crystallite diameter of the available crystallites of metallic cobalt, which will be oxidized under real Fischer-Tropsch synthesis conditions.

Further, it is assumed that crystallites of metallic cobalt in the case of reduced catalysts based on cobalt are hemispherical, which allows us to assume that

- surface area of one crystallite = (px ² ) / 2;

- the volume of one crystallite = 0,083рх ³ , where

x = diameter of the proposed hemispherical crystallites and also denotes the crystallite size.

Although the oxidation of bulk particles of metallic cobalt to CoO or Co ₃ O ₄ under typical conditions of the Fischer-Tropsch synthesis is unlikely from a thermodynamic point of view, there are literature data on the possible oxidation of a cobalt-based catalyst during the Fischer-Tropsch reaction.

In the case of catalyst B, we can assume the existence of the following characteristic deactivation parameters in the Fischer-Tropsch synthesis reaction:

Table 1 Temperature (° C) The degree of oxidation ex t _i (% a _i ) The deactivation rate associated with ex t _i oxidation (RIAF units / day) 220 fifteen 1.0 × 10 ^-2

1.2.3. Phase II deactivation is part of the experiment, proceeding from the onset (t _i ) to about 5 days after the onset, under the actual conditions of the Fischer-Tropsch reaction. At this stage of decontamination, there are:

- sulfur poisoning in accordance with 1.2.1;

- ex t _i oxidation in accordance with 1.2.2.

In addition to these two decontamination mechanisms, reductive poisoning may be thought to occur. By “reductive poisoning” is meant that reduction can be carried out in an in situ treatment with pure hydrogen at a pressure of 20 bar and a temperature of 220 ° C., that is, the usual Fischer-Tropsch reaction conditions. The following two known decontamination mechanisms may occur:

- shielding active sites containing hydrocarbon residues (i.e. clogging) removed by hydrolysis. According to this mechanism, treatment with pure hydrogen should restore the initial Fischer-Tropsch synthesis rates, and this is facilitated by the presence of ruthenium as a promoter, that is, the use of its known strength in the hydrolysis process. The ability to regenerate deactivated catalysts by treatment with hydrogen can be problematic on supported metal cobalt, that is, in the absence of ruthenium in Fischer-Tropsch catalysts;

- reductive poisoning of the Fischer-Tropsch catalysts based on cobalt on a carrier with contaminants other than sulfur-containing compounds, for example NH ₃ and / or HCN, contained in the synthesis gas. This theory of reductive poisoning, which lasts for approximately 5 days under the influence of the actual conditions of the Fischer-Tropsch synthesis in the CSTR, was tested in experiments 35F, 41F, 215F, 317s and 319s. Test No. 41F was carried out in the presence of catalyst B. This test was carried out under real synthesis conditions in a CSTR, then the following two stages of in situ treatment with pure hydrogen were carried out.

Hydrogen Treatment Step A:

After 178.3 hours of operation, the source gas (i.e., APG containing 15 vol.% Ar) was replaced with pure hydrogen (feed rate 0.5 dm ³ / min) at a reactor pressure of 20 bar and a reactor temperature of 220 ° C. This treatment step with pure hydrogen was continued for 10.2 hours, after which pure hydrogen was replaced with the same synthesis gas (i.e., APG containing 15 vol.% Ar). The first analysis of the characteristics of the catalyst in the implementation of the Fischer-Tropsch reaction (stage A treatment with hydrogen) was carried out 1.8 hours after the repeated introduction of synthesis gas.

Hydrogen Treatment Step B:

After 471.1 hours of operation, the source gas (i.e., APG containing 15 vol.% Ar) was replaced with pure hydrogen (feed rate 0.5 dm ³ / min) at a pressure in the reactor of 20 bar and a temperature in the reactor of 220 ° C. This treatment step with pure hydrogen was continued for 39 hours, after which pure hydrogen was replaced with the same synthesis gas (i.e. APG containing 15 vol.% Ar). The first analysis of the characteristics of the catalyst in the implementation of the Fischer-Tropsch reaction (stage A treatment with hydrogen) was performed 2.0 hours after the repeated introduction of synthesis gas.

Analysis of the data obtained during the experiment 41F, allowed to draw the following conclusions:

- the characteristic activity of catalyst B, the implementation of stages A and B of the hydrogen treatment are similar to those of phase II deactivation (i.e. ex t _i ). If we accept this position, we can conclude that reductive poisoning plays a significant role during phase II decontamination, as was observed during experiment 41F and

- extrapolation of the results, provided that the RIAF is 3.0 at the time instant equal to 0. Thus, we can conclude that the extrapolated RIAF at the time moment equal to 0, which corrects any deactivation caused by phases II, III and IV, is equal to 3.0.

It is known from the literature that catalyst reduction can also be carried out by treatment with an inert gas under typical conditions of the Fischer-Tropsch reaction (i.e. 220 ° C and 20 bar). Thus, it turned out that if the presence of hydrogen during in situ reduction of catalyst B was not necessary and the blowing step was sufficient, then it is possible to consider an Al ₂ O ₃ support with a pore diameter exceeding 12 nm instead of the preferred support Puralox SCCa 5/150 from SASOL Germany GmbH. This in situ reduction step with an inert gas was carried out, but could not be repeated. It was concluded that the presence of hydrogen is necessary during catalyst reduction, which is consistent with published observations and confirms the view that catalyst contamination may not cause catalyst poisoning.

Based on Figure 3, analysis of the results of experiments 29F, 106F, 215F, 317s and 319Ss, that is, experiments on the reaction with catalyst B in real conditions of the Fischer-Tropsch synthesis showed the following:

- Recovery poisoning was not always observed and depended on specific periods of time. The characteristics of the catalysts during experiments 29F and 106F can be considered typical of all experiments carried out in suspension in a Fischer-Tropsch microCSTR for a long time using APG as synthesis gas. Experiments 317s, 319s, and 215F were performed over a significantly shorter period of time, also using APG as synthesis gas. It was concluded that reductive poisoning during phase II deactivation should not be associated with the process of contamination of active sites with high molecular weight hydrocarbons. Therefore, preference is given to explaining reductive poisoning by the presence of contaminants in the feed gas, for example, NH ₃ and / or HCN.

- If we assume that during experiments 317s, 319s and 215F, there is no reductive poisoning in phase II deactivation, the RIAF at extrapolated time point 0 is 2.9. This value of 2.9 for extrapolated time point 0 confirms the value of 3.0 mentioned earlier, that is, the extrapolated RIAF value at time 0, which neutralizes any deactivation caused by phases II, III and IV.

1.2.4. The decontamination phase I is part of the experience of conducting the Fischer-Tropsch reaction until the initial time (i.e., t _i ).

At this stage of decontamination, the following occur:

- sulfur poisoning according to 1.2.1 (i.e. phase IV);

- oxidation ex t _i according to 1.2.2 (i.e. phase III decontamination);

- recovery poisoning according to 1.2.3 (i.e. phase II decontamination).

If an extrapolated correction is made for all three of these decontamination mechanisms when the Fischer-Tropsch reaction is used in the synthesis of catalyst B during the synthesis, it turns out that the RIAF at time 0 is 3.0. However, as indicated previously in section 1.2.1, the RIAF unit corresponds to 1.72 × 10 ⁻⁵ mol sites / g of catalyst. Consequently, the density of active sites at time 0 is 5.16 × 10 ⁻⁵ mole of cobalt atoms on the surface / g of catalyst B, and this explains the effect of deactivation phases II, III, and IV under real synthesis conditions in CSTR.

Assuming that one surface atom of metallic cobalt occupies an area of 0.0662 nm ² , the density of active sites equal to 5.16 × 10 ^-5 per g of catalyst will correspond to a surface area of metallic cobalt of 2.06 m ² / g of catalyst . Consequently, the surface area of cobalt at time 0, equal to approximately 2.1 m ² / g of catalyst B, explains the effect of deactivation phases II, III and IV under real synthesis conditions in CSTR.

However, the interpretation of the chemisorption (H ₂ ) analysis of the freshly reduced catalyst B led to the conclusion that the surface area of cobalt in the freshly restored (i.e., at time 0) catalyst B is 11.9 m ² / g of catalyst.

Catalyst B deactivation phase I is associated with significant catalyst induction (in addition to the three hypothetical deactivation mechanisms associated with deactivation phases II, III, and IV), which is equivalent to a loss of 11.9-2.1 = 9.8 m ² of cobalt surface area per gram of catalyst. Based on the studies published by M össbauer E mission S pectroscopy (MES ) and T emperature G ravimetric A nalysis (TGA ) appeared hypothesis of the mechanism almost instantaneous oxidation of cobalt crystallites whose size is much smaller than the threshold value.

