IL26813A

IL26813A - Process for the catalytic oxidation of toluene with oxygen,in the gaseous phase,to benzaldehyde and catalyst therefor

Info

Publication number: IL26813A
Application number: IL26813A
Authority: IL
Original assignee: Stamicarbon
Priority date: 1965-11-12
Filing date: 1966-11-07
Publication date: 1970-05-21
Also published as: FR1498896A; ES333272A1; NL6514683A; DE1294951B; CH481857A; GB1164316A; BE689424A; AT268253B; SE326170B; NL144573B

Description

26813/2 Process for the catalytic oxidation of toluene with oxygen, in the gaseous phase, to benzaldehyde and catalyst therefor STAMICASBON N.V. , C. 25489 This invention relates to the gaseous catalytic oxidation of toluene with oxygen or ozone, to benzaldehyde and/or benzoic acid, and to ; catalysts for use therein. P//Known catalysts for use in the above reaction include oxidic catalysts based on for example oxides of the metals aluminium, antimony, bismuth, cerium, chromium, silver, cobalt, magnesium, molybdenum, tin, titanium, tungsten, uranium, vanadium and zinc, or mixtures thereof, e.g. a mixture of 93 % uranium oxide and 7 % molybdenum oxide, possibly with a slight admixture of copper oxide. Other catalysts hitherto recommended for the oxidation of toluene are salts of vanadates, molybdates, chromates,uranates, stannates, in the form of copper, silver, lead, thallium, platinum, cerium, nickel and cobalt salts. The suitability of any particular catalyst is evaluated with reference to inter alia its activity and selectivity. The activity determines the degree of conversion, i.e. the percentage of starting material that is converted into other products. The selectivity determines the yield of desired product in the products obtained by the conversion.

Among the catalysts so far suggested for use in the oxidation of toluene to benzaldehyde, catalysts based on silver vanadate are prefer-red because such: catalysts combine a reasonably good activity with a particularly good selectivity, in that only a small proportion of of the oxidized quantity of toluene is converted to worthless carbon dioxide, the remainder consisting substantially of the desired benzaldehyde and benzoic acid.

As regards the gaseous phase oxidation of toluene with oxygen or ozone it has now been found that a catalyst based on silver vanadate can be further improved by the incorporation therein of one or more cerite earths vanadate(s) . The presence of vanadate(s) of one or more of the cerite earths results in an increase in the activity of the catalyst, the selectivity Remaining substantially constant. This increase in activity is not to be expected, since in the oxidation of toluene with oxygen or ozone under comparable conditions, a catalyst based on one or more cerite earth vanadate(s) is both less active and less selective than a catalyst based on silver vanadate. An increase in the activity of a catalyst based on the combination of silver vanadate and one or more of the rare earth vanadate(s) is clearly apparent even if the proportions of cerite earths in the combination is small in relation to the amount of silver. Thus a catalyst with a molar ratio of cerite earth/silver of say 1:5 results in an improvement.

The largest improvement in activity is achieved if the molar ratio of cerite earth/silver is about 1:2, but catalysts with a molar ratio of 2: 1 also show a higher activity than a catalyst based on silver vanadate alone.

The catalyst components should be thoroughly mixed, preferably by a coprecipitation technique. It is preferred to apply the catalyst components into a carrier, e.g. an alumina and/or silica carrier.

In the oxidation of toluene using the catalysts according to the invention less than the stoichiometric amount of oxygen or ozone is used, in order to reduce the production of carbon dioxide and water. An optimum result is obtained if the toluene vapour/oxygen volume ratio is approximately 2.

To achieve a selective oxidation the gas/vapour mixture should contain a considerable proportion of steam beside toluene. Toluene/steam volume ratios of about 0.5:1 give good results.

At toluene/steam volume ratios higher than 0.5:1, the formation of by products, such as tolyl-benzaldehyde and ditolyl, and the formation of carbon dioxide, increase sharply. Toluene/steam volume ratios lower than 0.5:1 have no adverse effect on the activity and the selectivity of the catalyst, but in industrial applications it is uneconomical to use more steam than is necessary.

The space velocities of the gas mixture that is to be passed over the catalyst in the catalytic oxidation of toluene can be varied between wide limits. At a toluene content of about 10 %-vol. in the gas mixture, space velocities of from 750 to 10,000 v/v/hour may be employed without having a significant effect on the activity and/or selectivity -of the catalyst. A high space velocity generally has the advantage of yielding a higher daily output, even if the degree of conversion is slightly lower than when using a lower space velocity. The oxidation of toluene is carried out at a temperature in the range of 300 °C to 450 °C, the optimum temperature depending upon the activity of the catalyst.

The products obtained by oxidizing toluene with oxygen or . ozone by means of a catalyst based on the combination silver vanadate and one or more cerite earth vanadate (s), contain a large percentage: of benzaldehyde and benzoic acid, e.g. about 95 % of the total quantity of aldehydes produced consist of benzaldehyde, wMite' about'rSO % of the acids produced from the toluene consist of benzoic acid. The oxidation products formed are separated in a conventional manner, e.g. by condensation and distillation. Unconverted toluene, together with steam and oxygen, may then be recycled over the catalyst.

