Method for preparing acrylic acid

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing acrylic acid and selective oxidation of propylene to acrolein. Method involves carrying out reaction of propylene with oxygen in the first zone reaction with the first catalyst corresponding to the following formula: A_aB_bC_cCa_dFe_eBi_fMo₁₂O_x wherein A means Li, Na, K, Rb and Cs and their mixtures also; B means Mg, Sr, Mn, Ni, Co and Zn and their mixtures also; C means Ce, Cr, Al, Sb, P, Ge, Sn, Cu, V and W and their mixtures also wherein a = 0.01-1.0; b and e = 1.0-10; c = 0-5.0 but preferably 0.05-5.0; d and f = 0.05-5.0; x represents a number determined by valence of other presenting elements. Reaction is carried out at enhanced temperature providing preparing acrylic acid and acrolein and the following addition of acrolein from the first reaction zone to the second reaction zone containing the second catalyst used for conversion of acrolein to acrylic acid. Method provides high conversion of propylene to acrylic acid and acrolein.

EFFECT: improved preparing method.

7 cl, 1 tbl, 5 ex

The present invention relates to the creation of an improved method for the production of acrylic acid. Currently, acrylic acid is produced using a two-step method, according to which first produce oxidation of propylene to acrolein over a catalyst of a mixture of metal oxides containing iron, bismuth and molybdenum, activated the corresponding elements, and then additionally produce oxidation of acrolein to acrylic acid over a second catalyst in a separate reactor. Usually easily available catalyst from a mixture of oxides of iron, bismuth and molybdenum, activated the relevant elements for selective oxidation of propylene to acrolein (i.e. for the initial operation of the two-stage method for the production of acrylic acid). Examples of suitable catalysts for carrying out the specified first operation shown in U.S. patent No. 4162234 and 4280929.

When carrying out the second operation of the two-way carry out the oxidation of acrolein over the second catalyst in the acrylic acid. Always the selectivity of the conversion of acrolein in acrylic acid is less than 100%. However, acrylic acid, which was formed at the first stage of the two-way passes through the second reactor without decomposition. Sledovatel is but it is advantageous to use a catalyst which produces a significantly large amount of acrylic acid during the oxidation of propylene to acrolein in the first reactor, resulting in possible to increase the yield of acrylic acid in a two-stage method.

In the application for U.S. patent No. 08/923878 on September 2, 1997, discovered a new catalyst designed for use in the manufacture of Acrylonitrile and hydrogen cyanide. The specified catalyst contains a mixture of oxides of iron, bismuth and molybdenum, activated various metals, and allows for the production of Acrylonitrile to obtain a much higher yield of hydrogen cyanide, which is a by-product. The applicants of the present invention have found that the catalyst disclosed in the related application U.S. patent No. 08/923878, not only can be used at the first stage of two-stage production method of acrylic acid, but also allows to achieve a surprisingly high yield of acrylic acid in the first stage of the two-way. This high yield of acrylic acid at this stage leads to the achievement of a higher full output of acrylic acid in a two-stage method.

Summary of invention

The main task of the present invention to provide a novel method for the production of acrylic acid and selective oxidation of propylene to acrolein.

To achieve the above objectives, in accordance with the present invention it is proposed a method, which provides for the reaction of propylene and oxygen (mainly in the form of oxygen-containing gas such as air) in a reaction zone with a catalyst in accordance with the following formula:

A_aB_bC_cCa_dFe_eBi_fMo₁₂O_x,

where A=Li, Na, K, Rb and Cs, and mixtures thereof

In=Mg, Sr, Mn, Ni, Co and Zn, and mixtures thereof

C=CE, Cr, Al, Sb, P, Ge, Sn, Cu, V, and W and mixtures

and

a=0.01-1.0; b and e=1.0-10;

C=0-5 .0 and mostly 0.05-5.0, and preferably, from 0.05 to 4.0;

d and f=0.05-5.0, and x is a number determined by the valence of the other elements present;

at elevated temperatures (for example, from 200° to 600° (C)allowing to obtain acrylic acid and acrolein.

In accordance with the first preferred embodiment of the present invention And are selected from the group comprising lithium, sodium, potassium and cesium, and mixtures thereof, and most preferred are cesium and potassium.

In accordance with another preferred option is chosen from the group comprising magnesium, manganese, Nickel, cobalt, and mixtures thereof.

