WO2021023803A1 - A process for the preparation of dicarboxylic acids - Google Patents

Abstract

The presently claimed invention relates to a continuous process for the preparation of dicarboxylic acids, especially a continuous process for the preparation of sebacic acid.

Description

A process for the Preparation of Dicarboxylic Acids

Field of the invention

The presently claimed invention relates to a continuous process for the preparation of dicarboxylic acids, especially a continuous process for the preparation of sebacic acid.

Background of the invention

Dicarboxylic acids find a wide variety of applications in the field of cosmetics, plasticizers, lubricants, corrosion retardants and as a chemical intermediate to produce a wide range of esters.

The sebacic acid is one of the dicarboxylic acids widely used as a synthetic intermediate to produce sebacates esters such as diisopropyl sebacate, diethylhexyl sebacate, diethyl sebacate and dibutyl sebacate. The sebacic acid is a white flake or powdered crystal, which dissolves in organic solvents such as ethanol, ether and is soluble slightly in water. The sebacic acid was named from the Latin sebaceus (tallow candle) or sebum (tallow) in reference to its use in the manufacture of candles.

The sebacic acid derivatives are used as emollients. Generally, sebacate esters are claimed to enable a good penetration and give a non-oily and silky skin feeling. These esters are also recognized to be good pigment dispersants, to provide good protection against sun light and also to prevent whitening in antiperspirant.

Sebacic acid is widely used to produce a wide range of plastics. The most important application of sebacic acid in plastics is manufacturing of polyamides (PA6.10, PA4.10, PA 10.10, etc.). Compared to other diacids having a lower carbon atom number (e.g.: adipic acid), sebacic acid provides better flexibility, ductility, hydrophobicity, and a lower melting temperature. The other types of plastics in which sebacic acid is used as a building block are copolyamides, polyesters, copolyesters, alkyd resins, polyester, polyols, polyurethanes, etc.

Disodium sebacate is used as corrosion inhibitor. It is also used as an anti-freeze fluid for aircraft, automotive and truck engines. The sebacic acid is also a raw material to produce sebacate diesters which are used as complexing agent for greases or lubricants. Generally, the diesters are used as base oils for high performance lubricants.

Presently, sebacic acid is manufactured by heating castor oil to a high temperature with an alkali. This treatment results in saponification of the castor oil to ricinoleic acid which is then cleaved to give capryl alcohol (2-octanol) and sebacic acid. Although sebacic acid yields are low, this route has been found to be cost competitive. High purity sebacic acid is manufactured from adipic acid, which comprises three steps:

1. adipic acid is partially esterified to a potassium salt of monomethyl adipate;

2. electrolysis of the potassium salt of monomethyl adipate in a mixture of methanol and water gives dimethyl sebacate

3. hydrolysis of the dimethyl sebacate to sebacic acid. The overall yield of the process is about 85%.

WO 98/35925 A1 discloses a process for the preparation of sebacic acid from castor oil, a ricinolate or a ricinoleic acid using a heat transfer fluid at a temperature of 250 to 320 °C. The process carried out preferably in presence of alkali hydroxide.

US 2, 182,056 A discloses a process for the preparation of sebacic acid from castor oil and ricinoleic acid. The process is carried out by reacting the ricinoleic acid and the caustic alkali in an aqueous solution at a preferred temperature in the range of 240 °C to 325 °C and at a super atmospheric pressure which both prevent the escape of water vapor. The preferred temperature is about 275 °C and the pressure usually observed at this temperature is 800 to 1200 lbs. US 2,182,056 A also discloses a process for carrying out the above-mentioned reaction in a continuous manner. The continuous process was achieved by pumping a mixture of ricinoleic acid and alkali hydroxide solution to a suitable pressure resisting reaction vessel maintained at a temperature of 285 to 300 °C at a rate that the reaction was completed approximately in 6 hours.

Another disadvantage in the process for the preparation of sebacic acid is the use of phenol as a solvent which leads to a large quantity of effluent.

