WO2013114381A1

WO2013114381A1 - Two stage process of producing fatty acid esters from palm fatty acid distillate (pfad) using acid chloride route for biodiesel

Info

Publication number: WO2013114381A1
Application number: PCT/IN2012/000199
Authority: WO
Inventors: Venkata Sudhakar Edupuganti
Original assignee: Venkata Sudhakar Edupuganti
Priority date: 2012-01-30
Filing date: 2012-03-26
Publication date: 2013-08-08

Abstract

The saturated fatty acids obtained from the hydrophilization (2) of Palm Faty Acid Distillate are heated in mixing tank (4) with agitation and under vacuum at 120 degree centigrade for one hour. Then it is pumped into reactor (5) and cooled to room temperature and a chlorinating agent is added and the reactor contents are heated up to 60 degree centigrade for two hours. The formed saturated fatty acid chloride is transferred into an acid chloride reactor (7) containing alcohol from. The evolving hydrogen chloride gas converted to alcoholic HCL by bubbling through alcohol react with the unsaturated fatty acids in a reactor (13) under constant agitation and heated at reflux for two hours to obtain the unsaturated fatty acid esters. The same is neutralized with calcium carbonate or calcium oxide in reactor (14) and the unsaturated fatty acid esters is filtered out which can be used as Biodiesel.

Description

TWO STAGE PROCESS OF PRODUCING FATTY ACID ESTERS FROM PALM FATTY ACID DISTILLATE (PFAD) USING ACID

CHLORIDE ROUTE FOR BIODIESEL

TECHNICAL FIELD The present invention relates to a two stage process of producing fatty acid esters from Palm Fatty Acid Distillate (PFAD) which is a byproduct of palm oil refining, using acid chloride route for Biodiesel. More particularly, the present invention relates to a method of producing biodiesel having excellent low temperature fluidity by separating palm fatty acid into C16 and C18 fractions and converting the C16 fraction which is poor in low temperature fluidity into raw material for alkyl ester sulphonates.

BACKGROUND OF THE INVENTION

It is estimated that the world may run short of fossil oils by the year 2044, in less than forty years at the present rate of consumption (Drewette and Dwyer, 2005). Biodiesel is one of the current favorites to be used in the next generation as diesel fuel. Hence Biodiesel is an alternative fuel for diesel engines produced by transesterification of oils and fats, which are also used in human diet. Since there is a chronic shortage of edible oils in India producing biodiesel from oils is not economical and other raw materials which are inedible should be used. One such raw material which is available in sufficient volumes and at a comparatively low price than vegetable oil is palm fatty acid distillate (PFAD), which is a byproduct of palm oil refining. PFAD can be converted into fatty acid alkyl esters (biodiesel) by reacting it with alcohol. These organic esters are termed as biodiesel. Biodiesel is nontoxic, biodegradable and renewable alternative to conventional diesel fuel produced from petroleum crude oil. Biodiesel also produces lower emissions One of the draw backs associated with biodiesel is its gelling at low temperatures such as those commonly encountered in north India during winter due to the presence of high amounts of saturated fatty acids. The typical composition of PFAD is myristic acid C 14, 1.0%, palmatic acid C 16,43.5%, Stearic acid C 18, 4.3%, Oleic acid C18:1 ,36.6%, linoleic acid C 18:2, 9.1 %, others, 5.5%. As can be seen from the above statistics palm fatty acid distillate contains approximately 50:50 ratios of saturated and unsaturated fatty acids. The saturated fatty acids mainly palmitic and stearic acids must be separated from unsaturated fatty acids mainly oleic and linoleic acids to obtain biodiesel with good cold flow properties. For example methyl palmitate (016:0) has a pour point of 30-32 degree centigrade, methyl stearate (018:0) has a pour point of 37-41 degree centigrade, methyl oleate (018:1 ) has a pour point of -20 degree centigrade, Methyl linoleate (018:2) has a pour point of -35 degree centigrade. Symbols, such as, 018:0, 018:1 , etc are expressions of fatty acids. For example, 018:1 represents a fatty acid consisting of 18-carbon atoms with one double bond. It should be noted from the above, that to obtain good cold flow properties one has to separate saturated fatty acids from unsaturated fatty acids. To improve the low temperature characteristics mentioned earlier, pour point depressants are normally employed. The pour point depressants help the fuel to move freely. Although these additives can be blended into the fuel they are expensive. To obtain biodiesel with better cold flow characteristics one has to remove the saturated fatty acid fraction from palm fatty acid distillate.

