FR2782513A1 - Process for the preparation of methacrolein from isobutene by means of a redox reaction using a mixed oxide composition including molybdenum, bismuth, iron, and four other elements - Google Patents

Abstract

A vapor phase oxidation of isobutene is carried out using an oxide composition which acts as a redox system providing the oxygen necessary for the reaction The use of a mixed oxide composition of formula (I):- Mo12AaBibFecDdEeFfOx (I) A = W, Cr or Sn ; D = Ni or Co ; E = K, Rb or Cs ; F = Si, Al, Zr or Ti ; a = 0 - 5 ; b = 0.5 - 5 ; c = 0.1 - 10 ; d = 2 - 20 ; e = 0 - 1 ; f = 0 - 50 (limits included) ; and x = amount of oxygen linked to the other elements depending on their oxidation states ; -is claimed, in the manufacture of methacrolein by oxidation of isobutene according to the reaction :- SOLID (oxidized) + isobutene -------------------- SOLID(reduced) + methacrolein (1) An Independent claim is also included for the redox process using the oxide composition (I)

Description

METHOD FOR MANUFACTURING METHACROLEIN FROM ISOBUTENE

BY REDOX REACTION AND USE OF A SOLID COMPOSITION

MIXED OXIDES AS A REDOX SYSTEM IN THE SAID REACTION

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

redox system in said reaction.

The industrial production of methacrolein is currently carried out by catalytic oxidation of isobutene in the vapor phase. All efforts to improve this process have hitherto focused on the development of catalysts giving the highest possible conversion rate of isobutene as well as 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 whose composition of the catalytic elements, expressed in atomic ratio, is as follows: C02.0-20, OFeO, 1-10, oBio, 1-10, oWo, 5-10.0oM2.0-11, sSio, 5-15, ozo, 005-1.0

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

This catalyst can be prepared by mixing aqueous solutions of ammonium molybdate and ammonium paratungstate, adding solutions of cobalt nitrate, iron nitrate and bismuth nitrate to the aqueous mixture, and then adding an aqueous solution. hydroxide or carbonate of an alkali metal, then colloidal silica as a source of silicon, by molding the obtained substance and calcining it at 350-600 C in a current of air. Japanese patent Showa 45-125 359 describes a process for the manufacture of methacrolein in the vapor phase by catalytic oxidation of isobutene with air or oxygen, in the presence of a catalyst of formula: NiacobFecBidMeeHhMofOg in which: * a = 0 - 20; * b = o - 20 with a + b between 0.5 and 20; * c = 0.5 - 8; * d = 0.1 - 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, one can 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 the resulting mixture is heated to dryness, calcined to

around 500 C, and it is made into pellets.

French Patent No. 2 534 904 describes a catalyst for the manufacture of unsaturated aldehydes, in particular acrolein and methacrolein, by vapor phase oxidation of propylene, isobutylene or tertiary butanol with a gas containing oxygen molecular. This catalyst is represented by the general formula: BiaWbFecModAeBfCgDhOx in which: - A represents nickel and / or cobalt; - B represents one or more elements chosen from alkali metals 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 obtained beforehand by calcination between 600 and 900 C of a mixture of a compound of bismuth and a compound of

tungsten.

The Applicant Company has now discovered that methacrolein can be produced 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 supplies 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: limitation of the overoxidation of the products formed which takes place in the presence of molecular oxygen; according to the present invention, due to the fact that the operation is carried out in the absence of molecular oxygen, the formation of COx (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 rate of reduction of the solid composition increases; the solid composition, once it has undergone a reduction and a gradual 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 regains its initial activity and can be used in a new reaction cycle; - The separation of the steps of reduction of the solid composition and of regeneration thereof makes it possible: - to increase the selectivity for methacrolein; and increasing the partial pressure of isobutene, such a partial pressure of supply of isobutene no longer being limited by the existence of an explosive zone by the isobutene + oxygen mixture. A subject of the present invention is therefore first of all the use of a solid composition of mixed oxides of formula (I): Mol2AaBibFecDdEeFfOx (I) 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 amount of oxygen bound 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) :

Oxidized SOLID + Isobutene - Reduced SOLID + Methacrolein (1).