Thus, it is an object of the presently claimed invention to provide a continuous process for the preparation of dicarboxylic acids, especially a continuous process for the preparation of sebacic acid. Another object of the presently claimed invention is to provide a continuous process which can be carried out at atmospheric pressure, at a lower reaction temperature and a reduced reaction time. It is also an object of the presently claimed invention is to omit toxic solvents such as phenol or its derivative as a diluent in the process.

Summary of the invention

Surprisingly, it was found that passing a feed stream comprising at least one alkali hydroxide, at least one precursor component for dicarboxylic acids and at least one diluent continuously through a heat exchanger which is heated to a temperature in the range of 150 to 280 °C leads to the formation of the dicarboxylic acid. Thus, in a first aspect, the presently claimed invention is directed to a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl.

The second aspect of the presently claimed invention is to provide a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid. Detailed description of the invention

Before the present compositions and formulations of the presently claimed invention are described, it is to be understood that this invention is not limited to particular compositions and formulations described, since such compositions and formulation may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the presently claimed invention will be limited only by the appended claims.

If hereinafter a group is defined to comprise at least a certain number of embodiments, this is meant to also encompass a group which preferably consists of these embodiments only. Furthermore, the terms 'first', 'second', 'third' or 'a', 'b', 'c', etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the presently claimed invention described herein are capable of operation in other sequences than described or illustrated herein. In case the terms 'first', 'second', 'third' or '(A)', '(B)' and '(C)' or '(a)', '(b)', '(c)', '(d)', ϊ, 'ϋ' etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below.

Furthermore, the ranges defined throughout the specification include the end values as well i.e. a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, applicant shall be entitled to any equivalents according to applicable law.

In the following passages, different aspects of the presently claimed invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the presently claimed invention. Thus, appearances of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment, but may.

Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the presently claimed invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

In a preferred embodiment, the presently claimed invention is directed to a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, F¾, and Ft are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl; more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 150 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and

R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R₄ and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl; even more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 180 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C₅-C₂₀ aryl, and -CH₂-CH(0C(=0)R_I)-CH₂(0C(=0)R₂); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; most preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; and in particular a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals

In another preferred embodiment, the at least one precursor component is a compound of formula

(A),

formula (A), wherein the x and y are independently of each other an integer in the range of 4 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, unsubstituted C₁-C₃₀ alkyl, linear or branched, unsubstituted C₂-C₃₀ alkenyl, unsubstituted C₅-C₂₀ cycloalkyl, unsubstituted C₅-C₂₀ cycloalkenyl and -CH₂-CH(0C(=0)-R_I)-CH₂(0C(=0)-R₂); wherein Ri and R₂ are independently of each other selected from linear or branched, C₂-C₃₀ alkenyl which is unsubstituted or substituted by -OH.

In another preferred embodiment, the compound of formula (A) is selected from the group consisting of ricinolein, lesquerolic acid or its alkali metal salt, and ricinoleic acid or its alkali metal salt; more preferably the compound of formula (A) is selected from the group consisting of ricinolein and ricinoleic acid or its alkali metal salt; and most preferably the compound of formula (A) is ricinoleic acid or its alkali metal salt.

In another preferred embodiment, the precursor component is derived from castor oil. Castor oil is obtained from the seeds of Ricinus communis and consists primarily of the triglycerides of ricinoleic acid (about 85 - 95 %), isoricinoleic, linoleic acid, oleic acid, stearic acid, palmitic acid, dihydroxystearic acid, linolenic acid and eicosanoic acid. The triglycerides of ricinoleic acid is more polar in nature compared to any other triglycerides as it has a hydroxy functional group in the 12^th carbon. This hydroxy functional group helps to derivatives the ricinoleic acid.

In another preferred embodiment, the process is a batch process or a continuous process; more preferably a process is a continuous process.

In another preferred embodiment, in step b. the temperature is in the range of 180 to 250 °C, more preferably in step b. the temperature is in the range of 200 to 250 °C, most preferably in step b. the temperature is in the range of 200 to 230 °C, and in particular in step b. the temperature is in the range of 210 to 230 °C.

