Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF CARBOXYLIC ACIDS

Abstract

This invention relates to an improved process for the preparation of carboxylic acids. The invention relates to a process for the conversion of aliphatic and aromatic substituted aldehydes to their corresponding acids, catalyzed by vanadium silicalite (VS-1) in combination with air as an oxidant and tertiary butylhydroperoxide (TBHP) or ethylbenzenehydroperoxide (EBHP) or cumenehydroperoxide (CHP) as an initiator. The process steps are: reacting 0.010 to 0.014 mol of an aldehyde, in presence of a polar solvent, an initiator having strength 50-100%, an oxidant and a heterogenous catalyst, at a temperature in the range of 80-120°C, pressure ranging from 400 to 500 psi for a period of 2 to 10 hrs, cooling the reaction mixture to room temperature, separating corboxylic acids from the said mixture by convectional methods, the said process

Full Text

This invention relates to an improved process for the preparation of carboxylic acids, catalysed by heterogeneous catalyst. More particularly, the invention relates to a process for the conversion of aliphatic and aromatic substituted aldehydes to their corresponding acids, catalysed by vanadium silicalite (VS-1) in combination with air as an oxidant and tertiary butylhydroperoxide (TBHP) or ethylbenzenehydroperoxide (EBHP) or cumenehydroperoxide (CHP) as an initiator. Carboxylic acids have wide variety of applications; they are used as intermediates for textile chemicals, dyes, drugs, plastics, and photographic chemicals. Esters are used as perfumes or perfume precursors, as liquid binders, and moisturising compositions cosmetics. Amides and other derivatives serve as corrosion inhibitor, detergent, floatation aids, an oil additives, some derivatives are used in the preparation of Pharmaceuticals also as radical inhibitors for the polymerisation of vinyl chloride or of ethylene. One of the largest uses in the preparation of agricultural chemicals, used in the preparation of a number of commercial herbicides. Cu, Zn salts are used as fungicides and insecticides, Co, Pb, Mn, Fe, salts are employed as drying agents for paints and printing inks. In the prior article, conversion of aldehydes to acids is achieved by various methods and following are the few methods: 1. Oxidation reactions in which the conversion of aldehydes to acids have been achieved by using reagents like KMn04, Jones reagent, CrO3, Ag2O, Chromyl acetate, NBS. [Ref: JACS.109, 7122 (1987) and ref. cited therein], Cr complex [Ref: Synth.commun.10, 951(1980)], HNO3 [Ref: Org Synth Coll. Vol -I page 166.], t-BuOH, KMnO4, [Ref: Tet Lett.27, 4537, (1986)], TBHP Mo. Catalyst, H2O2, NaC102, AgO, RuCl2, NaMnO4, [Ref: Tet.Lett 25, 4417(1984)], DDQ, Cu (MnO4).8H20, NaOH, active Ag metal and by using various catalyst like, Ru04, RuCl2, RuH2, Ru02, Ni02, etc [Ref:JOC, 52, 622, (1987)] and JOC, 52,4319(1987). 2. Kolbe's method where C02 is used for the conversion of aldehydes to acids (Ref: J. Chinese. Chem.Soc. 13, 77-83, (1946) and other references where they have used CO2 in hydrogen atmosphere with catalyst and at higher temperature to get carboxylic acids from K-phenolates whereby hydroxyaromatic acids are manufactured [Ref: Japan patent 72, 44, 215, (1969), Japan patent 7424470, (1974), Japan patent, 7210, 380, (1967), Ger.offen, 2033, 448, (1970), Ger. offen, 2049104 (1971), Fr. 1564, 997(1969). 3. Phenol and K-phenolates were converted to aromatic acids and K-salicylates were converted to hydroxy aromatic acids by using CO and C02 in N2 atmosphere and higher temperature and pressure [Ref: Japan patent 7234693, (1972), Fr. Addn. 2098, 768 (1970), Japan patent 6929251, (1969), JCS, 3092-6, (1964), Brit 816, 248 (1959) Kagakuto Kogyo Osaka 335317-18(1959), Rev. Soc, Quisnn Mex, 8, 13-18, (1964). 4.. Hydroxy toluene was converted to hydroxy aromatic acid by using CuO, at higher temp [Ref: US 3360553, (1967)]. 5. Hydroxy aromatic acids were obtained from Chlorobenzene by using CO, and higher temperature [Ref: Ger 575955, (1933)]. 6. Aromatic aldehydes were converted to their acids by using strong alkali and active Ag metal [Ref: JOC, 1947, 12, 85]. 7. Furfuraldehyde was converted to furfuroic acid by using copper oxide - silver oxide as a mixed catalyst along with oxygen as the oxidant in alkaline medium [Ref: Org. Synth.