Ethylene Guard Bed for Polyethylene Batch Reactor

[sshep]

Gentlemen,

We have a small scale polyethylene batch reactor used to test the performance of a comonomer (1-Octene). We use ethylene straight off our ethylene recovery plant, but are not really in the polyethylene business (at this site at least).

At a meeting this morning I was told that the customer was wondering why we did not guard bed our ethylene before the reactor to insure that our comonomer was run under the best possible conditions. It was proposed that ethylene feed guard beds were standard even in polyethylene plants that recieve polymer grade pipeline ethylene such as ours.

Is there anyone with polyethylene experience that can tell me if this information (feed ethylene guard bedding) is true? I would also appreciate some details as to what guard bed material is used, and what poisons are being targeted (acetylene, CO, methanol, etc).

best wishes always,
ssehp

 

[dcasto]

I'll get you started, I'm not a polymer engineer, but I delivered billion of pounds of ethylene and here are the problems we were asked to look into.

Sulphurs of course, poison catalysts.
CO2 is a polymer stopper, CO2 should be under 2 ppm.
Ammonia, it is found in refinery ethylene.
Water
Acetylenes.
Ethane and methane are inerts and just build up over time.

The gaurd beds are typically a ZnO to remove Sulphur, Mole sieves to remove water and CO2.

I don't remember what was the agent for ammonia.

The Catalyst handbook by Twigg has some good info.

 

[sshep]

DCasto,
Thanks for the advice. I have just ordered a copy of Twigg's "The Catalyst handbook". I may owe you a star.
best wishes,
sshep