JP2011116660A - Catalytic vapor-phase oxidation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for a stable catalytic vapor-phase oxidation reaction over a long period in an industrial scale. <P>SOLUTION: The catalytic vapor-phase oxidation method includes replacing at least one portion of a catalyst disposed in a gas outlet portion in a reaction gas flow direction with an un-used catalyst and/or additionally charging the un-used catalyst in the gas outlet portion to extend the length of the layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for catalytic vapor phase oxidation of at least one organic compound using molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor packed with a catalyst. Specifically, at least a part of the catalyst having deteriorated activity arranged at the gas outlet with respect to the reaction gas flow direction is replaced with an unused catalyst and / or an additional catalyst is additionally filled to extend the catalyst layer length. The present invention relates to a contact gas phase oxidation method.

  In the petrochemical industry, the catalytic gas phase oxidation reaction using a fixed bed reactor is, for example, production of ethylene oxide by catalytic gas phase oxidation of ethylene, propylene, isobutylene, tertiary butanol and / or methyl tertiary butyl ether. Production of (meth) acrylic acid by two-step oxidation as a starting material, production of phthalic anhydride by catalytic gas phase oxidation of o-xylene and / or naphthalene, maleic anhydride by catalytic gas phase oxidation of benzene and n-butane Many productions have been implemented.

  In the catalytic gas phase oxidation reaction using such a fixed bed reactor, various proposals have been made by various companies for the purpose of producing a target product stably and efficiently for a longer period of time.

  For example, in Patent Document 1 and Patent Document 2, at least a part of the catalyst deteriorated by the catalytic gas phase oxidation reaction is extracted and replaced with an unused catalyst, so that the entire catalyst layer is stable for a long time without replacement. Thus, a method for producing the target product is disclosed. Patent Document 3 discloses that in a reactor having a heat exchange medium circulation mechanism having an oblique impeller, the uppermost catalyst layer can be replaced with an unused catalyst for the reaction.

US Patent Publication (US-A1) 2004/0015013 US Patent Publication (US-A1) 2007/0155988 JP 2003-83289 A

  However, the methods described in Patent Documents 1 to 3 substantially extract and replace a part of the catalyst filled in the gas inlet portion with respect to the reaction gas flow direction. Since it is necessary to extract and replace even the preheating layer arranged on the upstream side of the catalyst of the part, it is not preferable from the economical aspect. In Patent Document 1 and Patent Document 3, in order to replace a part of the catalyst at the gas inlet portion whose performance has deteriorated with an unused catalyst as it is, the catalytic activity between the replaced part and the part already subjected to the reaction is changed. This balance is not balanced and it becomes difficult to control the local high temperature heat generating part, which may cause a runaway reaction. Further, there is a possibility that catalyst deterioration is accelerated by the excessive heat generation, which is not preferable from the viewpoint of safe operation as well as long-term operation. As a countermeasure, Patent Document 2 discloses using a catalyst having a reduced volume specific activity as compared with an unused catalyst when exchanging the catalyst at the reaction gas inlet, but it is substantially unused. This is a method of diluting the catalyst with an inert carrier. In this case, the amount of catalyst charged into the reaction tube, that is, the amount of active component is reduced, and the load of the newly charged catalyst is increased, so that the long-term operation is required. Is not preferable.

  Thus, the object of the present invention is long-run on an industrial scale in catalytic gas phase oxidation of at least one organic compound with molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor packed with a catalyst. It is an object of the present invention to provide a method for performing a catalytic gas phase oxidation reaction safely and stably over a period of time.

  In the catalytic gas phase reaction, the present invention has a reaction order with respect to the reaction substrate (raw material) almost in the first order, in contrast to the above-described conventional techniques. In the known method of filling so that the activity increases from the gas inlet portion toward the outlet portion as in the embodiment, it is more effective to recover the lowered catalyst performance by replacing the outlet portion than replacing the catalyst at the gas inlet portion. As a result of diligent investigations on the assumption that the oxygen concentration would be high, catalytic gas phase oxidation of at least one organic compound with molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor packed with a catalyst was used for the reaction. Even if the catalyst layer is a catalyst layer, the catalyst arranged at the gas outlet with respect to the direction of the reaction gas flow has no local high-temperature heat generation and the catalyst performance is stabilized. At least a part of the catalyst layer is replaced with an unused catalyst. And By extending the catalyst layer length by additionally filling unused catalyst, the performance deteriorated by the reaction for a long period of time can be recovered efficiently without affecting the balance of the catalyst activity. The present inventors have found that it is possible to carry out a catalytic gas phase oxidation reaction stably and safely.

