DE1169912B - Process for the production of phthalic anhydride - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school KI .: C 07 c

German KL: 12 ο -14

Number: 1169 912

File number: B 64169 IVb / 12 ο

Filing date: September 28, 1961

Opening day: May 14, 1964

The main patent application B 62 309 IVb / 12o is a process for the production of phthalic anhydride by oxidation of o-xylene with oxygen-containing gases at a temperature of 250 to 420 ⁰ C using vanadium pentoxide-allcalipyrosulfate supported catalysts in the fluidized bed, in which one a catalyst is used which, in the pores of a highly porous carrier material with a grain size of 10 to 3000 μ, contains a mixture of vanadium pentoxide and at least two pyrosulfates of different alkali metals that is liquid under the reaction conditions and whose melting point is lower than that of potassium pyrosulfate.

It has now been found that even when using naphthalene instead of o-xylene, the process described in the main patent application phthalic anhydride in excellent Maintains yield and purity.

This process has two major advantages: First, the catalyst is optional Use for the oxidation of o-xylene or naphthalene in the fluidized bed. That's unusual, because, according to previous experience, a type of catalyst when used in the fluidized bed either only with naphthalene or with o-xylene oxidation leads to good results; Second, it was surprising that the new catalysts in the Using naphthalene as a starting material gives better results in terms of resilience, more consistent Have activity and lifetime than the known catalysts, also as the catalysts, the z. B. by the method of Belgian patent specification 592 605 by applying vanadium pentoxide-potassium pyrosulfate melts on porous supports. Namely, if the oxidation of naphthalene is carried out in a fluidized bed using known catalysts at high concentrations of naphthalene, e.g. B. of more than 80 g Naphthalene per normal cubic meter of air, and at high catalyst loads, e.g. B. of 30 g of naphthalene per kilogram of catalyst and hour, the activity of the catalyst already decreases noticeably after a short operating time. This changes the composition of the end products, especially as well there is a change in the ratio of main to side reactions. So the burn increases Carbon monoxide and carbon dioxide decrease while the formation of naphthoquinone increases. It is known, that the proportion of naphthoquinone can be kept small by increasing the oxidation temperature. However, there is a reduction in the Selek process for the production of phthalic anhydride

Addition to registration: B 62309 IV b / 12 ο -
Interpretation document 1162 348

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Klaus Wiebusch,

Dr. Anton Feinauer,

Dr. Konstantin Andrussow,

Dr. Max Appl,

Dr. Helmut Nonnenmacher,

Ludwigshafen / Rhine

activity one, d. i.e., the ratio of the mole percent phthalic anhydride to the sum of the mole percent of Carbon monoxide and carbon dioxide become smaller, the maleic anhydride content increases. All in all the yield of phthalic anhydride decreases with the conversion remaining the same. The known method at For these reasons, part of the catalyst is always withdrawn from the fluidized bed and regenerated separately and is then led back again, can indeed provide a certain remedy, but it is quite elaborate. The new catalysts, however, remain even at high loads, e.g. B. of more than 30 g of naphthalene per kilogram of catalyst per hour, uniformly active and selective, d. h., the Phthalic anhydride yield does not decrease. The decrease in activity at low reaction temperatures, e.g. B. at 330 ° C or below occurs the new catalytic converters.

Another disadvantage of the known catalysts, the naphthalene oxidation in the fluidized bed are used, is their sensitivity to the sulfur compounds contained in technical naphthalene. Even sulfur contents of more than 0.1% in the naphthalene can lead to a significant Decrease in activity lead, as in the case of high space velocity over the catalyst, in a decrease in the Turnover rate and an increase in the naphthoquinone content of the crude product shows. Sulfur content of over 0.5% can be achieved within a few days

409 589/446

lead to complete poisoning of the catalyst. In this case, too, it is not possible to compensate for the decreasing activity by increasing the reaction temperature, since the resulting decrease in selectivity leads to significant yield losses. To avoid this, the usual sulfur content of technical naphthalene of 0.3 to 0.7% has to be reduced by a special desulfurization process before use as a raw material for phthalic anhydride production
reduce.

