WO2010020998A2

WO2010020998A2 - A catalyst composition for transesterification of organically/naturally derived oils and fats to produce alkyl esters and process for preparing the same

Info

Publication number: WO2010020998A2
Application number: PCT/IN2009/000426
Authority: WO
Inventors: Sarvesh Kumar; Alex Cheru Pulikottil; Alok Sharma; Mainak Sarkar; Vivekanand Kagdiyal; Anil Yadav; Ajay Kumar Arora; Suresh Kumar Puri; Mitra Bhanu Patel; Manoranjan Santra; Rakesh Sarin; Brijesh Kumar; Anurag Ateet Gupta; Biswajit Basu; Ravinder Kumar Malhotra; Anand Kumar
Original assignee: Indian Oil Corporation Limited
Priority date: 2008-07-30
Filing date: 2009-07-27
Publication date: 2010-02-25
Also published as: WO2010020998A3

Abstract

The present invention relates to a heterogeneous catalyst composition(s) for transesterification of organically/naturally derived oils and fats comprising support component, a mixed spinel oxide in conjunction with a mixed metal oxide component. The invention also relates to a process for the preparation of said composition and uses the same for the process of transesterification of organically/naturally derived oils and fats with a suitable alcohol.

Description

A CATALYST COMPOSITION FOR TRANSESTERIFICATION OF

ORGANICALLY/NATURALLY DERIVED OILS AND FATS TO PRODUCE

ALKYL ESTERS AND PROCESS FOR PREPARING THE SAME

Field of the Invention This invention, in general relates to a catalyst composition(s), which is employed for the production of fuel. In particular, the present invention provides a heterogeneous catalyst composition comprising a mixed spinel oxide in conjunction with a mixed-metal oxide, process for preparing said composition and process for producing fuel employing the same. Background of the Invention

The major source for the liquid fuels currently used world over is crude oil. Apart from the constraints of depleting crude oil reserves and its availability, the fuels derived from the crude oil have a considerable impact on the environment due to the presence of high content of impurities such as sulfur, nitrogen, and aromatics. Environmental concerns resulting out of increased fuel consumption worldwide and also with an ever-increasing demand for fuels have encouraged fuel producers to explore alternatively available renewable sources for liquid fuels. For the production of diesel, the interest is focused on vegetable oils and animal fats comprising triglycerides of fatty acids as a renewable source. The long, straight and mostly saturated hydrocarbon chains of fatty acids in the vegetable oils and animal fats correspond chemically to the hydrocarbons present in diesel fuels. However, the neat vegetable oils and animal fats display inferior properties, particularly extreme viscosity, and thus limiting their direct use in production of fuels. Conventional approaches for converting vegetable oils and animal fats into fuels comprise transesterification of triglycerides, which form the main component in vegetable oils and animal fats. By this process, the triglycerides are converted into the corresponding alkyl esters by the transesterification reaction with an alcohol in the presence of basic/acidic homogeneous catalysts.

The alternative diesel range fuels such as biodiesel and green diesel derived from vegetable oils and animal fats are envisaged to have an increasing portfolio in the diesel composition in the near future. Efficient and cost effective processes and catalyst for the transesterification process are essential for commercial utilization of vegetable oil and animal fats as the source for diesel in the coming years.

The triglycerides present in the vegetable oils and animal fats are converted in to the alkyl esters of an alcohol by the transesterfication reactions. The transesterifϊcation reactions proceed through either by an acid catalyzed or a base catalyzed route. The alcohol mostly used for transesterification is methanol although other alcohols like ethanol, propanol and other alcohols could also be used. The alkyl esters other wise termed as biodiesel are then blended with the conventional diesel for the end use. The amount of free fatty acids which varies depending on the nature of the vegetable oils are also converted in to its ester form along with water in the process. However, if the water is not removed it can result in the reformation of the fatty acids.

The catalyst system is required to accomplish the esterification and transesterification reactions at high conversion rate. The severity of the reaction parameters, and requirement of various removal/purification steps of the products are dependent on the nature of the catalyst system used.

Transesterification is conventionally carried out using homogenous catalysts, which could either be an alkaline or an acidic catalyst system. Several patents for the transesterifaction of vegetable oils and animal fats are reported. The process is cumbersome primarily because of the difficulties involved in the separation of product from the catalyst, which involves high production cost. These limitations of using the homogenous catalyst severely restrict the achievement of the desired specifications.

