JP2009084167A - Manufacturing method of acrolein and/or acrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing acrolein and/or acrylic acid by a catalytic gas-phase oxidation of propylene and/or propane, where acrolein and/or acrylic acid are manufactured in a high yield stably for a long period of time on an industrial scale even when the operation is temporarily suspended and then resumed. <P>SOLUTION: On suspending an operation of a catalytic gas-phase oxidation process, the feed of a reaction raw material gas is suspended; subsequently an inert gas is fed to the reactor followed by feeding a molecular oxygen-containing gas; then the feed of the molecular oxygen to the reactor is suspended. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a fixed bed reactor having a reaction tube filled with a gas phase oxidation catalyst, and a propylene and / or propane is subjected to catalytic gas phase oxidation with molecular oxygen or a molecular oxygen-containing gas, thereby acrolein and / or acrylic acid. It relates to a method of manufacturing.

  Acrylic acid is an industrially important material as a raw material for various synthetic resins, paints, and plasticizers. In recent years, the importance as a raw material for water-absorbing resins has increased, and the demand for acrylic acid tends to increase.

  As a method for producing acrylic acid, a two-stage contact gas phase oxidation method using propylene as a raw material is the most common and widely used industrially. As a form of this method, in a first fixed bed reactor packed with a catalyst for converting propylene to acrolein (hereinafter referred to as “pre-stage catalyst”), a raw material gas containing propylene and molecular oxygen is supplied. Acrolein is converted into acrolein by catalytic gas phase oxidation, and the resulting gas is oxidized in a second fixed bed reactor packed with a catalyst for converting the obtained acrolein into acrylic acid (hereinafter referred to as “second-stage catalyst”). Method for producing acid, and method for producing acrylic acid by catalytic gas phase oxidation of a raw material gas containing propylene and molecular oxygen in a fixed bed reactor in which a first stage catalyst and a second stage catalyst are packed in one reactor There are two main methods.

  In recent years, propane, which is cheaper than propylene, is used as a raw material to produce propylene by dehydrogenation or oxidative dehydrogenation, and the obtained propylene is subjected to the above-mentioned two-stage contact gas-phase oxidation, or the propane is directly contacted in one stage. Various studies have been made.

  In such a method for producing acrylic acid by catalytic gas phase oxidation of propylene and / or propane, various proposals have been made for the purpose of producing a high yield and stable for a long period of time safely. Some proposals have also been made on how to stop or start up.

  For example, Patent Document 1 discloses that deterioration of catalyst performance can be prevented by supplying a gas containing oxygen to the reactor even when the operation of the catalytic gas phase oxidation step is stopped.

  In Patent Document 2, the operation is performed only when the concentration value of each gas obtained by calculation based on the flow rate of each introduced gas at the reactor inlet and the analysis value by the gas analyzer are both out of the set range. By stopping the operation, there is disclosed a method for eliminating an emergency stop of useless operation and stopping it only when it is necessary to stop.

  Further, Patent Document 3 discloses a safe reactor by avoiding the explosion range undertaken by the composition of the raw material to be oxidized and the molecular oxygen-containing gas supplied to the reactor, and reducing the supply amount of the dilution gas. It is disclosed that startups can be achieved.

JP 2005-314314 A JP 2004-277339 A JP 2002-53519 A

  However, acrylic acid is currently produced at a scale of several million tons / year, and if the yield is improved even at an industrial scale of 0.1%, it will be very economically significant. Furthermore, it is even more so if it can be manufactured stably over a longer period of time. Although the above-described production method or stopping method has been improved in the yield of the target acrylic acid and long-term production, there is still room for improvement in view of the recent increase in demand.