If, on the other hand, the method of the invention is used, even without pretreatment of technical naphthalene in non-subdivided

where one refers to the entire reaction space imagined free from the catalyst:

Dwell time =

Catalyst space volume

Gas volume per second

(based on pressure and temperature in

Catalyst room)

The preparation of the catalysts used according to the invention is described in patent application B 62 309 IVb / 12ο explained.

These catalysts are made by applying a melt of alkali pyrosulfates, in which the Vanadium pentoxide, optionally with additives, is dissolved on large-surface carrier substances with large Total pore volume produced. More precisely,

The method may at atmospheric pressure, slightly 0.1 ° / o ¹⁰ elevated pressure, eg. B. up to 3 atm, or under increased pressure, z. B. at 5 to 25 atm.

The selectivity of the catalysts, as defined above, increases as the reaction temperature falls. In contrast to the previously known Fluidized bed at concentrations of 80 to 150 g of 15 catalysts decreases in spite of the thereby decreasing Naphthalene per normal cubic meter of air, catalyst conversion rate, the content of naphthoquinone loads of 40 g of naphthalene per kilogram in the reaction products are only insignificant. It Achieve catalyst and hour over a long period of time without it is therefore possible with the Verdaß according to the invention the activity of the catalyst decreases. drive at lower reaction temperatures, e.g. B.

A crude naphthalene at 20,320 to 340 ° C. can be used as the starting material. This avoids the risk of a freezing point of 77.0 to 79.5 ° C and a spontaneous after-reaction of the reaction products. This crude naphthalene usually contains sulfur-containing impurities in the dilute zone above the fluidized bed, e.g. B. thionaphthene decreased. The activity of these catalysts accordingly allows a sulfur content of 0.1 to 1.0%. it, so low reaction temperatures even at You can also more heavily contaminated naph 25 catalyst loadings of 40 g of naphthalene per kilothalin, z. B. a raw naphthalene, the noticeable amounts of grams of catalyst and hour to adhere to methylnaphthalene and / or or anthracene and
or or contains phenanthrene, e.g. B. the fraction obtained in tar distillation or in the pyrolysis of hydrocarbons with a boiling range of 30
from about 210 to 240 ⁰ C, use. The naphthalene
does not require any special pretreatment, in particular it is not necessary to use the sulfur-containing
Remove contaminants prior to implementation;
Nor is it necessary to separate the melt, which is liquid under the reaction conditions for the treatment of the polymerizable impurities o-xylene oxidation, from vanadium oxide in a separate area. On the other hand, you can also use containing alkali pyrosulphates in the pores of the catalytic pure naphthalene with a sulfur content of <0.1%.

work. As a high-surface carrier, for example

The naphthalene is used, for example, in an amount of aluminum phosphate, artificial or natural from 30 to 150 g per normal cubic meter of air, corresponding to silicates, silica, in particular in the form of 150 to 750 g naphthalene per normal silica gel, or active carbons. Particularly suitable cubic meters of oxygen in the oxygen-containing gas is silica gel, which brings the fluidized sol, which is kept at the reaction temperature, by precipitating silica in, followed by drying, calcining and stratifying the catalyst. The naphthalene is 45 smaller than granules. It should be iron-free gas flow is obtained, for example, by partial flow. It is used in a grain size of 10 to 3000 μ, saturation and mixing with the main flow, through in particular from 20 to 600 μ. When evaporating into the gas stream or by injecting the naphthalene oxidation, a silica gel with grain naphthalene in solid or liquid form, given sizes from 75 to 300 μ, has proven particularly useful. The inner if with the help of an auxiliary gas stream, for. B. with stick 50 surface of the silica gel should be about 200 to about fabric. The naphthalene can also be separated from the 400 m ² / g, preferably 300 to 360 m ² / g, of oxygen-containing gases required for the reaction, the mean pore radius being introduced directly into the fluidized bed at about 50 to 60 AE. and the total volume is about 1 cm ³ / g. The surface-rich carrier can also be used in the form of air, depending on the catalyst used by microspheres, which can be up to 3 percent by volume. It is also possible to obtain mixtures of naphthalene and o-xylene by spray-drying aqueous concentrates.