The alkaline catalysts such as hydroxides and/or methoxide of sodium and potassium are most commonly used due to their wide availability and low cost. However, due care has to be taken while using alkaline catalyst system with respect to some parameters like the total Free Fatty Acid (FFA) and the water content. The total FFA should not exceed 0.5 % in order to avoid the soap formation, which results in drastic reduction of the reaction rate. Also, the water content in the alcohol and catalyst should not exceed more than 0.3 % as it promotes hydrolysis of alkyl esters to FFA's and thereby the soap formation tendency.

Although the acid catalyzed reactions, unlike the base catalyzed reactions, are not affected by the FFA content of the feed stock, but their rate of the reactions are significantly slower, by about 4000 times, than the base catalyzed reactions. The homogenous acid catalyzed transesterification therefore requires comparatively longer time for reactions to complete, making the process economically unviable. The acid catalysts such as H₂SO₄, HCl, BF₃, H₃PO₄ and organic sulfonic acids have been used by various groups. Sulfuric acid is most widely investigated acidic catalyst. High molar ratio (30:1) of alcohol to triglycerides is required in order to achieve higher conversion of about 98.4%. Various alcohols such as methanol, ethanol, propanol, butanol and amyl alcohol are reported to be used in the transesterification of oil/fat feed stocks obtained from different sources in presence of homogeneous acidic catalyst. Butanol is found to be more effective compared to propanol followed by ethanol. The increase in temperature and pressure enhances the reaction rate of acid catalyzed transesterification. The side reaction such as alcohol etherification may also occur at harsh conditions such as pressure of about 70 bars and temperature of about 240⁰C. The co-solvent such as tetrahydrofuran is used to counteract the miscibility problem besides; it also enhances the reaction rate dramatically.

The drawbacks associated with the product separation in homogenous catalyst system can be efficiently circumvented using a heterogeneous catalyst system. However, heterogeneous catalyst systems for transesterification of triglycerides and esterification of FFAs have not been exhaustively reported in comparison to the homogenous catalyst system. Different solid catalyst systems such as layered aluminosilicates treated with sulfuric acids, aluminophosphate, hydrous tin oxide, amberlyst-15, envirocat EPZG, natural kaolinite clay, B₂O₃ZZrO₂, sulfated SnO₂, zeolites, molecular sieves such as MCM-41 with metals such as aluminium, zirconium, titanium, tin introduced in the silica matrix, sulfated zirconia (SO₄ZZrO₂), hafanium and zirconium salts, alumina loaded with potassium etc have been reported. Some of the above catalyst systems are adversely affected due to high content of FFAs, while others are deactivated in presence of water, and some are deactivated in presence of both beyond certain threshold levels.

Therefore, a robust heterogeneous catalyst system, having good activity and which can process high content of FFAs in minimum number of steps is required to make the process of fuel extraction economically and commercially viable in comparison to known processes in the art. Description of the Prior Arts

European Patent No. 0924185 discloses a three-stage transesterication process by using a heterogeneous catalyst followed by vacuum distillation at reduced pressure to separate the product. The vacuum distillation used for the separation of the ester is energy intensive and could also deteriorate the residue material due to high temperature. Another European Patent EP-B-O 198 243 discloses a transesterification catalyst, comprising alumina or a mixture of alumina and ferrous oxide. The catalyst works at very low space velocity and also the glycerin generated in the process is far less than that of the theoretical value. It may be that glycerin ethers are formed as reported on US Patent 5,908,946.

English Patent GB-A-795, 573 discloses a zinc silicate as a catalyst for transesterification process. The catalyst is reported to be active in the temperature range of 250 to 280 ⁰C, and a pressure of at least 100 bar, with methanol. The 100 % conversion is achieved in two stages, if glycerin was removed after first stage. However, due to the high temperature, zinc soaps would be formed with the zinc compounds, which cannot be allowed in fuel.

