FIELD OF INVENTION

The present invention relates to an improved process for the synthesis of oxo- alcohols. The invention further relates to synthesis of C3 — C4 oxo-alcohols from corresponding aldehyde with greater selectivity in a single pot using recyclable multifunctional catalyst. The present modified process selectively prepare C3 - C4 oxo-alcohols in single pot which result in simple process, reduction in reaction time, reaction steps and workup and total cost of manufacturing.

BACKGROUND OF INVENTION:

Oxo alcohols are important chemicals, such as ^-butanol and 2-ethyl- 1-hexanol, are used to make acrylic esters, formulate lubricants, diesel additives and in paint and varnish applications, 2-methyl-l-pentanol is used as solvent and intermediate for the manufacturing of other chemicals.

Oxo-alcohols, mainly 2-ethyl- 1-hexanol (2 -EH) is a bulk chemical with production capacity of 2.8 million tons per year. The traditional route involves quantitative conversion of butyraldehyde into 2-ethyl hexenal in the presence of sodium hydroxide or a basic ion-exchanger at 80-100°C. Followed by gas phase hydrogenation to 2-EH at pressure of 5 atm and temperature of 100-150°C with nickel or 135-170°C with copper fixed bed catalysts. Pure product is obtained after three stage distillation.(Kinetic studyofbiphasicaldolcondensationof n- butyraldehyde using stirredcell, ArvindVarma et al, Chemical Engineering Science 104, 2013, pg619-629)

US 3127451, discloses the synthesis of 2-ethylhexanol from olefins such as propylene via the aldox condensation reaction followed by hydrogenation of the resulting aldox aldehydes using sulfactive hydrogenation catalyst at temperatures between about 350° and 400° F. and a pressure of about 3000 psig.

EP 1836148B1, discloses the synthesis of 2-ethylhexanol from n-butanal using catalyst such as hydridocarbonyltris(triphenylphosphine) rhodium(I) impregnated on hydrotalcite. The cost of hydridocarbonyltris(triphenylphosphine) rhodium(I) is very high and hence the overall cost of synthesis process is also high.

The present invention eliminates the drawbacks of the prior art reaction which discloses use of costly catalyst. It deals with synthesis of aoxoalcohols using eco- friendly process and economic catalyst. The basic site of hydrotalcite support along with active metal site of coppermakes it efficient for selective conversion of aldehydes to corresponding oxo-lacohols through catalysing cascade reactions such as aldol condensation and hydrogenationin a single pot. In addition to that the modified process is devoid of any organic solvent and hence it makes the process eco-friendly.

The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

OBJECTIVES OF THE INVENTION

The main objective of the present invention is to provide an improved process for synthesis of oxo-alcohols from corresponding aldehyde.

Another objective of the present invention is toprovide an eco-friendly process for the synthesis of oxo-alcohols in a single pot using .a multifunctional catalyst.

• The present invention also aims to providea simple and economic method for preparation ofoxo-alcohols with greater selectivity and high conversion rate. • One more object of the present invention is to provide a single potmethod for preparation of 2-ethyl-l-hexanol using heterogeneous catalyst such as copper supported on hydrotalcite which is capable of recycle.

One more object of the present invention is to provide a single pot method for preparation of 2-methyl-l-pentanol using heterogeneous catalyst such as copper supported on hydrotalcite which is capable of recycle.

SUMMARY OF THE INVENTION

The present invention relates to one pot synthesis of C3 -C4oxo-alcohols starting from corresponding aldehyde using recyclable copper supported on hydrotalcite which is a heterogeneous multifunctional catalyst.

The aldehyde is converted to the corresponding dimer through aldol condensation and finally hydrogenation to oxo-alcohols in single pot.

It is significant to note that copper multifunctional heterogeneous catalyst supported on hydrotalcite is used for this purpose. Wherein cascade reaction is facilitated due to acid and base sites of hydrotalcite as well as metal active sites. The present invention provides a process for the synthesis of C3 - C4oxo-alcohols comprising the steps of;

1. Charging reactor with substrate and catalyst.

2. Flushing with inert gas.

3. Passing hydrogen gas upto 20 atm. 4. Heating the reaction mixture at temperature between 100 C and 200 C for time between 5 min and 10 h.

