WO2005052103A1

WO2005052103A1 - An improved process for the preparation of bio-diesel

Info

Publication number: WO2005052103A1
Application number: PCT/IB2003/005349
Authority: WO
Inventors: Kandukalpatti Chinnaraj Velappan; Subramani Saravanan; Nagarajan Vedaraman; Paruchuri Gangadhar Rao
Original assignee: Council Of Scientific And Industrial Research
Priority date: 2003-11-24
Filing date: 2003-11-24
Publication date: 2005-06-09
Also published as: US20050108927A1

Abstract

A process is disclosed for the preparation of biodiesel, whereby oil is subjected to catalytical transesterification, settling, separation, bubble washing and micro filtration at controlled conditions of temperature and turbulence. The process enables production of high quality fuel, termed as biodisel, within a period of as low as 50 hrs. The fuel can be used without blending with any conventional fuel.

Description

AN IMPROVED PROCESS FOR THE PREPARATION OF BIO-DIESEL Field of the invention:

The present invention relates to an improved process for the preparation of bio-diesel. It has enormous potential application in automobile industry as a substitute fuel for diesel. Background of the invention:

Biodiesel has of late been recognized as an efficient fuel substitute. As reported by Anjana Srivastava and Ram Prasad (Renewable & Sustainable Energy Reviews - 4, 2000, pi 11- 133,) renewable sources such as vegetable oils, animal fats and used cooking oils are normally used as the starting material for preparing this alternate source of fuel. There are also reports that, the engine problems due to carbonization of combustion chamber and wax deposits & engine failure.

As reported by Gerhard Vellguth (Society of Automobile Engines No. 831358 , 1983 ), the fuel injector modifications are needed in standard diesel engines while using vegetable oil as a fuel , otherwise forms deposits on the injectors and in the cylinder head, leading to poor performance, higher emissions and reduces engine life. This limitation has to some extent been resolved by way of transesterification.

Reference may be made to Antolin et al., (Bioresource Technology 83, 2002, pi 11-114), who transesterified sunflower oil with methanol at a temperature in the range of 40-70 °C under constant stirring for a period of 2-6 hrs. Similar efforts have been made by different research groups to prepare biodiesel from multiple oil sources. As reported by Alcantara et al., (Biomass Bioenergy 18,p515-527,2000) several oils such as soybean, frying oil, tallow have been tried as substitutes for diesel. As reported by idyan and Shyoukh (Bioresource Technology 85, p253-256,2002), palm oil has also been tried as substitutes. Conventionally, biodiesel is prepared from oil by reacting with alcohol using a acid/alkali/enzyme catalyst in the temperature range of 40-80 °C under constant stirring for a period of 2-6 hrs. In order to achieve higher product conversion, 1-3 moles per moles of oil in excess to stoichemetric quantity of alcohol is normally used and the unreacted alcohol is removed in the subsequent process steps. The ester obtained is separated from glycerine by suitable separation process and the ester is washed with mild acid. The product is purified further by evaporation to remove unreacted alcohol and traces of moisture. The final product is normally used in combination with regular petroleum fuels to overcome the viscosity and related problems.. The major limitation associated with all these processes is that the overall product conversion in most of the cases is limited to 60-85% only. Moreover, the temperature range limited up to 60°C results in prolonged time, which may be as high as 6 hrs and thereby enhancing the cost of the process significantly. Another limitation associated with these processes is that the resulting product exhibits higher viscosity compared with conventional petroleum fuels, thereby necessitating it is blending with petroleum fuels for the use in diesel engines. Objects of the invention:

The main object of the present invention is to provide an improved process for the preparation of bio-diesel which obviates the limitations as stated above.

Another object of the present invention is to provide a chemical process for biodiesel with renewable sources of energy.

