Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF SECONDARY ALCOHOLS BY OXICATION OF ALKANES"

Abstract

"An improved process for the preparation of secondary alcohols by oxidation of alkanes". This invention relates to an improved process for the preparation of secondary alcohols by oxidation of alkanes which comprises of contacting individual n-alkane or in mixture with oxygen, air or oxygen containing inert gas such as nitrogen in presence of boric acid of fatty acid mixed with water at temperature between 150-200°C and pressure between 0.01 to 10 bar.

Full Text

Background of the information This invention relates to an improved process for the preparation of secondary alcohols by oxidation of n-paraffms. The invention is particularly concerned with a process for the oxidation of n-paraffin in presence of boric acid, or boric acid esters, mixed with water, selectively, yields secondary alcohols. Fatty alcohols, having C12.C15 carbon chains and their derivatives are important commercial products as plasticizers, surfactants and in the production of polymers, monomers, lubricating oils. Viscosity improvers and pour point depressants greases etc. Fatty alcohol derivatives are used to a great extent in the premium house hold detergents for performance and environmental reasons. These surfactants are readily biodegradable and are finding increased use in low phosphate and non-phosphate detergents. The alcohol provides the starting material for all types of surfactants e.g. non-ionics anianics, catiaric and zwitterianics of Ci2-Cis find applications in consumer products e.g. Toothpaste, hair shampoos, carpet shampoos and light duty house hold detergent. Polyethoxyiates alcohols sulphates and neutralized products gives anionic surfactants had wide applications as light duty detergent and heavy duty house hold liquid & granular detergent. Polyethoxylated alcohols have numerous industrial applications as wetting agents, dispersing agents and errfulsifiers. It is well known in the literature that these fatty alcohols can be produced directly via oxidation of n-paraffins. Studies to prepare fatty alcohols via oxidation of n-paraffins. Studies to prepare fatty alcohols via oxidation of n-paraffins in presence of boric acid * and arsenous acids, aluminium and chromic hydroxides and potassium permanganate are described in J. Soc. Chem. Ind. Jpn., 47, pp. 475-477, 1944; ibid-46, pp. 765-7, 1943 and Ann. Chim. Appl., 39, pp. 311-20, 1949. In all the above investigations the alcohol formation is accompanied by the formation of large amount of by-products such as acids, esters and carboxyl compounds etc., resulting in a complex mixture of oxygenated compound; the isolation of alcohols from such complex mixture is very difficult. Baskhirov et.al. and Baskirov and Kamzolkim (Proc. Acad. Sci. U.S.S.R. Chem. Tech. Sec., 1, pp 118-119, 1956 and World Pet. Congr. 4, pp. 175-183, 1959) described the process for oxidation of individual n-paraffins with nitrogen-oxygen mixture containing 3.0 to 4.5% oxygen at 165 -170°C mixture containing 3.0 to 4.5% oxygen in liquid phase at 165-170°C in presence of boric acid or to produce secondary fatty alcohols with same • number of carbon atoms and the same skeletal structure of the starting paraffin. The yield of alcohols was reported to be about 70% of the n-paraffms feedstock. Various boron derivatives e.g. tributoxy boroxine, tributoxy borane, boron trioxide with or without lithium oxide have also been reported to be used in the oxidation of n-paraffin to alcohols. The yield of alcohols were however low in the range of 16-21% at 10-30% paraffin conversion. In US patent no. 3,238,238 (1966), use of oxidation catalysts such as Mg, Co or V napthenate, oleate or acetate with t-butylborate and an inert diluent oxidize aliphatic hydro-carbons to alcohols at 130-180°C. Japanese patent no 6,27,267 (1987) describes a process to prepare alcoholic waxes by liquid-phase oxidation of C2o-Ceo paraffins waxes with oxygen in presence of 1.0:0.5 - 1.0 mol mixture of HaBQs and 8263; about 73% conversion to alcohols were reported. A process for preparing secondary alcohols by oxidation of Cio-C30 n-paraffins using finely divided orthoboric acid at 156-60°C has been claimed to given about 70% selectivity to alcohol formation. (Neth. Patent appl. 6, 50g857 (1966)). Use of promoters such as ammonia, amines, imides, amides, pyridine etc. were found to promote the oxidation of alkanes or cycloalkane with boric acid or dehydrate boric acid (French patent no- 1,501,429 (1967)). US patent no 4,970,346 (1990) disclose a process for the production of detergent range alcohols and ketones from Ci0-C18 alkanes by reacting with a hydroperoxide in the presence of dicyano bis (1,10 = phenanthrolene) iron (II) catalyst. The use of transition metal catalysts to prepare C10-Ci8 