DESC:Field of the Invention

The present invention relates to a process for production of branched alcohol.

Background of the Invention

The currently known processes for production of C6 or C8 branched alcohol involve formation of certain unwanted unsaturated aldehydes, other by-products such as high boiling oils, complex unsaturated compounds, and large amount of acetaldehyde.

Therefore, there is a need to provide a process for the process for production of a branched alcohol from aldol, which is safe, economic and cost-effective.

Summary of the Invention

The instant invention is related to a process for production of a branched alcohol from one or more aldehyde and/or aldol. First, an aldol is reacted with an aldehyde in presence of catalyst to generate an aldol at a temperature in a range of 15°-60°C. Alternatively, the aldol or aldehyde is subjected to self-condensation reaction or different aldehydes are reacted in presence of a catalyst to form an aldol. The aldol generated in the above process is dehydrated at a temperature in a range of 110°C-140°C to form an unsaturated aldehyde, which after distillation, is hydrogenated catalytically at a temperature in a range of 120?-130°C to produce the branched alcohol.

Description of the Invention

The present invention discloses a safe, economic and cost-effective process for production of a branched alcohol.

The invention discloses a process for production of a branched alcohol. An aldol is generated in presence of a catalyst at a temperature in a range of 15?-60°C by reacting an aldol with an aldehyde, or by self-condensation of aldol or aldehyde or by reacting two different aldehydes. The aldol prepared in the above step is dehydrated at a temperature of 110?-140°C to obtain an unsaturated aldehyde followed by distillation. The unsaturated aldehyde is hydrogenated in presence of a catalyst at a temperature of 120?-130°C to obtain the branched alcohol.

In an aspect of the invention, an aldol is generated in presence of a catalyst at a temperature in a range of 15?-60°C by reacting an aldol with an aldehyde. The aldol thus obtained is dehydrated at a temperature in a range of 110?-140°C to form an unsaturated aldehyde. The unsaturated aldehyde is then subjected to distillation. The unsaturated aldehyde thus obtained after distillation, is hydrogenated at a temperature in a range of 120?-130°C in the presence of a catalyst to produce the branched alcohol.

In another aspect of the invention, an aldol is generated in presence of a catalyst at a temperature in a range of 15?-60°C by self-condensation of an aldol or an aldehyde. The aldol thus obtained is dehydrated at a temperature in the range of 110?-140°C to form an unsaturated aldehyde. The unsaturated aldehyde is then subjected to distillation. The unsaturated aldehyde thus obtained after distillation, is hydrogenated at a temperature in the range of 120?-130°C in the presence of a catalyst to produce the branched alcohol.

In another aspect of the invention, an aldol is generated in presence of a catalyst at a temperature in a range of 15?-60°C by reaction of two different aldehydes. The aldol thus obtained is dehydrated at a temperature in the range of 110?-140°C to form an unsaturated aldehyde. The unsaturated aldehyde is then subjected to distillation. The unsaturated aldehyde thus obtained after distillation, is hydrogenated at a temperature in the range of 120?-130°C in the presence of a catalyst to produce the branched alcohol.

The aldehyde is selected from acetaldehyde, butyraldehyde, crotonaldehyde or mixtures thereof, and the aldol is acetaldol.

The catalyst for the aldol generation reaction is selected from alkali, anion exchange resin or supported alkaline catalyst. The alkali is selected from sodium hydroxide (NaOH), sodium carbonate or potassium hydroxide. The aldol generation is carried out at an alkaline pH, preferably in a range of 9 to 11.5, and at a temperature in a range of 15?-60 ? or 18°C-22°C or 50°C-60°C.

The dehydration reaction is carried out at a temperature in the range of 110-140 ?.

The hydrogenation step is carried out in presence of a catalyst selected from nickel, palladium or supported palladium.

An embodiment of the present invention provides a process for production of a branched alcohol such as C6 or C8 branched alcohol from C4 and C6 aldol.

The process comprises steps of reacting an aldehyde with C4 aldol in the presence of a catalyst to form a C6 aldol compound. The aldehydes are acetaldehyde, butyraldehyde, crotonaldehyde or mixtures thereof. The aldol is dehydrated to produce an unsaturated C6 aldehyde (as per the selected reactants), which is further hydrogenated in the presence of a catalyst to produce C6 branched alcohol.

