CLIAMS:We Claim:

1. A process (200) for preparation of n-propyl benzene, the process (200) comprising the steps of:
a) adding aromatic hydrocarbon having an active hydrogen on a saturated α-carbon and a solid support to a first reactor to form a mixture;
b) adding alkali metal catalyst and oleic acid to the mixture to form a reaction mass and closing and agitating the first reactor for a time period of about 30 minutes to 1 hour;
c) flushing nitrogen gas to the first reactor and heating the reaction mass at a temperature in a range of about 185 to 1900C for about 15 minutes;
d) adding aromatic hydrocarbon and an initiator to a second reactor, the second reactor being flushed with nitrogen gas and stirred for a time period of about 15 minutes to 30 minutes, the second reactor then connected to the first reactor;
e) adding alkene to the first reactor to form a reaction mixture;
f) adding small amount of initiator to the first reactor periodically and maintaining the reaction mixture at temperature in a range of about 180 to 220oC for longer than 1 hour to 5 hours while agitating the reaction mixture at about 35 to 40 kg/cm2;
g) adding desired amount of methanol and water to the reaction mixture;
h) separating the reaction mixture to an aqueous phase for recovery of the catalyst, catalyst support and un-reacted toluene and to an organic phase for obtaining n-propyl benzene and byproduct; and
i) analyzing and purifying the organic phase to generate n-propyl benzene,
wherein, the n-propyl benzene is separated from the byproduct by fractional distillation and analyzed by gas chromatography.

2. The process (200) as claimed in claim 1, wherein the aromatic hydrocarbon having active hydrogen on the saturated α-carbon is toluene.

3. The process (200) as claimed in claim 1, wherein the solid support is alkali metal carboxylate such as potassium carbonate.

4. The process (200) as claimed in claim 1, wherein the alkali metal catalyst is selected from sodium, lithium and combination thereof.

5. The process (200) as claimed in claim 1, wherein the initiator is selected from any one of di-ter-butyl peroxide, azo-iso-bis butyronitrile and iso-amyl nitrite.

6. The process (200) as claimed in claim 1, wherein the initiator is used in a range of 50 to 100 ppm in single stage or in multiple stages.

7. The process (200) of claim 1 further comprising recovering from the reaction mixture un-reacted aromatic hydrocarbon having the active hydrogen on the saturated α-carbon and using at least a portion of the recovered un-reacted hydrocarbon in step (a).
,TagSPECI:Process for Preparation of n-Propyl Benzene

Field of the invention

The present invention relates to an alkylation and more particularly, to a process for preparation of n-propyl benzene.

Background of the invention

Alkyl benzenes are useful, for example as intermediates in the production of various end products. It has been known for decades that alkali metals when reacted with alkyl benzenes displace benzylic hydrogens (Chester E. Claff and Avery A. Morto, J. Org. Chem., 1955, 20(4), pp 440-442, Herman Pines & Norman C. Sih, ibid, 1965, 30(1), pp 280-284, Schramm and Langlois, Journal of the American Chemical Society, 1960, 82, pp 4912-4917). The resulting alkyl benzene anion and alkali metal cation pair undergoes a reaction with olefins at high temperature to give alkylation products in which single or all saturated benzylic carbon atoms are alkylated in such a way as to replace single or all of the benzylic hydrogen atoms on a carbon atom with one aliphatic chain per benzylic hydrogen atom. Such reactions yield a variety of products depending on the number of saturated benzylic carbon atoms and the number of hydrogen atoms on the given benzylic carbon atom. In the commercial production of alkyl benzenes, high purity product is generally desired and byproducts must be removed.

Several patents and publications address issues related to providing suitable methods for commercial production of alkyl benzenes for example, U.S. Pat. No. 8,277,652 B2, U.S.Pat. No. 6,100,437 and U.S.Pat. No. 4,950,831.

The examples cited in U.S. Pat. No. 8,277,652 B2 and U.S. Pat. No. 6,100,437 makes use of sodium-potassium alloy as the catalyst. The catalyst during activation step gets melted but remains as the different phase than the alkyl benzene. This helps metalation of alkyl benzene. Also, the use of small amount of water in the reaction is mentioned in this process. This operation poses difficulties as follows:
• The small amount of catalyst causes inefficient distribution of the catalyst in the alkane phase.
• High temperature promotes the tarry byproducts which cover the catalyst surface and the reaction is lowered.
• Also, the use of sodium-potassium alloy in presence of water is hazardous and affects the process economics.

A serious problem with the present alkali metal especially sodium-potassium alloy catalyzed alkylation reaction is the fact that an alpha carbon of the alkyl benzene anion can add to either carbon atom comprising the olefinic double bond thereby giving two alkylation products. Moderation of reaction conditions has proven to be effective in eliminating multiple alkylations.

