WO2015011018A1 - Process for manufacturing a cleaved product from a ricinic compound - Google Patents

Abstract

The invention pertains to a method for manufacturing a cleaved product from a ricinic compound comprising reacting at a temperature of at least 150°C at least a ricinic compound and at least one alkali in the presence of at least one thinning agent selected from the group consisting of long chain phenol derivatives of formula (I) herein below; wherein: n and m, equal to or different from each other, are integers equal to 1, 2 or 3; p is zero or an integer of 1 to 3; R_Long is a long-chain hydrocarbon group having 6 to 36 carbon atoms; R_Short is a short-chain hydrocarbon group having 1 or 2 carbon atoms.

Description

[Title established by the ISA under Rule 37.2] PROCESS FOR MANUFACTURING A CLEAVED PRODUCT FROM A RICINIC COMPOUND Cross-reference to related application

This application claims priority to Indian Provisional application No. IN 2197/DEL/2013 filed July 23, 2013, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

The invention pertains to a process for the manufacture of sebacic acid from castor oil/ricinoleic acid.

Background Art

It is well known that ricinoleic acid, generally obtained by hydrolysis of castor oil from renewable source, can be cleaved in the presence of caustic alkalis at high temperature (up to 350°C) to thus yielding sebacic acid, and possibly other acid derivatives, e.g. 10-hydroxy-decanoic acid. Reaction can be equally carried out starting from castor oil itself, with substantially similar effectiveness, adding required amount of water for initial hydrolysis of castor oil into ricinoleic acid and glycerol.

Because alkaline soaps resulting from alkaline thermal cracking are relatively hard, poor heat conductors, and practically impossible to be mixed by mechanical agitation, it is common practice in the industry to carry out the cracking process in the presence, as diluent, of phenol, cresols and/or the like. Alkaline phenolates thereof are stable at the temperatures at which the ricinoleic acid alkali cracking takes place and behave as excellent diluents, in those conditions, for various constituents of the reaction mixture, and enable reaction to be easily carried out in semi-solid phase under simple mechanical agitation.

As the reaction proceeds, volatile products, chiefly including water and organic compounds including 2-octanone and 2-octanol are generally discharged from vapour phase; at the end of the reaction, upon cooling at room temperature, a solid mass is obtained, mainly constituted of above mentioned alkaline phenolates (diluents) and alkaline salts of sebacic acid, of 10-hydroxy-decanoic acid and other by-products.

Indeed, GB 675434 describes a technique of alkali thermal cracking of ricinoleic acid in the presence of alkali derivatives of phenolic compounds, including derivatives of phenol, cresol or xylols (i.e. benzene-derivatives possibly including methyl substituents).

To recover sebacic acid, it is general practice in the industry to dissolve the above mentioned salt cake into water, and proceed with acidifying the so obtained alkaline solution to acidic pH (generally about 2, typically using sulphuric acid): in these conditions, upon boiling, substantially all sebacic acid passes into the aqueous phase, while the other organic acids and phenols mainly separate off in the form of a supernatant oily layer. From aqueous phase, upon cooling, the sebacic acid crystallizes out, and is separated from said aqueous phase.

Nevertheless, the aqueous phase, from which sebacic acid is recovered by crystallization, comprises residues of phenol contaminants (typically up to 2500 ppm) and inorganic salts (e.g. alkali sulfates if sulphuric acid is used for acidification).

Phenol/cresol being toxic, and attracting environmental concerns, disposal of waste water contaminated with such compounds generally requires extensive treatment/purification thereof for ensuring phenol/cresol content to be below legally admissible limits. While thresholds in phenol contents for waste water disposal vary from country to country, limits as low as below 1 ppm are generally encountered.

For instance, CN 102372378 20120314 pertains to the field of phenol diluent in the alkali thermal cracking of ricinoleic acid and addresses the issue of purifying waste waters from phenol, by proposing oxidation with hydrogen peroxide.