US Patent 5,908,946 discloses a process for production of alkyl ester and high purity glycerin with a catalyst that is selected from among zinc oxide, mixtures of zinc oxide and aluminum oxide, and zinc aluminates. The 90 -95 % conversion is achieved in two-stage process. The glycerin is removed from the ester after first step. The patent also discusses the detrimental effect of the presence of water, which encourages the formation of fatty acids, which may react to form soaps. The references cited in this patent, compare about twenty catalysts, namely zinc chloride, zinc sulfate, zinc powder, barium oxide, calcium oxide, zinc oxide, alumina, thiosalicylic acid, calcium phosphate, potassium bicarbonate, sodium methylate or sodium ethylate, and even lithium hydroxide etc, showing similar performance. All these salts or oxides provide yields of between 32 and 39% of monoglyceride in a comparative test where excess glycerine is used relative to the fatty acid.

US Patent 6,712,867 discloses a transesterification process by using a co- solvent to form a single-phase solution of triglyceride in an alcohol selected from methanol and ethanol. The reaction is carried out below the lower boiling points of the solvent and co-solvent and the co-solvent is removed after the reaction by distillation. Tetrahydrofuran (THF) 1,4-dioxane, diethyl ether, methyl tertiary butyl ether and diisopropyl ether are reported to be used in an amount to effect formation of the single phase and a base catalyst for the esterification reaction.

US Patent 7,145,026 discloses a transesterification process, in a continuous, plug-flow environment using a 7-foot of 3/8" coiled copper pipe with a low residence time of about 10 seconds, single-pass in a temperature range of 80-180 ⁰C and a pressure of 1-30 atm. The coiled copper tubes are coated with metallic catalyst or a caustic and achieve about 70% conversion.

US Patent 7,193,097 describes a process using a third component like carbon dioxide, propane, butane, pentane, and hexane in a super critical or a sub critical state using catalysts sodium carbonate; sodium bicarbonate; titanium aluminum sulfate; and a salt containing titanium, zirconium, and phosphorous.

US Patent 7,122,688 discloses a method to prepare a fatty acid lower alkyl esters from a reaction of vegetable or animal oil, with a lower alcohol using acidic mesoporous silicate as catalyst. In this patent the various acidic mesoporous silicates have been prepared and activities of different acidic catalysts such as H₂SO4, SBA- 15-SO₃H-P 123, Nafion, SBA-15-SO₃H-L64, SBA- 15-ph-SO₃H-P 123, CDAB-SO₃H- C16 have been compared by esterification of palmitic acid in soybean oil.

US Patents 7,138,536 and 6,878,837 disclose a process for producing fatty acid alkyl esters and glycerol from vegetable and/or animal oil and an alcohol, in the presence of a heterogeneous zinc aluminate catalyst. The process requires the control of the water in the reaction medium and is achieved by employing water/methanol separation steps by evaporation steps or through a series of nanofiltration membrane modules, maintained at a pressure close to 6 MPa. Objects and Summary of the Invention

It is a principal object of the present invention to provide a novel heterogeneous catalyst composition suitable for transesterification of organically/naturally derived oils and fats to produce biodiesel.

It is another object of the present invention to provide a highly active and stable heterogeneous catalyst composition for the transesterification of organically/naturally derived oils and fats to produce biodiesel comprising a mixed, spinel oxide in conjunction with metal oxide components with appropriately designed porosity sufficiently tolerant to water.

Further object of the present invention is to provide a process for the preparation of a catalyst composition for transesterification of organically/naturally derived oils and fats to produce biodiesel employing readily available raw materials. Still another object of the present invention is to provide a process for transesterification of organically/naturally derived oils and fats to produce biodiesel, wherein said process employs continuous fixed bed.

A further object of the present invention is to provide a process for transesterification of organically/naturally derived oils and fats to produce biodiesel, wherein the feed stocks used for the process contains water of about 0.5 to 1.0 weight percent.

A further object of the present invention is to provide a process for transesterification of organically/naturally derived oils and fats to produce biodiesel, wherein the production of the biodiesel is enhanced by introducing co-solvents to generate a molecular level contact of the reactant mixture.

The above and other objects of the present invention are further attained and supported by the following embodiments described herein. However, the scope of the invention is not restricted to the described embodiments herein after.

In accordance with one preferred embodiment of the present invention, there is provided a catalyst composition for transesterification of organically/naturally derived oils and fats, said catalyst composition comprising a base component of desired porosity and a reactive component comprising a mixed spinel oxide and a metal oxide.

