RU2436832C2 - Catalyst for reducing carbon monoxide, method of preparing catalyst and method of producing hydrocarbon - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of preparing a catalyst for Fischer-Tropsch synthesis, involving the following steps a)-d): a) pretreatment of aluminium oxide or silicon dioxide in spherical form through saturation in an aqueous solution with pH 7 or lower, which is selected from a group consisting of aqueous nitric acid solution, aqueous acetic acid solution, aqueous sulphuric acid solution, aqueous hydrochloric acid solution, ion-exchange water and distilled water; b) saturating the treated aluminium oxide or silicon dioxide in a zirconium solution whose volume is twice or more higher than the volume of aluminium oxide or silicon dioxide in order to deposit the treated aluminium oxide or silicon dioxide; c) annealing the aluminium oxide or silicon dioxide on which zirconium has been deposited to obtain a carrier in which zirconium in form of an oxide is selectively deposited near the outer surface of the metal carrier; d) depositing onto the carrier one or more types of metals selected from a group consisting of cobalt and ruthenium in amount ranging from 3 to 50 wt % in terms of the catalyst, where 75 wt % or more of the total amount of zirconium oxide is deposited on 1/5 or less portion of a radial area running from the outer surface of the catalyst to its centre. The invention also relates to a catalyst obtained using said method and a method of producing hydrocarbons via Fischer-Tropsch synthesis using said catalyst.

EFFECT: catalyst obtained using said method has improved catalyst performance.

4 cl, 2 tbl, 3 ex

Description

FIELD OF THE INVENTION

The present invention relates to a catalyst for the reduction of carbon monoxide, methods for preparing such catalysts, and methods for producing hydrocarbons resulting from the reduction of carbon monoxide.

State of the art

In recent years, the requirements for sulfur in liquid fuels such as gasoline and gas oils have been tightened to a much greater extent than before. In this regard, it is now absolutely necessary to obtain clean liquid fuels that are environmentally friendly, which are characterized by a reduced content of sulfur and aromatic hydrocarbons. An example of one way to produce such pure fuels is Fischer-Tropsch synthesis (FT). FT-synthesis makes it possible to simultaneously obtain the basic component of pure liquid fuel, which is enriched in paraffins and does not contain sulfur, and wax (FT-wax). FT wax can be converted to the middle fraction (the base component of pure liquid fuel for kerosene or gas oil) as a result of hydrocracking.

The Fischer-Tropsch synthesis is carried out using catalysts containing an active metal, such as iron or cobalt, supported on a carrier such as silica or alumina (for an example, see patent document No. 1 below).

It has been reported that these catalysts are improved in catalytic performance as a result of the use of secondary metals in combination with such an indicated active metal (for example, see Patent Document No. 2 below). Examples of secondary metals include alkali or alkaline earth metals, such as sodium, lithium and magnesium, zirconium and hafnium, which are used appropriately depending on the purpose, such as improving the conversion rate of carbon monoxide and increasing the likelihood of chain growth (α) , which will be a numerical indicator of wax production.

In order to efficiently obtain the fuel base component, which is the middle fraction, a high conversion rate of carbon monoxide and a high probability of chain growth (α) are required from the synthetic FT catalyst.

Although the aforementioned secondary metals play an important role in improving catalytic performance, the effects associated with the presence of these metals have not yet been realized to the fullest extent possible. Typically, an impregnation method, such as an initial moisture method, is used to deposit a secondary metal in a highly dispersed state. However, FT synthesis is a high-intensity exothermic reaction, and thus it is assumed that the reaction is likely to occur near the outer surface of the catalyst.

In this regard, it is assumed that the secondary metal, selectively deposited near the outer surface of the catalyst, acts more effectively to improve catalytic performance. However, examples were not known when the secondary metal was deposited near the outer surface of the catalyst, and thus the improvement in catalytic performance was inhibited.