Similarly, CN 202297275 U 20120704 addresses the issue of purifying waste waters from phenol-assisted ricinoleic acid cracking, by proposing a particular multilevel extracting device.

Furthermore, because the process as above described produces generally about 30 tons of waste water per ton of sebacic acid, it is clear that a continuous quest exists for processes enabling avoiding the use of phenol/cresol derivatives, and hence avoiding generation of contaminated waste water and/or avoiding the need of extensive containment technique for recovery of such contaminants.

Aqueous alkali medium has been already proposed as suitable reaction medium for effecting thermal cracking of ricinoleic acid, although extensive foaming phenomena and need of working under pressure have substantially reduced interest for industrializing such solutions.

GB 534322 AMERICAN CYANAMID CO 19400409 teaches the thermal cracking of ricinoleic acid to yield sebacic acid in caustic acid aqueous solution, in conditions suitable for reducing foaming;

Similarly, US 2693480 SIMCO INC 19541102 discloses such thermal cracking in an aqueous medium in the presence of calcium hydroxide, as base.

Still, GB 777876 BAKER CASTOR OIL CO 19570626 discloses a process for obtaining sebacic acid compounds from ricinoleic compounds, which comprises reacting the ricinoleic compounds with alkali metal hydroxide and water, in the presence of a lead compound and/or a barium compound.

Carboxylic acids have been further suggested as diluents/thinning agents for the alkali thermal cracking.

US 6392074 JAYANT AGRO ORGANICS 20020521 discloses the use of certain isocarboxylic acids, isoaldehydes and isoalcohols as thinning agents in the alkali thermal cracking of ricinoleic acid; the thinning agent can be selected from a group of low melting aliphatic organic isocarboxylic acids containing 5 to 13 carbon units (C₅ to C₁₃), such as isononanoic acids, 2-ethyl hexanoic acid, isovaleric acids, isodecanoic acids, and isotridecanoic acids. Also included are aliphatic organic isoaldehydes and isoalcohols from C₅ to C₁₃, since these readily oxidize to the corresponding acid in reaction conditions.

Still, CN 102318892 20081210 complements the technology of above detailed reference, by teaching combining the use of an iso-carboxylic acid with certain specific high-temperature surface active agents (e.g. Sodium dodecyl sulfonate), for minimizing foaming.

Further, CN 101367719 20090218 is directed to the use of a multi-component acid diluent containing more than 2 types of organic C₇-C₁₄ acids as thinning agent in the alkali thermal cracking of ricinoleic acid; specifically exemplified is a mixture of 40% C₁₄ organic acids and 60% C₈ organic acid.

Still, mineral oils have been further suggested as diluents/thinning agents for carrying out this reaction.

Hence, CN 101239900 20080813 pertains to a method for manufacturing sebacic acid with no use of hydroxy-benzene derivative. The technique provided in this patent makes use as thinning agent of white oil, i.e. of a mixture of hydrocarbons, and more particularly, of a mixture of C₁₆-C₃₁ isoparaffins.

Summary of invention

The invention hereby provides a novel method for manufacturing cleaved products, and notably sebacic acid, from ricinic compounds, through the use of a thinning agent different from pollutant phenol/cresol derivatives.

The invention thus pertains to a method for manufacturing a cleaved product from a ricinic compound comprising reacting at a temperature of at least 150°C at least a ricinic compound, at least one alkali in the presence of at least one thinning agent selected from the group consisting of long chain phenol derivatives of formula (I) herein below:

wherein: n and m, equal to or different from each other, are integers equal to 1, 2 or 3; p is zero or an integer of 1 to 3; R_Long is a long-chain hydrocarbon group having 6 to 36 carbon atoms; R_Short is a short-chain hydrocarbon group having 1 or 2 carbon atoms.

Compounds of formula (I) have been found to reduce the solidification and foaming tendency of the reaction mixture upon high temperature caustic oxidative cleavage of ricinic compounds leading to improved yield and purity of the product.

