JPH04215843A - Catalyst for manufacturing phthalic anhydride - Google Patents

Abstract

PURPOSE:To provide a catalyst suitable for manufacturing phthalic anhydride which has catalytic performance greatly improved in comparison with conventional catalyst in a catalyst for manufacturing phthalic anhydride by a method wherein o-xylene and/or naphthalene is catalytically oxidized in gaseous state by molecular oxygen or gas containing molecular oxygen. CONSTITUTION:The catalyst is such that a catalytically active substance containing 1-20 pts.wt. vanadium oxide as V2O5, 99-80 pts.wt. anatase-type titanium dioxide having specific surface area of 10-60m<2>/g as TiO2, at least one kind of element, selected from potassium, cerium, rubidium and thallium, of 0.05-1.2 pts.wt. as oxide per 100 pts.wt. of these two components and 0.05-2 pts.wt. silver as Ag2O is carried by heat-resisting inorganic carriers. The catalyst may contain 0-1 pts.wt. niobium as Nb2O5, 0-1.2 pts.wt. phosphorus as P2O5 and 0-5 pts.wt. antimony as Sb2O3 per 100 pts.wt. of vanadium oxide and titanium oxide.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a catalyst for producing phthalic anhydride, and more specifically, the present invention relates to a catalyst for producing phthalic anhydride, and more specifically, it produces phthalic anhydride by catalytically oxidizing ortho-xylene and/or naphthalene with molecular oxygen or a molecular oxygen-containing gas. Concerning catalysts for

0002

[Prior Art] Catalysts for producing phthalic anhydride in which a catalytically active material containing vanadium oxide and titanium oxide as main components are supported on an inert carrier are widely known, for example, Japanese Patent Publication No. 47-15323, Japanese Patent Publication No. 47-15323, It is described in Japanese Patent Publication No. 49-41036, Japanese Patent Publication No. 52-4538, Japanese Patent Application Publication No. 47-5661, and Japanese Patent Application Publication No. 49-89694. Each of these catalysts has its own characteristics, and some have been used industrially with good results.

[0003] However, there is still room for improvement in catalyst performance. First, in terms of selectivity, even a 1% increase in yield has a large economic effect considering the scale of the production equipment. . Furthermore, since an improvement in selectivity facilitates heat treatment and distillation operations before obtaining a product, it can also be expected that a high-quality product can be produced at a low cost due to this improvement in selectivity. In this way, improving selectivity is also important for effectively using raw materials.

[0004] In addition, it is important to ensure stable production by improving productivity and maintaining catalyst activity. One way to improve productivity is to perform the oxidation reaction under high load reaction conditions, such as by increasing the raw material gas concentration. However, the reaction to obtain phthalic anhydride from ortho-xylene or naphthalene is accompanied by significant heat generation, so under high concentration conditions, the temperature rises rapidly at the hot spot, causing an excessive oxidation reaction and reducing the yield of phthalic anhydride. As the temperature decreases, the deterioration of the catalyst is significantly accelerated.

[0005] Catalysts that can withstand use under such high-load reaction conditions are also available, for example, in Japanese Patent Publication No. 59-1 by the applicant of the present patent.
This method has been proposed in Publication No. 378, etc.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a catalyst which has improved catalytic performance compared to conventionally known catalysts and is suitable for the production of phthalic anhydride. Accordingly, one object of the present invention is to provide a catalyst for producing phthalic anhydride that produces phthalic anhydride with high selectivity by gas phase catalytic oxidation of ortho-xylene and/or naphthalene.

Another object of the present invention is to provide a catalyst for producing phthalic anhydride through gas phase catalytic oxidation of ortho-xylene and/or naphthalene, which has excellent durability and does not lose its catalytic activity even after long-term use. It is an object of the present invention to provide a catalyst for producing phthalic anhydride that enables stable production of phthalic anhydride with a small amount of phthalic anhydride. Still another object of the present invention is to enable the production of phthalic anhydride with high selectivity even under high load reaction conditions in the production of phthalic anhydride by gas phase catalytic oxidation of ortho-xylene and/or naphthalene, and An object of the present invention is to provide a catalyst for producing phthalic anhydride that has excellent durability and enables stable production of phthalic anhydride over a long period of time.

[0008]

[Means for Solving the Problems] As a result of extensive research in order to solve the above problems, the inventors have found that the above objects can be achieved by introducing silver as a component of the catalytically active substance into a vanadium-titanium catalyst. We learned that this could be achieved, and based on this knowledge, we completed this invention. That is, the present invention provides a catalyst for producing phthalic anhydride by gas phase catalytic oxidation of ortho-xylene and/or naphthalene with molecular oxygen or molecular oxygen-containing gas. 99 to 80 parts by weight of anatase titanium oxide having a specific surface area of 10 to 60 m2/g as TiO2, and at least 1 part selected from potassium, cesium, rubidium, and thallium per 100 parts by weight of these two components in total.
An anhydrous material comprising a heat-resistant inorganic carrier supporting a catalytically active material containing 0.05 to 1.2 parts by weight of a seed element as an oxide and 0.05 to 2 parts by weight of silver as Ag2O. Catalyst for phthalic acid production (hereinafter referred to as “catalyst”)
catalyst (1)").

Furthermore, the present invention provides a catalyst for producing phthalic anhydride by gas phase catalytic oxidation of ortho-xylene and/or naphthalene with molecular oxygen or molecular oxygen-containing gas. ~20 parts by weight, specific surface area 10~60m2/g
99-8 as anatase type titanium oxide as TiO2
Furthermore, per 100 parts by weight of these two components in total, 0 to 1 part by weight of niobium as Nb2O5 and 0.05 to 1 part of at least one element selected from potassium, cesium, rubidium and thallium as an oxide. 2 parts by weight, 0 to 1.2 parts by weight of phosphorus as P2O5, 0 to 5 parts by weight of antimony as Sb2O3, and 0.05 to 2 parts of silver as Ag2O (however, niobium, phosphorus, and A catalyst for producing phthalic anhydride characterized by supporting a catalytically active substance on a heat-resistant inorganic carrier (the content of each antimony does not become zero at the same time) (hereinafter, this catalyst will be referred to as "catalyst (2)"). ”).

The present invention will be explained in more detail below. One of the features of this invention is that as a component of the catalytically active substance, the specific surface area is 10 to 60 m2/g, preferably 15 to 60 m2/g.
40 m2/g of anatase titanium oxide is used. The specific surface area of this anatase-type titanium oxide is 1
If it is less than 0 m2/g, the activity of the catalyst obtained will be low, while if it exceeds 60 m2/g, the durability of the catalyst will deteriorate and the yield will decrease in a short period of time, which is not preferable.

[0011] In the present invention, among the above-mentioned anatase type titanium oxides, an average particle size of 0.4 to 0.7 μm is used.
, preferably 0.45 to 0.60 μm, and substantially spherical ones are particularly preferably used. The anatase-type titanium oxide that is particularly preferably used in this invention is produced by a method known as the "solution method," and although it is porous, it has high mechanical strength and cannot be crushed by mechanical grinding such as a normal ball mill. It has enough strength to be considered a "primary particle". However, although this anatase-type titanium oxide has a large average particle size in the range of 0.4 to 0.7 μm, it has a high specific surface area of 10 to 60 m2/g, and essentially has a small diameter. It is an aggregate of primary particles with Therefore, this anatase-type titanium oxide does not need to be a perfect sphere, but only needs to be substantially spherical.

According to the above solution method, ilmenite (Fe
OTiO2) is treated with sulfuric acid, which has a lower concentration than that used in the production of titanium oxide by the solidification method, usually about 70 to 80% sulfuric acid, to obtain titanium sulfate.
Hydrolysis under pressure at °C and further at 600-900 °C
Anatase type titanium oxide can be obtained by firing with. Note that this anatase-type titanium oxide may contain iron, zinc, aluminum, manganese, chromium, calcium, lead, etc. due to the relationship with the raw material ore; If it is less than % by weight, there will be no particular problem in terms of catalyst performance.

[0013] The heat-resistant inorganic carrier used in this invention is
It must be stable for a long time at a temperature sufficiently higher than the firing temperature of the catalyst and the catalyst temperature during the production of phthalic anhydride, and must not react with the catalytically active substance. An example of such a heat-resistant inorganic carrier is silicon carbide (Si
C), alumina, zirconium oxide, titanium oxide, etc. can be used. Among these, alumina (
A silicon carbide carrier having an Al2O3) content of 20% by weight or less, preferably 5% by weight or less, and an apparent porosity of 10% or more, preferably 15 to 45% or more is suitably used. In particular, the alumina content is 5% by weight or less,
A silicon carbide carrier having a silicon carbide content of 95% by weight or more and an apparent porosity of 15 to 45% is preferably used. More preferably, purity is 98%.
Examples include silicon carbide carriers obtained by self-sintering the above silicon carbide powders.

