KR960006544B1 - Process for the smooth oxydation of ethane into a mixture of ethylene and acetic acid - Google Patents

Abstract

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Description

Controlled oxidation with a mixture of ethanol ethylene and acetic acid

The present invention relates to a process for controlled oxidation with a mixture of ethanol ethylene and acetic acid.

Acetic acid is an industrially produced product for which its various uses are well known. In addition, a mixture of ethylene and acetic acid can be used to feed the form of this mixture to the catalytic reactor for the synthesis of vinyl acetate according to its precise composition. As such, there is particular interest as a monomer widely used industrially.

French patent application 2,326,393 discloses the oxydehydrogenation of ethane in the presence of a suitable amount of water to produce ethylene and acetic acid. The catalyst used for the exothermic reaction carried out in the gas phase is based on molybdenum and at least one element.

However, the usefulness of the acetic acid yield relative to the gaseous injection of ethane with or without water can be seen by observing the presence of acetic acid as a product formed in less than ethylene.

In addition, vanadium and antimony-based "control" catalysts tested under the above conditions cause combustion of ethane or conversion of ethane to ethylene.

J. 52 (11), p 116-132 (1978), recalling the availability of catalysts based on molybdenum and vanadium in the reaction under consideration, and indicated that acetic acid formation in this process is due, in particular, to total pressure.

Regarding the type of catalyst, EP-A-0,261,264 mentions that partial pressure of water affects acetic acid formation.

Further, from US Pat. No. 4,410,752, oxydehydration to ethanol ethylene by contacting ethane with gas containing oxygen in the presence of a catalyst of the general formula VPaOx (wherein a is from 05 to 3.0 and x is a value satisfying the required valence). It is known to carry out an oxydehydration digestion reaction with ethanol ethylene by contacting a gas containing digestion with ethane, and the catalyst may preferably contain a metal promoter. The main purpose of the prior art is to produce ethylene very selectively. Finally, the reaction was carried out in a 300 to 6001C fixed bed reactor containing very excess air (in terms of volume) relative to atmospheric pressure and hydrocarbons. In addition, the seadil phosphate type catalysts used in the prior art are particularly particular crystallographic structures. Appeared to have had. The selectivity of ethylene obtained is generally higher than 50%.

At present, unexpectedly, it has been found that acetic acid can be obtained mainly by controlled oxidation of ethane using oxygen, provided that the charge pressure measured at 25C is above 2 barrelative using a specific catalyst as described in detail below. It is an object of the present invention to provide a controlled oxidation of a medium-phase ethanol ethylene and acetic acid using an oxygen-containing gas, which comprises: (a) bonding to phosphorus-based titanium-based supports; And in the presence of an oxygen-containing catalyst, (b) the reaction is carried out under conditions in which the charge pressure measured at 25 C is at least 2 bar relative.

The main feature of the invention lies in the catalyst used. As mentioned above, the catalyst contains vanadium, phosphorus and oxygen attached on a titanium oxide based support.

Titanium oxide can be selected from the forms of anatas TiO 2, rutile TiO 2 and TlO / B. Preference is given to using annatas TiO 2.

Titanium oxide is generally represented as 25 to 99.5% of the catalyst composition and 50 to 99.9% by weight of the present invention shows excellent effects.

The catalyst phase supported by the titanium oxide used in the present invention contains at least 0.01 phosphorus atom per vanadium atom, preferably at least 0.5, and oxygen can satisfy the necessary valences of V and P in the VpaOx phase. It should be present in the required amount as possible. If the atomic ratio of P / V is less than 0.5, a rather excessive combustion may occur, damaging the desired reaction.

If the phosphorus atom is present in an amount exceeding 5.0 or more relative to the vanadium atom, no benefit is seen, and indeed, at this preload, a decrease in acetic acid selectivity is observed. It is desirable that the amount of personnel does not exceed 3 per vanadium atom.

Generally, the amount of vanadium present in the catalyst composition, expressed as weight percent of metal vanadium, is 0,05 to 35%. In order to obtain the excellent effect in the present invention, 0.20 to 10% by weight of the composition # is taken out.

Catalyst compositions useful for carrying out the present invention can be prepared in a number of ways. In practice, supported VPaOx catalyst formulations are known in the art, e.g. NH ₄ VO by tartaric acid in an aqueous medium under addition of orthophosphoric acid. VPaOx catalysts supported on silica and aluminum phosphate, obtained by incorporating a support corresponding to an aqueous solution produced by the attack of ₃ [Creation, J. Catal. 117, p 301-310 (1989)], or a VPaOx catalyst supported on alumina, obtained by impregnating a support corresponding to an aqueous solution produced by the attack of V2O5 with oxalic acid in an aqueous medium under addition of orthophosphoric acid. (Appl Catal. 45, p 1-7 (1988)).

In general, these preparations require dissolution of the vanadium compound and addition of the desired amount of orthophosphoric acid before it is obtained by impregnation of the support in the solution. The solution dissolves pentavalent vanadium compounds (V ₂ O ₅ , VOC1 ₃ , VOBr ₃ , VClr ₃ , VC1 ₅ , NH ₄ VO ₃ ) or tetravalent vanadium compounds (VO ₂ , VOSO ₄ , VOCI ₂ , After dissolving VOBr ₂ , VC1 ₄ ) or reducing in a pentavalent vanadium compound (V ₂ O ₄ , VOC1 ₃ , VC1 ₄₁ , NH ₄ VO ₃ ) medium: obtained by adding the desired amount of orthophosphoric acid solution can do.

As a reducing agent in the pentavalent vanadium compound, organic acids such as oxalic acid, cytoric acid, tartaric acid and maleic acid (see J. Catal. 34, p 345 to 355 (1974)), hydrazine described in U.S. Patent No. 4,410,752, or United States Patent As described in 4,085,122, concentrated hydrochloric acid may be used alone or in the presence of acids such as formic acid, acetic acid, lactic acid and boric acid having non-oxidizing properties.

The support is impregnated with this solution, dried in air and then calcined. Calcination is carried out in air at 250 to 900C, preferably 350 to 750C.

These catalyst compositions can take various forms such as powders, beads, extrudates and milled products.

-50 to 99% by weight of anatas tanthanum oxide,

It is comprised from the VPaOx phase in which metal vanadium shows 0.20 to 10 weight% (where a is 0.5-3.0 and x is an essential value satisfying valence requirement).

The catalyst composition is advantageously used in the present invention by attaching itself onto solid particles or coating the solid particles with the composition.

When such solids are used, they can be selected from those commonly used to prepare naturally supported catalysts, as long as these materials are chemically inert to the reaction. For example, mention may be made of solids of oxides of silica, alumina, magnesium, zirconium, lanthanum and cerium, clays, zeolites, silicon carbide and mixtures of these compounds.

When these solids are used to prepare the catalysts used in the present invention, they are represented by 20 to 92% by weight of the total weight.

More specifically as such preparations may be mentioned clay beads, and compositions containing vanadium, phosphorus and oxygen are supported by academia titanium coating these beads.

As mentioned at the outset of the present invention, another important feature of the method according to the invention is that the filling pressure measured at 251 C is applied above 2 bar relative. There is no benefit at pressures above 100 bar reIative. In order to obtain the good effect of the present invention, the total pressure measured at 25C should be 2-30 barrelrel.

According to the invention, ethane is contacted with a gas containing oxygen. Due to the strong exothermic nature of the reactions used and the risk of spontaneous ignition of the ghs mixtures containing ethane and oxygen under pressure, a mixture containing excess alkanes relative to oxygen is used to preserve the catalytic and selective properties of the reaction. It is preferable. In order to obtain the excellent effect of the present invention, the volume ratio of ethane / oxygen should be larger than 1. 6 to 60 are preferred.

In the present invention, inert gas is slightly mixed and oxygen or optionally pure oxygen rich air can be used. Preferably pure oxygen is used.

Water can also be added to the reaction mixture. The volume ratio of water / ethane for obtaining an excellent effect is 0 to 1. 5. Preferably it is 0.02-0.7.

The reaction of oxygen-containing gas and ethane in the presence of the catalyst described above is carried out in the steam sand. The reaction temperature is generally 150 to 600C. The upper limit is determined by the spontaneous ignition temperature of the reaction mixture, which is a function of the total pressure and the residence time of the reaction mixture in the reactor. The reaction temperature for carrying out the excellent effects of the present invention is 175 to 400C.

The contact time (∞c) in the reactor, defined as the ratio of the volume (cm 3) of catalyst in the reactor to the fill flow rate (N cm 3 / s) in the reactor, is 0.05-10 s. Preferably it is 0.1-5s.

Gas phase acetic acid generated from the reactor can be condensed and recovered, for example in the form of an aqueous solution. It can then be extracted from the aqueous solution according to known methods such as distillation, solvent extraction or extractive distillation.

The following examples illustrate the invention.

The results are shown in terms of the degree of conversion of ethane, the selectivity to ethylene and acetic acid, and the rate of acetic acid production, and these variables are defined as follows.

- conversion of ethane is also _{& (DC C2H6) = (C} 2 H 6 -C ₂ H ₆ mole number of the mole number of the discharge flow rate) / (number of moles of C ₂ H ₆ flow rate) Selectivity mol% of ethylene

Sc _{2H 4} = (moles of C ₂ H ₄ effluent) × / (moles of C ₂ H ₆ inflow—moles of C ₂ H ₆ effluent) Select mole% for acetic acid

S _ACOH = (moles of CH ₃ COOH outflow) x 100 / (moles of C ₂ H ₆ inflow-moles of C ₂ H ₆ outflow)

The production rate of acetic acid PAco1 {(g / h // catalyst) is the number of grams of acetic acid produced per hour per 1 flter of catalyst injection

Catalyst test method:

A 20 cm ³ test catalyst is placed in an Inconel reactor 25 cm in length and 2 cm in diameter. The catalyst activity is measured 45 minutes after the reaction reflux under the desired temperature and pressure conditions. The flow rate of the gas is ascertained by measuring the mass flow. The flow rate of water is measured using a metering pump. The liquid is vaporized in a stainless steel reactor where the temperature is maintained at 275 C. The reactor is filled with small, 50 cm ³ alumina beads that are previously calcined at 850 C in air to provide a mixing role. The reactor is brought to temperature through a flowing sand bath.

The efficiency is calculated from the results provided by the two gas chromatographic analyzers arranged at the outlet of the reactor. Equipped with a thermal conductivity detector can separate CO ₂ , C ₂ H ₄ , O 2, N ₂ and CO and determine their elution order. Equipped with a phantom ionic detector can separate C ₂ H ₄ , C ₂ H ₆ and acetic acid and determine their elution order.

Catalysis and Big Conditioning:

Example 1

Preparation of Catalyst A based on (VO) ₂ P ₂ O ₇ according to the prior art:

240 ml of isobutyl alcohol and 160 ml of benzyl alcohol are placed in a glass reactor provided with an anchor rotary stirrer, a dropping funnel, a thermometer and a cooler and a Gail device.

To the above solution is added 40 g of powder V ₂ O ₄₁ and the resulting suspension is refluxed at 110 C for 2 hours, followed by 58.3 g of 85% orthophosphoric acid via a dropping funnel.

The suspension is refluxed again at 110 C for 2 hours. The solvent is removed by distillation.

The paste obtained is dried in air at 150C for 6 hours. The solid obtained is triturated and then calcined in air at 400C for 15 hours.

The powder obtained is coated on a support composed of clay beads 5 mm in diameter.

After coating (VO) ₂ P ₂ O ₇ content is 16% by weight.

Example 2

Preparation of B of a catalyst based on Mo _0.73 V _0.18 Nb _0.09 according to the prior art.

500 m1 of deionized water, 57.6 g of ammonium hepta molybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O and 9.2 g of powdered ammonium meta in a glass reactor provided with an anchor rotary stirrer, thermometer and cooler and heating device Vanadate NH ₄ VO ₃ is introduced.

The suspension is refluxed at 90C with stirring for 30 minutes.

After cooling, 12.2 g of niobium ethoxide Nb (C ₂ H ₄₁ O) ₄₁ is added to the obtained solution.

The resulting suspension is refluxed at 90 C with stirring for 2 hours. The suspension is then concentrated and dried.

The resulting paste is dried in 120C air for 12 hours and then calcined in 350C air for 5 hours.

The obtained powder is gouted on the same support composed of clay beads as in the case of catalyst A. After gouting the Mo _0.73 V _0.18 Nb _0.19 content is 19% by weight.

Example 3

Preparation of Catalyst C According to the Invention:

7. 37 g of powdered oxalic acid are dissolved under stirring in 16.25 ml of deionized water in a heated state. When oxalic acid is dissolved, 3.27 g of powder V ₂ O ₄₁ is added to this solution.

Completely dissolve V ₂ O ₄₁ under stirring while heated to cool the solution

2.83m1 of 85% orthophosphoric acid is added to this solution at room temperature. Thus, a solution consisting of the solution to be impregnated with the TiO ₂ support is obtained.

TiO ₂ support is powdered anatase acid titanium with a specific surface area of 105 m ² / g and a total pore volume of 0.35 cm ³ / g. 45 g of the support is impregnated into the solution in a rotary bowl granulator.

The resultant powder is rolled in 150C air for 6 hours and then calcined in 500C air for 3 hours. After calcination, the recovered solid is ground. A fragment smaller than 125 μm remains.

25 g of this powder are coated onto 100 g of clay beads in the same manner as for Catalysts A and B.

The coated catalyst is re-dried for 6 hours in 150C air and then calcined for 3 hours in 500C air. After coating, the content of catalyst C is 12.7% by weight.

Catalyst test conditions:

Catalysts A, B and C are tested under the following conditions.

The catalyst dosage is 20 cm ³ of catalyst coated on clay beads. The flow rate of ethane is 60N1 / h, the flow rate of oxygen is 5m1 / h (represented as a liquid) and the ethane / oxygen equivalent ratio is 15 (volume ratio).

The total pressure measured at 25C is 10 bar relative.

The contact time equivalent to GHSV 3510h- ¹ is 1.03 s.

The results are shown in Table 1.

Table I

Example 4

Preparation of Catalyst D According to the Invention

3.15 g of tartaric acid are dissolved in a heated state in 17 ml of deionized water under stirring. After dissolution, 1,40 g of powder V ₂ O ₄₁ is added to the solution.

After dissolving V ₂ O ₄₁ under agitated conditions, the solution is returned to room temperature.

2 03 g of 85% orthophosphoric acid is then added to the solution. In this way an impregnation solution is obtained.

45 g of Anatas TiO ₂ (specific surface area 45 m ² / g, total pore volume of 0.38 cm ³ / g) is impregnated into the solution obtained above in a rotating bowl granulator.

The powder is dried in 150C air for 6 hours and then calcined in 500C air for 3 hours.

The obtained 25 g of powder was coated on 100 g of clay beads having a diameter of 5 mm. The resultant was dried for 6 hours in 150C air and dried for 3 hours in 500C air. The coating rate was 17.3%.

Example 5

Preparation of Catalyst E According to the Invention

1. Dissolve 82 g citric acid under heating in 16 ml of deionized water under heating, after dissolving, add 0.81 g of powder V ₂ O ₄₁ to the solution.

Dissolve V ₂ O ₄₁ under stirring in a heated state and return the solution to room temperature.

Subsequently, 1.17 g of 85% orthophosphoric acid is added to the solution. Thus an impregnation solution is obtained.

26 g of rutile TiO ₂ (specific surface area 30 m ² / g, total pore volume 0 58 cm ³ / g) are impregnated into the solution obtained above in a rotating bowl granulator.

The powder is dried in 150C air for 6 hours and then calcined in 400C air for 3 hours.

25 g of the powder obtained are coated onto 100 g of clay beads having a diameter of 5 mm. After drying for 6 hours in air at 150C and calcining for 3 hours in air at 400C, the coating rate was 16,6%.

Example 6

Preparation of Catalyst F According to the Invention

15 g of oxalic acid are dissolved under stirring in 25m1 of deionized water in a Gale state. After dissolution, 6.O 4 g of powder V ₂ O ₄₁ is added to the solution.

Dissolve V ₂ O ₄₁ under stirring in a heated state and return the solution to room temperature.

Then, 22.85 g of 85% orthophosphoric acid is added to the solution. Thus an impregnation solution is obtained.