  According to the present invention, by solving the above problems, it is possible to perform a stable catalytic gas phase oxidation reaction on an industrial scale for a long period of time.

  Hereinafter, the contact gas phase oxidation method according to the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention is changed as appropriate without departing from the spirit of the present invention. And can be implemented.

  According to the present invention, in the catalytic gas phase oxidation of at least one organic compound with molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor packed with a catalyst, when the performance deteriorates due to the reaction. In addition, at least a part of the catalyst arranged at the gas outlet in the reaction gas flow direction may be replaced with an unused catalyst and / or an unused catalyst may be additionally charged to extend the catalyst layer length. In addition, the unused catalyst in this invention is a catalyst which has not been used for reaction.

  When the catalyst layer length is extended by replacing at least one part of the catalyst arranged at the gas outlet with respect to the reaction gas flow direction with an unused catalyst and / or additionally charging an unused catalyst at the gas outlet, It is more effective if the exchange amount of the catalyst or the additional filling amount of the catalyst or the total amount of the exchange amount of the catalyst and the additional filling amount is 1% or more, preferably 3% or more of the catalyst layer length. If the replacement amount or the additional charge amount of the catalyst or the total amount of the catalyst replacement amount and the additional charge amount is less than 1%, the performance recovery effect is insufficient, and the work frequency increases during long-term operation, As a result, the period during which the reaction is stopped becomes long, and a sufficient production amount cannot be secured. However, when replacing a deteriorated catalyst, the upper limit of the replacement amount is at most about 1/3 of the entire catalyst layer packed in the reaction tube from the viewpoint of economic balance and catalyst activity. is there. When 1/3 or more of the entire catalyst layer is replaced, not only an effect commensurate with the replacement amount of the expensive catalyst is obtained, but also the catalyst having a large degree of performance deterioration is replaced, and the balance of the activity as described above. May be affected. If the catalyst filled in the reaction gas outlet of the reaction tube is exchanged by about 10% of the catalyst layer, an effect corresponding to the exchange amount can be sufficiently obtained within a range that does not affect the balance of activity.

  When an unused catalyst is additionally filled at the outlet of the reaction gas, the pressure loss increases and the performance recovery effect due to the additional filling, although it varies depending on the length of the space of the reaction gas outlet of the reaction tube filled with the catalyst. Therefore, it is sufficient to add about 10% of the already packed catalyst layer length.

Further, even when the catalyst is exchanged and the additional filling is performed simultaneously, a sufficient effect can be obtained when the total amount is about 10% of the catalyst layer length.
In order to operate stably for a long period of time, it is preferable to periodically extend the layer length by exchanging the catalyst and / or additionally filling the catalyst, and at least once / year. preferable.
The method for exchanging and / or additionally filling the catalyst is not particularly limited, and can be performed according to a known method. For example, when exchanging the catalyst, when extracting the catalyst arranged at the gas outlet with respect to the reaction gas flow direction, a suction pipe connected to an exhaust suction device as in JP-A-2002-301355 is placed in the reaction pipe. The method of inserting and extracting with an air flow etc. can be used suitably. In addition, when the catalyst is filled in the reaction tube at the time of catalyst replacement or when the catalyst layer length is extended, a method of filling using a filling machine with controlled vibration such as JP-A-10-202084, JP-A 20002- For example, as described in Japanese Patent No. 306953, a method in which the volume is preliminarily measured so as to be uniform and the filling is performed with a predetermined filling time can be suitably used.