Still another object of the present invention is to provide a chemical process for biodiesel oil preparation from extracted from agricultural edible and non-edible products. Yet another object of the present invention is to provide an environmentally friendly fuel. Still yet another object of the present invention is to provide an improved quality of biodiesel can be used with out any alteration in the diesel engine.

Accordingly the present invention provides an improved process for the preparation of biodiesel, which comprises i) heating oil, characterized by specific gravity in the range of 0.85 - 0.96 and iodine value not exceeding 208, to a temperature not exceeding 120°C for not less than 2hrs followed by transesterification with 8 to 42% w/w, of alcohol of general formula R-OH, where R represents (C_nH _n+ι), n being any integer between 1 and 5, by known method in presence of not more than 0.55% w/w, of a known catalyst, at a temperature higher than the boiling point of the alcohol but not exceeding 215°C for a period of not less than 30 minutes under continuous turbulent condition to get mixture of ester and glycerol, ii) subjecting the mixture, as formed in step(i) to separation of the esterified oil by known method for a period of not less than 4 hrs followed by conventional purification for a period of not less than 8 hrs. and repeating the process of separation as well as purification in succession for not less than three times to get biodiesel. In an embodiment of the present invention the oil used may be selected from ricebraii oil, cottonseed oil , soybean oil, sunflower oil , castor oil, coconut oil.

In another embodiment of the present invention the alcohol used may be selected from methanol, ethanol, n-propanol, n-butanol, n-pentanol In yet another embodiment of the present invention the catalyst used may be selected from sodium hydroxide, potassium hydroxide.

In still another embodiment of the present invention, the lαiown method of separation used may be such as decanting, centrifuging, gravity separation, settling.

In yet another embodiment of the present invention the conventional method of purification used may be selected from bubble washing involving bubble size of l-3mm, micro filtration with not less than 5micron filter, centrifuging, either alone or in any combination.

In still another embodiment of the present invention, the Reynolds number (N _e) used for maintaining turbulence may be adjusted at not less than 4000 irrespective of the type of reactor.

The process of the present invention is described below in detail.

Oil having specific gravity in the range of 0.85 - 0.96 and iodine value not exceeding 208 is heated to a temperature not exceeding 120°C for not less than 2hrs and is transesterified using 8 to 42% w/w, of alcohol of general formula R-OH, where R represents (C_nH_2n+ι) , n being any integer between 1 and 5, by lαiown method in presence of not more than 0.5% w/w, of a known catalyst, at a temperature higher than the boiling point of the alcohol but not exceeding 215°C for not less than 30 minutes under continuous turbulent condition at rpm in the range of 100-150 to get a mixture of ester and glycerol. The Reynolds number

(N_Re) is maintained at not less than 4000 irrespective of the type of the reactor. The mixture of ester and glycerol is subjected to separation by lαiown method for a period of not less than 4 hrs and the top layer ester is purified by conventional method for a period of not less than 8hrs. The process of separation as well as purification is repeated for not less than three times in succession to get biodiesel.

The inventive step of the present invention lies not only in selecting the temperature of transesterification at higher than the boiling point of the alcohol while not exceeding

215°C,but also in maintaining turbulence monitored by adjusting the Reynolds number

(N_Re) at not less than 4000 irrespective of the type of the reactor, to ensure about 97% conversion of the oil into ester within a period of as low as 30 minutes, thereby enhancing the formation of fuel properties in the resulting product called biodiesel. The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention. . Example 1

100 ml of rice bran oil having a moisture content of 3% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%o. This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 20ml of methanol was taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system was maintained at turbulent condition by stirring at 100 rpm in order to maintaining the Reynolds number (N_RJ.) at the minimum of 4000. The reaction was continued for 30 minutes. The excess methanol of 4 ml used for above reaction was later is recovered.

The resulting solution was taken in separating funnel, and two layers were found to form.

The mixture was allowed to settle for 4 hrs and the top layer was taken for further processing.