A lot of work has been done by many researchers to bring out process to manufacture Biodiesel from Palm Fatty Acid Distillate. Some of the draw backs in the existing process are its high plant & equipment cost and its operative expenditure. The catalyst used in the process is also expensive. Most of the prior art process use external catalysts, which are dangerous to handle and also involve long reaction time. Similarly many a time use excess of alcohol which has to be recovered and reprocessed, costing added investment and operative expenditure.

Patent application WO 2008/093990 describes a method for making biodiesel with good low temperature performance from palm oil. But palm oil is expensive that PFAD and here the process uses traditional transesterfication reaction to produce biodiesel and uses a vacuum fractionator to separate saturated fractions from unsaturated ones. The saturated C 16 methyl ester is used to make paraffin mixture.

Da Silva et.al uses heteropolyacid as a catalyst for the esterification of free fatty acids. This process uses a large excess of alcohol (155:1 mmoles) to esterify oleic acid. The alcohol has to be recycled and distilled for further use. The catalyst used in the process is expensive. This process uses external catalysts which are dangerous to handle and long reaction times and also an excess of alcohol which has to be recovered and reprocessed. WO./2011/033346 relates to a process for conversion of low cost and high free fatty acid (FFA) oils to biodiesel in the presence of macro reticular and gel type acidic heterogeneous resin followed by transesterification in presence of homogeneous basic catalyst and separation of biodiesel and glycerine. Further the present invention describes a process for converting high free fatty acid containing feed stocks( FFA 20-85 %) like palm fatty acid distillate (PFAD), restaurant grease, waste cooking oil, Soya deodistillate, acid oil, jatropha curcas oil, mohua oil etc. to biodiesel, which involves esterification of FFA containing oil with lower alcohols like methanol, ethanol, propanol etc. in presence of macro reticular and gel type acidic heterogeneous resin as catalyst to bring down acid value in the range of 1-2 mgKOH/g followed by transesterification in presence of homogeneous basic catalyst metal oxides, hydroxides and alkoxides like sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide etc. and separation of biodiesel and glycerine. This process uses external catalysts which are dangerous to handle and long reaction times and also an excess of alcohol which has to be recovered and reprocessed.

WO/2009/047793 relates to an improved process for the preparation of biodiesel from vegetable or animal oils containing high contents of free fatty acids (FFA). Particularly the present invention relates to deacidification of FFA from the crude vegetable oil by liquid-liquid extraction followed by transesterification for the preparation of biodiesel. The present invention provides an improved process for the preparation of biodiesel from crude vegetable oils especially Jatropha (Jatropha curcas) and Karanja {Pongamia pinnata). In the preset invention the bio-active constituents, fatty acids and polar materials are selectively removed from the crude oils by liquid-liquid extraction with a polar solvent into the solvent phase in a non-destructive manner in specially designed equipment either in a batch mode or continuous mode and the oil left as residue is amenable for direct transesterification.

WO/2004/096962 Catalytic process to the esterification of fatty acids present in the acid grounds of the palm in the presence of alcohol to the transformation of the called fatty acids in esters, characterized by the fact that using an acid solid catalyst for thermal stability and Br6nsted-and/or Lewis acidity in the reaction conditions, molar ratios alcohol/fatty acid between 3 and 15, temperatures between 60 and 200°C, pressure higher than or equal to the air pressure, agitation rate between 400 and 1500 rpm. The above process mentioned sometimes use oil which is an expensive raw material uses excess alcohol, high temperatures unit operations excess energy, external catalyst to obtain biodiesel

In view of this, I have come out with a state of the art two stage process for the manufacture of Biodiesel using two stage processes for the production of alkyl ester of fatty acids from Palm Fatty Acid Distillate (PFAD) using acid chloride route.

SUMMARY OF INVENTION

The novel method to produce Biodiesel by two stage process for the production of alkyl ester of fatty acids from Palm Fatty Acid Distillate (PFAD) using acid chloride route is the state of the art process which is very cost effective. As per my invention, it is a process for producing Biodiesel from Palm Fatty Acid Distillate (PFAD) comprising , a) separation of saturated and unsaturated fatty acids by any known process such as hydrophilization b) converting the resultant saturated fatty acid into fatty acid chloride by means of a chlorinating agent c) mixing the fatty acid chloride with an appropriate amount of anhydrous alcohol to give saturated alkyl esters and hydrogen chloride gas d) preparation of alcoholic HCL by absorbing the hydrogen chloride gas resulted in step c) with an anhydrous alcohol e) converting the resultant unsaturated fatty acid obtained in step (a) into esters by reacting with the said alcoholic HCL. f) neutralizing the excess acid from the acidic unsaturated fatty acid esters g) separating the pure unsaturated fatty acid esters by filtration which is capable of using as biodiesel.

