US3736355A

US3736355A - Process for the preparation of unsaturated acids

Info

Publication number: US3736355A
Application number: US00884734A
Authority: US
Inventors: M Croci; A Croci; M Biagioni; E Cavaterra
Original assignee: Montedison SpA
Current assignee: Montedison SpA
Priority date: 1968-12-16
Filing date: 1969-12-12
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29
Also published as: DE1962431C3; DE1962431A1; GB1287483A; NL6918448A; SE368777B; FR2026214A1; DE1962431B2; ES374571A1; BE743146A

Abstract

ALPHA-BETA UNSATURATED OLEFINS, PARTICULARLY PROPYLENE, ARE OZIDIZED IN THE VAPOR PHASE BY MOLECULAR OXYGEN, WITH THE PRODUCTION OF THE CORRESPONDING UNSATURATED CARBOXYLIC ACIDS, PARTICULARLY ACRYLIC ACID.

Description

United States Ratent O US. Cl. 260-533 N 2 Claims ABSTRACT OF THE DISCLOSURE Alpha-beta unsaturated olefins, particularly propylene, are oxidized in the vapor phase by molecular oxygen, with the production of the corresponding unsaturated carboxylic acids, particularly acrylic acid.

THE PRIOR ART The oxidation of olefins to the corresponding unsaturated carboxylic acids has been described in various patents according to which the reaction occurred either in a single phase and led directly to the desired product, or in two phases, the olefins being oxidlzed to the corresponding unsaturated aldehyde in the first phase, and the aldehyde being oxidized to the desired unsaturated carboxylic acid in the second phase.

For the production of the unsaturated carboxyllc acids on an industrial scale, the single phase process is preferred. A great variety of catalysts may be used in that process.

However, it is known that, in general, the results obtained are not entirely satisfactory. One drawback is that, in addition to the unsaturated carboxylic acid, considerable quantities of unsaturated aldehyde are formed and must be recycled in order to obtain a satisfactory yield of the acid. In an industrial operation, such recycling is a burdensome, uneconomical disadvantage.

THE PRESENT PROCESS The primary object of the present invention is to provide a process for oxidizing the unsaturated alpha-beta olefins to the corresponding unsaturated aliphatic carboxylic acids in good yields and with the formation of the aldehydes in such minimum quantities that recycling thereof is not necessary. More particularly, it is an object of the invention to oxidize propylene to high yields of acrylic acid, with minimum formation of the intermediate aldehyde and hence the elimination of any need for recycling the latter.

These and other objects are accomplished by this invention in accordance with which alpha-beta olefins are oxidized to the corresponding unsaturated aliphatic carboxylic acids by reacting the alpha-beta olefin and molecular oxygen in a vapor phase, at temperatures of from 300 C. to 500 C., and in the presence of a catalyst consisting of molybdenum, vanadium, tellurium, oxygen and, in the given case, other elements capable of combining with tellurium to form alloys or tellurides in which there is present at least one of oxygen, molybdenum, and/ or vanadium, and/or tellurium having an oxidation state lower than the maximum.

The ratios between the elements constituting the catalyst may vary within a Wide range. Thus, for 1 gram atom of molybdenum there may be used from 2.0 to 0.05 gram atoms of vanadium and from 2.0 to 0.02 gram atoms of tellurium, preferably from 1.0 to 0.1 gram atom of vanadium and from 1.0 to 0.1 gram atom of tellurium. In order to obtain such catalysts, the molybdenum and vanadium are subjected, for example as ammonium salts, to a heat treatment at temperatures comprised between 350 C. and 550 C., in the absence of oxygen. The tellurium may be added either before or after the heat treatment.

In a preferred embodiment, the catalyst used in the present process is prepared by evaporating an aqueous solution of ammonium para-molybdate and ammonium meta-vanadate to dryness, and then subjecting the product thus obtained, to a heat treatment at temperatures comprised between 350 C. and 550 C., for a time varying from 2 to 16 hours, and in the absence of oxygen. Tellurium, tellurium dioxide, or a metal telluride, for instance, nickel telluride, is then mixed mechanically with the heat-treated product.

In another preferred embodiment, the catalyst is prepared by evaporating an aqueous solution of ammonium para-molybdate, ammonium meta-vanadate, and telluric acid to dryness and subjecting the product thus obtained to heat treatment at temperatures comprised between 350 C. and 550 C., for from 2 to 16 hours, in the absence of oxygen.

