Claims:We Claim:
1. A process for production of alkyl esters comprising reacting a feedstock having a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst.
2. A process for production of alkyl esters as claimed in claim 1, wherein the reaction is carried out at a temperature between 120 oC and 250 oC under autogeneous pressure for a period of 30 minutes to 8 hours.
3. A process for production of alkyl esters as claimed in claim 1, wherein the fly ash catalyses esterification, transesterification and interesterification of the monobasic acid ester and/or polybasic acid ester; esterification of monobasic acid and/ or polybasic acid; or both depending on the feedstock.
4. A process for production of alkyl esters as claimed in claim 1, wherein the amount of fly ash used as a catalyst is in the range of 1 to 30 weight percentage with respect to the feedstock.
5. A process for production of alkyl esters as claimed in claim 1, wherein the fly ash comprises of two or more of SiO2, Al2O3, Fe2O3, CaO, MgO and SO3.
6. A process for production of alkyl esters as claimed in claim 1 or 5, wherein the fly ash comprises of 5 to 12 weight percentage SiO2; 2 to 11 weight percentage Al2O3; 0.50 to 2.0 weight percentage Fe2O3; 35 to 60 weight percentage CaO; 0.40 to 1 weight percentage MgO; 26 to 30 weight percentage SO3.

7. A process for production of alkyl esters as claimed in claim 1, wherein the process further comprises of recovering the fly ash from the reaction mixture.
8. A process for production of alkyl esters as claimed in claim 1, wherein the recovered fly ash is recycled.
9. A process for production of alkyl esters as claimed in claim 7 or 8, wherein the process further comprises of separating the fly ash from the reaction mixture; washing and drying the washed fly ash and reusing the fly ash as a catalyst for producing alkyl esters.
10. A process for production of alkyl esters as claimed in claim 1, wherein the polyol is selected from ethylene glycol, glycerol, sorbitol, sucrose, xylitol, ascorbic acid, any sugar derivative or combination thereof.
11. A process for production of alkyl esters as claimed in claim 1, wherein the molar ratio of the feedstock to polyol is in the range of 1:0.1 to 1:1.2.

Dated this 9th day of November, 2015

Aparna Kareer
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 1359 , Description:Present disclosure provides a process for production of alkyl esters using fly ash as a catalyst.

BACKGROUND
Alkyl esters are chemical compounds derived from an acid in which at least one hydroxyl group is replaced by an alkoxy group. Alkyl esters have applicability in diverse fields such as plasticizers, lubricants, surfactants, emollients, opacifiers, and pearling agents. Alkyl esters are also used as one of the ingredients in various cosmetics apart from the niche application attributed to specific property of individual product molecule.
In general, method of ester preparation depends on the nature of the feedstock and the process can be multi-step depending on the complexity of the feedstock- reagent interaction. Catalysts are generally employed to make the reaction facile and since the ester formation reaction is reversible, one of the reactants is taken in higher proportions. The usage of large excess of alcohols (generally low boiling) is practiced to take this reversible reaction in the forward direction and excess of the alcohol is recovered either through vacuum distillation or selective extraction procedures once the reaction is complete. Use of homogeneous catalyst invariably calls for an aqueous wash step to remove the soluble catalyst or a resin treatment to selectively retain the catalyst while allowing the neutral product to pass through. This therefore adds to downstream processing.
In order to overcome the problems associated with use of a homogeneous catalyst, heterogenous solid catalysts for the preparation of alkyl esters have been developed. For example, various basic metal oxides, such as magnesium methoxide, calcium oxide, calcium alkoxide, and barium hydroxide, have been demonstrated to be active catalysts for transesterification.
However, the recyclability of these solid base catalysts is poor. This is because of the moderate solubility of some of these solid metal oxides, hydroxides and alkoxides in methanol/ethanol and strong physical adsorption of the reaction products on their surfaces.
Use of double metal cyanides and metal (e.g., Zn, Mo) embedded on supports (like alumina) as recyclable solid catalysts have also been claimed. The major drawback of such a catalyst is its relatively higher cost of preparation and therefore requiring large number of recycles. These recovery and further activation for recycling of catalyst cause technical and economic restrains.
In view of these drawbacks, there is a need to develop a process for preparation of alkyl esters that does not require tedious aqueous washes and/ or neutralization steps. An economical and recyclable catalyst that can be easily separated from the alkyl ester products is also needed. Moreover, a catalyst that can economically catalyse esterification and transesterification / interesterification is desirable.

SUMMARY
A process for production of alkyl esters is disclosed. The process comprising reacting a feedstock having a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst.

