Title of Invention

"AN IMPROVED PROCESS FOR THE CARBONYLATION OF METHANOL USING RHODIUM CARBONYL COMPLEXES OF NITROGEN DONORS LIGANDS"

Abstract The present invention relates to an improved process for the carbonylation of methanol using Rhodium carbonyl complexes of nitrogen donors ligands. The invention also relates to a process for the preparation of novel rhodium carbonyl complexes containing nitrogen based donors ligands and their catalytic activity. The rhodium metal complexes prepared by the process of present invention are useful as catalyst precursors for carbonylation of alcohol to carboxylic acid and/or ester. The ligands are selected from 2-aminobenzoic acid, 3-aminobenzoic acid, or 4-aminobenzoic acid. The carbonylation reaction can be carried out at a temperature below 140°C and pressure below 35 bar.
Full Text The present invention relates to a process for the preparation of novel rhodium carbonyl complexes containing nitrogen based donors ligands and their catalytic activity.
The present invention particularly relates to a process for the preparation of new and novel rhodium(I) carbonyl complexes containing nitrogen donor ligands. More particularly, the process of the present invention relates to preparation of new and novel rhodium(I) carbonyl complexes of ligands containing aromatic backbone. The rhodium metal complexes prepared by the process of present invention are useful as catalyst precursors for carbonylation of alcohol to carboxylic acid and/or ester.
Borowski et. al. {Trans. Met. Chem., 8. 1983. 266) reported the preparation of rhodium complexes with N-phenylanthranilic acid (PAAH) of the type H[Rh2(PAA)2Cl] and their catalytic activity towards hydrogenation reaction of a few aromatic and heteroaromatic compounds. Borowski et. al. (Trans. Met. Chem. 9, 1984. 109) also reported the synthesis and properties of some anthranilato- and N-phenylanthranilato-rhodium(I)-cycloocta-1.5-diene complexes. Nagy-Magos et. al (Trans. Met. Chem., 5. 1980, 186) reported the rhodium(I) complexes of the type (XY)Rh(CO)2 (where XYH = 2-aminobenzoic acid) but they did not report any catalytic work. Borowski et. al. (Polyhedron, 12. 1993. 1757) reported rhodium(I) complexes of the type [Rh(AA)(PPh3)3] and [Rh(PAA)(PPh3)2] (AAH = 2-aminobenzoic acid, PAAH = N-phenylanthranilic acid) and their catalytic activity for hydrogenation reactions of unsaturated compounds. Islam et. al. (./. Mol. Catal. A., 142, 1999, 169) showed some catalytic activities with these complexes for the reductive carbonylation of nitroaromatics
as well as in hvdrogenation but they did not indicate any catalytic activity of these complexes towards carbonylation of alcohols.
Denise et. al. have reported (J. Organomet. Chem, 63, 1973, 423) a few pyridine or substituted pyridine complexes of rhodium metal of the type [Rh(COD)ClL] (COD = 1.5-cyclooctadiene; L = pyridine. 2-vinyl pyridine. 2-methyl pyridine. 4-methyl pyridine), but they did not report any carbonyl complexes and also they did not disclose any catalytic application.
It may be mentioned that Lawson & Wilkinson have reported (J. Chem. Soc. A. 1965. 1900) preparation of few rhodium(I) carbonyl complexes of pyridine or chloro-pyridine but no mono substituted aldehyde/ester-pyridine containing complex was reported and also they did not disclose any catalytic application.
Sivasubramanian et. al. (Trans. Met. Chem.. 1982. 7, 346) have reported the first metal-nitrone complex (i.e.metal complexes of nitrogen-oxygen donors ligands) where metals are used from the 1 st row transition metal series. Other few reports of metal nitrone complex appeared in literature e.g. Frederick et. al. (Inorg. Chem. 37. 1998. 1446. J. Chem. Soc.. Da/ton Trans., 1998. 4055), Thirumalaikumar et. al. (Indian J. Chem, 38A, 1999. 720). but no rhodium complex has so far been reported.
Since the fust report of catalysis by [Rh(CO)2I2]- (F. E. Paulik and J. F. Roth. J. Chem. Soc. Chem. Comm., 1968. 1578). there has been little improvement on the intrinsic activity of the catalyst. Attempt to develop new catalysis species have been hampered by the relatively harsh condition under which the reaction is conducted commercially (150-200 °C, 25-45 atm.. in the presence of I") because under such conditions, virtually any
source of rhodium will be converted to [Rh(CO)2h] (D. Forster, J. Am. Chem. Soc 1976.98.846).
Reference may be made to U.S. Pat. No. 3.769.327 issued to F. E. Paulik et. al. wherein methanol is carbonylaled with carbon monoxide gas at 175°C and 1000 psig pressure to acetic acid using the catalyst [RhfCOhF] • The process is similar to existing industrial condition for conducting the reaction.
U.S. Pat. 4.990.654 issued to Wegman et.al. disclosed production of acetate ester from alcohol using rhodium complex catalysts. The process comprises catalytic reaction of a mixture of methanol and ethanol and carbon monoxide in contact with a homogeneous catalyst of rhodium complex containing the ligands like Ph2P(CH2)nP(O)Ph2 (Ph = phenyl, n = 1-4) or Ph2P(CH2)nC(O)R or Ph2P(CH2)nCOOR (R=alkyl/aryl). The reaction was carried out at a temperature up to 130°C and reaction pressure up to about 250 psig. The main drawback of the process is that methanol conversion is only 70 %.
Reference may be made to Wegman et.al. (J. Chem. Soc. Chem. Comm., 1987. 1891) wherein carbonylation in presence of catalyst [Rh(CO)2Cl(Ph2P(CH2)2P(O)Ph2)] was carried out at 80°C and 50 psig CO. The turnover frequency was 400 h-1.
