JP2005193172A - Fluidized reaction method and method for producing acrylonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the fluidity of catalysts within a reactor by supplying a small amount of unused catalysts so as to maintain a high production efficiency of acrylonitrile. <P>SOLUTION: The method for producing acrylonitrile comprises, in a method for conducting fluidized reaction using a fluidized bed reactor, for example, supplying raw material gas containing hydrocarbon, ammonia, and oxygen to a reactor 1 and collecting an acrylonitrile component in gas that is generated by vapor-phase oxidation reaction in the presence of fluid granular catalysts within the reactor 1. Part of the granular catalysts in a fluidized bed 2 within the reactor 1 are extracted, the extracts are classified to obtain fine granular catalysts with a grain diameter between 20 and 44 μm, and then the fine granular catalysts are returned to the fluidized bed 2. At the same time, unused granular catalysts are supplied in a small amount to adjust the proportion of the amount of the fine granular catalysts in the whole granular catalysts, thereby producing acrylonitrile. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fluidized reaction method, and more specifically, a fluidized bed reaction method having technical characteristics in a fluidized bed of a catalyst, and production of acrylonitrile in which a raw material gas is subjected to a gas phase oxidation reaction in the presence of a granular catalyst in the fluidized bed reactor. Regarding the method.

  In recent years, acrylonitrile has been produced on a large scale by a gas phase oxidation reaction of propane or propylene and ammonia, and as a typical production method thereof, at the bottom of a fluidized bed reactor containing a finely divided fluidized bed type catalyst, Propylene or propylene, ammonia, and oxygen-containing gas such as air is supplied, and the acrylonitrile is formed by continuing the oxidation reaction while removing the heat of reaction by passing a cooling medium such as water through a cooling pipe passing through the reactor. Manufacturing methods are known.

  In this method, the oxidation reaction gas containing acrylonitrile distilled out from the reactor contains unreacted ammonia, oxygen, nitrogen, propane, and propylene in addition to acrylic acid, acetic acid, hydrocyanic acid, acetonitrile, acrolein, and the like.

  This oxidation reaction gas is washed with an aqueous sulfuric acid solution and cooled, and unreacted ammonia is neutralized and removed as an aqueous ammonium sulfate solution. Thereafter, products such as acrylonitrile, hydrocyanic acid, acetonitrile, and acrolein are absorbed into water by an absorption tower. Alternatively, they are dissolved and separated from the oxidation reaction gas.

  From the aqueous solution in which acrylonitrile or the like is dissolved, acrylonitrile is recovered by appropriately combining means such as stripping or distillation in a recovery tower.

  Acrylonitrile recovered at this time is crude acrylonitrile, which is further sent to a purification system for separation of light-boiling components including hydrocyanic acid, dehydration, and separation of high-boiling components. can get.

  As shown in FIG. 1, the reactor 1 in such a continuous production process of acrylonitrile contains a feed fine powder fluidity catalyst called a fluidized bed 2, and disperses air from the bottom (not shown). The raw material propylene and ammonia (indicated by arrows in the figure) are respectively supplied above.

  The reactor 1 includes a cooling pipe 3 that collects the generated heat of reaction as steam, and a catalyst return pipe that returns the cyclones 4, 5, and 6 and catalyst particles separated thereby by a large particle size and specific gravity to the lower part of the reactor. (Dipleg) 7, 8, 9

  The fluid catalyst constituting the fluidized bed 2 in the reactor 1 is a finely divided catalyst containing elements such as phosphorus, molybdenum, bismuth, iron, antimony, etc., and the physical properties of the catalyst (particle density, particle size) Distribution, strength, etc.) to give the required fluidity.

Typical examples of the physical properties of the finely divided fluid catalyst are those having a particle density of 1 to 2 g / cm ³ and an average particle diameter of about 50 to 80 μm. And, in order to have good fluidity as a catalyst, the presence of so-called “good fraction” of 44 μm or less is indispensable, and the required content of such fine particles is 20 to 60%. Desirably, it is 20 to 50% (Non-Patent Document 1), and the acrylonitrile (AN) yield increases as the fine particle concentration increases (Non-Patent Document 2).

  In the continuous production process of acrylonitrile, the catalyst that jumps out from the fluidized bed 2 into the space in the reactor 1 is collected by the cyclones 4, 5, and 6 and flows from the catalyst return pipes (diplegs) 7, 8, and 9 (catalyst). Returned to Tier 2.