In accordance with another preferred embodiment of the present invention, there is provided a process for preparing a catalyst composition for transesterification of organically/naturally derived triglycerides, the process comprising of reacting in solid state the mixed spinel oxide and the base component in a grinder to obtain a powder, homogenizing the powder by mulling with a solvent to obtain a mixture, adding an extrusion agent to the mixture, peptizing the resultant mixture with an acid, extruding the peptized material, optionally in the presence of extrusion aiding agents, to obtain catalyst extrudates, drying the catalyst extrudates, calcining the dried catalyst extrudate in a furnace to obtain the catalyst composition. In accordance with another preferred embodiment of the present invention, there is provided a process for transesterification of organically/ naturally derived triglycerides employing the catalyst composition, wherein the process comprises of reacting a mixture of the organically derived triglycerides, an alcohol and optionally a co-solvent in presence of the catalyst composition in a reactor maintained at an appropriate flow rate, pressure, and temperature, collecting effluent stream from the bottom into a decantor attached to the reactor, separating components in the effluent by decantation, wherein the top component comprises alkyl esters and bottom component comprises glycerin. In accordance with a preferred embodiment of the present invention, there is provided a catalyst composition suitable for transesterification of vegetable oil or animal fats to produce biodiesel wherein said composition comprises a mixed spinel oxide preferably in the range of 10 to 50 wt% in conjunction with a mixed metal oxide preferably in the range of 50 to 90 wt% generated by thermal decomposition of clay typically of the bentonite type and/or of a hydrotalcite type.

Detailed Description of the Invention

While this specification concludes with claims particularly pointing out and distinctly claiming that, which is regarded as the invention, it is anticipated that the invention can be more readily understood through reading the following detailed description of the invention and study of the included examples.

Catalyst Composition

High activity heterogeneous catalyst having appropriate porosity is produced by solid-state reactions. The porosity of the catalysts are so designed to accommodate long chain triglycerides of oils and free fatty acids to convert them to alkyl esters by reacting with an alcohol.

The base component of catalyst is a porous material, which provides the porosity, sufficiently peptizable for extrusion and obtaining strength to the said catalyst. These materials are such as alumina, clay, magnesia, titania or a mixture of two or more of the said base materials, more preferably a clay in the range from about 5 to 30 weight percent and an alumina in the range from about 10 to 40 weight percent. The base component as alumina is a porous gamma alumina having surface area in the range from about 250 to 350 m²/g and having a unimodal pore size distribution. The clay component contains mainly TiO₂, Fe₂O₃, MnO₂, and SiO₂. The clay component also acts as activity enhancer in synergy with the active components. The base component will generally be present in range from about 10 to 50 weight percent. The reactive components of catalyst compositions comprise, a mixed spinel oxide of the form A_xA¹^_-X)B₂O₄ where 'A' is a divalent atom like Ni, Mg, Co, 'A¹' is Zn and 'B' is a trivalent metal atom like Al, and a metal oxide of Ti, Fe, Mg and/or a mixed metal oxide of the form A_xA¹^_x)O where 'A' is a divalent atom like Ni, Sn, Mg, Co and 'A¹' is Zn, or a combination thereof. The value of x may range from 0.05 to 0.95. The reactive mixed spinel oxide of the catalyst is prepared through solid-state reactions of the said metal oxides at the temperature range from about 400 to 650⁰C. The metal oxide and the metal oxide components are generated in situ by the decomposition of the metal salts in a solid-state reaction. The reactive metal oxide component will generally be present in range from about 50 to 90 weight percent. This component is responsible for converting the triglycerides and fatty acid component to alkyl esters.

The mixed spinel oxide generated by a solid state reaction is mixed with the metal salt of the said elements or with a clay containing these elements and is grinded in a ballmill /grinder to generate a powder of fine particles and homogenized by mulling with solvent like water, acetone, and propanol, more preferably with acetone to form a wet solid. The mixture is then mixed with an extrusion agent like pseudoboehmite and/or clay and peptized with dilute acids preferably with nitric acid and/ or by the addition of extrusion aiding agents like polyvinyl alcohols, polyethylene glycols or carboxyl methylcellulose prior to extrusion. The extrudates of the catalyst are then dried at room temperature overnight followed by drying in a furnace at about 100 to 200 ⁰C temperature for about 4 to 12 hrs. The dried catalyst is then calcined in a furnace at about 200 to 600 ⁰C temperature for about 4 to 12 hrs. The final catalyst comprises of surface area ranging from 50 to 150 m²/gm, pore volume ranging from 0.1 to 0.6 cc/gm and average pore size ranging from 50 to 200 A⁰.

