question3.docx

Question3

(i) Thermal cracking ( heating heavy fractions under pressure) is one way to generate lower molecular weight fractions. What is one major disadvantage of thermal cracking ? Name two processes that have largely superseded thermal cracking .

One disadvantage it produce large amounts of coke. Two process that superseded are Visbreaking, Catalytic Cracking and Steam cracking .

(ii) What are the desired products from the process called steam cracking? Small Olefins ( ethylene , propylene , butadiene) and aromatics .

(ii) Each of the following reactions could be considered as typical of a particular stage petroleum processing. For each reaction stat the stage where the reaction is most likely to occur.

(1) Hyrdotreating (2)

Question 4

(i) Using proplyene as monomer shows :

(a) Syndiotactic

(b)

Isotactic

(ii) Briefly describe the Ziegler- Natta process, as applied to the polymerisation of propylene. What is significant about Ziegler- Natta polypropylene, compared with polypropylene made using free radical initiation?

1st ligand exchange between 2 metals ( give active Ti catalyst) 2nd Successive insertion of the first propylene into Ti-C bond3rd Add another onto another which gives a isotactic polymer with 92-99% stereochemical purity.

Compare to using free radical initiation can only give branched polyethylene and cant make polypropylene while with Zeigler-Natta you can make unbranched polyethylene and isotactic polypropylene.

Question 5Provide industrially useful methods for the production of TWO of the following:(i) Acetic Acid ( the Kativa or Monsanto process) Monsanto used rhodium catalyst with iodide methanol carbonylation - operate possible at 1 atm (3-6 atm) modest

Kativa - iridium catalyst with iodide

(ii) Adipic AcidTwo stage process : Produce Cyclohexanone / Cyclohexanol and then KA oxiation with nitric acid using Copper(II) catalysts.

(iii) Phthalic acid Catalytic vapour phase air oxidation of napthalene or ortho-xylene Napthalene is disfavoured due to availability and cost ( lose 2 Cs in process)

(iv) Terephthalic Air oxidation (liquid phase) of para-xylene

(v) Caprolactam Synthesis based on cyclohexane oximeRequires hydroxlyamine NH2OHThe oxime is converted to caprolactam by a Beckmann rearrangement

(vi) Phenol N20 byproduct is used to oxidise benzene to phenal Zeolite catalyst 3atm; 300-500

(vii) Tetrafluoroethylene

Question 6

(i) Provide a reaction for the conversion of para-xylene to terephthalic acid

(ii) An older method relied on nitric acid oxidation of para-xylene explain why this method is no longer favoured.It is no longer favoured as the new process produce >95% of yield and does not produce NH3.

(iii) Provide an explanation for where para-xylene is sourced. In your answer provide a description of how other aromatic compounds can be utilised and how paraxylene is purified.

Comes from reforming of low octances parrifins by doing that it gives (toulene, ortho-xylene, para-xylene) distillating it will give you what you want