Refining Alkenes: Separating Ethylene & Monomer Definition

[Vonderbach]

Hello all. I am not a student of science, in fact I'm relatively ignorant when it comes to most sciences in general. However, as a matter of personal interest, I have endeavored to understand a few things as they relate to my industry and some of the products that I sell.

At the moment, I am writing a technical article (from the layman's point of view) on heat shrinkable polyolefin tubing. I have interviewed a couple of people in the industry and been privy to the basics from the pellet stage forward. But where I lack clarity is in the processes prior to pelleting the polyolefin product for extrusion.

I have just two questions for the moment, but I'm sure they will lead to more if anyone is interested in discussing this with an ignorant plebeian. ;)

•By what process do you separate post-cracked ethylene from the accompanying propene and other trace compounds?

•Is a monomer an atom or a molecule? Sources such as wikipedia claim that a monomer "may be" an atom or a molecule. That seems very vague and contradictory. How can a monomer (meaning single part) be used to describe a molecule (multiple atoms?)

Thank you in advance for any input you might offer. If there is a substantial contribution, I would gladly credit you in my paper. It won't be anything glamorous, but I suspect it will be viewed by more than a few thousand people over the course of a few years.

 

[Bloodthunder]

By what process do you separate post-cracked ethylene from the accompanying propene and other trace compounds?

Fractional Distillation may be possible.

Is a monomer an atom or a molecule? Sources such as wikipedia claim that a monomer "may be" an atom or a molecule. That seems very vague and contradictory. How can a monomer (meaning single part) be used to describe a molecule (multiple atoms?)

Monomers can be both a single atom or a long chain of molecules. It is just a repeating unit in a long chain of a polymer.

For example, polyethene. We have

In this case, (Edit by Borek: too large image deleted, it was just the most right part of the above image) is the monomer.

 

[epenguin]

Perhaps for the OP who struggles with chemistry and terminology, we should say the thing on the very left is the monomer, and the thing on the very right in brackets is called the monomer residue - its different from the monomer of course because the monomer has reacted - in this case the double bonds have opened and attached to other carbons. (OK?)