Title of Invention

"A PROCESS FOR THE PREPARATION OF N-ALKANES"

Abstract

The present invention provides for a process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3c, omprising the steps of refluxing a mixture of 8 to 16 wt.% of 2,4-pentanedione, 5 to 25 wt.% of 1- bromoalkane, 0.6 to 1.0 wt.% of a phase transfer catalyst, 15 to 25 wt/% of anhydrous potassium carbonate, 40 to 60 wt.% of aliphatic short chain alcohol at 80 to 100°C with continuous stirring for 24 to 42 hrs. to obtain a methyl ketone; preparing -n-alkanes by refluxing the methyl ketone obtained in step(i) with a mixture of 8 to 15 wt.% of hydrazine hydrate, 10 to 15 wt.% of potassium hydroxide pellets and 55 to 70 wt.% of diethylene glycol or triethylene glycol at 90 to 130°C with continuous stirring for 4 to 8 hrs. followed by removal of water and excess hydrazine from the mixture by distillation and further refluxing at 200 to 230°C to 8 to 16 hrs. The product so obtained is of high yield and purity.

Full Text

HELD OF INVENTION: The present invention relates to a new process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3 where n=6-17. BACKGROUND OF INVENTION: The hydrocarbons are the most broadly used organic compounds known, and are quite literally the driving force of western civilization. The greatest amounts of hydrocarbons are used as fuel for combustion, particularly in heating and motor fuel applications. With pentane, the saturated hydrocarbons enter the realm of room-temperature liquids. This makes them useful as organic solvents, cleaners, and transport fuels. Gasoline for internal combustion engines in cars, trucks, tractors, lawnmowers, and so on, is rated in combustion properties relative to octane. It is in fact a combination of liquid hydrocarbons ranging from hexanes to decanes. Slightly larger hydrocarbons are known as kerosene or jet fuel, diesel fuel and heating oil. Still larger hydrocarbon molecules serve as lubricating oils, and greases. Eventually a point is reached at which the materials are solids at room temperature. These are the waxes. Hydrocarbon molecules larger than those of the waxes are the heavy greases and the tars commonly used in roofing applications and highway construction. In the last two decades, hydrocarbons are found to have new important applications such as insect pheromones and special lubricants in high-tech areas. This new utility as insect pheromones has lead to requirement of synthesis of pure hydrocarbons. One of the processes known in the art for the preparation of aliphatic straight chain saturated hydrocarbons involves generation from the thermal 'cracking' and fractional distillation of crude oil (Ref: Morrison, R.T. & Boyd, R. N. Organic chemistry, Prentice Hall publications, Sixth edition, 1992, page 94). the main disadvantage of this technology is that the above process is very tedious as it involves separation of pure hydrocarbons by fractional distillation from the mixture of close boiling hydrocarbons. Still another disadvantage of this technology is that the composition of raw material varies with source of petroleum well. Another disadvantage of this technology is that the process is not cost effective for preparation of pure 9 hydrocarbons. Another known process in the art for preparation of aliphatic straight chain saturated hydrocarbons involves hydrolysis of alkyl magnesium halide. The major drawback of this method is that the process involves the use of dried diethyl ether, which has very low flash point and highly inflammable for the preparation of alkyl magnesium halide. Since the reaction is moisture sensitive, great caution should be employed in storage, handling and transfer operations. Another drawback of this method is that the overall yield of the final product is low. Still another drawback of this process is that the use of magnesium leads to large quantities of toxic effluent; thus the process is not environment friendly. Another process for the preparation of aliphatic saturated hydrocarbons involves catalytic synthesis from carbon monoxide or carbon dioxide. Reference is taken from European Patent publication No. UA78656, dated 10.04.2007. Aliphatic hydrocarbons containing more than one carbon