Another aspect of the present invention comprises reacting an aldehyde with C6 aldol compound. The aldehydes are acetaldehyde, butyraldehyde crotonaldehyde or mixtures thereof. The aldol is dehydrated to produce an unsaturated C8 aldehyde (as per the selected reactants), which is further hydrogenated in the presence of a catalyst to produce C8 branched alcohol.

Yet another aspect of the invention comprises self-condensation of C4 aldol (d) in the presence of a catalyst to form C8 aldol (e), further heating or dehydrating the C8 aldol to form C8 unsaturated aldehyde (f), which on hydrogenation gives C8 branched alcohol (g).

The reaction scheme is shown below:

Scheme I:

Yet another aspect of the invention comprises self-condensation of C4 aldehyde in the presence of a catalyst to form C8 aldol, further heating or dehydrating the C8 aldol to form C8 unsaturated aldehyde, which on hydrogenation gives C8 branched alcohol.

The invention also includes a process where the reaction is carried out in excess of acetaldehyde whereby the acetaldol is in situ produced during the reaction and reacts with acetaldehyde to form the C6 aldol.

The unsaturated C6 aldehyde formed in the dehydration step is 2-vinyl crotonaldehyde, 2-ethyl crotonaldehyde or sorbaldehyde (2,4-hexadienal).

The branched C6 alcohol formed after hydrogenation of unsaturated C6 aldehyde is 2-ethyl-1-butanol.

The unsaturated C8 aldehyde formed in the dehydration step is 2-ethyl hexenal.

The branched C8 alcohol formed after hydrogenation of unsaturated C8 aldehyde is 2-ethyl hexanol.

The first step that is reaction between the aldehydes is carried out in the presence of a catalyst such as an alkali, like sodium hydroxide (NaOH), Sodium carbonate, potassium hydroxide, anion exchange resin, supported alkaline catalyst preferably 2% aqueous solution of NaOH at a temperature in a range of 15°C-20°C and an alkaline pH of 9 to 11.5 to produce the C6 and C8 aldol. After the reaction is complete, the aldol is thermally dehydrated for instance in an autoclave (125°C - 130°C) under an inert atmosphere to produce the unsaturated C6 or C8 aldehyde.

The reaction mixture is subjected to distillation to separate the unsaturated aldehyde which is then hydrogenated in presence of a hydrogenation catalyst such as nickel, palladium or supported palladium to produce C6 or C8 branched alcohol.

The process of the present invention results in improved yield of the branched alcohol as the major product. The process also results in improved purity of the branched alcohol as the overall selectivity of the four carbon straight chain aldehyde towards the branched alcohol is increased. The process does not result in acetaldehyde and high boiling point oils as major by-products.

In another aspect, the present invention includes a process for producing a C6 branched alcohol, 2-ethyl-1-butanol. The process comprises steps of reacting acetaldehyde with acetaldol in the presence of a catalyst to form C6 aldol (a), dehydrating the aldol (a) to produce 2-vinyl crotonaldehyde (b) and other unsaturated aldehydes, and hydrogenating 2-vinyl crotonaldehyde (b) and other unsaturated aldehydes in the presence of a catalyst to produce 2-ethyl-1-butanol (c).

The reaction scheme is shown below:

Scheme II

The process is carried out in excess of acetaldehyde.

The reaction between the aldehydes is carried out in the presence of an alkali such as sodium hydroxide (NaOH), preferably 2% aqueous solution of NaOH, as the catalyst at a temperature in range of 15?-20°C and an alkaline pH of 11 to 11.5 to produce a C6 aldol (a). The reaction is carried out preferably for 8 minutes and after the reaction is complete, the reaction mixture is neutralized, the aldol (a) is thermally dehydrated for instance in an autoclave (125°C -140°C) under inert atmosphere to produce 2-vinyl crotonaldehyde (b) and other unsaturated aldehydes that are hydrogenated in the presence of a hydrogenation catalyst to 2-ethyl-1-butanol (c).

The process further includes a step of separation and purification of 2-ethyl-1-butanol (c) by distillation preferably fractional distillation.