(1963) Coll Vol 4,493 ] The above mentioned processes in the prior art are known to be useful for the conversion of aldehydes to its carboxylic acids, however they suffer from the following drawbacks: 1. In the Kolbe-Schimdt method CO2, H2 is used and higher temperature is employed which are hazardous. 2. In the other method CO and higher temperature are employed which is hazardous to the environment. 3. Most of the methods in the prior art are not catalytic method; they involve the use of stoichiometric amounts of the expensive reagents. 4. In most of the stoichiometric reactions in the prior article, large amounts of waste products containing heavy metals (Cr, Mn, etc.) residues are generated in the processes, which are difficult to dispose off. 5. In many reactions halogenated oxidants, highly alkaline conditions and high temperature are used which are hazardous to the environment. 6. In most of the reactions highly expensive catalysts are used. 7. In one of the method HN03, HCN are also used which are highly toxic. In view of all the above disadvantages of the prior art, it is desirable to provide a process that is safe, eco-friendly, inexpensive, single step and simple. The main object of the present invention is to provide an improved process of preparation of carboxylic acids which obviates the drawbacks as detailed above. Another object of the present invention to provide a single step process for the preparation of carboxylic acids by conversion of substituted aromatic aldehyde using TBHP as initiator (70%), air as an oxidant and heterogeneous catalyst VS-I (10%) which can easily be separated from the product and reused. The catalyst used in the present invention is prepared as per process given in our pending Indian patent application 765/Del/91. Accordingly, the present invention provides an improved process for the preparation of carboxylic acids which comprises; reacting 0.010 to 0.014 mol of an aldehyde, in presence of a polar solvent, an initiator having strength 50-100%, an oxidant and a heterogenous catalyst, at a temperature in the range of 80-120°C, pressure ranging from 400 to 500 psi for a period of 2 to 10 hrs, cooling the reaction mixture to room temperature, separating corboxylic acids from the said mixture by convectional methods, the said process characterized in that in using heterogenous catalyst and an initiator. In one of the embodiments of the present invention initiator used may be such as TBHP, H2O2 ethylenebenzene hydroperoxide and cumena hydroperxide. In another embodiment the concentration of initiator may be in the range of 30-100%. In another embodiment, the solvent used may be selected from organic solvent such as acetic acid, acetonitrle, water, prop ionic acid, butyric acid etc (but not formic acid) as solvent. In another embodiment the oxidant may be air or oxygen. In yet another embodiment the heterogeneous catalyst used may be titanium silicate (TS-1), vanadium silicate (VS-1) prepared as per procedure given in the Indian patent application no 765/DEL/91. In a feature of the present invention the products were isolated by just filtering and by removal of the organic solvent to afford compound in a pure state. In yet another feature, the catalyst can be reused for the reaction several times without affecting the activity of the catalyst. In yet another feature, the substituents on the aromatic ring could be both electron withdrawing or electron donating groups such as -OMe, -Cl, -NO2 present at ortho or para positions on the aromatic ring, or disubstituted compounds. The conventional methods used to separate the product from the mixture comprises of simple filtration of the catalyst, removal of the solvent under reduced pressure (40 mm) to get the product. The process of the invention is described below with reference to the examples, which are illustrative only and should not be construed to limit the scope of the present invention in any manner. Example 1 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-hydroxybenzoicacid (Conversion: 44 %) (Selectivity: 94 %). Example 2 A mixture of p-Chlorobenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-chlorobenzoicacid (Conversion: 82 %) (Selectivity: 99 %) Example 3 A mixture of p-nitrobenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml WAV) was taken in a parr reactor and stirred at 110°C for 5hrs,at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-nitrobenzoicacid (Conversion: 74 %) (Selectivity: 91 %). Example 4 A mixture of 2-pyridine carboxaldehyde (0.012 mol), VS-1 (10%W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs.at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the 2-pyridine carboxylicacid (Conversion: 70 %) (Selectivity: 90 %). Example 5 A mixture of Anisaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressureof 400 p.s.i. It was filtered to recover the catalyst; solvent removal afforded the anisic acid. (Conversion: 80 %) (Selectivity: 96 %). Example 6 A mixture of propionaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 40°C for 3 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the propionicacid (Conversion: 40 %) (Selectivity: 80%). Example 7 A mixture of n - hexanal (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the hexanoic acid (Conversion: 42 %) (Selectivity: 85%). Example-8 A mixture of cyclohexanecarboxaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the cyclohexanoicacid (Conversion: 42 %) (Selectivity: 85 %). Example 9 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 30%TBHP (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-hydroxybenzoicacid (Conversion: 10 %) (Selectivity: 50 %) Example 10 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and acetonitrile (40 ml W/W) was taken in a parr reactor and stirred at 80°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded mixture of acetamide, aldehyde and p-hydroxybenzoicacid (Conversion: 20%) (Selectivity: 50 %). Example 11 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and methanol (40 ml W/W) was taken in a parr reactor and stirred at 60°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded complex mixture . Example 12 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 70%TBHP (30% W/W), and water (40 ml W/W) was taken in a parr reactor and stirred at 90°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-hydroxybenzoicacid (Conversion: 12%) (Selectivity: 20%). Example 13 A mixture of p-hydroxybenzaldehyde (0.012 mol), VS-1 (10% W/W), 30%H2O2 (30% W/W), and acetic acid (40 ml W/W) was taken in a parr reactor and stirred at 110°C for 5 hrs. at air pressure of 400 p.s.i. It was filtered to recover the catalyst, solvent removal afforded the p-hydroxybenzoicacid (Conversion: 10%) (Selectivity: 5%). The advantages of the present invention are as follows: 1: The process is economically viable. 2: It is environmentally safe. 3: It is easy to handle. 4: It is time saving. We Claim: 1. An improved process for the preparation of carboxylic acids which comprises; reacting 0.010 to 0.014 mol of an aldehyde, in presence of a polar solvent, an initiator having strength 50-100%, an oxidant and a heterogenous catalyst, at a temperature in the range of 80-120°C, pressure ranging from 400 to 500 psi for a period of 2 to 10 hrs, cooling the reaction mixture to room temperature, separating corboxylic acids from the said mixture by convectional methods, the said process characterized in that in using heterogenous catalyst and an initiator. 2. An improved process as claimed in claim 1 wherein, the oxidant used is air or oxygen. 3. An improved processes as claimed in claims 1 and 2 wherein the initiator used is selected from H2O2, tertiary butylhydroperoxide (TBHP), ethylenebenzene hydroperoxide, cumene hydroperoxide but preferably TBHP having strength 70%. 4. An improved process as claimed in claim 1, wherein an aldehyde is selected from p- hydroxy benzaldehyde, p-chloro benzaldehyde, p-nitrobenzaldehyde, 2-pyridine carboxaldehyde, anisaldehyde, propionaldehyde, n-hexeanol, cyclohexane carboxaldehyde. 5. An improved process as claimed in claims 1 to 4 wherein, the polar solvent used is selected from organic solvent such as acetic acid, acetonitrile, water, propionic acid, butyric acid. 6. An improved process as claimed in claim 1 wherein the heterogeneous catalyst used is selected from titanium silicate (TS-1), vanadium silicate (VS-1), Chromium silicate (CrS-1) preferably vanadium silicate (VS-1) 7. An improved process for the preparation of carboxylic acid substantially as herein described with reference to examples.

Documents:

1492-del-1999-abstract.pdf

1492-del-1999-claims.pdf

1492-del-1999-correspondence-others.pdf

1492-del-1999-correspondence-po.pdf

1492-del-1999-description (complete).pdf

1492-del-1999-form-1.pdf

1492-del-1999-form-19.pdf

1492-del-1999-form-2.pdf