JP2000038358A - Production of acrolein and acrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an acrolein and acrylic acid in high yield in a long-term stability while effectively restraining any side reaction by subjecting a specific propylene to vapor-phase oxidation with a molecular oxide-containing gas in the presence of oxidation catalyst. SOLUTION: This method is conducted by using a propylene wherein the content of 2-5C unsaturated hydrocarbon (e.g. ethylene) except propylene is <=500, pref. <=450, more pref. 300, still more pref. 200 wt. ppm and the total content of a 2-5C diene (e.g. butadiene) and acetylene (methylacetylene) is <=200, pref, <=150, more pref. <=100, yet more pref. <=50 ppm, and by subjecting the above propylene to vapor-oxidation with (B) a molecular oxide-containing gas in the presence of oxidation catalyst, thus obtaining an acrolein and acrylic acid. The pure content of propylene in the component A is pref. >=90%, pref., >=92%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a process for producing acrolein and acrylic acid, and more particularly to a method for producing acrolein and acrylic acid by catalytic gas-phase oxidation of propylene with a molecular oxygen-containing gas. Acrolein and acrylic acid are stably produced in a high yield for a long time by effectively suppressing the formation of various by-products such as aldehydes, carboxylic acids, high boiling compounds and tar-like substances without loss. And a method for producing the same.

[0002]

2. Description of the Related Art The production of acrolein and acrylic acid by catalytic gas-phase oxidation of propylene with a molecular oxygen-containing gas is widely industrially performed. Generally,
Acrylic acid is produced by a two-step reaction consisting of a first step in which propylene is gas-phase oxidized with a molecular oxygen-containing gas to produce mainly acrolein and a second step in which a reaction gas containing this acrolein is further oxidized to produce acrylic acid. ing.

[0003] However, in the first step of oxidizing propylene with a molecular oxygen-containing gas, a side reaction occurs in addition to a main reaction for producing acrolein, and organic acids such as terephthalic acid and maleic acid, high boiling compounds, and tar-like compounds. Compounds and the like are produced. As a result, these by-products contaminate the reactor and, in severe cases, deposits such as carbides are formed, which increases the pressure loss and clogs the pipes, making it difficult to operate normally and reducing product quality. Problems such as reduction occur. In addition, the provision of purification means for removing these by-products increases the equipment cost,
Incurs manufacturing costs. Further, a post-reaction by a highly reactive compound such as acrolein also occurs.

Conventionally, in order to suppress these side reactions,
Rapidly cooling the outlet gas of the reactor in the previous step to suppress the occurrence of side reactions, or maintaining the temperature of the outlet gas of the reactor at a certain temperature or higher to prevent contamination of the equipment due to precipitation of high boiling compounds and tar-like compounds. An operation has been performed to suppress this (see JP-A-49-132,007).

[0005] However, the above operation is not economically advantageous because it requires equipment for the operation, requires a large amount of energy for cooling or warming, and increases the manufacturing cost. That was enough. In particular, it cannot be said that sufficient effects have been obtained with respect to contamination of the apparatus by organic acids, high boiling compounds, tar compounds, etc., precipitation of carbides, and deterioration of product quality.

Further, a method of limiting the amount of an organic compound such as an organic acid in reusing a reaction product gas as a part of a raw material gas has been proposed (see Japanese Patent Application Laid-Open No. 52-108,917). ing. However, nothing is mentioned here about the quality of the raw material propylene gas.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to produce acrolein and acrylic acid by catalytic gas-phase oxidation of propylene with a molecular oxygen-containing gas. Effectively suppresses side reactions such as the formation of tar-like compounds, the precipitation of carbides, and the deterioration of product quality, and provides a high yield of acrolein and acrylic acid from propylene, and stably for a long period of time. It is to provide a manufacturing method.