In an embodiment, acetaldehyde and butyraldehyde are reacted in the presence of sodium hydroxide (NaOH) as the catalyst at a temperature in range of 15?-20°C and an alkaline pH of 9 to 11.5 to produce an aldol. The reaction is carried out preferably for 8 hours and after the reaction is complete the aldol is dehydrated at a temperature in a range of 110°C -140°C followed by distillation to produce 2-ethylcrotonaldehyde and 2-ethylhexenal that are hydrogenated at 120?-130 ? in the presence of nickel catalyst to produce 2-ethyl-1-butanol. Preferably, the reaction is carried in a batch mode.

In another embodiment, the process comprises subjecting acetaldehyde or acetaldol to self-condensation at a temperature in a range of 15?-20°C or 55?-60°C for 8 minutes in presence of sodium hydroxide to form an aldol. This aldol is dehydrated at a temperature in the range of 110?-140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde, which are then hydrogenated in presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol. Preferably, the reaction is carried in a continuous mode.

In yet another embodiment, acetaldehyde is treated with acetaldol at a temperature in a range of 50?-60°C, preferably 55?-60°C for 8 minutes in presence of sodium hydroxide to form an aldol. The aldol is dehydrated at a temperature in a range of 110?-140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde. 2-vinylcrotonaldehyde and sorbaldehyde thus obtained are hydrogenated in presence of nickel at a temperature in the range of 120?-130 ºC to obtain 2-ethyl-1-butanol. Preferably, the reaction is carried in a continuous mode. The reaction temperature of 50?-60°C facilitates less energy and steam requirement.

2-ethyl-1-butanol obtained in the above described processes is further separated by distillation.

In yet another embodiment of the present invention, the process for production of 2-ethyl-1-butanol comprises subjecting acetaldehyde or acetaldol to self-condensation in presence of sodium hydroxide at a temperature in a range of 55?-60°C and a pH of 9-11.5 to form C6 aldol. The C6 aldol is dehydrated at a temperature in a range of 125°C to 140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde. 2-vinyl crotonaldehyde and sorbaldehyde are then hydrogenated in the presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol. 2-ethyl-1-butanol thus obtained is separated by distillation.

The process results in an improved yield and purity of 2-ethyl-1 butanol which is used for preparing of 2-ethylbutyric acid and certain esters which are in demand in the manufacture of plasticizers. Further, small size equipment is required for the process, which allows for easy control of the reaction exotherm, thereby reducing safety hazard. Also, due to the low temperature range required in the processes, the energy and the steam requirement is also very low.

The process of the invention enables high selectivity and high conversion rate to products. The process consistently achieves the overall selectivity of 70 % moles or higher, and the yield of 50 mole % or higher. Further, as the reaction temperatures are lower, the energy and steam requirements are also lower, thereby reducing the operating costs.
Examples

The following examples illustrate the invention but are not limiting thereof.

Example 1:

A 2 Liter RBF having agitator, temperature sensor and online pH meter, was immersed in water bath having chilled water circulation arrangement. 452 gm of acetaldehyde and 370 gm of butyraldehyde was charged into RBF. The charge was mixed while cooling to a temperature of 15 ºC, after which was added from dropping funnel slow stream of 2% aqueous sodium hydroxide solution. The reaction temperature was maintained during reaction to about 20 ? and pH was maintained at 11-11.5 for 8 hours. After neutralization, the aldol was dehydrated in an autoclave at 125 ºC under nitrogen pressure. The unreacted acetaldehyde, butyraldehyde and crotonaldehyde was separated by distillation. The bottom product 2-ethylcrotonaldehyde, 2-ethylhexenal and other unsaturated aldehydes were hydrogenated using nickel catalyst at 120?-130ºC at 20-22 kg/cm2 of hydrogen pressure. After hydrogenation, 2-ethyl-1-butanol with purity of 99% and was separated by distillation, yield was 60 mole%. The overall selectivity of acetaldehyde to 2-ethyl-1-butanol and crotonaldehyde combine was 77 mole%. The overall selectivity of butyraldehyde to 2-ethyl-1-butanol and 2-ethylhexanol was 77 mole% and 81 mole% respectively.