Instead of using the ammonium salts of molybdenum and vanadium as starting materials for preparation of the catalyst, the oxides of those elements may be used, for instance molybdenum trioxide and vanadium pentaoxide. In that case, the oxides are mixed together and the mixture is then subjected to a heat treatment in the presence of a gas containing ammonia, and at temperatures comprised between 350 C. and 550 C.

Besides tellurium metal, other products containing the element may be used, such as, for instance, tellurium dioxide, metal tellun'des, telluric acid, and ammonium tellurate.

The catalyst may be used with or without a carrier. Suitable carriers or supports include silica, alumina, silicaalumina, pumice stone, silicium carbide, etc. Furthermore, the catalyst may be used as a fixed or as a fluidized bed.

The reaction temperature may vary from 300 C. to 500 C., but is preferably in the range 350 C. to 420 C.

The reaction may be conducted at atmospheric pressure, or it may be conducted at increased pressure (e.g., up to 10 absolute atms.) in order to increase production of unsaturated acid.

The contact time, defined as the ratio between the apparent volume of the catalyst and the volume of the fed gas under the given reaction conditions in a unit of time, may vary from 0.05 to 25 seconds, but is preferably from 0.5 to 10 seconds.

The oxygen used to oxidize the alpha-beta olefins may originate from any appropriate source. Air is preferred. The oxygen/olefin molar ratio may be from 0.5:1 to 5:1, and is preferably from 1:1 to 3:1.

The oxidation is preferably conducted in the presence of one ormore diluents, such as: nitrogen, steam, carbon dioxide, and saturated hydrocarbons. The yield in unsaturated acidsis quite independent from the nature of the diluents. It has now been found that the presence of steam increases the quantity of acetic acid produced. Therefore, if it is desired to limit the acetic acid production it is convenient to use other diluents, in particular nitrogen.

However, steam may be useful for its effectiveness in dissipating the reaction heat, or when the formation of acetic acid is not undesirable. Furthermore, steam permits an increase in the concentration of propylene, restricting the inflammability of the air/propylene mixture.

The present invention provides a very advantageous process for the preparation of alpha-beta unsaturated aliphatic carboxylic acids, particularly acrylic acid. In fact,

about 120 Nl/hour of a gas consisting of 10% of ammonia and 90% of nitrogen. At various time intervals, 40 g. samples were taken out and to each sample there was added the same quantity (3.8 g.) of nickel telluride (NiTe The samples were then kneaded, dried, granulated and finally tested on the equipment specified in Example 1.

The following table shows the results of these tests carried out at a temperature of 370 C., under a pressure of 1.2 absolute atm., with a contact time of 2 seconds and with a feed-mixture consisting of 5% by volume of propylene, 42.5% of air and 52.5% of nitrogen.

1 From the examination of the above table it can be seen how the duration of the reducing treatment shows an optimum.

Conversion of olefin in moles of fed olefin moles of unreacted olefin M0165 of fed olefin X 100 Selectivity of the products in g. atoms of carbon in the product X100 g. atoms of carbon in the reacted olefin In all the examples the reaction products were determined by means of a gas chromatograph.

EXAMPLE 1 175.6 g. of ammonium paramolybdate were dissolved in 300 cc. of water. Thereupon there were added 22.8 g. of ammonium metavanadate and the whole was then heated until complete dissolution was attained. This solu tion was evaporated to dryness and the product was reduced into granules and subdivided into three parts: a, b and c, which were activated at the same temperature of 450 C., for the same period of time (8 hours), but in difierent atmospheres, i.e.:

part a: in an air current; part b: in a nitrogen current, and part c: in a current of nitrogen containing 10% of NH 50 g. of each activated product were admixed with 4.9 g. of tellurium dioxide, kneaded with a little water, dried and reduced into granules having a diameter comprised between 0.2 and 0.3 mm., thereby originating respectively catalysts A, B and C.

The catalysts were tested by filling them into a steel reactor 100 mm. long and with an inside diameter of 10 mm., immersed in a bath of molten tin, into which was sent a gaseous mixture consisting of 5% by volume of propylene, 42.5 of air and 52.5% of nitrogen.

At a temperature of 400 C., under a pressure of 1.2 atm. and with a contact time of 0.7 second, the following results were obtained:

Selectivity (percent) in- Over a product based on molybdenum and vanadium, obtained as described in Example l-part a, were passed, through a Pyrex glass pipe, at a temperature of 450 C.,

From the examination of the above table it can be seen how the duration of the reducing treatment shows an optimum.