DETAILED DESCRIPTION
The invention as described herein is an improvement over the applicant’s earlier filed patent application no 1181/MUM/2008 dated June 04, 2008.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the disclosed process and system, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may but do not necessarily, all refer to the same embodiment.
A process for production of alkyl esters is disclosed. The process comprising reacting a feedstock having a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst. Fly ash is generally defined as finely divided residue resulting from the combustion of powdered coal transported from the firebox through the boiler by the flue gases. The composition of the fly-ash is found to vary on the type of coal used. However, the composition of the fly ash typically has the following composition by weight percentage (5-12) SiO2 : (2-11) Al2O3 : (0.50 - 2.0) Fe2O3 : (35-60) CaO : (0.40-1) MgO : (26-30) SO3.
The process for production of alkyl esters comprises reacting a feedstock that includes a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst to get a reaction mixture comprising a mixture of alkyl esters, polyol and fly ash; and recovering alkyl esters from the reaction mixture.
Fly ash used in the process catalyzes esterification, transesterification and interesterification of the monobasic acid ester and/or polybasic acid ester present in the feedstock as illustrated in the exemplified reactions below:
HOOC-R-COOR’ + R”OH ? R’OOC-R-COOR”
R’OOC-R-COOR’ + R1COOR2 ? R’OOC-R-COOR2 + R1COOR’
Fly ash also catalyzes the esterification of monobasic acid and/ or polybasic acid present in the feedstock as illustrated in the exemplified reaction below:
R (COOH) n + R’-OH ? R(COOR’)n-x (COOH) x+ (n-x) H2O
Where x is 0 to n-1
1-30 weight percentage of fly ash with respect to the feedstock may be used as a catalyst for the reaction. The molar ratio of the feedstock to polyol is in the range of 1: 0.1 to 1: 1.2.
A greater than 98% conversion is achieved by the process and a greater than 99% conversion is achieved using fly ash as a catalyst under preferred reaction condition.
Fly ash is easily recovered from the reaction mixture by any method including gravitational settling, filtration, centrifugation or any combination thereof.
In accordance with an aspect, once separated, the fly ash may be reused, if needed, as a catalyst for alkyl ester production without any loss of catalytic activity. The recyclability has been tested for at least five cycles and the reaction proceeds with quantitative yield of the products.
In accordance with an aspect, the fly ash recovered from the reaction mixture may be washed and dried prior to reusing it as a catalyst for the production of alkyl esters. The fly ash recovered from the reaction mixture may be washed with any organic solvent in which the organics are soluble.
Recovery of alkyl esters from the reaction mixture is carried out by separating the catalyst from the reaction mixture. The catalyst may be separated by using known separation techniques including filtration. Further, excess polyol after the completion of the reaction can be separated by distillation.
In accordance with an aspect, the production of alkyl esters comprises of reacting a feedstock having a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst at an elevated temperature and autogenerated pressure for a pre-determined period of time to get a reaction mixture; removing the fly ash catalyst from the said reaction mixture by filtration or any suitable conventional separation method to get a liquid, an alcohol containing alkyl ester, and removing the alcohol from alkyl esters by conventional distillation to get alkyl ester.
The feed stock used for this process may contain a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof. In accordance with an embodiment, the monobasic acid ester includes but not limited to glycerol esters, Ethylene glycol esters and sugar ester. The polybasic acid ester includes but not limited to dimethyl adipate, dioctyl adipate, dioctylpthalate, di-isononyl phthalate and dimethyl succinate. In accordance with an embodiment, polybasic acid esters are generated during the reaction of polybasic acid and alcohol. The monobasic acid includes but not limited to fatty acid, aromatic and aliphatic carboxylic acids. The polybasic acid includes but not limited to adipic acid, pthalic acid (and its anhydride), succinic acid and citric acid.
The polyol is selected from the group consisting of ethylene glycol, glycerol, sorbitol, sucrose, xylitol, ascorbic acid and any sugar derivative or combination thereof.
In accordance with an aspect, the reaction is carried out at an elevated temperature of 120-250ºC under autogenerated pressures.
The following examples are provided to explain and illustrate certain preferred embodiments of the process of the invention.
Example 1
Synthesis of Ethylene glycol monostearate
In a 1L high pressure reactor, 100 g of Stearic acid (0.35 moles) ,10 gm. Catalyst and 25 gm. Ethylene glycol ( 0.4 moles) was reacted at 200oC for 2 hrs., at 300 RPM under autogeneous pressure conditions. At the end of two hours, the vapors were removed. Reaction mixture, devoid of water, was stirred at 220 oC for additional two hours and the reaction mass cooled to about 70 oC and filtered over a Buchner funnel. Traces of Ethylene glycol were removed by vacuum distillation.
Example 2
Synthesis of Glycerol monostearate
In a 1 L high pressure reactor, 100 g of Stearic acid (0.35 moles), 10 gm. Catalyst and 36 gm. (0.4 moles) glycerol was reacted at 200oC for 2 hrs., at 300 RPM under autogeneous pressure conditions. The vapors were removed at the end of two hours and vacuum was applied to completely remove any water. Reaction mixture, devoid of water, was stirred with excess of alcohol stirred at 220 oC for further two hours and the reaction mass cooled to about 70 oC and filtered over a Buchner funnel. Traces of glycerol were removed by vacuum distillation.