atom, particularly liquid hydrocarbons, are produced by reacting mixtures of carbon monoxide/carbon dioxide with atleast an equal volume of hydrogen in the presence of catalysts, at ordinary or slightly increased or reduced pressure, and at temperatures of 180-200° C. The main disadvantage of this process is that mixture of hydrocarbons is produced and required pure hydrocarbon from the mixture of products. Another disadvantage of this process is the use of two gases viz carbon monoxide or carbon dioxide and hydrogen at high pressure and temperature. Maintenance of same condition is required for the formation of the required hydrocarbon product. Yet, another disadvantage of this method is the use of highly inflammable gas, hydrogen as the raw material which makes the process hazardous. Yet another disadvantage of this process is the use of particular catalyst composition. The formation of the required" hydrocarbon decreases when the catalyst activity" decreases and varies with the composition of the catalyst. Another disadvantage of this method is that it requires special equipment, thus this process is not cost-effective also. Another disadvantage of this process is that it is not suitable for hydrocarbons having more than 10 carbon atoms. Another method reported in the literature is the preparation of alkanes by Wurtz reaction i.e. reaction of sodium with alkyl halides to give even numbered carbon containing symmetrical alkanes. The main drawback of this method is that it is suitable only for the preparation of even numbered carbon containing symmetrical alkanes. Another drawback of this method is the use of sodium metal which is highly reactive (moisture sensitive, flammable). Dangerous explosion may result if sodium come comes in contact with water. Another drawback of this reaction is that it is not suitable for upscaling as handling of sodium in more quantity requires further more safety procedures. OBJECTS OF THE INVENTION: There is a need to develop a simple and cost effective method for the preparation and process development of n-alkanes which can be upscaled to manufacturing process and overcome the disadvantages/drawbacks of the processes known in the art. The main objective of the present invention is to provide a novel and simple method for the preparation of n-alkanes using indigenously available raw materials to make the process cost effective. Another objective of the present invention is to provide and environment friendly process without using any hazardous chemicals. Another objective of the present invention is to provide a simple process for the preparation of n-alkanes which give pure product for its use as pheromones. Still another objective of the present invention, is to provide a new process for the preparation of n-alkanes which do not require the use of any flammable moisture sensitive reagents. Yet another objective of the present invention is to provide a new process for the preparation of n-alkanes which gives excellent yield. Still another objective of the present invention is to provide a novel process for the synthesis of n-alkanes which can easily be upscaled. Still another objective of the present invention is to provide a new process for the preparation of n-alkanes in which effluent load is minimum. STATEMENT OF INVENTION: The present invention relates to a process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3, comprising of the steps of: (i) refluxing a mixture of 8 to 16 wt. % of 2,4-pentanedione, 5 to 25 wt. % of 1-bromoalkane, 0.6 to 1.0 wt. % of a phase transfer catalyst, 15 to 25 wt. % of anhydrous potassium carbonate, 40 to 60 wt. % of aliphatic short chain alcohol at 80 to 100° C with continous stirring for 24 to 42 hrs, to obtain a methyl ketone. (ii) preparing n-alkanes by refluxing the methyl ketone obtained in step (i) with a mixture of 8 to 15 wt. % of hydrazine hydrate, 10 to 15 wt % of potassium hydroxide pellets and 55 to 70 wt. % of diethylene glycol or triethylene glycol at 90 to 130°C with continuous stirring for 4 to 8 hrs. followed by removal of water and excess hydrazine from the mixture by distillation and further refluxing at 200 to 230° C for 8 to 16 hrs. DETAILED DESCRIPTION OF THE PROCESS: The