However, inability to conveniently improve upon addition selectivity is the problem. In addition to multiple alkylation of the alkyl benzene, the alkali metal catalyst utilized in the alkylation reaction seems to promote insoluble tarry byproducts formation due to poly condensation or the alkali metal catalyzed polymerization reaction. Other byproducts are also formed in the alkali metal catalyzed reactions which are soluble in reaction medium offering darkened color to the reaction medium.

Yet another problem in the present alkali metal catalyzed reaction is the proper distribution of the alkali metal alloy in the reaction system. Reference may be made to U.S. Pat. No. 8,277,652 B2 wherein 0.5 wt% of the sodium-potassium alloy is used as the catalyst. The alloy is used in the neat form and is highly difficult to disperse the small quantity of the catalyst uniformly throughout the reaction medium which is destroyed at the end of the reaction. In order to get good reaction efficiency, the alkyl benzene-potassium ion pair formed in the reaction between the alkyl benzene and potassium should be dispersed effectively in the reaction mixture to get good selectivity for mono-alkylation.

The alkyl benzene-potassium ion pair and the alkyl benzenes form immiscible phases and the malfunctioning of the catalyst distribution in the reaction media leads to the side product formation. Generally, the present system being practiced commercially uses small amount of tall oil and water to help the catalyst and associated catalytic species in emulsified phase in the reaction medium. The small amount of water used in the present commercial practice to emulsify the reaction medium poses a serious safety concern.

It is generally believed that the alkyl benzene-potassium ion pair which is a catalyst complex gets dispersed at the emulsified phase which also coats the alkali metal alloy thus higher surface area is available for the reaction with an alkene. The formation of tars and other byproducts reduces reactant utilization significantly. The formation of tars and other byproducts has further commercial impact that the alkyl benzene-potassium ion pair gets covered by the tarry product which reduces the rate of formation of alkyl benzene though the catalyst is active. The active catalyst covered by the tarry product gets destroyed at the end of production cycle by water. This puts severe pressure on ecology and the process economics.

Similarly, with the present alkali metal alloy system, the alkyl benzenes are isolated after aqueous work-up that is towards end of the reaction water is charged followed by layer separation. This causes trouble of emulsion formation due to high alkalinity of reaction medium as well causes loss of costly alkali metal alloy. The heavy emulsion tends to lose the organic phase. This puts severe pressure on ecology and the process economics.

Schramm and Langlois (Journal of the American Chemical Society, 1960, 82, pp 4912-4917) presented a detailed study of the alkylation of toluene using propylene as the form of alkene in presence of highly dispersed sodium or potassium or lithium metal and various activators such as anthracene, fluorene, indene, cyclopentadiene, α-methyl pyridine and the like as the chain initiator and shown that the alkylation of alpha carbon atom takes place at 149 to 307o C.

Schramm and Langlois also presented a detailed study of the alkali metals on the yield of byproducts, particularly isomers due to non-selective addition at the double bond at a wide range of temperatures. They observed lower product to isomer ratio over a temperature range of 107o C to 204oC in the presence of potassium as the catalyst. Whereas, when sodium was used instead of potassium the product to isomer ratio was large. Also, they have shown in data that in presence of potassium the rate of product formation is higher than in presence of sodium as the catalyst.

Herman Pines and Norman C. Sih, (J. Org. Chem., 1965, 30(1), pp 280-284) presented a detailed study of alkylation of toluene, ethyl benzene and isopropyl benzene using isoprene as the form of alkene in presence of highly dispersed sodium or potassium metal and o-chlorotoluene as a chain initiator and shown that the alkylation of alpha carbon atom takes place at 125 to 133o C in the presence of initiator like o-chlorotoluene.

Also, in a current industrial practice, higher amounts of catalyst like potassium metal and sodium metal alloy is used in the pre-alkylation stage that gets destroyed by putting water or alcohol at the end of the cycle.

Accordingly, there is a need to provide a process for preparation of n-propyl benzene that overcomes the drawbacks of the prior art.

Objects of the invention

An object of the present invention is to use initiators that improve selectivity of starting aromatic hydrocarbons towards a desired product.

Another object of the present invention is to facilitate reuse of a metal catalyst and higher alkylated products.

Yet another object of the present invention is to recycle a byproduct thereby increasing selectivity towards the desired product.

Summary of the invention

Accordingly, the present invention provides a process for preparation of n-propyl benzene. The process involves adding aromatic hydrocarbon having an active hydrogen on a saturated α-carbon and a solid support to a first reactor to form a mixture. Further, the process involves adding alkali metal catalyst and oleic acid to the mixture to form a reaction mass and closing and agitating the first reactor for a predefined period of time. The alkali metal catalyst is selected from sodium, lithium and combination thereof. Furthermore, the process involves flushing nitrogen gas to the first reactor and heating the reaction mass at a temperature in a range of about 185 to 1900 C for about 15 minutes. Moreover, the process involves adding aromatic hydrocarbon and initiator to a second reactor. The initiator is selected from any one of di-ter-butyl peroxide, azo-iso-bis butyronitrile and iso-amyl nitrite. The initiator is used in a range of 50 to 100 ppm in single stage or in multiple stages.

