JPS60155148A - Increased selectivity for oxidation of olefin to alpha, beta-unsaturated carboxylic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for the oxidation of olefins to produce α,β-unsaturated carboxylic acids. More specifically, the present invention is directed to a new olefin-activated palladium catalyst and an improved process for the oxidation of propylene to acrylic acid in the presence of a free radical inhibitor.

Similarly, isobutylene and butene-1 can be oxidized to methacrylic acid and crotonic acid, respectively.

(Related applications) The subject matter of the present invention is related to the following same-day applications: US Pat.

“Catalytic Oxidation of Olefins to α,β-Unsaturated Carboxylic Acids” and “Increased Selectivity in the Oxidation of Olefins to α,β-Unsaturated Carboxylic Acids” by Lyon et al. The following applications relate to processes in which the catalyst systems described herein are used:

"Catalytic oxidation of propylene to allyl acetate""Process for the oxidation of butenes to linear acetates" (Prior art and problems to be solved) In one step using a Varadium metal catalyst supported on carbon black The oxidation of propylene to acrylic acid is described in Tokoku Patent No. 3,624,147. However, this process is characterized by yields of 60% or less based on the amount of propylene converted, the operating temperature is generally above 90° C., and it is carried out at high pressure. Moreover, substantial amounts of CO2 have been reported as unwanted by-products and low reaction rates have been reported.

A similar method is described in J-Catal, 173 (1972
), where palladium black and palladium activated charcoal were used to convert propylene to acrylic acid. However, only stoichiometric non-catalytic conversions based on palladium metal are taught, thus providing an even less efficient process than the above US patent.

Furthermore, several patents describe conventional methods for the preparation of supported palladium metal catalysts, for example by reduction of palladium salts, using reducing agents such as hydrogen, lower alcohols, hydrazine, or various olefins. For example, US Pat. No. 3,275,680 (Ilolzrichte
r) or 4435598 ()Iinnenkamp)
See.

These teach the reduction of palladium salts with hydrogen or hydrazine. US Pat. No. 4,016,200 (0 oda) similarly teaches that palladium compounds can be reduced to palladium metal using formalin, hydrazine, hydrogen, methanol, or ethylene, propylene-based olefins as reducing agents. Similarly, US Pat. No. 3,970,713 (Scharfe) also teaches the reduction of palladium and other metal salts to metal catalysts using hydrogen, alcohols, olefins, etc. as reducing agents. However, none of these citations teaches the preparation of highly activated palladium metal species by reflexions under unique time and temperature conditions, nor do these catalysts teach the preparation of highly activated palladium metal species under unique time and temperature conditions. It does not teach a surprisingly effective method for oxidizing olefins to alpha, beta unsaturated acids under milder operating conditions. Finally F, R.

Hartley, R., "The Chemistry of Brachymetal Palladium," Willie and Linds, pp. 380-390 and 412-417 (1973), discloses the formation of complexes of ethylene with palladium chloride to provide palladium-42 metal catalysts. However, as described below, the use of ethylene or chloride and the formation of a palladium+2 metal catalyst may deactivate the catalyst of the present invention for the purpose of forming the desired product claimed herein. Do you get it.

U.S. patent application no.
3-046 CIP-1) under mild reaction conditions using a supported palladium catalyst activated by activation with a C3-C6 olefin, preferably propylene, at at least about 60°C for at least about 10 minutes. describes an improved process for the direct oxidation of propylene to acrylic acid with air or oxygen in an aqueous medium. The oxidation reaction is then continued in the presence of the pretreated catalyst at a temperature of at least about 25°C, whereby acrylic acid is recovered at high rates and selectivities in contrast to the prior art described above.

It is thus an object of the present invention to further provide an improvement to the olefin oxidation process using certain free radical inhibitors as described below.

It is a further object of the present invention to oxidize isobutylene to methacrylic acid and butene-1 to crotonic acid in a similar manner.