purpose of the present invention is to provide a process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3, comprising of the steps of: (i) reacting a mixture of 2,4-pentanedione with 1-bromoalkanes in an alcohol selected from isopropanol, n-propanol, ethyl alcohol and n-butanol, using a phase transfer catalyst, to obtain a methyl ketone. (ii) n-alkanes are prepared by reduction of methyl ketones so obtained in step (i) using hydrazine hydrate and potassium hydroxide in diethylene glycol. In the first step methyl ketones are prepared by refluxing a mixture of 2,4-pentanedione 8-16 % by wt. preferably 12-14 % by wt., 1-bromoalkane 5-25 wt. %, preferably 10-20 wt. %, a phase transfer catalyst 0.6 to 1.0 wt. %, preferably 0.8 to 0.9 wt. %, anhydrous potassium carbonate 15 to 25 wt. % preferably 17 to 20 wt. % and an alcohol 40 to 60 wt. % preferably 49-55 wt. % were added by stirring. The mixture is refluxed at 80-100° C preferably 85 to 95° C with continuous stirring for 24-42 hrs preferably 30 to 36 hrs; after refluxing at the said temperature, the mixture was cooled to ambient temperature (25° C), equal volume of water was added to it and the methyl ketone was extracted with dichloro methane from the mixture. On distillation of dichloro methane, methyl ketone yield greater than 85% is obtained. 1-bromoalkane is selected from 1-bromoalkanes, having the carbon number from 5 to 16. The alcohol is selected from a group of ethanol, n-propanol, isopropanol, isobutanol, n-butanol, n-pentanol and a combination thereof. The catalyst used for the process is a phase transfer catalyst of the kind 18-crown-6 (IUPAC name 1,4,7,10,13,16-hexaoxacyclooctadecane) and tetramethyl ammonium bromide (TMAB). In the second step (step ii) n-alkanes from methyl ketone obtained in step (i) is prepared by refluxing with a mixture of hydrazine hydrate 8 to 15 % by wt. preferably 10-12 % by wt., potassium hydroxide pellets 10 to 15 % by wt. preferably, 11 to 13 % by wt. and diethylene glycol or triethylene glycol 55 to 70 % by wt. preferably 60 to 65 % by wt. refluxed at 90 to 130° C preferably 110 to 120° C with continuous stirring for 4 to 8 hrs preferably 6 to 8 hrs, followed by removal of water and excess hydrazine from the mixture by distillation and further refluxiflg of the mixture at elevated temperature of 200 to 230° C preferably 210 to 220° C for 8 to 16 hrs. preferably 11 to 13 hrs. After this the reaction mixture is cooled at ambient temperature (25° C) and treated with equal volume of water. The n-alkane is seperated by extraction with dichloromethane followed by evaporation. The crude alkane can further be purified by distillation. The over all yield of n-alkanes is greater than 80% and the overall yield is greater than 99%. the process is simple and is eco-friendly. The details of the alkanes and methyl ketones obtained from different bromoalkanes are described below: (Table Removed) EXAMPLES: Example 1: To a 2 L two-necked round bottom flask equipped with water condenser, calcium chloride guard tube and mechanical stirrer, 127 gm of 2,4-pentanedione, 190 gm of 1-bromohexadecane, 8.5 gm of 18-crown-6, 175 gm of anhydrous potassium carbonate and 500 ml of isopropanol were added with stirring. The mixture was refluxed at 90° C with continuous stirring for 30 hrs; after refluxing at the said temperature, the mixture was cooled to ambient temperature (25° C), equal volume of water was added to it and the 2-nonadecanone was extracted with dichloromethane from the mixture. On distillation of dichloromethane, 2-nonadecanone was obtained. The so formed 2-nonadecanone was taken in a 3 L two-necked flask equipped with water condenser, calcium chloride guard tube and mechanical stirrer. To this, 300 ml of hydrazine hydrate, 325 gm of potassium hydroxide pellets and 1500 ml of diethylene glycol were added with stirring. The mixture was refluxed at 110°C with continuous stirring for 6 hrs. water and excess hydrazine from the mixture were removed by distillation and the temperature was elevated slowly to 210° C for 11 hrs. After this, the reaction mixture was cooled to ambient temperature (25° C) and treated with 1500 ml of water. The n-nonadecane separated by extraction with dichloro