U.S.Pat. 5.488.153 issued to Baker et.al. discloses a process for the liquid phase carbonylation of methanol in presence of CO. a halogen promoter ( e.g. CH3I), water, rhodium complexes of Ph2PCH2P(S)Ph2 or 2-(diphenylphosphino)thiophenol. The reaction was performed in the temperature range of 25 - 250°C and at pressure in the range 10 to 200 bar. The carbonylation rate was found to be considerably higher i.e.
about 6 times higher than that of the Monsanto's catalyst [Rh(CO)2I2] The main drawback of the process is that it involves higher temperature and pressure.
Cavell et. al (US Pat. 5352813) in their patent disclosed an improved process for the carbonylation of methanol to acetic acid and or its ester using a catalyst precursor composed of transition metal complex containing a hetero functional bidentate phosphorous-nitrogen donors ligand under CO pressure of 40 psi. and at 80 °C. However, the patent did not claim any yield of the catalytic reaction process.
Baker et.al. {J.Chem.Soc.Chem.Comm.. 1995. 197) also disclose that a catalyst cis-RhI(CO)Ph2PCH2P(S)Ph2 is about 8 times more active than the classic Monsanto catalyst [Rh(CO)2I2]- for carbonylation of methanol at 185°C and at 70 bar pressure.
In another disclosure. Dilworth et.al. (J. Chem. Soc: Chem. Comm., 1995. 1579) claimed that use of rhodium(I) complexes containing phosphinothiolate and thioether ligands resulted about 4 times higher rate in carbonylation of methanol to ethanoic acid than that of [Rh(CO)2I2] • The reaction was carried out at 185°C and at 70 bar pressure. The draw back of the process is that it involves high temperature and pressure.
Reference may be made to U.S.Pat No. 5,973.197 issued to Denis et.al.. wherein a method for preparing carboxylic acids by carbonylation of an alcohol in presence of rhodium complex catalyst. The carbonylation reaction was conducted at a temperature in the range 150 - 250°C and 1-100 bar pressures. Again the main drawback is the involvement of drastic reaction condition.
Since the discovery. Monsanto catalyst [Rh(CO)2I2] is still preferred as commercial catalyst for carbonylation of methanol to acetic acid. It is well known that a complex to act as an efficient catalyst, it should possess high electron density on the
metal center which can be achieved by introducing different types of electron donor ligands in the metal complex species. It is anticipated that a 'Hard* donors like nitrogen atom would increase the electron density on the central rhodium atom causing the complexes to behave as an efficient catalyst.
The main object of the present invention is to provide a process for the preparation of new and novel rhodium carbonyl complexes of ligands containing aromatic hetero and non-hetero backbone which are likely to obviate the drawback as detailed above.
Another object of the present invention is to provide a process for preparing rhodium(l) complexes containing electron rich ligand 'Hard' donors atoms facilitating high electron density on the rhodium center and higher stability, and thus causing facile oxidative addition reactions with different electrophiles and consequently can act as efficient catalyst precursors for carbonylation of alcohol to acid and/or ester.
Still another object of the present invention is to provide a process for carbonylation of methanol at comparatively lower temperature and pressure.
Accordingly, the present invention provides an improved process for carbonylation of methanol using novel electron rich rhodium metal complexes as catalyst, which comprises contacting carbon monoxide with liquid reaction composition comprising methanol, a halogen promoter preferably methyl iodide, water at a temperature in the range 135 ± 5°C and at a pressure of 35 ± 2 bar for a period of 30 - 120 min. in presence of novel rhodium complexes catalysts containing nitrogen donor ligands such as 2-aminobenzoic acid or 3-aminobenzoic acid or 4-aminobenzoic acid synthesized by reacting chlorobridged dimeric complex [Rh(CO)2Cl]2 in an organic solvent like CH2Cl2. CH3COOCH3 etc. with two molar equivalent (Rh : Ligand = 1:2 mo I ratios) of the
respective ligand under nitrogen atmosphere at room temperature for a period of about 10 - 30 minutes under stirring condition.
In an embodiment of the present invention the carbonylation reaction is exemplified by the reaction of methanol with carbon monoxide to form a mixture of acetic acid and methyl acetate.
The catalytic reaction was carried out in a 150 ml capacity teflon coated pressure reactor (Make Berghof, Model Heizug 75-150. Germany). The reactants such as methanol (4 ml), methyl iodide (1 ml), water (1 ml), ligand (0.050 mmol) and [Rh(CO)2Cl]2 (0.025 mmol) were taken in the reaction vessel. Optionally, the metal complex [Rh(CO)2ClL], L = 2-aminobenzoic acid, 3-aminobenzoic acid and 4-aminobenzoic acid as synthesized was added directly as catalyst precursors to the catalytic system. The reaction vessel was purged with CO gas for about 5 minutes and then pressurized with CO gas up to 20 bar at room temperature. The temperature of the reactor was raised to 135 + 5°C and the corresponding pressure was 35 ± 2 bar. The reaction was allowed for 30 to 120 minutes. After the catalytic reaction, the reaction products were collected and analyzed by Gas Chromatography.
In an embodiment of the present invention provides the preparation of novel rhodium(I) carbonyl complex of the type [Rh(CO)2CIL], where L are 2-aminobenzoic acid. 3-aminobenzoic acid and 4-aminobenzoic acid, by reacting [Rh(CO)2Cl]2 with two molar equivalents of the corresponding ligands which show equally intense terminal v(CO) band in the range 2010 - 2100 cm-1 attributable to the cis-disposition of the carbonyl groups. The v(NH2) bands in the complexes show an appreciable shift towards the lower wave number compared to that of the free ligands indicating coordination