The transesterification process is carried in one or more numbers of fixed bed reactors, in the temperature range of about 150 ⁰C to 250 ⁰C, pressure in the range of about 50 to 90 bar, alcohol to oil ratio in a range of about 1-3 v/v, Liquid Hourly Space Velocity (LHSV) in the range of 0.5 to 3.0 h^'1 _. The reaction product was distilled in an atmospheric column to separate the alcohol and co-solvent, which were collected by condensing the stream from the column top and recycled. After separating the glycerin component from the bottom product of the column, it is admixed with alcohol and co-solvent again and sent to second stage of the reaction to achieve the complete conversion. The alcohol used in the process herein is preferably selected from the alcohols having carbon chain of Ci to C₆. The product from the second stage reaction is sent to another atmospheric column to separate alcohol and co-solvent from the column top. The bottom product from the column is sent to decanter to separate the glycerin component from the bottom and alkyl ester from the top. The products are further treated to achieve required specifications and purity.

Feed Stocks The triglycerides derived from various plants and animals such as jatropha curcas oil, castor oil, sunflower oil, soybean oil, rapeseed oil, cotton oil, corn oil, coconut oil, ground nut oil, olive oil, palm kernel oil, fish oil, lard, tallow etc. may be used. In the present invention the triglycerides derived particularly from non-edible oils available in India such as jatropha curcas oil, castor oil, and karanjia oils have been used.

Reactor System

The experiments were conducted in a high-pressure reactor system. The details of the reactor system are shown in Figure- 1. This reactor system contains two numbers of fixed bed reactors, which can be operated either in series or parallel in up or down flow modes. These reactors are equipped with separate electrical furnaces, which can heat the reactors up to 600 ⁰C. The furnace is divided into seven different zones. The top two zones were used for preheating the feed stream before entering the process zones. The middle three zones were used for process reactions and bottom two zones were used for post heating purposes. Adjusting the corresponding skin temperatures controls the reactor internal temperatures. The separate feed tanks (T-I, T-2) equipped with feed pumps (P-I, P-2) have been provided for oil and alcohol. The oil, alcohol and co-solvent can be admixed and fed to the first reactor (R-I) in down or up flow mode with the help of either of the feed pump (P-I or P-2). The oil and alcohol can also be pumped separately via pumps P-I & P-2 and mixed in a Static Mixer SM-I before entering to R-I. The R-I effluent was sent to separator S-I where gas and liquid streams were separated. The liquid stream from the bottom of S-I was sent to Atmospheric column C-I. The C-I top stream containing mainly alcohol or mixture of alcohol and co-solvent is condensed in Condenser HE-I and recycled to feed tanks T-I or T-2.

A part of the condensed stream is recycled back to the column to achieve the desired separation. The column temperature profile and reflux ratio are maintained in such a way so that desired separation is achieved. The liquid stream from the bottom of C-I mainly containing unconverted oil, alkyl esters, glycerin, and some amount of alcohol and co-solvent is sent to Decanter D-I. The glycerin component separated in the bottom portion of the D-I is collected into a glycerin storage tank T-5. The upper layer of D-I containing unconverted oil, alkyl esters, and some amount of alcohol and co-solvent was sent to Oil Feed Tank (T-3) for R-2. The separate alcohol feed tank (T-4) has been provided for R-2. The alcohol and co-solvent can be admixed with unreacted material into either of feed tank T-3 or T-4 with the help of P-3 or P-4. The oil and alcohol can be pumped separately via pumps P-3 & P-4 from tanks T-3 & T-4 and mixed in a Static Mixer SM-2 before entering to R-2. The R-2 effluent was sent to S-2 where gas and liquid streams were separated. The liquid stream from the bottom of S-2 is sent C-2. The C-2 top stream containing mainly alcohol or mixture of alcohol and co-solvent is condensed in HE-2 and recycled to feed tanks T-3 or T-4. A part of the condensed stream is recycled back to the C-2 to achieve the desired separation. The column temperature profile and reflux ratios are ,maintained in such a way so that desired separation is achieved. The liquid stream from the bottom of C-2 mainly containing alkyl esters, glycerin, and traces of unconverted oil, alcohol and co- solvent is sent Decanter D-2. The glycerin component separated in the bottom portion of the D-2 is collected into a glycerin storage tank T-5. The upper layer of D-2 mainly containing alkyl esters is sent to biodiesel storage tank (T-6). Example- 1