The second reactor is then flushed with nitrogen gas and contents of the second reactor are kept under stirring for a predefined period of time. Then, the second reactor via a bottom liquid discharge valve thereof is connected to the first reactor.

Further, the process involves adding alkene for example, ethylene to the first reactor to form a reaction mixture. Furthermore, the process involves adding small amount of initiator to the first reactor periodically and maintaining the reaction mixture at a temperature in a range of about 180 to 220oC for longer than 1 hour to 5 hours while agitating the reaction mixture at about 35 to 40 kg/cm2. Moreover, the process involves adding desired amount of methanol and water to the reaction mixture. Further, the process involves separating an aqueous phase for recovery of the catalyst, catalyst support and un-reacted toluene and an organic phase for obtaining n-propyl benzene and byproduct. Furthermore, the process involves analyzing and purifying the organic phase to obtain n-propyl benzene.

Moreover, the process involves recovering from the reaction mixture un-reacted aromatic hydrocarbon having the active hydrogen on the saturated α-carbon and using at least a portion of the recovered un-reacted hydrocarbon in the preparation of n-propyl benzene.

Brief description of the drawing

Figure 1 shows a flowchart illustrating a process for preparation of n-propyl benzene, in accordance with the present invention.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a process for preparation of n-propyl benzene. The process gives high selectivity and yield of n-propyl benzene by single step catalytic alkylation that involves contacting a mixture of toluene and ethylene over an alkali metal like litium or sodium and alkali metal carboxylate like potassium carbonate in presence of initiators/promoters like di-ter-butyl peroxide (DTBP), azo-iso-bis butyronitrile (AIBN) and iso-amyl nitrite.

The present invention provides a process (200) for preparation of n-propyl benzene.
The process (200) is illustrated in figure 1. The process (200) starts at step (10). At step (20), the process (200) involves adding aromatic hydrocarbon and a solid support to a first reactor (not shown) to form a mixture. In an embodiment, the aromatic hydrocarbon includes an active hydrogen on a saturated α-carbon for example toluene. The solid support is an alkali metal carboxylate for example, potassium carbonate powder that acts as a medium for spreading an alkali metal catalyst thereon.

At step (30), the process (200) involves adding alkali metal catalyst and oleic acid as a dispersing agent to the mixture to form a reaction mass. The alkali metal catalyst is selected from sodium, lithium and combination thereof. In an embodiment, molten sodium metal or lithium metal is used and coated on the solid support. After addition of the alkali metal catalyst and oleic acid, the first reactor is closed and agitated for a time period of about 30 minutes to 1 hour.

At step (40), the process (200) involves flushing nitrogen gas to the first reactor for creating inertness therein. At step (50), the process (200) involves heating the reaction mass at a temperature in a range of about 185 to 1900C for about 15 minutes.

At step (60), the process (200) involves adding aromatic hydrocarbon and an initiator to a second reactor (not shown). In an embodiment, aromatic hydrocarbon is toluene. The initiator is selected from di-ter-butyl peroxide, azo-iso-bis butyronitrile, iso-amyl nitrite and combination thereof. The nitrogen gas is then flushed inside the second reactor and the contents of the second reactor are kept under stirring for a time period of about 15 minutes to 30 minutes. Then, a bottom liquid discharge valve (not shown) of the second reactor is connected to the first reactor.

At step (70), the process (200) involves adding alkene to the first reactor to form a reaction mixture. In an embodiment, a preferred alkene is ethylene.

At step (80), the process (200) involves adding small amount of the initiator to the first reactor periodically. The reaction is continued till a desired consumption of ethylene is observed. The reaction mixture is maintained at a temperature in a range of about 180 to 220oC for longer than 1 hour to 5 hours while agitating the reaction mixture at about 35 to 40 kg/cm2. Once the desired consumption of ethylene is observed, the reaction mixture is cooled to room temperature.
At step (90), the process (200) involves adding desired amount of methanol and water to the reaction mixture. The reaction mixture is then taken out of the first reactor.

At step (100), the process (200) involves separating an aqueous phase and an organic phase from the reaction mixture. The aqueous phase is separated for recovery of the catalyst, catalyst support and un-reacted toluene and the organic phase is separated for obtaining n-propyl benzene and byproduct. At step (110), the process (200) involves analyzing the organic phase. In an embodiment, the organic phase is analyzed by gas chromatography (hereinafter “the GC”). The purity of n-propyl benzene is found to be 99.82% by the GC analysis. The process (200) ends at step (120).