(Means for Solving the Problem) According to the present invention, α,β-unsaturated carboxylic acids such as Doce
in the presence of an oxidized free radical inhibitor than that obtained by the use of olefin-activated palladium catalysts supported on carbon or alumina, as described in No. I have found that it is even stronger when it is done in a calm manner. By carrying out the oxidation described above in the presence of these, the selectivity to acrylic acid is about 92-93x, i.e., about 5-12x higher than using the activated catalyst alone. It is equally effective in oxidizing isobutylene to methacrylic acid and butene-1 to crotonic acid.

Thus, olefins having about 3 to 6 carbon atoms can be used in the present invention.

As described above, the present invention further improves a novel process for the oxidation of certain olefins, principally propylene, to their corresponding acids in the presence of a pretreated supported palladium catalyst. The above improvement consists in carrying out the oxidation in an aqueous medium with air or oxygen in the presence of a free radical inhibitor such as butylated hydroxytoluene (BIT).

There's no need to be discouraged. Using a catalyst prepared by the novel process discussed in detail below, the catalyst is combined with Applicant's claimed surfactant system to effect the oxidation reaction of propylene to acrylic acid from about 25 to Suffice it to say that it can uniquely be carried out at temperatures in the range of 125 DEG C. and pressures of 1 to 100 atmospheres. US Patent 362414
In contrast to the much more severe conditions used in Example 7, preferably at temperatures between 25 and 80'C, the production is significantly increased over the use of catalyst alone, as shown in the Examples below.

In one preferred embodiment of the process, the liquid reaction medium is passed downwardly through a fixed catalyst bed to increase the reaction rate and simultaneously reduce the reactor volume, and the acrylic acid product is recovered from the bottom. It has been found advantageous to carry out the reaction in a trickle bed reactor. Alternatively, the oxidation reaction can be carried out using an ebulating bed catalyst with gas and solvent circulation.

The starting material from which the catalyst of the present invention is prepared is carbon or, less preferably, alumina or the like, on commercially available 5%, 10x, 20x carbon, available from standard catalyst suppliers such as Johnson-Massey, Inc. It is palladium. The terms "palladium metal catalyst" or "palladium in the metallic state" are used commercially or by other means, such as those shown in Schaffle et al. U.S. Pat. No. 3,970,713 or Horlichter et al. U.S. Pat. refers to a palladium catalyst that has been exposed to the atmosphere during normal process procedures. Although Applicants do not intend to be bound by any particular theory, it is believed that in the normal course of handling and using prior art reduced catalysts following reduction of palladium, due to exposure to the atmosphere, a proportion of palladium surface species Becomes oxidized. It is this air-exposed palladium catalyst that is used as a starting material in the preparation of Applicants' novel olefin activated catalysts.

("Surface species" means any palladium species found on the surface of the catalyst itself, as recognized by those skilled in the catalysis art.) Applicants also do not wish to be bound by any particular theory. Although not intended to be used as It is with these positions that propylene forms the novel surface active species that are the activated catalysts of the present invention.

In the novel activated catalyst of the present invention, as evidence that commercially available reduced palladium is reoxidized under normal handling and exposure to air, e.g. Generates 1 part of active catalyst species.

In preparing the activated oxidation catalyst for use in the present invention using a carbon or alumina supported palladium metal catalyst as defined above with propylene or similar olefins, the activation treatment is carried out at a temperature of at least about 60°C. from about 10 minutes to about 120 minutes, preferably at least about 30 to 60 minutes, at a temperature of up to 150°C, preferably from about 65 to 95°C;
It is essential that it be carried out under oxygen-free conditions as described below.

Although these catalysts have low P on activated carbon, here 1' u :4''<':f P'' activity. As mentioned earlier, the selectivity towards acrylic acid is surprisingly further enhanced by this treatment through the use of the surfactant system defined by the applicant. The term "activated palladium metal catalyst" is therefore used for the purposes of the present invention to refer to catalysts made according to the above method, which...7 and which react faster and at lower temperatures than known supported palladium catalysts. , refers to a catalyst capable of oxidizing propylene to acrylic acid.