to use. If active charcoals are used as a carrier

The oxidation temperature is about 250 to grain size range of from about 20 μ to 600, so may 42O ⁰ C, in particular 310-370 ° C. The flow rate during the production of the catalyst and the speed of the gases and vapors and the oxidation, as a rule, temperatures from 300 to volume of the fluidized bed are not exceeded in such a way that ^{340 0 C} 5 to 50 seconds of the active coals takes place in the air flow, which, in particular, takes 5 to 40 seconds. Man for the production of the vanadium-containing alkali pyro-

But even with residence times of 3 seconds, the mixtures of alkali pyrodes are obtained as sulphate melt good results. The residence time is like sulfates or alkali hydrogen sulfates, if appropriate commonly defined, d. i.e., it is the time during which, together with water, heated and melted until the starting material comes into contact with the catalyst and the water has evaporated. Then at about

5 6

300 to 450 ° C the vanadium compounds, in particular the upper limit for the proportion of pyrosulfate melt vanadium pentoxide or ammonium vanadate, in which the catalyst depends to a large extent on the type of melt dissolved. You can also use other vanadium from the carrier. Too high a proportion leads to use compounds that go under the reaction usually to caking or confluence in vanadium pentoxide, z. B. 5 glue of catalyst grains, z. B. a proportion of vanadium (III) chloride, vanadium (III) oxide or vanadyl more than 60 percent by weight, based on the catalyst, sulfate (VOSO ₄ ). So much vanadium is used when using silica gel as the carrier. Preferably binding that the melt contains 5 to 40 percent by weight, the use of 25 to 50 percent by weight of vanadium pentoxide. Pyrosulfate melts containing fused vanadium are preferably used, based on the zen, which contain 10 to 25 percent by weight of vanadium finished catalyst, in particular when pentoxide is used. You can get the vanadium pentoxide from silica gel.

by additions, for example from 1 to 10 weight- You can also produce these catalysts in this way

percent silver oxide or copper oxide, based on the fact that the carrier material with aqueous

Vanadium pentoxide, activate. Solutions of vanadium compounds and potassium

The mixtures of alkali pyrosulfate and sodium pyrosulfate used soak. Instead of the pyro-

Melts contain lithium sodium, lithium sulfates can also be the alkali hydrogen sulfates or

Potassium, sodium-potassium or lithium-sodium the alkali sulfates, optionally with the addition of

Potassium pyrosulphate mixtures. Sulfuric acid can also be used. The impregnated catalyst

Also use rubidium or cesium pyrosulphate. The generator is then dried and

However, these compounds are very rare, they have 20 temperatures from 200 to 600 ° C, in particular

of little importance for practical use. at 250 to 450 ° C.

The ratio of the individual alkalis in the pyro- When using alkali sulfate instead of Melt sulphate can vary considerably in the production of the alkali metal pyrosulphates but there are necessary for each pair of substances or for the catalyst to achieve the two-three combination a mixing ratio, the phase system, in which a liquid melt is in delivers particularly favorable results. Preference is given to the pores of the catalyst support, sulfur gas Sodium-potassium pyrosulphate pair of substances used, trioxide-containing gases or sulfur dioxide or such in particular sodium-potassium pyrosulphate mixtures, the sulfur compounds that form the sulfur-10 up to 50 percent by weight of sodium pyrosulphate trioxide, together with oxygen-containing ones keep. 3 ° to supply gases, with a temperature of

It is convenient to the vanadium pentoxide 250 to 500, especially from 300 ° C to comply containing 45O ⁰ C, Pyrosulfatschmelze initially in the desired. In this treatment, they are to be prepared in a fixed mixing ratio, then left to solidify in shape, left on the catalyst support, comminuted and added to the support in a liquid alkali pyrosulphate melt. 35 in which the vanadium compound is dissolved, transferred.

