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The most used method for biodiesel production is the transesterification of the fatty acids from vegetable oils with methyl alcohol. A high toxicity, a low flash point, the harmful irreversible effects over the human wellness, makes that use of methyl alcohol for biodiesel synthesis to be less desired. In our surveies we investigate the possibilities of methyl alcohol with ethanol replacing in the transesterification of fatty acids from vegetable oils procedure and development of the separation method of ethylester from glycerin, every bit good as alteration of the reaction parametric quantities ( temperature, force per unit area, stirring velocity, volumetric velocity ) , in order to optimise the procedure.

Keywords: biodiesel, bioethanol, transesterification

Introduction

Harmonizing to the European directive 2003/30/EC all members of EU must replace at 1.01.2010, 5.75 % from the Diesel fuel green goodss by oil with biodiesel. The international criterions define that the biodiesel is obtained merely by transesterification of vegetable oils and of carnal lubricating oils with low intoxicants ( methyl alcohol, ethyl alcohol, n-propanol, n-butanol ) or iso-aliphatics ( glycols and benzoic ) , catalyzed by ( Na or K hydrated oxide ) , acids or enzymes. Presents, the best transitions in biodiesel are achieved by triglyceride from vegetable oils transesterification with methyl alcohol, catalyzed by K hydrated oxide [ 1 ] . Use of methyl alcohol for transesterification has the consequence a non ecological biodiesel because the methyl alcohol is non produce by renewable natural stuffs. In order to bring forth an ecological biodiesel, we propose to replace the classical synthesis method with transesterification of triglyceride from vegetable oils with ethanol green goodss by renewable natural stuffs.

Although ethanol signifiers azeotrope with H2O, and the separation of glycerin by ethyl ester is really hard, in our probes we attempt to extinguish most of the jobs that can take topographic point at permutation of methyl alcohol with ethyl alcohol hence, we propose a method for interrupting the emulsion formed after transesterification by presenting of a demulsify agent. Harmonizing to our old surveies we observed that by presenting the demulsify agent into the reaction system at temperatures between 50-60 & A ; Acirc ; & A ; deg ; C, under vigorous agitation for 5 hours, the separation of the esters by glycerin become elementary [ 1, 2 ] .

Experimental survey

In our survey the esters were synthesized by transesterification of triglycerides from sunflower oil. For comparing we prepared methyl ester and ethyl ester harmonizing to a method presented below [ 2 ] .

Fatty acid methyl esters synthesis

Methyl ester

Transesterification of the fatty acylglycerols bing into the sunflower oil was realized in a batch reactor utilizing potassium hydrated oxide as accelerator via a method given elsewhere [ 3-6 ] . The reaction was carried out at 60 & A ; Acirc ; & A ; deg ; C, atmospheric force per unit area for 2 hours under vigorous agitation in order to accomplish the maximal transition. In order to obtain the fatty methyl ester by transesterification we used 100 % extra methyl alcohol, maintaining the grinder ratio sunflower oil to methanol 1:6 and the accelerator concentration of 1 % .

The petroleum methyl ester was separated by glycerin by gravitation and the accelerator was eliminated by hot H2O lavation.

triglyceride intoxicant ester glycerin

Ethyl ester

Transesterification of sunflower oil in the presence of ethyl alcohol was carried out in similar conditions as methyl ester synthesis. The reaction conditions were 60 & A ; Acirc ; & A ; deg ; C, atmospheric force per unit area for 5 hours under vigorous agitation, K hydrated oxide accelerator, the ratio between sunflower oil and intoxicant was 1:6. In order to better the separation between the ester and glycerin, 1wt % of a demulsify agent ( related to intoxicant ) was added at the beggary of transesterification procedure into the reaction mixture.

Mixture of esters

1:1 methanol-ethanol molar ratio was used for transesterification of sunflower oil, maintaining the ratio between vegetable oil and intoxicant at 1:6. The transesterification took topographic point in the same reactor antecedently used for methyl and ethyl esters synthesis. The intoxicant mixture together with sunflower oil was heated up to 60 & A ; Acirc ; & A ; deg ; C at atmospheric force per unit area under energetic stirring for 5 hours. The separation of glycerin from esters was done as antecedently mentioned.

The intoxicants used in our probe ( anhydrous methanol 99.8 % and ethanol 99.9 % ) were provided by Sigma-Aldrich.

The chemical composing of sunflower oil is given in table 1. After readying, the methyl ester, ethyl ester and mixture of esters were characterized from viscousness, denseness, prurience and refraction index points of position ( table 2 ) .

Table 1. The chemical composing of sunflower oil

Fatty acids

Symbol

Sunflower oil,

wt %

Lauric acid

12:0

Miristic acid

14:0

Palmitic oil

16:0

5.5

Stearic acid

18:0

5.2

Oleic acid

18:1

24.3

Linoleic acid

18:2

64.5

Linolenic acid

18:3

Table 2. Physical-chemical features of sunflower oil, methyl ester and ethyl ester

Features

Sunflower oil

Methyl ester

Ethyl ester

Mixture of esters

Kinematicss Viscosity at 40oC, Central Time

32.46

4.67

4.20

4.31

Density,

0.9176

0.8791

0.8752

0.8771

Prurience, ( HFRR trial ) ,

117

209

183

198

Refraction index

1.4732

1.4559

1.4542

1.4551

Consequences

Biodiesel output probes

In order to look into the output of biodiesel obtained by transesterification of fatty acids in vegetable oils in the presence of different intoxicants.

Refering the ethyl alcohol, it is good known that signifiers azeotrope with H2O that complicate the recovery procedure and use of the ethyl alcohol into the transesterification procedure leads to an emulsion which makes hard the separation of ethylic esters by biodiesel.

The old surveies we realized, proved promising consequences and consists in infixing into the system of a demulsify agent that inhibit the formation of emulsions from ethyl ester and glycerin produced in the procedure. Therefore, before transesterification, a demulsify agent ( 1:10 demulsify agent-sunflower oil grinder ratio ) was introduced into the reaction system in order to increase the solubility of the glycerin produces in transesterification procedure. The biodiesel output obtained by transesterification on presence of different intoxicants is presented in table 3.

Table 3. Biodiesel output obtained by transesterification on presence of different intoxicants

Methyl ester

Mixture of methyl and ethyl esters

Ethyl ester

Biodiesel output

94.6

66.7

44.20

Unfortunately, foremost attempts lead us to a much lower ester yield than obtain in transesterification procedure with methyl alcohol.

Decisions

In this paper, the research lab experiments were conducted to bring forth biodiesel by transesterification of sunflower oil in presence of methyl alcohol, ethyl alcohol and mixtures of methyl alcohol and ethyl alcohol. The experiments reveal that the rate of sunflower oil transesterification with methyl alcohol was faster so the transesterification rate in the presence of ethyl alcohol.

The separation of glycerin from biodiesel merchandise was improved by adding a demulsify agent into the reaction system before transesterification procedure and 1:10 demulsify agent-sunflower oil grinder ratio was found to give the faster separation although the ethyl ester output is much lower than methyl ester output hence, extra surveies are indispensable in order to increase the ethyl ester output.

Recognitions

The writers are thankful for fiscal support to UEFISCSU PN II-PD-6/28.07.2010.

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