Further, these compounds of formula (I) possess substantial insolubility in water, so as to be easily recovered as organic phase and not migrating into waste water from further processing of the reaction mixture.

This allows for the effective preparation of cleaved products such as sebacic acid (or derivatives thereof) and octanol-2, avoiding generation of substantial amounts of polluted waste waters.

Description of embodiments

As said, the invention pertains to a method for manufacturing a cleaved product from a ricinic compound.

Said ricinic compound can be at least one of castor oil, ricinoleate, ricinic acid esters, ricinoleic acid, ricinoleic acid amides, ricinoleic acid esters, sulfonated ricinoleates, ricinic alcohol, ricinoleyl alcohol, ricinoleyl alcohol ester, alkali ricinoleates; mixtures of more than one of these ricinic compounds can be used.

The ricinic compound is preferably selected from the group consisting of ricinoleic acid, glycerol tri-ricinoleate, a glyceryl tri(12-acetyl ricinoleate), glyceryl tri(12-hydroxystearate), glyceryl tri(12-acetoxystearate), alkyl ricinoleate (including methyl and ethyl ricinoleate), isoalcohol esters of ricinoleic acid (including notably 2-ethylhexanol ricinoleate), capryl ricinoleate, propylene glycol ricinoleate, and mixtures thereof.

Most preferably, the ricinic compound is ricinoleic acid.

The method of the invention can be used for producing a cleaved product of ricinic compound, generally at least one of compounds having 10 carbon atoms and compounds having 8 carbon atoms. Preferably the cleaved product is selected from the group consisting of organic carboxylic acid having 10 carbon atoms, including sebacic acid and 10-hydroxy-decanoic acid and derivatives thereof, aliphatic alcohols having 8 carbon atoms, such as octanol-2, and aliphatic acyl-containing compounds having 8 carbon atoms, such as 2-octanone.

In preferred embodiments, the method is used for producing sebacic acid and derivatives thereof.

The thinning agent is advantageously oxidatively and/or thermally stable, that is to say it can be recovered substantially unmodified after the cracking reaction.

Mixtures of compounds of formula (I) can be used as thinning agent.

The thinning agent is preferably at least one compound of formula (II):

wherein R_Long is an alkyl group of 12 to 36 carbon atoms.

More preferably, the thinning agent is a compound of formula (III):

Compound of formula (III), i.e. 3-pentadecylphenol (PDP), also known as 'Hydrogenated Cardanol' can be obtained from natural sources, and because of this reason its profile is more environmental friendly. More specifically, PDP can be obtained by hydrogenation of cardanol, which is the major component in the cashew nut shell liquid. Because India is the largest worldwide producer of both castor oil and cashew nut shell liquid, the use of derivative of cardanol in the cracking of castor oil (or derivatives thereof) is particularly advantageous from the perspective of easy availability of these compounds. PDP is advantageously substantially insoluble in water, that is to say it has advantageously solubility in water of less than 1 ppm at room temperature, so that in work-up of salts cake from pyrolysis, it will advantageously not substantially migrate into aqueous waste water obtained as mother liquor from sebacic acid crystallization.

The thinning agent is present in sufficient amount to reduce solidification and foaming, while increasing the overall yield of the reaction and allowing for hydrogen to be liberated from the reaction.

The weight ratio thinning agent/ricinic compound is generally of at least 5/95, preferably of at least 10/90, even more preferably of at least 15/85, and of at most 50/50, preferably of at most 40/60, even more preferably 35/65.

Weight ratios thinning agent/ricinic compound which have been found particularly useful are those of about 20/80.

The selection of the alkali is not particularly critical. The alkali is generally selected from the group consisting of sodium hydroxide and potassium hydroxide, with sodium hydroxide being preferred.

The method comprises reacting the ricinic compound and the alkali at a temperature of at least 150°C, preferably at least 180°C, more preferably at least 200°C, even more preferably at least 210°C. Temperatures beyond 350°C are not recommended, and preferably the temperature is kept below 300°C, more preferably below 280°C. For optimizing yields in sebacic acid, the temperature of the reaction is generally selected in the range of 220° to 250°C.

