Develop a block diagram showing all of the constituent process reactions (one reaction or process per block) required to produce common PET polyester
(polyethyleneterephthalate) via the DMT Route starting from fundamental raw materials such as natural gas methane (CH4), natural gas condensate ethane
(C2H6), crude oil naphtha (assume normal octane, C8H18)), air (N2 and O2), and water (H2O). Write balanced chemical equations for every reaction.
Considering the overall supply chain and its component balances, comment on recycle possibilities among these constituent processes within the supply
chain.
Intermediates you should consider include:
Ethylene, C2H4
Ethylene Oxide (EO), C2H4O (3-member ring)
Ethylene Glycol (EG), HOC2H4OH
Xylene (mixed), C6H4(CH3)2 (three isomers)
Paraxylene (1,4-dimethylbenzene, pX), CH3C6H4CH3
Terephthalic Acid (1,4-benzenedicarboxylic acid, TPA), HOOCC6H4COOH
Carbon Dioxide, CO2
Carbon Monoxide, CO
Hydrogen, H2
Methanol (MeOH), CH3OH
Dimethylterephthalate (DMT), CH3OOCC6H4COOCH3
Bis(2-hydroxyethyl)terephthalate (PET “monomer”, BHET), HOC2H4OOCC6H4COOC2H4OH
Polyethyleneterephthalate (PET), (‒C2H4OOCC6H4COO‒)n
Some chemistries:
Ethylene is made by steam cracking of ethane (the steam keeps the system from coking)
Ethylene oxide is made by the air oxidation of ethylene
Ethylene glycol is made by ethylene oxide hydration
Xylene is made by the catalytic reforming of octane
Terephthalic acid is made by the air oxidation of paraxylene isomer
Carbon dioxide is made by the combustion of methane
Syngas (hydrogen carbon monoxide mixture) is made by the steam reforming of methane
Excess hydrogen in syngas can be reacted with carbon dioxide to produce carbon monoxide (water gas shift reaction)
Methanol is made from an exactly 2:1 (hydrogen : carbon monoxide) ratio syngas
Dimethylterephthalate is made by the esterification of terephthalic acid with methanol
Bis(2-hydroxyethyl)terephthalate is made by the transesterification of DMT with EG
Polyethyleneterephthalate is made by the polycondensation of BHET splitting out EG
An appropriate basis for the overall supply chain component balances might be the final polymer repeat unit -C2H4OOC6H4COO-.
