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Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: ciel on March 29, 2006, 08:44:36 PM

Title: separation: Naphtalene, Ethylene glycol, Ethyl benzene, Styrene
Post by: ciel on March 29, 2006, 08:44:36 PM

                 Mol % in feed     Boiling   Melting   Soluble in   Soluble in Molecule                            point (C) Point (C)  water       benzene

Naphtalene        12                 218       80.2       yes          yes
Ethylene glycol    18                197       -11.5      yes          no
Ethyl benzene       32               136.2     -95       no            yes
Styrene               38              145.2       -30.6     no            yes

Separate this into four essentially pure product streams. Indicate the separation technology you choose and the sequence of the separation steps.

The answer that I came up with :

N, EG, EB, S  -EXTRACTION w/ water--> we get two streams which are :

the first stream : EB,S --DISTILLATION--> we get two streams, one contains EB and another contains S

the second stream : water + N + EG  -EVAPORATION-> we get two streams, #1 is water and #2 is N + EG

Do EXTRACTION with benzene to the second stream which contains N,EG. The results are two streams, #1 contains EG and #2 is benzene + N.
My questions are :

* Is my answer correct?
    The heuristic that I should follow are :
     - if the feed is already in two phases, use a mechanical separation technology. If it's in single phase, first consider equilibrium-based separation
      - for equilibrium-based separation, consider differences in boiling pt, melting pt, solubility in common solvents, and binding to solid surface
     -avoid adding foreign material as possible
      - remove corrosive/hazardous material early
      - separate out components present in the greatest quantity first
     - save difficult separations for last
     -operate at temperatures and pressures as close to ambient as possible. Prefer T above ambient to below.
* How to separate benzene and naphtalene ?  I don;t havae any idea how to answer this one.

That's all. Sorry if this post is very long. I really hope someone could help. Thanks.
Title: Re:separation
Post by: Abing on April 01, 2006, 12:46:21 AM
My questions are:
1.the T difference between EB and S is small, which makes distillation need much energy.
2.Make sure that there is no azeotropy of  water and EG

The B.P. of bezene is 80.1??you can separate bezene and naphthalene by distillation easily
Title: Re: separation
Post by: cap on April 13, 2006, 07:53:09 AM
you can't separate benzene and naphtalene by distillation - naphtalen can't be in liquid phase
Title: Re: separation
Post by: eugenedakin on April 23, 2006, 10:25:35 PM
Hi Ciel,

There are many ways to skin-a-cat, or in this case to separate a mixture.  Although the method I am proposing *should* work, it would be best to try it in the lab first....

I like your first idea of adding water ... this will cause the ethylene glycol to adhere with water, and since Ethyl benzene is soluble in alcohols, it should (?) separate with the EG. (You may get eg, h2o, EB, or you may just get eg and h2o).  The water-glycol mixture can be separated by either 1) distillation or 2) centrifuge.  The water-glycol-styrene mixture can be separated by distillation.

Abing is right about the close boiling points of Ethyl Benzene and Styrene for distillation ... it could be done, but at the expense of a large amount of energy.

Benzene has a BP of 80.1 C.  Cap, why can't Naphthalene be in the liquid phase (I'm just curious)...