There will certainly be a temperature drop, especially if the pipe is not insulated. If you need to maintain the 280F, you will have to insulate and add heat tracing. Of course I don't know the system and the chemistry may not allow this, but you could calculate the temperature drop and increase the 280F to whatever you need to have the right temp at the amine unit.
By the way, older homes are built with copper water piping, which is a pretty good conductor, so don't expect as dramatic a drop as from your hot water tank to your shower.