This oxidation of the catalyst is thus different from the previously indicated oxidation ex t _i and is referred to as pre t _i oxidation.

The full effect of this pre t _i oxidation on catalyst B was evaluated as follows. The cobalt surface area in the freshly reduced catalyst is 11.9 m ² / g of catalyst. However, one cobalt atom occupies an area equal to 0.0662 nm ² . Thus, the freshly reduced catalyst B contains 2.98 x 10 ^-4 moles of active Fischer-Tropsch sites per gram of catalyst. The RIAF unit corresponds to 1.72 × 10 ^-5 mole sites per gram of catalyst, as described in section 1.2.1. Thus, the RIAF of the freshly reduced catalyst B (i.e., the RIAF at time 0) is 17.3. Therefore, only pre t _i oxidation is responsible for the loss of 17.3-3.0 = 14.3 RIAF units in the case of catalyst B, which corresponds to a loss of 9.8 m ² of cobalt surface area per gram of catalyst.

1.3. Description of the size distribution of cobalt crystallites in the case of freshly reduced catalyst B.

1.3.1. Known Characteristics of Catalyst B.

Based on the results of the analysis of H ₂ chemisorption by freshly reduced catalyst B, the following conclusions were drawn:

- The surface area of metallic cobalt = 11.9 m ² / g of catalyst.

- The most common crystallite size of metallic cobalt is 6 nm, this value was also confirmed by high resolution transmission electron microscopy (HRTEM).

The most common crystallite size of metallic cobalt, equal to 6 nm for the freshly reduced catalyst B, was also confirmed by the magnetic method. It was determined that 30 wt.% Of all metallic cobalt in the freshly reduced catalyst B is contained in crystallites whose size exceeds 15 nm.

Therefore, any model considered as a likely description of the size distribution of cobalt metal crystallites in freshly reduced catalyst B should also give an idea of the following set of known characteristics:

- the most common crystallite size of metallic cobalt is 6 nm;

- the surface area of metallic cobalt is 11.9 m ² / g of catalyst;

- the content of metallic cobalt in crystallites larger than 15 nm is equal to 30 wt.%.

1.3.2. A model for describing the size distribution of crystallites of cobalt metal for a freshly reduced catalyst B.

To determine the model of the possible crystallite size distribution (CSD), the following list of standard possible types of distribution was used:

a) a monomodal chi-quadratic distribution;

b) F-distribution;

c) monomodal Gaussian distribution;

d) monomodal asymmetric normal distribution;

e) bimodal Gaussian distribution.

An assessment of the possibilities a) -e) led to the conclusion that it is impossible to satisfy all three characteristics in section 1.3.1 at the same time using the model of the monomodal size distribution of crystallites.

Option e), i.e. a bimodal Gaussian distribution, is possible and it can be described by the following mathematical equation:

Where

количество кристаллитов, размер которых равен х нм;i)

the number of crystallites whose size is x nm;

ii)

iii) 0≤β≤1

iv)

нежелательно с физической точки зрения (то есть кристаллиты с отрицательным диаметром). Для разрешения этой ситуации использовали ограничение максимально достижимой (то есть отрицательной) величины:* Note:

undesirable from a physical point of view (i.e. crystallites with a negative diameter). To resolve this situation, we used the limitation of the maximum attainable (i.e., negative) value:

Proposed Limit:

Theorem: 99% of the number described

will be in the range (μ _i -2,67σ _i ,) ≤х≤ (μ _i + 2,56σ _i ) Thus: maximum permissible value

σ _i = (μ _i / 2.67)

Consequently: 0 <σ _i ≤ (μ _i / 2,67) and μ _i > 0

2.1.1. The surface area of the particles of metallic cobalt in accordance with the bimodal Gaussian size distribution of crystallites.

.In accordance with the symbol, the number of crystallites of size x

.

However, the surface area of a single crystallite with a diameter of x nm is equal to:

[(πx ² ) / 2] (nm) ²

Thus, the total surface area of crystallites with a diameter of x nm is equal to:

Therefore, the total metal surface area of the total number of cobalt crystallites is equal to:

In addition, the volume of a single crystallite with a diameter of x nm is equal to: (0,083πх ³ ) (nm) ³ . Thus, the volume of crystallites with a diameter of x nm is:

However, the cobalt density is 8.9 g / ml. Therefore, the total mass of cobalt in crystallites with a diameter of x nm is equal to:

The total mass of cobalt contained in all crystallites of metallic cobalt is:

Equations 4 and 6 make it possible to determine that the surface area of metallic cobalt per gram of metallic cobalt is equal to:

Using equation (7) for a freshly reduced catalyst B makes it possible to determine that the surface area of cobalt per gram of catalyst will be equal to:

Equation (8) shows that 1 g of the catalyst contains 0.195 g of cobalt, 75% of which is recovered during the reduction stage. Therefore, 1 g of catalyst B contains only 0.146 g of cobalt metal.

1.3.2.2. Part of the total amount of cobalt metal contained in crystallites whose size exceeds d nm (X _d )

Equation (6) leads to the equation:

1.3.2.3. Determination of model parameter values applicable to freshly recovered catalyst B.

Два параметра модели μ₁ и σ₁ определяют положение и ширину первого пика соответственно. Два параметра модели μ₂ и σ₂ выполняют ту же функцию в случае второго пика, в то время как β обозначает относительные размеры пика. При применении этой модели для свежевосстановленного катализатора В μ₁ равен 6 согласно требованию, что наиболее распространенным размером кристаллита является 6 нм, как описано выше. Остальные параметры модели, а именно σ₁, μ₂ и β, были выбраны на основе следующих критериев соответствия модели:The proposed bimodal Gaussian CSD model contains five parameters, namely:

Two model parameters μ ₁ and σ ₁ determine the position and width of the first peak, respectively. Two model parameters μ ₂ and σ ₂ perform the same function in the case of the second peak, while β denotes the relative dimensions of the peak. When applying this model to a freshly reduced catalyst, B μ ₁ is 6 according to the requirement that the most common crystallite size is 6 nm, as described above. The remaining parameters of the model, namely σ ₁ , μ ₂ and β, were selected on the basis of the following criteria for model compliance:

i)

(ref: equation 8)

ii)

(ref: equation 9)

Thus, a model of a bimodal size distribution of crystallites of metallic cobalt is proposed for freshly reduced catalyst B. A model of a bimodal Gaussian crystallite size distribution provides a reasonable description of this crystallite size distribution, verified by the known characteristics indicated above. The following model parameters were selected:

μ ₁ = 6.0

σ ₁ = 1.0

μ ₂ = 16.0

σ ₂ = 5.0

β = 0.976

The validity of this set of model parameter values is illustrated in Table 2.

table 2   Desired value Model Prediction The most common crystallite size 6 nm 6 nm The surface area of metallic cobalt 11.9 m ² / g cat. 11.9 m ² / g cat The content of metallic cobalt (wt.%) In crystallites larger than 15 nm thirty% 30.9%

A visual illustration of such a crystallite size distribution model is shown in FIGS. 4 and 5.

I.4. Coordination of the profile of the characteristic Fischer-Tropsch activity (i.e. 2.1) and the size distribution of cobalt crystallites (i.e. 1.3) for catalyst B. We studied the relationship between the characteristics of the catalyst during oxidation (both pre and ex t _i oxidation) for catalyst B and the crystallite distribution of cobalt metal in size at time 0. The goal was to find a crystallite size distribution of cobalt metal in sizes that would provide absolute oxidation resistance under real conditions of Fischer synthesis Ra Tropsch. Section 1.2 concluded that 9.8 m ² of cobalt surface per gram of catalyst were lost due to pre t _i oxidation (i.e. during phase I deactivation) and that (0.15 a _i ) RIAF units are lost due to ex t _i oxidation at 230 ° C (i.e. during phases II and III of decontamination).

However, one RIAF unit corresponds to 1.72 × 10 ^-5 mole of cobalt atoms on the surface per gram of catalyst, and one cobalt atom occupies an area of 0.0662 nm ² (presumably) and a _i = 2.8 (based on a large number of experiments on Fischer-Tropsch synthesis in the presence of catalyst B). Accordingly, from the values of the cobalt surface area at time 0 equal to 11.9 m ² / gram of catalyst, 9.8 m ² were oxidized during the induction of the catalyst (i.e. phase I deactivation) followed by oxidation of another 0.29 m ² the time of phase II and phase III deactivation due to the implementation of the Fischer-Tropsch synthesis in real conditions.

