DE1542023C3 - Vanadium and (clay-containing supported catalyst - Google Patents

Description

The main patent relates to a supported catalyst containing vanadium and titanium, obtained by Applying a mixture of finely divided titanium dioxide and the solution of a vanadium compound an inert, non-porous support in such a way that the support after drying in a layer thickness of 0.02 to 2 mm is coated with the active material, which is 1 to 15 percent by weight of vanadium pentoxide and Contains 85 to 99 percent by weight of titanium dioxide, and the finished supported catalyst has a vanadium pentoxide content of 0.05 to 3 percent by weight.

It has now been found that a supported catalyst according to the main patent for the oxidation of aromatic and unsaturated aliphatic hydrocarbons are particularly well suited to their carrier prior to application the mixture of finely divided titanium dioxide and the solution of a vanadium compound with a Oxide of the metals vanadium, molybdenum, tungsten, chromium, titanium and / or iron has been primed.

The new catalyst enables the oxidation of the hydrocarbons to carboxylic acids in particular high yields. In particular, the proportion of by-products is low, resulting from a too extensive Oxidation reaction (combustion) result. The excellent yields can also be achieved then achieve when the starting material is practically completely implemented. The catalyst particularly allows high throughputs and shows practically no loss of activity even after very long operating times. In many cases, the yield increases further, for example by 2 to 5%, even with prolonged operation.

The catalyst is used for a large number of the known oxidation reactions of aromatic and unsaturated aliphatic hydrocarbons to carboxylic acids suitable, for example for the production of acetic acid from propylene, of maleic acid from butadiene, butene- (1), butene- (2) or benzene and for the oxidation of naphthalene to phthalic acid. Methyl-substituted aromatic hydrocarbons can also be used convert into the corresponding aromatic carboxylic acids, such as toluene in benzoic acid, Methylnaphthalenes in naphthoic acids. Particularly good results are obtained with the oxidation of o-xylene to phthalic acid achieved. The catalyst is highly resilient and z. B. in the production of Phthalic anhydride still has a weight yield of over 100 %.

This is surprising because e.g. B. the catalysts described in US Pat. No. 3,177,229, where the carrier receives an aluminum oxide primer before coating with vanadium pentoxide,

ίο only very unsatisfactory yields (according to column 6, Line 74 only 53 percent by weight) result in the oxidation of o-xylene to phthalic anhydride.

Also with the catalysts known from British patent specification 669 999 during their production Tin oxide is added during or after the coating of the carrier with the vanadium compound, the high yields obtained in the manufacture of phthalic anhydride using of the catalysts of the invention are achieved, do not achieve.

Inert materials with a surface area of preferably less than 3 m ² / g, advantageously 0.5 to 2 m ² / g, such as quartz, silica and in particular porcelain, molten aluminum oxide, silicon carbide and molten or sintered silicates are used as non-porous catalyst supports, z. B. aluminum, magnesium, zinc or zirconium silicate. Both synthetic and natural materials can be used. The catalyst support is expediently used in an average particle size between 2 and 10 mm in diameter, advantageously in the form of spheres, pills or cones.

Sometimes it is also beneficial to have smooth surfaces the carrier prior to its use by etching, e.g. B.

with hydrofluoric acid, hydrogen fluoride, ammonium fluoride solution, to slightly roughen the adhesive strength of the to increase active mass.

The porous mass used as a catalyst coating, which in the dry state is 1 to 15 percent by weight Vanadium pentoxide and 85 to 99 percent by weight titanium dioxide is said to be more common Way prepares. For this purpose, for example, finely divided titanium dioxide is impregnated with a solution of a vanadium compound in water or in an organic solvent such as formamide or alcohol, and produces a pulp with a roughly honey-like consistency. The coating of the carrier with the active Mass is also done in the usual way, for example in a coating drum with gradual additions of the pulp, expediently with simultaneous drying with hot air. The coating can also be used in the Wise done that carrier, finely divided titanium dioxide and vanadium compound together with a fusible organic substance above the melting point of this organic substance in a coating drum be mixed. It is advisable to work in the temperature range between 80 and 150 ° C. The active material is used in an amount which is necessary to give the support a layer thickness from 0.02 to 2 mm, in particular 0.05 to 1 mm, the finished catalyst 0.05 to 3, preferably 0.1 to 2 percent by weight, in particular 0.1 to 1 percent by weight of vanadium pentoxide target. To solidify the coating, it is advisable to leave the catalyst on for some time, about V2 to Heat for 10 hours in a stream of air at a higher temperature, about 200 to 600 ° C, until used organic substances are burned.

In addition to vanadium and titanium, the catalyst mass can also contain small amounts of silver, cobalt, nickel, Contain molybdenum, tungsten and / or phosphorus compounds, especially in the form of oxides or Hydroxides. These elements are based, for example, in an amount of 0.1 to 3 percent by weight on the catalyst coating.

The main feature of the new process is before coating the carrier with the vanadium pentoxide and titanium dioxide-containing mass the carrier with an oxide of the metals vanadium, To prime molybdenum, tungsten, chromium, titanium or iron or a mixture of these oxides. Man uses the oxides generally in an amount of 0.05 to 1.5 percent by weight, in particular 0.1 up to 1 percent by weight, based on the catalyst.