In another preferred embodiment, in step b. the pressure is in the range of 0.5 bar to 25 bar, more preferably 0.5 bar to 15 bar, even more preferably 0.5 bar to 10 bar, most preferably in the range of 0.5 bar to 5 bar and in particular the pressure is atmospheric pressure.

In another preferred embodiment, the heat exchanger is selected from the group consisting of a thin film reactor, a wiped film evaporator and a falling film evaporator, more preferably the heat exchanger is selected from the group consisting of a wiped film evaporator and a falling film evaporator and most preferably the heat exchanger is a wiped film evaporator.

Within the context of the presently claimed invention a wiped film evaporator is a cylindrical vacuum column equipped with wiping elements for distributing a thin layer of liquid/slurry on a heat exchange surface/ an evaporation surface, causing the formation of a thin film of the material and high surface to volume ratio of the material in the vessel. The cylindrical vacuum column may be arranged vertically or horizontally; preferably the cylindrical vacuum column is arranged vertically. The wiped film evaporator further comprises a rotor mounted with the cylindrical vacuum column and provided with a number of wiping elements, i.e. wiping blades or wiping rollers, and a motor is provided to drive the rotor. The rotor is arranged within the cylindrical vacuum column so that upon rotation by the motor, the wiping elements are caused to move over the inner surface, i.e. the evaporation surface, of the cylindrical vacuum column. The wiping elements may contact the inner surface of the cylindrical vacuum column or, alternatively, a small gap or clearance may be left between the tips of the wiping elements and the inner surface of the cylindrical vacuum column. This design greatly increases the area of the effective heat exchange surface/evaporation surface and shortens the required period of heat exposure of the liquid/slurry passing over the heat exchange surface/ the evaporation surface.

In another preferred embodiment, the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide and cesium hydroxide; more preferably the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide, lithium hydroxide, and potassium hydroxide; most preferably the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide and potassium hydroxide; and in particular the at least one alkali hydroxide is potassium hydroxide.

In another preferred embodiment, the at least one diluent is selected from the group consisting of paraffin oil, saturated or unsaturated, substituted or unsubstituted, branched or linear C3-C30 alkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C6-C30 cycloalkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C8-C30 alcohols, substituted or unsubstituted C5-C20 aryl, paraffins and waxes, more preferably selected from the group consisting paraffin oil, saturated or unsaturated, substituted or unsubstituted, branched or linear C3-C30 alkyl carboxylic acid, substituted or unsubstituted C5-C20 aryl, paraffins and waxes , most preferably the at least one diluent is paraffin oil.

Within the context of the presently claimed invention, the paraffin oil refers to liquid paraffin oil obtained by refining crude petroleum. The paraffin oil is a transparent, colorless oil, composed mainly of alkanes and cycloalkanes, related to petroleum jelly and has a density of around 0.8 g/cm³.

In another preferred embodiment, the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0: 1.0 to 1.0:15; more preferably the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0:.0 to 1.0:12; even more preferably the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0:3.0 to 1.0:10; most preferably the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1 .0:4.0 to 1.0:8.0; and in particular the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0:5.0 to 1.0:8.0.

In another preferred embodiment, the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0:4.0 to 1.0:10.0.

In another preferred embodiment, the heat exchanger is maintained at an atmospheric pressure.

In another preferred embodiment, the thin film evaporator is maintained at an atmospheric pressure. In another preferred embodiment, the wiped film evaporator is maintained at an atmospheric pressure.

In another preferred embodiment, the falling film evaporator is maintained at an atmospheric pressure.

In another preferred embodiment, the step b. is carried out in the absence of an inert gas.

In another preferred embodiment, the step b. is carried out in the presence of at least one inert gas.

In another preferred embodiment, the at least one inert gas is selected from the group consisting of nitrogen and argon, more preferably the at least one inert gas is nitrogen.

In another preferred embodiment, the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:1.0 to 1.0:30; more preferably the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:1.0 to 1 .0:20; even more preferably the weight ratio of the at least one precursor component to the at least one diluent is from 1.0: 1.0 to 1.0:10; most preferably the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:1.0 to 1.0:5.0; and in particular the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:2.0 to 1.0:3.0.

