JP2008006406A - Iron-based catalyst for Fischer-Tropsch synthesis reaction, method for producing the same, and method for producing hydrocarbons using the same - Google Patents

Abstract

An object of the present invention is to increase the production ratio of hydrocarbons having 5 or more carbon atoms suitable as fuel oil when an iron-based catalyst is used as a catalyst for FT reaction and hydrocarbons are synthesized from constituent gases.
An iron hydroxide catalyst is produced from an iron sulfate aqueous solution, and the precipitate is calcined to obtain an iron-based catalyst. The iron sulfate aqueous solution may contain a silica precursor or a silica precursor and activated carbon. The obtained iron-based catalyst includes magnetite-structured iron oxide particles and hematite-structured iron oxide particles, and also includes silica or silica and activated carbon.
[Selection figure] None

Description

  The present invention relates to an iron-based catalyst used in a Fischer-Tropsch synthesis reaction, a method for producing the same, and a method for producing hydrocarbons using the iron-based catalyst.

Fischer-Tropsch synthesis reaction (hereinafter referred to as FT reaction) is a reaction for producing hydrocarbons using synthesis gas containing carbon monoxide and hydrogen as raw materials, and produces hydrocarbons such as fuel oil having 5 or more carbon atoms. It is something that can be done.
As a catalyst used for this FT reaction, an iron-based catalyst, a cobalt catalyst, a ruthenium catalyst, and the like are known.

Among these catalysts, the iron-based catalyst is mainly composed of iron oxide particles having a hematite structure, and contains a small amount of a metal such as copper or potassium as a co-catalyst.
Conventionally, this iron-based catalyst is produced by mixing an aqueous iron nitrate solution such as ferric nitrate with an aqueous copper nitrate solution and an aqueous potassium carbonate solution, and adjusting the pH of the aqueous solution to neutral to weak alkaline to produce an iron hydroxide precipitate. Then, copper and potassium are co-precipitated in the iron hydroxide precipitate, and the precipitate is fired.
And in the iron-type catalyst manufactured by this manufacturing method, the iron oxide which comprises this mainly consists of iron oxide particles having a hematite structure.

In the FT reaction using this conventional iron-based catalyst, the proportion of liquid hydrocarbons having 5 or more carbon atoms suitable as fuel oil among the synthesized hydrocarbons is not sufficient, and the synthesis ratio of fuel oil is low. There was a problem to say.
The following are known literatures related to the iron-based catalyst for the FT reaction.
JP-A-3-39008 JP-A-3-245847 W. Ma, et al. , Applied Catalysis A: General, 268 (2004) p. 99-106

  Therefore, the problem in the present invention is to use an iron-based catalyst as an FT reaction catalyst and increase the production ratio of hydrocarbons having 5 or more carbon atoms suitable as fuel oil when synthesizing hydrocarbons from synthesis gas. In other words, the cost of conventional preparation is reduced, and a more practical device is devised.

To solve this problem,
The invention according to claim 1 is an iron-based catalyst for a Fischer-Tropsch synthesis reaction characterized by including iron oxide particles having a magnetite structure and iron oxide particles having a hematite structure.

The invention according to claim 2 is the iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 1, further comprising silica.
The invention according to claim 3 is the iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 1, further comprising silica and activated carbon.

  The invention according to claim 4 is a method for producing an iron-based catalyst for a Fischer-Tropsch synthesis reaction, wherein a precipitate of iron hydroxide is produced from an aqueous iron sulfate solution and the precipitate is calcined.

  The invention according to claim 5 is the method for producing an iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 4, wherein the iron sulfate aqueous solution contains a silica precursor or a silica precursor and activated carbon. is there.

  The invention according to claim 6 is characterized in that the Fischer-Tropsch synthesis reaction iron catalyst according to any one of claims 1 to 3 is used to synthesize hydrocarbons from synthesis gas containing carbon monoxide and hydrogen. This is a method for producing hydrocarbons.

  In the iron-based catalyst of the present invention, magnetite-structured iron oxide particles and hematite-structured iron oxide particles are included. By using this as an FT reaction catalyst, a liquid hydrocarbon having 5 or more carbon atoms is obtained. As a result, the fuel oil can be synthesized more efficiently than the conventional catalyst.

  Further, when silica or silica and activated carbon are contained, the mechanical strength and surface area of the catalyst itself are increased, and the cost performance is more excellent than that of the catalyst.

  Furthermore, according to the method for producing an iron-based catalyst of the present invention, an iron-based catalyst containing the above-described magnetite-structured iron oxide particles and hematite-structured iron oxide particles can be produced.