When carbon monoxide is reduced using a catalyst, the optimal reaction conditions for the production of hydrocarbons are effectively changed depending on the type of support and active metal of the catalyst and the method of applying the secondary metal.

Patent Document No. 1: Open Laid-Open Publication of Japanese Patent No. 4-227847.

Patent Document No. 2: Open Laid-Open Publication of Japanese Patent No. 59-102440.

SUMMARY OF THE INVENTION

As a result of extensive scientific research and improvement by the authors of the present invention, the present invention has been made based on the discovery that the catalyst obtained by the selective deposition of zirconium dioxide, which is a secondary metal, near the outer surface of the metal oxide, and after this deposition of ruthenium and / or cobalt, capable of efficiently producing hydrocarbons as a result of the reduction reaction (FT synthesis) of carbon monoxide.

That is, the present invention relates to a method for producing hydrocarbons by reduction of a monoxide using a catalyst comprising a carrier comprising metal oxide and zirconium oxide, selectively deposited near the outer surface of the metal oxide, and one or more types of metal selected from cobalt and ruthenium deposited on a carrier.

Alternatively, the present invention relates to a previous method for producing hydrocarbons using a catalyst containing a carrier obtained by depositing and subsequently annealing zirconium on a metal oxide pretreated in an aqueous solution with a pH of 7 or lower, and having one or more types of metal selected from cobalt and ruthenium deposited on a carrier.

The present invention also relates to a method for preparing a carbon monoxide reduction catalyst, comprising preparing a carrier by pretreating metal oxide in an aqueous solution of pH 7 or lower, and depositing and annealing zirconium on a metal oxide and applying one or more types of metals selected from cobalt and ruthenium on the carrier.

The present invention also relates to a carbon monoxide reduction catalyst prepared using the previous preparation method.

The effects of the invention

The method for preparing the carbon monoxide reduction catalyst according to the present invention allows for selective deposition of zirconium oxide near the outer surface of the metal oxide, and thus, the method allows the creation of a catalyst with excellent properties that are required for a synthetic FT catalyst. In addition, the method according to the present invention using a carbon monoxide reduction catalyst containing a carrier obtained by selective deposition and subsequent annealing of zirconium oxide near the outer surface of the metal oxide, and one or more types of metal selected from cobalt and ruthenium supported on a carrier is capable of efficiently producing hydrocarbons, i.e., fuel base components, with a higher conversion rate of carbon monoxide and a higher probability of p the backbone of the chain (α).

The best embodiments of the invention

The present invention will now be described in more detail.

The catalyst used in the present invention is a catalyst that includes a support comprising a metal oxide and zirconium oxide, deposited selectively near the outer surface of the metal oxide, and one or more types of metal selected from cobalt and ruthenium.

There are no particular restrictions on the metal oxide of the catalyst used in the present invention. However, examples of metal oxide include silica, titanium dioxide, alumina and magnesia, and preferred examples include silica and alumina.

There are no specific restrictions on the properties of metal oxide. However, the specific surface area of the metal oxide measured by the nitrogen adsorption method is preferably from 50 to 800 m ² / g, more preferably from 150 to 500 m ² / g.

The average pore diameter of the metal oxide is preferably from 6 to 40 nm, more preferably from 10 to 20 nm. An average pore diameter of less than 6 nm is not preferred because the time of zirconium deposition would tend to increase. An average pore diameter of greater than 40 nm is not preferred because zirconium would probably penetrate into the inner region of the metal oxide.

There are no specific restrictions on the shape of the metal oxide. In view of practicality, the shape is preferably spherical, cylindrical, or a trefoil shape that has been used in an existing refinery or petrochemical plants. There are also no specific restrictions on particle diameter. However, for practical reasons, the particle diameter is preferably from 10 μm to 10 mm.

In the present invention, a method of preparing a carrier containing metal oxide and zirconium in the form of an oxide deposited selectively near the outer surface of the metal oxide is specifically carried out by pretreating the metal oxide in an aqueous solution with a pH of 7 or more, and then applying and annealing the zirconium on the metal oxide .