In another preferred embodiment, the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:2.0 to 1.0:5.0.

In another preferred embodiment, the feed stream is passed continuously through the heat exchanger at a rate of 1.0 to 5.0 kg/h; more preferably the feed stream is passed continuously through the heat exchanger at a rate of 1.0 to 4.0 kg/h; even more preferably the feed stream is passed continuously through the heat exchanger at a rate of 1.5 to 2.5 kg/h; most preferably the feed stream is passed continuously through the heat exchanger at a rate of 1 .8 to 2.2 kg/h, each based on a reactor having surface area of 0.11m² and a volume of 2.75L.

In another preferred embodiment, the feed stream is passed continuously through the thin film evaporator at a rate of 1.0 to 5.0 kg/h; more preferably the feed stream is passed continuously through the thin film evaporator at a rate of 1 .0 to 4.0 kg/h; even more preferably the feed stream is passed continuously through the thin film evaporator at a rate of 1.5 to 2.5 kg/h; most preferably the feed stream is passed continuously through the thin film evaporator at a rate of 1.8 to 2.2 kg/h, each based on a reactor having surface area of 0.11m² and a volume of 2.75L. In another preferred embodiment, the feed stream is passed continuously through the falling film evaporator at a rate of 1.0 to 5.0 kg/h; more preferably the feed stream is passed continuously through the falling film evaporator at a rate of 1.0 to 4.0 kg/h; even more preferably the feed stream is passed continuously through the falling film evaporator at a rate of 1.5 to 2.5 kg/h; most preferably the feed stream is passed continuously through the falling film evaporator at a rate of 1.8 to 2.2 kg/h, each based on a reactor having surface area of 0.11m² and a volume of 2.75L.

In another preferred embodiment, the feed stream is passed continuously through the wiped film evaporator at a rate of 1.0 to 5.0 kg/h; more preferably the feed stream is passed continuously through the wiped film evaporator at a rate of 1.0 to 4.0 kg/h; even more preferably the feed stream is passed continuously through the wiped film evaporator at a rate of 1.5 to 2.5 kg/h; most preferably the feed stream is passed continuously through the wiped film evaporator at a rate of 1.8 to 2.2 kg/h, each based on a reactor having surface area of 0.11 m² and a volume of 2.75 L.

In another preferred embodiment, the feed stream is passed continuously through the heat exchanger for a period of 30 seconds to 20 minutes; more preferably the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 15 minutes; even more preferably the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 10 minutes, most preferably the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 5 minutes and in particular the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 3 minutes.

In another preferred embodiment, the feed stream is passed continuously through the thin film evaporator for a period of 30 seconds to 20 minutes; more preferably the feed stream is passed continuously through the thin film evaporator for a period of 1 minute to 15 minutes; even more preferably the feed stream is passed continuously through the thin film evaporator for a period of 1 minute to 10 minutes, most preferably the feed stream is passed continuously through the thin film evaporator for a period of 1 minute to 5 minutes and in particular the feed stream is passed continuously through the thin film evaporator for a period of 1 minute to 3 minutes.

In another preferred embodiment, the feed stream is passed continuously through the falling film evaporator for a period of 30 seconds to 20 minutes; more preferably the feed stream is passed continuously through the falling film evaporator for a period of 1 minute to 15 minutes; even more preferably the feed stream is passed continuously through the falling film evaporator for a period of 1 minute to 10 minutes, most preferably the feed stream is passed continuously through the falling film evaporator for a period of 1 minute to 5 minutes and in particular the feed stream is passed continuously through the falling film evaporator for a period of 1 minute to 3 minutes. In another preferred embodiment, the feed stream is passed continuously through the wiped film evaporator for a period of 30 seconds to 20 minutes; more preferably the feed stream is passed continuously through the wiped film evaporator for a period of 1 minute to 15 minutes; even more preferably the feed stream is passed continuously through the wiped film evaporator for a period of 1 minute to 10 minutes, most preferably the feed stream is passed continuously through the wiped film evaporator for a period of 1 minute to 5 minutes and in particular the feed stream is passed continuously through the wiped film evaporator for a period of 1 minute to 3 minutes.

