I'm thinking no, why would they?
Say you had a container of various gases, each with a different density. Left undisturbed on the earth they would separate into layers (assuming they don't react with one another) depending on their densities right?
Now if you put this container deep into space free from (or as free as you can get) gravity from any source, would they still separate into layers depending on their density? I wouldn't be surprised if each gas formed it's own group or groups, but they wouldn't separate depending on their density as there is no gravity acting on the particles for that to make a difference I assume.
Yeah some flat earther is trying to convince me that gravity doesn't exist, it's just a bogus theory the government introduced to us in order to explain people walking "upside down". And apparently gasses don't need gravity to separate into layers.