Diploma students can apply for direct B.tech second year. There are many colleges offer B.tech Lateral Entry programme through their own Entrance Exam.

Diploma holders can also apply for JEE Main Entrance Exam to be eligible for JEE Advance Entrance Exam as they are eligible to apply in IITs B.tech First Year.

You can also go for the short term job oriented Chemical Process Simulation Software like ChemCAD, Aspen-Plus, ASPEN-HYSYS etc. But I would suggest you to go for Graduation programme.

In case you have any other query then let me know.

Good Luck!