DE1201327B - Production of phthalic anhydride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07c

German class: 12 ο -14

Number: 1201327

File number: B 75379IV b / 12 ο

Filing date: February 12, 1964

Opening day: September 23, 1965

It is known that one can produce phthalic anhydride by the oxidation of naphthalene or o-xylene with oxygen-containing gases, in particular with air, at a temperature between about 300 and about 55O ⁰ C in the presence of catalysts. The catalyst can be fixed in the oxidation space or it can be in a whirling motion. Many catalysts have been described for this purpose, the active constituents of which are vanadium compounds. It is also known to use the supported and unsupported catalysts.

Both catalysts are known in which the vanadium compounds in alkali metal pyrosulfate, in particular in potassium pyrosulphate or in a mixture of sodium pyrosulphate and potassium pyrosulphate and in which the vanadium is present as pentavalent vanadium, as well as catalysts that are free from Pyrosulfates are and contain the vanadium partly or wholly as tetravalent vanadium.

It has now been found that, in the preparation of phthalic anhydride by oxidation of o-xylene or naphthalene with oxygen or such gases containing in molecular form at a temperature of 250 to 420 ⁰ C in the gas phase on a supported catalyst, which is the catalytically active Constituent vanadium compounds, dissolved in potassium pyrosulfate or in mixtures of various alkali metal pyrosulfates, gives higher yields than when using previously known catalysts if the oxidation is carried out with a supported catalyst which contains 0.5 to 15 percent by weight, in particular 0.5 to 10 percent by weight, of oxygen Contains vanadium compounds, based on the total catalyst and calculated as V ₂ O ₅ , with at least 50% of the vanadium, but not more than 90%, from the outset in the form of tetravalent vanadium and at least 10% in the form of pentavalent vanadium.

The catalysts of the invention can, for example, by partial reduction of in customary Way prepared catalysts with pentavalent vanadium or by mixing catalysts that containing pentavalent vanadium, can be made with those containing tetravalent vanadium.

The vanadium pentoxide can be replaced in part, up to about 80%, by phosphoric acid and optionally molybdenum and / or tungstic acid; the phosphoric acid content can be up to 40 percent by weight (phosphorus pentoxide) and the molybdenum or tungstic acid content up to 40 percent by weight (MoO ₃ or Wo ₃ ), each based on the active catalyst substances. Production of phthalic anhydride is understood here

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Wilhelm Friedrichsen, Ludwigshafen / Rhine; Dr. Otto Göhre, Heidelberg

active catalyst substances vanadium pentoxide, optionally phosphoric acid and additions of molybdenum and / or tungsten oxide, optionally silver or copper oxide.
The catalysts used for the oxidation of o-xylene or naphthalene to phthalic anhydride can, for example, by applying a melt of an alkali pyrosulfate or a mixture of alkali pyrosulfates in which the vanadium pentoxide, optionally with additives, is dissolved on the carrier substances in a vortex process or by Mixing can be produced in a mixing drum at a temperature above the melting temperature of the alkali pyrosulfate melt. But they can also be prepared so as to impregnating the support material with aqueous solutions containing the active ingredients, compounds which when heated Alkalipyrosulfat, and optionally additives, drying the support thus treated and at 200-650 ⁰ C, in particular at 550 to 65O ⁰ C, annealed, ζ. B. 2 to 48 hours, until the vanadium-containing pyrosulfate melt forms in the pores of the carrier. In these catalysts, the vanadium oxide-containing alkali metal pyrosulfates, including any additives, are located as a liquid melt in the pores of the catalyst support under the reaction conditions of oxidation.

The usual carriers can be used, for example those with large internal surfaces, e.g. B. with 200 to 400 m ³ / g, of which, for example, may be mentioned: aluminum phosphate, artificial or natural silicates, active coals, pumice stone, silica or silica gel that was obtained as granules by precipitating silica sol, subsequent drying, calcining and crushing . However, it is preferred to use supports with small internal surfaces, e.g. B. from about 2 to 50 m ² / g, of which titanium oxide, cerium oxide or over 1000 ⁰ C as examples

E09 688/472

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heated alumina may be mentioned. Finally, one can apply the melt to the carrier, it is expedient-

also use mixtures of different carriers. moderate to let the melt solidify first and

If you put the catalyst by applying the crush the melt cake.