Equation (8) was used to explain these values — 9.8 m ² / g of catalyst and 0.29 m ² / g of catalyst, which were lost respectively during pre t _i oxidation and ex t _i oxidation. The following assumptions were made. Cobalt metal crystallites smaller than λ nm are oxidized during catalyst induction (i.e. decontamination phase I) and cobalt crystallites whose size is between λ and δ nm are oxidized during catalyst conditioning (i.e. deactivation phases II and III). Thus,

Given that μ _i = 6.0, σ ₁ = 1.0, μ ₂ = 16.0, σ ₂ = 5.0 and β = 0.976, we determined λ and δ from equations (10) and (11):

λ = 8.24 nm

δ = 10.30 nm

Figure 6 presents a visual illustration of the result, indicating that the stability of catalyst B in real synthesis conditions is provided by cobalt crystallites, the size of which exceeds 10.30 nm. Thus, it was unexpectedly found that cobalt crystallites up to 10.30 nm in size will be oxidized under real synthesis conditions. This contradicts published data, which recommend that a 15% cobalt dispersion (crystallite size between 5-6 nm) is optimal for use on supported catalysts under typical real conditions of the Fischer-Tropsch synthesis reaction.

1.5. Optimal size distribution of crystallites of cobalt metal for a cobalt-based catalyst on a support containing 19.5% by weight of cobalt and having a reduction ratio of 75% (i.e., comparable to catalyst B). The following three criteria were used to quantify the optimal distribution:

- monomodal Gaussian size distribution of cobalt metal, measured for a freshly reduced catalyst;

- the maximum stabilized characteristic Fischer-Tropsch activity in real synthesis conditions. A stabilized cobalt-based Fischer-Tropsch catalyst is defined as a catalyst that is fully conditioned under real conditions of Fischer-Tropsch suspension synthesis using ultrapure synthesis gas. Further, it is assumed that the source gas undergoes reductive poisoning, as discussed above, so that oxidation is the only cause of deactivation during catalyst stabilization;

- the efficiency factor of the Fischer-Tropsch synthesis is approximately 1.

Monomodal Gaussian CSD is described by the equation:

Where

численность кристаллитов размером х нм;(a)

the number of crystallites with a size of x nm;

нежелательно с физической точки зрения (то есть кристаллиты с отрицательным диаметром).(b) imposed restriction:

undesirable from a physical point of view (i.e. crystallites with a negative diameter).

To resolve this situation, a restriction was imposed on the maximum attainable (i.e., negative) value:

Proposed Limit:

Thus, crystallites with a diameter of ≥0 always account for ≥99.5% of the total number. Further, 99% of the crystallite abundance is in the range: (μ-2.67σ) ≤x≤ (μ + 2.67σ). Accordingly, the maximum allowable value σ = (μ / 2.67) and, therefore,

Feature Specifications

i) df (x) / dx = 0 at x = μ, this quantity x at the maximum of the function;

ii)

iii)

In the case of a freshly reduced catalyst:

the surface area of all crystallites of metallic cobalt larger than θ nm is equal to:

In other words, the surface area of all crystallites of metallic cobalt larger than θ nm is:

Equation (16) gives the following information:

1 g of catalyst contains 0.195 g of cobalt, 75% of which is recovered. Thus, 1 gram of catalyst corresponds to 0.146 g of cobalt metal.

Table 3 shows the data according to equation (16) for a freshly reduced catalyst.

Table 3 Selected Parameters of a Monomodal Gaussian CSD Freshly Reduced Catalyst The total surface of cobalt metal in crystallites larger than θ nm, m ² / g of catalyst μ σ θ = 0 θ = 8.24 θ = 10.30 5 0.47 19.42 1.44 × 10 ^-10 0 5 0.94 18.50 1.46 × 10 ^-2 6.71 × 10 ^-10 5 1.40 17.25 0.50 5.55 × 10 ^-7 5 1.87 15.86 1.89 0.17 7 0.66 13.87 0.61 8.74 × 10 ⁰ 7 1.31 13.22 3.60 0.18 7 1.97 12.31 5.54 1.36 7 2.62 11.33 6.49 2.84 nine 0.84 10.79 9.33 0.91 nine 1.68 10.29 8.22 3.43 nine 2,52 9.58 7.75 4.77 nine 3.36 8.82 7.35 5.36 eleven 1,03 8.83 8.81 7.14 eleven 2.06 8.41 8.09 6.43 eleven 3.09 7.84 7.33 6.16 eleven 4.12 7.21 6.72 5.89 12 1.12 8.09 8.09 7.75 12 2.24 7.71 7.58 6.76 12 3.36 7.19 6.91 6.20 12 4.49 6.61 6.31 5.78 14 1.31 6.94 6.94 6.93 14 2.62 6.61 6.59 6.39 14 3.93 6.16 6.06 5.80 14 5.24 5.66 5.54 5.31 16 1,50 6.07 6.07 6.07 16 3.00 5.78 5.78 5.73 16 4,50 5.39 5.35 5.25 16 5.99 4.96 4.90 4.79

The data in this table can be used to determine the RIAF using the following values:

(a) One RIAF unit corresponds to 1.72 × 10 ⁻⁵ mol of atoms on the surface of cobalt per gram of catalyst, as described above;

(b) one cobalt atom on the surface occupies an area of 0.0662 nm ² . Therefore, one RIAF unit corresponds to 0.686 m ² surface area of cobalt metal / gram of catalyst.

Equation (17) made it possible to obtain the data shown in Table 4.

Table 4 Selected Parameters of a Monomodal Gaussian CSD Freshly Reduced Catalyst Relative characteristic activity factor (RIAF) (Fischer-Tropsch) μ σ Time 0 Start time Stabilizer. catalyst 5 0.47 28.3 0,0 0,0 5 0.94 27.0 0,0 0,0 5 1.40 25.1 0.7 0,0 5 1.87 23.1 2,8 0.2 7 0.66 20,2 0.9 0,0 7 1.31 19.3 5.2 0.3 7 1.97 17.9 8.1 2.0 7 2.62 16.5 9.5 4.1 nine 0.84 15.7 13.6 1.3 nine 1.68 15.0 12.0 5,0 nine 2,52 14.0 11.3 7.0 nine 3.36 12.9 10.7 7.8 eleven 1,03 12.9 12.8 10,4 eleven 2.06 12.3 11.8 9,4 eleven 3.09 11,4 10.7 9.0 eleven 4.12 10.5 9.8 8.6 12 1.12 11.8 11.8 11.3 12 2.24 11.2 11.0 9.9 12 3.36 10.5 10.1 9.0 12 4.49 9.6 9.2 8.4 14 1.31 10.1 10.1 10.1 14 2.62 9.6 9.6 9.3 14 3.93 9.0 8.8 8.5 14 5.24 8.3 8.1 7.7 16 1,50 8.8 8.8 8.8 16 3.00 8.4 8.4 8.4 16 4,50 7.9 7.8 7.7 16 5.99 7.2 7.1 7.0

A visual reflection of this section is presented in Fig 7, which allows us to draw the following conclusions

1. The Fischer-Tropsch catalyst containing 20 wt.% Cobalt on a support is optimal if the freshly reduced catalyst meets the following criteria:

(a) the degree of recovery is approximately 75%;

(b) it has a monomodal Gaussian size distribution of crystallites of metallic cobalt;

(c) the surface area of cobalt metal is 2.1-15.0 m ² , more preferably 4.1-13.0 m ² / g of catalyst;

(d) the geometry of the catalyst (i.e., porosity, pore size distribution, etc.) provides a factor of stabilized Fischer-Tropsch synthesis efficiency of approximately 1.

2. Therefore, it is possible to prepare a Fischer-Tropsch catalyst containing 20 wt.% Cobalt on a substrate with an initial RIAF (that is, a _i ) of 3.0-10.0, which is (2.4 ± 1.3) times greater than the corresponding value for catalyst B (a _i = 2.8).

1.6 The optimum size distribution of crystallites of metallic cobalt for a generic cobalt-based catalyst on a support with a Fischer-Tropsch efficiency factor equal to 1 and a reduced cobalt content of 1 and a reduced cobalt content of Ω wt.%, I.e., recovered in the process catalyst activation.

To quantify the optimal characteristics, the same criteria were used as in 1.5.

The mathematical equations describing the monomodal Gaussian distribution of CSD are given in Section 1.5; these are equations (12), (13), (14) and (15).

For a freshly reduced catalyst: the surface area of crystallites of metallic cobalt larger than θ nm is:

Table 5 shows the data obtained by equation (18) for the freshly restored catalyst.