In accordance with another preferred option is chosen from the group comprising cerium, chromium, antimony, phosphorus, germanium, tungsten, and mixtures thereof, and most preferred are cerium, chromium, phosphorus and germanium.

In accordance with another preferred option and may be within the range of about .05 to .9, but mainly approximately from 0.1 to 0.7.

In accordance with another preferred option b and e can be within the range of approximately from 1 to 10. In accordance with another preferred option, C, d and f can be within the range of approximately from 0.05 to 4, and mainly from 0.1 to 3.

In accordance with another preferred option the proposed method involves extracting acrylic acid and acrolein from the first reaction zone, introducing at least acrolein and oxygen in the second reaction zone with a second catalyst for the reaction of acrolein and oxygen at elevated temperature, to obtain acrylic acid, and extracting acrylic acid from the second reaction zone. On the specified second stage may be used any suitable catalyst for promoting the conversion of acrolein in acrylic acid. For example, a typical catalyst for the second stage of the method (e.g., 62% Sb₃Sn₃V₃W_1.2Mo₁₂O_x•38% SiO₂), described in U.S. patent No. 3840596 are preferred to undertake the program of the present invention.

In accordance with another preferred variant, the first reaction of the conversion of propylene to acrylic acid and acrolein takes place in the reactor with a fluidized bed of catalyst, and the second reaction conversion acrolein in acrylic acid takes place in a reactor with a fixed catalyst bed.

In accordance with the present invention can be used catalyst on the carrier, or without the media. Mostly use the catalyst on an inert carrier of silicon dioxide, aluminum oxide or zirconium, or mixtures thereof, and a preferred carrier is silica.

Detailed description of the invention

The catalysts in accordance with the present invention can be prepared using any of the many well-known specialists in the method of preparation of the catalysts. For example, the catalyst may be prepared by using co-deposition of different ingredients. Obtained using co-deposition mass can then be dried and milled to the appropriate particle size. Alternatively, obtained using co-deposition material can be introduced into a slurry and spray dried in accordance with known technology. The catalyst may be extruded in the form of tablets or formed in the form of spheres in oil, h is of itself known. Alternatively, the components of the catalyst can be mixed with a carrier in the form of a suspension, followed by drying, or they can be impregnated with silicon dioxide or other media. Specific methods of obtaining catalysts described in U.S. patent 5093299; 4863891 and 4766232.

Typical component And catalyst may be introduced into the catalyst in the form of the oxide or salt, which, after annealing forms an oxide. Mostly use salt such as nitrides, which are easily accessible and readily soluble, as a means of introducing element And the catalyst.

Bismuth can also be introduced into the catalyst in the form of the oxide or salt, which, after annealing forms an oxide. Preferred are water-soluble salts, which are easily dispersed, but form stable oxides by heat treatment. Particularly preferred source for the introduction of bismuth is bismuth nitrate in the form of a solution in nitric acid.

For the introduction of the iron component in the catalyst may be used any compound of iron, which, after annealing forms oxides. As with other introduced into the catalyst elements, preferred are water-soluble salt, as they can easily be uniformly dispersed in the catalyst. Especially preferred salt is the nitrogen-jelly what Naya salt (iron nitrate).

Cobalt, Nickel and magnesium can also be introduced into the catalyst with the use of nitrate salts. However, magnesium can also be introduced into the catalyst with the use of insoluble carbonate or hydroxide, which after heat treatment forms the oxide.

For the introduction of a component of molybdenum in the catalyst may be used any molybdenum oxide, such as dioxide, trioxide, pentoxide, niobium or heptaoxide. However, as the source of molybdenum is mainly used or hydrolyzable biodegradable salt of molybdenum, with the most preferred starting material is heptamolybdate ammonium.

Phosphorus can be introduced into the catalyst in the form of a salt of an alkali metal or alkaline-earth metal, however, is mainly introduced in the form of phosphoric acid. Calcium, which is the main ingredient of the catalyst in accordance with the present invention, may be introduced by the preliminary formation of calcium molybdate or by impregnation or other known types of processing, however, calcium is usually administered in the form of calcium nitrate together with other nitrates.