occurs through N donor. 1H NMR data complexes. 1H NMR (300 MHz. CDC13) δ 6.28 -7.33 (m. 4H. Ph). 7.47 - 7.73 (s. 2H. NH2)], show a downfield shift compared to that of the free ligands. which is due to the partial shift of electron cloud from N-atom to the metal centre. This interaction also causes the phenylic protons a downfield shift.
The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention.
EXAMPLE - 1
To a solution of [Rh(CO)2Cl]2 (20 mg. 0.051 mmol) in CH2C12 (5 ml) 2-aminobenzoic acid (13.988 mg. 0.102 mmol) in acetone (3 ml) was added with constant stirring to yield [Rh(CO)2Cl(2-aminobenzoic acid)]. The solution was stirred at room temperature for 30 minutes. Light yellow coloured compound was separated out. The solvent was evaporated out under vacuum and the yellow mass obtained was washed with dry diethyl ether for several times. Yield : 95%; anal, calcd. for C9H7ClNO4Rh in %: C. 32.59; H. 2.11; N. 4.22; found: C, 32.42; H, 2.10: N. 4.25.
EXAMPLE -2
To a solution of [Rh(CO)2Cl]2 (20 mg. 0.051 mmol) in CH2C12 (5 ml) 3-aminobenzoic acid (13.988 mg, 0.102 mmol) in acetone (3 ml) was added with constant stirring to yield [Rh(CO)2Cl(3-aminobenzoic acid)]. The solution was stirred at room temperature for 20 minutes. Redish brown coloured compound was separated out. The solvent was evaporated out under vacuum and the yellow mass obtained was washed
with dry diethyl ether for several times. Yield : 93%; anal, calcd. for C9H7ClNO4Rh in %: C. 32.59; H. 2.11; N, 4.22; found: C. 32.45; H, 2.12: N. 4.20.
EXAMPLE -3
To a solution of [Rh(CO)2Cl]2 (20 mg. 0.051 mmol) in CH2Cl2 (5 ml) 4-aminobenzoic acid (13.988 mg. 0.102 mmol) in acetone (3 ml) was added with constant stirring to yield [Rh(CO)2Cl(4-aminobenzoic acid)]. The solution was stirred at room temperature for 20 minutes. Deep violet coloured compound was separated out. The solvent was evaporated out under vacuum and the yellow mass obtained was washed with dry diethyl ether for several times. Yield : 97%: anal, calcd. for C9H7ClNO4Rh in %: C. 32.59; H. 2.11; N. 4.22; found: C. 32.51; H. 2.10: N, 4.21.
EXAMPLE -4
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm-3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 + 5° C [pressure 35 ± 2 bar], and the reaction was continued for 30 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 38.11 % wt./wt.) of acetic acid (4.51 % wt./wt.) and methyl acetate (33.60 % wt./wt.) and the Turn Over Number (TON) was 588. Conversion = {[CO consumed (mol)]/[CO charged (mol)]} x 100. CO consumption was determined from analysis of products by GC. Yields of methyl acetate and acetic
acid were obtained from GC analyses. TON = [Amount of product (mol)]/[Amount of catalyst (Rh mol)].
EXAMPLE -5
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2CI(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 45 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 46.99 % wt./wt.) of acetic acid (9.3 % wt./wt.) and methyl acetate (37.64 % wt./wt.) and the Turn Over Number (TON) was 725.
EXAMPLE - 6
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 60 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 60.37 % wt./wt.) of acetic acid (16.46 %
wt./wt.) and methyl acetate (44.27 % wt./wt.) and the Turn Over Number (TON) was 937.
EXAMPLE - 7
0.099 mol of MeOH, 0.016 mol of Mel, 0.060 mol of H2O, 0.052 mmol of [Rh(CO)2Cl(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature, 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 75 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 75.05 % wt./wt.) of acetic acid (26.93 % wt./wt.) and methyl acetate (48.12 % wt./wt.) and the Turn Over Number (TON) was 1158.
EXAMPLE -8
0.099 mol of MeOH, 0.016 mol of Mel, 0.060 mol of H2O, 0.052 mmol of [Rh(CO)2Cl(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature, 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 90 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 87.42 % wt./wt.) of acetic acid (35.86 % wt./wt.) and methyl acetate (51.56 % wt./wt.) and the Turn Over Number (TON) was 1349.
EXAMPLE -9
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(2-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 95.62 % wt./wt.) of acetic acid (59.48 % wt./wt.) and methyl acetate (36.14 % wt./wt.) and the Turn Over Number (TON) was 1475.
EXAMPLE - 10
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.026 mmol of [Rh(CO)2CI]2 and 0.052 mmol of 2-aminobenzoic acid were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature, 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 94.69 % wt./wt.) of acetic acid (55.22 % wt./wt.) and methyl acetate (39.47 wt./wt.) and the Turn Over Number (TON) was 1460.
EXAMPLE -11
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(3-aminobenzoic acid)] catalyst precursors were charged into a previously
degassed 100 cnr reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 30 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 41.71 % wt./wt.) of acetic acid (2.22 % wt./wt.) and methyl acetate (39.49 % wt./wt.) and the Turn Over Number (TON) was 644.
EXAMPLE - 12
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O, 0.052 mmol of [Rh(CO)2Cl(3-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 45 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 55.87 % wt./wt.) of acetic acid (13.58 % wt./wt.) and methyl acetate (42.29 % wt./wt.) and the Turn Over Number (TON) was 862.