methane followed by evaporation. The crude n-nonadecane was purified by distillation. The over all yield was > 90% and purity is >99%. Example 2: To a 2 L two-necked round bottom flask equipped with water condenser, calcium chloride guard tube and mechanical stirrer, 135 gm of 2,4-pantanedione, 250 gm of 1-bromododecane, 9 gm of 18-crown-6, 180 gm of anhydrous potassium carbonate and 500 ml of n-butanol were added with stirring. The mixture was refluxed at 95° C with continuous stirring for 24 hrs, after refluxing at the said temperature, the mixture was cooled to ambient temperature (25° C), equal volume of water was added to it and the 2-pentadecanone was extracted with dichloromethane from the mixture. On distillation of dichloromethane, 2-pentadecanone was obtained. 2-pentadecanone so obtained was taken in a 3 L two-necked flask equipped with water condenser, calcium chloride guard tube and mechanical stirrer. To this, 330 ml of hydrazine hydrate, 350 gm of potassium hydroxide pellets and 1600 ml of triethylene glycol were added with stirring. The mixture was refluxed at 120°C with continuous stirring for 8 hrs. Water and excess hydrazine from the mixture were removed by distillation and the temperature was elevated slowly to 220° C for 12 hrs. After this, the reaction mixture was cooled to ambient temperature (25° C) and treated with 1600 ml of water. The n-pentadecane separated by extraction with dichloro methane followed by evaporation. The over all yield was greater than 88%. We Claim: 1) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3, comprising the steps of : (i) refluxing a mixture of 8 to 16 wt.% of 2,4-pentanedione, 5 to 25 wt.% of 1- bromoalkane, 0.6 to 1.0 wt.% of a phase transfer catalyst, 15 to 25 wt/% of anhydrous potassium carbonate, 40 to 60 wt.% of aliphatic short chain alcohol at 80 to 100°C with continuous stirring for 24 to 42 hrs. to obtain a methyl ketone; (ii)preparing -n-alkanes by refluxing the methyl ketone obtained in step(i) with a mixture of 8 to 15 wt.% of hydrazine hydrate, 10 to 15 wt.% of potassium hydroxide pellets and 55 to 70 wt.% of diethylene glycol or triethylene glycol at 90 to 130°C with continuous stirring for 4 to 8 hrs. followed by removal of water and excess hydrazine I from the mixture by distillation and further refluxing at 200 to 230°C to 8 to 16 hrs. 2) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3a s claimed in claim 1, wherein x= 6 to 17. 3) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3 as claimed in claim 1,wherein 1-bromoalkane carbon number from 5 to 16. 4) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3a s claimed in claim 1, wherein the aliphatic short chain alcohol is selected from ethanol, n-propanol, isopropanol, isobutanol, n-butanol, n-pentanol or a combination thereof. 5) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3a s claimed in claim 1, wherein phase transfer catalyst is of the kind 18 crown 6 or tetramethyl 1 i ammonium bromide (TMAB) . 6) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3a s claimed in I 1 claim 1, wherein the amount of 2,4-pentanedione is 12-14 wt.%, 1-bromoalkane is 10- 20 wt.%, the phase transfer catalyst is 0.8 to 0.9 WtO/o, anhydrous potassium carbonate is 17 to 20 wt.% and the aliphatic short chain alcohol is 49-55 wt.%. 7) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3 as claimed in claim 1, wherein the reflux temperature for step(i) is 85 to 95OC; for step(ii) is 110 to 120°C; and the temperature for further refluxing the mixture is 210 to 220°C. 8) A process for the preparation of n-alkanes of the formula n-CH3(CH2)xCH3a s claimed in claim 1,wherein the refluxing duration for step (i) is 30 to 36 hrs and for step (ii) is 6 to 8 hrs; and time for further refluxing is 11 to 13 hrs.

Documents:

68-del-2008-Abstract-(18-04-2013).pdf

68-del-2008-abstract.pdf

68-del-2008-Claims-(18-04-2013).pdf

68-del-2008-claims.pdf

68-del-2008-Correspondance Others-(18-04-2013).pdf

68-del-2008-Correspondence Others-(04-09-2008).pdf

68-del-2008-correspondence-others.pdf

68-del-2008-description (complete).pdf

68-del-2008-form-1.pdf

68-del-2008-Form-18-(04-09-2008).pdf

68-del-2008-form-2.pdf

68-del-2008-form-3.pdf

68-del-2008-form-5.pdf