The present invention is directed to a method of production of acrylic acid during the oxidation of propylene to acrolein, which provides for the reaction of oxygen and propylene in the area of R is the action upon contact with the catalyst, which corresponds to the following empirical formula:

A_aB_bC_cCa_dFe_eBi_fMo₁₂O_x,

where A=Li, Na, K, Rb and Cs, and mixtures thereof; B=Mg, Sr, Mn, Ni, Co and Zn, and mixtures thereof; C=CE, Cr, Al, Sb, P, Ge, Sn, Cu, V, and W and mixtures thereof; and a=0.01-1.0; b and e=1.0-10; C=0-5 .0 and mostly 0.05-5.0, and preferably, from 0.05 to 4.0; d and f=0.05-5.0, and x is a number determined by the valence of the other elements present; to obtain acrylic acid and acrolein. Mostly the reaction proceeds at a temperature of from 200° 500°and preferably, from 300° 400°C.

The catalysts in accordance with the present invention can be prepared by mixing an aqueous solution of heptamolybdate ammonium Sol of silicon dioxide, with the addition of an aqueous solution of a suspension, which contains compounds of other elements, drying aqueous solution, denitrification and calcination. The catalyst may be dried using a spray drying at a temperature of from 110°With up to 350°C. Temperature denitrification is in the range from 100°With up to 450°C. Finally, the calcination is carried out at a temperature of 400°700°C.

In accordance with another preferred embodiment of the present invention the method involves the extraction of acrylic acid and acrolein obtained in the first reaction zone, introduction at least acrolein and oxygen (mainly when using air as the oxygen source) at elevated temperature in the second reaction zone containing a suitable conversion acrolein in the acrylic acid of the second catalyst, the conversion of acrolein in acrylic acid, and extracting acrylic acid from the second reaction zone. Suitable catalysts for use in the conversion of acrolein in acrylic acid described in previously mentioned U.S. patent No. 3840595. As specific examples of catalysts which can be used in the second reaction zone, you can specify Mo₉V₂W₁Cu₁Sn_0.4O_x; Mo₁₀W₁V₃Sb₂Cu₁Nb₂O_x; Mo₁₂V₃W_1.2Cu₂Ti_0.5O_x; Mo₉V₂W₁Cu_1.5Sn_0.4P₁O_x; Mo₁₂V₃W_1.2Cu₂Sn_0.5O_xand Sb₃Sn₃V₃W_1.2Mo₁₂O_x. These catalysts are inert carriers, such as aluminum oxide, zirconium oxide or silicon dioxide, and mostly silicon dioxide. Typically the catalyst on an inert carrier contains from 70 to 75 wt.% the active phase and from 25 to 30 wt.% inert carrier.

The following examples are not restrictive nature of the and and serve only to illustrate the present invention.

In each of the following examples of processes carried out in a reactor with a fluidized bed capacity of 40 cm³at 0.05-0.10 wwh, with the feed mixture 1C₃ ⁼/1.7O₂/9.3N₂/3H₂O at a temperature of 360°C and pressure of 15 psig.

1. A method of manufacturing acrylic acid, which provides for the reaction of propylene and oxygen in the first reaction zone with a first catalyst, which corresponds to the following formula:

A_aB_bC_cCa_dFe_eBi_fMo₁₂O_x,

where A = Li, Na, K, Rb and Cs, and mixtures thereof;

In = Mg, Sr, Mn, Ni, Co and Zn, and mixtures thereof;

C = CE, Cr, Al, Sb, P, Ge, Sn, Cu, V, and W and mixtures thereof,

and

a = 0.01-1.0; b and e = 1.0-10;

C = 0-5 .0, mostly 0.05-5.0;

d and f = 0.05-5.0; x is a number determined by the valence of the other elements present;

at elevated temperatures, allowing to obtain acrylic acid and acrolein, and the subsequent introduction of at least acrolein from the first reaction zone into a second reaction zone containing a second catalyst that is used to convert acrolein in acrylic acid.

2. The method according to claim 1, in which And are selected from the group comprising lithium, sodium, potassium and cesium, and mixtures thereof.

3. The method according to claim 2, in which the In is chosen from the group which includes magnesium, manganese, Nickel, cobalt, and mixtures thereof.

4. The method according to claim 3, in which is chosen from the group comprising cerium, chromium, phosphorus, germanium, and mixtures thereof.

5. The method according to claim 4, in which a is in the range from 0.05 to 0.9.

6. The method according to claim 5, in which b is in the range 2 to 9.

7. The method according to claim 6, in which C, d and f is in the range from 0.1 to 4.