For example, in a process for producing acrylic acid from propylene by catalytic gas-phase oxidation with a molecular oxygen-containing gas by a two-step reaction, an organic acid as described above,
Effectively suppresses side reactions that cause the formation of high-boiling compounds and tar-like compounds, the precipitation of carbides, and the deterioration of product quality, and mainly produces acrolein from propylene in high yield, and ultimately acrylic acid. Is to provide a method for producing the compound in a high yield and stably for a long period of time.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have conducted research to solve the problems in producing acrolein and acrylic acid by the above-described catalytic gas phase oxidation of propylene with a molecular oxygen-containing gas. As a result, the following findings were obtained.

(1) an organic acid formed by a side reaction,
High-boiling compounds, tar-like compounds, and the like are formed regardless of the reaction conditions, the activity of the catalyst, and the selectivity of acrolein formation.

(2) The amount of its production is extremely small as compared with the main products, acrolein and acrylic acid, but it is a serious obstacle to stable operation for a long period of time.

(3) The amount of production is more affected by impurities contained in the starting propylene and the amount thereof than the performance of the catalyst.

(4) The presence of unsaturated compounds other than propylene greatly affects catalyst performance and the amount of by-products produced.

(5) The higher the degree of unsaturation of impurities in propylene or the higher the basicity, the greater the effect on catalyst performance and the amount of by-products.

The present inventors have further studied and found that the raw material propylene has 2 to 5 carbon atoms other than propylene.
It has been found that setting the content of unsaturated hydrocarbons to 500 ppm (weight) or less can effectively suppress side reactions and solve the above problems, and based on this finding, completed the present invention.

That is, the present invention relates to a method for producing acrolein and acrylic acid by catalytically oxidizing propylene with a molecular oxygen-containing gas in the presence of an oxidation catalyst to produce acrolein and acrylic acid. This is a method for producing acrolein and acrylic acid, wherein the content of saturated hydrocarbons (excluding propylene) is 500 ppm (weight) or less.

The present invention is also directed to a first step in which propylene is catalytically oxidized in the presence of an oxidation catalyst with a molecular oxygen-containing gas to produce acrolein, and the acrolein-containing reaction gas is converted to a gas phase in the presence of an oxidation catalyst. In a method for producing acrylic acid by a two-step reaction comprising a latter step of oxidizing to produce acrylic acid, an unsaturated hydrocarbon having 2 to 5 carbon atoms in a propylene raw material (excluding propylene)
This is a method for producing acrylic acid, wherein the content is 500 ppm (weight) or less.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The feature of the present invention is that the raw material propylene contains an unsaturated hydrocarbon having 2 to 5 carbon atoms excluding propylene (hereinafter referred to simply as "an unsaturated hydrocarbon having 2 to 5 carbon atoms"). The point is to use those having an amount of 500 ppm (weight ppm: the same applies hereinafter) or less. Among them, the content of unsaturated hydrocarbon having 2 to 5 carbon atoms is 450 ppm or less,
Preferably not more than 300 ppm, particularly preferably 200p
pm or less are preferably used.

Further, in the present invention, the compound having 2 to 5 carbon atoms is used.
The content of unsaturated hydrocarbon of 500 ppm or less, preferably 450 ppm, more preferably 300 ppm or less,
It is particularly preferably at most 200 ppm, and the total content of dienes and acetylenes having 2 to 5 carbon atoms is at most 200 ppm, preferably at most 150 ppm, more preferably at most 100 ppm, particularly preferably at least 50 ppm.
Propylene below pm is preferably used. Therefore, as an example of a suitable raw material propylene, carbon number 2 ~
And the total content of dienes and acetylenes having 2 to 5 carbon atoms is 100 ppm or less, particularly 50 ppm or less.

Typical examples of the above-mentioned dienes include butadiene and the like, and typical examples of the acetylenes include methylacetylene. Other typical examples of the unsaturated hydrocarbon having 2 to 5 carbon atoms include ethylene, butylene, and isobutylene.