The following examples illustrate the invention.

Examples 1 and 2 relate to the testing of a catalyst based either on silver vanadate or on one or more of the cerite earth vanadate (s), for use in the oxidation of toluene with oxygen in v the gaseous phase. Examples 3, 4 and 5 relate to the testing of a catalyst according to the invention, i.e. a catalyst containing both silver vanadate and cerite earth vanadate as the catalytically active material .

Example 1 (Not according to the invention) A catalyst mass consisting of 20 %-w of AgVO and 80 %-w of SiO as a carrier therefor was prepared by suspending SiO in an aqueous solution of ammonium metavanadate, adding a silver nitrate solution to said suspension, removing the precipitate by filtration, and drying and calcining the precipitate at 450 °C.

Toluene was oxidized with this catalyst by passing a 2 1 of toluene vapour, 1 1 of oxygen, 3 1 of nitrogen and 12 1 of steam per hour, over 20 ml of the catalyst.

The catalyst mass was kept at 372 °C. Under these conditions 14 % of the toluene was converted.

The composition of the oxidized toluene was 54 % aldehyde, 37 % acid, and 9 % carbon dioxide.

Example 2 (Not according to the invention) A catalyst mass consisting of 20 %-w of Ce(V0 ) , and 80 %-w of SiO as carrier therefor was prepared in the way described in Example 1, but using cerium nitrate instead of silver nitrate. The oxidation of the toluene was carried out under the same experimental conditions, with the difference that the temperature of the catalyst mass was kept at 358 °C. Under these conditions, 7 % of the toluene was converted, the composition of the oxidized toluene being 37 % aldehyde, 47 % acid, and 16 % carbon dioxide.

Example 3 A catalyst mass consisting of 20 %-w of AgVO 20 %-w of Ce(V0 ) and 60 %-w of SiO as carrier therefor, was prepared by adding a silver nitrate solution and a cerium nitrate solution to a suspension of SiO^ in an ammonium metavanadate solution, removing the precipitate by filtration, and drying and calcining the precipitate.

With this catalyst mass, in which the Ag:Ce molar ratio was approximately 2:1, toluene was oxidized under the conditions mentioned in Example 1 at a temperature of 375 °C. Under these conditions, 30 % of the toluene was converted the composition of the oxidized toluene being 43 % aldehyde, 46 % acid, and 11 % carbon dioxide.

Example 4 A catalyst mass consisting of 20. %-w of AgVO , 20 %-w of didymium vanadate, and 60 %-w of 3i0 as carrier therefor, was obtained as in Example 3 by adding solutions of silver nitrate and didymium nitrate to a suspension of Si02 in ammonium metavanadate, removing the precipitate by filtration, and drying and calcining the filtrate. The oxidation of toluene was effected under the o experimental conditions of Example 3 at a temperature of 375 C. Under these conditions 30 % of the toluene was converted; the composition of the oxidized toluene being 36 % aldehyde, 53 % acid, and 11 % carbon dioxide.

Example 5 A catalyst mass consisting of 20 %-w of AgVO , 20 %-w of o La(V0 ) , and 60 %-w SiO as carrier therefor with a Ag/La molar ratio of approximately equal to 2:1 was obtained in the way of Example 3, except that a lanthanium nitrate solution was used instead of a cerium nitrate solution. The gas mixture of Examples 3 and 4 was passed over the catalyst at a temperature of 379 °C. Under these conditions 23 % of the toluene was converted the composition of the oxidized toluene being 42 % aldehyde, 42 % acid, and 16 % carbon dioxide.

The working conditions and the results of the procedures described in the examples are summarized in the accompanying table, from where it can be seen here that with the improved catalyst a considerably higher yield of aldehyde and acid can be obtained than with a catalyst containing as active component only silver vanadate, or only a vanadate of a rare earth.

TABLE Examples according to the invention

Claims

1. HAVINS NOW PARTICULARLY 0ESGN I BED AND ASCERTAINED THE NATURE OF OUR ΒΑΙ» INVENTION ANO IN WHAT ANNERTTHE SAME IS T© BE PERFORMED, WE DECLARE THAT WHAT WE CLAIM IS( A process for the gaseous phase catalytic oxidation of toluene with oxygen or ozone to benzaldehyde and/or benzoic acid, in which the oxidation is carried out in the presence of a catalyst mass containing both silver vanadate and one or more cerite earth vanadate (s) . A process according to claim 1, in which the silver/cerite earth molar ratio in the catalyst mass lies between 5 : 1 and 0.5 :

1. A process according to claim 1 or claim 2, in which the catalyst mass is prepared by coprecipitation of silver vanadate and one or more cerite earth vanadate (s) from an aqueous solution of ammonium metavanadate . A process for the gaseous phase oxidation of toluene with oxygen or ozone as claimed in claim 1, substantially as herein before described . Benzaldehyde and/or benzoic acid produced' by_ a process claimed in any of the preceding claims. A catalyst composition suitable for use in the process claimed in any of claims 1 to 4, comprising silver vanadate, and one or more cerite earth vanadate(s), the catalyst being supported on a. carrier therefor. DATED THIS 6TH DAY SF N0VEM8ER 1966 FOR THE APPLICANT*: