JP2002233759A - Pretreatment method for catalyst in acrylonitrile manufacturing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment method for a catalyst for manufacturing acrylonitrile by the ammoxidation reaction of propylene in a high yield since just after starting reaction and in a yield stable with time for a long term. SOLUTION: When manufacturing of acrylonitrile is started, a catalyst is packed into a fluidized-bed reactor and heat-treated in a particular oxygen- containing atmosphere and under a specific condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the production of acrylonitrile by the ammoxidation of propylene using a fluidized bed reactor. More specifically, the present invention relates to a method for obtaining a stable acrylonitrile yield at a high level immediately after the start of the reaction and for a long period of time by performing a catalyst pretreatment in a fluidized bed reactor at the start of acrylonitrile production.

[0002]

2. Description of the Related Art There is no specific proposal for a method of pretreating a catalyst in a reactor before starting the production of acrylonitrile by ammoxidation of propylene. As a similar technique, a heat treatment method for producing a catalyst and a heat treatment method for regenerating and activating a catalyst with reduced performance are known.

[0003] Many catalysts have been proposed for producing acrylonitrile by ammoxidizing propylene. For example, Japanese Patent Publication No. 38-17967 discloses molybdenum,
Oxide catalyst containing bismuth and iron
No. 9111 proposes an oxide catalyst containing antimony and iron, and various improvements have been proposed for these catalyst systems. Examples of these improvements include JP-A-49-101335 and JP-B-51-33888.
JP, JP-A-52-125124, JP-B-53
-18014, JP-A-57-180431, JP-B-58-38424, JP-A-59-204163.
JP, JP-B-61-43094, JP-B-61-43094
JP-A-26419, JP-A-4-118051, JP-A-7-289901, JP-A-7-328441
And Japanese Patent Application Laid-Open No. H10-43595 have been proposed. Specific methods for producing these catalysts are individually different, but are produced through the following steps. A step of preparing a raw material slurry comprising various metal components as catalyst constituents, a catalyst carrier component such as silica, a step of spray-drying the raw material slurry to obtain a spherical powder, a step of drying the powder, and a step of drying. It consists of a step of finally firing the powder. The final calcination step is usually performed at a high temperature in an air atmosphere at 500 to 950 ° C. for 1 to 50 hours, although the optimum conditions vary depending on the catalyst.

[0004] As another similar technique, there is a method for regenerating a catalyst whose performance has deteriorated due to long-term use. Methods for regenerating the catalyst used in the propylene ammoxidation reaction include firing the catalyst at a high temperature, adding an active ingredient in the catalyst, adding a new component to the catalyst, and a combination of these methods. is there. As an example of a specific proposal, JP-A-54-62193 discloses a method in which a deteriorated iron-antimony catalyst is calcined in a temperature range of 600 ° C. to 950 ° C., and JP-B-63-33903 discloses a deteriorated molybdenum catalyst. Method for calcining the contained catalyst, Tokiko Sho 55-
JP-A-49541, JP-A-7-289901 and JP-A-11-319562 disclose a method of adding molybdenum to a deteriorated molybdenum-containing catalyst and finally calcining it. In each of these, the catalyst is finally calcined at a high temperature of 500 to 1000 ° C.

[0005] According to the above prior art, the produced or regenerated catalyst is stored in a state of being packed in a packaging material and packed in a drum or the like, or directly filled in a metal container such as a hopper. The storage period can be unconditional, but can extend for as long as several months. When such a catalyst was charged into a reactor and started to be used for acrylonitrile production, the acrylonitrile yield was several months after the start of the reaction.
When the value is lower than expected or severe,
May stay at low levels over time. Conventionally, there is no disclosure about solving such a problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a catalyst for producing acrylonitrile by ammoxidizing propylene in a fluidized bed reactor to obtain a high acrylonitrile yield which is high immediately after the start of the reaction and is stable over time. It proposes a preprocessing method.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the problems, and as a result, when starting the production of acrylonitrile by the ammoxidation of propylene using a fluidized bed reactor, the fluidization was carried out prior to the start of the reaction. By carrying out catalyst pretreatment under specific conditions in a bed reactor, a high acrylonitrile yield can be obtained immediately after the start of the reaction, and an industrially easy-to-implement method capable of obtaining stable reaction results over a long period of time has been found in the present invention. Reached.