The process (200) facilitates recovery of aromatic hydrocarbon, alkali metal catalyst and byproduct. The process (200) utilizes different kinds of initiators such as di-tert-butyl peroxide (DTBP), azo-iso-bis-butyronitrile (AIBN) and iso-amyl-nitrite. The initiators are used as intermittent charging in to the reaction mass. In accordance with the present invention, in the process (200) for preparation of n-propyl benzene, 3-pentyl benzene is formed as the byproduct. Most of the chemical reactions are equilibrium controlled and the formation of the byproduct also is equilibrium controlled. In addition, in the process (200) few experiments are carried out wherein 3-pentyl benzene along with toluene are charged deliberately in the reaction system that resulted in increase in selectivity of the process (200) towards n-propyl benzene.

As an embodiment of the process (200), among the products which can be synthesized more efficiently using alkyl benzenes such as iso-butyl benzene prepared in accordance with this invention are members of the family of compounds which comprise the 2-aryl propionic acid derivatives. Specially, ibuprofen, a commercially successful, over-the-counter analgesic can be synthesized using isobutyl benzene prepared as a raw material. Similarly, an embodiment of this invention, among the products which can be synthesized more efficiently using alkyl benzenes such as 3-isobutyl-toluene and sec-butyl benzene starting from m-xylene-propylene and ethylbenzene-ethylene respectively.

The invention is further illustrated hereinafter by means of examples.

Example 1: Preparation of n-propyl benzene using potassium carbonate as the solid support for sodium catalyst without initiator (control experiment)

The first reactor is a 2 liter capacity high pressure stirred reactor. To the first reactor, dry toluene, dry potassium carbonate, sodium metal catalyst and oleic acid as the dispersing agent were added. The first reactor was then closed and the agitation of the first reactor was started. The first reactor was flushed with nitrogen gas. Then the reaction mass was heated for 15 minutes at a temperature in a range of about 185 to 190oC to activate the catalyst.

Meantime a small amount of dry toluene was taken in the second reactor. The second reactor is a 500-ml capacity stirred high pressure reactor. The nitrogen was flushed to the contents of the second reactor and kept under stirring. The bottom liquid discharge valve of the second reactor was connected to the first reactor and vents of both the reactors were connected.

Once the desired reaction temperature of the first reactor was attained, desired amount of ethylene was added to the first reactor with the help of ethylene cylinder. The addition of ethylene caused the pressure of the first reactor to rise initially and subside slowly as the ethylene consumption took place. The reaction was continued till desired consumption of ethylene was observed and then the reaction mass was cooled to room temperature. To the reaction mass, desired amount of methanol followed by water was added. The reaction mixture was taken out of the first reactor and a lower aqueous phase and an upper organic phase was separated. The organic phase was analyzed using the GC. The GC make used is Shimadzu-17 A, Column used is DB Petro 100 m length (ID 0.25 mm, film thickness 0.5 micron), FID detector, Injector temperature 250oC, Detector temperature 260o C, Initial temperature 80o C, hold time 2 minutes, heating rate 4oC/min, final temperature 250oC for 30 minutes, nitrogen flow rate 1.4 ml/min., split ratio 1:80. The results of the various examples are as shown in the following Table-1.

Table-1 show examples-1.1 and 1.2 using potassium carbonate as catalyst support
Example Number Example-1.1 Example-1.2
Charge to 2-L Reactor
Dry toluene, gm 922 920
Ethylene Gas
Lot-1, gm 98 70
Lot-2, gm 43 70
Potassium carbonate, gm 78 78
Sodium metal, gm 9.2 9.2
Oleic acid, gm 2.5 2.5
Methanol, gm 32 32
Water, gm 600 600
Charge to 500-ml Reactor
Dry toluene 0 184
Process conditions
Maximum reaction temp., o C 180.9 210.1
Maximum reaction press., kg/cm2 30.7 44.8
Final reaction press., kg/cm2 7.6 9.5
Reaction time in hr 4.5 5
Output of reaction mass
Wt. of organic layer, gm 904 1181
Wt of aqueous layer, gm 698 694
Analysis, wt%
Hexenes, wt% 0.085 0
Toluene, wt% 80.889 61.453
n-Propyl Benzene (NPB), wt% 15.891 23.821
3-PP (**) and Heavies, wt% 2.997 14.726
Reaction performance
Toluene to Ethylene mol ratio 1.99 2.40
Quantity of NPB, gm 143.65 281.33
Selectivity based on toluene, % 57.76 57.02
Toluene per pass conversion, % 20.68 34.26
NPB to 3-PP & Heavies ratio 5.3 1.62

Example 2: Preparation of n-propyl benzene using potassium carbonate as the solid support for sodium catalyst and the initiator

The first reactor is a 2 liter capacity high pressure stirred reactor. To the first reactor, dry toluene, dry potassium carbonate, sodium metal catalyst and oleic acid as the dispersing agent was added. The first reactor was then closed and the agitation of the first reactor was started. The first reactor was flushed with nitrogen gas. Then the reaction mass was heated for 15 minutes at temperature in a range of about 185 to 190oC to activate the catalyst.

