Distillation-lab (1).pdf - Chem 226 SIMPLE AND FRACTIONAL DISTILLATION OF ESTERS THE EXPERIMENT Scenario A project that will make use of your new gas

Distillation-lab (1).pdf - Chem 226 SIMPLE AND FRACTIONAL...

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Chem 226 SIMPLE AND FRACTIONAL DISTILLATION OF ESTERS THE EXPERIMENT: Scenario: A project that will make use of your new gas chromatography skills has just come in to the CRW institute. A new recycling company intends to fractionally distill and sell the components of a manufacturer’s waste mixture. The literature indicates that since the boiling points of the two major components are 7˚ C apart, about 30 “theoretical plates” will be needed in the fractionating column. The company would like a good estimate of the HETP value for the type of fractionating column they have provided and the height of column therefore needed for the planned separation. They would also like an advisor to come and explain the distillation technique to their technicians who work the Saturday shift. Since you are the new person in your group and nobody else wants to work on Saturday, you are chosen for the project and training mission. To prepare for the training session you will need some practical and theoretical experience with various distillation techniques. You will also need to prepare distillation curves to graphically show how well each works. For this part you will work with a colleague, one person doing simple distillation and one doing fractional distillation. Applying Scientific Methodology A) A common measure of the efficiency of the fractionating column used in fractional distillation is given by its number of “theoretical plates”. One theoretical plate’s worth of separation of a mixture is the difference in percent composition of the components that would be expected by one vaporization- condensation cycle. While theoretical plates could be actual plates in the column, in the usual column the distillation does not occur in discrete steps but is continuous up the column. A H eight of column material that provides the separation E quivalent to the separation expected for one T heoretical P late (ie the HETP ) is measured. To determine HETP for fractionating column materials you need to know the composition of the vapor at the top of the column and the composition of the liquid mixture boiling in the pot at the bottom of the column. We will do this by boiling a known composition mixture of ethyl acetate and n-butyl acetate and collecting the condensed vapor at the top of the column as the first distillate in a distillation. The percent composition of this “HETP sample” of distillate will then be determined by GC analysis. This will tell us the total number of theoretical plates from the boiling pot (counted as one plate) and the height of column used. Dividing the column height by the number of theoretical plates in the column gives HETP.
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