A description will be given for a method for pretreating metal oxide in an aqueous solution at pH 7 or lower.

An example of an aqueous solution with a pH of 7 or lower includes an aqueous solution of nitric acid, an aqueous solution of acetic acid, an aqueous solution of sulfuric acid, an aqueous solution of hydrochloric acid, ion-exchanged water and distilled water. The pH value is preferably from 5 to 7, more preferably from 6 to 7. A pH value of less than 5 is not preferred due to economic reasons, because there is a need to increase the applied zirconium concentration after pretreatment.

Pretreatment can be carried out by pouring an aqueous solution with a pH of 7 or more into a vessel containing metal oxide.

The time for impregnation of metal oxide in an aqueous solution with a pH of 7 or more is from 10 to 72 hours in the case when the mixture is left to stand, from 1 to 12 hours in the case when the mixture is treated with vibration, and from 1 to 30 minutes in the case of when the mixture is exposed to ultrasonic waves. In any case, even if the metal oxide was soaked in the solution for a time longer than necessary, this does not have an adverse effect. The above time is used when the temperature of the solution is room temperature. The impregnation time can be shortened by heating the solution to 50 ° C. Raising the temperature of the solution higher than 50 ° C is not preferred due to the possible evaporation of water, which will result in a change in pH.

After the pretreatment is carried out for a predetermined time, zirconium can be deposited on the metal oxide by pouring a solution of excess zirconium into a vessel containing the pretreated metal oxide. Subsequently, the upper liquid layer of the solution after pretreatment is preferably removed, since a smaller vessel can be used. The term "excess", as used herein, means a volume amount of two or more times the volume of metal oxide.

The zirconium source used herein may preferably be zirconyl sulfate, zirconyl acetate, (ammonium zirconyl) carbonate or zirconium trichloride, but (ammonium zirconyl) carbonate or zirconyl acetate is preferred.

The amount of zirconium applied is preferably 40 mass. percent or less, more preferably from 1 to 30 mass. percent relative to the mass of metal oxide. When the specified amount is more than 40 mass. percent, zirconium will probably not be applied selectively near the outer surface of the metal oxide.

There are no specific restrictions on the time of application of zirconium, since the time depends on a given amount of applied zirconium. However, the time usually corresponds to 3 to 72 hours.

After completion of the zirconium deposition, the carrier (metal oxide on which zirconium is deposited) is separated from the solution and then dried. There are no specific restrictions on the drying method.

Examples of the drying method include natural drying in air and degassing drying in vacuum. Drying is carried out at a temperature of from 100 to 200 ° C, preferably from 110 to 130 ° C, for from 2 to 24 hours, preferably from 5 to 12 hours.

After drying, annealing is performed to convert zirconium to oxide. There are no specific restrictions on the calcination method. Calcination is usually carried out in an air atmosphere at a temperature of from 340 to 600 ° C, preferably from 400 to 450 ° C for 1 to 5 hours.

In this way, a support is obtained which contains metal oxide and zirconium oxide selectively held near the outer surface of the metal oxide.

After that, ruthenium and / or cobalt is applied to the carrier.

In general, examples of active metals for FT synthesis include ruthenium, cobalt and iron. However, the active metals used in the present invention are limited to ruthenium, cobalt and a combination thereof in order to exploit the characteristics of zirconia.

There are no specific restrictions on the composition of the precursor containing ruthenium or cobalt. Therefore, salts or complexes of these metals can be used. Examples include nitrate, hydrochloride, formate, propionate and acetate.

There are no specific restrictions on the amount of ruthenium or cobalt with respect to the carrier. However, ruthenium or cobalt can be applied in an amount usually from 3 to 50 masses. percent, preferably from 10 to 30 mass. percent. If the specified amount is less than 3 mass. percent, activation may be insufficient. If the specified amount is over 50 mass. percent, the active metal is likely to aggregate, and thus, it can be assumed that the value of its use as a synthetic FT catalyst will be reduced.

