WO2000010956A1 - Method for making methacrolein from isobutylene by redox reaction - Google Patents

Abstract

The invention concerns the use of a solid composition of mixed oxides of formula (I): MO12AaBibFecDdEeFfOx wherein A is at least one among tungsten, chromium and tin; D is at least one among nickel and cobalt; E is at least one among potassium, rubidium and caesium; F is at least one among silicium, aluminium, zirconium and titanium; a ranges between 0 and 5, inclusively; b ranges between 0.5 and 5, inclusively; c ranges between 0.1 and 10, inclusively; d ranges between 2 and 20, inclusively; e ranges between 0 and 1, inclusively; f ranges between 0 and 50, inclusively; and x is the amount of oxygen bound with the other elements and depends on their oxidation conditions, for producing methacrolein by oxidising isobutylene, said solid composition reacting with isobutylene by redox reaction (1): oxidisedSOLID + Isobutylene } reducedSOLID + Methacrolein. The method for making methacrolein consists in reacting gaseous isobutylene with a solid composition of formula (I), operating at a temperature ranging between 200 and 600 DEG C, under pressure ranging between 1,01 X 10<4> and 1.01 x 10<6> Pa (0.1 to 10 atmospheres), and a retention from 0.1 second to 90 seconds, in the absence of molecular oxygen, thereby producing said redox reaction (1).

Description

_P ROCÉD _É methacrolein MANUFACTURING FROM JET ISOBUTENE ORP

The present invention relates to the manufacture of methacrolein from isobutene by oxidation according to a redox reaction. The invention also relates to the use of a solid composition of mixed oxides as a redox system in said reaction.

Industrial production of methacrolein is currently carried out by catalytic oxidation of isobutene in the vapor phase. All efforts to improve this process have so far focused on the development of catalysts giving the highest possible conversion rate of isobutene and the highest possible selectivity for the desired methacrolein.

Thus, French Patent No. 2,093,773 describes the manufacture of carbonyl compounds by catalytic oxidation _of an olefin chosen from propylene or isobutene in the vapor phase, with molecular oxygen, in the presence of a catalytic oxide, the composition of the catalytic elements, expressed in atomic ratio, is as follows:

005-1, 0C ° 2, ₀ -2 ₀ , _θ Fe _{0 /!} _! (),

005-1.0

with + Mo = 12.0 and Z representing an alkali metal.

This catalyst can be prepared by mixing aqueous solutions of ammonium olybdate and ammonium paratungstate, adding solutions of cobalt nitrate, iron nitrate and bismuth nitrate to the aqueous mixture, then adding an aqueous solution. of hydroxide or carbonate of an alkali metal, then colloidal silica as a source of silicon, by molding the substance obtained and calcining it at 350-600 ° C in a stream of air. Japanese patent Showa 45-125 359 describes a process for the production of methacrolein in the vapor phase by catalytic oxidation of isobutene by air or oxygen, in the presence of a catalyst of formula:

^Nl a ^Co b ^Fe c ^Bl d ^Me e ^H h ^Mo f ° g

in which: a = 0 - 20; b = 0 - 20 with a + b between 0.5 and 20; c = 0.5 - 8; • d = 0, l - 7;

0 <e <2; h = 0 - 0.3; f = 12; g = 36 - 90; • Me is one of Sn, Zn, W, Cr, Mn and Ti; and

H is at least one of K, Rb and Cs.