Example 2:

A 2 Liter autoclave having agitator, temperature sensor was equipped with a coil for cooling and a dropping funnel. The equipment was vented through cold trap and inert atmosphere was maintained in reaction. 1000 gm of acetaldehyde was charged into an autoclave and chilled at 15 ºC, after which slow stream of 2% aqueous sodium hydroxide solution was added from dropping funnel and pH was maintained at 11-11.5. The reaction temperature was maintained to about 20 ºC during the reaction to obtain an aldol. Reaction time was eight minutes. After neutralization, the aldol was dehydrated. The unreacted acetaldehyde, crotonaldehyde was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldehyde were hydrogenated using nickel catalyst at 120?-130 ºC at 20-22 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation, yield was 54 mole%. The overall selectivity of acetaldehyde to 2-ethyl-1-butanol and crotonaldehyde was 87 mole%.

Example 3:

In a continuous mode of SS (Stainless Steel) column, below materials were fed:
Acetaldehyde - 600 gm/hr
Acetaldol (40%) – 300 gm/hr
Water – 57 gm/hr
2% NaOH solution – 114 gm/hr
25% Acetic Acid – 11.82 gm/hr

The reaction temperature was maintained to about 50?-55 ºC during the reaction to obtain aldol and pH was maintained at 11-11.5. Reaction time was eight minutes. After neutralization, the aldol was dehydrated at 110-120 ºC. The unreacted acetaldehyde, crotonaldehyde was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldehyde were hydrogenated using nickel catalyst at 120?-130 ºC at 20-22 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation, yield was 65 mole%. The overall selectivity of acetaldehyde to 2-ethyl-1-butanol and crotonaldehyde was 86 mole%.

Example 4:

A 2 Liter autoclave having agitator, temperature sensor was equipped with a coil for cooling and a dropping funnel. The equipment was vented through cold trap and inert atmosphere maintained in reaction. 1000 gm of acetaldol was charged into an autoclave and chilled at 15 ºC, after which slow stream of 2% aqueous sodium hydroxide solution was added from dropping funnel and pH was maintained at 11-11.5. The reaction temperature was maintained to about 20 ºC during the reaction to obtain aldol. Reaction time was eight minutes. After neutralization the aldol was dehydrated. The unreacted acetaldol was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldol were hydrogenated using palladium catalyst at 120?-130 ºC at 20 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation. The overall selectivity of acetaldol to 2-ethyl-1-butanol and crotonaldehyde was 86 mole%.

Example 5:

A 2 Liter autoclave having agitator, temperature sensor was equipped with a coil for cooling and a dropping funnel. The equipment was vented through cold trap and inert atmosphere maintained in reaction. 1000 gm of acetaldehyde was charged into an autoclave and chilled at 18 ºC, after which slow stream of 2% aqueous sodium hydroxide solution was added from dropping funnel and pH was maintained at 11-11.5. The reaction temperature was maintained to about 20 ºC during reaction to obtain aldol. Reaction time was eight minutes. After neutralization the aldol was dehydrated. The unreacted acetaldehyde was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldol were hydrogenated using Raney nickel catalyst at 121 ºC at 22 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation. The overall selectivity of acetaldehyde to 2-ethyl-1-butanol and crotonaldehyde was 85 mole%.

Example 6:

A 2 Liter autoclave having agitator, temperature sensor was equipped with a coil for cooling and a dropping funnel. The equipment was vented through cold trap and inert atmosphere maintained in reaction. 1000 gm of acetaldehyde was charged into an autoclave and chilled at 15 ºC, after which slow stream of 2% aqueous sodium hydroxide solution was added from dropping funnel and pH was maintained at 11-11.5. The reaction temperature was maintained to about 18 ºC during the reaction to obtain aldol. Reaction time was eight minutes. After neutralization the aldol was dehydrated. The unreacted acetaldehyde, crotonaldehyde was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldehyde were hydrogenated using nickel catalyst at 125 ºC at 20-22 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation. The overall selectivity of acetaldehyde to 2-ethyl-1-butanol and crotonaldehyde was 87 mole%.

