DE1642907A1 - Process for the preparation of vanadium-containing catalysts - Google Patents

Description

Process for the preparation of vanadium-containing catalysts.

The invention relates to a method for the production of vanadium-containing Catalysts for the vapor phase oxidation of aromatic hydrocarbons and the catalysts obtained by this process.

In particular, the invention relates to a method of manufacture of catalysts containing vanadium oxide for the vapor phase oxidation of naphthalene Phthalic anhydride and the catalysts obtained by this process.

They have already been extensive, stretching over a few decades Investigations on Catalysts for the vapor phase oxidation of naphthalene to phthalic anhydride, and numerous patents have been issued on it the procedures for their production are granted.

In general, according to the prior art, fixed bed reactors the application of catalytically active compounds, natural or synthetic inert carriers such as clay, silica gel, carborundum, pumice stone, etc. are provided. the Oxidation generally occurs on the surface of the support.

In fluidized bed reactors, the mixing or mixed precipitation is catalytic effective substances with aqueous gels of silica or clay and drying and calcination of the variously treated mixtures are known. The oxidation takes place mainly in the pores of the catalyst pills.

Recently there has been another way of making fluid bed catalysts trodden, namely the impregnation of the porous carrier with the molten one Mass of active substances at 350 to 4000C, this method of operation is in the British Patent specification 906 311 and in German patent specification 1,148,225.

The present invention relates to a method for producing Vanadium catalysts for the vapor phase oxidation of aromatic hydrocarbons, in particular from naphthalene to phthalic anhydride as well as those according to this process obtained catalysts.

Naphthalene is understood to mean both the chemically pure product and also technical naphthalene, thionaphthene, methylnaphthalene and generally the Contains homologues of naphthalene, indane, etc. in varying proportions.

The preparation of the catalysts which are an object of the present invention Invention is carried out because porous supports, depending on the specific conditions of the oxidation process are selected at room temperature in appropriately calculated Ratios, with solutions containing an appropriate concentration of active or activatable Substances have to be impregnated, whereupon the obtained mass is dried and is calcined, whereby the active components on the inner surfaces of the Pores adhere without closing the outer openings.

In particular, the invention relates to a method of manufacture of catalysts for the vapor phase oxidation of naphthalene on the basis of vanadium-containing active substances; the procedure is through characterized in that an aqueous solution containing V204, SO3 and K20 in molar ratios contains between 1: 6 s 2 and 1 s 10: 6, preferably from 1 s 8 t 4, on one natural or artificial porous support is absorbed at 100 to 900C, whereupon the impregnated carrier is calcined in a stream of air.

Commercially available substances can be used as active substances according to the invention Use substances in any valency state, also in combination with others Elements and groups of elements that are volatile at the calcination temperature are provided that they are the mixtures having the composition given above deliver.

In order to obtain the best results in accordance with the invention, one uses preferably an aqueous solution consisting of potassium vanadyl disulfate and potassium bisulfate (VOS04. K2SO4 + 2 EHS04), whereby the valence of the vanadium is reduced to 4 is; the solution can optionally contain activators or stabilizers.

Connections with the other known valencies 2, 3, 5 and 7 were also examined, and it was found that they too can be used; but the use of these compounds is due to them lower solubility and stability and as a result of their more difficult production and the higher cost less advantageous O According to the invention, silica gel, Clay and other natural or man-made substances are used, which are stable at the reaction temperature and have suitable mechanical strength, Thermal conductivity, porosity, specific surface area, pore diameter and apparent Own volume.

These properties are not critical; however, to get the best results commercial silica gels with the following properties are preferred: Specific surface area 250-800 m2 / g.

Porosity 0.3-1.7 ml / g pore diameter 20-200 i Apparent density (Bulk density) 0.4-0.8 g / ml grain size distribution the most suitable for the reactor, in which the catalyst is to be used, e.g. for a fixed bed 2-5 mm; for a fluidized bed P, 075-0,300 mm.