For the application of the vanadium pentoxide containing For the xylene oxidation is in the main patent pyrosulphate melts on the carrier substance can be used at reaction temperatures above 350 ° C a different methods. For example, the addition of sulfur trioxide or such can be recommended in a mixing drum on a grain substance. When using crude naphtha size of about 200 μ or smaller, ground, solidified 40 lin, as much sulfur melt material with the corresponding amount of compounds containing silica gel is generally fed to the catalyst, the carrier mix and then several hours on the catalyst to sulfur dioxide and sulfur 300 to 450 ⁰ C heat. In this case, the trioxide will be oxidized, so that in this case another liquid melt will be absorbed by the pores of the carrier. The support 45 is expediently the activity of the catalyst is not required. for even distribution of the melt in motion. This can e.g. B. be carried out in a heated tion temperatures above 310 ⁰ C and with high loading stirred tank or in a load, an additional supply of sulfur-heated screw conveyor. Another compound containing the catalyst sulfur method is that you form the powdered 50 trioxide, z. B. Thionaphthen, carbon disulfide melt in the with air or an inert gas, z. B. substance or sulfur dioxide, be advantageous. Other nitrogen or carbon dioxide, in whirling motion on the other hand, it is possible to use low-sulfur or offset carrier material such. B. the silica gel, trickle in sulfur-free naphthalene as a starting material and leave for a while, z. B. 8 hours, turn at one.

Temperature above the melting temperature of 55 The catalyst is used in small systems in one Pyrosulfate melt leaves. You can go to the Homogeni- quartz tube, with larger systems in one tube Sizing the catalyst this before use some iron or stainless steel, z. B. Austenitic Chromium Time at the reaction temperature in a stream of air or nickel steel, kept in a whirling motion. the in the oxygen-containing gas stream in the swirling use of stainless steel is the use of Keep moving. 6 ° iron to be preferred, since when performing the

The temperature at which the impregnation was carried out- Oxidation in an iron pipe increased combustion

is practically without influence on the action of the naphthalene to carbon dioxide and carbon

speed of the catalyst. Monoxide makes noticeable. The gas distribution will

The quantitative ratio between vanadium pentoxide at the lower, possibly conically drawn in containing pyrosulfate melt and carrier can be in 65 end of the reaction tube through a plate can be varied within a certain range. They are mainly common in ceramic or metallic sintered material at least 10 percent by weight of pyrosulfate- taken or via a cone-shaped melt, based on the catalyst, required; Use generated annular gap accomplished. At Ver.

The use of small reaction tubes can reduce heat dissipation over the wall of the reaction tube z. B. by air cooling or by means of a molten salt take place, when using larger dimensioned units is for the dissipation of the heat of reaction the installation of cooling coils in the fluidized bed is necessary. The heat is then used to generate steam usable.

The catalyst has very little abrasion and remains active for a long time.

example 1

a) Catalyst production

Catalyst A: 3690 g potassium pyrosulfate (K ₂ S ₂ O ₇₎ and 1525 g of sodium hydrogen sulfate (NaHSO ₄ H ₂ O) are melted in a crucible furnace and held about 1 hour at 350 ⁰ C. This melt contains 25% sodium pyrosulphate and 75% potassium pyrosulphate. Then 1080 g of vanadium pentoxide are introduced with stirring. After the end of the entry, the temperature is held at 350 ° C. for a further 1 hour. After cooling and solidification, the molten material containing 18% vanadium pentoxide is ground to a grain size of less than 150 μ. 5900 g of this powdered melting material are mixed with 7220 g of silica gel granulate, as it is known under the trade name Kieselgel BS, with a grain size of 60 to 300 μ in a mixing drum and then, with constant mixing, in a vessel made of Austem'tischer chromium-nickel steel within 4 hours heated to 350 ^° C. and then kept at this temperature for a further 4 hours. After cooling, the finished catalyst (pyrosulfate melt containing 45% vanadium, 55% silica gel) is sieved through a sieve with a mesh size of 300 μ.