Meantime about 184 gm of dry toluene was taken in the second reactor and 50 to 100 ppm of di-ter-butyl peroxide (DTBP) as the initiator was added therein. The second reactor is a 500-ml capacity stirred high pressure reactor. The nitrogen was flushed to the contents of the second reactor and kept under stirring. The bottom liquid discharge valve of the second reactor was connected to the first reactor and vents of both the reactors were connected.

Once the desired reaction temperature of the first reactor was attained, desired amount of ethylene was added to the first reactor with the help of ethylene cylinder. The addition of ethylene caused the pressure of the first reactor to rise initially and subside slowly as the ethylene consumption took place. The reaction was continued till desired consumption of ethylene was observed and then the reaction mass was cooled to room temperature. To the reaction mass, desired amount of methanol followed by water was added. The reaction mixture was taken out of the first reactor and a lower aqueous phase and an upper organic phase was separated. The organic phase was analyzed using the GC as mentioned under example 1. The details and the results of the examples 2.1 to 2.8 are shown in the following Table-2.

Table-2 show examples-2.1 to 2.8 using potassium carbonate as catalyst support with DTBP as the initiator

Example Number Example-2.1 Example-2.2 Example-2.3 Example-2.4
Charge to 2-L Reactor
Dry toluene, gm 922 922 922 922
Ethylene Gas
Lot-1, gm 70 140 140 90
Lot-2, gm 70 10
Potassium carbonate, gm 78 78 78 78
Sodium metal, gm 8.7 9.2 9.2 9.2
Oleic acid, gm 2.5 2.5 2.5 2.5
Methanol, gm 32 32 32 32
Water, gm 600 600 600 600
Charge to 500-ml Reactor
Dry toluene 184 184 184 184
Initiator, DTBP (*), mg 60 120 60 60
Process conditions
Maximum reaction temp., o C 182.2 185.5 190.8 190.6
Maximum reaction press., kg/cm2 36.6 32.2 37.8 33
Final reaction press., kg/cm2 11.3 7.6 9.3 12.1
Reaction time in hr 2.45 3 3 3.25
Output of reaction mass
Wt. of organic layer, gm 1106 1115 1149 1117
Wt of aqueous layer, gm 707 702 718 703
Analysis, wt%
Hexenes, wt% 0.12 0.077 0.025 0.1037
Toluene, wt% 73.86 78.346 55.97 72.6199
n-Propyl Benzene (NPB), wt% 21.2 17.327 32.91 20.6993
3-PP (**) and Heavies, wt% 4.41 4.014 10.966 6.42
Reaction performance
Toluene to Ethylene mol ratio 2.40 2.40 2.40 3.36
Quantity of NPB, gm 234.47 193.20 378.14 231.21
Selectivity based on toluene, % 62.61 64.28 62.9 60.53
Toluene per pass conversion, % 26.01 20.87 41.75 26.52
NPB to 3-PP & Heavies ratio 4.81 4.32 3.01 3.22
(*) DTBP-Di-tert-butyl peroxide (**) 3-Phenyl pentane
Table-2 Continued …
Example Number Example-2.5 Example-2.6 Example-2.7 Example-2.8
Charge to 2-L Reactor
Dry toluene, gm 920 920 920 920
Ethylene Gas
Lot-1, gm 45 140 50 45
Lot-2, gm 48 75 48
Potassium carbonate, gm 78 78 78 78
Sodium metal, gm 8.7 9.2 9.2 9.2
Oleic acid, gm 2.5 2.5 2.5 2.5
Methanol, gm 32 32 32 32
Water, gm 600 600 600 600
Charge to 500-ml Reactor
Dry toluene 184 184 184 184
Initiator, DTBP (*), mg 120 65 62 60
Process conditions
Maximum reaction temp., o C 190.1 195.34 195.4 192.4
Maximum reaction press., kg/cm2 18.6 31.8 34.2 38.7
Final reaction press., kg/cm2 8.7 9.2 11.8 10.3
Reaction time in hr 3 3.5 3.25 3.5
Output of reaction mass
Wt. of organic layer, gm 1109 1134 1143.2 1107
Wt of aqueous layer, gm 699 698 702 545
Analysis, wt%
Hexenes 0.086 0.076 0.0863 0.3792
Toluene 80.7862 63.93 62.5214 62.975
n-Propyl Benzene (NPB) 15.5083 24.6894 25.364 24.87
3-PP (**) and Heavies 3.4307 11.1819 11.898 11.62
Reaction performance
Toluene to Ethylene mol ratio 3.61 2.40 2.69 3.61
Quantity of NPB, gm 171.99 279.98 289.96 275.31
Selectivity based on toluene 63.37 56.63 57.11 51.88
Toluene per pass conversion 18.85 34.33 35.26 36.85
NPB to 3-PP & Heavies ratio 4.52 2.21 2.13 2.14
(*) DTBP-Di-tert-butyl peroxide (**) 3-PP- 3-Phenyl pentane

