which gas is not obtained on a large scale by fractional distilation

argon

Not according to Google.
https://nzic.org.nz/app/uploads/2017/10/1K.pdf

argon

Argon

I apologize for the confusion. The correct answer is actually neon. Neon occurs in the air at a concentration of only 18.18 ppm (parts per million) and is typically obtained through cryogenic distillation.