Petro chemical engineering is a branch of Chemical Engineering which deals with the operations of refining and petrochemical technology. You will first require degree in petroleum engineering/chemical engineering and you can further do PG in it for mastering in your specialization. 

You can apply for GATE entrance and apply for PSU which will help you placed in government agencies in your specialisation.

There are many government job prospects in this field like in drilling & oil refining companies like ONGC, GAIL, Indian Oil and etc. 

There is a huge demand for perto chemical/ petroleum engineers. With good experience you can expect decent pay packages.

Good Luck.