JPH0242818B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing anthraquinone by catalytic gas phase oxidation of anthracene with a molecular oxygen-containing gas. In particular, the present invention provides a method for efficiently producing anthraquinone by carrying out a catalytic oxidation reaction at a higher ratio of anthracene/molecular oxygen-containing gas. [Prior art] Anthraquinone has been produced for a long time by catalytic gas phase oxidation of anthracene, and its yield is 90 mol% or more of the theoretical yield, as shown in the example of Japanese Patent Publication No. 50-24305. has been achieved, and it can be said that the technological level of achievement as a catalyst is extremely high. However, as is clear from the Examples of the same issue, the catalytic oxidation of anthracene has hitherto been carried out under conditions of a very low anthracene/air ratio and a very high space velocity in terms of catalytic performance. This is because this low anthracene/air ratio is considered to be an unavoidable measure to keep the gas composition on the inlet side of the reactor out of the flammable range. Catalytic oxidation at a low anthracene/air ratio concentration has a problem in that it is difficult to maintain the reactor temperature calorically in its industrial implementation. This is due to the excellent selectivity of the catalyst, which means that the amount of heat generated by side reactions such as combustion to carbon dioxide and carbon monoxide (COx) is small, and the heat of formation of anthraquinone is approximately 141 kcal/mol rather than anthracene. Although it depends on the small size, the main reason is that the absolute concentration of the substance to be oxidized is low and the high space velocity allows a large amount of reaction gas to carry away the heat generated in the reactor out of the reactor. For this reason, in actual industrial practice, anthracene containing many impurities such as carbazole and phenanthrene is used as a raw material in order to ensure the calorific value in the reactor, and the heat of combustion reaction of these impurities is used as a raw material. A sufficient amount of heat is ensured to allow the reactor temperature to become self-sustaining. Due to such countermeasures, many impurities were mixed into the anthraquinone produced, and the purification process required many steps. In order to make the oxidation reactor calorically independent, it is preferable to reduce the amount of conducting air in order to suppress the amount of sensible heat of the gas. However, in order to ensure production volume, it is necessary to increase the anthracene/air ratio accordingly. However, under such conditions, excessive oxidation reactions occur with conventionally known catalysts, for example,
The catalyst disclosed in No. 24305 has an anthracene/air ratio of 33.
Although anthraquinone was obtained at a yield of 105% by weight or more at g/ ^NM3 , when the ratio was increased to 80g/ ^NM3 , the hot spot of the catalyst layer became extremely high, resulting in a yield of about 84% by weight. It is known that anthraquinone can only be obtained using
reference). [Problems to be Solved by the Invention] Therefore, the object of the present invention is, firstly, to provide an anthracene/air or molecular oxygen-containing gas ratio of 60
To provide a catalyst for obtaining anthraquinone in high yield by contacting a gas with a high anthracene concentration of 80 g/NM ^{or more} , especially 80 g/NM To provide a catalyst which has sufficiently high activity and selectivity even when the oxygen concentration employed is as low as 5 to 15% by volume in order to avoid explosion.
The purpose of this invention is to provide a practical industrial implementation method for achieving the first and second objectives. [Means for solving the problem] First, as a result of investigating a catalyst composition that has sufficiently high activity even at low oxygen concentrations, we found that alkali metals, thallium, and phosphorus were added to a substance whose main components are vanadium pentoxide and titanium dioxide. , a catalyst in which an active substance containing niobium as a co-catalyst is supported on a porous carrier mainly composed of silicon carbide reduces the oxygen concentration in the raw material gas to 15% by volume or less, especially
It was found that the activity was extremely high even under conditions where the concentration was reduced to 10% by volume or less. In addition, in such a catalyst system, it is possible to add a catalyst with a higher amount of alkali metal or thallium added to the front part of the catalyst layer (the inlet side of the reaction gas), and add a catalyst with a higher amount of alkali metal or thallium added to the rear part than in the front part. By using a stacked catalyst system with a reduced amount of catalyst, high yields can be obtained even in high concentration conditions with much higher anthracene/molecular oxygen-containing gas ratios than is achieved with conventional catalysts. It was discovered that anthraquinone can be obtained by More specifically, the present invention can be specified as follows. (1) When producing anthraquinone by catalytic gas phase oxidation of anthracene with a molecular oxygen-containing gas, the vanadium component is replaced with vanadium pentoxide (V ₂ 1 to 20 parts by weight as O ₅ ), 99 to 80 parts by weight as titanium dioxide (TiO ₂ ), and 100 parts by weight of V ₂ O ₅ and TiO ₂ in total,
5.0 to 12.0 parts by weight of at least one element (X) selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium as an oxide (X ₂ O), and phosphorus component as phosphorus pentoxide ( 0.05 to 5.0 parts by weight as P ₂ O ₅ ) and niobium component as niobium pentoxide (Nb ₂ O ₅ )
A catalytically active material containing 0.05 to 5.0 parts by weight of each catalyst is supported on an inert carrier, and a vanadium component is placed as a subsequent catalyst at a height of 70 to 30% of the total catalyst layer height. V ₂ O ₅
1 to 20% as titanium component and 99 to 80 parts by weight as TiO ₂ and a total of 100 parts of V ₂ O ₅ and TiO ₂
Based on weight part, X component is 0.05 to 3.0 as X ₂ O
