Process for the production of nitriles using a catalyst based on antimony and iron

Abstract

A compound of the formula Sb.sub.xFe.sub.1O.sub.y (I) in which x varies from 0.4 to 1 inclusive and y varies from 1.6 to 4 inclusive, may be used as a catalyst for catalyzing the ammoxidation reaction of an alcohol of following formula (II) CH.sub.2C(R.sup.1)CH.sub.2OH (II) in which R.sup.1 represents a hydrogen atom or a methyl radical, to give nitrile of following formula (III) CH.sub.2C(R.sup.1)CN (III) in which R.sup.1 has the same meaning as in above formula (II), the said reaction being carried out in the gas phase, the said gas phase comprising at least oxygen and ammonia. The present invention also relates to the process for the ammoxidation of an alcohol of formula (II) employing a compound of formula (I) as catalyst.

Claims

1. A process for the production of a nitrile from an alcohol in the presence of a catalyst, said method comprising: a stage of ammoxidation of an alcohol of following formula (II):
CH.sub.2C(R.sup.1)CH.sub.2OH(II) in which R.sup.1 is a hydrogen atom or a methyl radical, to result in a nitrile of following formula (III):
CH.sub.2C(R.sup.1)CN(III) in which R.sup.1 has the same meaning as in the above formula (II), said reaction being carried out in gas phase, said gas phase comprising at least ammonia and oxygen, and in the presence of a solid catalyst selected from the group consisting of compounds of following formula (I):
Sb.sub.xFe.sub.1O.sub.y(I) in which x varies from 0.4 to 1 inclusive and y varies from 1.6 to 4 inclusive.

2. The process according to claim 1, wherein R.sup.1 is a hydrogen atom and acrylonitrile is produced.

3. The process according to claim 1, wherein x varies from 0.5 to 0.8 inclusive.

4. The process according to claim 1, wherein x=0.6.

5. The process according to claim 1, wherein the ammoxidation reaction is carried out at a temperature varying from 350 to 450 C.

6. The process according to claim 1, wherein the ratio of the volume of catalyst to the total flow rate by volume of gas injected into the reactor, calculated at the temperature and at the pressure of the reaction, varies from 0.05 to 2 s.

7. The process according to claim 1, wherein, within the gas phase, the alcohol of formula (II)/ammonia molar ratio varies from 1/1 to 1/4.

8. The process according to claim 1, wherein, within the gas phase, the alcohol of formula (II)/oxygen molar ratio varies from 1/1.5 to 1/5.

9. The process according to claim 1, wherein the ammoxidation reaction is carried out using a gas phase in which the alcohol of formula (II)/oxygen/ammonia molar ratio is 1/3.5/3.

10. The process according to claim 1, wherein the catalyst of formula (I) is supported by a porous solid support.

Description

DETAILED DESCRIPTION

(1) The present invention is illustrated by the following implementational examples, to which, however, it is not limited.

EXAMPLES

(2) In the examples which follow, the following starting materials were used: 97% Oxalic acid (Fluka), Iron nitrate nonahydrate (Sigma Aldrich), Antimony(III) oxide (Sigma Aldrich), 99% Allyl alcohol (Fluka), Ammonia (Praxair), Oxygen (Alphagaz).

(3) Catalysts of formula (I) with x=0.4 to 1 were prepared from these starting materials. The value of y for each of these catalysts is determined in accordance with the electrical neutrality and/or the valences of the elements. It was not measured experimentally.

(4) The synthesis of the acrylonitrile was carried out in the gas phase in a tubular fixed bed reactor with a diameter of 15 mm and a length of 120 mm. The temperature of the reactor was precisely regulated and controlled by a thermocouple.

Example 1

Synthesis of a Catalyst of Formula (I) with x=0.6

(5) A 0.05M solution was prepared by dissolving 2.21 g of oxalic acid in 500 ml of water at 80 C. with stirring. Once dissolution was complete, 140.97 g of iron nitrate nonahydrate were added to the oxalic acid solution while maintaining the temperature at 80 C. After complete dissolution of the iron nitrate nonahydrate, 30.51 g of antimony(III) oxide were added. The resulting solution was left to evaporate while maintaining the temperature at 80 C., with stirring, until a viscous solution was obtained, which was then dried in an oven at 120 C. for 72 hours.

(6) After drying, the product obtained was pressed in the form of pellets which were subsequently ground in order to obtain a pulverulent product comprising particles having a size of between 250 and 630 m. These particles were then calcined under static air from ambient temperature up to 500 C. while observing a temperature rise gradient of 1 C./min and then a phase of maintenance at 500 C. for 8 hours. The catalyst was subsequently left in the oven until the temperature had returned to 50 C. A catalyst exhibiting an Sb/Fe ratio of 0.6 (i.e., x=0.6) was obtained.

Example 2

Synthesis of a Catalyst of Formula (I) with x=0.8

(7) A catalyst of formula (I) in which x=0.8 was prepared according to a procedure identical to that of Example 1 above but using 2.21 g of oxalic acid, 27.7 g of iron nitrate nonahydrate and 8 g of antimony(III) oxide.

Example 3

Synthesis of a Catalyst of formula (I) with x=0.4

(8) A catalyst of formula (I) in which x=0.4 was prepared according to a procedure identical to that of Example 1 above but using 2.21 g of oxalic acid, 87.3 g of iron nitrate nonahydrate and 12.6 g of antimony(III) oxide.

Example 4

Synthesis of a Catalyst of Formula (I) with x=1.0

(9) A catalyst of formula (I) in which x=1.0 was prepared according to a procedure identical to that of Example 1 above but using 2.21 g of oxalic acid, 22.2 g of iron nitrate nonahydrate and 8.0 g of antimony(III) oxide.

Example 5

Synthesis of Acrylonitrile from Allyl Alcohol

(10) 5 g of the catalyst prepared according to Example 1 were placed in a fixed bed reactor. The reaction was carried out with a 7.2% by weight aqueous allyl alcohol solution. The reactor was heated to 400 C. and then fed with reactants (allyl alcohol/O.sub.2/NH.sub.3) at atmospheric pressure. The contact time of the reactants with the catalyst was of the order of 0.1 s and the reaction time was 5 hours.

(11) The products resulting from the reaction were analysed after trapping at the reactor outlet in a bubbler maintained at low temperature (4 C.). The liquid obtained was subsequently analysed on a gas chromatograph equipped with a flame ionization detector.

(12) The operating conditions used are summarized in Table I below:

(13) TABLE-US-00001 TABLE I Control (*) Test 1 Test 2 Test 3 Test 4 Allyl 1/1.6/ 1/1.6/0.4 1/3.5/0.8 1/3.5/1.5 1/3.5/3 alcohol/O.sub.2/NH.sub.3 0.4 molar ratio Conversion of the 14% 87% 95% 99% 99% allyl alcohol % Acrylonitrile 0 17 38 52 63 % Acrolein 24 52 43 26 3 % Acetaldehyde 16 5 4 1 1 % 21 5 4 0 <1 Propionaldehyde % Acetonitrile 0 1 2 2 1 (*): Catalyst-free process: not in accordance with the invention

(14) These results demonstrate, first of all, that the presence of a catalyst in accordance with the present invention is necessary in order to carry out the ammoxidation reaction of allyl alcohol to give acrylonitrile in the presence of ammonia and oxygen. Furthermore, they show that the presence of a catalyst in accordance with the present invention increases, with identical operating conditions, the conversion of the allyl alcohol (from 14% to 87%) and also increases the selectivity for acrylonitrile and for acrolein, from 0% and 24% to 17% and 52% respectively. In addition, according to a preferred embodiment of the process in accordance with the invention, it is seen that the increase in the NH.sub.3/allyl alcohol molar ratio makes it possible to further improve the selectivity for acrylonitrile and also the conversion of the allyl alcohol. Under the optimum implementational conditions of this example, the conversion of the allyl alcohol is 99% with a selectivity for acrylonitrile of 63%.

Example 6

Synthesis of Acrylonitrile from Allyl Alcohol

(15) In this example, the ammoxidation reaction of allyl alcohol was carried out according to the process described in detail in Example 5 above under operating conditions which make possible the complete conversion of the allyl alcohol, using the catalyst prepared according to Example 1, at a temperature of 400 or 450 C., and using different allyl alcohol/NH.sub.3 molar ratios.

(16) The reaction time was 5 hours.

(17) As for Example 5, the products resulting from the reaction were analysed after trapping at the reactor outlet in a bubbler maintained at low temperature (4 C.). The liquid obtained is subsequently analysed on a gas chromatograph equipped with a flame ionization detector.

(18) The operating conditions used are summarized in Tables II and III below:

(19) TABLE-US-00002 TABLE II Test 5 Test 6 Test 7 Reaction temperature 400 C. 450 C. 450 C. Contact time (s) 0.1 0.1 0.16 Allyl alcohol/O.sub.2/NH.sub.3 molar 1/3.5/2 1/3.5/1 1/3.5/2 ratio Conversion of the allyl 100% 100% 100% alcohol % Acrylonitrile 67 51 76 % Acrolein 11 24 9 % Acetaldehyde 1 1 1 % Propionaldehyde 1 1 1 % Acetonitrile 4 2 3 Carbon balance 97% 101% 101%

(20) TABLE-US-00003 TABLE III Test 8 Test 9 Test 10 Reaction temperature 450 C. 400 C. 400 C. Contact time (s) 0.1 0.16 0.16 Allyl alcohol/O.sub.2/NH.sub.3 molar 1/3.5/3 1/3.5/1 1/3.5/3 ratio Conversion of the allyl 100% 100% 100% alcohol % Acrylonitrile 83 50 76 % Acrolein 4 27 1 % Acetaldehyde <1 2 1 % Propionaldehyde 1 1 1 % Acetonitrile 3 3 5 Carbon balance 92% 93% 85%

(21) These tests show that the best results in terms of selectivity with regard to the formation of acrylonitrile are obtained with Test 8 carried out at 450 C. with a contact time of 0.1 s and an ally alcohol/NH.sub.3 molar ratio of 1/3. An acrylonitrile yield of 83% with complete conversion of allyl alcohol is then obtained.