The largest impurity in the raw material propylene is a saturated hydrocarbon such as propane. However, the saturated hydrocarbon has low reactivity with the catalyst and has little effect on the performance and life of the catalyst. There is no particular limitation on the hydrocarbon content. On the other hand, unsaturated hydrocarbons have high reactivity with the catalyst and cause side reactions to produce undesired products as by-products. In addition, it not only lowers the catalytic activity to lower the yield of acrolein or acrylic acid, but also causes the catalyst life to be impaired. In addition, by-products contribute to the occurrence of post-reactions, fouling and clogging of equipment. For this reason, the concentration of the unsaturated hydrocarbon in the raw propylene must be severely limited as described above.

The raw material propylene contains, in addition to the above-mentioned saturated or unsaturated hydrocarbons, non-volatile residues and sulfur, etc., and these impurities may cause a decrease in the performance of the propylene evaporator or equipment. May cause corrosion. For this reason,
Non-volatile residue and sulfur content are 100 pp each
m (weight) or less, preferably 50 ppm (weight) or less.

As the raw material propylene, any propylene can be used as long as the content of unsaturated hydrocarbon is within the above range. For example, propylene produced by a steam cracking method such as naphtha, a dehydrogenation or oxidative dehydrogenation method of propane, or the like can be used. There is no particular limitation on the method of adjusting the content of the unsaturated hydrocarbon in the propylene to the above range.For example, in the case of a steam cracking method such as naphtha, a small amount of water separated by a low-temperature fractionation method is added. Acetylenes may be removed by selective hydrogenation. Moreover, you may refine | purify by ultraprecision distillation which increased the number of stages.

The purity of propylene in the raw material propylene is not particularly limited, and considering the economics involved in the purification, the purity of propylene is 90% or more, preferably 9%.
Those having 2% or more are preferably used.

The content of the unsaturated hydrocarbon having 2 to 5 carbon atoms in the starting propylene is preferably as small as possible, but even if the content is reduced to 1 ppm or less, a further increase corresponding to the increase in the cost is required. No improvement in yield is observed.
It is sufficient to reduce the content of diene and acetylene having 2 to 5 carbon atoms to about 0.1 ppm.

The production of acrolein and acrylic acid from propylene and the production of acrylic acid from propylene by a two-step reaction according to the method of the present invention are carried out when the content of unsaturated hydrocarbon having 2 to 5 carbon atoms as raw propylene is 500%.
The method can be carried out according to a method generally used or known to be used, except that a substance having a concentration of ppm or less is used.

For example, as the catalyst to be used, a catalyst generally used for producing acrolein and acrylic acid from propylene or acrylic acid from propylene by a two-step reaction can be used. For example, in the production of acrylic acid by a two-step reaction, a metal oxide catalyst containing molybdenum and bismuth as essential components can be used as the oxidation catalyst used in the first step. Among these, preferred are the oxidation catalysts represented by the general formula (1).

[0028]

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Here, Mo is molybdenum, Bi is bismuth, Fe is iron, A is at least one element selected from cobalt and nickel, and B is at least one element selected from alkali metals, alkaline earth metals and thallium. Element, C is at least one element selected from tungsten, silicon, aluminum, zirconium and titanium, D is phosphorus, tellurium, antimony, tin, cerium,
O represents at least one element selected from lead, niobium, manganese, arsenic and zinc, O represents oxygen, and a, b,
c, d, e, f, g and x are respectively Mo, Bi, F
represents the atomic ratio of e, A, B, C, D and O, and a = 12
When b = 0.1-10, c = 0.1-20, d = 2
-20, e = 0.001-10, f = 0-30, g = 0
And x is a numerical value determined by the oxidation state of each element.

The shape of the oxidation catalyst may be cylindrical, ring-shaped, spherical, etc., or may be amorphous, and may be supported on an inert carrier or the like, if necessary, or the active ingredient may be formed by an appropriate method. May be molded. In addition to the above ingredients,
A molding aid, a reinforcing agent, and the like can be added. For example, various glass fibers, whiskers, and the like can be used.