There is no restriction | limiting in particular as a catalyst used by this invention, The well-known catalyst generally used in catalytic gas phase oxidation can be used, For example, following (1)-(9) etc. are mentioned.
(1) A catalyst for producing ethylene oxide by containing silver as an essential component and oxidizing ethylene in a gas phase,
(2) For producing (meth) acrolein and (meth) acrylic acid by containing molybdenum, bismuth and iron as essential components and oxidizing propylene, isobutylene, tertiary butanol and / or methyl tertiary butyl ether in the gas phase catalyst,
(3) A catalyst for producing acrylic acid by oxidizing acrolein in the gas phase, containing molybdenum and vanadium as essential components,
(4) a catalyst for producing methacrylic acid by oxidizing molybdenum in the gas phase, containing molybdenum and phosphorus as essential components,
(5) A catalyst for producing phthalic anhydride by oxidizing vanadium and titanium as essential components and oxidizing o-xylene and / or naphthalene in a gas phase,
(6) A catalyst for producing maleic anhydride by oxidizing molybdenum in the gas phase, containing molybdenum as an essential component,
(7) A catalyst for producing maleic anhydride by oxidizing phosphorus in the gas phase and containing phosphorus and vanadium as essential components,
(8) A catalyst for producing propylene, acrolein and / or acrylic acid by oxidizing molybdenum in the gas phase, containing molybdenum as an essential component,
(9) In addition, a solid granular catalyst used in a catalytic gas phase oxidation reaction by filling a fixed bed multitubular reactor.

  These catalysts can be produced by various conventionally known methods and are not particularly limited.

  The catalyst charged in the reactor does not need to be a single type of catalyst in each of the cases (1) to (9), and a plurality of types of catalysts having different compositions, shapes, and activities are each active. It is also possible to fill the layers so as to form the layers in a different order, or to mix and fill the layers. Further, a part of the catalyst can be diluted with an inert carrier or the like.

In the present invention, when exchanging the catalyst disposed at the gas outlet and / or additionally filling the gas outlet with respect to the direction of the reaction gas flow, the reaction gas flow introduced into the reactor is naturally from the bottom to the top of the reactor. Therefore, a known reactor can be used as long as it is an upflow. For example, in a method for producing acrylic acid by two-stage oxidation of propylene, a reactor (pre-stage reactor) filled with a catalyst (pre-stage catalyst) suitable for catalytic vapor phase oxidation of propylene mainly on acrolein and the obtained acrolein A reactor in which two reactors (secondary reactor) filled with a catalyst (secondary catalyst) suitable for catalytic gas phase oxidation of acrylic acid with acrylic acid are both up-flow, or a reaction in which the first catalyst is charged at the bottom One reactor provided with a zone (front reaction zone) and a reaction zone (second stage reaction zone) filled with a rear catalyst at the top can be used. In that case, the catalyst layer length extension by the replacement and / or additional filling of the catalyst in the present invention may be performed in either the front stage catalyst or the rear stage catalyst, and naturally it may be performed for both the front stage catalyst and the rear stage catalyst. The reaction tubes of these reactors are not particularly limited, but preferably have an inner diameter of 15 to 50 mm.
In the method for producing acrylic acid by two-stage oxidation of propylene, suitable reaction temperatures for the former catalyst and the latter catalyst are appropriately selected depending on the reaction conditions and the like, but the former catalyst is usually 300 to 380 ° C. Moreover, it is 250-350 degreeC normally with a back | latter stage catalyst. Furthermore, the difference between the reaction temperature of the former catalyst and the reaction temperature of the latter catalyst is 10 to 110 ° C, preferably 30 to 80 ° C.

  The reaction temperature of the front catalyst and the reaction temperature of the rear catalyst substantially correspond to the heat medium inlet temperature in each reactor or reaction zone, and the heat medium inlet temperature is set within the above range. It is determined according to each set temperature. Hereinafter, the present invention will be described more specifically with reference to examples.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and may be implemented with appropriate modifications within a range that can meet the gist of the present invention. These are all included in the technical scope of the present invention. Hereinafter, for convenience, “parts by mass” may be simply referred to as “parts”. The conversion rate and yield are defined as follows.
Conversion rate (mol%)
= (Number of moles of reacted raw material / number of moles of supplied raw material) × 100
Yield (mol%)
= (Number of moles of target product produced / number of moles of supplied raw material) x 100
<Reference Example 1>
[Preparation of Oxide Catalysts (1) and (2)]
While heating and stirring 2000 parts of distilled water, 350 parts of ammonium molybdate was dissolved (solution A). Separately, 250 parts of cobalt nitrate and 120 parts of nickel nitrate are dissolved in 500 parts of distilled water (liquid B), and separately, nitric acid is added to a solution made acidic by adding 18 parts of concentrated nitric acid (65% by mass) to 350 parts of distilled water. 80.1 parts of ferric iron and 120 parts of bismuth nitrate were dissolved (C solution). These nitrate solutions (B solution and C solution) were added dropwise to the A solution. Subsequently, 1.67 parts of potassium nitrate were added. The suspension thus obtained was heated, stirred and evaporated. The obtained dried product was dried at 200 ° C. and pulverized to 150 μm or less to obtain catalyst powder. Into a rolling granulator, 1400 parts of an alumina spherical carrier having an average particle diameter of 4 mm was charged, and then catalyst powder was gradually added together with a 35 mass% ammonium nitrate aqueous solution as a binder to be supported on the carrier, and then in an air atmosphere. Heat treatment was performed at 470 ° C. for 6 hours to obtain an oxide catalyst (1). The metal element composition excluding the carrier and oxygen of this catalyst was as follows.

Mo ₁₂ Bi _1.5 Co _5.2 Ni _2.5 Fe _1.2 K _0.1
Further, the loading rate calculated from the following formula of this oxide catalyst was about 30% by mass.

Support rate (mass%) = (oxide catalyst mass−support mass) / support mass × 100
Similarly, an oxide catalyst (2) supported on a spherical alumina carrier having an average particle diameter of 7 mm was obtained.
[Reactor]
Three reactors (A, B, C) comprising a SUS reaction tube having a total length of 3000 mm and an inner diameter of 25 mm and a shell for flowing a heat medium covering the SUS reaction tube were prepared in the vertical direction. For each reactor, an inert ceramic ball having an average particle diameter of 8 mm, an oxide catalyst (2), and an oxide catalyst (1) are sequentially dropped from the upper part of the reaction tube as a preheating layer, and the respective layer lengths are changed in order from the bottom. , Ceramic balls: 100 mm, oxide catalyst (2): 700 mm, oxide catalyst (1): packed to 2000 mm, and the catalyst filling specifications of the three reactors (A, B, C) are substantially the same. It was.
[Oxidation reaction]
In each of the three reactors filled with the oxide catalyst, a mixed gas of 8.3% by volume of propylene, 15% by volume of oxygen, 30% by volume of water vapor, and 46.7% by volume of nitrogen at a space velocity of 1800 hr ⁻¹ (STP). The reaction was introduced from the lower part of the reactor, and the catalytic gas phase oxidation reaction was continued for 8000 hours. The reaction results are shown in Table 1. All three units had almost the same performance.
<Comparative Example 1>
In Reference Example 1, after 8000 hours of the reaction, the catalyst A was not extracted from the reactor A and the reaction was continued for 8000 hours. Table 1 shows the reaction results at the accumulated time of 12000 hours and 16000 hours.
<Example 1>
In Reference Example 1, after 8000 hours of the reaction, the oxide catalyst (1) was extracted from the upper part of the reaction tube for the reactor B by a layer length of 20 mm, and an unused oxide catalyst (1) was replaced by a layer length of 20 mm instead. After filling and exchanging the catalyst, the reaction was further continued for 4000 hours (cumulative time 12000 hours). Table 1 shows the reaction results immediately after the catalyst replacement (48 hours after the replacement) and at a cumulative time of 12000 hours.
<Example 2>
In Example 1, after 12,000 hours of cumulative time elapsed, an unused oxide catalyst (1) was additionally charged from the upper part of the reaction tube to extend the catalyst layer length by 40 mm, and the reaction was further continued for 4000 hours (cumulative time elapsed). 16000 hours). Table 1 shows the reaction results immediately after extension of the catalyst layer length (48 hours after extension) and at a cumulative time of 16000 hours.
<Example 3>
In Reference Example 1, after 8000 hours of the reaction, the oxide catalyst (1) was extracted from the upper part of the reaction tube for the reactor C by a layer length of 30 mm, and an unused oxide catalyst (1) was replaced by a layer length of 30 mm instead. After filling and exchanging the catalyst, the reaction was further continued for 4000 hours (cumulative time 12000 hours). Table 1 shows the reaction results immediately after the catalyst replacement (48 hours after the replacement) and the accumulated time of 12000 hours.
<Example 4>
In Example 3, after the accumulated time of 12000 hours, the oxide catalyst (1) was extracted from the upper part of the reaction tube by the length of 60 mm. Instead, the unused oxide catalyst (1) was refilled by the length of 60 mm and further reacted. After the unused oxide catalyst (1) was additionally charged from the upper part of the tube and the catalyst layer length was extended by 40 mm, the reaction was continued for 4000 hours (total time: 16000 hours). Table 1 shows the reaction results immediately after the catalyst exchange and extension of the layer length (48 hours after exchange / extension) and at a cumulative time of 16000 hours.

