JP5552351B2 - Catalyst carrier and method for producing the same - Google Patents

Description

  The present invention relates to an alumina catalyst support and a method for producing the same, and more particularly to a catalyst support used for producing ethylene oxide and a method for producing the same.

  The alumina porous body is used as a catalyst carrier for various chemical reactions. For example, it may be used as a catalyst carrier for producing ethylene oxide by partially oxidizing ethylene.

  The production of ethylene oxide is generally carried out by direct vapor phase oxidation of ethylene with molecular oxygen in the presence of a silver catalyst. The alumina porous body is used as a carrier for this silver catalyst (see, for example, Patent Document 1 and Patent Document 2).

  In the method for producing an alumina catalyst carrier for partial oxidation described in Patent Document 1, the alumina catalyst carrier for partial oxidation comprises low soda alumina powder, mullite inorganic binder, alumina secondary particles and mullite inorganic binder. It is manufactured by calcining after containing 1 to 15% by weight in the total amount or containing 0.01 to 2.0% by weight of colloidal silica with respect to the amount of secondary alumina particles.

  In the method for producing an α-alumina porous carrier used for a catalyst carrier for producing ethylene oxide described in Patent Document 2, the catalyst carrier for producing ethylene oxide comprises α-alumina powders 92 to 97 of low soda alumina secondary particles. To 100 parts by weight of an alumina raw material consisting of 3 parts by weight and 3-8 parts by weight of a mullite inorganic binder, 2.3 to 4.0 parts by weight of carboxymethyl cellulose is added to form a molded body, and the molded body is used as a roller. It is manufactured by firing at a temperature of 1520 to 1560 ° C. and 5 to 8 hours using a hearth kiln.

Japanese Patent Publication No. 2-49779 Japanese Patent No. 3469746

  The following analysis is given from the perspective of the present invention.

  For example, in the production of ethylene oxide, the reaction efficiency from ethylene to ethylene oxide is also affected by the catalyst carrier.

  In the background art described in Patent Document 1, improvement in specific surface area, wear strength, and crushing strength is achieved. In the background art described in Patent Document 2, a catalyst carrier that can be rapidly fired and has uniform physical properties is manufactured. However, the catalyst carriers described in Patent Document 1 and Patent Document 2 do not have the purpose of improving the reaction efficiency.

  The object of the present invention is to provide a catalyst carrier capable of further enhancing the catalyst performance and a method for producing the same.

According to the first aspect of the present invention, the catalyst carrier is an alumina-based porous body. The catalyst support contains mullite derived from a silimanite group mineral. Catalyst support, and _Al 2 _{O 3} component of 92.5 wt% ～95.9 wt%, and the SiO ₂ component of 3.7 wt% to 7.0 wt%, and other components of 1 wt% or less, Containing.

  According to a preferred embodiment of the first aspect, the catalyst carrier further contains silica derived from a sillimanite group mineral.

  According to a preferred form of the first aspect, the mullite and silica contain those produced by thermal decomposition of a sillimanite group mineral.

  According to the second aspect of the present invention, the catalyst carrier production method comprises 80% by mass to 95% by mass of alumina, 5% by mass to 20% by mass of the binder with respect to the total mass of the alumina and the binder. , And a step of firing the mixture at 1400 ° C. to 1600 ° C. The binder is derived from a sillimanite group mineral.

  According to a preferred embodiment of the second aspect, the method for producing a catalyst carrier further includes a step of thermally decomposing the sillimanite group mineral to produce a binder containing mullite before the step of producing the mixture.

  According to a preferred form of the second aspect, the binder further contains silica.

According to a preferred mode of the second aspect, the binder, _Al 2 _{O 3} component 58 wt% to 62 wt%, the SiO ₂ component 36 wt% to 39 wt%, and other components 5 wt% or less contains.

  The reaction efficiency can be increased by using the catalyst carrier of the present invention and the catalyst carrier produced by the production method of the present invention. For example, the production efficiency of ethylene oxide can be increased by using it as a catalyst carrier in the synthesis reaction of ethylene oxide.

2 is an X-ray diffraction pattern of the catalyst support produced in Example 1. FIG.

The catalyst carrier of the present invention will be described. The catalyst carrier of the present invention is an alumina-based porous body. The catalyst carrier of the present invention contains α-alumina (Al ₂ O ₃ ) as a substrate and mullite (3Al ₂ O ₃ · 2SiO ₂ ) as a binder. The binder preferably contains silica (SiO ₂ ).