  By the way, when acrylonitrile is continuously produced in such a process, the activity of the catalyst decreases with time, and the amount of catalyst gradually decreases by the amount of fine particles that could not be collected. Further, among the catalyst lost in this manner, the fluidized state is also deteriorated by reducing the fine particles having a particle diameter of 44 μm or less.

  Conventionally, in order to avoid such a decrease in the activity of the catalyst and efficiently perform continuous production of acrylonitrile, a part of the catalyst is extracted from the reactor, and the reactor is filled with a new unused catalyst. I was trying to do it.

“Chemical Industry”, published by Kagaku Kogyosha in 1984, Vol. 48, No. 11, p.73-74 "AI HC Symposium Series" (A.I.Ch.E. Symposium Series), US, ICH ISS, Volume 184, No. 262, p.68-73

  However, in the above conventional acrylonitrile production method, it is necessary to replenish a fairly large amount of a new catalyst so as to supplement the fine particles having a particle diameter of 44 μm or less that have decreased over time and maintain the required fluidity. In order to improve the fluidity of the catalyst, even if the original activity of the catalyst is not deteriorated, it will be replaced with an expensive unused (new) catalyst, and the replenishment amount is wasteful. It was.

  Therefore, the object of the present invention is to improve the fluidity of the catalyst in the reactor by replenishing a relatively small amount of unused catalyst so as to solve the above-mentioned problems, thereby improving the production efficiency of acrylonitrile. To keep it high.

  In order to solve the above problems, in the present invention, in a method of performing a fluid reaction using a fluidized bed reactor, a part of the granular catalyst in the fluidized bed reactor is extracted, and the extracted catalyst is classified. The fine particle size catalyst obtained is returned to the fluidized bed reactor and the amount of fine particle size catalyst in the whole granular catalyst is adjusted by replenishing unused granular catalyst. It was.

  According to the fluidized reaction method of the present invention configured as described above, the fine particle size catalyst obtained by classifying the particulate catalyst extracted from the fluidized bed in the reactor is returned to the fluidized bed in the reactor. Therefore, the fine particle diameter catalyst particularly useful for improving fluidity in the fluidized bed can be reused without being discarded along with the extraction, and the replenishment amount of the unused new granular catalyst can be reduced correspondingly.

  Alternatively, in order to solve the above problem, a raw material gas containing hydrocarbon, ammonia and oxygen is supplied to a fluidized bed reactor, and is generated by a gas phase oxidation reaction in the presence of a granular catalyst in the fluidized bed reactor. In the method for producing acrylonitrile for recovering the acrylonitrile component in the gas, a fine particle diameter catalyst having a particle diameter of 20 to 44 μm obtained by extracting a part of the granular catalyst in the fluidized bed reactor and classifying the extracted catalyst. While returning to the fluidized bed reactor, an unused granular catalyst is replenished to adjust the proportion of the fine particle diameter catalyst amount in the entire granular catalyst, thereby producing an acrylonitrile production method.

  According to the acrylonitrile production method of the present invention configured as described above, a fine particle size catalyst having a particle size of 20 to 44 μm obtained by classifying the catalyst extracted from the fluidized bed in the reactor is provided in the reactor. Since it is returned to the fluidized bed, the fine particle diameter catalyst that is particularly useful for improving fluidity in the fluidized bed is reused without being discarded along with the extraction, and the replenishment amount of the unused granular catalyst can be reduced accordingly.

  That is, even if a relatively expensive unused granular catalyst is not replenished in a large amount, a fine particle size catalyst classified from the catalyst extracted from the fluidized bed is used, and a relatively small amount of the unused catalyst is mixed and replenished. This makes it possible to increase the proportion of fine particle size catalyst having a particle size of 20 to 44 μm and replenish it, thereby saving the amount of new catalyst added and reducing the cost, and the flow of the catalyst in the reactor. Can improve sex.

  Moreover, in order to solve the above-mentioned problem reliably, it is preferable to adjust the ratio of the fine particle size catalyst to the whole granular catalyst in the range of 20 to 60% by weight, desirably 20 to 50% by weight.

  In this way, the fluidity of the catalyst in the reactor is reliably improved, the activity of the catalyst in the entire fluidized bed becomes uniform, the efficiency of the catalyst is increased, and as a result, the production efficiency of acrylonitrile can be maintained high.

