JPS637536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pyromellitic acid or its anhydride by catalytic gas phase oxidation of 1,2,4,5-tetramethylbenzene (hereinafter referred to as diurene) with a molecular oxygen-containing gas. Specifically, the present invention relates to vanadium (V),
It is characterized by catalytic gas phase oxidation of diurene using a catalyst in which a catalytic material containing oxides of titanium (Ti), phosphorus (P), niobium (Nb) and antimony (Sb) is supported on an inert carrier. The present invention relates to a method for producing pyromellitic acid or its anhydride. Pyromellitic anhydride has been widely used in heat-resistant resins, plasticizers, and epoxy resin curing agents, and its importance as an industrial raw material has been increasing in recent years. In addition to the catalytic gas phase oxidation method of Diurene, the manufacturing method also includes the liquid phase oxidation method of Diurene, 2,
A liquid phase oxidation method for 4,5-trimethylbenzaldehyde and a synthesis method from other starting materials other than diurene have also been proposed. Among these methods, the gas phase oxidation method for pyromellitic anhydride has promoted the decline in the market price of pyromellitic anhydride, and the demand for pyromellitic anhydride has increased due to the possibility that the raw material dyurene, which was traditionally expensive, can be obtained in large quantities and at low cost through the use of zeolite catalysts. It is attracting attention as a process that can cause expansion. Numerous patent documents have been published regarding catalysts for catalytic gas phase oxidation of diurene, such as V ₂ O ₅
−TiO ₂ , WO ₃ system (Belgium patent no. 655686),
V ₂ O ₅ −P ₂ O ₅ −TiO ₂ , MoO ₃ , WO ₃ series (Special public interest
−4978), V ₂ O ₅ −TiO ₂ (anatase type) −
MoO ₃ , P ₂ O ₅ series (Special Publication No. 45-15018), V ₂ O ₅ −
TiO ₂ −Na ₂ O, P ₂ O ₅ system (Special Publication No. 15252 of 1972),
V ₂ O ₅ −TiO ₂ −P ₂ O ₅ −Nb ₂ O ₅ −K ₂ O, Cs ₂ O system (Special Publication No. 1972-31972), V ₂ O ₅ −B ₂ O ₃ −SnO ₂ , P _{2 O5} ,
TiO ₂ , Na ₂ O type (Japanese Patent Publication No. 49-31973), etc. have been disclosed. However, in cases using these catalysts, the concentration of diurene in the raw gas composition is 20
The concentration is as low as g/Nm ³ -air or less, and the desired pyromellitic acid or its anhydride cannot be obtained in good yield, so it is not necessarily industrially satisfactory. The present inventors have conducted extensive research on a method for _producing pyromellitic acid or its anhydride by catalytic gas-phase oxidation of diurene, particularly on _{V 2 O 5} -TiO ₂ -based catalysts _. By using a multi-component oxide-supported catalyst in which a catalyst material combining Sb ₂ O ₃ with a catalyst system of Nb ₂ O ₅ -P ₂ O ₅ is supported on a carrier, extremely high yields of pyromellitic anhydride can be achieved even under high raw material loading conditions. It was discovered that the ratio (calculated as the sum of pyromellitic acid and its anhydride) could be stably obtained.
This invention has been completed. The present invention will be explained in more detail below. The catalyst material of the catalyst in the present invention mainly contains 1 to 80 parts by weight of V ₂ O ₅ and 99 to 20 parts by weight of TiO ₂ ,
For a total of 100 parts of both components, Nb ₂ O ₅ 0.01~
5 parts by weight, P ₂ O ₅ 0.02 to 10 parts by weight, and further Sb ₂ O ₃ 0,
It contains 1 to 30 parts by weight. In addition, in addition to the above composition ratio, Na ₂ O, K ₂ O,
A total of 0.01 to 5 parts by weight of one or more of Rb ₂ O, Cs ₂ O, CaO, SrO, BaO, or a total of 0.01 of one or more of rare earth element oxides, ZnO, Tl ₂ O
It may contain up to 3 parts by weight. The rare earth elements referred to here are elements with atomic numbers 39 and 57 to 71,
Particularly preferred are yttrium, lanthanum, cerium, neodymium, gadolinium, terbium, and erbium. In addition, the oxides of each element as the catalyst material used here, that is, V ₂ O ₅ ,
_Nb2O5 , _{P2O5 , Sb2O3 , Na2O , K2O} , _Rb2O ,
_Cs2O , CaO, SrO, BaO, rare earth oxides, ZnO,
Sources of Tl ₂ O include oxides of these elements,
It can be appropriately selected from ammonium salts, sulfates, nitrates, organic acid salts, carbonates, chlorides, hydroxides, free acids, and the like. Furthermore, the catalyst material components shown in the text are not necessarily limited to the oxide forms described in the text, but are merely used to indicate their compositions. TiO ₂ effective in the catalyst material of the present invention
There are various methods for producing TiO 2 , such as high-purity TiO ₂ obtained by synthesizing titanium ammonium sulfate using titanium tetrachloride as a raw material and thermally decomposing it, or TiO ₂ obtained by heat treating titanium hydroxide produced by hydrolyzing titanyl sulfate. Although TiO ₂ , which is generally commercially available for use as a pigment, can be used satisfactorily by performing appropriate treatment to control the removal of harmful impurities. TiO ₂ exists in two types of crystal forms: anatase type and rutile type, and the anatase type is useful for the catalyst of the present invention. In addition, in the case of high-purity TiO ₂ made from titanium tetrachloride, a mixture of rutile-type TiO ₂ can also be used, but commercially available rutile-type TiO 2 for pigments can be used.