The oxidation catalyst is not limited to a single type, but may be partially diluted with an inert carrier or the like, or may be prepared by changing the components, preparation method, calcination conditions and the like to prepare a plurality of different types of activities. An oxidation catalyst may be used in combination.

As the reactor, a multitubular fixed bed reactor is generally used, but a fluidized bed reactor or a moving bed reactor can also be used. The material of the reactor is not particularly limited, and carbon steel, stainless steel, or the like is used.

The molecular oxygen-containing gas source is not limited to pure oxygen, but may be air or exhaust gas from various plants. Carbon dioxide gas and other NOx, S, etc. contained in ordinary air other than the above-mentioned unsaturated hydrocarbons
There is no particular influence from impurities such as Ox and moisture.

In the present invention, when producing acrylic acid by catalytic gas-phase oxidation of propylene, for example, a two-step reaction, a soluble component such as acrylic acid is substantially converted from a reaction gas containing acrylic acid obtained from a subsequent step to water. The unreacted propylene, which has been recovered or separated using a solvent consisting of or other solvent, can be circulated and used as a raw material gas in whole or in part. In this case, the content of the unsaturated hydrocarbon having 2 to 5 carbon atoms in the raw material propylene composed of circulated propylene and freshly supplied fresh propylene is 500 ppm or less, preferably 45 ppm or less.
0 ppm or less, more preferably 300 ppm or less, particularly preferably 200 ppm or less, and more preferably 2 to 5 carbon atoms
The total content of dienes and acetylenes is 200p
pm or less, preferably 150 ppm or less, more preferably 100 ppm or less, particularly preferably 50 ppm or less.

In order to carry out the process of the present invention, the above-mentioned oxidation catalyst is charged into a multitubular reactor, and then the reaction zone is made up of a raw material propylene, a molecular oxygen-containing gas and an inert gas mixed as required. 250 to 4
Reaction temperature of 50 ° C, preferably 280-400 ° C, 30
0 to 5,000 hr ^-1 , preferably 700 to 3,000
It is carried out by flowing at a space velocity of hr ^-1 .

[0036]

According to the present invention, since side reactions can be effectively suppressed, by-products such as organic acids, high-boiling compounds, and tar-like compounds, and precipitation of carbides, and the rise of pressure loss and pipe clogging, Problems such as deterioration of quality can be solved.

According to the present invention, a decrease in the performance of the oxidation catalyst used can be effectively suppressed. Therefore, according to the present invention, acrolein and acrylic acid can be stably produced from propylene in a high yield for a long period of time. In particular, when acrylic acid is produced by a two-step reaction, it is possible to produce acrolein mainly from propylene in a high yield in the first step, and to produce acrylic acid in a high yield in the second step and stably over a long period of time. it can.

[0038]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The conversion of propylene, the yield of acrolein, and the yield of acrylic acid were determined according to the following equations.

[0039]

(Equation 1)

The content of the unsaturated hydrocarbon having 2 to 5 carbon atoms and the total content of dienes and acetylenes were determined by gas chromatography.

Example 1 (Preparation of catalyst) A catalyst was prepared as follows according to the method described in Example 1 of JP-B-47-42241.
While heating and stirring 1500 ml of water, 1062 g of ammonium molybdate and 314 g of ammonium paratungstate were dissolved therein. To this aqueous solution, an aqueous solution obtained by dissolving 700 g of cobalt nitrate in 200 ml of distilled water, an aqueous solution obtained by dissolving 243 g of ferric nitrate in 200 ml of distilled water, and 300 ml of acidic water obtained by adding 292 g of bismuth nitrate to 60 ml of concentrated nitric acid were added. A mixed solution of a nitrate aqueous solution obtained by mixing an aqueous solution dissolved in the above solution was added dropwise. Continued,
An aqueous solution in which 244 g of a 20% by weight silica sol solution and 2.02 g of potassium hydroxide were dissolved in 150 ml of distilled water was added. The suspension thus generated is heated and stirred,
After evaporation, the mixture was molded into a column having a diameter of 5 mm, and calcined at a maximum temperature of 450 ° C. for 6 hours in an air flow to obtain a catalyst. The composition ratio of this catalyst (excluding oxygen) was as follows.

