polyethylene (1 Viewer)

[Jimmay]

Hi, im just having some trouble with these dp's:

identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum.

we were taught thermal cracking, which is basically just using steam to crack the long chain hydrocarbons. Is this sufficient or should i learn about the cat cracking with zeolites?

outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

Our class was taught the method involving:

The initiator - a peroxide
Propagation - the dbl bonds repeatedly break to link up
termination - the chains are end with a H or looped
& separation - the chains are separated from the vessel.

Is this too brief?? Because in conc chem, it goes on about the zeigler natta process and the gas phase process, both of which go in depth ie- pressure and temp.

Thanks

 

[Chand]

umm..we've covered both catalytic n thermal cracking and I remember getting a couple of q on it. You should learn catalytic to be on the safe side.

 

[Dangar]

I'd go in a bit more depth for polyethylene. You need to know the two different processes cos each one produces a different type of polyethylene with different properties and uses.

Gas phase process produces low density polyethylene (LDPE) this is the one you already know

Ziegler-natta process produces high density polyethylen (HDPE).

It's probably not essential but it gives you that much extra to make you seem intelligent!

 

[Jimmay]

alright then, thanks for your help guys

 

[sneaker]

The answer to the first one is Crude Oil. They took out the dot point that said explain how polyethylene is made from the fractions of Crude Oil (which is where you would have to go on and talk about steam and catalytic cracking)

and the second one, you know the basic process so depending on the glossary term, i.e. describe or explain you should be right, so long as you suit it.
good luck

 

[hellohello]

Originally posted by Jimmay
Hi, im just having some trouble with these dp's:

identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum.

we were taught thermal cracking, which is basically just using steam to crack the long chain hydrocarbons. Is this sufficient or should i learn about the cat cracking with zeolites?

outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

Our class was taught the method involving:

The initiator - a peroxide
Propagation - the dbl bonds repeatedly break to link up
termination - the chains are end with a H or looped
& separation - the chains are separated from the vessel.

Is this too brief?? Because in conc chem, it goes on about the zeigler natta process and the gas phase process, both of which go in depth ie- pressure and temp.

Thanks

can u explain the last one a bit more

 

[Constip8edSkunk]

a peroxide breaks up 2 form reactive radicals that reacts with ethylene by breaking up its double bond, and forming a monomer radical which can break more double bonds as more ethene are added on. the process can be terminated by reacting two chain radicals 2gether or by reacting with another free radical. this polymer can then be extracted.

 

[hellohello]

thnxs a million baby

 

[iambored]

Originally posted by Jimmay
identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum.
outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

1. both

2. i also have a brief thing. every book i look at has a different way though

 

[ice_cube]

outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

Our class was taught the method involving:

The initiator - a peroxide
Propagation - the dbl bonds repeatedly break to link up
termination - the chains are end with a H or looped
& separation - the chains are separated from the vessel.

humm~~
is this jux 4 the production of LDPE?

 

[Dreamerish*~]

humm~~
is this jux 4 the production of LDPE?

Yes. HDPE requires the Ziegler-Natta process. In exams, you are usually not required to talk about Ziegler-Natta, but you must remember the three steps of the production of LDPE.

Gosh, that was an old, old thread.

 

[Riviet]

In Conquering Chemistry, it explains the gas phase process as well as mentioning LDPE, but it doesn't directly mention HDPE while explaining the Ziegler-Natta process.