JP2005349393A - Catalyst for vapor-phase oxidation for production of phthalic anhydride from orthoxylene and/or naphthalene, its preparation method, and vapor-phase oxidation method using the catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst suitable for vapor-phase oxidation for the production of phthalic anhydride from orthoxylene and/or naphthalene, its preparation method and a vapor-phase oxidation method for producing orthoxylene and/or naphthalene using the catalyst. <P>SOLUTION: In a catalyst for vapor-phase oxidation for the production of phthalic anhydride from orthoxylene and/or naphthalene, comprising a catalyst active ingredient carried on an inert carrier, a material capable of providing water with a specific resistance of not less than 20,000 Ωcm (25°C) by the following treatment is used as the carrier. The treatment includes the steps of placing 300 ml of the carrier in a 500-ml conical beaker, drying it at 120°C for 2 h, adding pure water (amount of water absorption+220) ml to the dried carrier and heating the mixture at 90°C for 30 min under the atmospheric pressure. Here the amount of water absorption is expressed by the formula, amount of water absorption=A/B, wherein A=300 (ml)×packing density (g/ml)×water absorption (wt%)/100 and B=density of water (g/ml). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catalyst suitable for producing phthalic anhydride from orthoxylene and / or naphthalene, a preparation method thereof, and a gas phase oxidation method of orthoxylene (and / or naphthalene) using these catalysts.

  Production by gas phase oxidation of phthalic anhydride by gas phase oxidation of orthoxylene and / or naphthalene has been widely carried out industrially, and various gas phase oxidation catalysts to be used have been proposed.

  Although these gas-phase oxidation catalysts have some excellent performance, it is the continuation of researchers in the technical field to develop gas-phase oxidation catalysts with better catalyst performance, ie, activity, selectivity and lifetime. It has become a theme.

  An object of the present invention is a gas phase oxidation catalyst for producing phthalic anhydride from orthoxylene and / or naphthalene, which has excellent catalytic performance and can stably produce a target product in a high yield over a long period of time. And a gas phase oxidation method for producing phthalic anhydride from orthoxylene and / or naphthalene using the catalyst.

  In order to solve the above problems, the inventors of the present application focused on a carrier used as a catalyst for the production of phthalic anhydride, and as a result of intensive studies, when a commonly used carrier was washed in advance, the washing carrier was used. The catalyst for gas phase oxidation for producing phthalic anhydride from orthoxylene and / or naphthalene obtained in this way was found to have excellent catalytic performance, and the present invention was completed based on this finding.

  That is, the present invention relates to a gas phase oxidation catalyst for producing phthalic anhydride from orthoxylene and / or naphthalene obtained by supporting a catalytically active component on an inert carrier. A gas phase oxidation catalyst characterized by using a catalyst having a resistance of 20,000 Ωcm (25 ° C.) or more.

  (Treatment method) After taking 300 ml of carrier in a 500 ml conical beaker (conforming to JIS R-3503) and drying at 120 ° C for 2 hours, add (water absorption +220) ml of pure water and heat at 90 ° C for 30 minutes under normal pressure. Here, the amount of water absorption is represented by the following formula: water absorption amount = A / B where A = 300 (ml) × packing density (g / ml) × water absorption rate (wt%) / 100 B = density of water (g / ml).

  In the above formula, the packing density (D) is D = W1 (g) / 1000 ml (where W1 is a graduated cylinder when a dry carrier is filled into a 1000 ml graduated cylinder (inner diameter 65 mm) at a rate of 2000 ml / minute) Is the weight of the carrier to be filled in).

  The water absorption (M) is M = [(W3 (g) −W2 (g)) / W2 (g)] × 100 (W2 is the weight of the dry carrier 300 ml, and W3 is the dry carrier 300 ml. It is the weight when it is put in a stainless steel basket, boiled in boiling pure water for 30 minutes, then taken out, wiped off excess water with wet gauze and then weighed).

  The present invention is also a method for producing phthalic anhydride, characterized in that phthalic anhydride is produced by gas phase oxidation of orthoxylene and / or naphthalene in the presence of the above catalyst.

