Hello aspirate 

 Out of 16 IITs only 10 IITs offer chemical engineering .Package in Chemical engineering depends on your capabilities. You may get average salary of 7.5 or 8 lakh package per annum depending on the companies and your skills. And you can also earn maximum package of 50 lakhs per annum in companies like  Reliance petroleum, Indian oil corporations etc . These companies offers high package in IIT Delhi. 

Hence it totally depend on your capacity and knowledge to get jobs in Best companies with best placement .

Hope it helps