TiO ₂ is already specially treated TiO ₂ ,
Even when used in the present invention, excellent effects cannot be expected. The above-mentioned catalyst substance can be used as a molded catalyst by itself or in combination with a molding aid, but is preferably supported on an inert carrier. As the inert carrier, commonly known carriers such as silica, alumina, silicate, silicon carbide, anti-flinder, pumice, etc. are used. Preferred carriers are, for example, aluminum containing 10% or less as Al ₂ O ₃ and silicon carbide content of 10% or less. Silicon carbide-based carriers with a porosity of 50% or more and an apparent porosity of 10% or more give good results. The method for preparing the catalyst in the present invention involves dispersing TiO ₂ powder into a slurry in an aqueous solution containing vanadium, niobium, phosphorus, antimony, and other component elements, a nitric acid aqueous solution, an oxalic acid aqueous solution, or a hydrochloric acid aqueous solution. is sprayed onto a preheated carrier using a sprayer or the like, and then heated at 300 to 650°C, preferably 400 to 550°C, for several hours under a stream of air or under a blanket of air or under a stream of an inert gas such as nitrogen. A method of firing is preferred. In this case, the loading rate of the catalyst substance on the carrier varies depending on the specific gravity, shape, particle size, etc. of the carrier used, but for example, when using a spherical silicon carbide carrier with a diameter of 3 to 10 mm, the catalyst substance is supported per 100 c.c. of the carrier. 3-15
carry g. When the supported catalyst obtained as described above is used in the production method of the present invention, it is particularly useful that the catalyst material has the following physical properties. In other words, the total volume of pores with an average pore diameter in the range of 0.05 to 0.45μ is 50% of the total volume of pores with a pore diameter of 10μ or less.
The pores are distributed at a ratio that shows the above. In general, the average pore diameter and pore volume distribution are influenced by catalyst preparation conditions such as catalyst composition and calcination conditions, but the catalyst in the present invention is particularly characterized by the presence of TiO ₂ powder in the catalyst slurry and other catalysts. Affected by the degree of dispersion with the substance and the slurry concentration. That is, when the slurry has a high degree of dispersion and a high concentration, the average pore diameter and pore volume also tend to increase.
Taking these points into consideration, the catalyst material having the above-mentioned pore distribution is prepared by appropriately determining the catalyst composition, the degree of dispersion and concentration of the catalyst slurry, and the firing conditions. The reaction conditions for catalytic gas phase oxidation of diurene using the catalyst obtained as described above include a reaction temperature of 350 to 450°C, preferably 360 to 430°C, and a space velocity of 3000 to 15000 hr ^-1 (STP), preferably is 4000～
10000hr ^-1 (STP), raw material concentration 10-50g/
Nm ³ -conducting gas, preferably 20 to 40 g/Nm ³ -conducting gas. Air or a molecular oxygen-containing gas is used as the conduction gas, with air being preferred. Moreover, water vapor can also be entrained in the raw material gas. Thus pyromellitic anhydride is 110-115
It is obtained in a high yield of % by weight. That is, by using the catalyst of the present invention, an extremely high yield of pyromellitic anhydride can be obtained even under high raw material loading conditions. Next, examples of the present invention will be shown and explained in more detail. Example 1 5700g of reagent grade TiCl ₄ was gradually dropped into water.
A 60% aqueous solution was prepared, and 2940 g of reagent grade sulfuric acid was added to this TiCl ₄ aqueous solution with stirring. On the other hand, prepare a saturated aqueous solution containing 3940 g of special grade ammonium sulfate heated to 100°C, and add this saturated aqueous solution to the TiCl ₄ −
Add to H ₂ SO ₄ aqueous solution with stirring and leave to stand.