Example 3: Preparation of n-propyl benzene using potassium carbonate as the solid support for sodium catalyst with the initiator

In this example, preparation of n-propyl benzene was carried out using potassium carbonate as the solid support, sodium as the metal catalyst and azo-iso-bis butyronitrile (AIBN) as the initiator. The steps of the process (200) are similar as mentioned in example 2 and the same are not again described herein for the sake of the brevity of the invention. The details and the results of the examples 3.1-3.3 are shown in the following Table-3.

Table-3 show examples-3.1 to 3.3 using potassium carbonate as catalyst support with AIBN as the initiator

Example Number Example-3.1 Example-3.2 Example-3.3
Charge to 2-L Reactor
Dry toluene, gm 920 920 920
Ethylene Gas
Lot-1, gm 135 120 165
Lot-2, gm
Potassium carbonate, gm 78 78 78
Sodium metal, gm 9,2 9,2 9,2
Oleic acid, gm 2.7 2.7 2.7
Methanol, gm 32 30 30
Water, gm 604 600 600
Charge to 500-ml Reactor
Dry toluene 184 184 184
Initiator, AIBN (*), mg 64 60 60
Process conditions
Maximum reaction temp., o C 221.8 190.8 195.2
Maximum reaction press., kg/cm2 53.4 37.4 46.3
Final reaction press., kg/cm2 16.4 19.9 13.2
Reaction time in hr 3.5 4.25 4.25
Output of reaction mass
Wt. of organic layer, gm 1198 1118 1190
Wt of aqueous layer, gm 707 698 701
Analysis, wt%
Hexenes, wt% 0.1849 0.2191 0.0808
Toluene, wt% 54.5393 69.9528 55.2322
n-Propyl Benzene (NPB), wt% 27.9853 21.6334 28.274
3-PP (**) and Heavies, wt% 16.981 8.0656 16.2886
Reaction performance
Toluene to Ethylene mol ratio 2.49 2.80 2.04
Quantity of NPB, gm 335.26 241.86 336.46
Selectivity based on toluene, % 57.04 57.60 57.74
Toluene per pass conversion, % 40.82 29.16 40.47
NPB to 3-PP & Heavies ratio 1.65 2.68 1.74
(*) AIBN-Azo-Iso-bis Butyro Nitrile (**) 3-Phenyl pentane

Example 4: Preparation of n-propyl benzene using potassium carbonate as the solid support for sodium catalyst with the initiator

In this example, preparation of n-propyl benzene was carried out using potassium carbonate as the solid support, sodium as the metal catalyst and iso-amyl nitrite as the initiator. The steps of the process (200) are similar as mentioned in example 2 and the same are not again described herein for the sake of the brevity of the invention. The details and the results of the examples 4.1-4.3 are shown in the following Table-4.

Table-4 show examples-4.1 to 4.3 using potassium carbonate as catalyst support with iso-amyl nitrite as the initiator
Example Number Example-4.1 Example-4.2 Example-4.3
Charge to 2-L Reactor
Dry toluene, gm 920 920 920
Ethylene Gas
Lot-1, gm 95 127 127
Lot-2, gm
Potassium carbonate, gm 78 78 78
Sodium metal, gm 9.3 9.18 9.18
Oleic acid, gm 2.5 2.5 2.5
Methanol, gm 32 32 32
Water, gm 604 600 600
Charge to 500-ml Reactor
Dry toluene 184 184 184
Initiator, iso-Amyl Nitrite, mg 120 64 64
Process conditions
Maximum reaction temp., o C 195.5 195.1 195.1
Maximum reaction press., kg/cm2 39 43 43
Final reaction press., kg/cm2 12 19 19
Reaction time in hr 4.5 4.25 4.5
Output of reaction mass
Wt. of organic layer, gm 1009 1106 1106
Wt of aqueous layer, gm 721 708 698
Analysis, wt%
Hexenes, wt% 0.0735 0.1106 0.1106
Toluene, wt% 74.038 70.324 70.324
n-Propyl Benzene (NPB), wt% 18.292 19.127 19.127
3-PP (**) and Heavies, wt% 7.542 10.3868 10.3868
Reaction performance
Toluene to Ethylene mol ratio 3.54 2.65 2.65
Quantity of NPB, gm 184.57 211.54 211.54
Selectivity based on toluene, % 39.64 49.72 49.72
Toluene per pass conversion, % 32.33 29.55 29.55
NPB to 3-PP & Heavies ratio 2.43 1.84 1.84
(**) 3-Phenyl pentane

Example 5: Preparation of n-propyl benzene using potassium carbonate as the solid support for lithium metal catalyst with initiator

In this example, preparation of n-propyl benzene was carried out using potassium carbonate as the solid support, lithium as the metal catalyst and di-ter-butyl peroxide (DTBP) as the initiator. The steps of the process (200) are similar as mentioned in example 2 except the temperature range of 190 to 200oC and the same are not again described herein for the sake of the brevity of the invention. The details and the results of the examples 5.1 and the control experiment (without initiator) are shown in the following Table-5.

Table-5 show example-5.1 and control example using potassium carbonate as catalyst support with lithium metal as the catalyst and DTBP as the initiator

Example Number Example-5.1 Control Example
Charge to 2-L Reactor
Dry toluene, gm 920 920
Ethylene Gas
Lot-1, gm 70 70
Lot-2, gm 70 70
Potassium carbonate, gm 78 78
Sodium metal, gm 0 9.2
Lithium metal, gm 3 0
Oleic acid, gm 2.5 2.5
Methanol, gm 32 32
Water, gm 600 600
Charge to 500-ml Reactor
Dry toluene 184 184
Initiator, DTBP, mg (*) 225 0
Process conditions
Maximum reaction temp., o C 215.2 210.1
Maximum reaction press., kg/cm2 39 44.8
Final reaction press., kg/cm2 21 9.5
Reaction time in hr 8.5 5
Output of reaction mass
Wt. of organic layer, gm 1178 1181
Wt of aqueous layer, gm 708 694
Analysis, wt%
Hexenes, wt% 0 0
Toluene, wt% 63.863 61.453
n-Propyl Benzene (NPB), wt% 26.061 23.821
3-PP (**) and Heavies, wt% 9.802 14.726
Reaction performance
Toluene to Ethylene mol ratio 2.40 2.40
Quantity of NPB, gm 307 281.33
Selectivity based on toluene, % 66.92 57.02
Toluene per pass conversion, % 31.86 34.26
NPB to 3-PP & Heavies ratio 2.66 1.62
(*) DTBP-Di-tert-butyl peroxide (**) 3-PP- 3-Phenyl pentane

Examples 6 and 7: Preparation of n-propyl benzene using potassium carbonate as the solid support for sodium metal catalyst and recycling of the alkali metal catalyst along with part recycle of 3-phenyl pentane

In this example, preparation of n-propyl benzene was carried out using potassium carbonate as the solid support, sodium as the metal catalyst and di-ter-butyl peroxide (DTBP) as the initiator. The steps of the process (200) are similar as mentioned in example 2 and the same are not again described herein for the sake of the brevity of the invention. The reaction mixture was siphon out of the first reactor under pressure so that only liquid phase is transferred. The liquid phase was used for collection of residual catalyst, potassium carbonate and un-reacted toluene while the remaining organic phase was used for collection of 3-phenyl pentane. The residual catalyst and potassium carbonate so collected were then continuously recycled for at least 10-15 times in next preparation cycle of n-propyl benzene.
The details and the results of the examples 6.1 -6.5 for recycling of the alkali metal catalyst are shown in the following Table-6. The details and the results of the examples 7.1 -7.2 for recycle of the catalyst and part recycle of 3-phenyl pentane are shown in the following Table-7.

Table-6 show examples-6.1 to 6.5 using potassium carbonate as catalyst support with sodium metal as the catalyst and recycle of the alkali metal catalyst

Example Number Example-6.1 Example-6.2 Example-6.3 Example-6.4 Example-6.5
Remarks Fresh Cycle Catalyst Recycle-1 Catalyst Recycle-2 Catalyst Recycle-3 Catalyst Recycle-4
Charge to 2-L Reactor
Dry toluene, gm 806 802 962 1010 1206
Initiator, DTBP, mg (*) 80 80 90 100 120
Ethylene Gas
Lot-1, gm 180 165 154 158 138
Lot-2, gm 0 0 0 0 0
Potassium carbonate, gm 146 0 0 0 0
Sodium metal, gm 14.76 10.312 10.428 10.218 8.342
Oleic acid, gm 3.8 3 3 3.5 2.5
Methanol, gm 0 0 0 0 501
Water, gm 422 425 450 501 508
Process conditions
Maximum reaction temp., o C 228.5 211.2 212.3 216.1 208.2
Maximum reaction press., kg/cm2 43 41 40 40 34
Final reaction press., kg/cm2 8 7 6 7 7
Reaction time in hr 2 1.15 1.45 1 1
Output of reaction mass
Wt. of organic layer, gm 778 942 1037 1195 1396
Wt of aqueous layer, gm 422 434 459 505 1038
Analysis, wt%
Toluene, wt% 42.580 39.721 48.625 50.613 62.294
n-Propyl Benzene (NPB), wt% 35.444 37.305 35.852 36.508 20.580
3-PP (**) 19.909 20.846 13.820 11.150 6.001
Heavies, wt% 2.067 2.128 1.703 1.730 11.125
Reaction performance
Toluene to Ethylene mol ratio 1.39 1.36 1.48 1.90 1.95
Quantity of NPB, gm 275.75 351.41 371.79 436.27 287.30
Selectivity based on toluene, % 44.53 62.97 62.27 82.55 65.48
Toluene per pass conversion, % 58.90 53.35 47.58 40.12 27.89
NPB to 3-PP ratio 1.78 1.79 2.59 3.27 3.43
NPB to Heavies ratio 17.15 17.53 21.05 21.11 1.85
(*) DTBP-Di-tert-butyl peroxide (**) 3-Phenyl pentane