The oxides of the different metals entering into 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 on calcination, namely metal salts of organic acids, metal salts of mineral acids, complex metal compounds, organic metal compounds, etc. The source of silicon generally consists of colloidal silica. The present invention relates to a process for the manufacture of methacrolein from isobutene, a process according to which gaseous isobutene is reacted with a solid composition of formula (I) as defined above, by operating at a temperature of 200 to 600 C, especially 250 to 450 C, under a pressure of 1.01 x 104 to 1.01 x 106 Pa (0.1 to 10 atmospheres), especially 5.05 x 104 to 5.05 x 105 Pa (0.5 to 5 atmospheres) and with a residence time of 0.01 seconds to 90 seconds, especially 0.1 seconds to 30 seconds, in the absence of molecular oxygen, thus carrying out the redox reaction ( 1) such

than indicated above.

According to particular embodiments of the present invention, it is possible to introduce gaseous isobutene mixed 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 gradual loss of its activity. This is why, once the solid composition has passed to the reduced state, the regeneration of said composition is carried out according to reaction (2): SOLIDreduced + 02 - Oxidized SOLID (2) by heating in the presence of an excess of oxygen or an oxygen-containing gas at a temperature of 250 to 5000C, for the time required for the reoxidation of the

solid composition.

After the regeneration, which can be carried out under temperature and pressure conditions identical to, or different from, those of the redox reaction, the solid composition regains an 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 periodically alternate; it is also possible to carry out the redox reaction (1) and the regeneration in the same reactor in

alternating periods of reaction and regeneration.

The preparation of methacrolein according to the invention is carried out according to a stoichiometric reaction

and not catalytic.

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 other elements and depends on their oxidation states. The conversions, selectivities and yields are defined as follows: Number of moles of isobutene having 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 reacted isobutene

EXAMPLE 1

(a) Preparation of a solid of formula Mo12Co6Fe3BilCr0 5SilK0 10x At room temperature, 262.7 g of Co (NO3) 2, 6H20, 182.3 g of Fe (N03) 3, 9H20 and 1.5 g of KNO3 in 420 ml of distilled water. Also at room temperature, 76.7 g of Bi (NO3) 3.5H20 are dissolved in 100 ml of distilled water acidified with 16.67 ml of HNO3 at 68% by volume. Still at room temperature, 30.1 g of Cr (NO3) 3, 9H20 are dissolved in 20 ml of distilled water. At 40 ° C., 318.7 g of (NH4) 6Mo7024, 4H20 are dissolved 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 as rain. The resulting mixture was heated at 80 C for 1.5 hours, then dried at 140 C for 12 hours. The solid obtained is calcined for 6 hours at 500 ° C. in air. The different metals are present in this solid in atomic ratios

as indicated in the title of this example.

(b) Preparation of methacrolein from isobutene by redox reaction In a tubular reactor at 340 ° C., mg of this solid is charged, then it is swept away with a continuous flow of 12 ml / min of helium. 1.9 × 10-6 moles of isobutene are injected into the solid, in order to carry out the redox reaction of the isobutene and of the solid. Isobutene is converted

at 99.8% with a methacrolein selectivity of 77.3%.

EXAMPLE 2

After having carried out the reaction of Example l (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

N injection Conversion of isobutene Selectivity to methacrolein

(%) (%)

I 79.4 75.3

2 53.8 77.4

3 40.3 77.9

4 32.2 78.6

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 flow of helium. Four new successive injections of 1.9 × 10-6 moles of isobutene are sent to the solid, in order to carry out the redox reaction of the isobutene and of the solid. The performances obtained are reported in the

Table 2.

Table 2 N injection Conversion of isobutene Selectivity to methacrolein

(%) (%)

1 96.5 79.5

2 76.3 76.1

3 50.5 80.5

4 38.4 81.1

EXAMPLE 4 (comparative) Preparation of methacrolein by the catalytic route 3 ml of the solid prepared according to Example 1 (a) are charged into a tubular reactor. A mixture consisting of isobutene / air / water / nitrogen = 6/63/15/16% by volume is injected into the solid at atmospheric pressure at a salt bath temperature of 340 C. The solid is here the catalyst of the reaction. The contact time, expressed by

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 of

76.4% methacrolein.

EXAMPLE 5

(a) Preparation of a solid of formula Mo12Co3.5Fe0.8BillW0.5Sil, 4K0.50x 60.9 g of Co (N03) 2, 6H20 are dissolved in 20 ml

of distilled water.

Also dissolved 20.2 g of Fe (NO3) 3, 9H20 in ml of distilled water, and 31.2 g of Bi (NO3) 3.5H20 in

30 ml of distilled water acidified with 6 ml of 68% HNO3.

Separately, 127.4 g of (NH4) 6Mo7024, 4H20 in 150 ml of water are dissolved by heating and stirring, then followed by

adds 7.4 g of WO3.

The aqueous solution containing the cobalt is introduced dropwise over 20 minutes into the aqueous solution of the ammonium salts. The ferric solution is then introduced over 10 minutes, then the solution containing the bismuth over 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 atomic ratios as indicated in the title

of this example.

(b) Preparation of methacrolein from isobutene by redox reaction In a tubular reactor at 370 ° C., mg of this solid is charged, then it is swept away with a continuous flow of 12 ml / min of helium. 1.9 × 10-6 moles of isobutene are injected into the solid, in order to conduct the redox reaction of the isobutene and of the solid. Isobutene is converted to 96.2% with a selectivity to methacrolein of

82.9%.

EXAMPLE 6

After having carried 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 Example 5. The performances are reported in Figure 5.

Table 3.

Table 3

N0 injection Conversion of isobutene Selectivity to methacrolein

(%) (%)

1 68.8 94.9

2 53.1 97.6

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 flow of helium. Three new successive injections of 1.9 × 10-6 moles of isobutene are sent to the solid, in order to carry out the redox reaction of the isobutene and of the solid. The performances obtained are reported in the

Table 4.

Table 4

N0 injection Conversion of isobutene Selectivity to methacrolein

(%) (%)

1 96.1 86.3

2 85.3 85.0

3 62.4 93.0

EXAMPLE 8 (comparative) Preparation of methacrolein by the catalytic route 3 ml of the solid prepared according to Example 5 (a) are charged into a tubular reactor. A mixture consisting of isobutene / air / water / nitrogen = 6/63/15/16% by volume is injected into the solid at atmospheric pressure at a salt bath temperature of 355 C. The solid is here the catalyst of the reaction. The contact time, expressed by

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 of

81.3% methacrolein.

Claims (9)

1 - Use of a solid composition of mixed oxides of formula (I): Mol2AaBibFecDdEeFfOx (I) in which: - A is at least one from 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 amount of oxygen bound 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) : SOLID Oxidized + Isobutene - SOLID Reduced + 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, by 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 the absence of molecular oxygen, thus carrying out the reaction redox (1) as indicated in claim 1. 3 - Process according to claim 2, characterized in that the gaseous isobutene is introduced as a mixture with an inert gas such as nitrogen and / or with water. 4 - Method according to one of claims 2 and 3, characterized by the fact that the redox reaction is carried out (1) at a temperature of 250 to 450 C. - Method according to one of claims 2 to 4, characterized in that the redox reaction (1) is carried out under a pressure of 5.05 x 104 to 5.05 x 105 Pa (0.5 to 5 atmospheres). 6 - Method according to one of claims 2 to 5, characterized by the fact that the redox reaction is carried out (1) with a residence time of 0.1 second to 30 seconds. 7 - Method according to one of claims 2 to 6, characterized in that once the solid composition has passed to the reduced state, the regeneration of said solid composition is carried out according to reaction (2): SOLIDreduced + 02 - Oxidized SOLID (2) by heating in the presence of a excess oxygen or an oxygen-containing gas at a temperature of 250 to 500 C, for the time required for the reoxidation of the solid composition. 8 - Process 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 periodically alternate of solid composition. 9 - Process according to claim 7, characterized in that one carries out the redox reaction (1) and the regeneration in the same reactor by alternating the periods reaction and regeneration.