During the preparation of the catalysts mentioned above, it is necessary to carry out the catalyst under conditions of maximum purity. Although the presence of small amounts of oxygen, to the extent readily determined by those skilled in the art, can result in a catalyst that performs under somewhat milder conditions than the commercially available catalysts described above, Advantages are derived by activating the catalyst under conditions as free of oxygen as possible, at least within commercially possible levels.

These oxygen-free conditions can be achieved using known methods, e.g. degassed water,
or by using a solvent and pure olefin gas during activation of the catalyst. Degassing is easily accomplished by holding the liquid under vacuum until it boils or by bubbling the desired olefin into the liquid until oxygen can no longer be replaced.Pure olefins are commercially available in various grades, e.g. chemically pure,
Available in research pure grades, or polymeric grades, etc., the latter two being preferred due to their high purity exceeding about 99°7z (the latter two are available, for example, from Matheson,
[1vision of 5earle Medicine
al Products, and 5unCo, respectively).

In order to maintain the oxidation process, and preferably during the oxidation step, the reactor oxygen is maintained in an amount no greater than the stoichiometric amount to oxidize the olefin to acrylic acid. It is understood that the presence of these metals or metal salts that may poison or alter the catalyst should be avoided in preparing the catalyst of the present invention. Examples include iron, manganese, copper, and all other reagents that will oxidize the mouth.

In addition, substances such as amines, hydrazine, and ethylene have been found to be harmful and to be avoided when preparing and using the catalysts of this invention. Moreover, attempts to use nitrogen to prepare this catalyst have shown that the catalyst is
It has been found that exposure to 2-propylene mixtures can cause an explosion and should be avoided.

Although the catalyst of the invention can be prepared separately and kept in an active state provided it is kept in an oxygen-free atmosphere, more conveniently the catalyst of the invention is the same as that used for propylene oxidation. Preparation may be carried out in a reactor.

This can be done, for example, by adding the system to an aqueous medium in a commercially available reactor, flushing the system with propylene gas, and then heating the mixture under propylene pressure until the temperature desired for catalyst preparation is reached, during which time the oxygen is removed again. This is conveniently accomplished by stirring the mixture at that temperature for at least 30 minutes in the presence of olefin and preferably in the presence of a slight excess of olefin.

After preparation of the catalyst, the propylene is replaced by a mixture of propylene and oxygen, preferably oxygen is added to the liquid medium. The oxidation reaction is carried out at a pressure of about 1-10 atmospheres.

Pressure is maintained by adding additional cass mixture from time to time until the desired propylene conversion is achieved. Air can be used instead of oxygen, but in this case the amount of propylene must be adjusted accordingly.

The activator of the catalyst is preferably propylene, but if desired may be substituted with furyl hydrogen and other light olefins containing from 3 to 6 carbon atoms, preferably corresponding to the olefin to be oxidized. It can be used for. Most preferably, besides propylene, butene-11butene-2 or isobutylene is used.

The olefin-activated catalyst -f;-tDU44 remains active for long periods of time as long as at least a small amount of acceptable olefin is present. It has therefore been found advantageous to carry out the reaction by constantly sparging the propylene/oxygen or air reaction mixture through the aqueous solution. By this method propylene is kept in excess and the catalyst remains highly active thereby preserving high selectivity and other advantages mentioned above.

When the oxidation is carried out batchwise, the ratio of catalyst to reaction medium desirably ranges from about 0.05 to about 5.0 gram atoms of palladium per liter of reactant, preferably about 0.0.
It is in the range of 1-1.0 gram atom.

In a continuous process using, for example, a fixed bed reactor, the reaction is carried out in a manner known in the art to achieve the high yields and selectivities described herein. It can be implemented effectively by making changes.

Good selectivity for many acids, generally known to those skilled in the art, makes the use of these inhibitors a superior method for the oxidation of propylene to acrylic acid. In the absence of these inhibitors, selectivity typically ranges from about 8θ to 85χ, but as shown in Table 1,
For example, the introduction of BIIT surprisingly reduced the selectivity to about 92
It can be increased to ~93X. The free radical inhibitor can be added to the liquid medium at any time, ie, before or after activation.