In another preferred embodiment, the feed stream does not comprise phenol or its derivatives.

In another preferred embodiment, the feed stream is present in the form of a slurry.

Within the context of the presently claimed invention, slurry is a mixture of precursor component, alkali hydroxide and the solvent(s). the physical state of slurry can be liquid-liquid or a solid-liquid dispersion, more preferably a solid-liquid dispersion.

In a preferred embodiment, the presently claimed invention is directed to a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a thin film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the thin film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R₄ and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R₂, R₃, and R₄ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a thin film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the thin film evaporator which is heated to a temperature in the range of 150 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R₄ and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R₂, R₃, and R₄ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; even more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a thin film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the thin film evaporator which is heated to a temperature in the range of 180 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C₅-C₂₀ aryl, and -CH₂-CH(0C(=0)R_I)-CH₂(0C(=0)R₂); wherein Ri and R₂ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; most preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a thin film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the thin film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A), formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri and R₂ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃o alkyl, linear or branched, substituted or unsubstituted C₂-C₃o alkenyl, substituted or unsubstituted C₅-C₂o cycloalkyl and substituted or unsubstituted C₅-C₂o cycloalkenyl; and in particular a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a thin film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the thin film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals. In a preferred embodiment, the presently claimed invention is directed to a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a falling film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the falling film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl; more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a falling film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the falling film evaporator which is heated to a temperature in the range of 150 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A), formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; even more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a falling film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the falling film evaporator which is heated to a temperature in the range of 180 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, and -CH2-CH(0C(=0)RI)-CH2(0C(=0)R2); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; most preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a falling film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the falling film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; and in particular a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a falling film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the falling film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals.

In a preferred embodiment, the presently claimed invention is directed to a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R₄ and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R₂, R₃, and R₄ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; c) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C₁-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl, substituted or unsubstituted C₅-C₂₀ cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R₄ and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R₂, R₃, and R₄ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃₀ alkyl, linear or branched, substituted or unsubstituted C₂-C₃₀ alkenyl, substituted or unsubstituted C₅-C₂₀ cycloalkyl and substituted or unsubstituted C₅-C₂₀ cycloalkenyl; even more preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; c) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 180 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, and -CH₂-CH(0C(=0)R_I)-CH₂(0C(=0)R₂); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl; most preferably a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A), formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri and R₂ are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C₂-C₃o alkyl, linear or branched, substituted or unsubstituted C₂-C₃o alkenyl, substituted or unsubstituted C₅-C₂o cycloalkyl and substituted or unsubstituted C₅-C₂o cycloalkenyl; and in particular a process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 180 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals. In another preferred embodiment, the presently claimed invention is directed to a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid; more preferably the presently claimed invention is directed to a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 180 to 250 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid; even more preferably the presently claimed invention is directed to a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 200 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid; most preferably the presently claimed invention is directed to a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 200 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil and ricinoleic acid; and in particular preferably, the presently claimed invention is directed to a process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 200 to 230 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is ricinoleic acid.

In another preferred embodiment, the dicarboxylic acid which is formed in step (b) is isolated by a method selected from the group consisting of chemical separation, acid-base neutralization, distillation, evaporation, column chromatography, filtration, concentration, crystallization and re crystallization or a combination thereof. A person skilled in the art is aware of such techniques.

In another preferred embodiment, sebacic acid which is formed in step (b) is isolated by any method known in the art, selected from the group consisting of chemical separation, acid-base neutralization, distillation, evaporation, column chromatography, filtration, concentration, crystallization and re crystallization or a combination thereof. A person skilled in the art is aware of such techniques.

The presently claimed invention is associated with at least one of the following advantages:

• The process is a continuous process for the preparation of dicarboxylic acid.

• The continuous process provides shorter reaction time, hence the formation of the degradation impurities is eliminated or reduced in the process.

• The continuous process eliminates the use of high-volume equipment; thus, the space requirement has been reduced considerably.

• The continuous process consumes less energy compared to the batch process as the reaction time is reduced to few minutes. Thus, the continuous process leads to energy efficient reaction.