And the novelty rests in using alcoholic HCL in-situ generated from esterification of saturated fatty acids for converting unsaturated fatty acids into unsaturated fatty acid alkyl esters, thereby saving in capital expenditure as well as reducing the operating expenditure or unit production cost.

In other words, this is a creative design modification that can increase the production efficiency while reducing the cost for making biodiesels. The biodiesels has not only has huge potential to replace our existing dependence on importing oil, but also make a huge positive impact towards our environment. The advantages that the current invention has over the existing technologies are as follows: a) The modified process uses only in-situ generated catalyst. No external or additional catalyst is required to carry out the process. b) Unsaturated fatty acids can only be converted into fatty acid chloride route by using very expensive chlorinating agents like oxylal chloride, which makes the process economically un viable. On the other hand saturated fatty acids cannot be used in the alcoholic HCL route because they have limited solubility in alcohols. Whereas unsaturated fatty acids are miscible with alcohol in all proportions there by enhancing reaction rates. c) Since it has an in-situ generated catalyst, no additional step is required.

This could tremendously improve the efficiency of the process as well as make it faster.

d) Since no excess alcohol is required for conducting the reaction, this eliminates the need for a distillation column which is huge cost savings. This also eliminates the huge design complications that can emanate from designing and running a distillation column.

e) As in the present invention the raw material is a distilled fatty acid there no issues of glycerol and the problems associated with its purification. f) The saturated alkyl ester fatty acids can be used as a raw material to make alkyl ester sulphonates.

BRIEF DESCRIPTION OF DRAWINGS

Now the invention will be described in more detail with reference to the accompanying drawing. The drawings described are only schematic and are non-limiting. In the drawings, the size of some elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual dimensions. The features of the invention will be better understood by reference to the accompanying drawings which illustrate presently preferred embodiments of the invention. In the drawings:

Fig. 1 A block diagram of the process.

Fig.2 A schematic diagram of a continuous unit for the production of biodiesel from PFAD Fig.3 GC chromatogram Figure of saturated fatty acid mixture mainly consisting of palmitic and stearic acids.

The Fatty acids were treated with thionyl chloride and the required amount of n butanol added to make fatty acid butyl esters. The main peaks shown are butyl palmitate and butyl stearate. The total ester percentage is approximately 94 %.

Fig.4 GC chromatogram of unsaturated fatty acids.

Sixty five percent of technical grade oleic acid is treated with butanolic HCL to give fatty acid butyl esters. The total ester content is approximately 94%. These esters after neutralizing gives biodiesel, with improved cold flow characteristics. DETAILED DESCRIPTION OF THE INVENTION

Palm fatty acid distillate, which is a byproduct of palm oil refining, is first treated in a hydrophilization process to separate saturated fraction from unsaturated fraction. By using a water solution containing a wetting agent, it is possible to separate saturated fatty acid from unsaturated fatty acid. A partly crystallized mixture of fatty acids is mixed with water solution containing a wetting agent. After mixing, the slurry is centrifuged, and a phase separation occurs. The lightest fraction, i.e., the liquid fatty acids, is at the top of the centrifuge tube. Intermediate is a suspension of fat crystals in water solution, and at the bottom is more or less fat free water. What has happened is that the fatty acid crystals are wetted by the water solution and are transferred from liquid oil into the water solution. When this happens oil drops coalesce and the light oil phase can be separated from the heavy suspension of crystals in a water solution by means of centrifugation. US patent 3,052,700 describes such a hydrophilization process in detail. PFAD after hydrophilization yields a saturated fraction containing mainly palmitic acid and the unsaturated fraction contains 65-70% oleic acid,20%linoleic acid and 10% saturated fatty acids.

The saturated fatty acids are heated to a temperature of 120 degree centigrade for one hour to remove traces of water and are cooled to room temperature. A chlorinating agent is added to convert the fatty acid into fatty acid chloride. Any suitable chlorinating agent can be added. For example phosphorous pentachloride, phosphorous trichloride or thionyl chloride can be added. The most preferred chlorinating agent for this purpose is thionyl chloride because of its low cost and ease of handling. Saturated fatty acids are converted into corresponding acid chlorides by heating with an appropriate amount of thionyl chloride at 60 degrees with stirring for two hours. The fatty acid chlorides thus obtained is again mixed with an appropriate amount of anhydrous alcohol with mixing to give saturated alkyl esters and hydrogen chloride gas. The hydrogen chloride gas is passed through another portion of anhydrous alcohol to give alcoholic HCL, which is then mixed with a stoichiometric amount of un saturated fatty acids and heated for two hours at the reflux temperature of the alcohol to give cold tolerant biodiesel after neutralization with calcium carbonate or calcium oxide. Any alcohol may be from the list given below. Methanol, ethanol, isopropyl alcohol, butanol can be selected as the alcohol of choice.