Preparation of Catalyst Catalyst was prepared by solid-state reaction of homogenous mixture of nickel zinc aluminate, clay and alumina in different proportions as detailed in Table 1. Nickel zinc aluminate was prepared through the solid-state reaction of zinc oxide, salt of nickel, like nickel acetate, nickel nitrates, nickel hydroxides, most preferably nickel nitrate and an alumina precursor at a temperature of about 550 - 600⁰C.

The various components of the catalyst were grinded and homogenized using a high-speed planetary ball mill in the desired proportions. Acetone was used to homogenize the component.

The homogenized powder was extruded after peptizing with about 1.0 % nitric acid to form the cylindrical extrudates. The extrudates were then dried at a room temperature of about 30⁰C overnight followed by drying at a temperature of about 120⁰C for about 4-2 hours. The dried catalyst is then calcined at a temperature of about 600⁰C for about 4-12 hours.

Table-1 Composition and Characterization of a Catalyst

* BET is the value obtained for a catalyst and that given in the description is the range that can be obtained if it is made by varying the preparation ranges like temperature and the compositions.

Example-2

Transesterification of Jatropha Curcas Oil with Methanol and Catalyst at 200⁰C temperature and 40 bar pressure:

The Reactor system shown in Figure- 1 was used to conduct the tranesterifiaction of jatropha curcas oil with methanol in presence of the catalyst. The

150 cc of the catalyst of cylindrical pellets of size 2*4 (dia *length) mm was charged into the middle three zone of each of the reactor. The preheating and post heating zones were filled with alumina ball of 3 to 4 mm size. The void space among the catalyst particles was filled with 80-100 mesh size of the inert diluents for proper wetting of the catalyst. Initially the reactors were pressurized with nitrogen gas up to 60 bar pressure. The reactors were heated in ramp @ of 50 ⁰C per hour to achieve the final temperature of 200 ⁰C. The oil and alcohol were fed separately into first stage reactor. After stabilizing the feed to the reactor, the internal reactor temperatures were maintained at isothermal temperature by adjusting the reactor furnace temperatures.

The reaction product was distilled in an atmospheric column to separate the alcohol, which was collected by condensing the stream from the column top and recycled. The column internal temperature profile and reflux ratio were maintained to achieve desired degree of separation. The column bottom product was sent to decanter where glycerin was separated from the bottom layer. The upper layer from decanter mainly containing unconverted oil, alkyl esters, and some amount of alcohol was admixed with alcohol and fed to the second stage reactor. The product from the second stage reaction was sent to another atmospheric column to separate alcohol from the column top.

The bottom product from the column was sent to decanter to separate the glycerin component from the bottom and alkyl ester from the top. The Decanter top product, which contains unconverted vegetable oil (TG & FFAs), intermediates (DG & MG), and alkyl esters (biodiesel), was analyzed by Gel Permeation Chromatography analysis. GPC technique provides separation of components on the basis of molecular weight.

The biodiesel content (conversion) in Decanter top product obtained after first and second stage reactions were 40.8 % and 53.1 % respectively. The definition of conversion is given below:

Area of Biodiesel Peak XlOO

% Conversion =

Area of (Biodiesel + Unconverted Oil/Fat + Intermediates) peaks

TG = Triglycerides FFAs = Free Fatty Acids DG = Diglycerides

MG = Monglycerides

The details of various operating parameters are reported in Table-2. Table-2

temperature and 60 bar pressure:

The experimental conditions of previous experiment were repeated except the addition of co-solvent with reactant material in both the reaction stages. In this experiment jatropha oil, methanol, tetrahydrofuran were mixed into a feed tank before feeding the reactors. Since the boiling point of tetrahydrofuran is close to the boiling point of methanol, hence it was removed from the reactor effluents by distillation with methanol. The details of various operating parameters are reported in Table-3. By adding co-solvent, the molecular contact of reactants increased resulting enhancement of conversion in both the reactors.