EXAMPLE - 13
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O, 0.052 mmol of [Rh(CO)2Cl(3-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the
reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 60 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 69.73 % wt./wt.) of acetic acid (27.14 % wt./wt.) and methyl acetate (42.59 % wt./wt.) and the Turn Over Number (TON) was 1075.
EXAMPLE - 14
0.099 mol of MeOH, 0.016 mol of MeL 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2CI(3-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cnr reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 75 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 84.51 % wt./wt.) of acetic acid (40.28 % wt./wt.) and methyl acetate (44.23 % wt./wt.) and the Turn Over Number (TON) was 1304.
EXAMPLE -15
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(3-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 90 min. After catalytic reaction, the products were collected and analvsed.
The product was a mixture (total conversion 95.91 % wt./wt.) of acetic acid (54.56 % wt./wt.) and methyl acetate (41.35 % wt./wt.) and the Turn Over Number (TON) was 1480.
EXAMPLE - 16
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(3-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 98.00 % wt./wt.) of acetic acid (57.83 % wt./wt.) and methyl acetate (40.17 % wt./wt.) and the Turn Over Number (TON) was 1512.
EXAMPLE-17
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.026 mmol of [Rh(CO)2Cl]2 and 0.052 mmol of 3-aminobenzoic acid were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 + 2 bar], and the reaction was continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 97.69 % wt./wt.) of acetic acid (55.02 % wt./wt.) and methyl acetate (42.67 wt./wt.) and the Turn Over Number (TON) was 1507.
EXAMPLE -18
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(4-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 30 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 38.29 % wt./wt.) of acetic acid (4.98 % wt./wt.) and methyl acetate (33.31 % wt./wt.) and the Turn Over Number (TON) was 590.
EXAMPLE - 19
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(4-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 45 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 47.18 % wt./wt.) of acetic acid (9.21 % wt./wt.) and methyl acetate (37.97 % wt./wt.) and the Turn Over Number (TON) was 728.
EXAMPLE - 20
0.099 mol of MeOH, 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(4-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm' reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 60 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 60.86 % wt./wt.) of acetic acid (18.54 % wt./wt.) and methyl acetate (42.32 % wt./wt.) and the Turn Over Number (TON) was 939.
EXAMPLE -21
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2Cl(4-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof. Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5 C [pressure 35 ± 2 bar], and the reaction was continued for 75 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 75.18 % wt./wt.) of acetic acid (25.81 % wt./wt.) and methyl acetate (49.37 % wt./wt.) and the Turn Over Number (TON) was 1160.
EXAMPLE -22
0.099 mol of MeOH. 0.016 mol of Mel, 0.060 mol of H2O. 0.052 mmol of [Rh(CO)2CI(4-aminobenzoic acid)] catalyst precursors were charged into a previously
degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 90 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 87.91 % wt./wt.) of acetic acid (39.60 % wt./wt.) and methyl acetate (48.31 % wt./wt.) and the Turn Over Number (TON) was 1356.
EXAMPLE -23
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.052 mmol of [Rh(CO):Cl(4-aminobenzoic acid)] catalyst precursors were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 96.33 % wt./wt.) of acetic acid (55.71 % wt./wt.) and methyl acetate (40.62 % wt./wt.) and the Turn Over Number (TON) was 1486.
EXAMPLE - 24
0.099 mol of MeOH. 0.016 mol of Mel. 0.060 mol of H2O. 0.026 mmol of [Rh(CO)2Cl]2 and 0.052 mmol of 4-aminobenzoic acid were charged into a previously degassed 100 cm3 reactor (Berghof, Germany) equipped with a magnetic stirrer and then pressurized with CO gas (20 bar at room temperature. 0.080 mol). The temperature of the reaction was increased to 130 ± 5° C [pressure 35 ± 2 bar], and the reaction was
continued for 120 min. After catalytic reaction, the products were collected and analysed. The product was a mixture (total conversion 95.69 % wt./wt.) of acetic acid (55.62 % wt./wt.) and methyl acetate (40.07 wt./wt.) and the Turn Over Number (TON) was 1476.
In summary, rhodium metal complexes [Rh(CO)2GL] where L = 2-aminobenzoic acid. 3-aminobenzoic acid. 4-aminoibenzoic acid were prepared by bridge splitting reaction of chlorobridged dimeric complexes [Rh(CO)2Cl]2 with the ligands L in 1 : 2 mol ratio at room temperature.
The main advantages of the present invention are : (i) The metal center in the complexes will be electron rich and therefore exhibit high nucleophilicity.
(ii) The complexes in general are stable in air as well as in solution, (iii) The complexes are coordinatively unsaturated and can easily undergo oxidative addition reaction with different electrophiles like alkyl halide, which is the key step in carbonylation of alcohol.
(iv) The carbonylation reaction can be carried out at a temperature below 140°C and pressure below 35 bar.