This was then subjected to bubble washing by aeration with 15ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored. 97% of rice bran oil was estimated to has been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines. The emission properties of this biodiesel were found to be better than of the conventional fuels. Example 2 100 ml of rice bran oil having a moisture content of 3% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%.

This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 32ml of propanol as taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (N_Re) at the minimum of 4000. The reaction was continued for 30 minutes. The excess methanol of 7 ml used for above reaction was later is recovered by the special recovery system.

This was then subjected to bubble washing by aeration with 25ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored. 95% of rice bran oil was estimated to has been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines. The emission properties of this biodiesel were found to be better than of the conventional fuels. Example 3 100 ml of sunflower oil having a moisture content of 1.5% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%.

This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 40 ml of butanol was taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (N_Rβ) at the minimum of 4000. The reaction was continued for 30 minutes. The excess butanol of 8.3 ml used for above reaction was later is recovered by the special recovery system. The resulting solution was taken in separating funnel, and two layers were found to form. The mixture was allowed to settle for 4 hrs and the top layer was taken for further processing.

This was then subjected to bubble washing by aeration with 15ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored. 98.0% of sunflower oil was estimated to have been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines. The emission properties of this biodiesel were found to be better than of the conventional fuels. Example 4 200 ml of coconut oil having a moisture content of 2% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%.

This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 47 ml of methanol was taken in a beaker and lgm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (N_Re) at the minimum of 4000. The reaction was continued for 60 minutes. The excess methanol of 10 ml used for above reaction was later is recovered by the special recovery system. The resulting solution was taken in separating funnel, and two layers were found to form. The mixture was allowed to settle for 8 hrs and the top layer was taken for further processing.

This was then subjected to bubble washing by aeration with 15ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored.

98.0% of coconut oil was estimated to have been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines. The emission properties of this biodiesel were found to be better than of the conventional fuels . Example 5 100 ml of coconut oil having a moisture content of 2% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%. This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 35 ml of ethanol was taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (N _e) at the minimum of 4000. The reaction was continued for 45 minutes. The excess ethanol of 8 ml used for above reaction was later is recovered by the special recovery system. The resulting solution was taken in separating funnel, and two layers were found to form. The mixture was allowed to settle for 8 hrs and the top layer was taken for further processing.

97.0% of coconut oil was estimated to have been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines. The emission properties of this biodiesel were found to be better than of the conventional fuels. Example 6 100 ml of sunflower oil having a moisture content of 1.5% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%. This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 20 ml of methanol was taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (NR_β) at the minimum of 4000. The reaction was continued for 30 minutes. The excess methanol of 4 ml used for above reaction was later is recovered by the special recovery system.

The resulting solution was taken in separating funnel, and two layers were found to form. The mixture was allowed to settle for 4 hrs and the top layer was taken for further nrocessinε. This was then subjected to bubble washing by aeration with 15ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored.

98.0% of sunflower oil was estimated to have been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines.The emission properties of this biodiesel were found to be better than of the conventional fuels. Example 7

100 ml of sunflower oil having a moisture content of 1.5% was heated at 120° C for a period of 2 hrs. Later the moisture content of the oil was found to be 0.5%. This oil was taken in the specially modified batch Continuous Stirred Tank Reactor (CSTR) with provision for alcohol recycle/recovery system, condenser, thermometer and feeding funnel. 25 ml of ethanol was taken in a beaker and 0.5gm sodium hydroxide was added to it under continuous stirring. The resulting solution was then added to the reactor rapidly. The reactor system maintained at turbulent condition by stirring at 100-rpm in order to maintaining the Reynolds number (N_Re) at the minimum of 4000. The reaction was continued for 30 minutes. The excess ethanol of 8ml used for above reaction was later is recovered by the special recovery system.

