JP2008136907A - Catalyst for synthesis gas production - Google Patents

Abstract

Provided is a catalyst for producing a synthesis gas by reacting an organic compound with steam, oxygen, and carbon dioxide, which does not easily cause catalyst poisoning due to carbon deposition.
The present invention relates to a catalyst for producing a synthesis gas containing hydrogen and carbon monoxide by reacting an organic compound gas with steam and / or carbon dioxide or oxygen gas. And a catalyst metal supported on the carrier, wherein the catalyst metal has an electronegativity of 1.35 to 1.55 by allred locomotive. It is. The catalyst metal is made of at least one metal selected from the group consisting of rhodium, ruthenium, iridium, palladium and platinum, and has a particle diameter of 1 nm to 100 nm. The supported amount of the catalyst metal is 0.01 to 20% by weight with respect to the support, and 50% of the support is preferably supported within 1000 μm from the outermost layer of the support.
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Description

  The present invention relates to a catalyst for producing a synthesis gas by reacting an organic compound with steam, oxygen and carbon dioxide.

  Syngas is a mixed gas composed of hydrogen and carbon monoxide, and is widely used as a raw material for ammonia, methanol, acetic acid and the like. Conventionally known methods for producing synthesis gas include a steam reforming method in which an organic compound gas such as methane reacts with steam (steam), and a partial oxidation method in which an organic compound reacts with oxygen.

In addition, carbon monoxide constituting the synthesis gas has utility value alone as a synthesis raw material for hydroformylation. Thus, in recent years, a method of reacting carbon dioxide with an organic compound is known for the purpose of increasing the carbon monoxide ratio in the synthesis gas.
Japanese Patent Application No. 05-208801 Japanese Patent Application No. 06-279003 Japanese Patent Application No. 09-168740

An advantage of the process of reacting carbon dioxide (CO ₂ reforming method) is that, as described above, the carbon monoxide content in the synthesis gas is higher than that of the steam reforming method. Since the steam reforming method uses the reaction of the following formula (1) as a main reaction, only 1 mol of carbon monoxide is generated with respect to 3 mol of hydrogen, which is inefficient as a carbon monoxide production process. is there. In contrast, when carbon dioxide is applied, equimolar amounts of hydrogen and carbon dioxide are generated by the reaction of the following formula (2). In this process, depending on the amount of carbon dioxide supplied, the reaction of the following formula (3) also occurs, so that carbon monoxide can be produced more efficiently.

In addition to the carbon monoxide production efficiency, the CO ₂ reforming method has the advantage that carbon dioxide, which is taken up as a cause of environmental problems, can be effectively used in addition to the production efficiency of carbon monoxide. There is also.

As a problem in the synthesis gas production method, there is a problem of catalyst poisoning due to carbon deposition (coking). Carbon deposition is caused by partial decomposition of an organic compound as a raw material and carbon monoxide as a product, and the deposited carbon decreases the activity of the catalyst. This carbon deposition problem can occur in any process of steam reforming, partial oxidation, and CO ₂ reforming.

  As a method for suppressing carbon deposition, it is possible to reduce the partial pressure of the organic compound and product in the reaction system. For this reason, as a countermeasure taken conventionally, there is a method of increasing the supply amount of steam, oxygen gas, and carbon dioxide gas and lowering the reaction pressure. However, when such countermeasures are taken, a large amount of steam and carbon dioxide gas are required, and the energy cost for preheating them is excessive, and there is also an inconvenience of an increase in cost due to an increase in the size of the reaction apparatus. That is, as a countermeasure against the problem of carbon deposition, it can be said that it is preferable to measure improvement of the catalyst itself, not from the viewpoint of process control as described above.

  The present invention has been made based on the background as described above, and is a catalyst for producing a synthesis gas by reacting an organic compound with steam, oxygen, and carbon dioxide. The purpose is to provide something that does not easily cause poison.

  As a result of diligent studies to solve the above problems, the present inventors have found the relationship between the electronegativity of the catalyst metal constituting the catalyst and the catalyst poisoning, and have come up with the present invention. That is, the present invention relates to a catalyst for producing a synthesis gas containing hydrogen and carbon monoxide by reacting an organic compound gas with steam and / or carbon dioxide or oxygen gas. The catalyst metal is a catalyst for syngas production, wherein the catalyst metal has an electronegativity of 1.35 to 1.55 by all red locomotive.