  In Patent Document 1, unless oxygen is continuously supplied while maintaining the temperature of the catalyst until the operation of the catalytic gas phase oxidation step is stopped and the operation is restarted, a part of heavy fuel accumulated on the catalyst is stored. Reducing substances such as by-products reduce the catalyst and the oxidation state of the catalyst changes, so the performance of the catalyst deteriorates.For this reason, if molecular oxygen is supplied even when the operation is stopped, the oxidation state of the catalyst is reduced. It is disclosed that the performance of the catalyst is maintained and does not deteriorate. However, in this embodiment, there is only the effect of filling the reaction tube with a new catalyst that has not been subjected to the reaction and supplying the oxygen-containing gas before the operation. No evaluation has been made on the catalyst in the case of stopping the reaction by periodic inspection or emergency stop. When the operation is stopped after being once subjected to the reaction, if the oxygen is continuously supplied while maintaining the temperature of the catalyst, the oxidation of the catalyst proceeds and a high yield in a steady state is obtained. The subtle oxidation state of the catalyst that has been lost collapses, and the yield decreases until a steady state is reached after restarting, which is not sufficient for stable production over a long period of time.

  Patent Document 2 relates to a method capable of avoiding an emergency stop due to a malfunction of an analyzer and the like and capable of performing an emergency stop only when necessary, and does not disclose any influence on the catalyst performance in the operation stop.

  Patent Document 3 relates to a method for efficiently starting up a reaction from an operation stop state, and does not disclose any influence on catalyst performance in operation stop as in Patent Document 2.

  Thus, an object of the present invention is to temporarily interrupt operation on an industrial scale by periodic inspection or emergency stop in a method for producing acrolein and / or acrylic acid by catalytic gas phase oxidation of propylene and / or propane. Even in such a case, the object is to provide a method for producing acrolein and / or acrylic acid in a high yield stably for a long period of time while maintaining a high yield even after resumption of operation.

  As a result of intensive studies to solve the above problems, the inventors of the present invention produce acrolein and / or acrylic acid by catalytic vapor phase oxidation of propylene and / or propane with molecular oxygen or a molecular oxygen-containing gas. In the method, when stopping the operation of the catalytic gas phase oxidation step, after the supply of the reaction raw material gas is stopped, the inert gas is supplied to the reactor, and then the supply of the inert gas is stopped, After the supply of the oxygen-containing gas, the molecular oxygen supply to the reactor was stopped, and it was found that even if the operation is started again, it can be produced stably and safely for a long time with a high yield.

  According to the present invention, in the method of producing acrolein and / or acrylic acid by catalytic vapor phase oxidation of propylene and / or propane with molecular oxygen or a molecular oxygen-containing gas, There is no decrease in yield due to stopping and restarting, and high yield and stable and safe production over a long period of time are possible.

  Hereinafter, the method for producing acrolein and / or acrylic acid by 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 the present invention is not limited to the following examples. The present invention can be changed and implemented as appropriate without departing from the spirit of the invention.

  According to the present invention, when the operation of the catalytic gas phase oxidation step is stopped, the supply of a mixed gas composed of propylene and / or propane, molecular oxygen and an inert gas (hereinafter referred to as “reaction raw material gas”) is performed. After stopping, the inert gas is supplied to the reactor, and then the molecular oxygen-containing gas is preferably supplied in a temperature range of 260 ° C. to 440 ° C., particularly preferably, and then the gas supply is stopped. Examples of the operation stop in the present invention include stop by inspection of the apparatus, replacement of parts and the like, emergency stop due to apparatus trouble, and the like.

  When the operation is stopped, the supply of the reaction raw material gas naturally needs to be stopped. However, even if the supply of the reaction raw material gas is stopped, the reaction raw material gas or its reaction product-containing gas remains in the reactor and the piping, so the molecular oxygen-containing gas is supplied in this state. Then, an explosion composition that may cause an explosion may be formed by an ignition source such as a high-temperature object or an electric spark. Therefore, it is necessary to stop the supply of the reaction raw material gas, and then introduce the inert gas composed of nitrogen, water vapor, etc. into the production apparatus to release the raw material gas remaining in the system out of the system. is there. The amount of the inert gas introduced varies depending on the size inherent to the apparatus and cannot be specified unconditionally. However, it is usually sufficient to introduce an amount of about 30 times the reactor and piping capacity.

