Selective liquid phase air oxidation of toluene catalysed by...

Details Selective liquid phase air oxidation of toluene catalysed by... Selective liquid phase air oxidation of toluene catalysed by...

2002-03-28

2004-06-01

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S815000, C562S409000

Reexamination Certificate

active

06743952

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the production of benzaldehyde with 40-50% selectivity by catalytic liquid phase air oxidation of toluene using a composite catalytic system.
The N.F./F.C.C. grade of benzaldehyde is widely used in flavors such as almond and cherry and in various fragrances for soap and toiletries. Benzaldehyde is an F.D.A. sanctioned synthetic flavoring substance generally recognized as safe for food. The technical grade is a versatile chemical intermediate in the manufacture of pharmaceuticals, dyes, perfume and flavoring chemicals. The technical grade of benzoic acid is used as at intermediate in the manufacture of chemicals, alkyd resins, polyesters, plasticizers, dyestuffs, preservatives, and rubber activators and retardants. Benzoic acid, industrial grade, is used as a chemical intermediate and as a diverting agent in crude oil recovery applications.
BACKGROUND AND PRIOR ART OF THE INVENTION
Benzaldehyde is currently produced by the hydrolysis of the corresponding side chain halogenated toluene compound. Reference may be made to a patent U.S. Pat. No. 4,229,379, Oct. 21, 1980, wherein benzaldehyde is prepared by hydrolysis of benzyl chloride at 100-200° C. at normal or under increased pressures in the presence of an excessive aqueous hydrochloric acid. Reference may be made to another patent, U.S. Pat. No. 4,450,298, May 22, 1994, wherein vapour phase catalytic hydrolysis of benzylchloride to form benzaldehyde by using activated carbon treated with H
2
SO
4
or impregnated with a metal chloride such as FeCl
3
or a metal sulphate such as cupric sulphate. The drawbacks in the above processes are generation of large excess of effluents and the benzaldehyde produced does not meet food grade specifications.
Air oxidation of toluene and its derivatives offers green technology path provided the desired selectivities are realised for market driven products and minimisation of halogenated and unwanted by-products causing effluents is achieved. Several patents have been filed describing innovation in air oxidation of toluene and its derivatives both in liquid and vapour phase.
One of the prevalent industrial practices for the vapour phase oxidation of toluene to benzaldehyde involves a uranium oxide/molybdenum oxide catalyst at 500-600° C. (W. L. Faith, D. B. Keyes and R. L. Clark, Industrial Chemicals, 3
rd
Ed., John Wiley & Sons, Inc., New York, 1965; U.S. Pat. No. 3,579,589). Reference may be made to a patent, U.S. Pat. No. 3,946,067, wherein a process is described for the preparation of aromatic aldehydes such as benzaldehyde or substituted benzaldehydes involving the vapour phase oxidation of aralkyl compounds such as toluene or substituted toluenes, respectively, at temperatures of less than ~250° C. in the presence of a catalyst composition containing phosphoric acid and a catalytically effective amount of palladium metal. The aromatic aldehydes are produced in a single reaction step. The drawbacks in this process are the conversion of toluene has to be kept very low <4% to attain high selectivity (>70%) of benzaldehyde and significant amount of carbon dioxide is also formed in this process.
Reference may be made to another patent, U.S. Pat. No. 3,989,674, Nov. 2, 1976, wherein a mixture of toluene, oxygen and a helium diluent in molar ratio 1:2:8 is passed over the Cu— Au— silica catalyst at atmospheric pressure and temperatures in the range of 450-600° F. with 200-1000 volumes of gas/h/volume of catalyst. The selectivity of benzaldehyde is 75-80% at conversion levels 15-30%. Reference may be made to another patent, U.S. Pat. No. 4,137,259, Jan. 30, 1979, wherein a process for the vapour phase catalytic oxidation of toluene to benzaldehyde and benzoic acid at a temperature ranging from 300-500° C. in the presence of a silver-iron vanadate on silica with conversion 21%, selectivity to aldehyde 33% is described. Reference may be made to a patent U.S. Pat. No. 4,390,728, Jun. 28, 1983, wherein benzaldehyde is formed by the oxidation of toluene in the presence of a catalyst composed of the oxides of Cu, Fe, Pb, U, Mo, and P, which can also include some other promoter elements. The reaction conditions are 475-550° C., 0-10 atm. pressure, per pass conversion is 35-50%, selectivity to benzaldehyde 40-70%. Reference may be made to a publication by Ray et al, Ind. J. Technol., 21(4), 137, 1983, where they have reported a process for the oxidation of toluene to benzaldehyde. But, the conversion per pass is restricted to ~15% and the yield of benzaldehyde is generally not more than 70%, with CO
2
as main product. Further, the low concentration of toluene in the toluene-air feed mixture poses problems of recovery. The drawbacks in the above processes are the use of higher reaction temperatures, generation of carbon dioxide in large amounts contributing global warming. Therefore, these processes do not appear to be attractive.
Reference may be made to U.S. Pat. No. 5,476,827, Dec. 19, 1995, wherein aldehydes are prepared by the reduction of acids, esters in vapour phase in the presence of a bimetallic catalyst. The drawback is two-step process of oxidation of toluene, a desired raw material to benzoic acid and reduction of benzoic acid to benzaldehyde with hydrogen. Eventually, this process becomes uneconomical, when compared to a process of selective oxidation of toluene to benzaldehyde.
Reference may be made to a publication by Morimoto et al (J. Chem. Soc. Sect. B, 62, 1967), Fields et al (Adv. Chem. Ser., No. 76(2), 395) and Kamiya (Adv. Chem. Ser., No. 76(2), 193, 1968), they have reported that liquid phase air oxidation provides high yield of benzaldehyde when oxidation is carried out in acetic acid medium with cobalt acetate as catalyst and sodium bromide as promoter. The drawbacks are that this process suffers from the disadvantages of relatively low yield. Reference may be made to U.S. Pat. No. 2,959,613, wherein the liquid phase oxidation of toluene or its nucleus substituted materials of toluene such as xylene is carried out by oxygen under the presence of a catalyser containing a bromine compound and a heavy metallic compound (such as cobalt compound or manganese compound) along with a zinc compound or an alkaline earth metallic compound or an alkaline metallic compound. The drawbacks in this method are that the main product is the corresponding aromatic carbonic acid and either there is absolutely no production of the corresponding aromatic aldehyde or it is produced in a very small quantity as a by-product.
Reference may be made to Japanese patent No. SHO-53-5132, wherein in order to increase the selectivity of benzaldehyde or its nucleus substituted material, a large quantity of catalyser containing a cobalt compound and bromine compound is used. Reference may be made to another Japanese patent No. SHO-56-108728, Aug. 28, 1981, wherein the liquid phase air oxidation of toluene is carried out by a catalyst composing a heavy metallic compound, zinc and bromine compound at 30-180° C. and low pressure. The transformation percentage of toluene is maintained within a specific range with the advantage of the execution of the reaction employing carboxylic acid as solvent in the range 0.5-2.0 times with respect to toluene or its substituted material. By this method the selectivity of benzaldehyde is increased while formation of benzyl bromide is reduced to 2 mol %. However, the turn over number is 3-50 in these air oxidation reactions. The drawbacks in the above processes are low turn over numbers render the process uneconomical, the use of higher catalyst concentration hasten corrosion of reactors and excessive production of benzyl bromide is detrimental to the achieve desired quality of the product. Reference may be made to U.S. Pat. No. 3,969,405 wherein the oxidation of toluene in the presence of cobalt acetate, acid activator and molecular oxygen oxidant gives high yield of benzoic acid with selectivity to benzaldehyde 35%. Reference may be made to U.S. Pat. No. 5,473,101 wherein the oxidation of toluene is carri

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