Example 7:

A 2 Liter autoclave having agitator, temperature sensor was equipped with a coil for cooling and a dropping funnel. The equipment was vented through cold trap and inert atmosphere maintained in reaction. 1000 gm of acetaldol was charged into autoclave and chilled at 15 ºC, after which slow stream of 2% aqueous sodium hydroxide solution was added from dropping funnel and pH was maintained at 11-11.5. The reaction temperature was maintained to about 22 ºC during the reaction to obtain aldol. Reaction time was eight minutes. After neutralization the aldol was dehydrated. The unreacted acetaldol was separated by distillation. The bottom product 2-vinylcrotonaldehyde, sorbaldehyde and other unsaturated aldol were hydrogenated using palladium catalyst at 120-130 ºC at 20 kg/cm2 of hydrogen pressure. After hydrogenation 2-ethyl-1-butanol with purity of 99% was separated by distillation. The overall selectivity of acetaldol to 2-ethyl-1-butanol and crotonaldehyde was 86 mole%.

The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.
,CLAIMS:
1. A process for production of a branched alcohol, the process comprising the steps of:

a. generating an aldol in presence of a catalyst at a temperature in a range of 15?-60°C by reacting an aldol with an aldehyde, or by self-condensation of aldol or aldehyde or by reacting two different aldehydes;

b. dehydrating the aldol compound at a temperature of 110?-140°C to form an unsaturated aldehyde,

c. subjecting the unsaturated aldehyde to distillation; and

d. hydrogenating the unsaturated aldehyde at a temperature of 120?-130°C in the presence of a catalyst to produce the branched alcohol.

2. The process as claimed in claim 1, wherein the aldehyde is selected from acetaldehyde, butyraldehyde or crotonaldehyde or mixtures thereof.

3. The process as claimed in claim 1, wherein the aldol is selected from C4 or C6 aldol.

4. The process as claimed in claim 3, wherein the aldol is acetaldol.

5. The process as claimed in claim 1, wherein the catalyst in step a is selected from alkali, anion exchange resin or supported alkaline catalyst.

6. The process as claimed in claim 5, wherein the alkali is selected from sodium hydroxide (NaOH), sodium carbonate or potassium hydroxide.

7. The process as claimed in claim 1, wherein the step a is carried out at a pH of 9 to 11.5.

8. The process as claimed in claim 1, wherein step a is carried out at a temperature in the range of 18 ? to 22 ?.

9. The process as claimed in claim 1, wherein step a is carried out at a temperature in the range of 50 ? to 60?.

10. The process as claimed in claim 1, wherein hydrogenation in step d is carried out in presence of a catalyst selected from nickel, palladium or supported palladium.

11. The process as claimed in claim 1 comprising:

a. reacting acetaldehyde with butyraldehyde at a temperature in a range of 15?-20°C for 8 hours in presence of sodium hydroxide to form an aldol;

b. dehydrating the aldol at 110?-140°C followed by distillation to obtain 2-ethylcrotonaldehyde and 2-ethylhexenal; and

c. hydrogenating 2-ethylcrotonaldehyde and 2-ethylhexenal in presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol.

12. The process as claimed in claim 1 comprising:

a. subjecting acetaldehyde or acetaldol to self-condensation at a temperature in a range of 15?-20°C for 8 minutes in presence of sodium hydroxide to form an aldol;

b. dehydrating the aldol at 110?-140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde; and

c. hydrogenating 2-vinylcrotonaldehyde and sorbaldehyde in presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol.

13. The process as claimed in claim 1 comprising:

a. reacting acetaldehyde with acetaldol at a temperature in a range of 50?-60°C for 8 minutes in presence of sodium hydroxide to form an aldol;

b. dehydrating the aldol at 110?-140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde; and

c. hydrogenating 2-vinylcrotonaldehyde and sorbaldehyde in presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol.

14. The process as claimed in any one of the claims 1 or 11-13 comprising separating 2-ethyl-1-butanol by distillation.

15. The process as claimed in claim 12 for production of 2-ethyl-1-butanol, the process comprising the steps of

a. subjecting acetaldehyde or acetaldol to self-condensation in presence of sodium hydroxide at a temperature in a range of 55?-60°C for 8 minutes and pH of 9-11.5 to form aldol;

b. dehydrating the aldol at a temperature in a range of 125°C to 140°C followed by distillation to obtain 2-vinylcrotonaldehyde and sorbaldehyde;

c. hydrogenating 2-vinyl crotonaldehyde and sorbaldehyde in the presence of nickel at a temperature of 120?-130 ºC to obtain 2-ethyl-1-butanol; and

d. separating 2-ethyl-1-butanol by distillation.