DE1226544B - Process for the production of catalysts for the production of phthalic anhydride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

BOIj

German KL: 12 g-11/56

Number: 1226 544

File number: B 74730IV a / 12 g

Filing date: December 19, 1963

Opening day: October 13, 1966

It is known that catalysts can be prepared if particles of a catalytic substance are mixed with porous carrier particles at a temperature at which the catalytic substances melt, optionally in a fluidized bed, and the carrier particles are in motion until the catalytic substance is taken up by the carrier particles holds. Vanadium pentoxide-potassium pyrosulfate mixtures, such as those used, for. B. be used for the oxidation of naphthalene with air, depending on the melt composition is between about 200 and 37o ⁰ C. Accordingly, it turns in the known processes for the production of vanadium pentoxide-potassium pyrosulfate catalysts on silica gel as support temperatures up to 500 ⁰ C. at. If one tries to produce vanadium pentoxide-potassium pyrosulphate catalysts on titanium dioxide supports within this known temperature range, it is found that the titanium dioxide supports are not wetted by the vanadium pentoxide-potassium pyrosulphate melt.

It has now been found that catalysts for the production of phthalic anhydride, in which a melt is applied a mixture of vanadium pentoxide-Alkalipyrosulfat and optionally additives at temperatures up to 500 ⁰ C on a porous Metalloxydträger, very advantageously obtained when as carrier titanium dioxide particles with an inner surface of 2 to 50 m ² / g is used and up to 650 ° C brings the mixture of the active components with the carrier substance above 500 ⁰ C, particularly at 550 contact each other.

Catalysts produced in this way are particularly suitable for the production of phthalic anhydride from o-xylene, particularly suitable in the fluidized bed.

The titanium dioxide is used in a form, which is an inner surface m of 2 to 50 ² / g, especially from 2 to 30m ² / g comprising. Depending on the type of use, it is used in the form of larger or smaller particles. If the catalyst is to be used as a fluidized catalyst, particle sizes from 0.06 to about 0.5 mm are used.

The active mixture containing vanadium pentoxide and alkali pyrosulfate is prepared in a manner known per se, e.g. B. the alkali pyrosulphate or alkali hydrogen sulphate or mixtures of several alkali pyrosulphates or alkali hydrogen sulphates, optionally together with water, heated and melted until the water has evaporated; then be dissolved in particular vanadium pentoxide or ammonium vanadate and optionally the additives in the melt at about 300 to 450 ⁰ C, the vanadium compounds. Used as alkali pyrosulfates for the preparation of catalysts for processes
the extraction of phthalic anhydride

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Wilhelm Friedrichsen, Ludwigshafen / Rhine

one sodium, potassium pyrosulphate or mixtures of these compounds. Potassium pyrosulfate is preferred and sodium-potassium pyrosulfate mixtures, in particular with 10 to 50 percent by weight sodium pyrosulfate, used.

In addition to those already mentioned, other vanadium compounds can also be added which convert to vanadium pentoxide under oxidizing conditions at the reaction temperature, e.g. B. Vanadium (III) chloride, vanadium (III) oxide, vanadium (IV) oxide or vanadyl sulfate, VOSO ₄ .

As further additives to the vanadium pentoxide, phosphoric acid, molybdenum trioxide and or or tungsten oxide is used, where the phosphoric acid as such or in the form of phosphorus pentoxide or can be admixed in the form of compounds which provide phosphoric acid. Man can also be phosphorus pentasulfide, ammonium phosphate, sodium or potassium phosphates as primary, use secondary or tertiary phosphates. When using alkali phosphates one must dem Alkali corresponding amount of sulfuric acid is added and taken into account as pyrosulphate. The phosphorus compounds are added in such an amount that a maximum of 4 percent by weight of phosphorus pentoxide are present in the pyrosulphate melt. The weight ratio of phosphorus pentoxide to vanadium pentoxide can be between 1: 6 and 1: 200.

The optionally added molybdenum compounds are z. B. in the form of molybdic acid, Molybdenum oxide, molybdenum sulfide or ammonium molybdate are used. But you can also use sodium or Use potassium molybdate or, advantageously, phosphomolybdic acid. The content of alkalis is expediently compensated by adding sulfuric acid. The alkali and / or phosphorus

609 670/392

content of the added molybdenum compounds is in the amount of Pyrosulfat'bzw. Phosphoric acid to be considered.

Instead of the molybdenum compounds, tungsten compounds can be added, for example tungstic acid, tungsten oxides, tungsten sulfides, ammonium tungstate or phosphotungstic acid: mixtures of molybdenum and tungsten compounds can also be added. The molybdenum and / or WoKramverbindüngen ¹ "are added in an amount that their proportion of the melt containing vanadium pentoxide and alkali pyrosulfate is up to 6 percent by weight of molybdenum trioxide (or an equivalent amount of tungsten trioxide) and the weight ratio of molybdenum or tungsten oxide to vanadium oxide 1 : 3 to 1:20.