<Reference Example 2>
In Reference Example 1, the oxide catalyst (1), the oxide catalyst (2), and an inert ceramic ball having an average particle size of 8 mm are sequentially dropped from the upper part of the reaction tube as the preheating layer, and the respective layer lengths are oxidized from below. Product catalyst (1): 2000 mm, oxide catalyst (2): 700 mm, ceramic balls: packed to 100 mm, mixed gas similar to that of Reference Example 1 was introduced from the top of the reactor, and catalytic gas phase oxidation reaction was carried out to 8000 The time continued. The reaction results are shown in Table 2.
<Comparative Example 2>
In Reference Example 2, after 8000 hours of the reaction, the whole ceramic ball was extracted from the upper part of the reaction tube, and then the oxide catalyst (2) at the gas inlet was removed by 200 mm. Instead, the unused oxide catalyst (2) was again removed at 200 mm. After the ceramic balls were filled and the catalyst was exchanged, the reaction was further continued for 4000 hours (total time of 12000 hours). Table 2 shows the reaction results immediately after the catalyst replacement (48 hours after the replacement) and the accumulated time of 12000 hours. The operation at the optimum reaction temperature was not possible due to the local high temperature heating part, and the performance was low.

<Reference Example 3>
[Preparation of Oxide Catalysts (3) and (4)]
While heating and stirring 2400 parts of distilled water, 380 parts of ammonium paramolybdate, 83.9 parts of ammonium metavanadate, and 72.7 parts of ammonium paratungstate were dissolved therein. Separately, 46.3 parts of water was heated and stirred, and 56.3 parts of copper nitrate and 36.5 parts of cobalt nitrate were dissolved. The two aqueous solutions obtained were mixed, and 26.1 parts of antimony trioxide was further added to obtain a suspension. This suspension was dried with a spray dryer. The obtained granular powder was calcined at 392 ° C. for about 5 hours in an air atmosphere. At this time, a thermometer was inserted into the granular powder, and the temperature was raised while adjusting the furnace temperature so as not to cause a rapid temperature rise. The calcined granular powder was pulverized to 150 μm or less to obtain catalyst powder. After 1500 parts of a silica-alumina spherical carrier having an average particle size of 4.5 mm is put into a rolling granulator, catalyst powder is gradually put together with a 15% by mass glycerin aqueous solution as a binder and supported on the carrier. The oxide catalyst (3) was obtained by heat treatment at 400 ° C. for 6 hours in an air atmosphere. The catalyst loading was about 30% by mass, and the metal element composition excluding the carrier and oxygen was as follows.
Catalyst 1: Mo ₁₂ V ₄ W _1.5 Cu _1.3 Sb _1.0 Co _0.7
Similarly, an oxide catalyst (4) supported on a silica-alumina spherical carrier having an average particle diameter of 7.5 mm was obtained.
[Reactor]
Three reactors (D, E, F) comprising a SUS reaction tube having a total length of 3000 mm and an inner diameter of 25 mm and a shell for flowing a heat medium covering the SUS reaction tube were prepared in the vertical direction. An inert ceramic ball having an average particle diameter of 8 mm, an oxide catalyst (4), and an oxide catalyst (3) are sequentially dropped as a preheating layer from the upper part of each reaction tube, and the respective layer lengths are ceramic balls in order from the bottom; 100 mm, oxide catalyst (4); 600 mm, oxide catalyst (3): packed to 2000 mm, and the catalyst filling specifications of the three reactors (D, E, F) were substantially the same.
[Oxidation reaction]