Heating can be achieved through injection of possibly superheated steam. Thus, generally, the reactor comprises a sub-surface steam line for steam supply.

The reaction mixture is agitated to allow for uniform dispersion of the reactants.

The method of the invention generally involves combining together in a reaction mixture an alkali in aqueous solution, a ricinic compound and a thinning agent and raising the temperature of the mixture to a level that will initiate a pyrolysis reaction to form a cleaved product from the ricinic compound.

The aqueous solution of the alkali generally possesses a concentration of at least 5% wt, preferably at least 10 % wt, more preferably at least 20 % wt.

The method preferably comprises the steps of:
- combining the alkali in aqueous solution, as above detailed, the thinning agent, as above detailed, and a ricinic compound, as above detailed, so as to form a mixture and heat the said mixture at a first temperature for a time sufficient to at least partially distill off water and optionally volatiles from said mixture; and
- raising the temperature to a second temperature higher than said first temperature and sufficient to initiate a cracking reaction and form a cleaved product from the ricinic compound.

First temperature is generally of at least 200°C. The aqueous alkali solution is preferably pre-heated to a temperature of 200-210°C.

Said first temperature is maintained generally until distillate is recovered from a condensate receiver.

The second temperature is generally of at least 220°C. Said second temperature is maintained generally until hydrogen evolution has been completed.

The method generally includes recovering the cleaved product and dissolving the same in water at a temperature of at least 60°C, preferably at least 70°C, more preferably at least 80°C, so as to obtain an aqueous mixture.

The thinning agents of formula (I) can be recovered for re-use as a supernatant oily phase while maintaining the aqueous mixture at a temperature of at least 60°C, preferably at least 70°C, more preferably at least 80°C.

The method further includes adding to said aqueous mixture containing the cleaved product an acid in an amount sufficient to convert the cleaved product into a free acid.

Sulfuric acid can be advantageously used.

Sebacic acid can be preferably extracted by hot water and crystallized to obtain the pure product.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The invention will now be illustrated with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.

Example 1: 1L Kettle equipped with heater, condenser, dean-stark apparatus, mechanical stirrer was charged with 90.7 g sodium hydroxide (2.267 mole) dissolved in water (50% w/w), and 38.12 g PDP (0.125 mole). Temperature was gradually increased to 130°C to remove water and then to 250°C. 170 g of ricinoleic acid (0.57 mole) was added slowly, and temperature was maintained between 230 and 250°C. Water and octanol/octanal were initially collected, and then temperature was maintained at 250°C for 4 hrs. Reaction mass was taken out of kettle and dissolved in water at 90°C. At this temperature pH of the solution was reduced to 6.2. Oily layer containing PDP which separated out was filtered. The aqueous layer containing mono-sodium salt of sebacic acid was further acidified to pH 2.0. On cooling, the white product which precipitated out was filtered and recrystallized in water. Yield: 67% and purity: 93%.

Example 2: 1L Kettle equipped with heater, condenser, dean-stark apparatus, mechanical stirrer was charged with 90.7 g sodium hydroxide (2.267 mole) dissolved in water (50% w/w), and 38.12 g PDP (0.125 mole). Temperature was gradually increased to 130°C to remove water and then to 250°C. 170 g of ricinoleic acid (0.57 mole) was added slowly, and temperature was maintained between 230 and 250°C. Water and octanol/octanal were initially collected, and then temperature was maintained at 250°C for 8 hrs. Reaction mass was taken out of kettle and dissolved in water at 90°C. At this temperature pH of the solution was reduced to 6.2. Oily layer containing PDP which separated out was filtered. The aqueous layer containing mono-sodium salt of sebacic acid was further acidified to pH 2.0. On cooling, the white product which precipitated out was filtered and recrystallized in water. Yield: 73% and purity: 98%.