By a further addition, for example from 1 to 10 percent by weight of silver oxide, based on Vanadium pentoxide, can be the catalysts for the. Further improve o-xylene oxidation.

It is expedient to prepare the pyrosulfate melt containing vanadium pentoxide and optionally additives of the type mentioned in the desired mixing ratio, to allow it to solidify, to comminute and then to apply it to the carrier. . For applying the. Vanadine pentoxide and other. If necessary, additives containing pyrosulphate melts on .the carrier substance can be used various methods. For example, one can mix to a particle size of about 200 μ or less milled solidified melt with the appropriate amount and then Titandioxydträger mehrere'Stunden to temperatures above 500 ⁰ C, for a mixing drum. B. 550 to 600 ⁰ C, heat. The liquefying melt is absorbed by the pores of the carrier material. The carrier is expediently kept in motion for even distribution of the melt. This can be done, for example, in a heated stirred tank or in a heated screw conveyor. Another method is that the powdered melt in the with air or an inert gas, z. B. nitrogen or carbon dioxide, in a whirling motion can trickle titanium dioxide and for a while, z. B. 8 hours, left at the said temperature. To homogenize the catalyst, it can be kept in swirling motion for some time before use at the reaction temperature in a stream of air or in a stream of gas containing oxygen.

The quantitative ratio between the pyrosulphate melt, which contains vanadium pentoxide and any additives, and vehicle may vary. It is advantageous at least 10 percent by weight of this melt, based on the catalyst applied. The use of 10 to 50 percent by weight is preferred, in particular 12 to 35 percent by weight of melt mixture, based on the catalyst.

The use of the catalysts prepared according to the invention in the o-xylene oxidation to phthalic anhydride takes place under known conditions. Passing the oxidation advantageously at 270 to 42O ⁰ C, preferably at 300 to 380 ⁰ G, - from. However, the reaction temperature must be selected to be so high that the active catalyst constituents are in liquid form in the carrier.

The catalysts of the invention are not only for o-xylene oxidation but also for other processes z. B. naphthalene and benzene oxidation, useful.

example 1
A. Catalyst manufacture

863 parts of titanium dioxide in the form of hollow spheres, produced by spraying hydrolysed ^; Titanium tetrachloride mm and with a grain size of 0.2 to 0.6 of an inner surface of 9.8 m ² / g of a finely ground, melt prepared at 400 ⁰ C of 15% vanadium pentoxide and 85 ° / ₀ potassium pyrosulfate well with 140 parts mixed and heated in a muffle furnace to 600 ° C for 3 hours, after which the evenly soaked catalyst is sieved to separate individual, slightly caked parts.

B. Use of the catalyst
for o-xylene oxidation

^{920 cm 3 of} the catalyst as described above are placed in a 1 m long, difficult-to-melt glass tube with an internal width of 42 mm, which is filled with wire spirals for better distribution of the gas C. 22.8 g / h of vaporous o-xylene with 700 l of air are passed through the swirling catalyst after condensation of the hot vapors, 22.6 g of phthalic anhydride and 1.4 g of maleic acid are obtained per hour of phthalic anhydride 99%> is in accordance with 71 ° / ₀ of theory.

Example2;

For comparison, a catalyst consisting of ^: silica gel with an internal surface area of 350 m ² / g 'is produced.

893 parts of silica gel are intimately mixed with 600 parts of ground melt, as described in Example 1, and the mixture is kept in a whirling motion ^{with a stream of air in a quartz tube at 450 ° C. for 3 hours.} The melt is then taken up by the carrier. As in Example 1 of this catalyst are ¹ hour at 370 ° C by 700 cm ³ 15 g of o-xylene fed in the vapor state with 6001 air. 9 g of phthalic anhydride and 1.1 g of maleic anhydride are obtained per hour. The weight yield is 60 ° / ₀ , corresponding to 43 ° / ₀ of theory.

In this comparative example, the melt-in applied in an amount which gives the best yields. When using a smaller amount it falls the yield drops sharply; if larger quantities of the melt are used, the catalyst will stick together a.

Claims (1)

Claim: Process for the preparation of catalysts for the production of phthalic anhydride, in which a melt of a mixture of vanadium pentoxide-alkali metal pyrosulfate and optionally additives at temperatures up to 500 ° C is applied to a porous metal oxide support, characterized in that the support is titanium dioxide particles with an inner surface from 2 to 50 m ² / g is used and up to 650 ° C brings the mixture of the active components with the carrier substance above 500 ⁰ C, particularly at 550 contact each other. Considered publications:
German publication No. 1122 929. 609 670/392 10.66 © Bundesdruckerei Berlin