|Title of Invention||
"AN IMPROVED PROCESS FOR PREPARING SECONDARY ALCOHOLS"
|Abstract||This invention relates to an improved process for preparing secondary alcohols comprising of contacting the n-paraffins with oxygen, air or oxygen containing inert gas such as nitrogen and boric acid or borate ester of fatty acid, the said boric acid/borate ester concentration is 0.1 to 10% weight of the n-paraffin, at temperature in the range of 150-250°C, and pressure in the range of 0.01 to 10 bar for a period of 1-10 h, characterized by; Mixing the n-paraffin with the catalyst in the range between 1-500 ppm, the said catalyst comprises an alkyl, aryl or alkyl-aryl phosphate of a group-VIII metal preferably Zn; Recovering the secondary alcohols by hydrolysis of borate ester produced in the step (b) above.|
|Full Text||Background of the Invention
This invention relates to an improved process for preparing secondary alcohols using the catalyst. The invention is particularly concerned with a catalyst comprising of an alkyl, aryl or alkyl-aryl phosphates or this phosphates of metals which catalyses the oxidation of n-paraffins to selectively yield 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 alcohols provides the starting material for all types of surfactant e.g. non-ionics anianics, catiaric and zwitterianics of C12-C15 find applications in consumer products e.g. Toothpaste, hair shampoos, carpet shampoos and light duty house hold detergent. Polyethoxylates 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 emulsifiers.
These fatty alcohols can be produced directly via oxidation of n-paraffms. Studies to prepare fatty alcohols via oxidation of n-paraffins. Studies to prepare fatty alcohols via oxidation of n-paraffms in presence of boric acid and arseous 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 these 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.
Bashkirov et.al. and Bashkirov and Kamzolkim (Proc. Acad. Sci. U.S.S.R. Chem. TV. h.
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-paraffins 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-C6o paraffins waxes with oxygen in presence of 1.0:0.5 -
1 .0 rnol mixture of HaBOs and B2O;j; 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)).
The use of transition metal catalysts to prepare Cio-Cie 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
US patent no 4,970,346 (1990) disclose a process for the production of detergent range
alcohols and ketones -from Cio-Cis alkanes by reacting with a hydroperoxide in the
presence of dicyano bis (1 ,10 = phenanthrolene) iron (II) catalyst.
Various oxidation catalysts were reported in literature including Mn-Naphthenate
KMnO4, t-Butyl per oxide, Co-strearate, TiCI4l etc. to increase the yield of Borate ester.
Amine & NHs were used to reduce tfie 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-paraffms perpass is low and 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 lower yield of
The main object of the present invention is to provide a catalyst that provide an
improved process for the oxidation of n-paraffins to produce secondary alcohols. It is an
object of the present invention to provide a process in which the use of the said catalyst
increases the yield of secondary alcohols in the oxidation of n-paraffms. It is yet another
object of the present invention to provide catalyst that decomposes the hydro-peroxides
in the free radical oxidation of paraffins and thereby increasing the formation and
selectivity of secondary alcohols.
STATEMENT OF INVENTION
According to this invention there is provided an improved process for preparing secondary alcohols comprising of:
a. Contacting the n-paraffins with oxygen, air or oxygen containing inert gas such
as nitrogen and boric acid or borate ester of fatty acid, the said boric acid/borate
ester concentration is 0.1 to 10% weight of the n-paraffin, at temperature in the
range of 150-250°C, and pressure in the range of 0.01 to 10 bar for a period of
1-10 h, characterized by;
b. Mixing the n-paraffin with the catalyst in the range between 1-500 ppm, the said
catalyst comprises an alkyl, aryl or alkyl-aryl phosphate of a group-VIII metal
c. Recovering the secondary alcohols by hydrolysis of borate ester produced in the
step (b) above.
SUMMARY OF THE INVENTION
In accordance with the invention, it has now been found that organo-metallic compounds, particularly the alkyl, aryl or alkyl-aryl phosphates of specific metals when used as catalyst enhance the formation of secondary alcohols in the oxidation of n-paraffins in presence of boric acid/boric acid ester.
The metal part of alkyl, aryl, or alkyl-aryl phosphate is selected from the metals of Group-VIIl of the Periodic Table of Elements. During the course of investigations to enhance the selectively of formation of secondary alcohols in the oxidation of n-paraffins having 10-20 carbon atoms in presence boric acid/borate esters the inventors have found that the use of alkyl, aryl or alkyl-aryl phosphates of metals of Group VIII of the Periodic Table of Elements and more particularly of Zn increases the formation of secondary alcohols. These organo-metallic compounds decompose the hydroperoxides formed during the oxidation process to non-radical products, thus preventing the chain propagation leading to over oxidized products such as acids, carboxyl compounds, CO and CO2. The mechanism involves complex interactions between alkyl peroxy radicals, organic peroxide and intermediate decomposition products by the initied compounds.
The present invention further relates to the application organo-metallic compounds of metals of Group-VIIl of the Periodic Table of Elements particularly Zn in oxidation of n-paraffins and provides a process to oxidise n-paraffins with O2/air/nitrogen and oxygen mixture in presence of boric acid under moderate operating conditions to selectively produce secondeiry edcohols.
