When conducting a transesterification , the reaction that forms biofuels (fatty

Question

When conducting a transesterification, the reaction that forms biofuels (fatty acid methyl esters) from vegetable oils, there is a competing reaction called a saponification. Saponification does not give the desired fatty acid methyl esters, instead the sodium salt of the fatty acids are obtained. These fatty acid sodium salts are commonly known as soap, hence the term saponification (soap making). Saponification is favored by the presence of water and/or absence of methanol in the reaction and high base (NaOH) concentrations.

Given this information and your chemical knowledge, select ALL the correct statements in the choices below. (To receive credit you must select all the correct statements and NOT select those that are false.)

A) The products of saponification, the sodium salts of the fatty acids, are of no consequence, since they are structurally the same thing as the fatty acid methyl esters (biofuel) and so they have the same properties.

B) The boiling point of methanol is 65 ?C; if the reaction is run at 80 ?C, saponification will be favored.

C) Adding glycerol to the transesterification (biofuels synthesis) will favor the formation of fatty acid methyl esters (biofuel).

D) Limiting the concentration of NaOH by preparing dilute methanolic NaOH solutions (NaOH dissolved in methanol) and using larger volumes of this dilute solution (so in effect, there is less NaOH and more methanol) should suppress saponification and favor transesterification (biofuel synthesis).

When conducting a transesterification, the reaction that forms biofuels (fatty acid methyl esters) from vegetable oils, there is a competing reaction called a saponification. Saponification does not give the desired fatty acid methyl esters, instead the sodium salt of the fatty acids are obtained. These fatty acid sodium salts are commonly known as soap, hence the term saponification (soap making). Saponification is favored by the presence of water and/or absence of methanol in the reaction and high base (NaOH) concentrations. Given this information and your chemical knowledge, select ALL the correct statements in the choices below. (To receive credit you must select all the correct statements and NOT select those that are false.) A) The products of saponification, the sodium salts of the fatty acids, are of no consequence, since they are structurally the same thing as the fatty acid methyl esters (biofuel) and so they have the same properties. B) The boiling point of methanol is 65 °C; if the reaction is run at 80 °C, saponification will be favored. C) Adding glycerol to the transesterification (biofuels synthesis) will favor the formation of fatty acid methyl esters (biofuel). D) Limiting the concentration of NaOH by preparing dilute methanolic NaOH solutions (NaOH dissolved in methanol) and using larger volumes of this dilute solution (so in effect, there is less NaOH and more methanol) should suppress saponification and favor transesterification (biofuel synthesis).

Explanation / Answer

The saponificaiton process is a second order reaction so rate of reaction will depend both on the concentration of triglycerol and NaOH.

so if we will decrease the conc of NaOH it will not favour the saponification process or will favour transesterification.

So statement C and D are correct.

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