In an anaerobic fermentation of grain, the saccharomyces cerevisae digest glucos

Question

In an anaerobic fermentation of grain, the saccharomyces cerevisae digest glucose (C_2H_12O_6) form plants to from ethanol (C_2H_5OH)and peopernic acid (C_2H_5CO_2H) by the following reactions: Reaction 1: C_6H_12O_6........ rightarrow 2C_2H_5OH + 2CO_2 Reaction 2: C_6H_12O_6........ rightarrow 2C_2H_5CO_2H + 2H_2O In a batch process, a tank is charged with 4000 kg of a 12%, solution of glucose in water. At the end of fermentation process 120 kg of CO_2 are produced and 90 kg of unreacted glucose remains in the broth. What are the mass percents of ethanol and propenoic acid in the broth at the end of fermentation? Assume, no glucose is assimilated by the bacteria. To make cyclohexane (C_6H_12), benzene is reacted with hydrogen, according to the following reaction C_6H_6 + 3H_2........ rightarrow C_6H_12 For the process of Fig 1. determine the ratio of the recycle stream to the fresh feed stream if the overall conversion of benzene is 95%, and the single pass conversion is

Explanation / Answer

(2)

Mass of glucose solution = 4000 kg

% by mass glucose = 12 % = 12*4000 / 100 = 480 kg

Initial water mass = 4000 - 480 = 3520 kg

Unreacted glucose = 90 kg

So glucose consumed = 480 - 90 = 390 kg

According to reaction 1,

1 mole glucose (= 180 g) produces 2 moles CO2 (= 44 g * 2 = 88 g)

Since 120 kg CO2 is produced, so mass of glucose consumed by reaction 1= 245.45 kg

Mass of ethanol produced by reaction 1 = 125.45 kg

So mass of glucose consumed by reaction 2 = 390 - 245.45 = 144.55 kg

Similarly, mass of propenoic acid produced = 59.4 kg

Mass of water produced = 28.9 kg

Thus, total mass in reactor broth after reaction = mass of glucose + total water + acid + ethanol = 90 + (3520+28.9) + 59.4 + 125.45 = 3823.75 kg

So mass% of ethanol = 125.45 / 3823.75 = 3.28 %

mass% of acid = 59.4 / 3823.75 = 1.55 %

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