Table 5 Selected Parameters of a Monomodal Gaussian CSD Freshly Reduced Catalyst The total surface of cobalt metal in crystallites larger than θ nm, m ² / g of catalyst μ σ θ = 0 θ = 8.24 5 0.47 1,331 Ω 0,000 Ω 5 0.94 1,268 Ω 0.001 Ω 5 1.40 1,182 Ω 0,034 Ω 5 1.87 1,087 Ω 0.130 Ω 7 0.66 0.950 Ω 0.042 Ω 7 1.31 0.906 Ω 0.247 Ω 7 1.97 0.844 Ω 0.380 Ω 7 2.62 0.776 Ω 0.445 Ω nine 0.84 0.739 Ω 0.639 Ω nine 1.68 0.705 Ω 0.563 Ω nine 2,52 0.656 Ω 0.531 Ω nine 3.36 0.604 Ω 0.504 Ω eleven 1,03 0.605 Ω 0.604 Ω eleven 2.06 0.576 Ω 0.554 Ω eleven 3.09 0.537 Ω 0.502 Ω eleven 4.12 0.494 Ω 0.460 Ω 12 1.12 0.554 Ω 0.554 Ω 12 2.24 0.528 Ω 0.519 Ω 12 3.36 0.493 Ω 0.473 Ω 12 4.49 0.453 Ω 0.432 Ω 14 1.31 0.476 Ω 0.476 Ω 14 2.62 0.453 Ω 0.452 Ω 14 3.93 0.422 Ω 0.415 Ω 14 5.24 0.388 Ω 0.380 Ω 16 1,50 0.416 Ω 0.416 Ω 16 3.00 0.396 Ω 0.396 Ω 16 4,50 0.369 Ω 0.367 Ω 16 5.99 0.340 Ω 0.336 Ω

The data in this table can be used to determine the RIAF using the following values:

(a) One RIAF unit corresponds to 1.72 × 10 ⁻⁵ mol of atoms on the surface of cobalt per gram of catalyst, as described above;

(b) one cobalt atom occupies an area of 0.0662 nm ² on the surface. Therefore, one RIAF unit corresponds to 0.686 m ² surface area of cobalt metal / gram of catalyst.

Equation (19) allows you to build Table 6.

Table 6 Selected Parameters of a Monomodal Gaussian CSD Freshly Reduced Catalyst Relative characteristic activity factor (RIAF) (Fischer-Tropsch) μ σ Time 0 Start time 5 0.47 1.94 Ω 0.00 Ω 5 0.94 1.85 Ω 0.00 Ω 5 1.40 1.72 Ω 0.05 Ω 5 1.87 1.58 Ω 0.19 Ω 7 0.66 1.39 Ω 0.06 Ω 7 1.31 1.32 Ω 0.36 Ω 7 1.97 1.23 Ω 0.55 Ω 7 2.62 1.13 Ω 0.65 Ω nine 0.84 1.08 Ω 0.93 Ω nine 1.68 1.03 Ω 0.82 Ω nine 2,52 0.96 Ω 0.77 Ω nine 3.36 0.88 Ω 0.73 Ω eleven 1,03 0.88 Ω 0.88 Ω eleven 2.06 0.84 Ω 0.81 Ω eleven 3.09 0.78 Ω 0.73 Ω eleven 4.12 0.72 Ω 0.67 Ω 12 1.12 0.81 Ω 0.81 Ω 12 2.24 0.77 Ω 0.76 Ω 12 3.36 0.72 Ω 0.69 Ω 12 4.49 0.66 Ω 0.63 Ω 14 1.31 0.69 Ω 0.69 Ω 14 2.62 0.66 Ω 0.66 Ω 14 3.93 0.62 Ω 0.61 Ω 14 5.24 0.57 Ω 0.55 Ω 16 1,50 0.61 Ω 0.61 Ω 16 3.00 0.58 Ω 0.58 Ω 16 4,50 0.54 Ω 0.53 Ω 16 5.99 0.50 Ω 0.49 Ω

The visual reflection of this Table is presented in Fig. 8 and allows us to draw the following conclusions.

1. A supported Fischer-Tropsch catalyst based on supported cobalt containing Ω wt.% Of reduced cobalt will be optimal if the freshly reduced catalyst meets the following criteria:

(a) has a monomodal Gaussian size distribution of crystallites of cobalt metal;

(b) the surface area of metallic cobalt is 0.014-1.03 Ω, preferably 0.28-0.89 Ω m ² / g of catalyst;

(c) the geometry of the catalyst (i.e., porosity, pore size distribution, etc.) provides a factor of stabilized Fischer-Tropsch synthesis efficiency of 1.

Example 2

An example of a cobalt-based catalyst supported on Al ₂ O ₃ for suspension synthesis according to the invention (catalyst F), which showed an increased initial Fischer-Tropsch activity.

In Example 1, it was shown that the optimal crystallite size of cobalt metal is 10-14 nm, preferably 10-12 nm, that is, this size is optimal from the point of view of maximum stabilized RIAF. With the exception of the size distribution of cobalt metal crystallites, which has a peak between 8.2 nm and 10.3 nm, the observed value of a _i (i.e., RIAF at the initial time) is the expected value of stabilized RIAF. The identification of Fischer-Tropsch supported catalysts with increased initial values of characteristic activity was to convert the bimodal size distribution of cobalt metal crystallites (CSD) of the freshly reduced catalyst sample B into a monomodal Gaussian distribution at

- the size of the most common metal crystallites, equal to 12 ± 2 nm;

- narrow distribution.

If catalyst B is used as a reference, a significant increase in the average crystallite size of cobalt oxide of the calcined improved catalyst precursor (m) g Co / (0.0025 m) g Pt / 100 g Al ₂ O ₃ can be quantified by easier reducibility. This statement is based on the general principle that it is difficult to obtain a highly dispersed and highly reduced catalyst using conventional catalyst preparation methods (for example, impregnation with nitric acid salts). Convincing confirmation of the successful obtaining of the desired size distribution of cobalt metal crystallites for freshly reduced catalysts can be obtained by a combination of the following analytical methods:

- chemisorption of H ₂ ;

- high resolution transmission electron microscopy (HRTEM);

- magnetic method;

- X-ray photoelectron spectroscopy (XPS);

- a gravimetric method for analyzing the susceptibility to oxidation in an H ₂ / H ₂ O medium in which the model is located and where cobalt oxidation in the mass is thermodynamically impossible.

To achieve this goal, that is, controlling the size distribution of cobalt oxide crystallites for the calcined Fischer-Tropsch catalyst precursors, catalyst F - (m) g Co / (0.0025 m) g Pt 100 g Al ₂ O ₃ was obtained.

Catalyst F (30 g Co / 0.075 g Pt / 3.1 g Ba / 100 g Al ₂ O ₃ .

The carrier, consisting of porous spherical Al ₂ O ₃ particles of the Puralox SCCa 5/150 brand, SASOL Germany GmbH, was modified at the stage of impregnation with barium nitrate as follows:

2.86 g of Ba (NO ₃ ) _{2 was} dissolved in 50 ml of distilled water. This solution was placed in a 500 ml round bottom flask in a rotary evaporator at 60 ° C and 50 g of Puralox SCCa 5/150 was added. Impregnation in an aqueous suspension and vacuum drying were carried out under the following conditions:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 200 thirty 70 200 90 85 200 60 85 fifty 240

This vacuum dried barium-modified intermediate was calcined in a fluidized bed in the following manner:

- Continuous air flow at a speed of 2.4 dm ³ / min;

- Temperature condition:

25 ° С- (1,6 ° С / min) → 250 ° С- (16 hours) → 250 ° С

The result was 3.1 g of Ba / 100 g of Al ₂ O ₃ .

The Fischer-Tropsch catalyst 30 g Co / 0.075 g Pt / 100 g Al ₂ O ₃ was obtained using a preformed carrier modified with barium - 3.1 g Ba / 100 g Al ₂ O ₃ according to the method of impregnation in aqueous suspension and vacuum drying followed by calcination in a fluidized bed, as described in US patent 5 733 839 and applications WO 99/42214 and WO 00/20116.

The catalyst was prepared as follows.

29.3 g of Co (NO ₃ ) ₂ · 6H ₂ O were dissolved in 28 ml of distilled water, 0.0167 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 7 ml of distilled water. The two solutions were mixed in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 35.0 g of a modified support 3.1 g Ba / 100 g Al ₂ O _{3 was} added. Impregnation in an aqueous suspension and vacuum drying was carried out according to the following regime:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 240 thirty 70 250 90 85 250 60 85 fifty 240

This vacuum dried intermediate was calcined in a fluidized bed in the following manner:

- Continuous air flow 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

35.1 g of this intermediate calcined product was subjected to a second cobalt / platinum impregnation and calcination.

16.5 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 28 ml of distilled water, 0.0273 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 7 ml of distilled water. These two solutions were mixed together in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 35 g of the impregnated and calcined product obtained in the first stage were added. Impregnation in an aqueous suspension and vacuum drying was carried out as follows:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 300 thirty 70 315 90 85 250 60 85 fifty 120

This vacuum dried intermediate was calcined in a fluidized bed in the following manner:

- Continuous air flow 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

This calcined catalyst precursor was reduced, a wax coating was applied as in the case of catalyst B, and was used in laboratory scale Fischer-Tropsch synthesis reactions in suspension in CSTR.

Modification of the Al ₂ O ₃ support for catalyst F was carried out to change the acidity of the support based on the following.

Three of the five different types of hydroxyl groups on the surface of alumina can serve to fix cobalt, that is, act as growth sites during the cobalt impregnation step. By limiting the surface concentration of potential growth points for cobalt crystallites while maintaining the same amounts of cobalt per m ^{2 of the} surface of the support just obtained, larger cobalt crystallites can be obtained. Barium is considered a promoter that can effectively reduce the concentration of hydroxyl groups on the surface of Al ₂ O ₃ , as well as other alternative carriers, such as SiO ₂ , TiO ₂ , etc.

Confirmation of this hypothetical effect of barium promotion was obtained by magnetic analysis of catalysts H and I. Catalysts H and I were obtained as follows.

Catalyst H (18 g Co / 0.05 g Pt / 100 g Al ₂ O ₃ )

The preformed Al ₂ O ₃ Puralox SCCa 5/150 carrier, supplied by SASOL Germany GmbH, was impregnated, dried in vacuum and calcined using a Co (NO ₃ ) ₂ solution according to the method described in US Pat. No. 5,733,839 and WO 99/42214. and WO 00/20116, incorporated herein by reference. In particular, catalyst H was prepared as follows.

In the first stage of impregnation, a solution of 43.7 kg of cobalt nitrate (Co (NO ₃ ) ₂ · 6H ₂ O), 24.0 g of (NH ₃ ) ₄ Pt (NO ₃ ) ₂ in 32.1 l of distilled water was mixed with 50, 0 kg Puralox SCCa 5/150 (preformed Al ₂ O ₃ ), SASOL Chemie GmbH, Uberseering, Germany). The resulting suspension was placed in a conical vacuum dryer with continuous stirring. The temperature of this suspension was raised to 60 ° C, after which a vacuum of 20 kPa (a) was applied. During the first 3 hours of drying, the temperature was slowly raised, it reached 95 ° C after 3 hours. After 3 hours, the vacuum was reduced to 3-15 kPa (a). The impregnated catalyst support was dried for 9 hours, after which the support was calcined at 250 ° C. for 6 hours. The preparation of this catalyst is limited to one stage of impregnation; therefore, the amount of cobalt is small - 18 g Co / 100 g Al ₂ O ₃ .

Prior to magnetic analysis of this product, this calcined catalyst precursor was reduced and a wax coating was applied according to the method described for catalyst B.

Catalyst I (18.8 g Co / 0.052 g Pt / 3.1 g Ba / 1.4 g Si / 100 g Al ₂ O ₃ )

Puralox SCCa 5/150 (preformed Al ₂ O ₃ catalyst carrier supplied by SASOL Germany GmbH) was modified by impregnation with a suspension of tetraethoxysilane (i.e. TEOS) in ethanol and calcined in a rotary kiln according to the method described in WO 99/42214, being a link. The technique was carried out as follows.

To 32 g of TEOS (tetraethoxysilane) and 200 g of ethanol were added 200 g of Puralox SCCa 5/150 (Al ₂ O ₃ catalyst carrier, supplied by SASOL Germany GmbH). In the impregnation step, the suspension was placed in a vacuum dryer with continuous stirring. The suspension was dried at 100 ° C and a pressure of 20 mbar. Then, the dried impregnated support was calcined at 500 ° C with a heating rate of 1 ° C / min, air was supplied at a speed of 1.7 dm ³ / min into the stainless steel calcination tube for 2 hours. Then, 50 g of this modified support was impregnated with a solution of 3 g of Ba (NO ₃ ) ₂ in 30 ml of water, adding the support to the solution. In the impregnation step, the suspension was placed in a vacuum dryer and continuously stirred. The suspension was dried at 100 ° C and a pressure of 20 mbar. Then, the dried impregnated modified carrier was calcined at 500 ° C with a heating rate of 1 ° C / min, air was supplied at a speed of 1.7 dm ³ / min in a fluidized bed for 2 hours. This support obtained was 3.1 g Ba / 1.4 g Si / 100 g Al ₂ O ₃ , then impregnated with an aqueous solution of Co (NO ₃ ) ₂ , dried under vacuum and calcined according to the catalyst preparation method described in US Pat. No. 5,733,839 and WO 99/42214 and WO 00/20116, incorporated herein by reference. Specifically, catalyst I was prepared as follows. 50 g of this modified carrier was mixed with a solution of 22.25 g of Co (NO ₃ ) ₂ · 6H ₂ O and 25 mg of Pt (NH ₃ ) ₄ (NO ₂ ) ₂ in 50 ml of water, adding the carrier to the solution. In the impregnation step, the suspension was transferred to a vacuum dryer and stirred continuously. The temperature of this suspension increased to 100 ° C. and a vacuum of 20 mbar was applied for 2 hours. The dried impregnated product was calcined at 150 ° C with a heating rate of 1 ° C / min for one hour and then the temperature was increased to 250 ° C with a heating rate of 1 ° C / min for 4 hours with air supply at a speed of 1.7 dm ³ / min The preparation of this catalyst was limited to one stage of impregnation; therefore, a support was obtained with a relatively low metal content of 18.8 g Co / 100 g Al ₂ O ₃ .

This calcined catalyst precursor was reduced and a wax coating was applied according to the procedure described for catalyst B. Then it was analyzed by the magnetic method. The results are shown in Table 7.

Table 7 Catalyst Magnetic data for freshly recovered samples View Composition The most common cobalt crystallite size The cobalt content (wt.%) In crystallites larger than 15 nm N 18 g Co / 0.05 g Pt / 100 g carrier 6.1 ± 0.8 29 ± 3 I 18.5 g Co / 0.05 g Pt / 3.1 g Ba / 100 g carrier 8 21

The apparent discrepancy seen in FIG. 8 (a barium-promoted catalyst precursor, reduced to a slightly greater degree) may be due to an artifact that was caused by some barium that could dissolve in the cobalt impregnation compound solution.

The barium-impregnated and dried catalyst intermediate F was calcined at a rather high temperature of 600 ° C. in order to strengthen the bond between alumina and barium. This intention was reinforced by published evidence that the activity of Fischer-Tropsch catalysts is sensitive to alkaline promotion and that the structural promotion of cobalt-based catalysts, for example, magnesium oxide, generally leads to reaction resistance. Therefore, it can be concluded that catalyst F exhibits quantitative evidence of an improved size distribution of cobalt metal crystallites in size, which was expected to produce Fischer-Tropsch catalysts with increased initial characteristic activity and, therefore, stabilized RIAF.

Table 8 shows the data confirming this conclusion.

Table 8
Catalyst F Characteristics and Fischer-Tropsch Synthesis Suspension Conditions in CSTR Catalyst F Catalyst Characteristics: i) Composition 30 g Co / 0.075 g Pt / 3.1 g Ba / 100 g Al ₂ O ₃ ii) Co content, wt.% (measured in a fully calcined precursor) 17.4 iii) the amount of reduced Co (in fully calcined state of the precursor), wt.% 13.1 * iv) Co surface area (chemisorption H ₂ ), m ² / g of catalyst 9.7 Synthesis conditions: Experience Number 48J Time (h) fifteen Conversion (H ₂ + CO),% 51 The partial pressure in the reactor: H ₂ (bar) 6.5 CO (bar) 3,7 H ₂ O (bar) 3.2 CO ₂ (bar) 0.2 Fischer-Tropsch initial characteristic activity factor (i.e., a _i = RIAF at t _i ) 3.6 * Note: It is assumed that the degree of recovery is 75%.

Based on the data in Table 8 and Figure 8, the following conclusions can be made.

Catalyst F.

Catalyst F had an initial Fischer-Tropsch characteristic activity factor of 3.6 units. This was achieved with a cobalt content of 30 g / 100 g Al ₂ O ₃ .

The relative increase in a _{i is} shown in Table 9.

Table 9 a _i (RIAF at the initial moment of time) Catalyst F 3.6 Catalyst B prepared with 10.0 mg Co (NO ₃ ) ₂ · 6H ₂ O per m ² (fresh) Al ₂ O ₃ 2,8

Catalyst F contained 13.1 wt.% Of reduced cobalt, as can be seen in FIG. 5, if Ω was replaced with a value of 13.1 for catalyst F. The surface area of cobalt in freshly reduced catalyst F was determined to be 9.7 m ² / g of catalyst, the most the common value of a _i is approximately 10.0.

The above findings are summarized in Table 10.