Pyrosulphate melt with the active ingredients For applying the vanadium pentoxide and

and the additives, for example 5 pyrosulphate melts, which may contain additives

First of all, produce the melt in the following way: one can rely on the carrier substance in different ways

Use an alkali pyrosulfate or alkali hydrogen sulfate or methods. For example, in a

a mixture of an alkali sulfate and an equi-mixing drum that has a grain size of about

equivalent amount of sulfuric acid or mixtures of 200 μ or smaller ground solidified melt material

Mix alkali pyrosulphates, alkali hydrogen sulphates or from io with the appropriate amount of carrier and

several alkali sulfates and sulfuric acid are then heated to 250 to 650 ^° C. for several hours

if necessary heated and heated together with water. This is where the liquefying melt

melted until the water has evaporated. Good soil absorbed by the pores of the carrier material,

Results are achieved when using potassium pyro- The carrier is expediently used for uniform

sulphate, potassium hydrogen sulphate or potassium sulphate kept in motion in the 15 division of the melt. This can

Mixture with sulfuric acid or of mixtures z. B. carried out in a heated stirred tank

contain sodium and potassium pyrosulphate at the same time, or in a heated screw conveyor

but also additions of lithium or rubidium are made. Another method is that you

may contain pyrosulfates or hydrogen sulfates, the carrier material with air or an inert gas, ζ. Β.

achieved. Then at about 300 to 45O ⁰ C to 20 nitrogen or carbon dioxide, in whirling motion

Vanadium compounds, in particular vanadium pentoxide, and to a temperature above the

or ammonium vanadate, and optionally the melting temperature of the pyrosulphate melt is heated,

Sentences such as phosphoric acid, molybdic acid or wolf- the finely powdered melt material to the whirling cat-

ramic acid or other additives in the melt analyzer and then catalyst supports and

solved. Vanadium compounds can also be melted for a few hours, e.g. B. 2 to 24 hours,

apply that during the preparation of the catalyst at a temperature above the melting point

pass into vanadium pentoxide, e.g. B. Vanadium (III) - leaves the melt in a whirling motion. Man

chloride, vanadium (III) oxide or vanadyl sulfate, VOSO ₄ . can use this to homogenize the catalyst

So much vanadium compound is used that the reaction temperature

Melt 1 to 30 percent by weight vanadium pentoxide 3 ° temperature in the air stream or in the oxygen containing

contains. Melts which keep the gas flow in swirling motion are preferably used.

2 to 20 percent by weight, in particular 3 to 15 percent. It is useful for large surfaces

contain vanadium pentoxide by weight. If Phos supports temperatures a little above the pour point

phosphoric acid is added, it can be used as such or in the pyrosulfate-vanadium mixture, e.g. B.

Form of phosphorus pentoxide or in the form of 35 200 to 460 ° C, while with carriers with only

Bonds that provide phosphoric acid are added to small internal surfaces advantageously at higher ones

will. So you can also phosphorus pentasulfide, Am temperature, for example between 450 and 600 ⁰ C, ins-

Moniumphosphat, sodium or potassium phosphate special over 500 ⁰ C, works. The flow point of the

as primary, secondary or tertiary phosphates melt is defined as the temperature at which

turn around. When using alkali phosphates, 40 pyrosulphate grinded to a grain size of 0.3 mm must be

an amount of sulfuric acid melt particles corresponding to the alkali begin to flow into one another and

added and taken into account as pyrosulphate. to wet the melting tube.

If phosphorus compounds are added, the ratio between vanadium pentoxide

one adds such amounts that a maximum of 4 weight-containing pyrosulfate melt and carrier can be in

Percent phosphorus pentoxide in the pyrosulfate melt 45 can be varied within a certain range. There are in

are present. generally at least 5 percent by weight of pyrosulfate

Any molybdenum compound melt added, based on the catalyst, is required;

fertilize in the form of molybdic acid, molyb- the upper limit for the proportion of pyrosulphate

Denoxide, molybdenum sulfide and ammonium molybdate melt on the catalyst depends to a large extent on

used. But you can also use sodium or 50 from the type of carrier used. Too high

Potassium molybdate or, advantageously, phosphorus molybdenum content usually leads to caking or

use acid. The content of alkalis is expedient sticking together of catalyst grains, e.g. B. a

moderately compensated by adding sulfuric acid. Share of more than 60 percent by weight, based on

Instead of the molybdenum compounds, a catalyst can be used, if silica gel is used as the carrier.