5. Separation of final product by fractionation

In yet another embodiment of the invention, the catalyst is selected from the group consisting of copper supported on hydrotalcite with nitrate as ananion MgO- A1 ₂ 0 ₃ -N0 ₃ layered mixed oxide.

In another embodiment of the invention, the multifunctional catalyst used in the reaction comprises 1% to 30 % (w/w) of metal active species with respect to the hydrotalcite support, more preferably from 1% to 10 % (w/w).

In another embodiment of the invention, the multifunctional catalyst is recovered and reused for several cycles with consistent activity without any thermal regeneration.

In one more embodiment of the invention, the heterogeneous multifunctional catalyst used in present invention is prepared by following method.

1. Mixing magnesium nitrate,aluminium nitrate, glycerol and water.

2. Heating the mixture at temperature between 50°C and 85°C.

3. Addition of Cupric nitrate to above mixture

4. Combustion of above mixture at temperature between the ranges between 200°C and 600°C in muffle furnace. 5. Calcining the powder between the temperaturerange from 200 C to 650°C for 2 h to 5 h.

BRIEF DESCRIPTION OF DRAWINGS

It is to be noted however, that the drawing illustrates only typical embodiment of the present invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

Figure 1: Scanning Electronic Microscope image (500X) of 5% Cu-HT Catalyst as prepared in example i with uniform particle size of 50-100 μπι.

Figure 2: ChrOmatograph of 2-methyl-l-pentanol on GC for sample obtained from example 3.

Figure 3: Mass Spectrum of2-methyl-l-pentanol on GC-MS (Perkin Elmer Clarus SQ8) for sample obtained from example 3.

Figure 4: shows the concentration of all the components present in complete reaction mass for example 3 before fractionation.

Figure 5: shows the concentration of all the components present in complete reaction mass for example 2 before fractionation.

Figure 6: shows the change of selectivity with respect to time for 2-methyl-l- pentanol and 2-ethyl hexanol.

STATEMENT OF THE INVENTION:

The present invention relates to a one pot process for synthesis of C3 -C4 oxo- alcohols using heterogeneous catalyst comprising steps of; a) charging corresponding aldehyde and heterogeneous multifunctional catalyst in the reactor,

b) purging the reactor with inert gas to remove traces of air,

c) Increasing the temperature of reactor between 100 to 200°C,

d) Carrying out the reaction for a period of 5 min to 10 far with speed of agitation between 100 to 1000 rpm;

Wherein, the heterogeneous multifunctional catalyst favours the selective condensation of corresponding aldehyde and consecutive hydrogenation over oxidation and etherification, dehydration.

The one pot process preferably firstly undergoes, aldol condensation over hydrogenation of corresponding aldehyde.The aldehydes are selected from butyraldehyde and propionaldehyde. The hydrogen gas is used at pressure from atmosphencupto 20 atm. The catalyst is used in the reaction in concentration range from 3 to 10 wt% with respect to the substrate.

The heterogeneous multifunctional catalyst is selected from Cu-Mg-Al oxide supported on hydrotalcite with nitrate as an anion with the formula: Cu-[Mg(l- x) Alx(OH)2]x+[(N03/nn-)x- m.H20.

The multifunctional catalyst used in the reaction catalyst has surface area in the range of 80 to 200 m2/g, pore size of 2 to 6 nm and pore volume of 0.1 to 0.3 cm3/g. and comprises 1% to 30 % (w/w) of copper loading as active metal species with respect to the hydrotalcite support, more preferably 1% to 10 % (w/w)of copper loading.