The iron-based catalyst for FT reaction of the present invention includes magnetite-structured iron oxide particles and hematite-structured iron oxide particles before the activation treatment (reduction treatment) performed before using the catalyst. One or two or more promoter components composed of metals such as copper, potassium, platinum, and palladium are included.
In addition to the above-mentioned promoter component, silica or silica and activated carbon are contained.

In the iron-based catalyst of the present invention, magnetite-structured iron oxide particles and hematite-structured iron oxide particles coexist, unlike those obtained by precipitation using conventional iron nitrate as a raw material. Conventional iron-based catalysts are composed only of iron oxide particles having a hematite structure.
Thus, the presence of both magnetite-structured iron oxide particles and hematite-structured iron oxide particles is expected to increase the production rate of liquid hydrocarbons having 5 or more carbon atoms obtained by the FT reaction.

The ratio of the iron oxide particles having a magnetite structure in the iron oxide of the iron-based catalyst of the present invention is preferably 10 to 99% by weight, and more preferably 50 to 99%. When the iron oxide particle having a magnetite structure is less than 10%, the performance cannot be sufficiently exhibited, and when it exceeds 99%, the effect of the promoter component to be added tends to be slightly lowered.
In addition to the magnetite-structured iron oxide particles and hematite-structured iron oxide particles, the iron-based catalyst of the present invention may contain iron oxides having other structures, but at least the oxidation of the magnetite structure. The ratio of iron particles should just be the above-mentioned range.

  Moreover, the addition ratio of the promoter component is preferably 0.1 to 10 with respect to iron 100 in terms of weight ratio. If it is less than 0.1, the reducing property of the catalyst tends to be low, and if it exceeds 10, the reactivity tends to be low.

  Silica or activated carbon is added to increase the mechanical strength of the catalyst itself, increase the surface area of the catalyst, and further improve cost performance. Silica or activated carbon appears to have a weak interaction or partial chemical bond with the catalyst body composed of iron oxide and a promoter component, thereby changing the catalyst performance.

  The addition amount of silica or silica and activated carbon is preferably 15 to 30 with respect to iron 100 in terms of weight ratio when silica alone is used. If it is less than 15, the specific surface area is low and the selectivity of the liquid hydrocarbon tends to be low, and if it exceeds 30, the amount of iron is relatively reduced, so that the reactivity tends to be low. In the case of adding silica and activated carbon, 15 to 60 is also preferable, and if it is less than 15, the difference from the silica alone is reduced in cost performance, and if it exceeds 60, the amount of iron is relatively reduced. Tend to be low.

Next, the manufacturing method of the iron-type catalyst of this invention is demonstrated.
The iron-based catalyst production method of the present invention is characterized in that iron sulfate is used as a starting material.
Specifically, a ferrous sulfate aqueous solution is prepared.

A metal salt aqueous solution serving as a promoter component such as a copper sulfate aqueous solution is added to the ferrous sulfate aqueous solution, and an alkaline aqueous solution for pH adjustment such as a sodium carbonate aqueous solution is further added to adjust the pH to 7.9 to 8.2, preferably Adjust to a weak alkalinity of 8.0 to 8.1.
As a result, a gel-like precipitate of iron hydroxide is generated, and this precipitate is accompanied by metal ions that serve as promoter components such as copper ions.

After the precipitate is filtered and washed with water, it is impregnated with an aqueous metal salt solution as a promoter component such as an aqueous potassium carbonate solution and dried as necessary. Furthermore, this is baked in the air at a temperature of 350 to 450 ° C. for 1 to 10 hours. The fired product obtained is pulverized and sieved to a predetermined particle size.
Thereby, the iron-type catalyst of this invention can be manufactured.

An iron-based catalyst containing silica or silica and activated carbon can be produced by adding a silica precursor such as water glass or this silica precursor and activated carbon to a ferrous sulfate aqueous solution. The silica precursor is not particularly limited as long as it becomes silicon oxide after firing.
The activated carbon is not particularly limited. For example, high-performance activated carbon used as a flue gas desulfurization agent in a thermal power plant, powdered recycled activated carbon for exhaust gas treatment that is reused after use, and coal gasification process. The use of an activated char generated in this way is preferable because of high cost performance. The particle size of the activated carbon is preferably 60 μm or less, and the surface area is preferably about 50 to 400 m ² / g in BET.

  In addition, the density | concentration and compounding quantity of each structural component, such as ferrous sulfate, can be suitably determined according to the composition of the iron-type catalyst to manufacture.

According to such a production method, a mixture of iron oxide particles having a magnetite structure and iron oxide particles having a hematite structure can be obtained by firing a precipitate of iron hydroxide obtained from ferrous sulfate.
In the conventional method for producing an iron-based catalyst, ferrous nitrate is used as a starting material, and the precipitate of iron hydroxide is calcined. In this production method, all of the crystal structure of iron oxide has a hematite structure.
Such a difference is considered to cause a difference in function and characteristics as a catalyst.