In the catalyst carrier of the present invention, the α-alumina content is preferably 75% by mass to 90% by mass, and the mullite content is preferably 10% by mass to 25% by mass. When the catalyst carrier contains silica, the silica content is preferably 0.5% by mass to 1% by mass. In terms of chemical components, in the catalyst carrier of the present invention, the content of the Al ₂ O ₃ component is preferably 92.5 mass% to 95.9 mass%, and 93.7 mass% to 94.2 mass%. % Is more preferable. The content of the SiO ₂ component is preferably 3.7% by mass to 7.0% by mass, and more preferably 5.4% by mass to 5.8% by mass. The content of other components (impurities) is preferably 1% by mass or less. Examples of other components include iron oxide (Fe ₂ O ₃ ), titanium oxide (TiO ₂ ), calcium oxide (CaO), magnesium oxide (MgO), sodium oxide (Na ₂ O), and potassium oxide (K ₂ O). ) And zirconium oxide (ZrO ₂ ).

  The catalyst carrier of the present invention preferably does not contain crystalline silica, or even if it contains it, the amount is very small. For example, in the X-ray diffraction pattern of the catalyst support of the present invention, it is preferable that crystalline silica is not detected or, if detected, sufficiently small compared to the peaks of alumina and mullite.

  A preferable water absorption in the catalyst carrier of the present invention is 33% by mass to 36% by mass.

Preferred specific surface area of the catalyst carrier of the present invention ^is 1.19m ² /g~1.23m 2 / g.

  The preferred crushing strength in the catalyst carrier of the present invention is 65N or more.

  A preferable wear rate in the catalyst carrier of the present invention is 1% or less.

  Mullite and silica in the catalyst carrier of the present invention function as a binder. Mullite and silica may be added independently, or may be generated by thermal decomposition of natural minerals or synthetic minerals.

As a mineral which produces | generates a mullite and a silica by thermal decomposition, a sillimanite group mineral is mentioned, for example. The sillimanite group mineral is an Al ₂ O ₃ .SiO ₂ component-based natural mineral. There are three types of sillimanite minerals: sillimanite (sillimanite), kyanite (kyanite, kyanite), and andalsite (andalusite, andalusite). However, both can be used in the present invention.

  Next, the manufacturing method of the catalyst carrier of this invention is demonstrated.

  First, an alumina powder as a substrate and a binder are mixed to prepare a mixture.

  The alumina powder is preferably α-alumina. The average particle diameter of the primary particles of the alumina powder is preferably 1 μm to 5 μm. The average particle size of the secondary particles of the alumina powder is preferably 30 μm to 60 μm. The alumina powder is preferably a calcined product.

  As a binder, it is preferable to use a mixture of mullite and silica or a sillimanite group compound. When a sillimanite group mineral is used, a fired or calcined material may be used as a binder, or a material that has not been fired or calcined may be used as a binder.

  In the case of producing a binder by firing a sillimanite group mineral, the calcination temperature of the sillimanite group mineral is preferably such that the sillimanite group mineral is decomposed into mullite and silica (for example, 1550 ° C. to 1800 ° C.). Since the decomposition temperature of sillimanite, kayanite, and andalusite may differ depending on the production area, etc., a suitable heating temperature is set depending on the type used. Moreover, when using a sillimanite group mineral, any 1 type may be used among a sillimanite, a kayanite, and an andalusite, and multiple types may be used.

In the binder, the content of the Al ₂ O ₃ component is preferably 58% by mass to 62% by mass. The content of SiO ₂ component is preferably a 36 wt% to 39 wt%. The content of other components (impurities) is preferably 5% by mass or less. Examples of other components include iron oxide (Fe ₂ O ₃ ), titanium oxide (TiO ₂ ), calcium oxide (CaO), magnesium oxide (MgO), sodium oxide (Na ₂ O), and potassium oxide (K ₂ O). ) And zirconium oxide (ZrO ₂ ).

  The binder produced by firing the sillimanite group mineral preferably contains crystalline silica detected by X-ray diffraction measurement. Most of the crystalline silica is produced by thermal decomposition of a sillimanite group mineral. In the X-ray diffraction measurement of the unfired sillimanite group mineral, the peak of each mineral contained is detected.

  The addition rate of the binder is preferably 1% by mass to 30% by mass and more preferably 1% by mass to 15% by mass with respect to the total mass of the alumina powder and the binder. By setting the addition rate of the binder having the above composition within this range, preferable conversion and selectivity can be obtained when used as a catalyst carrier for producing ethylene oxide.

  Next, a solvent (for example, water), a molding binder, and a pore forming material are added to the mixture of the alumina powder and the binder.