  Furthermore, the present invention relates to a gas phase oxidation catalyst for producing phthalic anhydride from orthoxylene and / or naphthalene obtained by supporting a catalytically active component on an inert carrier. This is a method for preparing a gas phase oxidation catalyst, characterized by using a catalyst that has been washed until its specific resistance reaches 20,000 Ωcm (25 ° C.) or more.

  (Treatment method) Take 300 ml of carrier in a 500 ml conical beaker, dry at 120 ° C. for 2 hours, add (water absorption + 220) ml of pure water, and heat at 90 ° C. for 30 minutes under normal pressure. Here, the amount of water absorption is represented by the following formula: water absorption amount = A / B, where A = 300 (ml) × packing density (g / ml) × water absorption rate (wt%) / 100 B = water Density (g / ml).

  The catalyst for vapor phase oxidation for producing phthalic anhydride from orthoxylene and / or naphthalene of the present invention is excellent in activity, selectivity and catalyst life, and can produce the desired compound in a high yield over a long period of time. it can.

  The material of the inert carrier used in the present invention is not particularly limited, and is generally used for the preparation of an oxidation catalyst used in the production of phthalic anhydride by gas phase oxidation of orthoxylene and / or naphthalene, or Any of the carriers known to be used can be used. For example, alumina, silica, silica-alumina, titania, magnesia, silica-magnesia, silica-magnesia-alumina, silicon carbide, silicon nitride, zeolite, and the like that are commonly used as carriers for gas phase oxidation catalysts can be mentioned.

  Among these, an inert carrier comprising silicon carbide or an inert carrier comprising silicon carbide as a main component is, for example, disclosed in JP-A-57-105241, in which phthalic anhydride is produced from orthoxylene and / or naphthalene. It is described that a silicon carbide self-sintered body is used as a catalyst support for the above.

  In the present invention, an inert carrier which is the silicon carbide self-sintered body and an inert carrier mainly composed of silicon carbide are preferably used. Among these, an inert carrier mainly composed of silicon carbide is particularly preferably used because it is inexpensive, has excellent thermal conductivity possessed by silicon carbide, and can be easily molded into a desired shape.

  The inert carrier having silicon carbide as a main component means a carrier of a type in which silicon carbide is a main component and this is mixed with an inorganic binder and calcined. The content of silicon carbide is preferably 70% by weight or more. Typical examples of the inorganic binder include silicon dioxide and mullite. Therefore, as a typical example of an inert carrier containing silicon carbide as a main component, a silicon carbide content of 70% by weight or more as described in JP-A-9-85096 is used. Mention may be made of inert carriers comprising silicon and mullite.

  In addition, an inert carrier mainly composed of steatite is also preferably used in the present invention.

There are no particular restrictions on the physical properties, shape, size, etc. of the inert carrier used in the present invention. Regarding physical properties, the specific surface area is 0.3 m ² / g or less, preferably 0.02 to 0.2 m ² / g, and the porosity is 0 to 35%, preferably 16 to 30%. The shape may be any of a spherical shape, a cylindrical shape, a ring shape, and the like. Also, for example, in the case of a spherical shape, the average particle size is about 2 to 15 mm, preferably about 3 to 12 mm.

  The present invention is characterized in that a carrier having a specific resistance of water of 20,000 Ωcm (25 ° C.) or more after the treatment is used. That is, when 300 ml of a carrier is placed in a 500 ml conical beaker, dried at 120 ° C. for 2 hours, added with pure water (water absorption amount + 220) ml, and heated at 90 ° C. for 30 minutes under normal pressure, the specific resistance of water after this treatment Is 20,000 Ωcm (25 ° C.) or more, preferably 25,000 to 1,000,000 Ωcm (25 ° C.), particularly preferably 30,000 to 1,000,000 Ωcm (25 ° C.).

  The specific resistance in the present invention is a value obtained by measuring the conductivity of water after the treatment at 25 ° C. with a conductivity meter and showing the reciprocal thereof. In the present invention, for example, the specific resistance is 20,000 Ωcm. It is displayed as 20,000 Ωcm (25 ° C.).

  A carrier having a specific resistance of 20,000 Ωcm (25 ° C.) or more after the treatment can be suitably prepared by washing the carrier with water, preferably pure water.