• The risk involved with hydrogen by-product is minimized, as the flow of reactant though the heat exchanger is controlled at a rate of 10 to 30 g/minutes which in turn to produced controlled amount of hydrogen per minutes, thus eliminating the risk of explosion and fire.

Embodiments:

1. A process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl.

2. The process according to embodiment 1 , wherein x and y are independently of each other an integer in the range of 4 to 10, and

R is selected from the group consisting of alkali metals, hydrogen, linear or branched, unsubstituted

C₁-C₃₀ alkyl, linear or branched, unsubstituted C₂-C₃₀ alkenyl, unsubstituted C₅-C₂₀ cycloalkyl, unsubstituted C5-C20 cycloalkenyl and -CH₂-CH(0C(=0)-R_I)-CH₂(0C(=0)-R₂); wherein Ri and R2 are independently of each other selected from linear or branched, C2-C30 alkenyl which is unsubstituted or substituted by -OH.

3. The process according to embodiment 1 , wherein the compound of formula (A) is selected from the group consisting of ricinolein, lesquerolic acid and ricinoleic acid. 4. The process according to embodiment 1 , wherein the precursor component is derived from castor oil.

5. The process according to embodiment 1 , wherein the process is a continuous process.

6. The process according to embodiment 1 , wherein in step b. the temperature is in the range of 200 to 250 °C.

7. The process according to embodiment 1 , wherein the heat exchanger is selected from the group consisting of a thin film reactor, a wiped film evaporator and a falling film evaporator.

8. The process according to embodiments 1 to 7, wherein the heat exchanger is a wiped film evaporator.

9. The process according to embodiment 1 , wherein the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide and cesium hydroxide.

10. The process according to embodiment 9, wherein the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide and potassium hydroxide.

11 . The process according to embodiment 10, wherein the at least one alkali hydroxide is potassium hydroxide.

12. The process according to embodiment 1, wherein the at least one diluent is selected from the group consisting of paraffin oil, saturated or unsaturated, substituted or unsubstituted, branched or linear C3-C30 alkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C6-C30 cycloalkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C8-C30 alcohols, substituted or unsubstituted C5-C20 aryl, paraffins and waxes.

13. The process according to embodiment 1 , wherein the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0:1.0 to 1.0:15.

14. The process according to embodiment 13, wherein the molar ratio of the at least one precursor component to the at least one alkali hydroxide is from 1.0:4.0 to 1.0:10.0.

15. The process according to embodiment 1 , wherein the heat exchanger is maintained at atmospheric pressure. 16. The process according to embodiment 1 , wherein the step b. is carried out in presence of at least one inert gas.

17. The process according to embodiment 1 , wherein the at least one inert gas is selected form the group consisting of argon and nitrogen.

18. The process according to embodiment 1 , wherein the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:1.0 to 1.0:30.

19. The process according to embodiment 1 , wherein the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:2.0 to 1.0:5.0.

20. The process according to embodiment 1 , wherein the feed stream is passed continuously through the heat exchanger at a rate of 1 to 5 kg/h, based on a reactor having surface area of 0.1m² and a volume of 2.75 L.

21. The process according to embodiment 20, wherein the feed stream is passed continuously through the heat exchanger at a rate of 1 to 4 kg/h, based on a reactor having surface area of 0.1m² and a volume of 2.75 L.

22. The process according to embodiment 21 , wherein the feed stream is passed continuously through the heat exchanger at a rate of 1.5 to 2.5 kg/h, based on a reactor having surface area of 0.1m² and a volume of 2.75 L.

23. The process according to embodiment 1 , wherein the feed stream is passed continuously through the heat exchanger for a period of 30 seconds to 20 minutes.

24. The process according to embodiment 23, wherein the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 10 minutes.

25. The process according to embodiment 24, wherein the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 3 minutes.

26. The process according to any of the preceding embodiment, wherein the feed stream does not comprise a phenolic compound.

27. The process according to any of the preceding embodiment, wherein the feed stream is present in the form of a slurry.

