Evaporation of mixture in Fluent
 

Hi everyone,
I am trying to simulate a tray of a C3/C4 splitter and I am trying to decide how I will define the inlet materials.
Basically i have 2 inlets which are C3/C4 mixtures (a liquid inlet and a gaseous inlet) with different temperature and composition (so different density,CP etc) and i was wondering if I need to set the mixtures as new materials (i will find the properties from NIST) or do I have to set 2 mixtures that will be based on the materials from Fluent Database?
I am afraid Fluent wont be able to understand that from the liquid mixture that will be 70% C3 and 30% C4 the quantity that will be evaporated will be mostly C3 and respectively from the gaseous mixture that will be 40% C3 and 60% C4 the quantity that will be condensated will be mostly C4.
The temperature is 40oC and the pressure is close to 14.5 atm so i dont know how this will affect the new materials or the mixtures.
I am new to Fluent and I am confused regarding the setting of the materials/mixtures.
Thank you in advance!!