In addition to butylated hydroxytoluene (BIT), 2.
Compounds of sulfur-containing metal chelates such as 2'-methylenehis (tomethyl-6-tert-butylphenol), hydroquinone, zinc dithiocarbamate and zinc dithiophosphate can be used.

The following examples illustrate the invention.

The amount of free radical inhibitor used generally ranges from about 0,000 to 1,000 per liter of aqueous medium. θg, preferably about 0.01-0.5 g.

Examples 1-6 In the following Examples 1-6, several reactions were carried out according to the following general procedure.

18 on carbon (Ingelhard Industries)
IO! Palladium metal was added to an 85 ml Fisher-Porter Aerosol tube. Next, 301 degassed distilled water was added and the Fischer-Porter tube was attached to the pressure manifold. The amounts indicated in the SET table were then added.

Mixture with pure propylene gas (research purity grade)
Flushed 3 times at psi. This mixture of pure propylene with stirring was then placed under 50 psi of pure propylene to a total pressure of 100 psig. In most cases the reaction proceeded immediately and the pressure dropped. When the total pressure reached 80 psig, the O2/C386 gas mixture was turned on to bring the total pressure to 100 psig. This was repeated as often as necessary during the course of the experiment. After the measured reaction time, the mixture was cooled, the gas was captured and analyzed, and the mixture was filtered. The catalyst was washed with both organic and aqueous solutions to remove the acrylic acid retained on the surface. The filtrate was analyzed by standard Cass chromatography to determine product composition.

The results are shown in Table 1 below along with certain changes in reaction conditions. In some of the examples, where indicated, the catalyst was first washed with base to remove any remaining traces of chloride ions from the commercial preparation.

Example 7 The reaction was carried out according to the procedure of Example 30 except that propylene was replaced with isobutylene to give methacrylic acid as the major product.

Example 8 The reaction was carried out according to the procedure of Example 3 except that propylene was replaced with butene-1 to give crotonic acid as the major product.

Claims (1)