To prepare this catalyst, it is possible to add to an aqueous solution of a molybdenum compound (ammonium molybdate, molybdic acid or molybdenum oxide), aqueous solutions of compounds of Ni, Co, Fe, K (and / or Rb , Cs), Bi and

Me, then add a support such as alumina, silicon carbide and silica (silica sol or silica gel), then heat the resulting mixture to dryness, calcine it at about 500 ° C, and transforms into pellets. French Patent No. 2,534,904 describes a catalyst for the production of unsaturated aldehydes, in particular acrolein and methacrolein, by vapor phase oxidation of propylene, isobutylene or tertiary butanol with a gas containing molecular oxygen. This catalyst is represented by the general formula:

Bi _ab Fe _c Mo _d A _e B _f C _g D _h O _χ

in which: - A represents nickel and / or cobalt; B represents one or more elements chosen from alkali and alkaline earth metals and thallium; C represents one or more elements chosen from phosphorus, arsenic, boron, antimony, tin, cerium, lead and niobium;

D represents one or more elements chosen from silicon, aluminum, zirconium and titanium; and

- a, b, c, d, e, f, g, h and x represent the atomic proportions of the individual elements, and if d is taken equal to 12: a is between 0.1 and 10, preferably between 0, 5 and 5; b is between 0.5 and 10, preferably between 0.5 and 4; - c is between 0.1 and 10, preferably between 0.2 and 5; e is between 2 and 20, preferably between 3 and 10; f is between 0.001 and 10, preferably between 0.02 and 2; g is between 0 and 10, preferably between 0 and 5; h is between 0 and 30, preferably between 0.5 and 10; and - x is the quantity of oxygen bound to the other elements and depends on their oxidation states, the bismuth being introduced in the form of an oxide previously obtained by calcination between 600 and 900 ° C. of a mixture of a compound bismuth and a tungsten compound.

The Applicant Company has now discovered that methacrolein can be manufactured by oxidation of isobutene in the gas phase in the absence of molecular oxygen, by reacting isobutene with a particular solid composition of mixed oxides, which acts as a redox system and provides the oxygen necessary for the reaction. The advantages of this new process, using the redox route and no longer the catalytic route, are as follows:

- the limitation of the overoxidation of the products formed which takes place in the presence of molecular oxygen; according to the present invention, because one operates in the absence of molecular oxygen, the formation of CO _χ (carbon monoxide and carbon dioxide), degradation products, is reduced, which makes it possible to increase the selectivity to methacrolein, as shown below by Comparative Examples 4 and 8; the selectivity for methacrolein remains good when the reduction rate of the solid composition increases;

- The solid composition, once it has undergone a reduction and a progressive loss of its activity, is easily regenerable by heating in the presence of oxygen or of a gas containing oxygen after a certain period of use; after regeneration, the solid returns to its initial activity and can be used in a new reaction cycle; the separation of the stages of reduction of the solid composition and of regeneration thereof makes it possible: to increase the selectivity in methacrolein; and to increase the partial pressure of isobutene, such a partial pressure of supply of isobutene being no longer limited by the existence of an explosive zone by the isobutene + oxygen mixture.

The present invention therefore firstly relates to the use of a solid composition of mixed oxides of formula (I):

^Mo 12 ^A a ^Bi b ^Fe c ^D d ^E e ^F f ° x <*> in which:

- A is at least one of tungsten, chromium and tin;

- D is at least one of nickel and cobalt; - E is at least one of potassium, rubidium and cesium;

- F is at least one of silicon, aluminum, zirconium and titanium; - a is between 0 and 5, limits included;

- b is between 0.5 and 5, limits included;

- c is between 0.1 and 10, limits included;

- d is between 2 and 20, limits included;

- e is between 0 and 1, limits included; - f is between 0 and 50, limits included; and

- x is the quantity of oxygen linked to the other elements and depends on their oxidation states, in the production of methacrolein by oxidation of isobutene, said solid composition reacting with isobutene according to the redox reaction (1):

SOLID _{Q de} + Isobutene - REDUCED ^{SOLID + Metnac} ^ olein (1).