There are no specific restrictions on the method of applying the active metal. An impregnation method such as an initial moisture method may be used.

After the active metal is deposited, drying is usually carried out at a temperature of from 100 to 200 ° C, preferably from 110 to 130 ° C for 2 to 24 hours, preferably from 5 to 10 hours, and then annealed in air at a temperature of from 340 up to 600 ° C, preferably from 400 to 450 ° C for 1 to 5 hours, to convert the active metal to oxide, thereby obtaining the carbon monoxide reduction catalyst used in the present invention.

The catalyst thus prepared is a catalyst having the excellent properties required for a synthetic FT catalyst.

When the metal oxide of the catalyst according to the present invention is in the form of a sphere, 75 mass. percent or more, preferably from 80 to 95 mass. percent of the total amount of zirconium oxide is applied to 1/5 or a smaller radial region (the outer side of the surface), extending from the outer surface of the catalyst to the center.

When carbon monoxide is reduced using a catalyst prepared as described above, the reaction temperature is usually from 180 to 320 ° C, preferably from 200 to 300 ° C. A reaction temperature lower than 180 ° C is not preferable because carbon monoxide reacts with difficulty and thus the hydrocarbon yield decreases. A reaction temperature higher than 320 ° C is also not preferred, because it is likely that the formation of a gas such as methane is increasing.

There are no specific restrictions on the hourly gas space velocity. However, it is usually from 500 to 4000 h ^-1 , preferably from 1000 to 3000 h ^-1 . When the hourly space velocity of the gas is less than 500 h ⁻¹ , the performance of the liquid fuel is likely to decrease. When the hourly space velocity of the gas is over 4000 h ⁻¹ , gas production is likely to increase as a result of an increase in the reaction temperature.

There are no specific restrictions on the reaction pressure (partial pressure of the synthesis gas of carbon monoxide and hydrogen). However, the reaction can be carried out within the range of usually from 1 to 7 MPa, preferably from 2 to 4 MPa. When the reaction pressure is less than 1 MPa, the liquid fuel yield will probably decrease. When the reaction pressure is over 7 MPa, the amount of production costs will likely increase.

There are no specific restrictions on raw materials, unless so far it consists mainly of carbon monoxide and hydrogen. However, the molar ratio of hydrogen / carbon monoxide is usually from 1.5 to 2.5, preferably from 1.8 to 2.2.

Examples

Hereinafter, the present invention will be described in more detail through the following examples and comparative examples, which should not be construed as limiting the scope of the invention.

Preparation of Catalyst A

In a 250 ml glass flask, 30 g of spherical silica was placed (average pore diameter: 10 nm, average particle diameter: 1.8 mm) and 100 ml of a nitrate aqueous solution with a pH of 6.6 was added thereto, and then a supersonic wave treatment was applied at a temperature of 40 ° C for 10 minutes. After that, approximately 50 ml of the upper liquid layer was evacuated with a Pasteur pipette and then 150 ml of a 0.2 mol / L aqueous solution of ammonium zirconyl carbonate was added. The mixture was allowed to stand at room temperature for 24 hours. After that, the mixture was filtered on a paper filter and then dried in vacuum at a temperature of 120 ° C for 6 hours and annealed in air at a temperature of 430 ° C for 3 hours.

The resulting carrier was impregnated in an aqueous solution of cobalt nitrate in such an amount that 10 mass. percent of metallic cobalt, calculated on the carrier, was placed using the initial moisture method. After that, the carrier was dried at a temperature of 120 ° C for 12 hours and then annealed at a temperature of 420 ° C for 3 hours, thus, catalyst A was obtained.