The two impregnation methods given below can be used be: a) The porous support is in an excess of the solution of the active substances submerged (the air contained in the pores escapes quickly), and those on the Outer surface of the grains adhering as well as that contained in the macropores of the carrier Solution is removed by centrifugation in a liquid extractor that has a provides corresponding centrifugal force (approx. 200 to 2000 g (unit of gravitational acceleration)) to remove the excess solution, i.e. the part of the solution that does not adhere to adheres to the outer surface of the grains or contained in the macro-pores of the carrier is.

The solution removed in this way can be returned to the subsequent impregnation will. b) The solution is sprayed or dripped onto the carrier, which is in rotating drums, V-misoing in fluidized bed reactors or other suitable devices in motion is held. The volume of the impregnation solution must be less than the pore volume of the door rs.

The drying and final calcining are not particularly critical and can be carried out in the same impregnation device if this is appropriately constructed.

The porosity of all types of carrier must be chosen so that with the Salt-impregnated surface reaches a maximum per unit volume of catalyst, that according to practical tests a maximum of catalyst activity and selectivity is equivalent to.

The concentration or density of the solution can be 160 g of active salts per 100 g of water (100 g of salts per 100 ml of solution), and this high solubility or density values are special characteristics of the present invention and permit quite a number of different endings.

It is possible in this way to change the concentration of the solution or to vary the moisture already contained in the carrier so that each grain, even with high concentrations of active salts, based on the carrier, perfectly is evenly impregnated; on the other hand, you can also get carrier grains that are only partially or slightly impregnated, if so desired.

In this way it is possible that the carrier in the pores leading to the for the most part are still accessible from the outside, such a catalytic or adsorptive Activity develops that modifies the rate of formation of phthalic anhydride or the ratios between the various reaction products can be varied being also higher resistance to those in naphthalene with technical Purity contained poisons is achieved.

It is known that the formation of larger amounts of naphthoquinones leads to serious technical disadvantages. It becomes the deposition of tar pitch in the pipes and heat exchangers, and during longer cleaning treatments some of the crude phthalic anhydride formed is lost.

It is also known that those contained in technical naphthalene sulfur-containing impurities are catalytically oxidized to S sulfuric anhydride and tend to increase the apparent density of the catalyst. As a result, the active salts are partially exposed and agglomeration takes place of the individual pills, thereby increasing the active surface humiliated and the turbulence is impaired.

In comparison to the known methods, the method according to FIG The invention has the following advantages: a) It provides catalysts which, if desired, with the same concentration of active compounds a higher specific surface area and a higher porosity and thus a higher catalytic activity and selectivity to have. Due to the higher activity can advantageously at temperatures with optimal Yield are worked, which are much lower than those usually used. Due to the higher selectivity, naphthoquinones are only formed to a small extent Extent or not at all, b) With the same activity, the concentration is on expensive active connections lower. c) The manufacturing process does not contain any critical conditions and can be done quickly and economically in simple devices be carried out with practically <iuantitative yields. d) The process makes it possible to vary the quality of the catalyst slightly Better adapt the catalyst to the desired purpose. e) There are catalysts that are more resistant to poisoning, abrasion and pressure.

The following examples illustrate the invention, but without the To limit the scope of protection Example 1 a) Preparation of the 698 g solution of a 13.21% strength aqueous H2SO4 solution 218.4 g K2S (99.95%) 57.2 g T205 (99.65%) are contained in the in the order given in a 1000 ml flask. The internal temperature the mixture is adjusted to 60 ° C. with stirring, and through a suitable inlet pipe SO2 is absorbed to saturation, which requires at least 20 g.

The first yellow-orange suspension becomes light as the progression is made exothermic reduction of the vanadium more fluid, then green and finally clear with a bright blue hue.