alcohols have been described in US patent no's-4,978,800 (1990) and 4,978,799 (1990); the conversion to alcohols obtained were low (~ 2% wt) even at longer reaction time of 20 h. The oxidation of alkanes in presence of boric acid or esters to produce alcohols was claimed to be accelerated by use of 50-100.ppm transition metal as a 3d-carboxylate. (Brit. Patent no- 1,035,624 (1966)). Various oxidation catalysts were reported in literature including Mn-Naphthenate Mn02KMnO4 t-Butyl per oxide, Co-strearate, TiCU, etc. to increase the yield of Borate ester. Amine & NH3 were used to reduce the deactivation effect of aromatics. Use of additives such as boron trioxide, tributyl oxyboroxine, oxybis (di-n-butoxy borane) and t-butyl hydroperoxide is known to increase the formation of alcohols but only marginally. In the hitherto known processes, generally the yield of alcohols and conversion of n-paraffins perpass range between 16-21% and 10-30% respectively. The selectivity of alcohols and ketones combined together range between 80-90% based on paraffin. Further in these processes there is always a possibility of coagulation of boric acid or boric acid esters due to their poor solubility and density difference between boric acid and hydrocarbon phase. This leads to poor activity of boric acid and decrease the yield of alcohols. The main object of the present invention to provide improved process for the oxidation of paraffins. It is an object of the present invention to provide a procer.s in which the boric acid as solution in water is used to improve the yield of secondary alcohols in the oxidation of paraffins. Summary of the invention In accordance with the present invention, it has been found that boric acid solution in water improves the selectivities and yield of secondary alcohols when used to produce secondary alcohols via oxidation of n-paraffms. During the investigation related to the research of using boric acid solution and developing a process for the oxidation of n-alkanes the inventors of the present invention found that when boric acid is used as solution in water, it improves dispersion of boric acid in the reaction mixture. Since the oxidation reaction is performed at relatively higher temperature than the boiling point of water, the water present in the system is converted into water vapour which provides increased mixing and dispersion , of boric acid. Further reprecipitation of boric acid from the boiling solution converts boric acid into very small particles thus improves the available surface area of contact with nalkanes per oxides producing alcohols at a faster rate. The reaction was carried out in cylindrical glass reactor having a thermometer pocket, a sintered disc at the bottom to bubble the N2 + O2 mixture. The reactor was connected to a reflex condenser through Dean and Stark receiver-to remove water. Out let gases were passed though a gas meter. The reactor can be heated electrically from the outside. The paraffin feed is taken in the reactor while N2 + O2 mixture of known concentration is bubbled through the paraffin at a required rate. The contents of the reactor is heated to the desired temperature for a specified and then boric acid water i solution is added to it. The reaction is continued for same. The water formed in the reaction or water added is removed with the help of liquid separator. After the reaction is over product is cooled and taken out in a RB flask. The unreacted paraffin is removed under reduced pressure to the extent possible. The extent & yield of the alcohols were monitored in terms of the yield of Borate ester which was worked up usual work procedure as given below: The borate ester left as residue is hydrolysed with equal quality of water at reflux temperature. The aqueous layer is evaporated to get boric acid. The organic portion is digested with alkali to remove organic acid which can be recovered by neutralization of aqueous portion. The organic portion is again distilled to recover the secondary alcohols. According to the specific feature of the present invention, there is provided an improved process for the preparation of secondary alcohols which comprises: (a) Contacting n-alkanes having 10-20 carbon atom with boric acid water solution. (b) Contacting the resulting mixture with air, 02 or oxygen containing inert gas such as N2 at a temperature in the range of 150-250°C and at a pressure of atmospheric to 10 bar for a period in the range of 1-10 h at a space velocity of CVnitrogen mixture of1-200h'1. (c) Separating the unreacted n-alkanes, secondary alcohol borate esters and unreacted boric acid by distillation. (d) Recovering the secondary alcohols by hydrolysis of borate esters; and (e) Recycling, if desired the n-alkanes and boric acid in step (a) and (b). Accordingly the present invention provides an improved process