We claim:
1. An improved process for the carbonylation of methanol using Rhodium carbonyl complexes of nitrogen donors ligands, which comprises: contacting carbon monoxide with liquid reaction composition comprising methanol, a halogen promoter preferably methyl iodide, water at a temperature in the range 135 + 5°C and at a pressure of 35 ± 2 bar for a period of 30 - 120 minutes in presence of rhodium carbonyl complexes catalysts prepared by the process as herein described and containing nitrogen donor ligands selected from 2-aminobenzoic acid, 3-aminobenzoic acid or 4-aminobenzoic acid, separating the product mixture acetic acid and methyl acetate by known methods.
2. An improved process as claimed in claim 1, wherein rhodium carbonyl complexes catalysts is prepared by reacting chlorobridged dimeric complex [Rh(CO)2Cl]2 in an organic solvent CH2Cl2 or CH3COOCH3 with ligands selected from 2-aminobenzoic acid, 3-aminobenzoic acid or 4-aminobenzoic acid, in a molar ratio of Rh: ligand = 1:2 under nitrogen atmosphere at room temperature for a period of 10-30 minutes under stirring condition, separating the catalyst by known methods.
3. An improved process as claimed in claim 1, wherein the rhodium carbonyl complexes are of the type [Rh(CO)2ClL)] where L = 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid.
4. An improved process for the carbonylation of methanol using Rhodium carbonyl complexes of nitrogen donors ligands substantially as herein described with references to the examples.

