A very technical question. All depends on the design of the reactor, process conditions and operating parameters.
What is the aim? You want to displace material from one place to another place or you want to separate an ingredient? Based on these issues we have to design the system.
When you want to displace liquid from one place to another place you have to design the vacuum levels and temperature of working in such a way that no liquid will get evaporate during the process. if it happens your working will never be effective.
The boiling temperature of a liquid will come down when you apply vacuum. The boiling temperature of the same liquid will vary based on vacuum levels and temperature. Even we can suck high viscosity material using a vacuum and transfer from one place to another place.
ISRO will use vacuum casting technique for making rockets in which is a very high viscous composite propellant It is a mixture of solids and liquids and the functioning of the material depends very much on the composition. So the casting will be designed by vacuum in which all the parameters including flow rate of the material is also designed in such a way that the temperature will not go beyond a particular level, the material will flow from the vessel to the casing of the rocket within the specified time. This should happen so accurately that even there should not be any air entrapment also.
All depends on your material properties, the constituents, the level of vacuum, the temperature of the system, the positioning of the reactors, the design of the reactor etc.
So if you want to know the exact conditions you have to use, you have to give me more details. However, I think generally, how it is work is explained above.