  As the molding binder, carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, or the like can be added. The addition rate of the molding binder is preferably 2% by mass to 10% by mass with respect to the total mass of the alumina powder and the binder.

  The pore-forming material is a porous material for the catalyst carrier produced by calcination. As the pore forming material, walnut grains having an average particle diameter of 125 μm to 1000 μm, nut shells, petroleum coke, carbon powder, graphite, polyethylene, and the like can be used. The addition rate of the pore forming material can be, for example, 1% by mass to 15% by mass with respect to the total mass of the alumina powder and the binder.

  Next, the mixture is formed into a predetermined shape. As the molding method, a suitable method such as extrusion molding can be appropriately selected.

  Next, the molded body is fired. The molding conditions can be, for example, a firing temperature of 1400 ° C. to 1600 ° C. and a firing time of 2 hours to 5 hours. Thereby, a catalyst carrier can be manufactured.

  When silica is present in the binder, it is considered that at least a portion thereof reacts with the alumina of the substrate to form mullite by firing.

  When the catalyst carrier of the present invention is used for producing ethylene oxide, silver as a catalyst is supported on the catalyst carrier.

[Manufacture of catalyst carrier]
The catalyst carriers of the present invention with different binder materials were prepared and the physical properties of each were measured. As the alumina raw material, the average particle size when the secondary particles are pulverized into primary particles is 1 μm to 3 μm, the central particle size of spherical secondary particles (particle size with a cumulative degree of 50%) is 35 μm to 55 μm, and the specific surface area is about Low soda α-alumina having a concentration of ₂ m ² / g and a Na ₂ O concentration of 0.1% by mass or less was used. A binder having the composition shown in Table 1 was used. When the “Presence / absence of pre-mixing firing” column is “Yes”, the sillimanite group mineral is calcined at about 1550 ° C. and thermally decomposed into mullite and crystalline silica is used as the binder. In the case of “None”, the sillimanite group mineral is used as a binder as it is without firing. The average particle size of the binder is 1 μm to 10 μm. Further, as a comparative example, a catalyst carrier using a binder other than the silimanite group mineral was produced. The composition of the binder in the comparative example is shown in Table 2. In Table 2, “Yes” in the “Presence / absence of firing before mixing” column is fired at 1550 ° C. The mineral of Examples 3 and 4 is a mixture of sillimanite and kyanite 50% each.

  In Examples 1 to 8, first, a mixture of 85% by mass of α-alumina powder and 15% by mass of a binder was prepared, and 8% by mass of methylcellulose as a molding binder was added to the mass of the mixture. The exchange water was added in an amount of 35% by mass relative to the mass of the mixture, and kneaded using a kneader. Next, the kneaded product was formed into a cylindrical shape having an outer diameter of 9.5 mm, an inner diameter of 4.3 mm, and a height of 9.5 mm by extrusion molding, and the molded product was dried in an oven at 80 ° C. for 16 hours. Next, the dried molded product was calcined by holding at a maximum temperature of 1450 ° C. for 4 hours to produce a catalyst carrier. Tables 3 and 4 show physical property values and compositions of the respective catalyst carriers.

  In Example 9, a mixture of 91% by mass of α-alumina powder and 9% by mass of a binder was prepared, and in Example 10, a mixture of 83% by mass of α-alumina powder and 17% by mass of a binder was prepared. Other than that is the same as the said method of Examples 1-8.

[Specific surface area measurement]
The specific surface area of the catalyst support was measured by the BET method (continuous flow type BET one-point method nitrogen gas adsorption). The apparatus used is a Macsorb HM-1210 manufactured by Mountec.

[Measurement of water absorption rate]
The water absorption rate of the catalyst carrier was measured by a boiling method according to JIS R2205.

[Measurement of crushing strength]
The crushing strength of the catalyst carrier was measured using a Kiya hardness meter (KHT-20 manufactured by Fujiwara Seisakusho). The numerical value of a table | surface is an average value of 25 measured values.

[Measurement of wear rate]
75 g of a sample was put in a stainless steel pot (width 91 mm × diameter 91 mm) and ground with a ball mill at 106 rpm for 30 minutes. The value obtained from the mass before pulverization / the mass after pulverization was defined as the wear rate.

[Measurement of composition]
The composition of the catalyst carrier was measured using a fluorescent X-ray apparatus (ZSX100e manufactured by Rigaku Corporation).

