Petroleum Refinery Engineering
Crude oil is subjected to vacuum distillation in the last stage, because

Lighter/low boiling products are prone to thermal decomposition
High boiling point products like heavy fuel oil & lubricating oils are heat sensitive and may decompose
High purity products can be obtained thereby
None of these

ANSWER DOWNLOAD EXAMIANS APP

Petroleum Refinery Engineering
Mercaptans are

All of these
Low boiling sulphur compounds
Undesirable in petrol, as they reduce its octane number
Added in LPG cylinders to detect gas leakage by its smell

ANSWER DOWNLOAD EXAMIANS APP