  As described above, the present invention classifies the catalyst extracted from the fluidized bed reactor in the production of acrylonitrile, returns the fine particle size catalyst having a predetermined particle size to the fluidized bed reactor, and uses the unused granular catalyst. Since the proportion of the fine particle size catalyst amount in the total catalyst is adjusted with the replenishment of the catalyst, the fluidity of the catalyst in the reactor can be improved by supplying as little new (unused) catalyst as possible. There is an advantage that the production method of acrylonitrile can maintain the efficiency as high as possible.

  In the method for producing acrylonitrile of the present invention, a raw material gas containing hydrocarbon, ammonia and an oxygen-containing gas is supplied to a reactor, and an oxidation reaction using an ammonium oxidation catalyst in a fluidized bed is performed in the reactor. The acrylonitrile component is recovered from the gas produced in the above step and purified.

  The reactor used in the present invention is a fluidized bed reactor, and the hydrocarbon supplied to the reactor is a gaseous hydrocarbon. For example, olefin such as propylene, propane, or a gas mixture thereof is used.

  The source gas containing oxygen separately supplied to the reactor may contain a predetermined concentration of oxygen, and the remaining component may be composed of a mixed gas composed of an inert gas. Usually, air is used. ing.

As the catalyst used in the gas phase oxidation reaction for oxidizing ammonium, for example, a well-known catalyst containing elements such as phosphorus, molybdenum, iron, antimony and the like can be used. Generally, the average particle size is 1 to 2 g / cm ^3. The diameter is about 50 to 80 μm. This also contains a fine particle size catalyst with a particle size of 20-44 μm which makes fluidity good, and the preferred content of such fine particles is 20-60% by weight, preferably 20-50% by weight. .

  Thus, in the manufacturing method of acrylonitrile of the embodiment shown in FIG. 1, olefin such as propylene or propane, ammonia and air is supplied to the reactor 1 filled with the fine particle catalyst and reacted at a high temperature to produce acrylonitrile. I am letting.

  The function of the fluidized bed 2 of the catalyst in the reactor 1 will be described in detail with reference to FIG. 1. A fluidized bed is formed in the reactor 1 by containing the supplied fine powder fluid catalyst, and dispersed at the bottom. Air (indicated by an arrow in the figure) is supplied through a vessel (not shown), and above that, raw material propane or propylene and ammonia (in the figure) through a gas distributor (not shown). Are indicated by arrows).

  The reactor 1 is provided with a heat exchanger cooling pipe 3 for recovering reaction heat as steam using water as a heat medium, a reaction product gas collection pipe 10, a horizontal plate 11, an inert gas supply pipe 12 and the like. Is provided. Further, catalyst return pipes (diplegs) 7, 8, 9 are provided for returning particles separated by the three-stage cyclones 4, 5, 6 and having a large particle size and specific gravity to the lower part of the reactor, and further a third-stage cyclone. The reaction gas that has passed through 6 is extracted from the collection tube 10 and sent to the next step.

  Such a reactor 1 is supplied with an unused catalyst (new catalyst), and a partly extracted catalyst is classified by a classifier (wind classifier) 19 to obtain a fine particle size of 20 to 44 μm. The concentration of the particle size catalyst was increased and returned to the reactor 1, and the catalyst having a large particle size from which the fine particle size catalyst was removed was discharged.

  Explaining the adjustment relationship of the amount of catalyst in and out of the reactor 1, a catalyst having an amount corresponding to the weight of the particulate catalyst partially extracted from the reactor 1 is recovered by increasing the proportion of the fine particle size catalyst. It is supplemented by the total amount of the catalyst weight and the replenishment weight of the unused granular catalyst.

  For example, the weight of the particulate catalyst partially extracted from the fluidized bed reactor is A, and the weight of the recovered catalyst obtained by classifying the extracted catalyst to increase the proportion of fine particle size catalyst having a particle size of 20 to 44 μm is a. Further, when the replenishment weight of the unused granular catalyst is B, the adjustment is made to satisfy the relationship of A = a + B.

  In this way, the amount corresponding to the weight of the particulate catalyst partially extracted from the fluidized bed reactor is the total amount of the recovered catalyst weight in which the fine particle diameter catalyst ratio is increased and the replenishment weight of the unused particulate catalyst. Therefore, there is no change in the total catalyst amount, and the replenishment weight of the unused granular catalyst can be minimized, that is, the consumption of expensive new catalyst can be reduced, and the fluidity of the catalyst can be improved efficiently.