Next, a hydrocarbon production method using the iron-based catalyst of the present invention will be described.
The hydrocarbon production method of the present invention synthesizes a hydrocarbon by a FT reaction using a synthesis gas containing carbon monoxide (CO) and hydrogen (H ₂ ) as a raw material and using the iron-based catalyst described above. .

As the synthesis gas, those obtained by reforming (reforming) gaseous hydrocarbons such as methane gas, natural gas, and coal gas are used. The ratio of hydrogen / carbon monoxide in the synthesis gas is usually 0.7 to 1 in volume ratio, but may be outside this range.
The reaction system may be a fixed bed (gas phase) system in which synthesis gas is blown into the reactor filled with the iron-based catalyst of the present invention and reacted, or synthesized in a slurry in which the iron-based catalyst of the present invention is dispersed in a solvent. A slurry bed (liquid phase) system in which gas is blown to react may be used.

  Prior to the FT reaction, the iron-based catalyst needs to be activated (reduced). The reduction treatment is performed by bringing a reducing gas such as synthesis gas or hydrogen or carbon monoxide into contact with an iron-based catalyst at a temperature of about 300 ° C. for about 3 hours. The reaction mode during the reduction treatment may be a fixed bed method or a slurry bed method. By the reduction treatment, the iron oxide constituting the iron-based catalyst becomes active metallic iron or iron carbide.

The pressure in the FT reaction is preferably 0.5 to 5 MPa, and the temperature is preferably 220 to 300 ° C.
The reaction product includes a wide range of hydrocarbons having 1 to 100 or more carbon atoms, liquid hydrocarbons having 5 to 18 carbon atoms are used as fuel oil, and the wax content having 19 or more carbon atoms is separately hydrogenated. It can be converted into fuel oil.

  According to such a hydrocarbon production method, by using the above-described iron-based catalyst, the production ratio of liquid hydrocarbons having 5 or more carbon atoms is increased, and fuel oil can be efficiently synthesized. An iron-based catalyst containing silica or silica and activated carbon also has high cost performance during hydrocarbon synthesis.

Hereinafter, although a specific example is shown, this invention is not limited to this specific example.
(1) Preparation of iron-based catalysts of Examples A, B, and C The following aqueous solutions were prepared.
・ Solution A Ferrous sulfate heptahydrate aqueous solution concentration 1 mol / liter ・ Solution B Copper sulfate pentahydrate aqueous solution concentration 0.5 mol / liter ・ Solution C Potassium carbonate aqueous solution concentration 1 mol / liter ・ Solution D Sodium carbonate Aqueous solution (for pH adjustment) Concentration 2 mol / liter

  300 ml of ion exchange water was prepared in a 3 liter beaker and heated to 60 to 70 ° C. In advance, 360 ml of the solution A and 6.3 ml of the solution B are mixed, and the mixture and the solution D are added dropwise to the beaker at the same time, and stirred while maintaining the temperature at 60 to 70 ° C. and pH 8.0 to 8.1. The temperature was kept at 60 to 70 ° C. and aged for 3 hours with stirring.

  The produced iron hydroxide precipitate was filtered and washed with ion-exchanged water. Subsequently, 5.1 ml of the washed precipitate was impregnated with the solution C and mixed well. The precipitate was then dried at 110 ° C. for 12 hours and calcined in the atmosphere at 400 ° C. for 3 hours. The fired product was pulverized and sized so as to pass through a sieve having a particle size of 60 μm, and the catalyst of Example A was obtained.

Also, except for mixing the ion-exchanged water 300ml water glass solution (3.6 g as SiO ₂₎ it is the same manner to obtain a catalyst of Example B.
Further, a catalyst of Example C was obtained by the same operation except that 300 ml of the ion-exchanged water was mixed with a water glass solution (3.6 g as SiO ₂ ) and 3.6 g of activated coke.

(2) Preparation of iron-based catalysts of Comparative Examples D, E, and F The following aqueous solutions were prepared.
・ Solution E Ferrous nitrate nonahydrate concentration 1 mol / liter ・ Solution F Copper sulfate trihydrate aqueous solution concentration 0.5 mol / liter ・ Solution C Potassium carbonate aqueous solution concentration 1 mol / liter ・ Solution G Ammonium carbonate Aqueous solution (for pH adjustment) Concentration 2 mol / liter

  300 ml of ion exchange water was prepared in a 3 liter beaker and heated to 60 to 70 ° C. In advance, 360 ml of the solution E and 6.3 ml of the solution F were mixed, and the mixture and the solution G were added dropwise to a beaker at the same time while stirring at a temperature of 60 to 70 ° C. and a pH of 8.0 to 8.1. The temperature was kept at 60 to 70 ° C. and aged for 3 hours with stirring.