EXAMPLE 3 An aqueous solution containing 55 g. of ammonium paramolybdate, 7.26 g. of ammonium meta-vanadate and 7.14 g. of telluric acid, was evaporated to dryness and subsequently subejected to activation in a nitrogen current at 450 C., for 8 hours. Thereby, a catalyst was obtained which was used in an oxidation test carried out on the same equipment cited in Example 1, using a feedmixture consisting of 5% by volume of propylene, 42.5% of air and 52.5% of nitrogen, at a temperature of 360 C. and under a pressure of 1.2 absolute atm., with a contact time of 2 seconds.

The results thereby obtained were as follows:

Percent Conversion of propylene 84.6

Selectivity in acrylic acid 67.4

Selectivity in acrolein 3.0

Selectivity in acetic acid 4.8

Selectivity in Co +CO M8 EXAMPLE 4 Percent Conversion of propylene 90.0 Selectivity in acrylic acid 66.4 Selectivity in acrolein 9.7 Selectivity in acetic acid 2.9 Selectivity in CO +CO 21.0

EXAMPLE 5 45 g. of a product based on molybdenum and vanadium, obtained as described in Example 1 (part b), were soaked with an aqueous solution containing 5.3 g. of telluric acid.

The product thus obtained was then dried in an oven and additioned with an aqueous solution containing hydrazine in excess for reducing the telluric acid to metaltellurium. Thereupon, the product was again brought to dryness and was then heated up to 300 C. in a nitrogen current in order to eliminate the excess hydrazine. Finally, the product was granulated to particles having a diameter comprised between 0.2 and 0.3 mm. It was then tested under the same reaction conditions as those used in Example 1, except for the temperature which was kept at 370 C. and the contact time which was maintained at 2 seconds. The results of these tests were the following:

Percent Conversion of propylene 85 Selectivity in acrylic acid 67 Selectivity in acrolein 9 Selectivity in acetic acid 3 Selectivity in CO +CO 21 EXAMPLE 6 49 g. of a product based on molybdenum and vanadium, obtained as described in Example 1 (part b), were additioned with 5.0 g. of molybdenum and cobalt telluride (CoMoTe With this mixture a catalyst was prepared which was tested under the same conditions as those specified in Example 5. The results were as follows:

Percent Conversion of propylene 86 Selectivity in acrylic acid 67 Selectivity in acrolein 7 Selectivity in acetic acid 3 Selectivity in CO-l-CO 23 EXAMPLE 7 40 g. of a product based on molybdenum and van-adium, obtained as described in Example 1 (part b), were additioned with 3.8 g. of nickel telluride. With this mixture a catalyst was prepared and tested under the same conditions as those of Example 2. The results were as follows:

Percent Conversion of propylene 88 Selectivity in acrylic acid 65 Selectivity in acrolein l2 Selectivity in acetic acid 3 Selectivity in CO +CO 20 EXAMPLE 8 Over the same catalyst as used in Example 7, Was passed a gaseous mixture consisting of 5% by volume of propylene, 42.5% of air, 25% of steam and 27.5% of nitrogen.

Under the same reaction conditions as those used in Example 5, the results obtained were as follows:

Percent Conversion of propylene 90 Selectivity in acrylic acid 61 Selectivity in acrolein 4 Selectivity in acetic acid 12 Selectivity in CO +CO 23 EXAMPLE 9 The results of experiments carried out with a number of catalysts in which the Te/Mo atomic ratio varied, while the V/ Mo atomic ratio remained constant and equal to 0.2 are recorded on the table that follows.

' To a compound based on molybdenum and vanadium, obtained as described in Example 1 (part b), was added tellurium in the form of molybdenum and cobalt telluride (CoMoTe The recorded data refer to tests carried out with a feed-mixture consisting of 5% by volume of propylene, 55% of air, 40% nitrogen, at a temperature of 360 C., under a pressure of 1.2 absolute atm. and with a contact time of 2 seconds. The test equipment was the same as that described in Example 1.

Catalyst Atomic ratio, Te/Mo Conversion, percent. Selectivity (percent) in:

Acrylic acid Acrolein Acetic acid. OOH-CO 8 EXAMPLE 10 Catalyst Atomic ratio, V/Mo 0.05 0.10 0.20 0.50 1.00 2.00 Conversion, percent 56.0 75.5 89.0 92.5 89.4 88.2 Selectivity (percent) in: 39 4 EXAMPLE 1 1 g. of ammonium paramolybdate were dissolved in 400 cc. of water. To this solution were then added 72.6 g. of ammonium meta-vanadate and the mixture was evaporated to dryness under constant stirring. The dry product was then activated in a Pyrex tube in a nitrogen current at 450 C. for 8 hours.

50 g. of the activated product were additioned with 33.3 of Nite then mixed, kneaded with a little water, dried and finally reduced to granules having a diameter comprised between 0.2 and 0.3 mm.