A catalytically active substance containing a phosphorus component in the range of 0.05 to 5.0 parts by weight as P ₂ O ₅ and a niobium component in the range of 0.05 to 5.0 parts by weight as Nb ₂ O ₅ is supported on an inert carrier. A method for producing anthraquinone, characterized by arranging. (2) As a molecular oxygen-containing gas, a gas having a composition consisting of 5 to 15% by volume of oxygen, 5 to 10% by volume of water, 0 to 4% by volume of carbon dioxide, and 0 to 2% by weight of carbon monoxide, the balance being essentially nitrogen. The method described in (1) above, which is characterized by using. (3) As an inert support, a porous support having an aluminum content of not more than 10% by weight as aluminum oxide (Al ₂ O ₃ ), a silicon carbide content of at least 50% by weight, and an apparent porosity of at least 10%. The method described in (1) or (2) above, which is characterized in that the method is used. The present invention will be explained in more detail below. In the present invention, the crystal form of titanium dioxide, which is a catalyst raw material, is not particularly limited, and has a specific surface area of 1 to 50 m ² /
g, especially from 1 to 30 m ² /g of anatase form, rutile form or a mixture of both in fine powder form. Other catalyst materials, i.e., alkali metals such as vanadium, lithium, sodium, potassium, rubidium, cesium, thallium, phosphorus, and niobium, may be any starting materials that decompose into oxides when heated. It is appropriately selected from salts, nitrates, sulfates, carbonates, organic acid salts, etc. Furthermore, among the catalyst components related to the present invention, 0 to 60% of titanium dioxide has a specific surface area of 1 to 1.
50 m ² /g, in particular from 1 to 30 m ² /g, may be substituted with finely powdered zirconium dioxide, tin dioxide or a mixture of both, based on a total of 100 parts by weight of both vanadium pentoxide and titanium dioxide. Aluminum in a total amount of up to 3 parts by weight calculated as oxides,
silicon, lead, antimony chromium, tungsten,
Cobalt, iron, nickel and/or manganese can be added. As the inert carrier, alpha alumina, silica, quartz, silicon carbide, silicates of aluminum and magnesium are used, but aluminum content is preferably 10% by weight or less, especially 5% by weight or less as Al ₂ O ₃ and A porous carrier containing 50% by weight or more, especially 80% by weight or more of silicon carbide and having a porosity of 10% or more, especially 20% or more is used. The size of the carrier is preferably spherical, ring or saddle shaped with an average diameter of 3 to 10 mm. The catalytically active substance is supported on the inert carrier by a conventionally known method, but preferably titanium dioxide is emulsified in an oxalic acid or other organic acid solution in which the catalytically active substance is dissolved, and a slurry is prepared. ~
It is carried out by spraying onto a carrier heated to 250°C. The support thus obtained is calcined under air circulation at a temperature of 400 to 550°C for 1 to 10 hours to obtain a finished catalyst. As a finished catalyst, the supported amount of catalytically active material is 3 to 150 g, preferably 8 to 50 g/100 c.c.
carrier range. The oxidation reaction of anthracene is carried out with an inner diameter of 20 to 40 mm, especially 25 to 30 mm, and a length of 1 to 5 m, especially 3 to 3.5 m.
The first stage catalyst and the second stage catalyst are packed in a tube so that the total bed height is 2 to 3 m. At this time, the layer length of the front catalyst is preferably 30 to 70% of the total catalyst layer height.
70-30% is filled with post-catalyst. The reaction tube is immersed in a heat medium tank such as molten salt, and a gas containing anthracene mixed with a molecular oxygen-containing gas is added at 120° C.
Preheat to ~150°C to carry out the oxidation reaction. Air is generally used as the molecular oxygen-containing gas, but other gases include 5-15% by volume of oxygen and 0-15% water vapor.
10% by volume, balance CO ₂ , CO, argon and N ₂
A mixed gas consisting of an inert gas consisting of, etc. is used. such air or molecular oxygen-containing gases;
20 to 100 g of anthracene, especially 60 to 80 g, is loaded to ^1NM3 , and the space velocity is 1000 to 1000 g.
It is introduced into the catalyst layer at 8000 Hr ^-1 , especially from 1000 to 4000 Hr ^-1 . The reaction tube is maintained at 350-450°C with molten salt. In order to carry out the oxidation reaction with a high anthracene/molecular oxygen-containing gas ratio, a part of the waste gas after collecting anthraquinone in a collector or washing tower is dehumidified or recycled to the reactor inlet side without dehumidification. It is safe and economical as an industrial process to mix it with fresh air drawn in and use it as a molecular oxygen-containing gas whose oxygen concentration is adjusted to 5 to 15% by volume, particularly 8 to 12% by volume. Under such conditions, anthraquinone can be obtained from anthracene in a yield of over 100% by weight. The present invention will be explained in more detail below using examples. Example 1 450 g of oxalic acid was dissolved in 6400 c.c. of water to make an oxalic acid aqueous solution, and to this was added 201.2 g of ammonium vanadate,
150.6 g of cesium sulfate, 108.5 g of potassium sulfate, 31.7 g of ammonium dihydrogen phosphate and niobium chloride
19.9g was added and dissolved. This has a specific surface area of 20
1800 g of anatase type TiO ₂ of m ² /g was added and emulsified using a stirrer to obtain a catalyst slurry. In an externally heated rotating drum with a diameter of 30 cm and a length of 50 cm, a spherical material with an average diameter of 5 mm and an apparent porosity of 37%, consisting of 3% by weight of alumina, 92% by weight of silicon carbide, and the balance SiO ₂ was placed. Add porous carrier 2000c.c. and heat to 200℃
preheated to. Next, while rotating the drum, the above catalyst slurry liquid was sprayed to add 10g/10g of the catalytically active material.
It was loaded at a ratio of 100 c.c.-carrier. This support was calcined in an electric furnace at a temperature of 540° C. for 6 hours under air circulation to obtain a completed catalyst. This is the front stage catalyst
Let it be A. A catalyst obtained in the same manner as above, except that 25.1 g of cesium sulfate and 18.1 g of potassium sulfate were used in the above catalyst, was used as post-catalyst-B (carrying amount: 10 g/100 c.c.-carrier). The compositions of the front and rear catalysts were as follows.