In each of the three reactors filled with the oxide catalyst, a mixed gas of 7.7% by volume of acrolein, 9.9% by volume of oxygen, 35% by volume of water vapor, and 47.4% by volume of nitrogen was supplied from the lower part of the reactor at a space velocity of 1800 hr. ^-1 (STP) and the catalytic gas phase oxidation reaction was continued for 8000 hours. The reaction results are shown in Table 3. All three units had almost the same performance.
<Comparative Example 3>
In Reference Example 3, after 8000 hours of the reaction, the catalyst D was not extracted from the reactor D, and the reaction was continued for 8000 hours. Table 3 shows the reaction results at the accumulated time of 12000 hours and 16000 hours.
<Example 5>
In Reference Example 3, after 8000 hours of the reaction, the oxide catalyst (3) was extracted from the upper part of the reaction tube for the reactor E by 30 mm, and the unused oxide catalyst (3) was replaced by 30 mm for the layer length instead. After filling and exchanging the catalyst, the reaction was further continued for 4000 hours (cumulative time 12000 hours). Table 3 shows the reaction results immediately after the catalyst exchange (at the time when 48 hours have passed after the exchange) and at a cumulative time of 12000 hours.
<Example 6>
In Example 5, after 12,000 hours of cumulative time elapsed, the oxide catalyst (3) was extracted from the upper part of the reaction tube by a layer length of 60 mm. Instead, an unused oxide catalyst (3) was refilled by a layer length of 60 mm. The reaction was continued for 4000 hours (cumulative time 16000 hours). Table 3 shows the reaction results immediately after the catalyst replacement (when 48 hours had elapsed after the replacement) and at a cumulative time of 16000 hours.
<Example 7>
In Reference Example 3, after 8000 hours of the reaction, the reactor F was additionally filled with unused oxide catalyst (3) from the upper part of the reaction tube to extend the catalyst layer length by 90 mm, and then the reaction was further continued for 4000 hours. (Total time of 12000 hours). Table 3 shows the reaction results immediately after the catalyst layer length extension (48 hours after the layer length extension) and at a cumulative time of 12000 hours.
<Example 8>
In Example 7, after 12,000 hours of cumulative time elapsed, the oxide catalyst (3) was extracted from the upper part of the reaction tube by a layer length of 150 mm. Instead, an unused oxide catalyst (3) was refilled by a layer length of 150 mm. The reaction was continued for 4000 hours (cumulative time 16000 hours). Table 3 shows the reaction results immediately after the catalyst replacement (when 48 hours had elapsed after the replacement) and at a cumulative time of 16000 hours.

<Reference Example 4>
[First reactor]
In the fixed bed multitubular reactor composed of 13,000 reaction tubes (reaction tube diameter 25 mm, length 3000 mm) and a shell for flowing a heat medium covering the reaction tube, an average particle is formed as a preheating layer from the top of each reaction tube. An inactive ceramic ball having a diameter of 8 mm, the oxide catalyst (2), and the oxide catalyst (1) are dropped sequentially, and the respective layer lengths in the respective reaction tubes are ceramic balls in order from the bottom; 100 mm, the oxide catalyst (2 ); 600 mm, oxide catalyst (1);
[Second reactor]
In the fixed bed multitubular reactor composed of 13,000 reaction tubes (reaction tube diameter 25 mm, length 3000 mm) and a shell for flowing a heat medium covering the reaction tube, an average particle is formed as a preheating layer from the top of each reaction tube. An inactive ceramic ball having a diameter of 8 mm, an oxide catalyst (4), and an oxide catalyst (3) are dropped sequentially, and in each reaction tube, each layer length is in order from the bottom ceramic ball; 100 mm, oxide catalyst (4 ); 600 mm, oxide catalyst (3);

