Scott Humason

Ch241: MWF 8:30-9:50

Biosynthesis of Ethanol from Molasses

Summary:
The purpose of this experiment is to distill Ethanol (EtOH) fermented from a black strap molasses solution. From this fermented solution, I will then be comparing the results of a steam or simple distillation to a fractional distillation. The results will be in two stages. First, a density and percentage of Ethanol extracted from the Molasses solution. Second, a density and percentage of Ethanol extracted from the first stage of simple Ethanol distillation. The basic procedure is to take time and temperature of the first drop in temperature or of the consistent rise slow rise in temp. Continue taking the sample where about 1 drop per minute is expected and about 20mL of product is produced. In the fractional distillation, measure first boiling point (drip off thermometer), continue until temp is plus or minus 75 degrees and hopefully at or above 5mL of final product.

Discussion of Results:
Volume and % ethanol for each fraction

Simple Distillation:
18.5mL @ 17.3064g gives 47.40% Ethanol, or 94.8 proof.

Fractional Distillation:
5mL @ 4.1g gives about 92% Ethanol, or 184 proof.

% yield of Ethanol from reactive sugars in molasses
1.2g/mL X 70mL = 84g of Molasses @ 33% Sugar Density = 27.72g of Sucrose
C2H60 = 46.068


                                   (1 mol Sucrose)     (4 mol EtOH)  (46.068g EtOH)
27.72g Sucrose = ----------------------- ------------------ -------------------- = 14.88g EtOH
                               (342.296g Sucrose) (1mol Sucrose) (1mol EtOH)            (Theoretical Yield)


% yield of Ethanol from Molasses
Actual Yield 4.1g EtOH

--------------------- = % Yield ---------------- = 27.55% Actual Yield

Theoretical Yield 14.88g EtOH

Error and Quality Analysis of Experiment:
I feel that there is a lot of room for error in this experiment. First off, the stopping point has no clean finishing point. This means that more or less of the azeotrope could be in the final product, thus changing the density and ultimately the purity. The fractional distillation seems to be much more accurate as it relies less on human error because of the fractioning distillation columns and higher temperature to achieve the separation.

Evaluation of Experiment in Terms of Greenness:
This is a socially applicable experiment, especially for our ever pressing need for alternative fuel sources that are clean and renewable. Black strap molasses, a by product of Sugar Beets, is often a low grade feedstock for livestock. This obviously brings in many points of environmental stewardship, social responsibility, and costs to the whole picture into a larger production model. As an experiment, this is very green, as a large scale production model, there is a lot to consider outside of the science.