28. A process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, NH₂, NHR₃, NR3R4 and -CH₂-CH(0C(=0)Ri)-CH₂(0C(=0)R₂); wherein Ri, R2, R3, and R4 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl.

29. A process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid. 30. The process according to embodiment 29, wherein the step b. is the temperature is in the range of 200 to 250 °C.

While the presently claimed invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the presently claimed invention.

Examples

The presently claimed invention is illustrated in detail by non-restrictive working examples which follow. More particularly, the test methods specified hereinafter are part of the general disclosure of the application and are not restricted to the specific working examples.

Materials:

Ricinoleic acid is available from M/S Vishal Pharma Chem, India.

KOH is available from SD Fine Chem, India.

Paraffin oil is available from Merck.

Batch Process:

Experiment 1 : A slurry of a feed stream comprising ricinoleic acid (100 g - 75% purity -0.2512 mols), potassium hydroxide (93.8 g - 85 % purity - 1.424 mols, molar ratio 1 :5.66) and paraffin oil (180 g) was charged to a reactor and maintained at 250 - 270 °C. The reaction mass was stirred for 6 hours at 240 - 250 °C. After completion of the reaction, toluene (100 ml.) was charged to the reaction mass and filtered to obtain a solid. The solid obtained was mixed with water (2000 ml.) and the pH of the solution was adjusted to 6.0 to 6.5 using cone. HCI (40 - 50 ml). The pH adjusted solution was washed with toluene (200 ml.) and the pH was further adjusted to 1 using cone. HCI to precipitate the sebacic acid. The precipitated sebacic acid was filtered and dried under vacuum to get 36.5 g of the product (yield: 72 %). Space time yield is 9.0 Kg/m³h.

Continuous process:

Experiment 2: A feed stream was prepared by mixing ricinoleic acid (200 g - 75% purity - 0.5025 mol), potassium hydroxide (188 g - 85 % purity - 2.8 54 mols, molar ratio 1:5 + 212 g demineralized water water) and paraffin oil (500 g).

The feed stream was charged continuously through a preheated wiped film evaporator at a temperature in the range of 220 to 230 °C (having a surface area of 0.11m² and a volume of 2.75L) at a constant rate using a peristaltic dosing pump over a period of 1 hour (18.33 g/minute). The reaction mass was collected, and the product was isolated using standard procedure to get 73 g sebacic acid (yield 72 % with a purity > 95%). Space time yield is 18 Kg/m³h. Experiment 3: Experiment 3 was performed similar to experiment 2 however, the wiped film evaporator was operated at a temperature of around 280 °C. The product obtained was dark brown in colour and the yield was around 30 %. Experiment 4: Experiment 4 was performed similar to experiment 2 however, the wiped film evaporator was operated at a temperature of around 150 °C. The reaction was incomplete leading to very less yield.

Experiment 5: Experiment 5 was performed similar to experiment 2 however, the wiped film evaporator was operated at a temperature of around 180 °C. The reaction was incomplete leading to very less yield (around 50 % yield).

Claims

Claims:

1. A process for the preparation of a dicarboxylic acid comprising at least the steps of: a) providing a reaction system comprising a heat exchanger; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the heat exchanger which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is a compound of formula (A),

formula (A), wherein x and y are independently of each other an integer in the range of 1 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, substituted or unsubstituted C1-C30 alkyl, linear or branched, substituted or unsubstituted C2- C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl, substituted or unsubstituted C5-C20 cycloalkenyl, substituted or unsubstituted C5-C20 aryl, and -CH₂-CH(OC(=0)R_I)- CH₂(0C(=0)R₂); wherein Ri and R2 are independently of each other selected from the group consisting of linear or branched, substituted or unsubstituted C2-C30 alkyl, linear or branched, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C5-C20 cycloalkyl and substituted or unsubstituted C5-C20 cycloalkenyl.

2. The process according to claim 1 , wherein x and y are independently of each other an integer in the range of 4 to 10, and R is selected from the group consisting of alkali metals, hydrogen, linear or branched, unsubstituted C1-C30 alkyl, linear or branched, unsubstituted C2-C30 alkenyl, unsubstituted C₅- C20 cycloalkyl, unsubstituted C5-C20 cycloalkenyl and -CH₂-CH(0C(=0)-R_I)-CH₂(0C(=0)-R₂); wherein Ri and F¾ are independently of each other selected from linear or branched, C2-C30 alkenyl which is unsubstituted or substituted by -OH.