A solution with a density of 1.35 g / ml is obtained that lasts for years is stable and contains 375 g of salts (calculated at 4000C). This concentration (i.e. 60.3 g of salts per 100 g of water) is already sufficient for many purposes. If you need a higher concentration (100 g of salts per 100 g of water), steam is used the solution with the help of an externally attached bath of 60 - 6500) under one Residual vacuum of 60 mm Hg at 500C. A concentration of 160 to 170 g of salts per 100 g of water at 600C should not be exceeded in order to crystallize out from KHSO 4.

The highly concentrated solutions must immediately be warm (preferably at 50 - 600C) can be used; if they crystallize, they must be diluted and be concentrated again in a suitable manner b) impregnation 663 g (490 ml) of the The above-mentioned dilute solution containing 250 g of salts are up to 500 g = 330 ml concentrated. The solution is then used over a period of 30 minutes at a speed lower than the critical one, at 20 - 30 ° C in a rotating drum on 760 g of silica gel, which was dried at 1500C and has the following properties: Specific surface 340 m2 / g Porosity 1.16 ml / g pore diameter 140 Å Apparent density (bulk density) 0.43 # Grain size distribution 0.075-0.300 mm The solution is adsorbed immediately, and the light blue colored mass always remains dry and free-flowing.

The catalytic mass is dried in an oven at 150 ° C. for four hours. 1030 g of a violet catalyst are obtained. By calcining for four hours 1000 g of a golden yellow catalyst are obtained in a stream of air at 3800.degree. the Oxidation of the vanadium takes place at around 2800C.

The catalyst is uneven and contains about 60% unimpregnated Grains. It does not contain salts that can be removed by sieving or salts that which adhere to the outer surfaces of the silica gel grains. The specific surface is 200 m2 / g.

The catalyst obtained according to Example 1 is placed in a fluidized bed reactor filled and activated in a stream of air at 3800C for 10 hours.

Technical naphthalene (purity 98%; 1.3% thionaphthene; 0.7 g α - # - methylnaphtahline, Indan etc.) is evaporated with hot air and then under the following technical Catalytic conditions passed through the catalyst: Space velocity: 0.04 - 0.05 kg naphthalene / kg catalyst / hour weight ratio air / naphthalene: 11.4 Contact time: 4 - 6 seconds After a period of treatment, the escaping gases can be released The individual reaction products are condensed over the catalyst for 30 hours and be determined. The molar yields for different catalyst temperatures and calculated on the technical naphthalene used (assumed as pure naphthalene) are indicated in FIG.

The optimum yield is achieved at 3650C and corresponds to the following Values: phthalic anhydride 88.4 mol. (102.5 wt.%) Maleic anhydride 4.4 mol.% Naphthoquinones 1.6 mol% Example 2 300 g silica gel with the properties of Example 1b are concentrated in 750 ml = 1130 g of a Immersed solution containing 565 g of the active salts prepared according to Example 1 a contains0 The air contained in the pores escapes immediately. After standing over For a period of 30 minutes, the mass is 5 minutes at 250 g (is not meant Gram ", but the unit of gravitational acceleration) centrifuged0 800 g of the impregnated After drying at 150 ° C., pale yellow silica gel yields 570 g of a purple-colored one Product. The mass is mixed with 460 g of non-impregnated silica gel and at Calcined 3800C.

1000 g of catalyst with the appearance of the catalyst are obtained Example 1. The specific surface area is 850 m2 / g.

When using this mass as a catalyst under the example 1 b specified conditions-one obtains the same yields, but with one Temperature optimum of 3550C.

Example 2 663 g = 490 ml of the solution prepared according to Example 1 a, which contains 250 g of salts are diluted with water to 833 g = 660 ml.

The solution is then added dropwise to 760 g of silica gel as in Example 1b added, which has been dried at 1500C and which has the following properties: Specific surface area 405 m2 / g porosity 0.9 ml / g pore diameter 89 i apparent Density (bulk density) 0.36 g / ml Grain size distribution 0.75-0.300 mm Then work the procedure of Example 1b is continued.