The oxides of the different metals used in the composition of the mixed oxide of formula (I) can be used as raw materials in the preparation of this composition, but the raw materials are not limited to the oxides; as other raw materials, there may be mentioned:

- in the case of molybdenum, ammonium molybdate and molybdic acid; - in the case of tungsten, ammonium tungstate and tungstic acid; in the case of chromium, chromium nitrate; and in the case of tin, stannous chloride bihydrate; in the case of bismuth, iron, nickel, cobalt, nitrates, carbonates and hydroxides, such as bismuth nitrate, ferric nitrate, nickel nitrate, cobalt nitrate; in the case of component E, hydroxides, carbonates or nitrates; and, in general, all the compounds capable of forming an oxide by calcination, namely salts metals of organic acids, metal salts of mineral acids, complex metal compounds, organic metal compounds, etc.

The source of silicon is generally constituted by colloidal silica.

The present invention relates to a process for the manufacture of methacrolein from isobutene, a process according to which the gaseous isobutene is reacted with a solid composition of formula (I) as defined above, operating at. a temperature of 200 to 600 ° C, in particular 250 to 450 ^o C, under a pressure of 1.01 x 10 to 1.01 x 10 ⁶ Pa (0.1 to 10 atmospheres), in particular 5.05 x 10 ⁴ at 5.05 x 10 Pa (0.5 to 5 atmospheres) and with a residence time of 0.01 second to 90 seconds, in particular from 0.1 second to 30 seconds, in the absence of molecular oxygen, achieving thus the redox reaction (1) as indicated above.

According to particular embodiments of the present invention, it is possible to introduce the isobutene gas in admixture with an inert gas, such as nitrogen, and / or with water (water vapor).

During the redox reaction (1), the solid composition undergoes a reduction and a progressive loss of its activity. This is why, once the solid composition has gone to the reduced state, the regeneration of said composition is carried out according to reaction (2):

S0LIDE _reduced + 0 ₂ - S0LIDE _oχydé (2)

by heating in the presence of an excess of oxygen or of an oxygen-containing gas at a temperature of 250 to 500 ° C., for the time necessary for the reoxidation of the solid composition.

After regeneration, which can be carried out under conditions of temperature and pressure identical to, or different from, those of the redox reaction, the solid composition regains initial activity and can be used in a new reaction cycle.

The redox reaction (1) and the regeneration can be carried out in a two-stage device, namely a reactor and a regenerator which operate simultaneously and in which two charges of solid composition alternate periodically; the redox reaction (1) and the regeneration can also be carried out in the same reactor by alternating the reaction and regeneration periods. The preparation of methacrolein according to the invention is carried out according to a stoichiometric and non-catalytic reaction.

The following Examples illustrate the present invention without, however, limiting its scope. In the formulas given in these Examples, x is the amount of oxygen bound to the other elements and depends on their oxidation states.

The conversions, selectivities and yields are defined as follows:

Number of moles of isobutene that reacted

Conversion (%) = x 100

Number of moles of isobutene introduced

Selectivity Number of moles of methacrolein formed in (%) = x 100 methacrolein Number of moles of isobutene that reacted

EXAMPLE 1

(a) Preparation of a solid of formula

^Mo 12 ^Cθ 6 ^Fe 3 ^Bi l ^Cr 0.5 ^Si l ^K 0, l

At room temperature, 262.7 g of Cθ (N0 ₃ ) ₂ , 6H ₂ 0, 182.3 g of Fe (N0 ₃ ) ₃ , 9H ₂ 0 and 1.5 g of K 0 ₃ are dissolved in 420 ml of 'distilled water. Also at room temperature, 76.7 g of Bi (NO ₃ ) _3.5 H ₂ 0 are dissolved in 100 ml of distilled water acidified with 16.67 ml of HN0 ₃ at 68% of volume. Still at room temperature, 30.1 g of Cr (NO ₃ ) ₃ , 9H ₂ 0 are dissolved in 20 ml of distilled water. At 40 ° C., 318.7 g of (NH ₄ ) ₆ Mo are dissolved _. 0 ₂₄ , 4H ₂ 0 in 900 ml of distilled water. The solution containing bismuth and that containing chromium are successively poured, with stirring, into the solution containing Co, Fe and K. The resulting solution is then poured, still with stirring, into the solution containing molybdenum. 23.7 g of colloidal silica (40% by mass) are then added thereto. The resulting mixture is heated to 80 ° C for 1.5 hours, then dried at 140 ^β C for 12 hours. The solid obtained is calcined for 6 hours at 500 ° C. in air. The various metals are present in this solid in the atomic ratios as indicated in the title of this example.

(b) Preparation of methacrolein from isobutene by redox reaction

200 mg of this solid is charged into a tubular reactor at 340 ° C., then it is swept by a continuous flow of 12 ml / min of helium. 1.9 x 10 ^-6 mole of ¹ isobutene is injected onto the solid, in order to conduct the redox reaction of the isobutene and the solid. Isobutene is converted to 99.8% with a selectivity to methacrolein of 77.3%.

EXAMPLE 2 After having carried out the reaction of Example 1 (b), the same solid is again subjected to four successive injections of isobutene, under the same conditions as in Example 1. The performances are reported in Table 1 . Table 1

EXAMPLE 3

After the reducing treatment of Example 2, the solid is regenerated for 1 hour in air at 340 ° C., then replaced under a stream of helium. Four successive new injections of 1.9 x 10 mole of isobutene are sent to the solid, in order to conduct the redox reaction of the isobutene and the solid. The performances obtained are reported in Table 2.

Table 2

EXAMPLE 4 (comparative) Preparation of methacrolein by the catalytic route

3 ml of the solid prepared according to Example 1 (a) are loaded into a tubular reactor. A mixture consisting of ¹ isobutene / air / water / nitrogen = 6/63/15/16% by volume is injected onto the solid at atmospheric pressure at a salt bath temperature of 340 ° C. The solid is here the catalyst for the reaction. The contact time, expressed relative to the total volume of the catalytic bed, is 2.25 s. After 16 hours of reaction, the conversion of isobutene is 91.6% with a selectivity to methacrolein of 76.4%.

EXAMPLE 5

(a) Preparation of a solid of formula Mo ₁₂ ^Cθ 3.5 ^Fe 0.8 ^Bi l, l 0.5 ^Si l, 4 ^K 0.5

60.9 g of Co (NO ₃ ) ₂ , 6H ₂ 0 are dissolved in 20 ml of distilled water.

Also dissolved 20.2 g of Fe (N0 ₃ ) ₃ , 9H ₂ 0 in 15 ml of distilled water, and 31.2 g of Bi (N0 ₃ ) ₃ , 5H ₂ 0 in 30 ml of acidified distilled water with 6 ml of 68% HN0 ₃ .

Separately, the solution is dissolved by heating and stirring 127.4 g of (NH ₄ ) ₆ Mo ₇ 0 ₂₄ , 4H ₂ 0 in 150 ml of water, then 7.4 g of 0 _{3 are added} .

The aqueous solution containing cobalt is introduced dropwise over 20 minutes into the aqueous solution of ammonium salts. The ferric solution is then introduced in 10 minutes, then the solution containing bismuth in 15 minutes. In the resulting gel, a solution obtained by dissolving 2 g of KOH and 12.8 g of colloidal silica (40% by mass) in 15 ml of water is added over 10 minutes. The gel thus obtained is kneaded for 1 hour at room temperature, then 1 hour at 70 ° C.

The gel is then dried at 130 ° C for

18 hours. The solid obtained calcined for 9 hours at 450 ° C. in air. The different metals are present in this solid in the atomic ratios as indicated in the title of this example. (b) Preparation of methacrolein from isobutene by redox reaction

200 mg of this solid is charged into a tubular reactor at 370 ° C., then it is swept with a continuous flow of 12 ml / min of helium. 1.9 x 10 mole of isobutene is injected onto the solid, in order to conduct the redox reaction of the isobutene and the solid. Isobutene is converted to 96.2% with a selectivity to methacrolein of 82.9%.