DETAILED DESCRIPTION OF THE INVENTION;

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

The novelty of the present invention lies in the preparation of C3— C4oxo- alcohols from corresponding aldehydes with greater than 95% selectivity in a single potusing a recyclable multifunctional catalyst of the formula ;

Cu-[Mg( _1-x )Al _x (OH)2] ^x+ [(N0 ₃ /n ⁿ -) ^x' m.H ₂ 0 The aldol condensation reaction of substrate aldehyde is carried out in the presence of heterogeneous catalyst at 100-200°C whichgives thedimer, which is in turn subjected to hydrogenation in presence of hydrogen gas and metal active site to form corresponding alcohol.

The cascade reactions happening in the single pot are as described in Scheme I. The reactions (a) and (b) are desired and (c),(d) and (e) are undesired. Wherein R=H , CH ₃

Reaction Scheme I

According to the present invention the undesirable side reactions as mentioned above can be avoided by first selective condensation of aldehyde and immediately hydrogenating the condensation production the surface ofCu-[Mg ₍ i. x ₎ Al _x (OH) ₂ ] ^x+ [(N0 ₃ /n ^n" ) ^" m.H ₂ 0, catalysthaving active acid, base and metal sitesunder relatively mild conditions i.e. at temperatures between 100°C to 200°C and a pressure of about 20 atm.

The present invention provides a process for the synthesis of C3— C4 oxo- alcohols comprising the steps of;

1. Charging reactor with substrate and catalyst,

2. Flushing with inert gas,

3. Passing hydrogen gas upto 20 atm,

4. Heating the reaction mixture at temperature between 100°C and 200°C for time between 5 min and 10 h,

5. Separation of final product by fractionation.

The higher yields and selectivity towards oxoalcohols (b) are obtained when Cu- Mg-Al oxidemultifunctional catalysthas a surface area in the range of 80 to 200 m /g, pore size of 2 to 6 nm and pore volume of 0.1 to 0.3 cm /g.

This catalyst is important in the sense that they are useful in catalyzing two different desired reactions viz aldol condensation and hydrogenation in situ and thus bringing down thevaporization cost of feed and condensation cost of products as disclosed in prior art methodology, hence saves the energy and time, which are vital for a better and economical process.

The catalyst is subjected to many recycles, which displayed consistent activity and reusability.

The present process is environmentally safe since there is no disposal problem. In another embodiment of the invention, the multifunctional catalyst used in the reaction comprises 3 to 10 wt% with respect to the substrate. In another embodiment of the invention, the multifunctional catalyst is recovered by filtration and reused for several cycles with consistent activity.

In yet another embodiment of the invention, the catalyst is selected from the group consisting of active metal copper supported on hydrotalcite with nitrate as an anion i.e. Mg-Al oxide.

In one more embodiment of the invention, the heterogeneous multifunctional catalyst used in present invention is prepared by following method.

1. Mixing magnesium nitrateraluminium nitrate (in molar ratio of 3:1), glycerol and water.

2. Heating the mixture at temperature between 50°C and 85°C.

3. Addition of Cupric nitrate to above mixture

4. Cumbustion of above mixture at temperature between the range from 200°C to 600°C in muffle furnace.

5. Calcining the powder between the temperature range from 200°C to 650°C for 2 h to 5 h.

In preferred embodiments, the converting step (a) to step (b) given in scheme I wherein, the corresponding aldehyde is converted to an oxoalcohol is carried out under conditions effective to provide a substrate conversion of at least about 40%, more preferably at least about 55%, and even more preferably at least about 70%. In certain preferred embodiments the conversion is at least about 90%, and more preferably about 99%.

Although it is contemplated that the steps mentioned in present invention may be conducted in batch operation, it is preferred that the said reaction is carried out as a substantially continuous operation also.

In preferred embodiments, at least a portion of the effluent from the reaction condition is fed after distillationagain to a reactor in which the unreacted aldehyde remaining in the effluent after the first reaction condition is converted to the oxoalcohol in accordance with the present invention.