For this purpose, the oxides mentioned or compounds of the metals mentioned, which are converted into oxides on heating, optionally in the presence of air, are brought into contact with the carrier in a melt or preferably in solution, so that a uniform layer is formed on the carrier. Suitable compounds of the metals mentioned are, for example, organic or inorganic salts and chelate complexes. Examples include: vanadium chlorides, vanadium oxytrichloride, vanadyl oxalate, ammonium vanadinate, ammonium molybdate, molybdenum pentachloride, ammonium tungstate, ethanolammonium tungstate, phosphotungstic acid, ammonium chromate, iron phosphate, titanyl sulfate, titanium phosphate, iron phosphate. The metal compounds are expediently used in solution in water, ammonium thiocyanate or in an organic solvent such as urea, thiourea or alcohols. In order to achieve sufficient strength of the primer and to achieve good adhesion of the subsequent coating, it is expedient to heat the substrate to a temperature between 300 and 1000 ^° C. before coating, ie after priming.

The oxidation reactions are carried out in the usual way, ie in the gas phase using oxygen-containing gases or oxygen and under normal, reduced or increased pressure at temperatures between approximately 250 and 600 ^° C.

For example, 1

7 g of titanium tetrachloride are dissolved in 20 ecm of glacial acetic acid with cooling. The resulting solution is evenly distributed in a drum on 250 ecm of molten aluminum oxide with a grain size of 4 to 6 mm. The carrier treated in this way is dried in a stream of air. Subsequently, the gloss coating (titania) is fixed by two hours at 400 ⁰ C muffles.

The carrier pretreated in this way is brought into contact with a paste prepared from a solution of 40 g of vanadyl oxalate in 40 ecm of formamide and 75 ecm of water with the addition of 270 g of anatase. The excess slurry is removed by shaking on a sieve and the catalyst is first heated slowly to 200 ° C and gemuffelt followed by 5 hours at 400 ⁰ C. It contains 5% active mass and a content of 0.5% vanadium pentoxide.

The finished catalyst is poured into a tube, 80 cm long and heated by a salt bath, with an inner diameter of 25 mm. At 400 ° C., 41 g of 98% strength o-xylene per hour are passed over the catalyst with 11001 air. 42.2 g of phthalic anhydride and 3.5 g of maleic anhydride are obtained per hour. Calculated on pure o-xylene, the weight yield of phthalic anhydride is 105%. The theoretical yield is 75.1 %.

At game 2

250 cc of porcelain balls having a diameter of 5 mm are wetted with a solution of 20 g of vanadyl oxalate in 10 g formamide and 10 g of urea by shaking in a vessel and heated at 200 ⁰ C to the evaporation of the solvent. Then the balls are gemuffelt 30 minutes at 700 ⁰ C. This process is repeated a second time. Then there is a layer of 0.4 percent by weight vanadium pentoxide on the porcelain balls.

The carrier pretreated in this way is then, as described in Example 1, with the vanadium oxalate-titanium dioxide pulp coated. The finished catalyst contains 3.3% active mass. The total vanadium pentoxide content is 0.49%.

In the oxidation of o-xylene under the same conditions as in Example 1 at 410 ^° C., the catalyst provides 45.7 g of phthalic anhydride and 2.8 g of maleic anhydride per hour. The weight yield of phthalic anhydride, based on pure o-xylene, is 113.6%. The theoretical yield is 81.5%. Without pretreatment of the porcelain balls with vanadium pentoxide, the weight yield is 112.5%. If the porcelain balls are pretreated with a solution of iron acetate and chromium acetate in an analogous manner, so that they have a primer of 0.2 percent by weight of chromium oxide and 0.2 percent by weight of iron oxide, and then coated with titanium dioxide-vanadium pentoxide in the above-mentioned manner, at o-xylene oxidation resulted in a weight yield of phthalic anhydride of 113.4%.

Example 3

5 g of molybdic acid are dissolved in a mixture of 8 ecm of ethanolamine, 2 ecm of water and 10 g of urea and made up to 20 ecm with formamide. 469 g of steatite balls having a diameter of 5.5 mm with shaking at 10 cc of this solution, wetted, at 200 ⁰ C dried and gemuffelt 15 minutes at 83O ° C. The amount of molybdic acid applied is 0.7 g. These spheres are then pretreated as described in Example 1, coated with the active Vanadinoxalat-titanium dioxide mass, dried and gemuffelt 4 hours at 400 ⁰ C. The finished catalyst contains 5.8% active mass and 0.35% vanadium pentoxide.

In the o-xylene oxidation at 410 ^° C., the catalyst prepared in this way (under the conditions of Example 1) gives 2.3 g of maleic anhydride and 46.2 g of phthalic anhydride per hour. Based on pure o-xylene, the weight yield of phthalic anhydride is 114.8%. The theoretical yield is 82.4%.

An analogous result is achieved if the carrier is replaced by molybdic acid with the same weight Tungstic acid is primed.

Claims (1)

Claim: Vanadium- and titanium-containing supported catalyst, obtained by applying a mixture of finely divided titanium dioxide and the solution of a vanadium compound on an inert, non-porous Carrier in such a way that the carrier after drying in a layer thickness of 0.02 to 2 mm with of the active composition is coated, which is 1 to 15 percent by weight vanadium pentoxide and 85 to 99 percent by weight Contains titanium dioxide, and the finished supported catalyst contains vanadium pentoxide from 0.05 to 3 percent by weight, according to patent 1 442590, characterized by a carrier, which before the application of the mixture of finely divided titanium dioxide and the Solution of a vanadium compound with an oxide of the metals vanadium, molybdenum, tungsten, Chromium, titanium and / or iron has been primed.