[Claims] 1. oxidizing a C3-C6 olefin mixed with air or oxygen in a liquid medium in the presence of a free radical inhibitor in the presence of an activated palladium metal catalyst, by contacting a palladium metal catalyst, the catalyst supported in the liquid medium, with the above or different C3-C6 olefin at a temperature of at least about 60°C for at least about 10 minutes in the substantial absence of oxygen. A method for producing an α,β-unsaturated carboxylic acid which is activated or which comprises performing the above-mentioned oxidation after activation. 2. First, supported palladium metal catalyst C3-C6
at least about 60°C in the olefin and liquid medium.
for at least about 10 minutes in the substantial absence of oxygen, and thereafter the activated catalyst is activated in the liquid medium in the presence of a free radical inhibitor. 63 above mixed with air or oxygen
α consisting of contacting with a ~C6 olefin, thereby oxidizing said olefin to the corresponding carboxylic acid. Claim 1: Producing β-unsaturated carboxylic acid
The method described in section. 3. The method of claim 2, wherein the catalyst is activated essentially in the absence of oxygen. 4. A process according to claim 2, wherein the catalyst is kept in an activated state by continuous contact with said olefin. 5. The process of claim 2, wherein the catalyst is activated with said olefin at a pressure of about 1 to 100 atmospheres. 6. The method of claim 2, wherein the catalyst is activated with said olefin at a temperature of about 60<0>C to 150<0>C for at least 10 to 120 minutes. 7. The method according to claim 2, wherein the olefin is propylene and the carboxylic acid is acrylic acid. 8. The method according to claim 2, wherein the olefin is isobutylene and the carboxylic acid is methacrylic acid. 9. The method according to claim 2, wherein the olefin is butene-1 and the carboxylic acid is crotonic acid. 10. The process of claim 2, wherein the oxidation is carried out with the stoichiometric amounts of olefin and oxygen required to produce the α,β-unsaturated carboxylic acid. 11. The method according to claim 2, wherein the support for palladium metal is carbon or alumina. 12. The method of claim 2, wherein the oxidation is conducted at a temperature of at least about 25°C. 13. The method according to claim 2, wherein the free radical inhibitor is butylated hydroxytoluene. 14. The method of claim 2, wherein the free radical inhibitor is 2,2'-methylenebis(4-methyl-6-tert-butylphenol). 15. The method of claim 2, wherein the amount of free radical inhibitor used is about 0.001 to 1.0 g per liter of aqueous medium. 16. oxidizing a C3-C6 olefin mixed with air or oxygen in a liquid medium in the presence of a free radical inhibitor in the presence of an activated palladium metal catalyst, said catalyst being in said liquid medium; is activated by contacting the supported palladium metal catalyst with the C3-C6 olefin at a temperature of at least about 60° C. for at least about 10 minutes in the substantial absence of oxygen. A method according to claim 1 for producing α,β-unsaturated carbonic acids. 17. The method of claim 16, wherein the catalyst is activated essentially in the absence of oxygen. 18. The method of claim 16, wherein the catalyst is maintained in an activated state by continuous contact with said olefin. 19. The method according to claim 16, wherein the olefin is propylene and the carboxylic acid is acrylic acid. 20. The method according to claim 16, wherein the olefin is isobutylene and the carboxylic acid is methacrylic acid. 21. The method according to claim 16, wherein the olefin is butene-1 and the carboxylic acid is crotonic acid. 22. The process of claim 16, wherein the oxidation is carried out with the stoichiometric amounts of olefin and oxygen required to produce the alpha,beta-unsaturated carboxylic acid. 23. The method according to claim 16, wherein the support for palladium metal is carbon or alumina. 24. Claim 1, wherein the catalyst is activated with said olefin to pressurize said olefin to about 1 to 100 atmospheres.
The method described in Section 6. 25. The method of claim 16, wherein the catalyst is activated with the olefin at a temperature of about 60<0>C to 150<0>C for at least about 10 to 120 minutes. 26. The method of claim 16, wherein the oxidation is conducted at at least about 25°C. 27. The method of claim 16, wherein the free radical inhibitor is butylated hydroxytoluene. 28. The method of claim 16, wherein the free radical inhibitor is 2,2'-methylenebis(4-methyl-6-4crt-butylphenol). 29. The method of claim 16, wherein the amount of free radical inhibitor used is about 0.001 to 1.08 per liter of aqueous medium. 30. First, supported palladium metal catalyst C3-C
6 olefin and in a liquid medium, at least about 60
C. for at least about 10 minutes, and thereafter the activated catalyst is activated in the liquid medium in the presence of a free radical inhibitor. and different C3-C6 olefins mixed with air or oxygen, thereby oxidizing said olefins to the corresponding carboxylic acids.
, Claim 1 for producing β-unsaturated carboxylic acid
The method described in section. 31. The method of claim 30, wherein the catalyst is activated essentially in the absence of oxygen. 32. Claim 30, wherein the catalyst is kept in an activated state by continuous contact with said olefin to be oxidized.
The method described in section. 33. The process of claim 30, wherein the catalyst is activated with said olefin at a pressure of iq+ of said olefin - 100 atmospheres. 34. The method of claim 30, wherein the catalyst is activated with the olefin at a temperature of about 60<0>C to 150<0>C for at least 10 to 120 minutes. 35. oxidizing a C3-C6 olefin mixed with air or oxygen in a liquid medium in the presence of a free radical inhibitor in the presence of an activated palladium metal catalyst, said catalyst being in said liquid medium; a palladium metal catalyst supported by a C3-C6 olefin with at least about 60
Claim 1, wherein the .alpha.,.beta.-unsaturated carboxylic acid is activated by contacting in the substantial absence of oxygen for at least about 10 minutes at a temperature of "C". 36. The method of claim 35, wherein the catalyst is activated essentially in the absence of oxygen. 37. The method of claim 35, wherein the catalyst is activated by continuous contact with the olefin in which the catalyst is oxidized. Claim 35 maintained in activated state
The method described in section. 38. Claim 3, wherein the catalyst is activated with said olefin under a pressure of about 1 to 100 atmospheres.
The method described in Section 5. 39. The method of claim 35, wherein the catalyst is activated with said olefin at a temperature of about 60<0>C to 150<0>C for at least 10 to 120 minutes.