Titanium ammonium sulfate [(NH ₄ ) ₂ SO ₄・
TiOSO ₄ H ₂ O] was precipitated. This was separated separately and then calcined at 750°C for 10 hours to obtain 2300g of TiO ₂ . Dissolve 514 g of oxalic acid in 6400 c.c. of deionized water to make an oxalic acid solution, and add 257 g of ammonium vanadate,
16.2g ammonium monophosphate and niobium chloride
Hydrochloric acid aqueous solution containing 12.2g and antimony trioxide 120
1800 g of the above TiO ₂ to the prepared solution obtained by adding
was added and stirred for 30 minutes to form a catalyst slurry. 2000 c.c. of SiC carrier (SiC content 98.5%) with an average particle size of 5 mm and an apparent porosity of 20% is placed in a stainless steel rotary furnace that can be heated from the outside and preheated to 200 to 250°C. While rotating the rotary furnace, the catalyst slurry was sprayed onto the carrier to support 180 g of the catalyst material.
It was then calcined for 8 hours at 530°C under a stream of air. The composition of the finished catalyst thus obtained is V ₂ O ₅ :
TiO ₂ :P ₂ O ₅ :Nb ₂ O ₅ :Sb ₂ O ₃ =10:90:0.5:
It was 0.3:6. The pore distribution of the catalyst prepared in this way was measured using a mercury intrusion porosimeter, and the pore diameter was
The pore volume occupied by 0.05-0.45μ pores was 89% of the total pore volume of 10μ or less. 100 c.c. of the obtained catalyst was filled into a stainless steel reaction tube with a diameter of 25 mm, and then immersed in a molten salt bath maintained at 390°C. (Hereinafter, the temperature of the molten salt will be abbreviated as NT (°C).) 15 g of diurene and 500 Nl of air were introduced per hour to cause a reaction. The reaction gas was led to a crystallizer and a water-washed collector to collect the product. When the entire collected product was dissolved in hot water and analyzed, the amount of pyromellitic acid was 113.2 in terms of pyromellitic anhydride.
A yield of % by weight was obtained. Example 2 Ilmenite was mixed with 80% concentrated sulfuric acid, and after a sufficient reaction, the mixture was diluted with water to obtain a titanium sulfate aqueous solution. Iron pieces were added as a reducing agent to reduce the iron content in ilmenite to ferrous ions, which were then cooled and separated as ferrous sulfate.
The aqueous titanium sulfate solution thus obtained was heated to boiling and hydrolyzed to precipitate hydrous titanium oxide. After thoroughly washing this, it was fired at a temperature of 800° C. for 4 hours under air circulation. This was subjected to jet air flow pulverization treatment, with an average particle size of approximately 0.5 μ and a specific surface area of 22 m ² /
g of anatase-type TiO ₂ was obtained. Dissolve 1030 g of oxalic acid in 6400 c.c. of deionized water to make an oxalic acid solution, and add 515 g of ammonium vanadate,
25.9g ammonium monophosphate and niobium chloride
Hydrochloric acid aqueous solution containing 20.3g, antimony trioxide 200
1,600 g of the above TiO ₂ was added to the prepared solution obtained by adding 3.4 g of barium nitrate and 3.4 g of barium nitrate, and the mixture was stirred for 30 minutes to prepare a catalyst slurry. The composition of the finished catalyst obtained by supporting it on a SiC carrier and calcining it in the same manner as in Example 1 is as follows in terms of weight ratio:
V ₂ O ₅ : TiO ₂ : P ₂ O ₅ : Nb ₂ O ₅ : Sb ₂ O ₃ : BaO=
It was 20:80:0.8:0.5:10:0.1. The pore volume occupied by pores with a pore diameter of 0.05 to 0.45 μ in this catalyst is 10 μ
It was less than 86% of the total pore volume. 100 c.c. of the above catalyst was packed into a stainless steel reaction tube with an inner diameter of 25 mm, and 15 g of diurene was added per hour at NT400°C.
When the reaction was carried out by passing 500 Nl of air, pyromellitic anhydride and pyromellitic acid were obtained in a yield of 114.1% by weight in terms of anhydride. Examples 3 to 6 Catalysts having the compositions shown in Table 1 were prepared in the same manner as in Example 1 and subjected to reactions. The results are shown in Table 2.

【table】

[Table] Comparative Example 1 Catalyst described in Example 1 in Japanese Patent Publication No. 49-31972 (V ₂ O ₅ :TiO ₂ :P ₂ O ₅ :Nb ₂ O ₅ :K ₂ O:
Cs ₂ O = 10:90:1.2:0.466:0.142:0.15 weight ratio)
When the reaction was carried out under the same conditions as in Example 1 of the present application, pyromellitic anhydride and pyromellitic acid were obtained in a yield of only 106.7% by weight in terms of anhydride. Comparative Example 2 A catalyst was prepared in the same manner as in Example 1 except that the catalyst component did not contain any Sb ₂ O ₃ and the reaction was carried out. It was obtained in only a high yield.

Claims (1)

[Claims] 1. When producing pyromellitic acid or its anhydride by catalytic gas phase oxidation of 1,2,4,5-tetramethylbenzene with a molecular oxygen-containing gas,
1. A method for producing pyromellitic acid or its anhydride, which comprises using a catalyst comprising oxides of vanadium, titanium, phosphorus, niobium and antimony supported on an inert carrier.