Table-3

temperature and 60 bar pressure: The experimental conditions of previous experiment were repeated except the temperature of both the reactors was increased from 200 to 220⁰C. The details of various operating parameters are reported in Table-4. Due to increase in temperature the conversion in both the reactors is improved.

Table-4

Example-5

Transesterification of Jatropha Curcas Oil with Methanol using Co-solvent at 240⁰C temperature and 80 bar pressure: The experimental conditions of previous experiment were repeated except the temperature of both the reactors was further increased from 200 to 240 ⁰C and pressure from 60 to 80 bar. The details of various operating parameters are reported in Table-5. Due to increase in temperature and pressure the conversion of both the reactors is significantly improved.

Table-5

temperature and 80 bar pressure The experimental conditions of previous experiment were repeated except the oil feed was changed from Jatropha Curcas oil to Castor Oil. The details of various operating parameters are reported in Table-6.

Table-ό

80 bar pressure

The experimental conditions of previous experiment were repeated except the oil feed was changed from Castor oil to Lard (animal fat). The details of various operating parameters are reported in Table-7. Table-7

Example 8

Transesterification of Jatropha Curcas Oil with Methanol using Co-solvent at 250 ⁰C temperature 80 bar pressure.

The experimental conditions of previous experiment were repeated except the addition of co-solvent with reactant material in both the reaction stages. In this experiment jatropha oil, methanol, tetrahydrofuran were mixed into a feed tank before feeding the reactors. Since the boiling point of tetrahydrofuran is close to the boiling point of methanol, hence it was removed from the reactor effluents by distillation with methanol. The details of various operating parameters are reported in Table-8. By adding co-solvent, the molecular contact of reactants increased resulting enhancement of conversion in both the reactors.

Table-8

The method as described in this invention is not only advantageous in terms of being economically viable, reducing the demand of crude oil and ultimately lessening the environmental burden due to fuels derived from it. The method of the invention also stands out in providing solution to the problems of the prior art and producing biodiesel, which meets the standard parameters of an ideal fuel. The inventors have tested the performance characteristics of the biodiesel obtained by the method disclosed in the current invention as against the standard norms and found it complying significantly as tabulated in Table 9.

Table 9 As per IS 15607:2005

While this invention has been described in detail with reference to certain preferred embodiments, it should be appreciated that the present invention is not limited to those precise embodiments. Rather, in view of the present disclosure, which describes the current best mode for practicing the invention, many modifications and variations would present themselves to those skilled in the art without departing from the scope arid spirit of this invention.

Claims

We Claim:

I . A catalyst composition for transesterification of organically/naturally derived oils and fats comprising a base component and a reactive component having a mixed spinel oxide and a metal oxide.

2. The catalyst composition according to claim 1, wherein the organically/naturally derived fats and oils are derived from any organic or natural sources including jatropha curcas oil, castor oil, sunflower oil, soybean oil, rapeseed oil, cotton oil, corn oil, coconut oil, ground nut oil, olive oil, palm kernel oil, fish oil, lard or tallow.

3. The catalyst composition according to claim 1, wherein the base component is a porous material selected from a group comprising alumina, clay, magnesia, titania or mixtures thereof.

4. The catalyst composition according to claim 1, wherein the base component in the composition is in a range of about 10 to about 50% w/w.

5. The catalyst composition according to claim 3, wherein the base component is preferably a mixture of the clay and the alumina.

6. The catalyst composition according to claim 5, wherein the clay is in a range of about 5 to 30 % w/w and the alumina is in a range of about 10 to 40 % w/w.

7. The catalyst composition according to claim 5, wherein the clay is comprising preferably of titanium oxide, ferric oxide, manganese dioxide or silicon dioxide or mixture thereof.

8. The catalyst composition according to claim 5, wherein the alumina is a porous gamma alumina having surface area preferably in a range from about 250 to about 350 m²/gm and unimodal pore size distribution.

9. The catalyst composition according to claim 1, wherein the reactive component in the composition is preferably in a range from about 50 to 90% w/w.

10. The catalyst composition according to claim 1, wherein the mixed spinel oxide is having formula A_xA¹^_-X)B₂O_4, wherein A is a divalent metal atom; A¹ is Zn; B is trivalent metal atom and x is having a value in a range preferably from about 0.05 to 0.95.