The advantage of the present invention is that it utilizes in-situ generated hydrogen chloride gas to make alcoholic HCL, which is used to make cold tolerant biodiesel from unsaturated fatty acids. Hydrogen chloride gas is costly, difficult to store in cylinders and hence in-situ generated hydrogen chloride gas in the present invention makes the process cost effective and safe. Alcoholic HCL is a very powerful esterification agent for the esterification of unsaturated fatty acids as the unsaturated fatty acids are miscible in alcoholic HCL in all proportions eliminating any mass transfer constraints. Like wise, it is very easy to convert saturated fatty acids into their corresponding fatty acid chlorides using cheap chlorinating agents like thionyl chloride.

One salient aspect of the present invention is that, unsaturated fatty acids are difficult to convert into their acid chlorides. This can only be achieved by using costly chlorinating agent like oxalyl chloride which is not cost effective. On the other hand saturated fatty acids have limited solubility in alcoholic HCL making the use of a co-solvent mandatory.

Both steps of the reaction are performed without any excess alcohol and hence there is no need for recovering the excess and purifying it in a distillation column. More over no external catalysts are used in both steps of the reaction. As in the present invention the raw material is a distilled fatty acid there no issues of glycerol and the problems associated with its purification. Although it is undeniable that biodiesel is a more environmentally benign fuel, its actual production process cannot be classified as a green process. The present invention is an effort in that direction. A lab scale processing to obtain biodiesel as part of the experimental process as per my invention is as under; 53.2 grams (0.2 moles) of a saturated fatty acid containing stearic acid and palmitic acid are heated in a constant temperature oven at 120 degree centigrade for one hour. After cooling the fatty acid mixture 0.22 mole of thionyl chloride (18 ml) is added and the mixture is heated to 60 degree centigrade for two hours with stirring. After cooling to room temperature 0.2 moles (18.3 ml) of n-butanol is added to the obtained fatty acid chloride. After mixing butanol vigorous vapours of hydrogen chloride gas are released which are bubbled through 200 ml of n-butanol giving 0.45 N butanolic HCL. To 20 ml of butanolic HCL 50 grams of sixty five percent technical grade oleic acid is added and heated for one hour at the reflux temperature of butanol to give 97% ester yield. The unsaturated fatty acid ester was mixed with sufficient amount of calcium carbonate / calcium oxide to neutralize excess HCL. The ester yield in the first step was 93% as analyzed by GC.

One of the preferred embodiments under of the present invention is illustrated in the following example with reference to Fig.2 Palm fatty acid distillate is pumped from storage vessel (1 ) to the hydrophilization unit where PFAD is separated into saturated fatty acids and unsaturated fatty acids and stored in vessels (3) and (11 ) respectively. From storage vessel (3) the saturated fatty acids are heated in mixing tank (4) with agitation and under vacuum at 120 degree centigrade for one hour. The saturated fatty acids are pumped into reactor (5) and cooled to room temperature and a chlorinating agent is added and the reactor contents are heated up to 60 degree centigrade for two hours. The formed saturated fatty acid chloride is transferred into an acid chloride reactor (7) where alcohol from storage tank (6) is pumped in to the reactor (7). The evolving hydrogen chloride gas is stored intermittently gas storage tank (10). The fatty acid alkyl esters are stored in storage vessels (8) and (9). The hydrogen chloride gas stored in gas storage tank (10) is bubbled through alcohol present in storage tank (12) to obtain alcoholic HCL. The unsaturated fatty acids present in storage tank (11) are pumped through to reactor (13) to which alcoholic HCL is added from storage tank (12). In Reactor (13) unsaturated fatty acids and alcoholic HCL is agitated and heated at reflux for two hours. The unsaturated fatty acid esters are mixed with calcium carbonate or calcium oxide in reactor (14) until neutral to litmus and the calcium carbonate is filtered off. The unsaturated fatty acid esters are stored in storage tank (15).