  One specific cleaning method is the operation of heating at 90 ° C. for 30 minutes under normal pressure, and the specific resistance of water after the treatment is 20,000 Ωcm (25 ° C.) or more, preferably 25,000 to 1, It is intended to be 000,000 Ωcm (25 ° C.), particularly preferably 30,000 to 1,000,000 Ωcm (25 ° C.). If the specific resistance of the water after the treatment is 20,000 Ωcm (25 ° C.) or more, the above operation may be performed once. In addition, when performing the said operation in multiple times, new water is used for every operation, and the specific resistance of the water after the said process is measured for every operation. The amount of water used is not particularly limited. For example, if the carrier is 300 ml, the water absorption amount is +220 ml for the first operation, and 220 ml of water is used for the first and subsequent operations.

  Prior to the washing with water, washing may be performed with an acidic aqueous solution such as nitric acid, a basic aqueous solution such as ammonia water, or an organic solvent such as alcohols. For example, when washing with an aqueous solution of nitric acid, the operation of heating at 90 ° C. under normal pressure may be repeated. In this case, subsequent water washing is necessary, but at the time of this water washing, it is not always necessary to heat at 90 ° C. under normal pressure.

  Further, there is no particular limitation on the means for washing the carrier, and the carrier may be washed in running water for a certain period of time, or simply immersed in a washing solution and allowed to stand for a certain period of time. It is preferable to wash the carrier until the treated water shows a certain specific resistance value.

  As described above, the support is washed, preferably washed with water, or by using a support having a specific resistance of 20,000 Ωcm (25 ° C.) or more after the treatment, an ortho catalyst having excellent catalytic performance. A catalyst for gas phase oxidation of xylene and / or naphthalene can be obtained.

  The catalyst for gas phase oxidation of orthoxylene and / or naphthalene of the present invention can be prepared according to a known method except that the above inert carrier is used as a carrier.

Production of phthalic anhydride from ortho-xylene and / or naphthalene Generally, a catalyst in which a catalytically active component containing (1) vanadium and (2) an oxide of titanium is supported on the above inert carrier is used.

  Among these, (1) vanadium, (2) titanium, (3) an oxide composition containing at least one element selected from alkali metal elements, rare earth elements, sulfur, phosphorus, antimony, niobium and boron is used as a catalyst active component. And a catalyst in which this is supported on the above inert carrier is preferable.

  The method for supporting the catalytically active substance on the inert carrier is not particularly limited, but a liquid substance containing the catalytically active substance while keeping a certain amount of the inert carrier in a rotating drum that can be heated from the outside and maintaining at 200 to 300 ° C. The method of spraying (slurry) and supporting the active substance is the simplest. At this time, the loading amount of the active substance on the inert carrier varies depending on the size and shape of the inert carrier to be used, but if it is spherical or cylindrical, 3-30 g active substance / 100 ml inert carrier, especially 5-5 20 g active substance / 100 ml inert carrier is preferred.

  The gas phase oxidation reaction according to the present invention can be carried out in accordance with a method generally used for carrying out various reactions, except that the gas phase oxidation catalyst is used as a catalyst. Usually, the vapor phase oxidation catalyst of the present invention is filled in a carbon steel or stainless steel reaction tube. The reaction tube is preferably kept at a certain temperature by a heat medium such as a molten salt so that the reaction temperature can be adjusted to be constant by removing reaction heat. The reaction conditions for the gas phase oxidation reaction are not particularly limited, and can be carried out under conditions generally used for various reactions. In the case of the reaction, the ortho-xylene-containing gas may be brought into contact with the oxidation catalyst at a temperature of 300 to 400 ° C., preferably 330 to 380 ° C. under normal pressure or pressure.

  The present invention will be described in more detail with reference to examples. The conductivity was measured using a conductivity meter (Castany LAB conductivity meter DS-12, manufactured by HORIBA).