This was then subjected to bubble washing by aeration with 15ml of distilled water for a period of 8 hrs and the resulting material was allowed to settle for 8hrs. It was taken for micro filtration to remove the micro particles present in the product. The bubble washing, settling and filtration operations were repeated for two more times to attain improved fuel properties. The resulting biodiesel was stored. 98.0% of sunflower oil was estimated to have been converted into biodiesel, which was found to meet the specifications of conventional petroleum fuel. The biodiesel was used for running a test engines.The emission properties of this biodiesel were found to be better than of the conventional fuels. Emission Analysis of Diesel. Biodiesel and Various Blends

Note: BS- Blended with Diesel BSl- B20, BS2- B80, BS3-B50, BS4-B40, BS5- B60 OIL SPECIFICATION Specific gravity 0.916-0.912 Refractive .Index 1.470-1.473 Iodine value 99-108 Saponification value 181 - 189 Acid value 4 - 120 Titer 24 - 28°c Unsaponifiable matter 3.5 % Tocopherols average 400 mg/kg ofoil Fuel properties

Engine Efficiency

A comparative study of the Complete specification relating to P03ce04 ( an improved process for the preparation of bio-diesel) and the US patent No. 6,015,440 apparently reveals the following differences.

In our opinion, the inventive step of the present invention vis-a-vis the aforesaid US Patent document, however, essentially lies in conducting the reaction at a temperature higher than the boiling point of the alcohol used, besides maintaining the turbulence (N_Re = 4000 or more), that is applicable irrespective of the type of the reactor used, to enhance the fuel properties of the resulting product. This step ensures that no blending, as described in the US Patent document.

Following are some of the advantages of the present invention :

1. The high temperature with turbulent condition (Reynolds number more than 4000), reduces the reaction time significantly.

2. The special provision in the reactor enables the effective recovery of excess alcohol added for the reaction.

3. Bubble washing and micro filtration achieved the high quality of the biodiesel.

4. The product is based on renewable source.

5. The product can be used as substitute fuel for diesel engines without any major modification of engines. 6. The final product is a substitute fuel for diesel without blending with other conventional petroleum fuels.

7. The products fuel properties and the engine efficiency are comparable with normal diesel engine fuels.

8. The emission characteristics are like those of normal fuels.

Claims

Claims:

1. An improved process for the preparation of bio-diesel, which comprises i) heating oil having by specific gravity in the range of 0.85 - 0.96 and iodine value not exceeding 208, to a temperature not exceeding 120°C for not less than 2hrs followed by transesterification with 8 to 42% w/w, of alcohol of general formula R-OH, where R represents (C„H _n+ι), n being any integer between 1 and 5, in presence of not more than 0.55% w/w, of a catalyst, at a temperature higher than the boiling point of the alcohol but not exceeding 215°C for a period of not less than 30 minutes under continuous turbulent conditions to obtain a mixture of ester and glycerol, ii) Subjecting the mixture, as formed in step (i) to separation of the esterified oil for a period of not less than 4 hrs followed by purification for a period of not less than 8 hrs. and repeating the process of separation as well as purification in succession for not less than three times to obtain biodiesel.

2. A process, as claimed in claim 1 wherein the oil is selected from ricebran oil, cottonseed oil , soybean oil, sunflower oil , castor oil, coconut oil.

3. A process, as claimed in claim 1, wherein the alcohol is selected from methanol, ethanol, n-propanol, n-butanol, and n-pentanol

4. A process, as claimed in claim 1 wherein the catalyst is selected from sodium hydroxide, potassium hydroxide.

5. A process, as claimed in claim 1 wherein the esterified oil is separated by decanting, centrifuging, gravity separation, settling, either alone or in any combination.

6. A process, as claimed in claim 1 wherein the purification of the mixture is by bubble washing involving bubble size of l-3mm, micro filtration with not less than 5micron filter, centrifuging, either alone or in any combination.

7. A process, as claimed in claim 1 wherein the Reynolds number (N_Re) for maintaining turbulence is adjusted at not less than 4000 irrespective of the type of reactor.