b) naphthalene oxidation

5.01, corresponding to 3.4 kg, of this catalyst are placed in a vertical reaction tube made of austenitic chromium-nickel steel, 80 mm in diameter and 2500 mm in length, heated by a bath of molten saltpeter. The filling height is 1000 mm. The catalyst is initially heated to 350 ⁰ C. After preheating to reaction temperature, an air stream loaded with naphthalene is passed through a sintered plate made of austenitic chromium-nickel steel into the reaction tube and sets the catalyst in a whirling motion. At the upper end of the reaction tube, catalyst dust carried over by a ceramic filter is recovered. The filter zone is kept at temperatures between 200 and 250 ^° C. (above the condensation point of the phthalic anhydride). The gas mixture leaving the reaction tube after a residence time of about 10 seconds is freed from the bulk of phthalic anhydride in an air-cooled tube 1000 mm long and 50 mm in diameter. The gas, which has been cooled down to 40 ^° C., is then washed with water, the remaining phthalic anhydride and most of the maleic acid being absorbed. Solid product and wash water are analyzed for their phthalic anhydride, maleic anhydride and naphthoquinone content. The results listed below are average values from 10 days of operation.

The calculation of the mol percent was based on the fact that from 1 mol of naphthalene 1 mol Phthalic anhydride or maleic anhydride or naphthoquinone is formed.

1. When using naphthalene with a sulfur content of 0.08 percent by weight, one load of 85 g of naphthalene per normal cubic meter and a space velocity over the catalyst of 25 g of naphthalene The following temperatures are obtained per kilogram of catalyst and hour at the temperatures listed below Exploit:

Mole percent phthalic anhydride

Mole percent maleic anhydride

Mole percent naphthoquinone

Temperature ( ⁰ C) 350! 340 I 330 320

83 84 86

1.8 '1.5 0.06J 0.06

1.4 y 1.2

0.08J 0.10

2. At a constant temperature of 340 "C and naphthalene, As described under 1, but with different loading and catalyst loading, the results are:

Mole percent Phthalic acid loading 40.6 anhydride (g naphthalene / Nm * air) Mole percent Maleic acid 85! 100 j 138 82 anhydride load Mole percent Naphtho- (g naphthalene / kg 1.4 chinone,. Catalyst and hour) 35 25 j 29.5 0.12 ! 84! 84.5 1.5 1.5 0.06 0.08

3. When using technical naphthalene with a solidification point of 78,95 ⁰ C and a sulfur content of 0.47 weight percent and the mentioned under 1 Naphthalinbeladung and catalyst loading are obtained:

Mole percent phthalic anhydride

Mole percent maleic anhydride

Mole percent naphthoquinone

Temperature ( ⁰ C) 350 I 340 I 330 I 320

79.5 81 83 1.6 1.6 1.3 0.08 0.08 0.11

83

Example 2

For comparison, a catalyst (catalyst B) is produced whose melt consists only of potassium pyrosulphate and vanadium pentoxide. The procedure described in Example 1 is followed,

whereby 4920 g of potassium pyrosulfate and 1080 g of vanadium pentoxide be used. The finished catalyst contains 45% vanadium pentoxide-containing potassium pyrosulphate melt and 55% silica gel BS.

5.01 (3.4 kg) of this catalyst are, as in Example 1 described, used for naphthalene oxidation.

