What is the approximate upper limit for elements fused and expelled by stars that eventually form planetary nebulae?

Answer

Nothing much heavier than carbon

Stars of lower-to-intermediate mass, whose demise leads to planetary nebulae, do not achieve the temperatures required to fuse elements beyond carbon during their lifetime.

What is the approximate upper limit for elements fused and expelled by stars that eventually form planetary nebulae?
SpaceastronomycompositionnebulaElements