Example 3
Synthesis of ethylene glycol Adipate (Esterification Reaction)
In a 1 L high pressure reactor, 146.14g of adipic acid (1 moles), 10 gm. catalyst and 31 gm. ethylene glycol (0.5 moles) were added and they were made to react between 210oC for 2 hrs. The vapors were removed at the end of two hours and water completely removed. Reaction mass was further stirred at 210 oC for further two hours and the reaction mass cooled to about 50 oC and filtered over a Buchner funnel. Excess ethylene glycol was removed by vacuum distillation to obtain ethylene glycol Adipate.
Example 4
Synthesis of Ethylene glycol Adipate (Trans- esterification Reaction)
In a 1 L high pressure reactor, 100 g of dimethyl Adipate (0.57 moles), 10 gm. catalyst and 17 gm. ethylene glycol (0.27 moles) were added and they were made to react between 210oC for 2 hrs. The vapors were removed at the end of two hours and methanol completely removed. Reaction mass was further stirred at 210 oC for further two hours and the reaction mass cooled to about 50 oC and filtered over a Buchner funnel. Excess ethylene glycol was removed by vacuum distillation to obtain ethylene glycol Adipate.
Example 5
Synthesis of Ethylene glycol stearate (Trans- esterification Reaction)
In a 1 L high pressure reactor, 100 g of Methyl Stearate (0.35 moles), 10 gm. Catalyst and 11 gm. (0.17 moles) Ethylene glycol was reacted at 200 oC for 2 hrs. at 300 RPM under autogeneous pressure conditions. The vapors were removed at the end of two hours and vacuum was applied to completely remove any Methanol. Reaction mass was stirred with excess of Ethylene glycol stirred at 200 oC for further two hours and the reaction mass cooled to about 70 oC and filtered over a Buchner funnel. Traces of Ethylene glycol were removed by vacuum distillation to obtain Ethylene glycol distearate.

SPECIFIC EMBODIMENTS ARE PROVIDED BELOW
A process for production of alkyl esters comprising reacting a feedstock having a monobasic acid ester, a polybasic acid ester, a monobasic acid, a polybasic acid or mixture thereof with a polyol in the presence of fly ash as a catalyst.
Such Process(s), wherein the reaction is carried out at a temperature between 120 oC and 250 oC under autogeneous pressure for a period of 30 minutes to 8 hours.
Such Process(s), wherein the fly ash catalyses esterification, transesterification and interesterification of the monobasic acid ester and/or polybasic acid ester; esterification of monobasic acid and/ or polybasic acid; or both depending on the feedstock.
Such Process(s), wherein the amount of fly ash used as a catalyst is in the range of 1 to 30 weight percentage with respect to the feedstock.
Such Process(s), wherein the fly ash comprises of two or more of SiO2, Al2O3, Fe2O3, CaO, MgO and SO3.
Such Process(s), wherein the fly ash comprises of 5 to 12 weight percentage SiO2; 2 to 11 weight percentage Al2O3; 0.50 to 2.0 weight percentage Fe2O3; 35 to 60 weight percentage CaO; 0.40 to 1 weight percentage MgO; 26 to 30 weight percentage SO3.
Such Process(s), wherein the process further comprises of recovering the fly ash from the reaction mixture.
Such Process(s), wherein the recovered fly ash is recycled.
Such Process(s), wherein the process further comprises of separating the fly ash from the reaction mixture; washing and drying the washed fly ash and reusing the fly ash as a catalyst for producing alkyl esters.
Such Process(s), wherein the polyol is selected from ethylene glycol, glycerol, sorbitol, sucrose, xylitol, ascorbic acid, any sugar derivative or combination thereof.
Such Process(s), wherein the molar ratio of the feedstock to polyol is in the range of 1:0.1 to 1:1.2.

INDUSTRIAL APPLICABILITY
The process as described produces variety of alkyl esters in an economically efficient and an environmental friendly manner. As fly ash is a solid catalyst, it can be easily separated from the reaction mixture and re-used thereby eliminating the need of neutralization step and aqueous washes that are associated with use of conventional catalysts. Moreover, fly ash catalyses esterification, transesterification and interesterification of the monobasic acid ester and/or polybasic acid ester; esterification of monobasic acid and/ or polybasic acid; or both depending on the feedstock. Further, the process has several advantages. Firstly, the downstream processing is easier and the fly ash separated from the reaction mixture does not lose its catalytic activity and may be reused as a catalyst, thereby reducing the cost of alkyl ester production. Furthermore, the use of fly ash provides an alternate to the disposal related concerns of fly ash generated in industries. The alkyl esters prepared by the disclosed process have applicability in diverse fields such as plasticizers, lubricants, surfactants, emollients, opacifiers, and pearling agents. Such alkyl esters are also used as one of the ingredients in various cosmetics.