  Hereinafter, the present invention will be described in more detail. In the catalyst according to the present invention, the catalyst metal has an electronegativity of 1.35 to 1.55 in order to suppress carbon deposition activity during the reaction. This electronegativity is based on the value of Allred-Rochow. A preferable catalyst metal is composed of at least one metal selected from the group consisting of rhodium, ruthenium, iridium, palladium, and platinum. Moreover, it is preferable that the particle diameter of a catalyst metal is 1 nm or more and 100 nm or less. This is because the particle size is in an optimum range for maintaining high catalytic activity.

  The amount of the catalyst metal supported is preferably 0.01 to 20% by weight with respect to the support. If it is less than 0.01% by weight, it does not function as a catalyst, and if it exceeds 20% by weight, it is not economical and aggregation of the catalyst metal tends to occur. This catalyst metal is preferably supported on the surface layer, not inside the support. Specifically, it is preferable that almost all (0.1 to 3% by weight) of the catalyst is supported within 1000 μm from the outermost layer of the support. The reason why such a state is preferred is that the reaction sites are concentrated on the catalyst surface when the reaction rate is high and the diffusion resistance in the catalyst particles is high. In order to support the catalyst metal only on the surface layer as described above, a method is generally used in which the support is immersed in a catalyst component solution that is strongly adsorbed on the support for a short time.

The carrier constituting the catalyst preferably has a specific surface area of 0.5 to 50 m ² / g. By setting the specific surface area in such a range, the carbon deposition activity can be suppressed synergistically with the use of the catalyst metal within the above-mentioned electronegativity range. The carrier is preferably made of a metal oxide, such as aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), calcium oxide (CaO), oxide. A metal oxide containing one or more of zirconium (ZrO ₂ ) and lanthanum oxide (La ₂ O ₃ ) is preferable. These composite oxides may also be used. The particle size of the carrier is preferably 0.1 to 10 mm, more preferably 1 to 5 mm. This is because if the carrier particle size is small, the pressure loss during the reaction increases, and if it is too large, the reaction efficiency deteriorates. In addition, the form of a support | carrier uses the thing of various forms, such as granular form, spherical shape, column shape, and cylindrical shape, The shape is suitably selected according to the system of the reaction bed to be used.

  About the specific surface area of a support | carrier, it can be made a preferable range by baking a metal oxide at 300-1300 degreeC before carrying | supporting a catalyst metal, Preferably it is 650-1200 degreeC. Alternatively, the specific surface area can also be adjusted by firing the catalyst metal on the metal oxide and firing at 150 to 1000 ° C., preferably 500 to 900 ° C. In this case, the specific surface area of the obtained catalyst or carrier metal oxide can be controlled by the firing temperature and firing time.

  The catalyst production method according to the present invention is preferably based on an impregnation method. In the production of the catalyst according to the present invention by the impregnation method, a salt containing a catalytic metal or an aqueous solution thereof is added to and mixed with a carrier (metal oxide) dispersed in water, and then the carrier is separated from the aqueous solution and then dried. Bake. Further, as the impregnation method, it is also effective to add a metal salt solution corresponding to the pore volume little by little to the exhausted carrier so that the surface of the carrier is uniformly wetted, and then drying and firing.

  In these production methods, the catalyst metal salt is preferably an inorganic acid salt such as nitrate or chloride, or an organic acid salt such as acetate or oxalate. Alternatively, a metal acetylacetonate salt or the like may be dissolved in an organic solvent such as acetone and impregnated in the carrier.

  The drying temperature of the carrier after impregnation is 100 to 200 ° C., preferably 100 to 150 ° C. in the case of impregnation with an aqueous solution, and when impregnated with an organic solvent, the drying temperature is 50 to 100 ° C. higher than the boiling point of the solvent. To do. The firing temperature and firing time after drying are appropriately selected according to the specific surface area of the obtained carrier, but are generally 500 to 1000 ° C.

  In addition, the metal oxide which is a support | carrier can be a metal oxide obtained by baking a commercially available metal oxide and a commercially available metal hydroxide. The purity of the metal oxide is 98% by weight or more, preferably 99% by weight or more. Also, components that enhance carbon deposition activity and components that decompose under high temperature / reducing gas atmosphere, such as iron and nickel, should be avoided, and these impurities are 1% by weight or less, preferably What is 0.1 weight% or less is preferable.