for the preparation of secondary alcohols which comprises of contacting n-alkanes with air, nitrogen & 02 mixture in presence of aqueous boric acid, which provides higher selectivity of secondary alcohols. The invention has been described in conjunction with examples and by reference to the .embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description, accordingly it is intended in the invention to embrace these and all such alternatives, variations, aid modifications as may fall within the spirit and scope of the appended claims: 6- Example -1 99.5 g of the paraffin mixture (9-11) along with 3g boric acid was taken in a cylindrical glass reactor with a reflux condenser at the top and heated electrically from outside and have a sintered disc at the bottom to bubble the oxygen, nitrogen mixture. The O2/N2 mixture was fed at a rate of 41 lit/hr. The temperature of the paraffin was increased to 155°C in 1 hr. The reaction was continued for 270 minutes. After the reaction was out reacted paraffin was removed by distillation under reduced pressure. The residue was hydrolysed by boiling with water to decompose the borate esters of sec-alcohol. The organic layer thus obtained was treated with alkali to remain traces of boric acid and other acids. The organic product was distilled to attain secalcohol. The yield of the sec-alcohol was only 0.26%. Example-2 The experiment was carried out as described in example-1 except that the paraffinic mixture was having n-paraffine for C10-15 and the reaction temperature was 180°C instead of 1552°C. The yield of the alcohols after usual workup was 15.5%. Example -3 The experiment was carried out as described in example-2 except that a feed of C10- C14 was taken instead of C11-C15 and two lots of 3g boric acid in 25 ml paraffine mixture were added in 10 min time after attaining the reaction temperature respectively. Total reaction time was 150 minutes. The yield of sec-alcohol after workup was 14.5%. Example -4 The experiment was carried out as example-2 except that 3g boric acid was added as solution in 100 ml water during 90 minutes and total reaction time was 180 minute. The yield of sec-alcohol after work up was 18.6%. Example-5 The experiment was carried out as.described in example-4 except 200 g of the recovered paraffin mixture was used. The CVNa mixture feed rate was 80 lit/hr and 6 g boric acid in 65 ml water was added in 40 min. The addition of boric acid was done ak the bottom of the reactor. Reaction time was 70 min. The yield of sec-alcohol was found to be 21.4%. Example-6 The experiment was carried out as described in example 4 except that 200 g of paraffine mixture was used with catalyst A and O2/N2 mixture feed rate was 80 lit/hr. Two lots of 6 g each of boric acid were added as solution in 65 ml water. The boric acid was added in 17 and 20 min respectively. The yield of sec-alcohol was 23.5%. We Claim: 1. An improved process for the preparation of secondary .alcohols by oxidation of. alkanes which comprises of contacting individual n-alkane or in mixture with oxygen, air or oxygen containing inert gas such as nitrogen in presence of boric acid of fatty acid mixed with water at temperature between 150-200°C and pressure between 0.01 to 10 bar. 2. A process of claim 1, wherein the concentration of boric acid is 0.1 to 10 wt% of n- paraffin. . 3. A process of claims 1&2 wherein the boric acid is used as solution In water. 4. A process of claims 1 to 3 wherein the pressure is in the range of 0.01 to 10 bar. 5. A process of claims 1 to 4 wherein the temperature is in the range of 150-250°C. 6. A process of claims 1 to 5 wherein the contacting of n-alkanes with O2l air, or O2 containing inert gas is continuous or batch wise. 7. A process for the preparation of secondary alcohols by oxidation of n-alkanes using boric acid as solution in water which comprises. (a).Contacting n-alkanes having 10-20 carbon atom with boric acid water solution. (b).Contacting the resulting mixture with air, Oa-or.oxygen containing inert gas such as N2 at a temperature in the range of 150-250°C and at a pressure of atmospheric to 10 bar for a period in the range of 1-10 h at a space velocity of Qi^aitrogjen mixturejDf 1-20Qh*l (c). Separating the unreacted n-alkanes, secondary alcohol borate esters and . unreacted boric acid by distillation.

Documents:

1133-DEL-2002-Abstract-11-11-2007.pdf

1133-del-2002-abstract.pdf

1133-DEL-2002-Claims-11-11-2007.pdf

1133-del-2002-claims.pdf

1133-DEL-2002-Correspondence-Others-11-11-2007.pdf

1133-del-2002-correspondence-others.pdf

1133-del-2002-correspondence-po.pdf

1133-del-2002-description (complete).pdf

1133-DEL-2002-Form-1-11-11-2007.pdf

1133-del-2002-form-1.pdf

1133-del-2002-form-18.pdf

1133-del-2002-form-2.pdf

1133-DEL-2002-Form-3-11-11-2007.pdf

1133-del-2002-form-3.pdf

1133-del-2002-gpa.pdf