That is, according to the present invention, when starting the production of acrylonitrile by ammoxidation of propylene using a fluidized bed reactor, the fluidized bed reactor is filled with a catalyst and a gas atmosphere having an oxygen concentration of 5 to 30%. 30 catalyst
The gist of the present invention is a catalyst pretreatment method in which a heat treatment is performed in a temperature range of 0 ° C. to 450 ° C. for 1 hour to 100 hours.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention is characterized in that a pretreatment of heating the catalyst under specific conditions in a fluidized bed reactor before starting the ammoxidation reaction, that is, before supplying the raw material, is performed. Usually, although the catalyst is subjected to a high-temperature baking treatment in the final step of the production or the regeneration / activation treatment, it is unknown why the remarkable effect is exhibited by the relatively low-temperature pretreatment of the present invention. However, it is considered that the catalyst was poisoned by the influence of moisture and atmospheric gas during storage, and poisoning was removed by the method of the present invention.

The heat treatment in the present invention is performed in an oxygen-containing atmosphere having an oxygen concentration of 5 to 30% under a gas flow. If the oxygen concentration is too low or too high, the manifestation of the effect is insufficient.
Although the use of air is convenient as the oxygen-containing gas, oxygen or air can be diluted with an inert gas, or oxygen-enriched air can be used.

The heat treatment temperature in the present invention is 300 to 450 ° C. If the temperature is lower than 300 ° C., the effect is insufficient, and if the temperature is higher than 450 ° C., the effect is not particularly accelerated, and it is difficult to carry out the reaction in a usual reactor, and it is not practical. The heat treatment is performed for 1 hour to 100 hours. If the heating time is less than 1 hour, the effect is insufficient.
If the heating is performed for a long time of 00 hours or more, the effect is not increased, and adverse effects such as a decrease in the catalyst surface area may occur. The heat treatment method is not particularly limited, and includes a method of heating with a heater on the outer wall of the reactor, a method of introducing a heated gas into the reactor through a heat exchanger, and a method of using high-temperature combustion gas containing oxygen-containing gas. Various methods such as a method in which a high-temperature gas mixed with an inert gas or the like is directly introduced into a reactor, and a method in which a combustible gas such as an oxygen-containing gas and ammonia is introduced into a reactor and a combustible gas is burned in a catalyst layer. Can be selected arbitrarily.

In the method of the present invention, in order to carry out the heat treatment efficiently, it is effective to consider the gas superficial velocity.
Preferably, it is in the range of 0.1 to 1 m / s. If the gas superficial velocity is 0.1 m / s or less, the fluidization of the catalyst becomes poor in an industrial scale apparatus, so that a sufficient heat treatment effect may not be obtained. Further, when the gas flow velocity is excessive, the amount of the catalyst entrained and transported by the gas increases, so that the scattering loss of the catalyst tends to increase. The pressure in the heat treatment is not particularly limited, but is from atmospheric pressure to 2 × 10 ⁵ Pa
Is preferably used.

The catalyst used in the method of the present invention is not particularly limited, but is particularly effective for a catalyst system containing iron and antimony, or molybdenum and bismuth as essential components. Specific examples of these catalyst systems include those described in the conventional literature described in the section of "Prior Art".

In order to sufficiently exhibit the effects of the present invention,
As soon as possible following the heat treatment, the raw material propylene,
It is desirable to start the reaction by feeding in ammonia.
As a production method after the start of the reaction, a normal method conventionally used by the business operator may be employed. At the start of the reaction, it is important, especially for safety reasons, to reduce the oxygen concentration sufficiently to prevent detonation at the inlet and outlet of the reactor, specifically US Pat.
No. 6,228, and the conventional method disclosed in Keizo Konogi, "Process System Design (1)," pp. 68-71 (Maruzen 1974) can be used.

[0015]

EXAMPLES The present invention will be described more specifically with reference to the following Examples, but the present invention is not limited to these Examples. The propylene conversion and acrylonitrile yield in the examples are defined by the following equations. Propylene conversion (%) = (moles of propylene reacted) / (moles of propylene supplied) × 100 Acrylonitrile yield (%) = (moles of acrylonitrile produced) / (moles of propylene supplied) × 10
0

(Embodiment 1) Japanese Patent Application Laid-Open No. 4-118051
The empirical formula shown in Example 1 of the report is Fe₁₀Sb ₁₀M
o_8.5Bi_1.5K_0.2Ni_5.0B_0.75P
_0.55O_{75.2 5}(SiO₂)₄₅Open the catalyst that is
Manufactured in the manner indicated. This catalyst is made of polyethylene
Stored in a bag in an air atmosphere at room temperature for 3 months
Then, 2.93 kg of this catalyst was collected and 3 inches high.
A 2 m stainless steel fluidized bed reactor was charged. Heat exchanger
Introduce air heated to about 400 ° C into the catalyst layer at
The catalyst is heated by an electric heater provided on the outer wall of the reactor.
The layers were heated. At this time, the temperature of the catalyst layer reaches 300 ° C.
Later, the gas superficial velocity was increased to about 0.15 to 0.18 m / s.
While maintaining the heat treatment for 2 hours, raise the temperature to 400 ° C.
Was. After the temperature of the catalyst layer reaches 400 ° C, the propylene
And ammonia were supplied. The reaction conditions were a temperature of 430 ° C,
The molar ratio is air: ammonia: propylene = 9.5: 1.
2: 1.0, apparent contact time 3.5 seconds and pressure
The reactor outlet was adjusted to atmospheric pressure. The reaction score is
10 hours after the start of the reaction,
5%, acrylonitrile yield 85.0%, from the start of the reaction
After 700 hours, the propylene conversion rate was 98.0%,
The acrylonitrile yield was 84.8%.

Example 2 Using the same catalyst and the same reactor as in Example 1, the heat treatment method for the catalyst layer was carried out from 300 ° C. to 4 ° C.
The temperature was raised to 00 ° C. for 1 hour at a gas superficial velocity of about 0.15 to 0.18 m / s, and then at 400 ° C., 80 vol. %, Water vapor 20 vol. % Of the mixed gas was passed at a gas superficial velocity of 0.18 m / s, and an ammoxidation reaction of propylene was carried out in the same manner as in Example 1. The reaction results were as follows: 10 hours after the start of the reaction, the propylene conversion rate was 98.3%, and the acrylonitrile yield was 85.50%.
The conversion of propylene was 97.7% and the yield of acrylonitrile was 84.9% after 700 hours from the start of the reaction.

(Comparative Example 1) Using the same catalyst and the same reactor as in Example 1, the heat treatment method for the catalyst layer was carried out from 300 ° C to 40 ° C.
Ammonia oxidation of propylene was carried out in the same manner as in Example 1 except that the temperature was raised to 0 ° C. in 0.5 hours. The reaction results were as follows: 10 hours after the start of the reaction, a propylene conversion rate of 96.5%, an acrylonitrile yield of 83.0%, and 700 hours after the start of the reaction, a propylene conversion rate of 96.
8% and acrylonitrile yield was 83.5%.

(Comparative Example 2) Using the same catalyst and the same reactor as in Example 1, the heat treatment method for the catalyst layer was carried out at a temperature of 300 ° C to 400 ° C and a gas superficial velocity of about 0.05 to 0.0.
Example 1 except that the temperature was raised in 2 hours while maintaining at 6 m / s.
The propylene ammoxidation reaction was carried out in the same manner as described above.
The reaction results were as follows: 10 hours after the start of the reaction, the conversion of propylene was 97.0%, and the yield of acrylonitrile was 83.3.
%, 700 hours after the start of the reaction, the propylene conversion rate was 97.8%, and the acrylonitrile yield was 84.2%.

[0020]

According to the present invention, a high acrylonitrile yield can be obtained immediately after the start of the reaction, and a stable acrylonitrile yield can be easily achieved over a long period of time.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Yamaguchi 10-1 Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Chemical Development Laboratory, Mitsubishi Rayon Co., Ltd. 4G069 AA08 BB06B BC03B BC25A BC25B BC26A BC26B BC59A BC59B BC66A BC66B BC68B BD03B BD05B BD07B CB53 DA05 FB40 FB77 FC07 FC08 GA06 4H006 AC54 BA02 BA13 BA14 BA19 BA21 BA30 BA31 BA33 BA35 BA81 BE14 BE30 4H039 CA70 CL50

Claims (3)

[Claims] When starting the production of acrylonitrile by ammoxidation of propylene using a fluidized bed reactor, the fluidized bed reactor is filled with a catalyst and the catalyst is placed in a gas atmosphere having an oxygen concentration of 5 to 30%. ° C to 450
A catalyst pretreatment method in which a heat treatment is performed at a temperature of 1 ° C for 1 hour to 100 hours. 2. The gas superficial velocity of the reactor is 0.1 to 1 m.
The catalyst pretreatment method according to claim 1, wherein the heat treatment is performed while the fluidization is performed while maintaining the pressure in the range of / s. 3. The method according to claim 1, wherein the catalyst contains iron and antimony, or molybdenum and bismuth as essential components.