[0042]

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(Oxidation reaction) The above catalyst was added to a stainless steel reaction tube having an inner diameter of 25 mm and a length of 4200 mm immersed in a molten salt bath kept at a substantially uniform temperature, and the layer length was 3000.
mm so that the propylene concentration is 6.5.
The reaction was carried out at a temperature of 325 ° C. by supplying a reaction gas consisting of volume%, air volume 65% and the remaining water vapor at a space velocity of 1800 hr ⁻¹ . The composition of the propylene was as follows.

Propylene: 96% by volume Propane and the like: Residual Content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 47 ppm Content of dienes and acetylenes: 10 ppm The results at the beginning of the reaction and after the reaction was continued for 4000 hours are as follows. It was as follows.

(Initial stage of reaction) Propylene conversion: 96.5 mol% Acrolein yield: 78.5 mol% Acrylic acid yield: 10 mol% (after 4000 hours) Propylene conversion: 96.0 mol% Acrolein yield : 79.0 mol% Acrylic acid yield: 9.7 mol% Example 2 The following composition ratio (excluding oxygen) according to the catalyst preparation of Example 1
Was prepared.

[0046]

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Thereafter, propylene was oxidized in the same manner as in Example 1. The composition of propylene used here was as follows.

Propylene: 96% by volume Propane, etc .: Residual Content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 450 ppm Content of dienes and acetylenes: 70 ppm The results at the beginning of the reaction and after 4000 hours of continuous reaction are as follows: It was as follows.

(Initial stage of reaction) Propylene conversion: 96.0 mol% Acrolein yield: 77.8 mol% Acrylic acid yield: 10.5 mol% (after 4000 hours) Propylene conversion: 95.6 mol% acrolein Yield: 78.2 mol% Acrylic acid yield: 9.8 mol% Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that propylene having the following composition was used.

Propylene: 91% by volume Propane and the like: Residual Content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 800 ppm Content of dienes and acetylenes: 50 ppm The results at the beginning of the reaction and after the reaction was continued for 4000 hours are as follows. It was as follows.

(Initial stage of reaction) Propylene conversion: 95.5 mol% Acrolein yield: 77.2 mol% Acrylic acid yield: 9.5 mol% (after 4000 hours) Propylene conversion: 94.5 mol% Acrolein Yield: 76.2 mol% Acrylic acid yield: 8.8 mol% Comparative Example 2 A reaction was carried out in the same manner as in Example 2 except that propylene having the following composition was used as propylene.

Propylene: 96% by volume Propane and the like: Residual Content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 600 ppm Content of dienes and acetylenes: 250 ppm The results at the beginning of the reaction and after the reaction was continued for 4000 hours are as follows. It was as follows.

(Initial stage of reaction) Propylene conversion: 95.8 mol% Acrolein yield: 75.5 mol% Acrylic acid yield: 8.7 mol% (after 4000 hours) Propylene conversion: 94.5 mol% acrolein Yield: 74.2 mol% Acrylic acid yield: 7.8 mol% Example 3 Multitubular reactor (1) having ancillary equipment for cooling the reaction product gas and a multitubular reactor independent of this The reactor (2) was connected by a pipe, and the reactor (1) was filled with the same catalyst as in Example 1 so as to have a layer length of 3000 mm. The reactor (2) had the following composition:

[0054]

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(However, except for the carrier and oxygen;
-Prepared by the method described in Example 1 of No. 206,503) to a layer length of 3000 mm.
The reaction product gas in the reactor (1) is immediately cooled to 280 ° C. or less at the outlet of the catalyst layer in order to prevent the occurrence of post-reaction, and the pipe connecting the reactor (1) and the reactor (2) is C., and the residence time of the gas in the piping was set to 5 seconds or less.

