PSU you can go for after MSc through GATE:

Mineral Exploration Corporation Ltd. ( Executive trainee chemist)

Oil and Natural Gas Corporation (chemist)

IOCL ( asst officer quality control )

DRDO ( scientists grade b )

BARC( scientists grade b)

You check the official website of the afore mentioned to know more about them.

I hope my answer helps. All the very best for your future endeavors!