Regarding the shape of the heat-resistant inorganic carrier,
Although there are no particular limitations, spherical or cylindrical shapes are suitable for handling, and those with an average diameter of about 2 to 15 mm are preferably used. The catalyst (1) of the present invention includes 1 to 20 parts by weight of vanadium oxide as V2O5 and anatase type titanium oxide as TiO2 on the heat-resistant inorganic carrier.
99 to 80 parts by weight, and a total of 1 of these two components.
Catalytic activity containing 0.05 to 1.2 parts by weight of at least one element selected from potassium, cesium, rubidium and thallium as an oxide and 0.05 to 2 parts by weight of silver as Ag2O per 00 parts by weight. Obtained by supporting components.

One feature of this invention is that, as mentioned above, silver is introduced as a component of the catalytically active material, and the silver content in the catalyst (1) is 0.0 as Ag2O.
The amount is 5 to 2 parts by weight, preferably 0.1 to 1 part by weight. If the silver content is too high or too low, the object of this invention cannot be achieved. In other words, the amount of silver added is A
If g2O is less than 0.05 parts by weight, the effect of improving performance by adding silver will be low. Also, the amount of silver added is 2
Exceeding the weight part adversely affects the performance of the catalyst and lowers the selectivity to phthalic anhydride.

The catalyst (2) of the present invention is a heat-resistant inorganic carrier containing 1 to 20 parts by weight of vanadium oxide as V2O5 and 99% of anatase-type titanium oxide as TiO2.
~80 parts by weight, and further 0 to 1 part by weight of niobium as Nb2O5 and 0.05 to 1 part of oxide of at least one element selected from potassium, cesium, rubidium, and thallium per 100 parts by weight of these two components in total. ．．
2 parts by weight, 0 to 1.2 parts by weight of phosphorus as P2O5, 0 to 5 parts by weight of antimony as Sb2O3, and 0.05 to 2 parts by weight of silver as Ag2O (However, niobium, phosphorus, and antimony (the contents of each of which do not become zero at the same time) can be obtained by supporting a catalytically active substance.

Similar to catalyst (1), this catalyst (2) also has a silver content of 0.05 to 2 parts by weight as Ag2O, preferably 0.1 to 1 part by weight. If the silver content is too high or too low, the object of this invention cannot be achieved. In addition, in the catalyst (2), niobium is replaced with N
0.01 to 1 part by weight as b2 O5, P2 as phosphorus
A catalyst formed by supporting a catalytically active material containing 0.2 to 1.2 parts by weight as O5 and 0.5 to 5 parts by weight as antimony as Sb2O3 on a heat-resistant inorganic carrier,
It is particularly preferred since it improves the selectivity of phthalic anhydride.

In preparing the catalyst (1) and the catalyst (2), the starting materials for each component of vanadium, niobium, potassium, cesium, rubidium, thallium, phosphorus and antimony include V2 O5, Nb2 O5, K2
O, Cs2O, Rb2O, Tl2O, P2O5
In addition to oxides such as , Sb2O3, etc., compounds that change into the above oxides by heating, such as ammonium salts, nitrates, sulfates, halides, organic acid salts, and hydroxides of each element, may be selected as appropriate. I can do it.

Regarding the silver component, in addition to Ag2O, nitrates, ammonium salts, sulfates, halides, organic acid salts, hydroxides, amine complexes, phosphates, sulfides, etc. can be used. Note that some of these, such as silver halide and silver phosphate, do not become oxides under the heating conditions during catalyst preparation, but they can be used without any problem in the present invention. In addition, when using silver phosphate and adding a phosphorus component as a catalytically active substance, there is no need to consider the amount of phosphorus in this silver phosphate, and the amount of phosphorus component as an oxide is Just make sure it's within the range.

[0020] When preparing the catalyst of the present invention, there is no particular restriction on the method of supporting the above-mentioned catalytically active substance on the heat-resistant inorganic carrier, and it can be supported by any commonly used method. In particular, a certain amount of carrier is placed in a rotating drum that can be heated from the outside, and the carrier is heated to 200 to 300
The simplest method is to spray a slurry containing a catalytically active substance while maintaining the temperature at °C to support the catalytically active substance.