Claims (15)

1. A method for manufacturing a cleaved product from a ricinic compound comprising reacting at a temperature of at least 150°C at least a ricinic compound and at least one alkali in the presence of at least one thinning agent selected from the group consisting of long chain phenol derivatives of formula (I) herein below:

   

   wherein: n and m, equal to or different from each other, are integers equal to 1, 2 or 3; p is zero or an integer of 1 to 3; R_Long is a long-chain hydrocarbon group having 6 to 36 carbon atoms; R_Short is a short-chain hydrocarbon group having 1 or 2 carbon atoms.
2. The method of claim 1 wherein said ricinic compound is at least one of castor oil, ricinoleate, ricinic acid esters, ricinoleic acid, ricinoleic acid amides, ricinoleic acid esters, sulfonated ricinoleates, ricinic alcohol, ricinoleyl alcohol, ricinoleyl alcohol ester, alkali ricinoleates, and preferably selected from the group consisting of ricinoleic acid, glycerol tri-ricinoleate, a glyceryl tri(12-acetyl ricinoleate), glyceryl tri(12-hydroxystearate), glyceryl tri(12-acetoxystearate), alkyl ricinoleate (including methyl and ethyl ricinoleate), isoalcohol esters of ricinoleic acid (including notably 2-ethylhexanol ricinoleate), capryl ricinoleate, propylene glycol ricinoleate, and mixtures thereof.
3. The method of claim 1 or 2, wherein the cleaved product is selected from the group consisting of organic carboxylic acid having 10 carbon atoms, including sebacic acid and 10-hydroxy-decanoic acid and derivatives thereof, aliphatic alcohols having 8 carbon atoms, such as octanol-2, and aliphatic acyl-containing compounds having 8 carbon atoms, such as 2-octanone.
4. The method according to anyone of the preceding claims, wherein the thinning agent is at least one compound of formula (II):

   

   wherein R_Long is an alkyl group of 12 to 36 carbon atoms.
5. The method of claim 4, wherein the thinning agent is a compound of formula (III):

   
6. The method according to anyone of the preceding claims, wherein the weight ratio thinning agent/ricinic compound is of at least 5/95, preferably of at least 10/90, even more preferably of at least 15/85, and/or of at most 50/50, preferably of at most 40/60, even more preferably 35/65.
7. The method according to anyone of the preceding claims, wherein the alkali is selected from the group consisting of sodium hydroxide and potassium hydroxide.
8. The method according to anyone of the preceding claims, said method comprises reacting the ricinic compound and the alkali at a temperature of at least 180°C, more preferably at least 200°C, even more preferably at least 210°C.
9. The method according to anyone of the preceding claims, said method involving combining together in a reaction mixture an alkali in aqueous solution, a ricinic compound and a thinning agent and raising the temperature of the mixture to a level that will initiate a pyrolysis reaction to form a cleaved product from the ricinic compound.
10. The method of claim 9, said method comprising the steps of:

    - combining the alkali in aqueous solution, the thinning agent, and the ricinic compound, so as to form a mixture and heat said mixture at a first temperature for a time sufficient to at least partially distil off water and optionally volatiles from said mixture; and

    - raising the temperature to a second temperature higher than said first temperature and sufficient to initiate a cracking reaction and form a cleaved product from the ricinic compound.
11. The method of claim 10, wherein said first temperature is of at least 200°C and/or said second temperature is of at least 220°C.
12. The method of anyone of the preceding claims, said method including recovering the cleaved product and dissolving the same in water at a temperature of at least 60°C, preferably at least 70°C, more preferably at least 80°C, so as to obtain an aqueous mixture.
13. The method of claim 12, wherein the thinning agent is recovered for re-use as a supernatant oily phase while maintaining said aqueous mixture at a temperature of at least 60°C, preferably at least 70°C, more preferably at least 80°C.
14. The method of claims 12 or 13, said method further including adding to said aqueous mixture containing the cleaved product an acid in an amount sufficient to convert the cleaved product into a free acid.
15. The method of claim 14, wherein said acid is sulfuric acid.