Akho, I have not use Aspen a lot, but all simulation programs are similar.
In essence you need to do a flash calculation, and the typical steps are:
- Select your components (H2+Benzene)
- Select the thermodynamic method (SRK or PR with interaction coef is probably okay).
- Add a stream or feed to the flowsheet.
- Add the composition and flow rate for the stream.
- Specify two of the following: Temp, Pres, Enthalpy, Entropy, Liquid fraction.
- Run the simulation and look how much H2 is in the liquid phase.