  If the reaction system can be replaced with the inert gas, then a molecular oxygen-containing gas may be introduced into the reactor. When molecular oxygen is not supplied, organic substances such as raw materials, reactants or by-products are adsorbed on the surface of the catalyst, and the organic substances adsorbed on these catalysts are oxidized by oxygen in the catalyst. In this case, it is presumed that the catalyst itself is reduced because oxygen is extracted, so that the subtle oxidation state suitable for the reaction of the catalyst changes and the performance deteriorates. In order to remove such organic substances adsorbed on the catalyst, it is necessary to supply molecular oxygen, and at this time, it is preferable to carry out the reaction at a temperature of 260 ° C. or higher. Removal of the organic matter is insufficient. On the other hand, if the treatment with molecular oxygen is performed at a very high temperature, the removal of organic substances becomes easy, but it is not preferable because the catalyst itself may be thermally deteriorated due to the high-temperature treatment. The treatment is preferably performed at a temperature of 440 ° C. or lower, more preferably 4420 ° C. or lower, particularly preferably 400 ° C. or lower. Among these, it is most preferable to perform the treatment while maintaining the reaction temperature immediately before stopping the gas phase oxidation.

The amount of the molecular oxygen-containing gas introduced varies depending on the size inherent to the apparatus, and thus cannot be specified unconditionally. However, preferably, the space oxygen velocity is 200 to 3000 h ^{− with} respect to the preceding catalyst in which the molecular oxygen-containing gas is charged in the reaction tube. The amount of carbon oxide contained in the reactor outlet gas excluding the amount of carbon oxide contained in the supplied molecular oxygen-containing gas when introduced in the range of ¹ (hereinafter referred to as “reactor outlet portion carbon oxide content” “)” Is preferably 1000 ppm or less, more preferably 500 ppm or less. However, if molecular oxygen is introduced for a long period of time as will be described later, the catalyst performance is lowered. Therefore, at least before the content of carbon oxide at the outlet of the reactor reaches 0 ppm, that is, carbon oxide in the reactor outlet gas. It is necessary to stop the supply of molecular oxygen before the concentration and the carbon oxide concentration in the supplied molecular oxygen-containing gas become equal.

  As a method for detecting carbon oxide, for example, it may be analyzed by a gas concentration analyzer such as a gas chromatograph method. As an analysis method, gas is sampled even in an on-line analysis incorporated in a series of manufacturing equipment. A sampling gas may be separately introduced into the analyzer for analysis.

  In the present invention, after the molecular oxygen-containing gas is finally supplied, it is necessary to stop the supply of molecular oxygen. At that time, the supply of molecular oxygen may be stopped, and a method of completely stopping the supply gas or switching the molecular oxygen-containing gas to an inert gas is adopted.

  If molecular oxygen is not supplied for a long time or until re-operation without being stopped, the oxidation of the catalyst proceeds and the oxidation state suitable for the reaction of the catalyst changes, contrary to the reduction by the organic matter described above. It is estimated that the performance is reduced.

  There is no restriction | limiting in particular as a pre-stage catalyst used by this invention, The well-known generally used oxide catalyst can be used.

Specifically, as the pre-stage catalyst, the following general formula (I):
Mo _a Bi _b Fe _c X1 _d X2 _e X3 _f X4 _g O _x (I)
(Where Mo is molybdenum, Bi is bismuth, Fe is iron, X1 is at least one element selected from cobalt and nickel, X2 is at least one element selected from alkali metals, alkaline earth metals, boron and thallium. Element, X3 is at least one element selected from tungsten, silicon, aluminum, zirconium and titanium, X4 is at least one element selected from phosphorus, tellurium, antimony, tin, cerium, lead, niobium, manganese, arsenic and zinc The element O represents oxygen, and a, b, c, d, e, f, g and x represent the atomic ratio of Mo, Bi, Fe, A, B, C, D and O, respectively, a = 12 Where b = 0.1-10, c = 0.1-20, d = 2-20, e = 0.001-10, f = 0-30, g = 0-4, and x is each An oxide catalyst represented by (a value determined by the oxidation state of the element) can be preferably used.