  Acrylonitrile was produced in the fluidized bed (bed) reactor shown in FIG. That is, 7.8 kg / hr of propylene, 3.5 kg / hr of ammonia and 54 kg / hr of air were supplied to the reactor 1 at each flow rate, and the proportion of fine particle size catalyst having a particle size of 20 to 44 μm was contained in the reactor 1. Contained 37% by weight of the catalyst and an ammonia oxidation reaction was carried out.

  The reactor 1 is connected to a supply path for replenishing an unused catalyst (the same new catalyst as described above), and a partly extracted catalyst is classified by a classifier 19 such as wind power, so that the particle size is 20 to 44 μm. The concentration of the fine particle size catalyst was increased to 62% by weight and returned to the reactor 1. In this case, the catalyst replenishment amount is 0% of the unused catalyst and classified catalyst (with a fine particle size catalyst content of 62% by weight with a particle size of 20 to 44 μm extracted and classified during use) 0 The ratio was 1 kg. When this operation was performed once a week, the concentration of the fine particle size catalyst in the reactor 1 could be adjusted to about 31%.

  In such a production method in Example 1, a fine particle size catalyst having a particle size of 20 to 44 μm is mixed by mixing an unused catalyst with a fine particle size catalyst classified from the catalyst extracted from the fluidized bed of the reactor 1. The ratio was increased and replenished to the fluidized bed, but the fluidity of the catalyst in the reactor was always kept good, the acrylonitrile production efficiency was good, and the amount of new catalyst added was saved, resulting in low cost. Met.

  In Example 1, acrylonitrile was produced in exactly the same manner except that the ratio of the classification catalyst was 0.3 kg. That is, the catalyst replenishment amount was set to a ratio of 0.3 kg of a classified catalyst having a fine particle size catalyst content concentration of 62% by weight and a particle size of 20 to 44 μm classified with respect to 0.6 kg of the unused catalyst. In this way, the concentration of the fine particle size catalyst in the reactor is adjusted to about 37%, the fluidity of the catalyst in the reactor is always kept good, and the production efficiency of acrylonitrile can be kept high. It was.

  In Example 1, acrylonitrile was produced in exactly the same manner except that the classification catalyst was 0.6 kg. That is, the catalyst replenishment amount was set to a ratio of 0.6 kg of a classified catalyst having a fine particle diameter catalyst content of 62% by weight with a particle diameter of 20 to 44 μm classified with respect to 0.6 kg of the unused catalyst. In this way, the concentration of the fine particle size catalyst in the reactor was adjusted to about 42%, and the fluidity of the catalyst in the reactor was always kept good.

Comparative Example 1

  In Example 1, acrylonitrile was produced in exactly the same manner except that the replenishment amount of the unused catalyst was 1.8 kg and the replenishment amount of the classified catalyst was not (0 kg).

  In this way, the concentration of the fine particle size catalyst in the reactor is adjusted to about 35%, and the replenishment amount of the new catalyst at that time is 3 to 6 times larger than those in Examples 1 and 2 described above. Therefore, a great manufacturing cost is required, and this makes it impossible to maintain the production efficiency of acrylonitrile at a low cost.

Schematic which shows the reactor in the manufacturing process of the acrylonitrile of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2 Fluidized bed 3 Cooling pipes 4, 5, 6 Cyclone 7, 8, 9 Catalyst return pipe 10 Collection pipe 11 Horizontal plate 12 Inert gas supply pipe

Claims (3)

  In a method of performing a fluid reaction using a fluidized bed reactor, a fine particle size catalyst obtained by extracting a part of the particulate catalyst in the fluidized bed reactor and classifying the extracted catalyst is placed in the fluidized bed reactor. A fluid reaction method characterized by adjusting the ratio of the amount of fine particle size catalyst in the whole granular catalyst by replenishing unused granular catalyst while returning. Manufacture of acrylonitrile by supplying raw material gas containing hydrocarbon, ammonia and oxygen to fluidized bed reactor and recovering acrylonitrile components in gas produced by gas phase oxidation reaction in the presence of particulate catalyst in this fluidized bed reactor In the method
A part of the granular catalyst in the fluidized bed reactor is withdrawn, and a fine particle size catalyst having a particle size of 20 to 44 μm obtained by classifying the extracted catalyst is returned to the fluidized bed reactor, and is unused. A method for producing acrylonitrile, comprising replenishing a granular catalyst and adjusting a proportion of a fine particle diameter catalyst amount in the entire granular catalyst.   The manufacturing method of the acrylonitrile of Claim 2 which adjusts the ratio of the fine particle diameter catalyst to the whole granular catalyst in the range of 20 to 60 weight%.

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