[0021] The amount of the catalytically active substance supported on the heat-resistant inorganic carrier varies depending on the size of the carrier used, but is usually preferably 3 to 20 g per 100 cc of carrier. The catalytically active material layer obtained by supporting the catalytically active material on the above carrier has a total pore volume occupied by pores having a diameter of 0.15 to 0.45 μm, and a total pore volume occupied by pores having a diameter of 10 μm or less. It is preferred to have surface properties such that 50% or more of the pore volume, especially 0.15 to 0.45
The total pore volume occupied by pores with a diameter of μm is 10μ
75% of the total pore volume occupied by pores with a diameter of m or less
It is preferable to have surface characteristics that account for the above.

By providing a catalytically active layer having such surface characteristics, the objects of the present invention can be achieved more effectively. A catalytically active material layer having the above-mentioned surface characteristics can be easily obtained by adjusting the slurry concentration according to the particle size of the essential primary particles of anatase-type titanium oxide, for example, in the supporting method using the aforementioned rotating drum. (Special Publication No. 49-4103)
(See Publication No. 6). Specifically, the particle size of the primary particles is 0.0
When using anatase titanium oxide having a diameter of 0.05 to 0.05 μm, the slurry concentration should be 5 to 25% by weight, preferably 10 to 20% by weight, and the particle size of the primary particles should be 0.05% by weight.
When using anatase titanium oxide larger than μm, the slurry concentration should be 10 to 40% by weight, preferably 1
By adjusting the amount to 5 to 25% by weight, a catalytically active material layer having the above surface characteristics can be formed.

In the present invention, the pore volume was determined from the pore size distribution measured by a mercury intrusion porosimeter. The specific surface area of anatase titanium was measured by the BET method, and the average diameter was measured using a transmission electron microscope. After supporting the catalytically active material layer as described above, 450 ~
at a temperature of 700°C, preferably 500-600°C,
The catalyst of the present invention is obtained by calcination for about 2 to 10 hours under air circulation.

The oxidation reaction of ortho-xylene and/or naphthalene using the catalyst of the present invention can be carried out under conventional reaction conditions. For example, the inner diameter is 5 to 40 m.
1 to 5 m of catalyst in a reaction tube, preferably 15 to 27 mm.
m, preferably 1.5 to 3 m high, and the reaction tube is heated to 300 to 400°C, preferably 3 m by a heating medium.
The temperature was maintained at 30 to 380°C, and the raw material ortho-xylene and/or naphthalene was added to the reaction tube together with air or a gas containing 5 to 21% by volume of molecular oxygen.
In the case of air, the rate is 5 to 70 g/Nm3 (air), and in the case of molecular oxygen-containing gas, it is 5 to 110 g/Nm3 (molecular oxygen-containing gas), and the space velocity is 1000 to 600.
0hr-1 (STP), preferably 1000-4000
Introduced at hr-1 (STP).

In the above oxidation reaction, the catalyst layer in the reaction tube is divided into two or more layers to provide a plurality of reaction zones, and a plurality of catalysts with controlled catalytic activities are introduced into these reaction zones as raw material gas into the reaction tube. The catalyst of the present invention can be used advantageously by arranging the catalyst so that the activity increases from the inlet to the outlet. To specifically explain the catalyst (2) of the present invention as an example, first, the reaction tube is divided into two layers, and a predetermined catalyst (previous stage The remaining bed height at the outlet is filled with a catalyst (second stage catalyst) whose activity is higher than that of the first stage catalyst. Catalysts with the same catalyst composition but different activities can be easily prepared, for example, by varying the content of the phosphorus component. Specifically, the phosphorus component is 0.0% as an oxide.
By using 2 to 0.4 parts by weight, it is possible to prepare a first stage catalyst, and by using 0.4 to 1.2 parts by weight, a second stage catalyst can be prepared which has higher activity than the first stage catalyst. Further, the catalytic activity can also be controlled by changing the type and/or amount of the element selected from potassium, cesium, rubidium, and thallium.