Similarly, the latter catalyst is not particularly limited, and a known and commonly used oxidation catalyst can be used. Specifically, as the latter stage catalyst, the following general formula (II):
_{Mo h V i W j Y1 k} Y2 l Y3 m Y4 n O y (II)
(Where Mo is molybdenum, V is vanadium, W is tungsten, Y1 is at least one element selected from antimony, bismuth, chromium, niobium, phosphorus, lead, zinc, cobalt, nickel and tin, Y2 is copper and At least one element selected from iron, Y3 is at least one element selected from alkali metals, alkaline earth metals and thallium; Y4 is at least one selected from silicon, aluminum, titanium, zirconium, yttrium, rhodium and cerium The seed element, O represents oxygen, and h, i, j, k, l, m, n and y represent the atomic ratios of Mo, V, W, Y1, Y2, Y3, Y4 and O, respectively, h = 12, i = 2-14, j = 0-12, k = 0-5, l = 0.01-6, m = 0-5, n = 0-10, y is An oxide catalyst represented by (a value determined by the oxidation state of each element) can be preferably used.

  As a method for forming the catalyst, a conventionally well-known extrusion molding method for molding an active ingredient into a certain shape, a tableting molding method, or the like, or an active component is supported on any inert carrier having a certain shape. It can be produced by a supporting method, and the shape thereof is not particularly limited, and may be any shape such as a spherical shape, a cylindrical shape, a ring shape, and an indefinite shape. Of course, in the case of a spherical shape, it does not need to be a true sphere, and may be substantially spherical, and the same applies to a cylindrical shape and a ring shape.

  Note that the catalyst charged in the reactor does not need to be a single catalyst. For example, a plurality of types of catalysts having different activities may be used in the preceding stage catalyst, and these may be charged in the order of different activities, The part may be diluted with an inert carrier or the like. The same applies to the latter stage catalyst.

  A suitable reaction temperature for the pre-stage catalyst and the post-stage catalyst is appropriately selected depending on the reaction conditions and the like, but is usually 300 to 380 ° C. for the pre-stage catalyst, and usually 250 to 350 ° C. for the post-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 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 propylene conversion rate and acrylic acid yield were determined by the following formulas.