The outlet of the first reactor and the inlet of the second reactor were connected by a steel pipe having an inner diameter of 500 mm and a length of 5000 mm so that it could be heated from the outside with steam.
[Oxidation reaction]
A mixed gas consisting of 8.2% by volume of propylene, 15% by volume of oxygen, 32% by volume of water vapor and 44.8% by volume of nitrogen is fed into the first reactor from the bottom of the first reactor. The catalyst was introduced at a space velocity of 1700 h ⁻¹ (STP) with respect to the packed catalyst, the reaction gas produced in the first reactor was introduced from the lower part of the second reactor, and the catalytic gas phase oxidation reaction was continued for 8000 hours. The reaction results are shown in Table 4.
<Example 9>
In Reference Example 4, after 8000 hours of the reaction, the oxide catalyst (1) was extracted by 100 mm from the upper part of each reaction tube of the first reactor, and an unused oxide catalyst (1) was used instead. After refilling for 100 mm, an unused oxide catalyst (1) was further charged from the top of each reaction tube to extend the catalyst layer length by 50 mm. Similarly, in the second reactor, the oxide catalyst (3) is extracted from the upper part of each reaction tube by a layer length of 100 mm, and after refilling with an unused oxide catalyst (3) by a layer length of 100 mm, An unused oxide catalyst (3) was additionally charged from the upper part of each reaction tube, the catalyst layer length was extended by 50 mm, and the reaction was continued for 4000 hours (total time of 12000 hours). Table 4 shows the reaction results immediately after the catalyst exchange extension (48 hours after the exchange / extension) and at a cumulative time of 12000 hours.
<Example 10>
In Example 9, after a cumulative time of 12000 hours, the oxide catalyst (1) was extracted from the upper part of each reaction tube of the first reactor by a layer length of 200 mm, and an unused oxide catalyst (1) was replaced by a layer length of 200 mm instead. Refilled minutes. Similarly, in the second reactor, the oxide catalyst (3) is extracted from the upper part of each reaction tube by a layer length of 200 mm, and is filled with an unused oxide catalyst (3) by a layer length of 200 mm, and then further reacted. For 4000 hours (cumulative time of 16000 hours). Table 4 shows the reaction results immediately after the catalyst replacement (48 hours after the replacement) and the cumulative time of 16000 hours.

Claims (4)

  In a method of catalytic vapor phase oxidation of at least one organic compound with molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor packed with a catalyst, the gas outlet is positioned in the direction of the reaction gas flow. Catalytic gas phase oxidation characterized in that at least a part of the catalyst having a deteriorated activity is replaced with an unused catalyst and / or an unused catalyst is additionally filled in the gas outlet to extend the catalyst layer length. Method.   When the catalyst layer length is extended by replacing at least one part of the catalyst arranged at the gas outlet with respect to the reaction gas flow direction with an unused catalyst and / or additionally charging an unused catalyst at the gas outlet, 2. The catalytic gas phase oxidation method according to claim 1, wherein the exchange amount of the catalyst or the additional filling amount of the catalyst or the total amount of the exchange amount of the catalyst and the additional filling amount is 1% or more of the catalyst layer length.   When extending the catalyst layer length by replacing at least one part of the catalyst arranged at the gas outlet with respect to the gas flow direction with an unused catalyst and / or additionally charging the catalyst with an unused catalyst at the gas outlet The catalytic gas phase oxidation method according to claim 1 or 2, wherein the exchange amount of the catalyst, the additional charge amount of the catalyst, or the total amount of the catalyst exchange amount and the additional charge amount is 10% or less of the catalyst layer length. . The catalytic vapor phase oxidation method according to any one of claims 1 to 3, wherein the catalytic vapor phase oxidation reaction is at least one selected from the group consisting of the following (1) to (8).
(1) Catalytic gas phase oxidation reaction for producing ethylene oxide by vapor phase oxidation of ethylene (2) Gas phase oxidation of propylene, isobutylene, tertiary butanol and / or methyl tertiary butyl ether to (meth) acrolein and Catalytic gas phase oxidation reaction for producing (meth) acrylic acid (3) Catalytic gas phase oxidation reaction for producing acrylic acid by vapor phase oxidation of acrolein (4) Gas phase oxidation of methacrylic acid to methacrylic acid (5) Catalytic gas phase oxidation reaction for producing phthalic anhydride by gas phase oxidation of ortho-xylene and / or naphthalene (6) Gas phase oxidation of benzene and anhydrous Catalytic gas phase oxidation reaction for producing maleic acid (7) Catalytic gas phase oxidation reaction for producing maleic anhydride by vapor phase oxidation of n-butane (8) propane and gas phase oxidation of propylene, acrolein and / or catalytic gas phase oxidation reaction for the production of acrylic acid