Add tungsten compounds, for example Wolf 55 Preference is given to using 10 to 50

ramic acid, tungsten oxides, tungsten sulphides, ammo weight percent vanadium-containing pyrosulphate melt,

nium tungstate or phosphotungstic acid. One referred to the finished catalyst, in particular

Can also mix molybdenum and tungsten using silica gel.

Add connections. If you have the supported catalyst on wet

Vanadium pentoxide can be added by 60 ways, i. H. by impregnating the carrier with aqueous

for example from 1 to 10 percent by weight of silver solutions containing vanadium, optionally phosphorus,

oxide or copper oxide, based on vanadium pent, molybdenum and / or tungstic acid containing

oxide, activate. ties, makes, one assumes accordingly

The total amount of active substance in the pyro-composed solutions. For the bulk sulphate melt should not be more than 40 percent by weight 65 ratios, the same numerical ratios apply as (calculated as oxides) of the melt mixture. in the case of those produced by applying the melt The total amount of active sub-catalysts is advantageously. Instead of pyrosulfates or alkali distance between 10 and 30 percent by weight. Before the hydrogen sulfate you can also use alkali sulfate and

5 6

Use sulfuric acid. But you can also use medium. The melting temperature rises. That I

Alkali sulfate alone without the addition of sulfuric acid in which the pour point on the carrier can no longer be determined

use aqueous solution and left by treatment, is determined appropriately in a control

of the soaked and dried catalysts with trial once and for all, like the pour points for one Sulfur trioxide or such supplying organic 5 are a certain proportion of tetravalent vanadium,

or inorganic sulfur compounds, e.g. B. Thio- The easiest way is to set up a curve in which the

phen, carbon disulfide or sulfur dioxide, wäh- ratios of tetravalent to pentavalent Vana-

At the end of the tempering in the air stream, the alkali metal with the melting point is applied against one another

Sulphates are the pyrosulphates and thus the alkali pyro- are. By analytical determination of tetravalent Manufacture sulphate melt. io and pentavalent vanadium on the reduced

According to the invention, only part of the supported catalyst can then be reversed

Determine at least 50% »of the yield point on the support.

Vanadins are in tetravalent form. At all the manufacture of the catalyst is not common The manufacturing process for the catalyst was protected.

unless special precautions are taken to ensure that the reaction conditions for the oxidation of the Vanadium converted into pentavalent vanadium. You must add o-xylene or naphthalene to phthalic acid therefore reduce it at least in part. Am anhydride are the same as easiest to use it takes place if one uses known catalysts before using them.

of the catalyst for the phthalic anhydride preparation. Preference is given to using 98 to 100% strength o-xylene, at a temperature at which the vanadium-containing ao 10% m-, p-xylene and / or medium, especially gaseous SO ₂ , as long as ethylene benzene. The last-mentioned tempts, until one finds on a sample taken because of the burning of bonds under the reaction conditions of the reducing effect that at least largely to carbon dioxide or carbon monoxide. 50 percent by weight is present as tetravalent vanadium. The o-xylene will, for example, be in an amount of. If the reduction has gone too far, 30 to 120 g per normal cubic meter of air, accordingly you can simply add a corresponding amount of not 150 to 600 g of xylene, based on normal cubic meters of reduced pentavalent vanadium-containing catalytic oxygen, via the sator at the reaction temperature. kept layer of the catalyst brought.

One can of course also avoid oxy- 30 However, a raw material can also be used as the starting material.

dative media, e.g. B. exclusion of oxygen, naphthalene with a freezing point of 77.0 to

Use the total amount or 79.5 ° C during manufacture. This contains crude naphthalene

a part of the vanadium in tetravalent form on the usually sulfur-containing compounds, z. B.

Bring a catalyst by using stable four-thionaphthene, corresponding to a sulfur content of

valuable vanadium compounds, e.g. B. vanadyl sulfate, 35 0.1 to 1.0%

Vanadyl oxolate or vanadyl formate is used. In tes naphthalene, e.g. B. a crude naphthalene, which is noticeably

In this case, a separate reduction of the vanadium borrowed amounts of methylnaphthalene and / or

before using the catalyst no longer contains anthracene and / or phenanthrene, z. B.

conducive. those in tar distillation or in the pyrolysis of

According to the invention, the vanadium must use the hydrocarbon-accumulating fraction with a boiling range of about 210 to 240.degree. C. already at the beginning of the use of the catalyst. The tetravalent vanadium present. In this way, naphthalene does not require any special pretreatment, the process differs from the known addition of, in particular, it is not necessary _{to remove the low-sulfur amounts of SO 2} during the phthalic acid-containing impurities prior to the conversion of deanhydride production for the purpose of supplementing the 45; it is also not necessary to _{remove the polymerizable contaminants in a separate SO 3} loss during the use of the catalyst pretreatment. to separate.