There are 1000 g of a uniformly light golden yellow colored granular Catalyst, the grains of which are uniformly impregnated, obtained. In a catalysis experiment over a little more than 200 hours under the conditions of Example 1b was obtained with the catalyst the constant yields of FIG. 2.

Optimal yields are obtained at 322 ° C .; they are for: phthalic anhydride = 88.0 mol% (101.6 wt%) maleic anhydride = 5.2 mol% naphthoquinones = 0.1 Mol.-The naphthoquinones are removed at temperatures above 3250C and give colorless condensates.

Example 4 810 g = 534 ml of a prepared as in Example la concentrated solution containing 405 g of active salts is as in Example 1b added dropwise to 603 g of silica gel which was dried at 1500C and the Properties of the silica gel according to Example 3 had. Then the way of working closes according to example 1b. 1000 g of a uniform, dark golden yellow catalyst are obtained made of grains that are all evenly impregnated.

In the case of catalysis, under the conditions of Example 1b optimal yields at 3300C; for: phthalic anhydride they are 87.8 mol% (101.6% by weight) maleic anhydride 3.7 mol% naphthoquinones 0.01 mol% - claims -

Claims (10)

Claims 1. Process for the production of catalysts based on active substances containing vanadium for the oxidation of aromatic substances Hydrocarbons, especially from naphthalene to phthalic anhydride, thereby characterized in that one is an aqueous solution containing V204, SO3 and K20 in molar ratios contains between 1 s 6 s 2 and 1: 10: 6, on a natural or artificial porous carrier adsorbed and the impregnated! Embossers then in a stream of air calcined. 2. The method according to claim 1, characterized in that the Impregnation is carried out at temperatures of about 10-90 ° C. 3. The method according to claim 1 and 2, characterized in that one adjusts the molar ratio between V204, SO3, K20 to the value 1: 8 s 4, 4. Procedure according to claims 1 to 3, characterized in that the porous carrier is silica gel used. 5. The method according to claim 4, characterized in that silica gel with the following technical properties used Specific surface 250-800 m2 / g porosity 0.3-1.7 ml / g pore diameter 20-800 Å Apparent density (sole density) 0.4-0.8 # grain size distribution 0.075-5 mm 6. The method according to claim 1 to 4, characterized in that the porous carrier at temperatures between 10 and 90 ° C immersed in an aqueous solution of the catalytically active compounds, the volume of which is at least equal to the total volume of the pores of the carrier, that the impregnated carrier is centrifuged at 200 - 2000 g (unit of acceleration due to gravity), up the excess solution, namely the solution that is on the outer surface the grain of the carrier adheres and which is contained in the macropores of the carrier, is removed, and that the catalyst system thus obtained in a hot air stream calcined in a manner known per se. 7. The method according to claim 1 to 4, characterized in that one an aqueous solution on the porous support at temperatures between 10 and 90 ° C of the catalytically active compounds, the volume of which is at least equal to the total volume of the pores of the support, and that the catalyst system thus obtained calcined in a stream of hot air for a period known per se. 8. Vanadium-containing supported catalysts, characterized in that them on the inner surfaces of the pores of a natural or artificial support catalytically active substances, calculated as V204, 503 and K20, in molar proportions between 1 t 6 t 2 to 1 s 10 t 6, preferably in a molar ratio of 1 t 8 t 4. 90 supported catalysts according to claim 6, characterized in that the carrier is made of silica gel with the following technical properties? Specific Surface area 250-800 m2 / g porosity 0.3-1.7 ml / g pore diameter 20-800 Å Apparent Density (bulk density) 0.4-0.8 g / ml grain size distribution 0.075-5 mm 10. Supported catalysts for the vapor phase oxidation of naphthalene to phthalic anhydride on the basis of Vanadium-containing active substances, characterized in that they according to the process according to claims 1 to 6 have been produced.