Table 10 Fisher-Tropsch Initial Activity Expressed as a multiple of catalyst B Expressed as a percentage of the ideal * Fischer-Tropsch cobalt-based catalyst on a support Catalyst F 1.29 about 36

* Note: An ideal supported Fischer-Tropsch catalyst has the following characteristics:

a) the monomodal size distribution of crystallites of cobalt metal for a freshly reduced sample;

b) in the case of a stabilized catalyst, it has an efficiency factor of 1 in Fischer-Tropsch synthesis reactions.

Example 3: (not according to the invention)

Catalyst K (30 g Co / 0.075 g Pt / 3 g F / 100 g Al ₂ O ₃ )

Puralox SCCa 5/150 (i.e., spherical porous catalyst support particles) supplied by SASOL Germany GmbH) was modified during the hydrofluoride impregnation step as follows: 3 g of a 48% solution of hydrofluoric acid were mixed with 50 ml of distilled water in a Teflon beaker. This solution was added to 50 g of Puralox 5/150 in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C. Impregnation in an aqueous suspension and vacuum drying was carried out according to the following procedure:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 200 thirty 70 200 90 85 200 60 85 fifty 240

This vacuum dried fluorine-modified intermediate was calcined in a fluidized bed in the following manner:

- A continuous stream of air was supplied at a speed of 2.4 dm ³ / min;

- Temperature condition:

from 25 ° C to 500 ° C at a speed of 1.6 ° C / min and exposure at 500 ° C for 4 hours. Received a modified carrier - 3.1 g F / 100 g Al ₂ About ₃ . The Fischer-Tropsch catalyst for synthesis in suspension, 30 g Co / 0.075 g Pt / 100 g Al ₂ O ₃ , was obtained on a modified preformed carrier - 3 F / 100 g Al ₂ O ₃ , according to the method of impregnation in aqueous suspension and drying, followed by fluid bed calcination as described in US Pat. No. 5,733,839, WO 99/42214 and WO 00/20116.

The catalyst was prepared as follows.

29.3 g of Co (NO ₃ ) ₂ · 6H ₂ O were dissolved in 28 ml of distilled water and 0.0167 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 7 ml of distilled water. The two solutions were mixed in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 35.0 g of a modified support 3.1 g F / 100 g Al ₂ O _{3 was} added. Impregnation in an aqueous suspension and vacuum drying was carried out as follows:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 200 thirty 70 200 90 85 200 60 85 fifty 240

The resulting vacuum dried intermediate was calcined in a fluidized bed under the following conditions:

- Continuous air flow at a speed of 1.7 dm ³ / min;

- Temperature condition:

from 25 ° C to 250 ° C at a rate of 1 ° C / min and exposure at 250 ° C for 6 hours. 35 g of this calcined intermediate were subjected to a second stage of cobalt / platinum impregnation and calcination:

16.5 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 28 ml of distilled water and 0.0273 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 7 ml of distilled water. The two solutions were mixed in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C. and atmospheric pressure, and 35.0 g of an intermediate product impregnated with cobalt / platinum and calcined in the first stage were added. Impregnation in an aqueous suspension and vacuum drying was carried out as follows:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 200 thirty 70 200 90 85 200 60 85 fifty 240

This vacuum dried intermediate was calcined in a fluidized bed under the following conditions:

- Continuous air flow at a speed of 1.7 dm ³ / min;

- Temperature condition:

from 25 ° C to 250 ° C at a rate of 1 ° C / min and exposure at 250 ° C for 6 hours. For use in a laboratory scale Fischer-Tropsch synthesis suspension in suspension in CSTR, this calcined catalyst precursor was reduced and wax coated using the method described for Catalyst B. This catalyst was used in the Fischer-Tropsch synthesis reaction (Table 11), no effect promotion by fluoride on the characteristic activity of the Fischer-Tropsch catalyst was not observed.

This fact can be explained by the fact that, in contrast to barium, fluoride does not bind to hydroxyl groups, which are used to fix cobalt crystallites, but fluoride binds to other hydroxyl groups. Thus, fluoride does not affect the size distribution of cobalt crystallites and, therefore, the Fischer-Tropsch characteristic activity.

Table 11 Catalyst TO Catalyst Characteristics: i) Composition 30 g Co / 0.075 g Pt / 3 g F / 100 g Al ₂ O ₃ ii) Co content, wt.% (measured in a fully calcined precursor) 19.0 iii) the amount of reduced Co (in the fully calcined state of the precursor), wt.% 4.3 * Synthesis conditions: Experience Number 11J Time (h) fifteen Conversion (H ₂ + CO),% 64 The partial pressure in the reactor: H ₂ (bar) 5.3 CO (bar) 3.0 H ₂ O (bar) 4.6 CO ₂ (bar) 0.2 Fisher-Tropsch initial characteristic activity factor (i.e., a _i = RIAF at t _i ) 3.0 * Note: It is assumed that the degree of recovery is 75%.

Example 4

Examples of cobalt-based catalysts supported on Al ₂ O ₃ for suspension synthesis according to the invention (catalysts E and G) that exhibit increased initial Fischer-Tropsch activity.

Samples of catalysts E and G were obtained to achieve the goal indicated above, that is, to control the size distribution of cobalt oxide crystallites in calcined precursors of Fischer-Tropsch catalysts of the composition (m) g Co / (0.0025 m) g Pt / 100 g Al ₂ O _3.

Catalyst E (40 g Co / 0.100 g Pt / 100 g Al ₂ O ₃ )

A product of SASOL Germany GmbH of the Puralox SCCa 5/150 brand (i.e. preformed porous spherical Al ₂ O ₃ particles) was coated with a uniform carbon-based layer in KataLeuna GmbH Catalysts (Am Haupttor, D-06236 Leuna; Germany) by the method described in EP 0681868, this source is incorporated by reference. The result is a modified carrier of 12.4 g C / 100 g Al ₂ About ₃ .

Using this modified support, 12.4 g of C / 100 g of Al ₂ O ₃ gave 40 g of Co / 0.100 g of Pt / 100 g of Al ₂ O ₃ , a Fischer-Tropsch reaction catalyst in suspension, by the method of impregnation in an aqueous suspension and vacuum drying followed by calcination in the fluidized bed described in US patent 5733839 and applications WO 99/42214 and WO 00/20116, incorporated by reference.

In particular, catalyst E was prepared as follows.

34.1 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 40 ml of distilled water, and 0.0185 g of (NH ₃ ) ₄ Pt (NO ₂ ) _{2 was} dissolved in 10 ml of distilled water. These two solutions were mixed.

in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 50 g of a modified support 12.4 g C / 100 g Al ₂ O _{3 was} added. Impregnation in an aqueous suspension and vacuum drying was carried out under the following conditions:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 240 thirty 70 240 90 85 240 60 85 fifty 240

The obtained vacuum-dried intermediate was subjected to calcination in a fluidized bed according to the following mode:

- Continuous air flow 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

50 g of this intermediate calcined product was subjected to a second cobalt / platinum impregnation and calcination.

34.1 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 40 ml of distilled water and 0.0189 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 10 ml of distilled water. The two solutions were mixed in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 50 g of the intermediate product, impregnated and calcined in the first stage, were added. Impregnation in an aqueous suspension and vacuum drying was carried out by the method used in the first stage of cobalt / platinum impregnation. This vacuum dried intermediate was immediately calcined in a fluidized bed under the following conditions:

- A continuous stream of air is supplied at a speed of 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

50 g of the calcined product was subjected to third cobalt / platinum impregnation and calcination.

25.4 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 40 ml of distilled water, 0.0446 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 10 ml of distilled water. The two solutions were mixed in a 500 ml round bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure, and 50 g of the intermediate product, impregnated and calcined in the second stage, were added. Impregnation in an aqueous suspension and vacuum drying was carried out by the method used in the first stage of cobalt / platinum impregnation. This vacuum dried intermediate was immediately calcined in a fluidized bed under the following conditions:

A continuous air stream is supplied at a speed of 1.7 dm ³ / min;

Temperature mode:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

All three successive stages of impregnation were thus carried out in accordance with the restrictions imposed by the pore volume of solid materials.

To prepare for use for Fischer-Tropsch synthesis in suspension in a CSTR on a laboratory scale, the calcined catalyst precursor obtained above was reduced at a temperature of 350 ° C. For this purpose, 22.8 g of the catalyst was reduced with pure hydrogen (bulk velocity 2000 ml / g of catalyst / hour) at a pressure of 1 bar, while the temperature was raised from 25 ° C to 350 ° C at a speed of 1 ° C / min, and then maintained equal to 350 ° C for 16 hours. The reduced catalyst was allowed to cool to room temperature, hydrogen was replaced with argon and discharged into molten wax in an argon atmosphere. This wax-containing catalyst was then placed in a synthesis reactor.