I I. The catalyst composition according to claim 1, wherein the reactive component is prepared in situ by reacting a metal salt of the divalent metal atom and oxides of Zn and the trivalent metal atom in solid state at a temperature preferably between 400 to 65O⁰C.

12. The catalyst composition according to claim 1, wherein the metal oxide is an oxide of metal selected from tin, iron and magnesium.

13. The catalyst composition according to claim 1, wherein the catalyst composition is having surface area preferably in a range from about 50 to 200 m /gm.

14. The catalyst composition according to claim 1, wherein the catalyst composition is having pore volume preferably in a range from about 0.1 to 0.6 cc/gm.

15. The catalyst composition according to claim 1, wherein the catalyst composition is having average pore size preferably in a range from about 50 to 200A°.

16. The catalyst composition according to claim 1, wherein the composition optionally comprises a mixed metal oxide.

17. The catalyst composition according to claim 16, wherein the mixed metal oxide is having formula A_xA¹^_-X)O, where A is divalent metal atom; A¹ is Zn; B is a trivalent metal atom and x is having a value preferably in a range from about 0.05 to 0.95.

18. A process for the preparation of the catalyst composition of claim 1 for transesterification of organically derived triglycerides, the process comprising: a) reacting in solid state the mixed spinel oxide and the base component in a grinder to obtain a powder; b) homogenizing the powder by mulling with a solvent to obtain a mixture; c) adding an extrusion agent to the mixture; d) peptizing the mixture of step (d) with an acid; e) extruding the peptized material, optionally in the presence of extrusion aiding agents, to obtain catalyst extrudates; f) drying the catalyst extrudates, and g) calcining the dried catalyst extrudate to obtain the catalyst composition.

19. The process according to claim 18, wherein the solvent is selected from a group consisting of water, acetone or propanol or a mixture thereof, preferably acetone.

20. The process according to claim 18, wherein the extrusion agent is preferably pseudoboehmite.

21. The process according to claim 18, wherein the acid is selected from dilute nitric acid and acetic acid.

22. The process according to claim 18, wherein the extrusion aiding agents is selected from a group consisting of polyvinyl alcohol, polyethylene glycol and carboxymethyl cellulose.

23. The process according to claim 18, wherein the drying is carried out for 4 to 12 hours in a furnace at a temperature preferably in a range from about 100 to 200⁰C.

24. The process according to claim 18, wherein calcining the dried catalyst extrudate is carried for about 4 to 12 hours in a furnace at a temperature in a range from about 200 to 600⁰C.

25. A process for transesterification of organically/naturally derived fats and oils employing the catalyst composition of claim 1, the process comprising the steps of: a) reacting a mixture of the organically derived triglycerides, an alcohol and optionally a co-solvent in presence of the catalyst composition in a reactor maintained at an appropriate flow rate, pressure, and temperature; b) collecting effluent stream from the bottom into a decantor attached to the reactor; c) separating components in the effluent by decantation, wherein the top component comprises alkyl esters and bottom component comprises glycerin.

26. The process according to claim 25, further comprising collecting effluent stream from top of the reactor and distilling the condensed stream to separate the alcohol and the co-solvent.

27. The process according to claim 25, wherein the component comprising the alkyl esters is further mixed with the alcohol and optionally the co-solvent and recycled into the reactor of step (a).

28. The process according to claim 27, wherein the reactor is a fixed bed reactor having: a. an upper zone loaded with alumina; b. a middle zone containing the catalyst composition wherein the reaction is performed; and c. a bottom zone loaded with alumina.

29. The process according to claim 25, wherein the ratio of the alcohol to organically/naturally derived fats and oils in the mixture is in a range of about 1-10 v/v, preferably between 1-3 v/v.

30. The process according to claim 25, wherein the alcohol used in the process is having carbon chain of Cjto C₆.

31. The process according to claim 25, wherein the pressure is preferably in the range from about atmospheric to 90 bar, more preferably between 50 to 90 bar.

32. The process according to claim 25, wherein the ratio of co-solvent to alcohol is in the range from about 1 to 5% v/v, preferably 1 to 2% v/v.

33. The process according to claim 25, wherein the temperature is in the range from about 50⁰C to 250⁰C.

34. The process according to claim 25, wherein the flow rate of the mixture in the reactor is in the range from about 0.5/h to 5.0/h, preferably between 0.5/h to 1.5/h.