As a rule of thumb, it can be stated that better results are obtained. For example, naphthalene is used in a quantity Booty can be achieved if the vanadium content is high from 30 to 150 g per normal cubic meter of air of the catalyst largely tetravalent Va- so 150 to 750 g of naphthalene per normal cubicnadine has been present or if you have a small meter of oxygen, in the oxygen-containing gas in Vanadium content is relatively less Vanadium (IV) - the layer of the kept at reaction temperature compounds are present, provided that you brought a catalyst. The o-xylene or naphtha Limit of 50 to 90% of the existing vanadium thaline vapor stream is obtained, for example, by adheres to. Catalysts that have 0.5 55 partial flow saturation and mixing with the main bis have proven themselves 15 percent by weight of oxygen-containing vanadium stream, by evaporation into the gas stream or through compound, in particular 0.5 to 10 percent by weight, injecting the o-xylene or naphthalene in solid based on the total catalyst. or liquid form, optionally with the help of a

It is advantageous if one in the reduced four auxiliary gas stream, z. B. with nitrogen. The o-xylene or

Valuable vanadium-containing catalyst a 60 naphthalene can also be separated from those for the

The flow point of the pyrosulphate melt is present, the oxygen-containing gases required for the reaction

approximately in the vicinity of the reaction temperature, for example directly on the catalyst layer. the

wise 40 ° C, below to 20 ⁰ C above the xylene inlet concentrations for the oxidation according to the above

of o-xylene or naphthalene provided reaction values are 0.6 to 2.5 percent by volume, and the

temperature is. To set this favorable 65 naphthalene inlet concentration, when using

In the range, a pyrosulphate melt is first made of air, depending on the catalyst loading

that are lower than the intended reaction temperature up to 3 percent by volume. It is also possible,

melts. Then deal with using the reducing mixtures of naphthalene and o-xylene.

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The catalyst can be fixed, or it can have residence times of

can be in a whirling motion. The 5 to 50 seconds, especially 5 to 40 seconds,

Carrying out the whirling process is preferable. complies with and in procedures with a fixed

The oxidation temperature for both o-xylene catalysts is 0.2 to 1 seconds. The dwell time is

as well as with naphthalene at about 250 to 420 ° C, especially defined as usual, d. i.e., it's the time during

especially at 300 to 39O ⁰ C. The flow rate of the starting material with the catalyst in

diness of the gases and vapors and the volume of contact is, whereby one is on the whole, from the

Catalyst layers are to be coordinated with one another, the catalyst relates to an imaginary reaction space:

.,. Catalyst space volume

Dwell time = - - -

Gas volume per second (based on pressure
and temperature in the catalyst room)

The process can be carried out at normal pressure, easily 15,600 parts of this catalyst in one with

increased pressure, e.g. B. up to 3 at, or given a quartz tube with increased external heating and

Pressure, e.g. B. at 5 to 25 at. under vortex conditions with air containing 2% sulfur

It is advantageous that contains dioxide during the oxidation treatment at 400 ⁰ C until themselves

of o-xylene or naphthalene small amounts, e.g. B. 65% of the vanadium pentoxide in tetravalent vanadium

0.5 to 2.5 percent by weight, based on o-xylene 20 converted. The pour point of the

or naphthalene, sulfur, sulfur trioxide or carrier melt has been reduced from 240

Sulfur compounds that are on the catalyst below the to 370 ⁰ C increased.

The catalyst produced in this way, together with the compound to be oxidized, is difficult to conduct the catalyst over a 1 m long, provided with external heating. The sulfur compounds, 25 fusible glass tube with a clear width of or the sulfur can be included from the outset in the 42 mm dimension, which for better gas distribution with wire material, z. B. is filled in sulphurous spirals, given. At 380 ^° C., naphthalene or else can be added. For example, 24.3 g of o-xylene vapor, in which 0.6 Ge sulfur dioxide or organic sulfur compounds, weight percent sulfur dioxide are dissolved, with 9171 such as carbon disulfide or thiophene can be added per hour. 30 air passed over the fluidized catalytic converter. After this

In the case of small plants, the catalyst will be in a cooling down of the hot vapors per hour Quartz tube, for larger systems in a tube made of 26 g phthalic anhydride and 0.87 g maleic acid iron or stainless steel fixed or preserved in swirling anhydride. The weight gain of phthalic movement held. The use of stainless steel acid anhydride is 107%> corresponding to 76.8% of the use of iron is preferable, since 35 theory.