As used herein, the term "reaction conditions" is intended to include the singular and means control of any one or more processing parameters which can be modified by the operator of the reaction to produce the conversion of the feed material in accordance with the teachings contained herein. By way of example, but not by way of limitation, conversion of the feed material may be. controlled or regulated by controlling or regulating any one or more of the following: the impeller, the temperature of the reaction, the flow rate of the reactants, the presence of diluent, the amount of catalyst present in the reaction vessel, the shape and size of the reaction vessel, the pressure of the reaction, and any one combinations of these and other process parameters which will be available and known to those skilled in the art in view of the disclosure contained herein.

The present invention is further described with the help of the following examples, which are given by way of illustration all the parts, percent's and ratios are by weight unless otherwise indicated and therefore should not be construed to limit the scope of the invention in any manner.

EXAMPLES:

Ingredients of composition in weight percentage range or in other unit in following conditions:

Example 1: Preparation of Heterogeneous catalyst

A mixture of 0.024 mol magnesium nitrate, 0.008 mol aluminium nitrate,0.025 mol glycerol which acts as fuel was taken in a crucible with minimumamount of water to allow mixing.This solution was heated at 80 C for 5 minutes. 0.32 milimol cupric nitrate was added to this solution.The solution was stirred till a thick paste was obtained. The thick paste was then placed in preheated muffle furnace at 500°C.The material was further calcined at 650°C in air for 3h.

Example 2: Synthesis of 2-ethyl hexanol,

0.4mol of butyraldehyde and 0.175 g of catalyst was charges in a batch reactor of 100ml volume with temperature controller, 45° pitched bladed turbine impeller was used. The reactor was flushed with nitrogen to remove traces of air. The reactor was then pressurised with hydrogen upto 20 atm. The reaction mass was then heated to 150°Cfor 1 h.The product was separated from reaction mixture by fractionation. Selectivity obtained towards 2-ethyl hexanol was 75%.

Example 3: Synthesis of 2-methyl-l-pentanol

0.49mol of propionaldehydeand 0.175gof catalyst was charged in a batch reactor of 100ml volume with temperature controller, 45° pitched bladed turbine impeller was used. The reactor was flushed with nitrogen to remove traces of air. The reactor was then pressurised with hydrogen upto 20 atm. The reaction mass was then heated to 150°C for 1 h.The product was separated by fractionation. Selectivity obtained towards 2-methyl-l-pentanol was 45%.

Example 4: Effect of concentration of catalyst amount on the conversion of butyraldehyde and selectivity towards 2-ethyI-l-hexanol

0.4 mol of Butyraldehyde and 0.175g of catalyst was charges in a batch reactor of 100ml volume with temperature controller, 45 degree pitched bladed turbine impeller was used. The reactor was flushed with nitrogen to remove traces of air. The reactor was then pressurised with hydrogen upto 20 atm. The reaction mass was then heated to 150°C for 30 min. The product was separated by fractionation.

Table No.l Example 5: Effect of catalyst amount on conversion of propionaldehyde and selectivity towards 2-methyl-l-pentanol

0.49 mol of Propionaldehyde and 0.175g of catalyst was charges in a batch reactor of 100ml volume with temperature controller, 45 degree pitched bladed turbine impeller was used. The reactor was flushed with nitrogen to remove traces of air. The reactor was then pressurised with hydrogen upto 20 atm. The reaction mass was then heated to 150 C for 30 min. The product was separated by fractionation.

Table No.2

Example 6: Effect of % of copper loading on selectivity towards 2-ethyl-l- hexanol.

The reaction was set as per example 2 with following parameters;

Process Parameter: Support: Hydrotalcite

Temperature: 423 K

Catalyst loading in reaction: 0.05 g/cm ³

Hydrogen pressure: 20 atm

Table No.3 Example 7: Effect of Temperature on selectivity of 2-ethyl-l-hexanol and 2- methyl-l-pentanol synthesis using 5% Cu/HT catalyst synthesis using 5% Cu/HT catalyst .

The reactions were set as per example 2 and 3 with following parameters;

Catalyst loading in process: 0.05 g/cm

Hydrogen pressure: 20 atm

Table No.5