Propylene conversion (mol%)
= (Number of moles of reacted propylene / number of moles of supplied propylene) × 100
Acrylic acid yield (mol%)
= (Number of moles of acrylic acid produced / number of moles of supplied propylene) × 100
<Reference example>
[Preparation of catalyst 1]
While heating and stirring 2000 parts of distilled water, 500 parts of ammonium molybdate was dissolved (solution A). Separately, 137 parts of cobalt nitrate and 206 parts of nickel nitrate were dissolved in 500 parts of distilled water (Liquid B), and nitric acid was added to a solution made acidic by adding 30 parts of concentrated nitric acid (65 wt%) to 350 parts of distilled water. 38.1 parts of ferric iron and 572 parts of bismuth nitrate were dissolved (solution C). These nitrate solutions (B solution and C solution) were added dropwise to the A solution. Subsequently, 9.0 parts of borax, 1702 parts of 20 wt% silica sol, and 2.4 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, and tableted into pellets having an outer diameter of 5 mm and a length of 4 mm. Next, the obtained molded product was calcined at 470 ° C. for 6 hours in an air atmosphere to obtain a pre-stage catalyst 1. The composition of metal elements other than oxygen was as follows in terms of atomic ratio.
_{Mo 12 Bi 5 Co 2 Ni 3} Fe 0.4 Na 0.2 B 0.4 K 0.1 Si 24
[Preparation of latter catalyst 1]
While heating and stirring 3000 parts of distilled water, 525 parts of ammonium paramolybdate, 87 parts of ammonium metavanadate, and 80.3 parts of ammonium paratungstate were dissolved therein. Separately, 71.9 parts of copper nitrate were dissolved while heating and stirring 300 parts of distilled water. The two aqueous solutions obtained were mixed, and 18.1 parts of antimony trioxide was further added to obtain a suspension. This suspension was evaporated to dryness to form a cake-like solid, and the obtained solid was calcined at 390 ° C. for about 5 hours. The fired solid was pulverized to 250 μm or less to obtain catalyst powder. After the α-alumina spherical carrier having an average particle diameter of 4 mm is put into the centrifugal fluidized coating apparatus, and then the catalyst powder is put together with 15% by weight ammonium nitrate aqueous solution as a binder while passing hot air at 90 ° C. and supported on the carrier. Then, heat treatment was performed at 400 ° C. for 6 hours in an air atmosphere to obtain a rear catalyst 1. The composition of metal elements other than oxygen excluding the catalyst support was as follows in terms of atomic ratio.
Mo ₁₂ V ₃ W _1.2 Cu _1.2 Sb _0.5
[Reactor]
A reactor consisting of a SUS reaction tube having a total length of 6000 mm and an inner diameter of 25 mm and a shell for flowing a heat medium covering the SUS reaction tube was prepared in the vertical direction. A partition plate having a thickness of 50 mm that divides the shell vertically was provided at a position of 3000 mm from the bottom of the shell, and the heat medium was circulated from below to above in both the upper and lower shell spaces. The front catalyst 1, the SUS Raschig ring with an outer diameter of 8 mm, and the rear catalyst 1 were dropped in order from the upper part of the reaction tube, and filled so that the respective lengths were 2800 mm for the front catalyst, 400 mm for the Raschig ring, and 2800 mm for the rear catalyst.
[Oxidation reaction]
The temperature of the front catalyst layer (heat medium inlet temperature in the lower shell space): 330 ° C., the temperature of the rear catalyst layer (heat medium inlet temperature in the upper shell space): 265 ° C., and 5 volumes of propylene from the bottom of the reactor %, Oxygen 10% by volume, water vapor 20% by volume and nitrogen 65% by volume as a reaction raw material gas was introduced at a space velocity of 1600 h ⁻¹ (STP) with respect to the preceding catalyst, and gas phase catalytic oxidation was continued for 2000 hours. I went. The reaction results are shown in Table 1.

<Example 1>
In the reference example, the operation was stopped after the gas phase oxidation reaction was continued for 2000 hours. At that time, in stopping the gas supply to the reactor, first, the reaction raw material gas was stopped, and then the inert gas composed of 70% by volume of nitrogen and 30% by volume of water vapor was maintained at 25 L STP) was allowed to flow for about 5 minutes, and oxygen content gas consisting of 18% by volume of oxygen and 82% by volume of nitrogen was subsequently increased to 2000 ppm at the reactor outlet at a flow rate of 25 L (STP). After the gas was circulated until it was, the gas supply was stopped. After the gas supply was stopped for 48 hours, the reaction raw material gas was introduced again and the operation was started. The reaction results are shown in Table 2.
<Comparative Example 1>
In Example 1, the same procedure was performed except that the supply of gas was stopped without circulating the oxygen-containing gas after circulating the inert gas when the operation was stopped. The reaction results are shown in Table 2.
<Example 2>
In Example 1, it was performed in the same manner except that the supply of gas was stopped after flowing through the reactor until the carbon oxide content at the outlet of the reactor reached 1000 ppm. The reaction results are shown in Table 2.
<Example 3>
In Example 1, it was carried out in the same manner except that the supply of gas was stopped after flowing until the carbon dioxide content at the outlet of the reactor reached 500 ppm when the operation was stopped. The reaction results are shown in Table 2.
<Comparative example 2>
In Example 3, the same procedure was performed except that the supply was continued until the re-operation was started (48 hours) even after the reactor outlet portion carbon oxide content reached 0 ppm when the operation was stopped. The reaction results are shown in Table 2.