1. When using pure naphthalene with a sulfur content of 0.08 percent by weight, a loading of 85 g of naphthalene per normal cubic meter of air and a catalyst loading of 25 g of naphthalene per kilogram of catalyst per hour, the following results ^{are obtained at temperatures of 320 to 35O 0 C:}
15 mole percent phthalic anhydride

Mole percent maleic anhydride

Mole percent naphthoquinone

Load (g naphthalene / Nm ³ air)

85

100

load

(g naphthalene / kg

Catalyst and hour)

25 29.5: 40.1

83 5.0 1.7

79 4.9 3.2

73 4.9 5.6

Mole percent phthalic anhydride

Mole percent maleic anhydride

Mole percent naphthoquinone

Temperature ( ⁰ C)
350 340 I 330 I 320

5.5
0.5

83

5.0

1.7

77

4.6

4.5

69

3. When using technical naphthalene, with a solidification point of 78,95 ⁰ C and a sulfur content of 0.47 weight percent and the mentioned under 1 Naphthalinbeladung and catalyst loading are obtained:

3.5 7.2

25th

2. At a constant temperature of 34O ⁰ C, pure naphthalene as under 1, but with increasing catalyst loading and loading the following values are found:

Mole percent phthalic anhydride

Mole percent maleic anhydride

Mole percent naphthoquinone

Temperature (° C) 350 I 340 I.

79 4.8 0.7

78 4.7 2.4

70 3.2 6.5

For an overview, the results of Examples 1 and 2 are summarized again in the following tables:

Tabel

Raw material pure naphthalene,

Sulfur content 0.08%

Naphthalene loading ... 85 g / Nm ³ air, catalyst loading ... 25 g / kg / hour

Reaction ^{temperature (0} C)

Catalyst A 330 320 350 Catalyst B 330 320 350 340 86 86 83 340 77 69 83 84 1.4 1.2 5.5 83 4.6 3.5 1.8 1.5 0.08 0.10 0.5 5.0 4.5 7.2 0.6 0.06 1.7

Mole percent phthalic anhydride
Mole percent maleic anhydride
Mole percent naphthoquinone

Tabel

Raw material pure naphthalene,

Sulfur content 0.08%

Reaction temperature .... 340 ^{0 C}

85 Naphthalene loading (g / Nm ⁸ ) 138 Catalyst B 40.6 25th 29.5 136 Catalyst A 85 I 100 82 83 79 25th I 100 1.4 5.0 4.9 40.1 84 Space velocity over the catalyst (g / kg / hour) 0.12 1.7 3.2 73 1.5 I 29.5 4.9 Mole percent phthalic anhydride 0.06 5.6 Mole percent maleic anhydride Mole percent naphthoquinone 84.5 1.5 0.08

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Tabel

Raw material technical naphthalene,

Ep. 78.95 ° C, sulfur content 0.47%

Naphthalene loading 85 g / Nm ³ air

Catalyst loading ... 25 g / kg / hour

Reaction ^{temperature (=} C)

350

Catalyst A 340 320

350

Catalyst B
340 I 330

320

Mole percent phthalic anhydride .. mole percent maleic anhydride .. Mole percent naphthoquinone

Claims (1)

Claim: 79.5 1.6 0.8 81 1.6 0.08 83 1.1
0.12 79
4.8
0.7 78 4.7 2.4 70
3.2
6.5 Modification of the process according to patent application B 62 309 IVb / 12o for the production of phthalic anhydride by oxidation of o-xylene with oxygen-containing gases at a temperature of 250 to 420 ⁰ C in the fluidized bed using a catalyst based on vanadium pentoxide alkali pyrosulfate carrier material, which in the pores of a highly porous carrier material with a grain size of 10 to 3000μ a mixture of vanadium pentoxide and at least two pyrosulfates of different alkali metals, which is liquid under the reaction conditions and whose melting point is lower than that of potassium pyrosulfate, characterized in that naphthalene is used instead of o-xylene Starting material used. 409 5S9 / 446 0.64 © Bundesdruckerei Berlin