3. The process according to claim 1 , wherein the compound of formula (A) is selected from the group consisting of ricinolein, lesquerolic acid and ricinoleic acid.

4. The process according to any of the preceding claims, wherein the precursor component is derived from castor oil.

5. The process according to any of the preceding claims, wherein the process is a continuous process.

6. The process according to claim 1 , wherein in step b. the temperature is in the range of 200 to 250 °C.

7. The process according to claim 1 , wherein the heat exchanger is selected from the group consisting of a thin film reactor, a wiped film evaporator and a falling film evaporator.

8. The process according to any of the claims 1 to 6, wherein the heat exchanger is a wiped film evaporator.

9. The process according to claim 1 , wherein the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide and cesium hydroxide.

10. The process according to claim 9, wherein the at least one alkali hydroxide is selected from the group consisting of sodium hydroxide and potassium hydroxide.

11. The process according to claim 10, wherein the at least one alkali hydroxide is potassium hydroxide.

12. The process according to any of the preceding claims, wherein the at least one diluent is selected from the group consisting of paraffin oil, saturated or unsaturated, substituted or unsubstituted, branched or linear C3-C30 alkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C6-C30 cycloalkyl carboxylic acid, saturated or unsaturated, substituted or unsubstituted, branched or linear C8-C30 alcohols, substituted or unsubstituted C₅- C20 aryl, paraffins and waxes.

13. The process according to any of the preceding claims, wherein the molar ratio of the at least one precursor component to the at least one alkali hydroxide is in the range from 1.0: 1.0 to 1.0:15.

14. The process according to claim 13, wherein the molar ratio of the at least one precursor component to the at least one alkali hydroxide is from 1.0:4.0 to 1.0:10.0.

15. The process according to any of the preceding claims, wherein the heat exchanger is maintained at a pressure is in the range of 0.5 bar to 25 bar

16. The process according to any of the preceding claims, wherein the heat exchanger is maintained at atmospheric pressure.

17. The process according to claim 1 , wherein the step b. is carried out in presence of at least one inert gas.

18. The process according to claim 1 , wherein the at least one inert gas is selected from the group consisting of argon and nitrogen.

19. The process according to any of the preceding claims, wherein the weight ratio of the at least one precursor component to the at least one diluent is from 1.0:1.0 to 1.0:30.

20. The process according to any of the preceding claims, wherein the feed stream is passed continuously through the heat exchanger at a rate of 1 to 5 kg/h, based on a reactor having surface area of 0.1 m² and a volume of 2.75 L.

21. The process according to claim 20, wherein the feed stream is passed continuously through the heat exchanger at a rate of 1.5 to 2.5 kg/h, based on a reactor having surface area of 0.1 m² and a volume of 2.75 L.

22. The process according to any of the preceding claims, wherein the feed stream is passed continuously through the heat exchanger for a period of 30 seconds to 20 minutes.

23. The process according to claim 22, wherein the feed stream is passed continuously through the heat exchanger for a period of 1 minute to 3 minutes.

24. The process according to any of the preceding claims, wherein the feed stream does not comprise a phenolic compound.

25. The process according to any of the preceding claims, wherein the feed stream is present in the form of a slurry.

26. A process for the preparation of sebacic acid comprising at least the steps of: a) providing a reaction system comprising a wiped film evaporator; b) passing a feed stream comprising at least one alkali hydroxide, at least one precursor component and at least one diluent continuously through the wiped film evaporator which is heated to a temperature in the range of 150 to 280 °C to obtain a product stream comprising the dicarboxylic acid; and c) isolating the dicarboxylic acid from the product stream; wherein the at least one precursor component is selected from the group consisting of castor oil, ricinolein and ricinoleic acid.

27. The process according to claim 26, wherein the step b. the temperature is in the range of 200 to

250 °C.