<Example 4>
[Preparation of gas phase oxidation catalyst]
Pre-stage catalysts 4 and 5 for producing acrolein-containing gas by gas phase catalytic oxidation of propylene-containing gas were prepared according to the method described in Example 1 of JP-A-4-217932. Similarly, post-stage catalysts 4 and 5 for producing acrylic acid by gas phase catalytic oxidation of an acrolein-containing gas were prepared according to the method described in Example 2 of JP-A-9-241209. The composition of metal elements other than oxygen excluding these catalyst supports was as follows in terms of atomic ratio.
Previous catalyst 2 Mo ₁₀ W ₂ Bi ₁ Fe ₁ Co ₄ K _0.06 Si _1.5 Average diameter 5 mm
Previous stage catalyst 3 Mo ₁₀ W ₂ Bi ₁ Fe ₁ Co ₄ K _0.06 Si _1.5 Average diameter 8 mm
Rear catalyst 2 Mo ₁₂ V ₄ W _2.5 Cu ₂ Sr _0.2 Average diameter 5 mm
_Second stage catalyst 3 Mo ₁₂ V ₄ W _2.5 Cu ₂ Sr _0.2 Average diameter 8 mm
[Reactor]
About 9,500 reaction tubes (reaction tube diameter: 25 mm, length: 6000 mm) and a fixed bed multi-tubular reactor comprising a shell for flowing a heat medium covering the reaction tube, the first catalyst 3 and the first Catalyst 2, SUS Raschig ring with outer diameter of 8 mm, rear stage catalyst 3, rear stage catalyst 2 are dropped and the respective lengths are: front stage catalyst 3: 800 mm, front stage catalyst 2: 2000 mm, Raschig ring: 400 mm, rear stage catalyst 3: 800 mm, Second stage catalyst 2: packed to 2000 mm and layer length of 800 mm. A partition plate having a thickness of 50 mm that divides the shell vertically was provided at a position of 3000 mm from the bottom of the shell, and the heat medium was circulated from below to above in both the upper and lower shell spaces.
[Oxidation reaction]
The temperature of the front catalyst layer (heat medium inlet temperature in the lower shell space): 320 ° C., the temperature of the rear catalyst layer (heat medium inlet temperature in the upper shell space): 260 ° C., and 8 volumes of propylene from the bottom of the reactor %, 15% by volume of oxygen, 10% by volume of water vapor and 67% by volume of nitrogen were introduced as a raw material gas at a space velocity of 1600 h ⁻¹ (STP) with respect to the preceding catalyst, and gas phase catalytic oxidation was performed.
[Stop and restart]
After the gas phase oxidation reaction was continued for 4000 hours under the above reaction conditions, the operation was stopped. At that time, when the gas supply to the reactor was stopped, first, the raw material gas was stopped, and then the inert gas composed of 70% by volume of nitrogen and 30% by volume of water vapor was maintained at 200 m ³ ( STP) was allowed to flow for about 15 minutes, and an oxygen-containing gas consisting of 18% by volume of oxygen and 82% by volume of nitrogen was subsequently supplied at an outlet carbon dioxide content of 500 ppm at a rate of 200 m ³ (STP) per minute. Then, the gas supply was stopped. After the gas supply was stopped for 48 hours, the raw material gas was introduced again and the operation was started. The reaction results are shown in Table 3.

Claims (2)

  Acrolein and / or acrylic acid is produced by catalytic gas phase oxidation of propylene and / or propane with molecular oxygen or a molecular oxygen-containing gas using a fixed bed reactor having a reaction tube filled with a gas phase oxidation catalyst. In the method, when the operation of the catalytic gas phase oxidation step is stopped, after the supply of the reaction raw material gas is stopped, an inert gas is supplied to the reactor, and then a molecular oxygen-containing gas is supplied, and then molecules to the reactor are supplied. A method for producing acrolein and / or acrylic acid, characterized in that the supply of gaseous oxygen is stopped.   The amount of carbon oxide contained in the gas at the outlet of the reactor excluding the amount of carbon oxide contained in the supplied molecular oxygen-containing gas when the operation of the catalytic gas phase oxidation step is stopped. 2. The method according to claim 1, wherein the supply of molecular oxygen to the reactor is stopped after supplying until the amount of oxygen exceeds 0 ppm and not more than 1000 ppm.