The synthesis gas reaction process to which the catalyst according to the present invention can be applied includes (1) a reaction process in which an organic compound reacts with steam, and a reaction process in which an organic compound reacts with steam and oxygen (steam reforming). Method), (2) Reaction process (partial oxidation method) of reacting organic compound and oxygen, (3) Reaction process of reacting organic compound and carbon dioxide (CO ₂ reforming method) Can also handle processes.

  In these methods, as the organic compound, lower hydrocarbons such as methane, ethane, propane, butane and naphtha, and non-hydrocarbon compounds such as methanol and dimethyl ether are used, and methane is preferred. In the present invention, natural gas (methane gas) containing carbon dioxide gas can be used as a reaction raw material.

In the steam reforming method, the reaction temperature is 600 to 1200 ° C., preferably 600 to 1000 ° C., and the reaction pressure is 1 to 40 kg / cm ² G, preferably 5 to 30 kg / cm ² . The gas hourly space velocity of the reaction is carried out in a fixed bed system (GHSV) is, 1000～10000Hr ^-1, preferably is 2000~8000hr ^-1.

  About the steam usage rate with respect to a raw material carbon-containing organic compound, it is 0.5-5 mol, Preferably it is 1-2 mol, More preferably, it is 1-1.5 mol per 1 mol of carbon in a raw material organic compound. When steam reforming is performed using the catalyst according to the present invention, as described above, even if the amount of steam used is maintained at 2 mol or less per 1 mol of carbon, carbon deposition is suppressed, which is industrially advantageous. Syngas can be produced. In this regard, considering that the conventional method required 2 to 5 moles of steam per mole of carbon, it is a great advantage that the reforming reaction can proceed smoothly by using steam of 2 moles or less.

In the steam reforming method, a mixed gas of steam and carbon dioxide may be reacted. At this time, the mixing ratio of steam and carbon dioxide is not particularly limited, but in general, it is preferably 0.1 to 10 in terms of H ₂ O / CO ₂ molar ratio.

  In the reforming by the partial oxidation method, the above-described hydrocarbon-based and non-hydrocarbon-based organic compounds are used, and methane is preferable. On the other hand, oxygen, air, or oxygen-enriched air can be used as the oxygen source. In the present invention, natural gas (methane gas) containing carbon dioxide gas can also be advantageously used as a reaction raw material.

In the partial oxidation method, the reaction temperature is 500 to 1500 ° C., preferably 700 to 1200 ° C., and the reaction pressure is 5 to 50 kg / cm ² , preferably 10 to 40 kg / cm ² . Moreover, when performing reaction by a fixed bed system, gas space velocity is 1000-50000 hr < ^-1 >, Preferably it is 2000-20000 kg / cm < ² >. The use ratio of the organic compound and oxygen as the raw material is 0.1 to 4, preferably 0.5 to ₂ , in the ratio C / O ₂ between the number of moles of carbon and the number of moles of oxygen molecules in the raw material. In addition, since the partial oxidation method is a large exothermic reaction, it is possible to adopt an autothermic reaction method by adding water vapor or carbon dioxide to the raw material.

Then, in the CO ₂ reforming, the reaction temperature at 500 to 1200 ° C., preferably from 600 to 1000 ° C., the reaction pressure, 5~40kg / cm ^2, preferably 5~30kg / cm ^2. Also, if the reaction is carried out in a fixed bed, a gas space velocity, 1000～10000Hr ^-1, preferably 2000~8000hr ^-1. The use ratio of carbon dioxide with respect to the organic compound of the raw material is 0.5 to 20 mol, preferably 1 to 10 mol of CO ₂ per 1 mol of carbon in the raw material. In the CO ₂ reforming method using the catalyst according to the present invention, as described above, the synthesis gas is industrially produced while suppressing carbon deposition even if carbon dioxide is reduced to 3 moles or less per mole of carbon in the raw material. can do.

  The reaction of each of the above processes using the catalyst according to the present invention is carried out by various methods such as a fixed bed method, a fluidized bed method, a moving bed method, etc., preferably a fixed bed method.

In each of the above processes, the CO ₂ reforming method is advantageous for producing carbon monoxide. When showing the composition of the synthesis gas in the case of methane as a raw material by this _{process, H 2: 10~30vol%, CO} : 35~45vol%, unreacted _CO 2: _5~40vol%, unreacted _CH 4: 0 to 30 vol%, H2 0: 5 to ₂₀ vol%.