The production of biodiesel from PFAD by the state of the art Two stage process of producing fatty acid esters from Palm Fatty Acid Distillate (PFAD) using acid chloride route under our invention makes PFAD more attractive as a raw material. It is found the new approach can reduce the cost of the plant and equipment as well as the unit product cost due to reduced material input cost and maintenance cost. Further it shorten the production time, as the process avoid waste treatment problem, in addition to providing higher %yield and %purity of the product which is having very low melting point that- are cold tolerant.

The amount of readily available PFAD is not insignificant and it presents biodiesel producers with excellent access to a low-cost, non-food source of feedstock. Hence there is a growing interest in biodiesel (fatty acid methyl ester or FAME) because of the similarity in its properties when compared to those of diesel fuels. Hence PFAD is potentially a valuable, low-cost feedstock for the production of biodiesel.

We have brought out the novel features of the invention by explaining some of the preferred embodiments under the invention, enabling the men in the art to understand and visualize our invention. It is also to be understood that the invention is not limited in its application to the details set forth in the above description or illustrated in the drawings. Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described herein above and as defined in the appended claims.

Claims

I claim,

1. A process for producing Biodiesel from Palm Fatty Acid Distillate (PFAD) comprising : a) separation of saturated and unsaturated fatty acids by any known . process; b) converting the resultant saturated fatty acid into fatty acid chloride by means of a chlorinating agent; c) mixing the fatty acid chloride with an appropriate amount of anhydrous alcohol to give saturated alkyl esters and hydrogen chloride gas; d) preparation of alcoholic HCL by absorbing the hydrogen chloride gas resulted in step c) with an anhydrous alcohol; e) converting the resultant unsaturated fatty acid obtained in step (a) into esters by reacting with the said alcoholic HCL; f) neutralizing the excess acid from the acidic unsaturated fatty acid esters; g) separating the pure unsaturated fatty acid esters which are capable of using as biodiesel.

2. A process for producing Biodiesel from Palm Fatty Acid Distillate (PFAD) as claimed in claim 1 comprising: a) separating the Palm fatty acid distillate ( PFAD) into saturated fatty acids and unsaturated fatty acids in a hydrophilization unit (2); b) heating the saturated fatty acids obtained in sep (a) in a mixing tank (4) under agitation maintained under vacuum at 120 degree centigrade for one hour and transferring the hot saturated fatty acids into reactor (5) and cooling to room temperature prior to the addition of a chlorinating agent and subsequently heating the reactor contents up to 60 degree centigrade for two hours; c) transferring the so formed saturated fatty acid chloride into an acid chloride reactor (7) where alcohol is already transferred and allowed to react producing fatty acid alkyl esters and hydrogen chloride gas wherein the evolved HCL gas is stored intermittently in the gas storage tank (10) while the fatty acid alkyl esters are stored in separate storage vessels; d) bubbling the hydrogen chloride so produced in situ through the alcohol present in the storage tank (12) so as to obtain the alcoholic HCL; e) transferring the unsaturated fatty acids into the reactor (13) to which alcoholic HCL is added and carrying out the reaction in a reactor ( 3) kept under agitation and heated at reflux for two hours so as to obtain the unsaturated fatty acid esters; f) mixing the unsaturated fatty acid esters with a base selected from calcium carbonate, calcium oxide in reactor (14) until it is made neutral; g) filtering pure unsaturated fatty acid esters capable of being used as biodiesel from the product obtained in step (f) . A process for producing Biodiesel as claimed in claim 1 wherein, the saturated fatty acid mainly comprises of palmitic acid, stearic acid and mystic acid while the unsaturated fatty acid comprising of oleic and linoleic acid. A process for producing Biodiesel as claimed in claim 1 wherein, the chlorinating agent used in step (b) is selected from phosphorous pentachloride, phosphorous trichloride or thionyl chloride preferably thionyl chloride.

5. A process for producing Biodiesel as claimed in claim 1 wherein, the anhydrous alcohol used in step (d) is selected from Methanol, ethanol, isopropyl alcohol, and butanol.

6. A process for producing Biodiesel as claimed in claim 1 wherein, the in situ produced hydrogen chloride functions as catalyst for the esterifiction οί· unsaturated fatty acids.

7. A process for producing Biodiesel as claimed in claim 1 wherein, the yield is at least 93%.

8 .A process for producing Biodiesel as claimed in claim 1 wherein, the resultant unsaturated fatty acid ester is capable of being used as Biodiesel that are cold tolerant with very low melting point.

9. A process for producing Biodiesel as claimed in claim 1 wherein, the saturated alkyl ester fatty acids obtained in step (c) is capable of being used for making alkyl ester sulphonates.