Into a reactor like that described in Example 1, charged with the above granules, was fed a mixture consisting of 5% by volume of propylene, 55% of air and 40% of nitrogen. At a temperature of 360 C., under a pressure of 1.2 absolute atm., and with a contact time of 2 seconds, the following results were obtained:

Percent Conversion of propylene 90.8 Selectivity in acrylic acid 58.7 Selectivity in acrolein 4.7 Selectivity in acetic acid 4.9 Selectivity in CO +CO 31.7

EXAMPLE 12 36 g. of ammonium paramolybdate were dissolved in 350 cc. of water. To this solution were then added 48.5 g. of ammonium metavanadate and the mixture was evaporated to dryness under stirring.

The dry product was activated in a Pyrex glass tube in a nitrogen current, at 450 C. for 8 hours. 50 g. of the activated product were additioned with 48.2 g. of NiTe mixed, kneaded with a little water, dried and finally reduced into granules having a diameter comprised between 0.2 and 0.3 mm. The tests with this catalyst, conducted as described in Example 11, gave the following results:

Percent Conversion of propylene 93.7 Selectivity in acrylic acid 41.8 Selectivity in acrolein 6.8 Selectivity in acetic acid 8.2

Selectivity in CO +CO 43.2

7 EXAMPLE 13 35.1 g. of ammonium paramolybdate were dissolved in 80 cc. of water. To this solution, there were added 4.6 g. ammonium metavanadate and the whole was heated to obtain a solution in which 3.8 g. of telluric acid were dissolved.

The solution was used to impregnate 81 g. of microspheroidal silica. The product thus obtained was dried in an oven at 110 C. and then activated for 8 hours in a current of nitrogen at 450 C. The carrier represented 70% by weight of the whole catalyst.

By passing over said catalyst a gaseous mixture consisting of by volume of propylene, 37.5% of air and 57.5% of nitrogen, at a temperature of 370 C. and under a pressure of 1.2 absolute atm. and with a contact time of 4 seconds, the following results were obtained:

Percent Conversion of propylene 65 Selectivity in acrylic acid 52 Selectivity in acrolein 4 Selectivity in acetic acid 12 Selectivity in CO -I-CO 32 The same feed-mixture was sent onto the same catalyst fluidized in a reactor having an inside diameter of 70 mm. (380 cc. of catalyst). Under the same conditions as those indicated above, the results were as follows:

Percent Conversion of propylene 57.0

Selectivity in acrylic acid 45.9

Selectivity in acrolein 3.4

Selectivity in acetic acid 7.4

Selectivity in CO +CO 43.3

EXAMPLE 14 47.4 g. of ammonium paramolybdate were dissolved in H O. To this solution were then added 3.1 g. of ammonium metavanadate and the mixture was heated until a solution was obtained, which was then brought up to a volume of 76 cc. This solution was used to impregnate 69.6 g. of microspheroidal silica. The product thus obtained was dried in an oven at 110 C., then activated in an N current at 420 C., for 8 hours; it was again impregnated with an aqueous solution containing 5.16 g. of telluric acid, and finally was dried again at 110 C.

By sending over said catalyst a gaseous mixture consisting of 5% by volume of propylene, 55% of air and 40% of nitrogen, at a temperature of 400 C., under a pressure of 1.2 atm., and with a contact time of 1 second,

the following results were obtained:

. Percent Conversion of propylene 82 Selectivity in acrylic acid 55.6 Selectivity in acrolein 1.8 Selectivity in acetic acid 9.0 Selectivity in CO +CO 33.6

EXAMPLE 15 A gaseous mixture consisting of 8.4% by volume of propylene, 67.6% of air, and 24% of steam was fed over a catalyst exactly like that described in Example 4.

At a temperature of 405 C., under a pressure of 1.2 absolute atm., and with a contact time of 1.5 seconds, the following results were obtained:

Percent Conversion of propylene 91.8

Selectivity in acrylic acid 65.4

Selectivity in acrolein 4.3

Selectivity in acetic acid 8.0

Selectivity in C'O -l-CO 22.3

EXAMPLE 16 305 g. of a product based on molybdenum and vanadium, prepared and activated as described in Example 1 (part b), were mixed with 147.5 g. of nickel telluride.

With this mixture was then prepared a catalyst in granules having a diameter comprised between 1.7 and 2.8 mm.

About 222 cc. of the granules were introduced into a tubular steel reactor having an internal diameter of 20 mm. and which was immersed in a heating bath of molten salts. Into this reactor were then fed 146 Nl/hr. of a gaseous mixture consisting of 5% by volume of propylene, 55 of air and 40% of steam. The inside temperature of the reactor was maintained at 373 C. Thereby, the following results were obtained:

Percent Conversion of propylene 83.6

Selectivit in acrylic acid 66.5

Selectivity in acrolein 6.2

Selectivity in acetic acid 8.5

Selectivity in CO -I-CO 18.8

EXAMPLE 17 A test was carried out on a catalyst prepared as described in Example 7, but activated at a temperature of 420 C., using a feed-mixture consisting of 5% by volume of propylene, 55% of air and 40% of nitrogen, at a temperature of 350 C., under a pressure of 1.2 absolute atm., and with a contact time of 3 seconds.

The testing technique was that described in Example 1. During the test, a high percentage of air was used in order to determine whether, with time, the phenomenon of reoxidation of the catalyst with the consequent loss of the starting performance level would occur. However, the results recorded in the following table show how the activity of the catalyst remained constant with time.

Conversion, Selectivity (percent) inpercent Progressive of Acrylic Acetic time, hours Oil-I5 acid Acrolem acid OOH-CO EXAMPLE 18 35.0 g. of ammonium paramolybdate were dissolved in water. To this solution were then added 4.7 g. of ammonium metavauadate and the mixture was heated to obtain a solution which was then brought up to a volume of 98 cc. with water.

The final solution was used to impregnate 89.7 g. of microspheroidal silica. The product thus obtained was dried in an oven at C., activated in a nitrogen current for 8 hours at 450 C., impregnated again with an aqueous solution containing 22.9 g. of telluric acid and, finally, dried again at 110 C.

By sending over this catalyst a gaseous mixture consisting of 5% by volume of propylene, 55% of air and 40% of steam at a temperature of 380 C., under a pressure of 1.2 absolute atm., and with a contact time of 2 seconds, the following results were obtained:

Percent Conversion of propylene 87.3 Selectivity in acrylic acid 69.8 Selectivity in acrolein 4.1 Selectivity in acetic acid 3.5 Selectivity in CO +CO 22.6

As will be apparent, various changes in details can be made in practicing this invention, without departing from the spirit thereof. Therefore, it is intended to include in the scope of the appended claims all modifications which will be obvious to those skilled in the art from the description and examples given herein.

We claim:

1. A process for preparing acrylic acid, characterized in that propylene and molecular oxygen are reacted in vapor phase at a temperature of from 300 C. to 500"v C. and in contact with a catalyst consisting of molybdenum, vanadium, tellurium and oxygen and obtained from molybdenum and vanadium ammonium salts which have been heat-treated in advance, in the absence of oxygen, in a nitrogen gas atmosphere, and at a temperature of from 350 C. to 550 C., and from a tellurium compound selected from the group consisting of tellurium dioxide, telluric acid and nickel telluride and cobalt-molybdenum telluride, the vanadium/molybdenum atomic ratio in the catalyst being 0.05 to 2.0, and the tellurium/molybdenum atomic ratio therein being from 0.02 to 2.0.

2. The process according to claim 1, in which the heattreatment is carried out in a gaseous 10% ammonianitrogen mixture.

References Cited UNITED STATES PATENTS 3,192,259 6/1965 Fetterly et al. 260-533 N 3,240,806 3/1966 Bethell et a1 260-533 N 3,435,069 3/1969 Bethell et a1 260-533 N 3,439,028 4/1969 Yanagita et a1. 260-533 NX 3,457,303 7/1969 Eden 260-533 N FOREIGN PATENTS 971,666 9/1964 United Kingdom 260-533 N 1,086,523 10/1967 United Kingdom 260-533 N HENRY R. JILES, Primary Examiner R. D. KELLY, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF. CORRECTION Pate t USP 3. 736, 355 Dated Ma L29. 1933 Inventor) Mauro Croci and Enrico Cavaterra It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Col. l, item 5, under the heading Acrolein" the numeral "3. 6" is corrected to 3. 5-

Col. 6, in the 5th column of the Table under Example 10, the fourth numeral "4. 3" is corrected to 4. 2- I Q Col. 8, in the third column of the Table under Example 17, the 6th numeral "57. 8" under the heading "Acrylic acid" is corrected to Signed and sealed this 9th day of April l97h.

' (SEAL) Attest:

EDI/JARD MELETCHERJR. C. MARSHALL DAT-IN Attesting Officer I Commissioner of Patents DRM PO-1 O50 (IO-69) USCOMM-DC BOS76-F'69 it UvS. GOVERNMENT PRINTING OFFICE I959 0-366-334.