In the production of carbon monoxide, the first step includes a synthesis gas production step by a CO ₂ reforming method, and the second step includes a step of concentrating carbon monoxide using the obtained synthesis gas as a raw material. The concentration of carbon monoxide can be carried out by a method such as a cryogenic separation method commonly used for the carbon monoxide concentration method or an absorption method using an aqueous copper salt solution as an absorbing solution.

  As described above, the catalyst according to the present invention has a suppressed carbon deposition activity. According to the present invention, synthesis gas can be produced while suppressing carbon deposition accompanying the progress of the reaction, and its catalytic activity is stable for a long period of time.

  Hereinafter, preferred embodiments of the present invention will be described. In the present embodiment, catalysts were produced by combining various catalyst metals and carrier metal oxides, and their reaction activity and durability were tested.

Example 1 : Aluminum oxide was calcined in air at 800 ° C. for 1.5 hours, and this was sized to 1.5 to 3.0 mm to prepare a carrier (specific surface area: 18.6 m ² / g). And the ruthenium (III) chloride aqueous solution (ruthenium concentration: 0.05 weight%) was dripped little by little at this, and it mixed with every dropping, and the aqueous solution was impregnated. After impregnation, the impregnated body was dried and fired to obtain a ruthenium-supported alumina catalyst (ruthenium-supported amount: 0.025 wt%).

Examples 2 to 18 : As shown in Table 1, various catalysts were obtained by the impregnation method while changing the carrier and the metal salt. The process is basically the same as in the first embodiment.

Reaction test : A reforming reaction of methane was performed using each catalyst prepared above. In the reaction test, a predetermined amount of catalyst was previously reduced in a hydrogen stream at 700 ° C. for 1 hour, and then charged into the reactor. Then, a raw material gas having a composition corresponding to the reaction process was introduced, and the reaction was performed by changing the conditions of pressure, temperature, and gas space velocity. The conversion rate of methane during the reaction test and at the end of the test ((number of moles of methane in the raw material−number of moles of methane in the product) / number of moles of methane in the raw material × 100) was determined.

In the reaction test, each reaction process of the steam reforming method, the partial oxidation method, and the CO ₂ reforming method was performed. Moreover, the reaction test by the autothermal reforming method using two connected reactors was conducted. In autothermal reforming, the raw material gas consisting of methane gas and oxygen gas was heated and partially oxidized in the first reactor, and the reaction gas was further introduced into the second reactor for reforming. After the test, the conversion rate of methane was determined in the same manner as described above. Table 2 shows the results of the reaction test conducted in this embodiment.

  As can be seen from Table 2, in the methane reforming reaction using the catalyst according to each example, there is very little change in the reaction rate between the initial stage of the reaction and the end of the test. That is, it was confirmed that these catalysts have good durability. This is thought to be due to the suppression of carbon deposition activity of these catalysts.

Example of enrichment of carbon monoxide : The synthesis gas obtained in Reaction Example 18 was rich in carbon monoxide with a carbon monoxide / hydrogen molar ratio of 2.2. Therefore, the synthesis gas was brought into contact with a hydrochloric acid acidic CuCl solution absorbing solution to concentrate carbon monoxide. As a result, a concentrated gas of 96% carbon monoxide was obtained.

Claims (6)

In a catalyst for producing a synthesis gas containing hydrogen and carbon monoxide by reacting an organic compound gas with steam and / or carbon dioxide or oxygen gas,
A synthesis gas comprising a carrier and a catalyst metal supported on the carrier, wherein the catalyst metal has an electronegativity of 1.35 to 1.55 by allred locomotive. Catalyst. 2. The synthesis gas production according to claim 1, wherein the catalyst metal is made of at least one metal selected from the group consisting of rhodium, ruthenium, iridium, palladium and platinum, and the particle diameter of the catalyst metal is 1 nm or more and 100 nm or less. Catalyst. The synthesis gas according to claim 1 or 2, wherein the amount of the catalyst metal supported is 0.01 to 20% by weight with respect to the support, and 50% of the catalyst metal is supported within 1000 µm from the outermost layer of the support. Catalyst for production. The catalyst for syngas production according to any one of claims 1 to 3, wherein the specific surface area is 0.5 to 50 m ² / g. The support is made of at least one metal oxide selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, titanium oxide, calcium oxide, zirconium oxide, and lanthanum oxide. A catalyst for producing synthesis gas as described in 1. The catalyst for syngas production according to any one of claims 1 to 5, wherein the carrier has a particle diameter of 0.1 to 10 mm.