[Measurement of X-ray diffraction pattern]
The X-ray diffraction pattern of the catalyst support in Example 1 was measured. The measuring device is a Rigaku X-ray diffraction device (RINT-TTRIII). The measurement conditions are the concentration method (tube voltage 50 kV, tube current 50 mA), scan speed 4 ° / min, scan step 0.02 °, and scan range 10 ° to 70 °. FIG. 1 shows the measurement result of the X-ray diffraction pattern of the catalyst carrier. There was no change in the X-ray diffraction pattern of the catalyst support even when the fired sillimanite group mineral was used as a binder or when the sillimanite group mineral was not fired as a binder. According to the X-ray diffraction pattern of the catalyst support, α-alumina and mullite were detected, but crystalline silica was not detected. Since the binder obtained by calcining the sillimanite group mineral contains crystalline silica, it means that the catalyst carrier does not contain (or hardly contains) crystalline silica. It is presumed that the SiO ₂ component reacts with the alumina of the substrate (for example, becomes mullite) or the remaining amount is reduced or becomes amorphous due to the firing at the time of preparing the catalyst carrier. In addition, when unsintered sillimanite group mineral is used as a binder, even if the binder is decomposed into mullite and crystalline silica by firing at the time of preparing the catalyst carrier, the crystalline silica similarly reacts with alumina. Or it is guessed that it became amorphous.

[Catalyst performance test]
A catalyst performance test was performed on the catalyst carrier of the present invention. In the catalyst performance test, the catalyst support of Example 1 and Comparative Example 1 was loaded with a silver catalyst under the same conditions, and the reaction temperature and the selectivity at a predetermined conversion rate in the reaction from ethylene to ethylene oxide were measured.

A catalyst carrier carrying a catalyst is filled in a heating type double tube stainless steel reactor with an inner diameter of 25 mm and a tube length of 11000 mm. The packed bed contains 20% ethylene, 7% oxygen, and 7% carbon dioxide gas. %, The balance consisting of methane, nitrogen, argon and ethane, and further introducing a mixed gas consisting of 1 ppm of ethylene dichloride, raising the reaction pressure to 24 kg / cm ² G, the space velocity 5500 Hr ⁻¹ , and the heating medium temperature 230 ° C. Reaction was performed. Table 5 shows the reaction temperature and selectivity after 10 days and 1 year after the start of the reaction. The selectivity is a value calculated by [number of moles of ethylene changed to ethylene oxide] / [number of moles of reacted ethylene] × 100. The reaction temperature indicates the reaction temperature when the conversion rate is 10%. Here, the conversion rate is a value calculated by [number of moles of reacted ethylene] / [number of moles of ethylene in the raw material gas] × 100.

  The catalyst carrier according to Example 1 was found to have a higher reaction efficiency than the catalyst carrier according to Comparative Example 1, regardless of immediately after production and after one year. In particular, even with a catalyst carrier one year after production, the reaction temperature could be lowered by 7 ° C., and the selectivity could be improved by 6%. From this, it can be seen that the catalyst carrier of the present invention can increase the reactivity and has an economically excellent effect.

  The catalyst carrier and the method for producing the same according to the present invention have been described based on the above embodiment, but are not limited to the above embodiment, and are within the scope of the present invention and based on the basic technical idea of the present invention. It goes without saying that various modifications, changes, and improvements can be included in the embodiment. Further, various combinations, substitutions, or selections of various disclosed elements are possible within the scope of the claims of the present invention.

  Further problems, objects, and developments of the present invention will become apparent from the entire disclosure of the present invention including the claims.

Claims (7)

An alumina-based porous body,
A catalyst carrier containing mullite derived from a sillimanite group mineral ,
And _Al 2 _{O 3} component of 92.5 wt% ～95.9 wt%,
And the SiO ₂ component of 3.7 wt% to 7.0 wt%,
And 1% by mass or less of other components .   2. The catalyst carrier according to claim 1, further comprising silica derived from a sillimanite group mineral. The catalyst support according to claim 1 or 2 , wherein the mullite and silica contain those produced by pyrolysis of a silimanite group mineral. Producing a mixture containing 80% by mass to 95% by mass alumina and 5% by mass to 20% by mass binder based on the total mass of alumina and the binder;
Calcining the mixture at 1400 ° C. to 1600 ° C.,
The method for producing a catalyst carrier, wherein the binder is derived from a sillimanite group mineral. Before the step of making the mixture,
The method for producing a catalyst carrier according to claim 4 , further comprising a step of thermally decomposing a sillimanite group mineral to produce the binder containing mullite. The method for producing a catalyst carrier according to claim 5 , wherein the binder further contains silica. The binder is, _Al 2 _{O 3} component 58 wt% to 62 wt%, claim 4, characterized in that it contains SiO ₂ component 36 wt% to 39 wt%, and other components 5 wt% or less process for preparing a catalyst carrier according to any one of 1-6.

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