The reaction is carried out in cylindrical reactor having a, a sintered disc at the bottom to bubble the N2 and 02 mixture. The reactor was connected to a reflex condenser through Dean and Stark receiver to remove water. The paraffin feed is taken in the reactor while N2 + 02 mixture of known concentration is bubbled through the paraffin at space velocity ranging between 1-250 h-1. The contents of the rector is heated to the desired temperature and then boric acid, 0.1 to 10% wt% of n-paraffin is added to it.
1 reaction is continued and water is removed with the help of clean and stark separator.
After about 2 hour 10-1000 ppm of measured amount organo-metallic phosphate Zn
compound is added to the reaction mixture and the reaction is continued. After the
reaction is over product is cooled and taken out. 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
It will be apparent from the foregoing that the present invention provides a catalyst
which is active and selective for producing secondary alcohols via oxidation of
n-paraffins. Moreover the catalyst of the present invention which comprises an alkyl,
aryl or alkyl-aryl phosphate of a Group-VIII metal preferably Zn is unexpectedly active
selective for oxidation of n-paraffins to produce secondary alcohols.
Although 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, and modifications as may fall within the spirit and scope of the
100 g of the paraffins mixture Cn-Ci5 was taken in a cylindrical glass reactor heated
electrically from outside and having a sintered disc at the bottom to bubble the oxygen
nitrogen mixture. The oxygen nitrogen mixture was fed at a rate of 40 litre per hour.
The temperature was increased from room temperature to 180°C in 1 hour. 3 g of boric
acid in 50 ml water was added in 25 minutes. The reaction was continued for 180
minutes. Water along with same paraffin was collected in Dean and Stark receiver
which was removed from time to time while paraffin was returned to the reactor. After
the reaction was over the unreacted paraffin was removed by distillation under reduced
pressure and residue was hydrolysed with water to decompose the borate ester of
secondary alcohol. The organic layer thus obtained was refluxed with sodium hydroxide
solution to remain traces of boric and other acids. The washed organic layer was again
distilled to obtain secondary-alcohol. The yield of secondary-alcohols was 17.36% at nparaffin
conversion of 19.75%.
Example - 2
The experiment was carried out as described in example-1 except total 6g of boric acid
was added in two lots of 3g each in 25 ml water. The 3g boric acid was added in 45
minutes. The yield of alcohol after was 18.9% at n-paraffm conversion of 17.11%.
200 g of paraffins mixture Gn-Ci5 was taken in a cylindrical glass reactor, heated
electrically from outside and having a sintered disc at the bottom to bubble the oxygen
nitrogen mixture. A Dean and stark assemfcHy was also attached to the reactor to remain
water and lighter component from the feed during the reaction. The oxygen nitrogen
mixture was bubbled at a rate of 80 litre per hour. The temperature of the paraffin was
increased from room temperature to 180°C in 60 minutes. 6 g of boric acid in 65 ml
water was added in 17 minutes after 60 minutes another lot of 6g boric acid in 65 ml
water was again added in 20 minutes. The reaction was continued for additional hour
and after that 0.0997 g of a catalyst was added. The reaction was again continued ior
60 minutes. The yield of sec-alcohol after usual work up and conversion of n-paraffin
were found to be 23.68% and 23.74% respectively.
The experiment was carried out as described in example - 3 except that 100 g paraffins
mixture was taken for the reaction and 6g of boric acid in 2 lots was added to the
reaction mixture. The quantity of the catalyst used was 0.0507 g. The yield of the secalcohol
and conversion of n-paraffin were 24.77% and 25.22% respectively.
1. An improved process for preparing secondary alcohols comprising of:
a. Contacting the n-paraffins with oxygen, air or oxygen containing
inert gas such as nitrogen and boric acid or borate ester of fatty
acid, the said boric acid/borate ester concentration is 0.1 to 10%
weight of the n-paraffin, at temperature in the range of 150-250°C,
and pressure in the range of 0.01 to 10 bar for a period of 1-10 h,
b. Mixing the n-paraffin with the catalyst in the range between 1-500
ppm, the said catalyst comprises an alkyl, aryl or alkyl-aryl
phosphate of a group-VIII metal preferably Zn;
c. Recovering the secondary alcohols by hydrolysis of borate ester
produced in the step (b) above.
2. A process as claimed in claim 1 wherein the n-paraffins have carbon chain containing 10 to 20 carbon atoms.
3. A process as claimed in claim 1 wherein the pressure is in the range of 0.01 to 10 bar preferably 0.01 to 3 bar.
4. A process as claimed in claim 1 wherein the temperature is in the range of preferably 170-200°C.
|Indian Patent Application Number||1130/DEL/2002|
|PG Journal Number||28/2009|
|Date of Filing||11-Nov-2002|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DLEHI-110001, INDIA.|
|PCT International Classification Number||B01J 23/00|
|PCT International Application Number||N/A|
|PCT International Filing date|