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2306-DEL-2004-Abstract-(16-03-2011).pdf

2306-del-2004-abstract.pdf

2306-del-2004-Claims-(06-06-2011).pdf

2306-DEL-2004-Claims-(16-03-2011).pdf

2306-DEL-2004-Claims-(18-05-2011).pdf

2306-del-2004-claims.pdf

2306-del-2004-Correspondence Others-(06-06-2011).pdf

2306-DEL-2004-Correspondence Others-(16-03-2011).pdf

2306-DEL-2004-Correspondence-Others-(18-05-2011).pdf

2306-del-2004-correspondence-others.pdf

2306-DEL-2004-Description (Complete)-(16-03-2011).pdf

2306-del-2004-description (complete).pdf

2306-del-2004-form-1.pdf

2306-del-2004-form-18.pdf

2306-DEL-2004-Form-2-(16-03-2011).pdf

2306-del-2004-form-2.pdf

2306-DEL-2004-Form-3-(16-03-2011).pdf

2306-del-2004-form-3.pdf

2306-del-2004-form-5.pdf


Patent Number 248428
Indian Patent Application Number 2306/DEL/2004
PG Journal Number 28/2011
Publication Date 15-Jul-2011
Grant Date 14-Jul-2011
Date of Filing 19-Nov-2004
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 DIPAK KUMAR DUTTA REGIONAL RESEARCH LABORATORY, JORHAT-785006, ASSAM, INDIA.
2 MANAB SHARMA REGIONAL RESEARCH LABORATORY, JORHAT-785006, ASSAM, INDIA.
3 PRATAP CHUTIA REGIONAL RESEARCH LABORATORY, JORHAT-785006, ASSAM, INDIA.
4 NANDINI KUMARI REGIONAL RESEARCH LABORATORY, JORHAT-785006, ASSAM, INDIA.
5 MADAN GOPAL PATHAK REGIONAL RESEARCH LABORATORY, JORHAT-785006, ASSAM, INDIA.
PCT International Classification Number C07C
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA