|Title of Invention||
A RPOCESS FOR THE SIMULTANEOUS PRODUCTION OF STYRENE OXIDE AND BENZALDEHYDE"
|Abstract||An improved process for the simultaneous production of styrene oxide and benzaldehyde by contacting styrene with air in the presence of solid organomanganese complex catalyst in an aliphatic organic solvent and a promoter containing hydroperoxide group at a temperature in the range of 40 to 100°C for a period in the range of 10 to 12 hours, isolating the styrene oxide and benzaldehyde from the reaction mixture by known methods.|
|Full Text||This invention relates to a improved process for the simultaneous production of styrene oxide and benzaldehyde.
Epoxides are versatile and important intermediates in the organic chemical industry because they easily undergo stereospecific ring opening to form bifunctional compounds. Epoxides of styrene are well known and are of considerable commercial importance. Benzaldehyde is used in the manufacture of perfumery chemicals.
In the prior art, epoxidation of styrene was carried out mostly in homogeneous systems using stoichiometric quantities of an active singlet oxygen source such as hydrogen peroxide, other peroxides, alkyl hydroperoxides, hypochlorites or iodosobenzene. Epoxidation of styrene by H2O2 and alkyl hydroperoxides as catalysed by several metal complexes such as rhenium trioxide, molybdenum, ruthenium Schiff base and rare earth metal complexes have been reported. The use of chiral Mn(III) salen as catalyst with imidazole as donor ligand in the epoxidation of styrene is known in the prior art ( P. Pietikainen reported in the Journal Tetrahedron Letters vol 36, No. 2, page 319,1995) that using sodium and tetra-n-butyl ammonium periodates, as the source of oxygen where 51 - 69 % styrene oxide was recovered. J. Skarizewski et al reported in the Journal, J. Mol. Cat., A, vol 105, L63(1995) the two phase epoxidation of styrene with sodium
nypochlorite but not molecular oxygen catalysed by the Jacobsen type Mn(III)salen complexes in the presence of various additional ligands. One significant draw back of this process was the formation of phenyl acetaldehyde and acetophenone in 5 : 1 ratio as by-products. R. A. Sheldon et al reported in the Journal J. Mol. Cat. A, vol. 102,page 23 (1995) the catalytic epoxidation of styrene by bis ruthenium bipyridyl complex using sodium hypochlorate as oxidant. They achieved overall 60 % conversion with 22 and 78 % selectivity to epoxides and benzaldehyde respectively. The major draw back of such complex as catalyst in the prior art is the separation of the catalyst from the reaction mixture. The ^Jerman patent (east) No. DD. 242,227,1987 \iescribes a process for the preparation of styrene oxide and benzaldehyde by oxidation of styrene is characterized in that styrene is oxidized in the presence of an oxidation initiator and a polymerization inhibitor at 120-130°C with or without solvent. Recently, another process for the preparation of styrene oxide and benzaldehyde is reported by the oxidation of styrene at 8QL-14Q C in the presence of trialkyl or triaryl orthophosphate catalyst. The catalytic activity of the Al- MCM-41 immobilized complex for oxidation of styrene with iodozylbenzene, hydrogen peroxide and tertiary butyl hydro peroxide as oxidant has been reported by S. Kim et al in the Journal Catalysis Letters, vol. 43, page 149(1997). In another report Rajive et al reported in the Journal J.Cat. vol. 156, page 163(1995) the catalytic oxidation of styrene using H2®2 as an oxidant where poor selectivity for
benzaldehyde was observed over a solid titanium silicate molecular sieve, TS-1.
In addition, the high cost of the hydroperoxides or iodosobenzene and low concentration of hypochlorites are also to be taken into account.
To overcome these limitations of the prior art and to make the production of benzaldehyde and styrene oxide more economical, it was found necessary to develop an improved process for the oxidation of styrene
(1) which makes use of less expensive, non-hazardous
homogeneous and/or heterogeneous catalyst and eliminate the
disadvantages of each
(2) which is a single step process
(3) which needs simple experimental set up
The main object object of the present invention is to provide an improved process for the simultaneous production of styrene oxide and benzaldehyde in high selectivity by the oxidation of styrene in presence of a catalyst and air as an oxidant.
Another object is to provide a process using less expensive and non-hazardous oxygen source.
Yet another object is to provide a process which operates at a relatively low temperature.
Accordingly, the present invention provide an improved process for the simultaneous production of styrene oxide and benzaldehyde which comprises contacting styrene with air in the presence of solid organomanganese complex catalyst such as herein described in an aliphatic organic solvent and a promoter containing hydroperoxide group at a temperature in the range of 40 to 100°C for a period in the range of 10 to 12 hours, isolating the styrene oxide and benzaldehyde from the reaction mixture by known methods.
In one of the embodiments of the present invention, the organic solvent used may be acetonitrile, acetone and methanol.
In another embodiment the promoter may be tertiary butyl hydroperoxide and cumene hydroperoxide.
Yet another embodiment the rate of air is in the range of 3 to 5 L/hr.
In another embodiment the catalyst used in the process may be such as the catalysts having the general formula 1 in the drawing accompanying this specification wherein the R1, R2, R3 have the values described in Table 1.
1. RI»R! = R2 = H, R3 = H
2. RI,RI = -(CH2)4-, R2 = H, R3 = H
3. RI.R! = H, R2 = H, R3 = Br
4. RI.RI = H, R2 = H, R3 = Cl
5. RI.R! = H, R2 = H, R3 = N02
6. RI.R! = -
8. RX.RI = -(CH2)4-, R2 = H, R3 = N02
9. RI»R! = H, R2 = Br, R3 = Br
10. RI.RI = H, R2 = Cl, R3 = Cl
11. Ri.Rl = H, R2 = NC^, R3 = N02
12. Rl»R2 = ~(CH2)4-, R2 = Br, R3 = Br
13. Ri,R2 = -
The same compounds have been characterized by UV and IR spectra as described in Table 2.
Table 2 Important FTIR and UV-VIS spectral data of the catalyst before (1-14) and after (15-28) encapsulation.
In a feature of the present invention, air is passed through the pot reactor to react with styrene at various temperatures and reaction time in the presence of an organomanganese complex of the general formula shown in Fig 1.
In another feature of the present invention the extent of carbon-carbon bond cleavage depends on the experimental conditions^ The amount of cleavage and hence the formation of benzaldehyde increased with acidity of the catalyst. In the process of the present invention, it is essential to use catalysts of the general formula given in Fig 1. Catalysts 1-14 are obtained with substituents indicated in Table 1. Catalysts-15-28 are obtained by encapsulation of catalysts 1-14 i zeolite X.
One feature of the process of the present invention is the use of non-hazardous organomanganese complex catalyst.
Another feature of the process is that the organomanganese complex catalyst is encapsulated in a zeolite, prepared by known conventional methods
An advantageous feature of the present process is that the active transition metal site differs from the solution species only by the constraints placed on it by the zeolite, allowing the reactions to occur under mild conditions. In addition, as the catalyst is encapsulated inside the zeolite, the products can be readily separated.
Another advantageous feature of the present process is that the life time of the catalyst are increased by its encapsulation since degradation pathways involving reactions such as dimerization of catalysts are prevented.
Another advantage of the process of the present invention is that the reactions are carried out at relatively low temperatures (between 40-100 C) under atmospheric pressure and other simple operational conditions.
One more feature of the process of the present invention is the use of easily available air as the oxidizing agent rather than expensive oxidants like hydrogen peroxide or alkyl peroxides.
The present invention will now be illustrated with a few examples. However, it should be understood that the present invention is by no means restricted by these specific examples.
Here, the preparation of catalysts (1-14) are reported. In a typical preparation, appropriate salicylaldehyde derivatives as in Table 1 (2 equivalent) are added to a 0.2 M solution of diamino derivatives(ethylene diamine or phenelen diamine) in absolute ethanol. The mixture is heated to reflux point for one hour and then cooled to obtain a bright yellow solution, which on further cooling gave yellow crystalline solid, purified by washing with small portions of alcohol. The respective salen obtained in the above manner were redissolved in hot absolute ethanol to give a 0.1 M solution. Solid hydrated manganese(II) acetate (2 equivalent) was then added in one portion and the solution refluxed for one hour. Approximately 3 equivalent of solid lithium chloride was then added and the mixture refluxed for an additional 30 minutes. Cooling the mixture to 0°C afforded the respective manganese salen complexes as dark brown crystals which were washed thoroughly with water and isolated by filtration in about 70% yield. An additional crop of material can be obtained by dropwise addition of water to the mother liquor. Elemental analyses, FTIR, solid UV-VIS and EPR data correspond to their proposed structure.
This example illustrates the procedure for the encapsulation of the above prepared catalysts in the super cage of zeolite X. Fumed silica (Sigma, 99.84%; 4g.), sodium hydroxide (3.2 g.), salen manganese(III) complex (0.05 g.) and distilled water (16 ml) were combined and stirred for 30 minutes. After 30 minutes, to the above homogeneous solution was added sodium aluminate solution (prepared from 9 'g. of aluminium isopropoxide, 3.2 g. of sodium hydroxide and 40 ml water) which resulted in a slurry. This mixture was taken in a polypropylene bottle and stirred for 24 hours at room temperature, then crystallized at 90° C for 24 hours. The mixture was allowed to cool to room temperature and diluted with large amounts of deionized water. The solid crystals were isolated by centrifugation at 8000 rpm for 24 hours.The resultant solid is dried at 90° for 24 hours in air and then soxhlet extracted with acetonitrile for 72 hours. It was then finally dried at 363 K under vacuum for 15 hours. Satisfactory X-ray diffraction pattern, FTIR, solid UV-VIS, ESCA and EPR results were obtained for this product.
The epoxidation reaction was conducted in an autoclave as follows. In a typical example, 0.5 g. of a catalyst given in Table 1, 15 g. of acetonitrile, 15 g. of styrene and 0.3 g. of tertiary butyl hydroperoxide are mixed in a Parr autoclave of capacity 300 ml. The autoclave was then pressurized with air to 500 psi and kept stirring at 70-100°C for 10 hours. The autoclave
was then cooled to room temperature and the product was analyzed by a gas chromatograph. The autoclave reaction was found to give 50-92% conversion but poor selectivity for styrene oxide.
The procedure for the oxidation of styrene by the catalysts at atmospheric pressure is described. In a standard experiment, 0.1 g. of the catalysts 1-14 , 5 g. of acetonitrile, 5 g. of styrene and 0.1 g. of tertiarybutyl hydroperoxide are placed in a glass reactor equipped with a reflux condenser and a gas inlet. Air was bubbled through the reactor and the temperature of the reaction system maintained at 70°C for 10 hours. The reaction mixture was cooled to room temperature and products analyzed by gas chromatography. The results are recorded in Table 3.
Table 3 Oxidation products of styrene with air over catalysts 1-14 after 10 hours at 70 C.
Encapsulated zeolite catalysts (0.1 g.) was reacted with styrene as in example (4) for 12 hours at 70 C. The reaction product obtained was analyzed by gas chromatography. Results are tabulated in Table 4.
Table 4 Oxidation products of styrene with air over zeolite encapsulated catalysts (15-28) after 12 hours at 70°C.
This example illustrates the effect of temperature on the
oxidation of styrene. The reaction procedure adopted was the
same as that described in examples (4) and (5) except that the
temperature of the reaction was varied to 60, 70 and 80°C. The
corresponding reaction products were analyzed by gas
chromatography. The results obtained by the treatment of catalysts 1 and 15 are shown in Table 5.
Table 5 Effect of temperature on the oxidation of styrene after 9 hours.
We claim :
1. An improved process for the simultaneous production of styrene oxide
and benzaldehyde which comprises contacting styrene with air in the
presence of solid organomanganese complex catalyst such as herein
described in an aliphatic organic solvent and a promoter containing
hydroperoxide group at a temperature in the range of 40 to 100°C for
a period in the range of 10 to 12 hours, isolating the styrene oxide and
benzaldehyde from the reaction mixture by known methods.
2. An improved process as claimed in claim 1 wherein the
organomanganese complex is a substituted salen complex of
3. An improved process as claimed in claims 1-2 wherein the organic
solvent used is acetonitrile, acetone and methanol.
4. An improved process as claimed in claims 1-3 wherein the promoter
used is tertiary butyl hydroperoxide, cumene hydroperoxide.
5. An improved process for the simultaneous production of styrene oxide
and benzaldehyde substantially as herein described with reference to
|Indian Patent Application Number||2789/DEL/1997|
|PG Journal Number||10/2008|
|Date of Filing||30-Sep-1997|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI 110001. INDIA|
|PCT International Classification Number||C07D 301/12|
|PCT International Application Number||N/A|
|PCT International Filing date|