By carrying out the oxidation reaction under the above conditions, heat accumulation in hot spots within the catalyst layer is suppressed, thereby preventing deterioration of the catalyst due to heat load, and ensuring stable operation for a long period of time industrially. It can be implemented. In addition, excessive oxidation reactions at hot spots are prevented, resulting in various effects such as improved selectivity. Such an effect is remarkable under high-load reaction conditions such as increasing the raw material gas concentration, and productivity can be significantly improved by increasing the ortho-xylene or naphthalene concentration.

[0027]

Effects of the Invention By using the catalyst of the present invention, phthalic anhydride can be produced from ortho-xylene and/or naphthalene with high selectivity. Therefore, heat treatment and distillation operations to obtain a phthalic anhydride product are facilitated, and a high-quality product can be obtained at a lower cost than with conventional methods.

The catalyst of the present invention has excellent durability and can therefore be operated stably for a long period of time industrially. The catalyst of the present invention produces phthalic anhydride with high selectivity even under high load reaction conditions such as increasing the raw material gas concentration, and has excellent durability even after long-term use. The use of catalysts significantly increases the productivity of phthalic anhydride production.

Therefore, it can be said that the catalyst of the present invention is an extremely useful catalyst for the production of phthalic anhydride.

[0030]

[Examples] The present invention will be explained in more detail below with reference to Examples. -Example 1- (Preparation of catalyst) Ilmenite was mixed with 80% concentrated sulfuric acid, and after sufficiently reacting, the mixture was diluted with water to obtain an aqueous titanium sulfate solution. Iron pieces were added as a reducing agent to reduce the iron in the ilmenite to ferrous ions, which were then cooled and separated as ferrous sulfate. Steam heated to 150°C was blown into the aqueous titanium sulfate solution thus obtained to precipitate hydrous titanium oxide. After washing with water, pickling and secondary water washing, this was baked at a temperature of 800°C for 4 hours under air circulation. This was subjected to jet air flow pulverization treatment, and the average particle size was approximately 0.5μ.
Anatase type titanium oxide (hereinafter sometimes simply referred to as "titanium oxide") with a specific surface area of 22 m2/g was obtained.

[0031] 200 g of oxalic acid was dissolved in 6400 cc of deionized water to obtain an oxalic acid aqueous solution, and to this was added 47.25 g of ammonium metavanadate and 5.98 g of monoammonium phosphate.
g, niobium chloride 18.79g, cesium sulfate 5.90g
, 5.39 g of silver nitrate and 36.73 g of antimony trioxide.
g and stirred thoroughly. 1,800 g of titanium oxide was added to the solution thus obtained and stirred using an emulsifier to prepare a catalyst slurry.

[0032] Diameter 35cm, length 8 that can be heated from the outside.
A sphere with a diameter of 6 mm is placed in a stainless steel rotary furnace with a diameter of 0 cm.
Put 2000 cc of SiC self-sintering carrier with an apparent porosity of 35%, preheat it to 200 to 250°C, and spray the above catalyst slurry onto the carrier while rotating the furnace to add 8 g/100 cc of the catalytic active material. (carrier). After that, it is heated at 580° in an electric furnace while circulating air.
The catalyst (A) was prepared by firing at a temperature of C for 6 hours.

The composition of the catalyst (A) and the ratio of the total pore volume occupied by pores with a diameter of 0.15 to 0.45 μm to the total pore volume occupied by pores with a diameter of 10 μm or less in the catalytically active material layer ( Table 1 shows the average particle diameter and specific surface area (hereinafter collectively referred to as "catalyst properties") of the titanium oxide used in the preparation of the catalyst. The ratio of the volume occupied by pores having a diameter of 0.15 to 0.45 μm to the total pore volume was determined from the results of measuring pore distribution using a mercury intrusion porosimeter.

Catalyst (B) was prepared in the same manner as above, except that the amount of monoammonium phosphate added in the preparation of catalyst (A) was changed to 23.92 g. Table 1 shows the catalytic properties of catalyst (B). Note that the phosphorus component content in the catalyst (B) is higher than that in the catalyst (A), and the activity of the catalyst (B) is higher than that of the catalyst (A). (Oxidation reaction) I.D. 2 immersed in a molten salt bath maintained at a temperature of 355°C.
A 5 mm, 3 m long iron reaction tube was first filled with the catalyst (B) as a rear stage catalyst at a height of 1 m at the raw material gas outlet, and then with the catalyst (A) as a front stage catalyst at a height of 1.5 m at the inlet. I filled it up.

