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Topic: Consecutive operations with reactions  (Read 4705 times)

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Offline daiskex16

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Consecutive operations with reactions
« on: October 03, 2010, 01:40:52 AM »
Hi guys! We have this problem from our problem set in Material Balance

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Ethylene chlorohydrin and glycol are produced from chlorine, water and sodium bicarbonate in the following process:

Chlorine and ethylene are absorbed in a water tower and react to yield the chlorohydrin:

C2H4 + Cl2 + H2:rarrow: ClC2H4OH + HCl

The exit-tower solution contains 5% by weight chlorohydrin, along with traces of ethylene dichloride as a by-product.
The dichloride is separated by decantation. This solution is now fed into a still and the chlorohydrin-water azeotrope, which contains 42% chlorohydrin and no HCl is taken as the overhead distillate product.
The still bottoms contain 1% chlorohydrin and all the HCl.
This distillate is then taken into an autoclave where the hydrolysis takes place at 150 degrees Celsius. A stoichiometric amount of bicarbonate is used:

ClC2H4OH + NaHCO3  :rarrow: NaCl + CO2 + HOC2H4OH

The Hydrochlorination reaction proceeds with a yield of 95% based on ethylene. The 5% by-product may be taken to be the dichloride. The hydrolysis yield is 90%; the other 10% of the chlorohydrin is converted to the ethylene oxide via

ClC2H4OH + NaHCO3  :rarrow: NaCl  H2O + CO2 + C2H4O

4 kg of ethylene glycol is to be produced in a bench-scale equipment. Make a complete material balance for the system.

--------------------------------------------

I am really confused in making the figure for this problem. my first attempt was:


C2H4 ---->                     ClC2H4OH; HCl                               42% ClC2H4OH
Cl2 ------>WATER TOWER ------------->DISTILLATION TOWER------------------->
H2O ----->          |                                      |
                          |                                     |
                          |                                     |
                       C2H4                       1% ClC2H4OH; all HCl


But my question is for the 42% chlorohydrin in the distillate and 1% in the bottom, where is the remaining 57%?

plus, I could not get this part of the problem:

The Hydrochlorination reaction proceeds with a yield of 95% based on ethylene. The 5% by-product may be taken to be the dichloride. The hydrolysis yield is 90%; the other 10% of the chlorohydrin is converted to the ethylene oxide via

ClC2H4OH + NaHCO3  :rarrow: NaCl  H2O + CO2 + C2H4O

Help please, thank you! :)

Offline skbuncks

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Re: Consecutive operations with reactions
« Reply #1 on: October 07, 2010, 10:24:10 AM »
Quote
But my question is for the 42% chlorohydrin in the distillate and 1% in the bottom, where is the remaining 57%?

Given that..

Quote
This solution is now fed into a still and the chlorohydrin-water azeotrope, which contains 42% chlorohydrin and no HCl is taken as the overhead distillate product.

...to what do you think the 42% refers to. Hint, it is not yield.

skb

Offline skbuncks

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Re: Consecutive operations with reactions
« Reply #2 on: October 07, 2010, 10:27:58 AM »
Quote
The Hydrochlorination reaction proceeds with a yield of 95% based on ethylene. The 5% by-product may be taken to be the dichloride. The hydrolysis yield is 90%; the other 10% of the chlorohydrin is converted to the ethylene oxide via

ClC2H4OH + NaHCO3  right arrow NaCl  H2O + CO2 + C2H4O

4 kg of ethylene glycol is to be produced in a bench-scale equipment. Make a complete material balance for the system.

First things first. You need to make 4 Kg of ethylene glycol. How much ethylene would be required given that the stage yields are 95% and 90% respectively?

skb

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