Catalyst G (3 g Co / 0.075 g Pt / 100 g Al ₂ O ₃ )

A platinum-promoted cobalt-based catalyst was prepared on a preformed Puralox SCCa 5/150 carrier from SASOL Germany GmbH in accordance with the impregnation and vacuum drying process followed by calcination described in US Pat. No. 5,733,839 and WO 99/42214 and WO 00/20116 . Specifically, the catalyst was prepared as follows.

44.6 g of Co (NO ₃ ) ₂ · 6H ₂ O was dissolved in 40 ml of distilled water, 0.0248 g of (NH ₃ ) ₄ Pt (NO ₃ ) _{2 was} dissolved in 10 ml of distilled water. The two solutions were mixed in a 500 ml round bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure and 50 g of Puralox SCCa 5/150 was added. Impregnation in an aqueous suspension and vacuum drying is carried out under the following conditions:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 240 thirty 70 244 90 85 242 60 85 fifty 240

This vacuum dried product was immediately calcined in a fluidized bed according to the following regime:

- Continuous air flow at a speed of 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

The calcined intermediate of the first cobalt / platinum impregnation step and the calcination was then partially reduced to a second (and last) cobalt / platinum impregnation. For this purpose, this intermediate was reduced with pure hydrogen (bulk rate 2000 ml / g of intermediate / hour) at a pressure of 1 bar, while the temperature was raised from 25 ° C to 230 ° C at a speed of 1 ° C / min, after which the temperature was maintained constant and equal to 230 ° C for 2 hours.

35.0 g of this partially reduced product was subjected to a second impregnation with an aqueous solution of cobalt / platinum in an argon atmosphere, and the impregnation solution was prepared as follows.

22.7 g of Co (NO) ₃ · 6H ₂ O was dissolved in 28 ml of distilled water, and 0.0401 g of (NH ₃ ) ₄ Pt (NH ₃ ) _{2 was} dissolved in 7 ml of distilled water. The two solutions were mixed in a 500 ml round-bottom flask in a rotary evaporator at 60 ° C and atmospheric pressure. Impregnation in an aqueous suspension and vacuum drying was carried out under the following conditions:

Oil bath temperature (° C) Pressure in a rotary evaporator (mbar) Time (min) 60 Atmospheric 10 60 300 thirty 70 307 90 85 301 60 85 fifty 240

This vacuum dried product was immediately calcined in a fluidized bed according to the following regime:

- Continuous air flow at a speed of 1.7 dm ³ / min;

- Temperature condition:

25 ° С- (1 ° С / min) → 250 ° С- (6 hours) → 250 ° С

To prepare for use for Fischer-Tropsch synthesis in a laboratory scale suspension in CSTRa, the calcined catalyst precursor obtained above was reduced and wax coated using the procedure described for catalyst B.

Programmed Temperature (TPR) Catalyst Reduction Profiles (TPR) (Figures 10 and 11) are consistent with the assumption that reducibility is a qualitative indicator of the increase in average cobalt oxide crystallite size, as also explained in Example 2. Increase in Fisher's original characteristic activity -Tropsha shown in Fig.8 was expected.

Therefore, we can conclude that catalysts E and G are characterized by a qualitative improvement in the size distribution of crystallites of cobalt metal, i.e., they have a characteristic that, as expected, should lead to the production of Fischer-Tropsch catalysts with increased initial characteristic activities and, therefore, with stabilized RIAF. This expectation came true, as shown in Table 12.

Table 12
The use of cobalt-based catalysts E and G in Fischer-Tropsch synthesis reactions in suspension in CSTR Catalyst E G Catalyst Characteristics: i) Composition 40 g Co / 0,100 g Pt / 100 g Al ₂ O ₃ 30 g Co / 0.075 g Pt / 100 g Al ₂ O ₃ ii) Co content, wt.% (measured in fully calcined predecessor) 22.6 18.6 iii) the amount of reduced Co (in fully calcined state of the precursor), wt.% 17.0 * 14.0 * iv) Co surface area 14.9 12.9 (chemisorption H ₂ ), m ² / g of catalyst Synthesis conditions: Experience Number 45J1 46J1 Time (h) fifteen fifteen Conversion (H ₂ + CO),% 76 65 The partial pressure in the reactor: H ₂ (bar) 4.0 5,0 CO (bar) 2,3 2.9 H ₂ O (bar) 5.9 4.4 CO ₂ (bar) 0.5 0.3 Fischer-Tropsch initial characteristic activity factor (i.e., a _i = RIAF at 1) 5,6 4.7 * Note: The recovery was assumed to be 75%.

Based on the data in Table 12 and Figures 8 and 12, the following conclusions can be made.

Catalyst E.

Catalyst E had an initial Fischer-Tropsch characteristic activity of 5.6 RIAF units. The catalyst contained 40 g Co / 100 g Al ₂ O ₃ .

In the case of catalyst B, a cobalt content of 30 g Co / 100 g Al ₂ O ₃ was considered optimal for the catalyst prepared on a Puralox SCCa 5/150 carrier from SASOL Germany GmbH, this value is limited by the maximum amount that can be introduced in a two-stage aqueous impregnation solution of Co (NO ₃ ) ₂ . This preferably spherical Al ₂ O ₃ filler is characterized by a surface area of 150 ± 10 m ² / g, assuming that 30 g Co / 100 g Al ₂ O ₃ corresponds to the use of 10 mg Co (NO ₃ ) ₂ · 6H ₂ About on m ² freshly obtained filler Al ₂ About ₃ . However, catalyst B is also characterized by a _i of 2.8 ± 0.2. Figure 12 reflects the curve constructed on the basis of this information and the value of a _i obtained on the basis of other experiments of the Fischer-Tropsch synthesis.

The relative increase in a _i observed when preparing catalyst E is shown in Table 13.

Table 13 a _i (RIAF at the initial time) Catalyst E 5,6 Catalyst B obtained using 13.3 mg of Co (NO ₃ ) ₂ · 6H ₂ O per m ^{2 of} freshly prepared Al ₂ O ₃ 3.3 * * Note: determined from the most suitable equality in Fig. 12.

Catalyst E contained 17.0 wt.% Of reduced cobalt, this was determined using Fig. 8, when replacing Ω by 17.0. The surface area of the cobalt metal of the freshly reduced catalyst E is equal to 14.9 m ² / g of catalyst, if we assume that the maximum achievable a _i is approximately 7.5.

Catalyst G.

Catalyst G had an initial Fischer-Tropsch characteristic activity of 4.7 RIAF units. This was achieved with a cobalt content of 30 g / 100 g Al ₂ O ₃ .

The relative increase in a _i achieved by the preparation of catalyst G is shown in Table 14.

Table 14 a _i (RIAF at the initial time) Catalyst G 4.7 Catalyst B obtained using 10.0 mg Co (NO ₃ ) ₂ · 6H ₂ O per m ^{2 of} freshly prepared Al ₂ O ₃ 2.8 *

* Note: calculated according to the most suitable equation in Fig. 12.

Catalyst G contained 14.0 wt.% Of reduced cobalt; Fig. 8 was used, where 14.0 was substituted for Ω. The surface area of cobalt metal in the freshly reduced catalyst G was determined, and it is equal to 12.9 m ² / g of the catalyst, using the maximum achievable value of a _i equal to about 4.3.

These data are summarized in Table 15.

Table 15 Initial Fisher-Tropsch Characteristic Activities Multiple of the indicator for catalyst B Expressed as a percentage of the ideal * Fischer-Tropsch cobalt-based catalyst on a support Catalyst E 1.70 about 75 Catalyst G 1.68 about 100 * Note: An ideal cobalt-based Fischer-Tropsch catalyst has the following characteristics:
a) a monomodal size distribution of crystallites of cobalt metal;
b) in the case of a stabilized catalyst, the Fischer-Tropsch efficiency factor equal to 1.