(Example 1)
-Cleaning of carrier (1)-
The weight ratio of silicon carbide, silicon dioxide, and mullite is 90: 5: 5, and the total content of alkali metal elements and alkaline earth metal elements (hereinafter referred to as alkali content) is 0.2% by weight. A ring-shaped carrier having a packing density of 0.88 g / ml, a water absorption rate of 15%, a specific surface area of 0.14 m ² / g, a porosity of 23%, an outer diameter of 6.9 mm, an inner diameter of 3.7 mm, and a length of 7.3 mm. 1) 3 liters was washed by heating at 90 ° C. for 30 minutes using 3 liters of pure water. This washing carrier is referred to as a carrier (1W).

In addition, after taking 300 ml of carrier (1W) into a 500 ml conical beaker and drying at 120 ° C. for 2 hours, 260 ml of pure water (= (300 × 0.88 × 0.15) +220) was added, and the pressure was 90 ° C. under normal pressure. Heated for 30 minutes. The electrical conductivity of the water after separating the carrier was measured, and the specific resistance was determined to be 27,400 Ωcm (25 ° C.).
-Catalyst preparation-
After 80% concentrated sulfuric acid was mixed with ilmenite and reacted sufficiently, it was diluted with water to obtain a titanium sulfate aqueous solution. An iron piece was added thereto as a reducing agent, and the iron content in the ilmenite was reduced to ferrous ions, and then cooled and precipitated and separated as ferrous sulfate. Water vapor heated to 150 ° C. was blown into the titanium sulfate aqueous solution thus obtained to precipitate hydrous titanium oxide. This was washed with water, pickled and washed with secondary water, and then calcined at 800 ° C. for 4 hours under air flow. This was subjected to jet airflow pulverization to obtain anatase type titanium oxide having an average particle size of 0.5 μm and a specific surface area of 22 m ² / g.

  100 g of oxalic acid was dissolved in 3200 ml of deionized water to form an aqueous oxalic acid solution. To this, 23.63 g of ammonium metavanadate, 2.99 g of monobasic ammonium phosphate, 9.40 g of niobium chloride, 4.13 g of cesium sulfate and antimony trioxide 18.35 g was added and stirred well. 900 g of the anatase-type titanium oxide was added to the solution thus obtained, and stirred with an emulsifier to prepare a catalyst slurry liquid.

  1000 ml of carrier (1 W) is placed in a stainless steel rotary furnace having a diameter of 35 cm and a length of 80 cm that can be heated from the outside, preheated to 200 to 250 ° C., and spraying the catalyst slurry liquid onto the carrier while rotating the furnace. Then, the catalytically active substance was supported at a ratio of 9.5 g / 100 ml (support). Thereafter, the catalyst (A) was prepared by calcination at a temperature of 580 ° C. for 6 hours while circulating air.

  In the preparation of the catalyst (A), a catalyst (B) was prepared in the same manner as in the above method except that the addition amount of primary ammonium phosphate was changed to 11.96 g. Table 1 shows the catalyst compositions of the catalyst (A) and the catalyst (B).

-Oxidation reaction-
An iron reaction tube having an inner diameter of 25 mm and a length of 3 m, immersed in a molten salt bath maintained at a temperature of 350 ° C., is first filled with a catalyst (B) at a height of 1 m at the raw material gas outlet as a subsequent catalyst, and then Catalyst (A) was packed at a height of 1.8 m at the inlet portion as a pre-stage catalyst. As a raw material gas, a mixed gas in which ortho-xylene is mixed with air at a ratio of 70 g / Nm ³ (air) is introduced from the upper inlet of the reaction tube at a space velocity (SV) 2910Hr ⁻¹ (STP) to oxidize ortho-xylene. Reaction was performed. The initial stage of the reaction, the phthalic anhydride yield three months after the initial stage of the reaction, and the amount of unreacted byproduct phthalide were measured. The conversion rate of ortho-xylene is almost 100%, and the above yield can be regarded as phthalic acid selectivity.

(Example 2)
In Example 1 (catalyst preparation), catalysts (C) and (D) were prepared in the same manner as in Example 1 (catalyst preparation) except that the following support (2W) was used instead of support (1W). Then, an oxidation reaction was performed in the same manner as in Example 1 (oxidation reaction). The compositions of the catalysts (C) and (D) are shown in Table 1, and the results of the oxidation reaction are shown in Table 2.