The amount of zirconium in this catalyst was quantified using fluorescence x-ray analysis. In addition, the distribution and amount of zirconium in the radial direction of the catalyst was measured using an electron microprobe (EPMA). Table 1 shows the amount of zirconium in the catalyst and the ratio of the amount of zirconium present on 1/5 or less of the radial area, varying from the outer surface to the center (near the outer surface), to the total amount of zirconium.

Catalyst Preparation B

In a 250 ml glass flask was placed 30 g of cylindrical alumina (average pore diameter: 115 nm, diameter: 1/16 '', about 3 mm) and 100 ml of ion-exchange water (pH 7.0) was added thereto and then the treatment was applied supersonic wave at a temperature of 40 ° C for 10 minutes. After that, approximately 50 ml of the upper liquid layer was evacuated with a Pasteur pipette and then 150 ml of a 0.2 mol / L aqueous solution of ammonium zirconyl carbonate was added. The mixture was allowed to stand at room temperature for 36 hours. After that, the mixture was filtered on a paper filter and then dried in vacuum at a temperature of 120 ° C for 6 hours and annealed in air at a temperature of 430 ° C for 3 hours.

The resulting carrier was impregnated in an aqueous solution of cobalt nitrate in such an amount that 10 mass. percent of metallic cobalt, calculated on the carrier, was placed using the initial moisture method. After that, the support was dried at a temperature of 120 ° C for 12 hours, and then annealed at a temperature of 420 ° C for 3 hours, thereby obtaining a catalyst B.

The amount of zirconium in this catalyst was quantified using fluorescence x-ray analysis. In addition, the distribution and amount of zirconium in the radial direction of the catalyst was measured using an electronic microprobe (EPMA). Table 1 shows the amount of zirconium in the catalyst and the ratio of the amount of zirconium present on 1/5 or less of the radial area in the direction from the outer surface to the center (near the outer surface) to the total amount of zirconium.

Catalyst Preparation C

The same preparation and analysis procedure was carried out as in the case of catalyst A, except that 30 g of the silica used to prepare catalyst A were soaked in a nitric acid aqueous solution containing 1.2 g of zirconium using the initial method humidity. The results are shown in table 1.

Catalyst Preparation D

The same preparation and analysis procedure was carried out as in the case of catalyst B, except that 30 g of the alumina used to prepare catalyst B was impregnated in a nitric acid aqueous solution containing 1.2 g of zirconium using the method initial humidity. The results are shown in table 1.

Catalyst Preparation E

The same preparation and analysis procedure was carried out as in the case of catalyst B, except that an aqueous solution of ammonium (pH 8.5) was used instead of ion-exchanged water (pH 7.0). The results are shown in table 1.

Example 1

30 g of catalyst A was charged into a fixed-bed loop reactor. Catalyst A was reduced in a stream of hydrogen gas at 400 ° C. for 2 hours before the reaction was initiated. After that, the feedstock mixed with a gas containing hydrogen and carbon monoxide in a molar ratio of 2/1 was introduced at a gas hourly space velocity of 2000 h ^-1 and the reaction was carried out at a temperature of 215 ° C and a pressure of 2.5 MPa. The gas composition and oil thus obtained at the outlet of the reactor were analyzed using gas chromatography to determine the carbon monoxide conversion rate and the chain growth probability (α) in accordance with a conventional method. The results are shown in table 2.

Example 2

The reaction was carried out under the same conditions and the same catalyst was used as in the case of Example 1, except that the reaction temperature was changed to 225 ° C. The results are shown in table 2.

Example 3

The reaction was carried out under the same conditions as in the case of example 1, except that 30 g of catalyst B was used instead of catalyst A. The results are shown in table 2.

Comparative Example 1

The reaction was carried out under the same conditions as in the case of example 1, except that 30 g of catalyst C was used instead of catalyst A. The results are shown in table 2.

Reference Example 2

The reaction was carried out under the same conditions as in the case of example 1, except that 30 g of catalyst D was used instead of catalyst A. The results are shown in table 2.