  The produced iron hydroxide precipitate was filtered and washed with ion-exchanged water. Subsequently, 5.1 ml of the washed precipitate was impregnated with the solution C and mixed well. The precipitate was then dried at 110 ° C. for 12 hours and calcined in the atmosphere at 400 ° C. for 3 hours. The fired product was pulverized and sized so as to pass through a sieve having a particle size of 60 μm to obtain a catalyst of Comparative Example D.

Also, except for mixing the ion-exchanged water 300ml water glass solution (3.6 g as SiO ₂₎ it is the same manner to obtain a catalyst of Comparative Example E.
Further, a catalyst of Example F was obtained by the same operation except that 300 ml of the above ion-exchanged water was mixed with a water glass solution (3.6 g as SiO ₂ ) and 3.6 g of activated coke.

Table 1 shows the physical property data of the six types of iron-based catalysts thus prepared.
Further, XRD (X-ray diffraction method) was measured for each of the catalysts of Examples A, B, and C and Comparative Examples D, E, and F. The X-ray diffraction pattern is shown in FIGS. It can be seen that in Comparative Examples E and F, the iron particles are fine and no peak is observed.

  1 and 2, it can be seen that the catalysts of Examples A, B, and C have both a magnetite structure and a hematite structure, and the catalysts of Comparative Examples D and E have only a hematite structure.

Subsequently, hydrocarbons were synthesized from these 6 kinds of iron catalysts using synthesis gas as a raw material.
50 ml of n-hexadecane as a solvent and 3 g of the iron-based catalyst were charged into a continuously stirred slurry bed reactor having a capacity of 100 ml.
First, reduction treatment was performed. The reduction conditions are as follows.
Reducing gas: synthesis gas (H ₂ / CO = 1)
W (catalyst amount): 3 g
F (gas flow rate): 150 cc / min.
Temperature: 300 ° C
Pressure: 0.5 MPa

Next, FT reaction was performed. The reaction conditions are as follows.
Reaction gas: synthesis gas (H ₂ / CO = 1)
W (catalyst amount): 3 g
F (gas flow rate): 150 cc / min.
Temperature: 260 ° C
Pressure: 2.0 MPa

  The performance of the catalyst during the synthesis of this hydrocarbon was evaluated, and the results are shown in Table 2.

In Table 2,
“CO conversion rate” is the rate at which the introduced carbon monoxide reacts to change into hydrocarbons or carbon dioxide.
The “CO ₂ selectivity” is a ratio in which carbon monoxide in the reaction gas becomes carbon dioxide instead of hydrocarbon.
“Hydrocarbon selectivity” indicates the proportion of each component in the generated hydrocarbon.
“STY” indicates the production rate of liquid hydrocarbons of C5 or more per unit amount of catalyst.
“Raw material cost” is a cost ratio per weight of the catalyst, and is shown as a relative value of 100 for Example A.
“Cost performance” is obtained by dividing STY by the raw material cost, and is shown as a relative value with the value of Example A as 100.

  From Table 2, the catalysts of Examples A-C show comparable or better performance in the slurry bed reactor compared to the catalysts of Comparative Examples D-F. Furthermore, in terms of raw material cost (relative ratio), the catalysts of Examples A to C are less expensive than the catalysts of Comparative Examples D to F, and therefore the production amount of hydrocarbons having 5 or more carbon atoms per catalyst cost It can be seen that the ratio is high and the cost performance is excellent.

It is a graph which shows the X-ray-diffraction pattern of the catalyst of an Example. It is a graph which shows the X-ray-diffraction pattern of the catalyst of a comparative example.

Claims (6)

  An iron-based catalyst for Fischer-Tropsch synthesis reaction, comprising iron oxide particles having a magnetite structure and iron oxide particles having a hematite structure.   The iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 1, further comprising silica.   The iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 1, further comprising silica and activated carbon.   A method for producing an iron-based catalyst for Fischer-Tropsch synthesis reaction, which comprises producing a precipitate of iron hydroxide from an aqueous iron sulfate solution and calcining the precipitate.   5. The method for producing an iron-based catalyst for Fischer-Tropsch synthesis reaction according to claim 4, wherein the iron sulfate aqueous solution contains a silica precursor or a silica precursor and activated carbon. A method for producing hydrocarbons, comprising synthesizing hydrocarbons from synthesis gas containing carbon monoxide and hydrogen using the iron-based catalyst for Fischer-Tropsch synthesis reaction according to any one of claims 1 to 3.

Images