A mixed gas of 85 g/Nm3 (synthesis gas) of ortho-xylene was mixed with a synthesis gas consisting of 10% by volume of oxygen, 10% by volume of water vapor, and 80% by volume of nitrogen, and was introduced into the space from the upper inlet of the reaction tube. Speed (SV)2
The oxidation reaction of ortho-xylene was carried out by introducing at 500 hr-1 (STP). In the early stage of the reaction, 3 months after the start of the reaction,
Measure the yield of phthalic anhydride 6 months after the start of the reaction,
The results are shown in Table 2. Note that the conversion rate of ortho-xylene was approximately 100%, and the above yield can be considered as the selectivity of phthalic anhydride.

-Example 2- In Example 1 (preparation of catalyst), Example 1 (preparation of catalyst) was performed except that 4.94 g of silver sulfate was used instead of 5.39 g of silver nitrate.
Catalysts (C) and (D) were prepared in the same manner as in Example 1 (Preparation of Catalyst), and an oxidation reaction was carried out in the same manner as in Example 1 (oxidation reaction). Table 1 shows the catalyst properties of catalysts (C) and (D), and Table 2 shows the results of the oxidation reaction.

-Example 3- Example 1 except that in Example 1 (preparation of catalyst), 4.42 g of silver phosphate was used instead of 5.39 g of silver nitrate.
Catalysts (E) and (F) were prepared in the same manner as in (Preparation of catalyst), and an oxidation reaction was carried out in the same manner as in Example 1 (oxidation reaction). The catalytic properties of catalysts (E) and (F) are shown in Table 1, and the results of the oxidation reaction are shown in Table 2.

- Comparative Example 1 - In Example 1 (preparation of catalyst), the same procedure as in Example 1 (preparation of catalyst) was carried out except that the amount of cesium sulfate added was 8.25 g and silver was not added. Catalyst (K), (L)
was prepared, and an oxidation reaction was performed in the same manner as in Example 1 (oxidation reaction). Table 1 shows the catalyst properties of catalysts (K) and (L), and Table 2 shows the results of the oxidation reaction.

-Example 4- (Preparation of catalyst) Ilmenite was mixed with 80% concentrated sulfuric acid, and after sufficiently reacting, it was diluted with water to obtain an aqueous titanium sulfate solution. Iron pieces were added as a reducing agent to reduce the iron in the ilmenite to ferrous ions, which were then cooled and separated as ferrous sulfate. Steam heated to 150°C was blown into the aqueous titanium sulfate solution thus obtained to precipitate hydrous titanium oxide. After washing with water, pickling and secondary water washing, this was baked at a temperature of 700°C for 4 hours under air circulation. This was subjected to jet stream pulverization treatment, and the average particle size was approximately 0.4.
Anatase type titanium oxide with a specific surface area of 33 m2/g measured by BET method at 5 μm was obtained.

Dissolve 900 g of oxalic acid in 6400 cc of deionized water to make an oxalic acid aqueous solution, and add 408.60 g of ammonium metavanadate, 10.34 g of monoammonium phosphate, 17.33 g of niobium chloride, 2.72 g of cesium sulfate, and sulfuric acid to this aqueous solution. Potassium 3.92g, silver nitrate 31.
05g and 42.35g of antimony trioxide,
Stir thoroughly. 1800 g of the above titanium oxide was added to the solution thus obtained and stirred using an emulsifier to prepare a catalyst slurry.

[0041] Using the above slurry, a catalytically active substance was supported in the same manner as in Example 1. The loading rate is 8.0g/10
It was 0 cc (carrier). Thereafter, the catalyst (G
) was prepared. Catalyst (H) was prepared in the same manner as in the preparation of catalyst (G) except that the amount of monoammonium phosphate used was 31.02 g. (Oxidation reaction) 25 mm inner diameter immersed in a molten salt bath maintained at 365°C
, a catalyst (H
) was packed to a height of 1 m, and then a catalyst (
G) was filled to a height of 1.5 m, and naphthalene was added from the top of the reaction tube to 10% by volume of oxygen, 10% by volume of steam, and 8% of nitrogen.
85 g/Nm3 (
Synthetic gas) mixed gas at a space velocity of 2500h
It was introduced at r-1 (STP) and an oxidation reaction was performed.