Reference Example 3

The reaction was carried out under the same conditions as in the case of example 1, except that 30 g of catalyst E were used instead of catalyst A. The results are shown in table 2.

Table 1 Total amount
zirconium (wt.%) The amount of zirconium near the outer surface of the total amount of zirconium (%) Catalyst A 3.8 91 Catalyst B 3.6 83 Catalyst C 3.6 42 Catalyst D 3,7 39 Catalyst E 6.2 39

table 2 The rate of conversion of carbon monoxide (%) Chain Growth Probability (α) Example 1 Catalyst A 58 0.93 Example 2 Catalyst A 82 0.91 Example 3 Catalyst B 56 0.92 Comparative Example 1 Catalyst C 42 0.89 Reference Example 2 Catalyst D 41 0.87 Reference Example 3 Catalyst E fifty 0.87

As shown in table 1, the preparation method according to the present invention can lead to the creation of a catalyst for the reduction of carbon monoxide carrying zirconia selectively near the outer surface.

In addition, as shown in Table 2, catalysts with zirconia deposited selectively near the outer surface (1/5 or less of the radial region from the outer surface to the center of the catalyst) are characterized by a high conversion rate of carbon monoxide and a chain growth probability (α) , and the use of catalysts allows you to effectively obtain a fuel base component.

Industrial Applicability

The method according to the present invention is capable of producing a hydrocarbon, which is a fuel base component, and is characterized by a high conversion rate of carbon monoxide and a high probability of chain growth (α).

Claims (3)

1. A method of preparing a catalyst for Fischer-Tropsch synthesis, comprising the following stages a) to d):
a) pretreatment of alumina or silica in spherical form by impregnation in an aqueous solution of pH 7 or lower, which is selected from the group consisting of an aqueous solution of nitric acid, an aqueous solution of acetic acid, an aqueous solution of sulfuric acid, an aqueous solution of hydrochloric acid, ion-exchange water and distilled water;
b) impregnating the treated alumina or silica in a zirconium solution in a bulk amount two or more times the volume of alumina or silica to deposit zirconium on the treated alumina or silica;
c) annealing the alumina or silica with zirconium deposited thereon to obtain a carrier in which zirconium in the form of oxide is selectively deposited near the outer surface of the metal carrier;
d) applying to the carrier one or more types of metals selected from the group consisting of cobalt and ruthenium in an amount of from 3 to 50 wt.% based on the catalyst,
moreover, 75 wt.% or more of the total amount of zirconium oxide is deposited on 1/5 or less of the radial region extending from the outer surface of the catalyst to its center. 2. The catalyst for the Fischer-Tropsch synthesis, in which 75 wt.% Or more of the total amount of zirconium oxide is applied to 1/5 or a smaller part of the radial region extending from the outer surface of the catalyst to its center in the catalyst, obtained by a method comprising:
a) pretreatment of alumina or silica in spherical form by impregnation in an aqueous solution with a pH of 7 or lower, which is selected from the group consisting of an aqueous solution of nitric acid, an aqueous solution of acetic acid, an aqueous solution of sulfuric acid, an aqueous solution of hydrochloric acid, ion-exchange water and distilled water;
b) impregnating the treated alumina or silica in a zirconium solution in a bulk amount two or more times the volume of alumina or silica to deposit zirconium on the treated alumina or silica;
c) annealing the alumina or silica with zirconium deposited thereon to obtain a carrier in which zirconium in the form of oxide is selectively deposited near the outer surface of the metal carrier;
d) applying to the carrier one or more types of metals selected from the group consisting of cobalt and ruthenium in an amount of from 3 to 50 wt.% calculated on the catalyst. 3. A method of producing hydrocarbons by Fischer-Tropsch synthesis, including the use of a catalyst according to claim 2.
4 The method for producing hydrocarbons according to claim 3, in which the reaction temperature in the Fischer-Tropsch synthesis is from 200 to 300 ° C.