There is not an exact pressure ratio that radial inflow turbines are limited to. Roughly speaking, I would say that 10:1 is near the maximum to maintain good efficiency, but there are also total enthalpy drop limitations that you may run into depending on the working fluid (as well as other limits).
I imagine that you are looking at Cyclohexane for an ORC working fluid due to it's high cycle efficiency. As far as I know, no one has built a cycle using this fluid and the fluid itself is very volatile and is not available in large quantities.