The catalyst properties of catalysts (G) and (H) are shown in Table 1.
The results of the oxidation reaction are shown in Table 2. - Comparative Example 2 - In Example 4 (preparation of catalyst), the amount of potassium sulfate added was 1.96 g, and the amount of silver nitrate added was 77.63 g.
Catalysts (M) and (N) were prepared in the same manner as in the preparation of catalysts (G) and (H), except that g was used, and the reaction was carried out in the same manner as in Example 4 (oxidation reaction).

The catalyst properties of catalysts (M) and (N) are shown in Table 1.
The results of the oxidation reaction are shown in Table 2. - Example 5 - (Preparation of catalyst) An oxalic acid aqueous solution was prepared by dissolving 200 g of oxalic acid in 6400 cc of deionized water, and to this aqueous solution, 96.48 g of ammonium metavanadate, 4.82 g of cesium sulfate, 1.18 g of thallium nitrate, and silver nitrate were added. 2.75 g was added and thoroughly stirred. The same anatase-type titanium used in Example 1 was added to the solution obtained in this manner as TiO2.
800 g was added and stirred using an emulsifier to obtain a slurry.

[0044] Using the above slurry, a catalytically active substance was supported in the same manner as in Example 1. The supported amount is 8.0g/
It was 100cc (carrier). Thereafter, the mixture was calcined in an electric furnace at a temperature of 550° C. for 6 hours while circulating air to prepare catalyst (I) (first stage catalyst). Catalyst (I) except that 2.96 g of rubidium nitrate was used instead of cesium sulfate and thallium nitrate in the preparation of catalyst (I) above.
Catalyst (J) (second stage catalyst) was prepared in the same manner as in the preparation of. (Oxidation reaction) In Example 1, a mixed gas in which ortho-xylene was mixed at a ratio of 70 g/Nm3 (synthesis gas) to a synthesis gas consisting of 21% by volume of oxygen and 79% by volume of nitrogen was used as the raw material gas, An oxidation reaction was carried out in the same manner as in Example 1 except that this was introduced from the upper inlet of the reaction tube at a space velocity of 3000 hr-1 (STP).

The catalyst properties of catalysts (I) and (J) are shown in Table 1.
The results of the oxidation reaction are shown in Table 2. - Example 6 - In the preparation of catalyst (I) in Example 5 (preparation of catalyst), catalyst (I) was prepared except that 19.06 g of niobium chloride was added.
Catalyst (Q) was prepared in the same manner as in the preparation of ). In addition, in preparing the catalyst (J), the amount of rubidium nitrate added was
．． Catalyst (R) was prepared in the same manner as in the preparation of catalyst (J) except that 6.08 g of primary ammonium phosphate was added.

An oxidation reaction was carried out in the same manner as in Example 5 (oxidation reaction). Table 1 shows the catalyst characteristics of catalysts (Q) and (R).
Table 2 shows the results of the oxidation reaction. - Example 7 - In Example 5 (preparation of catalyst), antimony trioxide 1
Catalysts (S) and (T) were prepared in the same manner as in Example 5 (preparation of catalyst) except that 8.75 g was added.
The oxidation reaction was carried out in the same manner as in (oxidation reaction).

The catalyst characteristics of catalysts (S) and (T) are shown in Table 1.
The results of the oxidation reaction are shown in Table 2. - Example 8 - In the preparation of catalyst (I) in Example 5 (preparation of catalyst), the amount of cesium sulfate added was 6.02 g, 19.06 g of niobium chloride and 6.08 g of primary ammonium phosphate.
Catalyst (I) was prepared in the same manner as in the preparation of catalyst (I) except that g was added.
U) Prepared.

In the preparation of catalyst (J), the same procedure as that of catalyst (J) was carried out except that the amount of rubidium nitrate added was 4.44 g, and 6.08 g of primary ammonium phosphate and 18.75 g of antimony trioxide were added. Similarly, the catalyst (V)
was prepared. Thereafter, an oxidation reaction was carried out in the same manner as in Example 5 (oxidation reaction). Table 1 shows the catalyst properties of catalysts (U) and (V).
Table 2 shows the results of the oxidation reaction.

-Example 9- The preparation of catalyst (I) in Example 5 (preparation of catalyst) was the same as the preparation of catalyst (I) except that 19.06 g of niobium chloride and 18.75 g of antimony trioxide were added. A catalyst (W) was prepared. In addition, in the preparation of catalyst (J), the amount of rubidium nitrate added was 4.44 g, niobium chloride was 19.06 g, and primary ammonium phosphate was 6.08 g.
A catalyst (X) was prepared in the same manner as the preparation of the catalyst (J) except that 18.75 g of antimony trioxide was added.