Table-7 show examples-7.1 and 7.2 using potassium carbonate as catalyst support with sodium metal as the catalyst, recycle of the catalyst and part recycle of 3-phenyl pentane

Example Number Example-7.1 Example-7.2
Remarks Fresh Cycle Catalyst Recycle-1
Charge to 2-L Reactor
Dry toluene, gm 774.97 781.74
Initiator, DTBP, mg (*) 80 80
3-PP (**) 26.03 26.26
Ethylene Gas
Lot-1, gm 145 135
Lot-2, gm
Potassium carbonate, gm 145 0
Sodium metal, gm 14.766 10.256
Oleic acid, gm 3.6 3
Methanol, gm 0 0
Water, gm 395 670
Process conditions
Maximum reaction temp., o C 200.1 200.4
Maximum reaction press., kg/cm2 40 39
Final reaction press., kg/cm2 8 8
Reaction time in hr 1.5 1.5
Output of reaction mass
Wt. of organic layer, gm 784 1020
Wt of aqueous layer, gm 398 832
Analysis, wt%
Toluene, wt% 49.127 49.509
n-Propyl Benzene (NPB), wt% 33.867 33.214
3-PP (**) 14.159 14.948
Heavies, wt% 2.847 2.330
Reaction performance
Toluene to Ethylene mol ratio 1.63 1.76
Quantity of NPB, gm 265.52 338.78
Selectivity based on toluene, % 51.17 91.19
Toluene per pass conversion, % 50.81 36.06
NPB to 3-PP ratio 3.27 2.76
NPB to Heavies ratio 11.90 14.25
(*) DTBP-Di-tert-butyl peroxide (**) 3-Phenyl pentane

Example 8: Purification of n-propyl benzene

An atmospheric pressure fractional distillation assembly was used for the purification of n-propyl benzene. The fractional distillation assembly consists of 10 L capacity stirred jacketed distillation still having 50 mm diameter and 1500 mm height packed distillation column, reflux condenser, distillate receiver, top and bottom temperature indicators and the like. 10 kg crude n-propyl benzene obtained from any of the examples 1 to 7 was added to the fractional distillation assembly. The crude material under stirring was heated with the help of hot oil circulator. Toluene was recovered till the top temperature reaches to 110 to 125o C whereas the bottom temperature reaches to 150 to 155o C with the reflux ratio ‘2’. The recovered toluene was recycled in next n-propyl benzene synthesis run. Pure n-propyl benzene was collected at the top temperature of 165 to 170o C and the bottom temperature of 180 to 190o C. During n-propyl benzene collection reflux ratio of 3 to 4 was maintained. All the distillation cuts, distillation residue were analyzed using the GC as mentioned under examples 1 and 2. The purity of n-propyl benzene cut was found to be 99.82% by GC analysis.

Advantages of the invention

1. The process (200) facilitates reuse of higher alkylated product such as 3-phenyl pentane, alkali metal catalyst and the solid support that improves the selectivity and reduces the effluent load and thus the waste disposal and hence is economically and commercially attractive.
2. The initiators being aprotic in nature are required in very small amount and improve the selectivity of starting alkyl benzene towards the desired product.
3. The process (200) is less hazardous since the dry reagents are used and water is not used in a reaction zone.
4. The potassium carbonate powder improves distribution of catalyst by offering a large amount of surface area for spreading the metal catalyst thereon thereby allowing a large mass transfer area for the reaction.
5. The potassium carbonate powder improves the contact area between the alkali metal catalyst and the alkyl benzene thereby improves the mixing and ensures the availability of the alkali metal catalyst throughout the first reactor.
6. As compared to potassium, sodium and lithium are easily available, less hazardous to handle and used in lesser amounts due to lower/lesser atomic weights.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.