Basic question: Can I connect 300# nozzle with a 150# line?

Hi experienced guys, I mean, everyone (everyone has more experience than me)

I have an exercise where a 300# vessel nozzle has to be connected to a 150# pipeline.
Can I do this in real world?
I mean, my pipeline has all components (valves and flanges, etc) with rating 150# but when it reachs the vessel I need a 300# flange to connect to this nozzle. Is that right?

Thank you.