-Cleaning of carrier (2)-
Ring-shaped steatite carrier having a packing density of 1.08 g / ml, a water absorption of 3%, a specific surface area of 0.007 m ² / g, a porosity of 5%, an outer diameter of 6.9 mm, an inner diameter of 3.8 mm, and a length of 7.0 mm ( 2) 3 liters were washed by heating at 90 ° C. for 30 minutes using 3 liters of pure water. This washing carrier is referred to as a carrier (2W).

  In addition, after taking 300 ml of carrier (2W) in a 500 ml conical beaker and drying at 120 ° C. for 2 hours, 230 ml of pure water (= (300 × 1.08 × 0.03) +220) was added, and at 90 ° C. under normal pressure. Heated for 30 minutes. When the electrical conductivity of the water after separating the carrier was measured and the specific resistance was determined, it was 44,200 Ωcm (25 ° C.).

(Comparative Example 1)
In Example 1 (catalyst preparation), catalysts (E) and (F) were prepared in the same manner as in Example 1 (catalyst preparation) except that unwashed carrier (1) was used instead of carrier (1W). Thereafter, an oxidation reaction was carried out in the same manner as in Example 1 (oxidation reaction). The compositions of the catalysts (E) and (F) are shown in Table 1, and the results of the oxidation reaction are shown in Table 2.

  In addition, after taking 300 ml of carrier (1) in a 500 ml conical beaker and drying at 120 ° C. for 2 hours, 260 ml of pure water (= (300 × 0.88 × 0.15) +220) was added, and the pressure was 90 ° C. under normal pressure. Heated for 30 minutes. When the electrical conductivity of the water after separating the carrier was measured and the specific resistance was determined, it was 10,500 Ωcm (25 ° C.).

(Comparative Example 2)
In Example 2 (catalyst preparation), catalysts (G) and (H) were prepared in the same manner as in Example 2 (catalyst preparation) except that unwashed carrier (2) was used instead of carrier (2W). Thereafter, an oxidation reaction was carried out in the same manner as in Example 2 (oxidation reaction). The compositions of the catalysts (G) and (H) are shown in Table 1, and the results of the oxidation reaction are shown in Table 2.

  In addition, after taking 300 ml of carrier (2) in a 500 ml conical beaker and drying at 120 ° C. for 2 hours, 230 ml of pure water (= (300 × 1.08 × 0.03) +220) was added, and at 90 ° C. under normal pressure. Heated for 30 minutes. When the electrical conductivity of the water after separating the carrier was measured and the specific resistance was determined, it was 9,500 Ωcm (25 ° C.).

Claims (3)

In the catalyst for gas phase oxidation for producing phthalic anhydride from orthoxylene and / or naphthalene having a catalytically active component supported on an inert carrier, the carrier has a specific resistance of 20,000 Ωcm after the following treatment as the carrier. (25 ° C.) or higher gas phase oxidation catalyst characterized by using:
(Processing method)
After taking 300 ml of the carrier in a 500 ml conical beaker and drying at 120 ° C. for 2 hours, add (water absorption + 220) ml of pure water and heat at 90 ° C. for 30 minutes under normal pressure. Here, the water absorption is expressed by the following formula:
Water absorption = A / B
However, in the formula:
A = 300 (ml) × packing density (g / ml) × water absorption (wt%) / 100
B = density of water (g / ml).   A method for producing phthalic anhydride, characterized in that ortho-xylene and / or naphthalene is vapor-phase oxidized in the presence of the catalyst of claim 1 to produce phthalic anhydride. In a gas phase oxidation catalyst for producing phthalic anhydride from ortho-xylene and / or naphthalene, in which a catalytically active component is supported on an inert carrier, the carrier has a specific resistance of 20 after treatment as follows. A method for preparing a gas-phase oxidation catalyst characterized by using a catalyst that has been washed to 000 Ωcm (25 ° C.) or more:
(Processing method)
After taking 300 ml of the carrier in a 500 ml conical beaker and drying at 120 ° C. for 2 hours, add (water absorption + 220) ml of pure water and heat at 90 ° C. for 30 minutes under normal pressure. Here, the water absorption is expressed by the following formula:
Water absorption = A / B
However, in the formula:
A = 300 (ml) × packing density (g / ml) × water absorption (wt%) / 100
B = density of water (g / ml).