45 g of Anatas TiO ₂ (specific surface area 275 m ² / g), total pore volume 1.18 cm ³ / g) are impregnated into the solution obtained above in a rotating bowl granulator.

The powder is dried in 150C air for 6 hours and then calcined in 600C air for 3 hours.

The obtained 25 g of powder was coated on 100 g of clay beads having a diameter of 5 mm. After drying for 6 hours in 150C air and calcining for 3 hours in 600C air, the coating rate was 13.6%.

Example 7

Preparation of Catalyst G according to the invention:

8.2 g of vanadil sulfate VOSO ₄ 5H ₂ O are dissolved under stirring in 17 ml of deionized water under heating.

After dissolution, the solution is returned to room temperature.

1.84 g of 85% orthophosphoric acid is then added to the solution. In this way an impregnation solution is obtained.

45 g of Anatas TiO ₂ (specific surface area 105 m ² / g, total pore volume 0.35 cm ³ / g) is impregnated into the solution obtained above in a rotating bowl granulator.

The powder is dried in 150C air for 6 hours and then calcined in 500C air for 3 hours.

25 g of the powder obtained are coated onto 100 g of clay beads having a diameter of 5 mm. After drying for 6 hours in 150C air and calcining for 3 hours in 500C air, the gouting rate was 18.6%.

Example 8

Preparation of Catalyst H According to the Invention

1. 33 g of oxalic acid is dissolved under stirring in 15 ml of deionized water under heating.

After dissolution, 0. 59 g of powder V ₂ O ₄₁ are added to the solution.

After dissolving V ₂ O ₄₁ under stirring in a heated state, the solution is returned to room temperature.

Then, 0. 86 g of 85% orthophosphoric acid is added to the solution. In this way, an anti-precipitation solution is obtained.

19 g of TiO ₂ (B) (specific surface area 35 m ² / g, total pore volume 0.8 cm ³ / g) is impregnated into the solution obtained above in a rotating bowl granulator.

The powder is dried in 150C air for 6 hours and then calcined in 350C air for 3 hours.

The obtained 20 g of powder was coated on 100 g of clay beads having a diameter of 5 mm. After drying for 6 hours in air at 150 C and calcining for 3 hours in air at 600 C, the coating rate was 14%.

Catalyst test conditions;

As described above, the catalysts D to H are tested under the same conditions as the catalysts A to C. The results are shown in Table II.

Table II

Claims (13)

A process for controlled oxidation of a vaporous mixture of ethanol ethylene and acetic acid using a gas containing oxygen, the reaction comprising: a) in the presence of a catalyst containing vanadium, phosphorus and oxygen attached on a titanium oxide based support; b) characterized in that the total pressure measured at 25C is carried out under conditions of at least 2 bar relative to the in-situ pressure. The method of claim 1, characterized in that the titanium oxide Ana Tasman TiO _2, rutile TiO ₂ and TiO ₂ (B) selected from. The process according to claim 1 or 2, characterized in that the titanium oxide represents 25 to 99.5% by weight of the catalyst composition (VPaOx, TiO ₂ ), The process according to claim 1 or 2, wherein the attached vanadium represents 0.05-35% by weight of the catalyst composition (VPaOx, TiO ₂ ). The method of claim 1 or 2, wherein a is at least 0.1 on the VPaOx. The method of claim 1 or 2, wherein a does not exceed 5 on the VPaOx. 3. Process according to claim 1 or 2, characterized in that the catalyst composition (VPaOx, TiO ₂ ) is attached on solid particles which are chemically inert to the reaction. 8. A method according to claim 7, wherein the solid represents 20-92% by weight of the total. 8. The method of claim 7, wherein the solid particles are clay beads and the catalyst composition coats the beads. 3. Process according to claim 1 or 2, characterized in that the volume ratio of ethane / oxygen is greater than one. The process according to claim 1 or 2, characterized in that the reaction temperature is 150-600C. The method according to claim 1 or 2, wherein the titanium oxide is 25-99.5% by weight of the catalyst composition (VPaOx, TiO ₂ ) and the attached vanadium is 0.05-35% by weight of the catalyst composition (VPaOx, TiO ₂ ). How to 13. The method of claim 12 wherein a is 0.1-5 on VPaOx.