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Analysis in Crude Glycerin

 

Parameters are analyzed on Crude Glycerin

 

Crude glycerin is side product of transesterification triglycerides with alcohol. Crude glycerin is purified in order to generate glycerol. The illustration of crude glycerin and refined glycerin is showed below. Before purifying crude glycerin, it should be analyzed with many parameter such as moisture, glycerol content, alcohol content, ash, mong, salt, and pH.

Moisture can be determined with Karl Fischer Method. According to Jeffery et al 1989, Karl Fisher method utilizes sulfur dioxide and iodine blended with anhydrous pyridine and methanol as reagent. Both this reagent will react with water to give C5H5NH(OSO2OCH3). The reaction is illustrated below. The principle of parameter is voltammetry titration. It can be proven since platinium cathode immersed in mixture is flown during iodine is on the mixture.

 Glycerol content is carried out by iodo-iodometry titration due to existing sodium metaperiodate. The sample dissolved with water is added with base solution until its pH value 8. The mixture is added with sodium metaperiodate due to oxidizing glycols in base condition. Hence formic acid and ion iodate are generated. The mixture is added with ethylene glycol and sodium formate. The reaction is described below (Santos et al, 2022).

Alcohol content is meaned with methanol content. Methanol content is analyzed through standard addition and chromatography. Crude glycerin is steamed to eliminate methanol inside then made glycerol solution 1% methanol (mass/mass, volume/volume). It is diluted into 4 concentration (0,01%-0,02%-0,03%-0,04%) then injected into gas chromatography. Each solution posses different peak area. Peak area is scattered with concentration. The equation results from scattered will be applied to all crude glycerin.

Salt content is analyzed though argentometry titration. Sample is titrated with standardized silver nitrate. Silver nitrate will make white precipitate with ion chloride. The bigger salt content inside crude glycerin the fastest sediment will be generated during titration.    

Parameter ash content is conducted through steamed sample in furnace at temperature 750 ºC for 10 minutes. Sample is firstly steamed in hot plate to reducing water then steaming in furnace. The rest sample from steaming in furnace is metal oxide. Mong is abbreviation from material organic non glycerol. Mong is only parameter which use mathematic calculation. Mong is generated due to partially transesterification on biodiesel production (Attarbachi et al, 2022). The formula of mong

Mong = 100% - moisture content – glycerol content – ash content

Crude glycerin is qualified good due to high glycerol content, low moisture, mong, ash, salt, and value of pH. The lower value of pH, the separation of crude glycerin and fatty matter is conducted properly.  

 

References

Attarbachi, T, Kingsley, M, Spallina, V, 2022, New Trend on Crude Glycerol Purification : a Review, Fuel, 340 (1-19)

Jeffery, G.H., Bassett, J., Mendham, J., Denney, R.C., 1989, Vogel's Textbook of Quantitative Chemical Analysis, 5th Edition, Essex : Longman Scientific and Technical

Santos, L, Rocha, S, Barra, C, Tubino, M, and Junior, J, 2022, A Simple, Rapid, and Reliable Titrimetric Method for the Determination of Glycerol at Low Concentration, J. Braz. Chem. Soc., Vol. 33, No. 6, 530-540

 

 

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