Claims (28)

1. The Fischer-Tropsch catalyst based on cobalt containing a porous catalyst support and crystallites of metallic cobalt in the specified media and characterized by: i. a certain amount of cobalt in a reducible form, expressed as Ω wt.% based on the total weight of the catalyst before reduction; ii. in the fresh state, crystallites of metallic cobalt, characterized by a monomodal Gaussian distribution; iii. in a freshly restored state, the surface area of the particles of metallic cobalt, equal to from 0.14 Ω to 1.03 Ω m ² / g of catalyst; iv. in the freshly restored state, the geometric form of the catalyst, which provides a factor of stabilized activity in the Fischer-Tropsch reaction, equal to 0.9 or more. 2. The catalyst according to claim 1, characterized in that the surface area of the cobalt metal in the catalyst in the fresh state is equal to from 0.28 Ω to 0.89 Ω m ² / g of catalyst. 3. The catalyst according to claim 1 or 2, characterized in that the size of most cobalt crystallites exceeds 8 nm. 4. The catalyst according to one of claims 1 to 3, characterized in that the porous catalyst support is calcined. 5. The catalyst according to one of claims 1 to 4, characterized in that the catalyst carrier is modified, representing particles of a coated catalyst carrier based on a modifying agent selected from Li, Na, K, Rb, Cs, Fr, Be, Mg , Ca, Sr, Ba, Ra and mixtures thereof. 6. The catalyst according to claim 5, characterized in that the modifying agent is barium, and the modified catalyst carrier contains particles of a catalyst carrier containing a barium-based coating. 7. The catalyst according to claim 6, characterized in that the amount of barium contained in the particles of the catalyst carrier is from 0.2 to 10% by weight of the catalyst before reduction. 8. The catalyst according to one of claims 1 to 4, characterized in that the catalyst carrier is a porous particle of a carbon coated catalyst carrier. 9. The catalyst according to claim 8, characterized in that the amount of carbon contained on the carrier is 0.1-40 g of carbon / 100 g of carrier. 10. A cobalt-based catalyst precursor comprising a porous catalyst support and cobalt oxide crystallites in this support, the precursor containing cobalt in a free-form reduction, and the amount of this cobalt is expressed as Ω wt.% Based on the weight of the catalyst, and this precursor is capable of lead to the production of a freshly reduced catalyst with a monomodal Gaussian distribution of crystallites of metallic cobalt in size with a surface area of particles of metallic cobalt from 0.14 Ω m ² / g of catalyst up to 1.03 Ω m ² / g of catalyst and with a geometric shape providing a value of the catalyst activity factor in Fischer-Tropsch reactions equal to 0.9 or more. 11. The precursor of claim 10, wherein the porous catalyst carrier is calcined. 12. The precursor of claim 10 or 11, wherein the catalyst carrier is modified, representing particles of a coated catalyst carrier based on a modifying agent selected from Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca , Sr, Ba, Ra and mixtures thereof. 13. The precursor according to p. 12, characterized in that the modifying agent is barium, and the modified catalyst carrier contains particles of a catalyst carrier containing a barium-based coating. 14. The precursor according to p. 13, characterized in that the amount of barium contained on the particles of the catalyst carrier is from 0.2 to 10% by weight of the catalyst before recovery. 15. The precursor of claim 10 or 11, characterized in that the catalyst carrier is a porous particle of a carbon coated catalyst carrier. 16. The precursor according to clause 15, characterized in that the amount of carbon contained on the carrier is 0.1-40 g of carbon / 100 g of carrier. 17. A method for producing a cobalt-based catalyst precursor, comprising impregnating the particles of the porous modified catalyst support with a cobalt salt and partially drying the impregnated carrier to obtain a partially dried impregnated carrier and calcining the partially dried impregnated carrier to obtain a cobalt-based catalyst precursor, the precursor comprising calcined porous particles modified catalyst support containing cobalt oxide crystallites contains op a certain amount of cobalt in a reducible form, and this amount is expressed as Ω wt.% based on the weight of the catalyst, and the specified predecessor is capable of producing a freshly reduced catalyst with a monomodal Gaussian distribution of cobalt metal crystallites in size with a surface area of particles of metallic cobalt from 0.14 Ω m ² / g of catalyst up to 1.03 Ω m ² / g of catalyst and with a geometric shape that provides a value of the catalyst activity factor in Fischer-Tropsch reactions equal to 0, 9 or more. 18. A method for producing a cobalt-based Fischer-Tropsch catalyst, comprising impregnating particles of a porous modified catalyst support with a cobalt salt and partially drying the impregnated support to obtain a partially dried impregnated support; calcining the partially dried impregnated support to obtain a cobalt-based catalyst precursor, the precursor comprising particles of a calcined porous modified catalyst support containing cobalt oxide crystallites and reducing the cobalt-based catalyst precursor to produce a cobalt-based catalyst that contains a certain amount of cobalt in capable of recovery form, and this amount is expressed as Ω wt.% based on the weight of the catalyst to of the reduction, in the freshly reduced state, has a monomodal Gaussian size distribution of crystallites of cobalt metal, in the freshly reduced state, has a surface area of particles of metallic cobalt equal to 0.14-1.03 Ω m ² / g of catalyst, and in the freshly reduced state has a catalyst geometry that provides factor stabilized efficiency in the Fischer-Tropsch reactions, equal to 0.9 or more. 19. The method according to 17 or 18, characterized in that the cobalt salt is cobalt nitrate, and the modified catalyst carrier is alumina, silica, mixed silica-alumina, titanium oxide or magnesium oxide containing a coating based on one or several metals of Group IA and / or Group II of the Periodic Table of the Elements which are a modifying agent. 20. The method according to 17 or 18, characterized in that the cobalt salt is cobalt nitrate, and the modified catalyst carrier is alumina, silica, mixed silica-alumina, titanium oxide or magnesium oxide coated with carbon. 21. The method according to any one of paragraphs.17-20, characterized in that the carrier is a protected modified catalyst carrier containing silicon as a modifying component. 22. The method according to any of paragraphs.17-21, characterized in that the cobalt-based catalyst precursor is obtained by a two-stage method of impregnation in suspension and annealing, which includes, in the first stage, impregnating the catalyst support with a cobalt salt, partially drying the impregnated support and calcining the partially dried support with obtaining the calcined material and then in the second stage, impregnating the calcined product with a cobalt salt, partially drying the impregnated product and calcining the partially dried product to obtain catalyst precursor. 23. The method according to p. 22, characterized in that it includes the partial restoration of the calcined product before impregnating it with cobalt salt. 24. The method according to item 23, wherein the partial recovery of the calcined product is carried out at a temperature of from 100 to 300 ° C. 25. The method according to item 23 or 24, characterized in that the partial recovery of the calcined material is carried out by contacting the calcined product with a gas containing hydrogen and / or carbon monoxide. 26. The method according to any of paragraphs.22-25, characterized in that at any or both stages of the impregnation in suspension add a water-soluble salt - the precursor of palladium or platinum or a mixture of such salts as an alloying agent that promotes the recovery of cobalt. 27. A method for producing a cobalt-based catalyst precursor, comprising impregnating particles of a porous catalyst support with a cobalt salt, partially drying the impregnated support, and calcining the partially dried support to obtain a calcined product; at least partially recovering the calcined product and then the second stage of impregnating the support by impregnating the at least partially reduced product with cobalt salt, partially drying the impregnated product and calcining the partially dried impregnated product to obtain a cobalt-based catalyst precursor, the precursor being a calcined a porous catalyst support containing cobalt oxide crystallites and an amount of cobalt in a reducible form, expressed Noe like Ω wt.% of the total weight of precursor and catalyst precursor capable of forming after reduction catalyst having a monomodal Gaussian distribution of the cobalt metal crystallite size, surface area of the cobalt metal to 0.14 Ω 1.03 Ω m ² / g catalyst and such a catalyst geometry that provides a Fischer-Tropsch stabilized efficiency factor of 0.9 or more. 28. A method of producing a cobalt-based catalyst, comprising impregnating particles of a porous catalyst support with a cobalt salt, partially drying the impregnated support, and calcining the partially dried support to obtain a calcined product; at least partial recovery of the calcined product; in the second stage of impregnation of the carrier, impregnation of at least partially reduced product with cobalt salt and partial drying of the impregnated product and in the calcination step, calcining the partially dried impregnated product to obtain a cobalt-based catalyst precursor, the precursor being a calcined porous catalyst carrier containing oxide crystallites cobalt and the amount of cobalt in a reducible form, expressed as Ω wt.% of the total mass of the precursor, and pre after reduction, the catalyst precursor is capable of forming a catalyst having a monomodal Gaussian size distribution of cobalt metal crystallites, a surface area of cobalt metal from 0.14 Ω to 1.03 Ω m ² / g of catalyst and such a catalyst geometry that provides the Fischer-Tropsch stabilized efficiency factor equal to 0.9 or more, and reducing the cobalt-based catalyst precursor to obtain a cobalt-based catalyst that has an amount of cobalt in the process pre-reduction form, expressed as Ω wt.% of the total catalyst mass before reduction, in the freshly reduced state having a unimodal Gaussian size distribution of metallic cobalt crystallites, in the freshly reduced state, has a surface area of metal cobalt particles of 0.140 Ω - 1.03 Ω m ² / g of catalyst, and in a freshly reduced state, has such a catalyst geometry that provides a stabilized efficiency factor in Fischer-Tropsch reactions of 0.9 or more.

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