An oxidation reaction was carried out in the same manner as in Example 5 (oxidation reaction). Table 1 shows the catalyst properties of catalysts (W) and (X).
Table 2 shows the results of the oxidation reaction. - Comparative Example 3 - In the preparation of catalyst (I) in Example 5 (preparation of catalyst), the same as the preparation of catalyst (I) except that the amount of cesium sulfate added was 6.03 g and silver nitrate was not added. A catalyst (O) (first stage catalyst) was prepared.

In addition, in preparing the catalyst (O), the catalyst (O) was prepared in the same manner as in the preparation of the catalyst (O), except that the amount of rubidium nitrate added was 4.44 g, and silver nitrate was not added.
P) (second stage catalyst) was prepared. Thereafter, an oxidation reaction was carried out in the same manner as in Example 5. Table 1 shows the catalyst properties of catalysts (O) and (P), and Table 2 shows the results of the oxidation reaction.

In the above Examples and Comparative Examples, the oxidation reaction is continued with a constant load on the catalyst, and during this time, in the case of the oxidation reaction of ortho-xylene, the amount of by-produced phthalide is controlled to 0.1% by weight or less. The molten salt temperature was set as follows, and in the case of the naphthalene oxidation reaction, the molten salt temperature was set so as to control the amount of by-produced naphthoquinone to 0.5% by weight or less.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

From the comparison between Examples 1 to 3 and Comparative Example 1, and the comparison between Examples 5 to 9 and Comparative Example 3, it is clear that the yield of phthalic anhydride is improved by adding silver. A comparison between Example 4 and Comparative Example 2 shows that there is a limit to the amount of silver added. As shown in Tables 1 and 2,
The catalyst to which silver is added according to the present invention has an approximately 2% improvement in the yield of phthalic anhydride compared to the catalyst without silver.
Furthermore, the performance after 3 and 6 months is also very stable, and great economic effects can be expected. For example, if we currently produce 40,000 tons of phthalic anhydride per year, a 2% increase in yield would allow us to obtain 400 tons of phthalic anhydride without increasing raw material consumption. It is.

Claims (3)

[Claims] Claim 1. A catalyst for producing phthalic anhydride by vapor phase catalytic oxidation of orthoxylene and/or naphthalene with molecular oxygen or a molecular oxygen-containing gas, comprising 1 to 20 parts by weight of vanadium oxide as V2O5. 99 to 80 parts by weight of anatase titanium oxide having a specific surface area of 10 to 60 m2/g as TiO2, and further oxidizing at least one element selected from potassium, cesium, rubidium, and thallium per 100 parts by weight of these two components in total. A catalyst for producing phthalic anhydride, characterized in that a catalytically active material containing 0.05 to 1.2 parts by weight as Ag2O and 0.05 to 2 parts by weight of silver as Ag2O is supported on a heat-resistant inorganic carrier. . 2. A catalyst for producing phthalic anhydride by vapor phase catalytic oxidation of orthoxylene and/or naphthalene with molecular oxygen or a molecular oxygen-containing gas, comprising 1 to 20 parts by weight of vanadium oxide as V2O5. , anatase type titanium oxide with a specific surface area of 10 to 60 m2/g as TiO2, and 99 to 80 parts by weight of TiO2, and niobium as Nb2 per 100 parts by weight of these two components in total.
0 to 1 part by weight as O5, 0.05 to 1.2 parts by weight as an oxide of at least one element selected from potassium, cesium, rubidium, and thallium, and P2 as phosphorus.
0 to 1.2 parts by weight as O5, antimony as Sb2
A catalytically active material containing 0 to 5 parts by weight as O3 and 0.05 to 2 parts by weight as Ag2O (however, the content of each of niobium, phosphorus, and antimony will not be 0 at the same time). A catalyst for producing phthalic anhydride characterized by being supported on a heat-resistant inorganic carrier. 3. In a catalytically active material layer supported on a heat-resistant inorganic support, the total pore volume occupied by pores with a diameter of 0.15 to 0.45 μm is the total pore volume occupied by pores with a diameter of 10 μm or less. The catalyst for producing phthalic anhydride according to claim 1 or 2, wherein the pore volume is 50% or more.