Propylene having the following composition was used as propylene.

Propylene: 96% by volume Propane and the like: Residual Content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 47 ppm Content of dienes and acetylenes: 10 ppm Reaction temperature of reactor (1) at 325 ° C. The reaction temperature of the apparatus (2) was set to 265 ° C., and a reaction gas consisting of a propylene concentration of 6% by volume, air of 60% by volume and remaining steam was supplied at a space velocity of 1,500 hr ⁻¹ to carry out the reaction. The catalytic performance in the connection of the reactor (1) and the reactor (2) at the beginning of the reaction was as follows.

(Initial stage of reaction) Propylene conversion: 96.7 mol% Acrylic acid yield: 89.2 mol% Acrolein yield: 0.5 mol% When this reaction was continued for 4000 hours, the reaction apparatus (1)
And the reactor (2) were at the same temperature as above, and the performance of these connected catalysts was as follows.

(After 4000 hours) Propylene conversion: 96.1 mol% Acrylic acid yield: 88.7 mol% Acrolein yield: 0.7 mol% The catalyst of the reaction apparatus (1) during the above reaction period No change in pressure loss was observed after the formation.

Comparative Example 3 A reaction was carried out in the same manner as in Example 3 except that propylene having the following composition was used as propylene.

Propylene: 88% by volume Propane, etc .: Residual content of unsaturated hydrocarbon having 2 to 5 carbon atoms: 1600 pp
m Content of dienes and acetylenes: 250 ppm The catalytic performance of the connected reactor (1) and reactor (2) at the beginning of the reaction was as follows.

(Initial stage of the reaction) Conversion of propylene: 94.3 mol% Acrylic acid yield: 78.8 mol% Acrolein yield: 3.9 mol% When this reaction was continued for 4000 hours, the reaction apparatus (1)
And the reactor (2) were at the same temperature, and the performance of these connected catalysts was as follows.

(After 4000 hours) Propylene conversion: 92.7 mol% Acrylic acid yield: 75.8 mol% Acrolein yield: 4.3 mol% During the above reaction period, the catalyst of the reactor (1) was used. The pressure loss after the bed increased by 400 mm water column. When the reaction was stopped and the cause of the increase in pressure loss was confirmed, carbide formation was recognized from the outlet of the catalyst layer of the reactor (1) to the inlet of the catalyst layer of the reactor (2), indicating that this was the cause. Was.

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Claims (5)

[Claims] 1. A process for producing acrolein and acrylic acid by subjecting propylene to gas-phase oxidation with a molecular oxygen-containing gas in the presence of an oxidation catalyst, the method comprising the steps of: A process for producing acrolein and acrylic acid, the content of which is not more than 500 ppm (weight). 2. A pre-process in which propylene is gas-phase oxidized with a molecular oxygen-containing gas in the presence of an oxidation catalyst to mainly produce acrolein, and the acrolein-containing reaction gas is vaporized with the molecular oxygen-containing gas in the presence of the oxidation catalyst. In a method for producing acrylic acid by a two-step reaction comprising a latter step of producing acrylic acid by phase oxidation, the content of unsaturated hydrocarbon having 2 to 5 carbon atoms (excluding propylene) in a propylene raw material is set to 500 ppm (weight). ) A method for producing acrylic acid, characterized by the following. 3. The total content of a diene and an acetylene having 2 to 5 carbon atoms in a propylene raw material is 200 ppm.
3. The method according to claim 1, wherein the weight is not more than (weight). 4. The method according to claim 1, wherein the content of the unsaturated hydrocarbon having 2 to 5 carbon atoms (excluding propylene) is 300 ppm (weight) or less. 5. The method according to claim 1, wherein the contents of the non-volatile residue and the sulfur content in the propylene raw material are 100 ppm (weight) or less and 100 ppm (weight) or less, respectively.