EXAMPLE 6

After carrying out the reaction of Example 5 (b), the same solid is again subjected to two successive injections of isobutene, under the same conditions as in

1 • Example 5. The performances are reported in Table 3.

Table 3

EXAMPLE 7

After the reducing treatment of Example 6, the solid is regenerated for 1 hour in air at 370 ° C., then replaced under a stream of helium. Three further successive injections of 1.9 x 10 ^-6 mole of isobutene are sent to the solid, in order to conduct the redox reaction of the isobutene and the solid. The performances obtained are reported in Table 4. Table 4

EXAMPLE 8 (comparative): Preparation of methacrolein by the catalytic route

3 ml of the solid prepared according to Example 5 (a) are loaded into a tubular reactor. A mixture consisting of isobutene / air / water / nitrogen = 6/63/15/16% by volume is injected onto the solid at atmospheric pressure at a salt bath temperature of 355 ° C. The solid is here the catalyst for the reaction. The contact time, expressed relative to the total volume of the catalytic bed, is 2.25 s.

After 16 hours of reaction, the conversion of isobutene is 88.4% with a selectivity to methacrolein of 81.3%.

Claims

CLAIMS 1 - Use of a solid composition of mixed oxides of formula (I): Mo12AaBibFecDdEeFf°x W in which: - A is at least one among tungsten, chromium and tin; - D is at least one of nickel and cobalt; - E is at least one of potassium, rubidium and cesium; - F is at least one of silicon, aluminum, zirconium and titanium; - a is between 0 and 5, limits included; - b is between 0.5 and 5, limits included; - c is between 0.1 and 10, limits included; - d is between 2 and 20, limits included; - e is between 0 and 1, limits included; - f is between 0 and 50, limits included; and - x is the quantity of oxygen linked to the other elements and depends on their oxidation states, in the manufacture of methacrolein by oxidation of isobutene, said solid composition reacting with isobutene according to the redox reaction (1) : S0LIDEo de + Isobutene → S0LIDEreduced + Methacrolein (1). 2 - Process for manufacturing methacrolein from isobutene, characterized in that gaseous isobutene is reacted with a solid composition of formula (I) as defined in claim 1, operating at a temperature from 200 to 600 "C, under a pressure of 1.01 x 104 to 10.1 x 106 Pa (0.1 to 10 atmospheres), and with a residence time of 0.01 seconds to 90 seconds, in absence of molecular oxygen, thus carrying out the redox reaction (1) as indicated in claim 1. 3 - Process according to claim 2, characterized in that the gaseous isobutene is introduced into a mixture with an inert gas such as nitrogen and/or with water. 4 - Process according to one of claims 2 and 3, characterized in that the redox reaction (1) is carried out at a temperature of 250 to 450° C. 5 - Method according to one of claims 2 to 4, characterized in that 1 'the redox reaction (1) is carried out under a pressure of 5.05 x 104 to 5.05 x 105 Pa (0.5 at 5 atmospheres). 6 - Method according to one of claims 2 to 5, characterized in that 1 'the redox reaction is carried out (1) with a residence time of 0.1 seconds to 30 seconds. 7 - Method according to one of claims 2 to 6, characterized in that once the solid composition has passed into the reduced state, the regeneration of said solid composition is carried out according to the reaction (2): _Reduced SOLID + 0 ₂ - _Oxidized SOLID (2) by heating in the presence of an excess of oxygen or an oxygen-containing gas at a temperature of 250 to 500 °C, for the time necessary for the reoxidation of the solid composition. 8 - Method according to claim 7, characterized in that the redox reaction (1) and the regeneration are carried out in a two-stage device, namely a reactor and a regenerator which operate simultaneously and in which two charges alternate periodically of solid composition. 9 - Process according to claim 7, characterized in that the redox reaction (1) and the regeneration are carried out in the same reactor by alternating the reaction and regeneration periods.