[Table] A tube with an inner diameter of 25 mm and a length of 3 m immersed in a molten salt bath was first filled with catalyst-B to a bed height of 1.5 m, and then catalyst-A was packed on top of it to a height of 1 m, and the temperature was increased. 360
It was kept at ℃. To this, 85 g of anthracene (purity 98.5%) was loaded onto a mixed gas of 1 NM ³ consisting of 10 volume % oxygen, 5 volume % water vapor, and 85 volume % nitrogen, and the mixed gas preheated to 150°C was introduced at a space velocity of 2000 Hr ^-1 for reaction. As a result, anthraquinone was obtained with a yield of 108.5% by weight. Example 2 A rutile crystal with a specific surface area of 5 m ² /g was used as titanium dioxide, rubidium carbonate and potassium nitrate were used as alkali metal compounds, 4% by weight of magnesium oxide (MgO) and 7% by weight of SiO ₂ were used as carriers. %, silicon carbide 89% by weight, a spherical porous carrier with an apparent porosity of 42% and a diameter of 6 mm, and the amount of catalytically active material supported was 12 g/100 c.c. Catalysts C and D below were prepared in the same manner as in Example 1.

[Table] In a tube with an inner diameter of 27 mm and a length of 3 m immersed in a molten salt bath, 1.25 m of post-catalyst D was placed, and above that, pre-catalyst C was placed.
Oxygen concentration 8% by volume, water vapor 10% by volume, carbon dioxide 3% by volume, carbon monoxide 1% by volume and nitrogen 78% from the top of the reaction tube packed in a 1.25m stack and maintained at 410°C.
% by volume was loaded with 98.5% pure anthracene at a ratio of 100 g/NM ³ , preheated to 150°C, and then introduced at a space velocity of 2000 Hr ^-1 to carry out the reaction. As a result, anthraquinone was produced with a yield of 107.6% by weight. was gotten. Example 3 In the same manner as in Example 1, titanium dioxide with a specific surface area of 4 m ² /g and an anatase/rutile ratio of 32/68 and a specific surface area of
3.5 m ² /g of tin dioxide, ammonium vanadate,
Ammonium dihydrogen phosphate, niobium chloride, sodium nitrate, thallium nitrate and apparent porosity 35%,
The following catalyst was prepared using a SiC self-sintering carrier with a purity of 98%. The loading rate is 15 for both the front and rear stage catalysts.
g/100 c.c.-carrier.