Carrying out the oxidation in an iron pipe. Example 2
increased combustion of o-xylene to carbon dioxide

and carbon monoxide makes itself felt. The gas 700 parts of titanium dioxide with a grain size distribution of 0.06 is optionally conical up to 0.2 mm are intimately drawn with a finely ground lower end of the reaction tube through a 40 melt of 35 parts vanadium pentoxide and 105 parts ceramic plate or metallic sintering of potassium pyrosulphate for 12 hours at 600 ^° C. in the material or mixed by means of a muffle furnace. The catalyst is then conical insert produced annular gap bewerk- as in Example 1 at 400 ⁰ C with a 2% Schwestelligt. When using small reaction tubes, the field dioxide-air mixture can be treated until 75% of the heat is dissipated through the reaction wall of the vanadium pentoxide in tetravalent vanadium overpipe z. B. are guided by air cooling or by means of a. The pour point of the salt melt on the carrier, when using larger-sized melt is then 380 ° C compared to ionized units is for the dissipation of the reac- 24O ⁰ C of the untreated catalyst,
The installation of cooling coils in the over 800 ecm of this pretreated catalyzed fluidized bed is necessary. The heat can then be used for 50 sators at 375 ⁰ C under vortex conditions such as steam generation. In the case of example 1, 16.4 g of vaporous vortex process per hour is expediently passed through the vessel with closed air or with o-xylene with 5741 air. Per hour, partially open fillers, wire spirals or, in addition to 1.05 g of maleic anhydride, 18.5 g of phthalic acid-shaped wire meshes are obtained, advantageously in anhydride. The weight yield of phthalic acid in the edge zone of the reaction zone per unit area of the anhydride is 112.8%> corresponding to 81% of the lower boundary area more air or air theory.

Hydrocarbon mixture is introduced as in Example 3
middle areas of the reaction zone.

. -I _{1 of} 800 ecm of that obtained according to Example 2, but

B 1 e s 1 e ρ 1 1 _{not go nocht re <j uz} i _Erten catalyst 490 cc

300 parts of a finely ground melt of 15% at 400 ° C with air that contains 5% sulfur dioxide,

Vanadium pentoxide and 85% potassium pyrosulphate are whirled until the content of tetravalent

with 900 parts of broken titanium dioxide with a vanadium 90%. After mixing this up

Grain from 0.2 to 0.5 mm intimately mixed. The catalyst with the non-reduced amount receives

Mixture is then in a muffle furnace under 65 one a mixed catalyst, which 55% of the previous

Heated mixing 12 hours 600 ⁰ C, which contains the handenen vanadium as Vanadintetraoxyd.

Melt is evenly sucked up by the carrier over the catalyst obtained in this way

will. 11.4 g of o-xylene with 500 l of air in the hour

the same apparatus as in Example 1 passed. The condensed vapors become in the hour 13.1 g of phthalic anhydride and 0.6 g of maleic anhydride were obtained. The weight yield is %, corresponding to 83% of theory.

Claims (2)

Patent claims: 1. A process for preparing phthalic anhydride by the oxidation of naphthalene or o-xylene with oxygen or oxygen in molecular form containing gases at a temperature of 250 to 42O ⁰ C in the gas phase over a supported catalyst, the active and catalytically part of vanadium compounds, dissolved in potassium pyrosulfate or in mixtures of different alkali metal pyrosulfates, characterized in that the oxidation with a Carries out a supported catalyst containing 0.5 to 15 percent by weight, in particular 0.5 to 10 percent by weight, of oxygen-containing vanadium compounds, based on the total catalyst and calculated as V ₂ O ₅ , with at least 50% of the vanadium, but not more than 90% ^of from the outset in the form of tetravalent vanadium and at least 10% in the form of pentavalent vanadium. 2. The method according to claim 1, characterized in that the oxidation with a supported catalyst carries out, in which the tetravalent vanadium by reduction prior to its use of vanadium (V) compounds or by mixing a supported catalyst with vanadium (V) oxygen compounds produced with a supported catalyst with vanadium (^ oxygen compounds had been. 509 688/472 9.65 © Bundesdruckerei Berlin