Polymerization can also take place at lower pressue. Increasing the pressure helps the gas to dissolve more in the slurry system of catalyst and  solvent. The more dissolved, the more the yield of polymerization.

of course there is an optimum pressure depending miscellaneous factors.

Dear all,

you are not specifying which generation of ZN catalysts you are talking about. I suppose you are dealing with the fourth generation also known as single site Zigler-Natta catalyst.

It is the opposite to what you have said. High pressure leads to more regular chains and favors high conversion, since it reduces the inter-reactants space or volume rendering them more close contacted. Regards