[Table] In a tube with an inner diameter of 27 mm and a length of 3 m immersed in a molten salt bath, 1 m of post-catalyst F was placed, and above that, pre-catalyst E was placed.
It was packed in layers at a height of 1.5 m and maintained at 415°C. From the upper part of the reaction tube, a synthesis gas containing 8% by volume of oxygen, 5% by volume of water vapor, and 87% by volume of nitrogen was loaded with anthracene with a purity of 98.5% at a ratio of 70 g/NM ³ and was preheated to 150°C and then poured into the space. speed
When the mixture was introduced into a catalyst layer and reacted at 2500 Hr ^-1 , anthraquinone was obtained with a yield of 105.3% by weight. Example 4 Titanium dioxide with a specific surface area of 9 m ² /g, 60% rutile content, and 40% anatase content was used, and the alkali metal compounds used were lithium carbonate, sodium carbonate, cesium sulfate, and potassium sulfate. , except that a ring-shaped self-sintered silicon carbide product with an outer diameter of 8 mm, an inner diameter of 4 mm, and a length of 8 mm with a porosity of 35% was used as the carrier, and the support rate was set to 8.5 g/100 c.c. Catalysts G and H below were prepared using the same catalyst raw materials and in the same manner as in Example 1.

〔Effect of the invention〕

As shown in Examples 1 to 4, the method of the present invention makes it possible to operate with an anthracene concentration more than twice that of the conventional method, and the yield is almost the same as in the case of a low gas concentration. Since a large amount of anthracene can be oxidized by blowing a small amount of air or molecular oxygen-containing gas, a high energy saving advantage can be obtained. In addition, a catalyst with high activity is used as an oxidizing agent for molecular oxygen-containing gas with an oxygen concentration of 15% by volume or less, thereby increasing the anthracene content and at the same time avoiding the danger of combustion of the mixed gas. It has also become possible to adopt a process that recycles waste gas, which is an inert gas. In addition, because such a stacked catalyst greatly suppresses the height of the hot spot in the catalyst layer,
This has the advantage of reducing thermal deterioration of the catalyst and extending the life of the catalyst. For example, although the catalyst according to the example of Japanese Patent Publication No. 50-24305 is used under milder conditions than the catalyst of the present invention, if the degree of yield reduction of the catalyst of the present invention after a certain period of time is 1, Tokuko Showa 50-24305
The degree of yield reduction of the catalyst of Example No. is about 1.5 to 2 times that of the catalyst of the present invention.

Claims (1)

[Claims] 1. When producing anthraquinone by catalytic gas phase oxidation of anthracene with a molecular oxygen-containing gas, a vanadium component is pentoxidized as a pre-stage catalyst at a height of 30 to 70% of the total catalyst layer height. 1 _{to 20} parts by weight of vanadium (V ₂ O _{5 )} and 99 to 80 parts by weight of titanium component as titanium dioxide (TiO ₂ ), and lithium, sodium, 5.0 to 12.0 parts by weight of at least one element (X) selected from the group consisting of potassium, rubidium, cesium, and thallium as an oxide (X ₂ O), and the phosphorus component as phosphorus pentoxide (P ₂ O ₅ ) and 0.05 to 5.0 parts by weight of a niobium component as niobium pentoxide (Nb ₂ O ₅ ) are supported on an inert carrier, As a post-catalyst, a vanadium component of 1 to 20% by weight as V ₂ O ₅ and a titanium component as TiO ₂ of 99 to 80 parts by weight are added to the height of the remaining 70 to 30% of the total catalyst layer height.
For a total of 100 parts by weight of V ₂ O ₅ and TiO ₂ , the X component is 0.05 to 3.0 parts by weight as X ₂ O, and the phosphorus component is P ₂ O ₅
As 0.05~5.0 parts by weight and niobium component Nb ₂ O ₅
1. A method for producing anthraquinone, comprising: supporting an inert carrier with a catalytically active substance containing 0.05 to 5.0 parts by weight of anthraquinone. 2. As the molecular oxygen-containing gas, use a gas with a composition consisting of 5 to 15% by volume of oxygen, 5 to 10% by volume of water, 0 to 4% by volume of carbon dioxide, and 0 to 2% by volume of carbon monoxide, the balance being essentially nitrogen. The method according to claim 1, characterized in that: 3. As an inert support, use a porous support having an aluminum content of not more than 10% by weight as aluminum oxide (Al ₂ O ₃ ), a silicon carbide content of at least 50% by weight, and an apparent porosity of at least 10%. Claim 1 or 2 characterized in that
Method described.