Project Requests do not appear in a timeline gantt.
Projects themselves will and in PPM6 it will be in the Executive tab. Select the view you want from the "More Views" list - or create one which meets your parameters and then switch format to Timeline Gantt. I suggest placing projects under a portfolio then creating a view that groups by parent project. This will give you what you are looking for.
also, the Timeline Gantt is based off of the Planned Start and Planned finish date in the Project Profile if there are no tasks in the project. If there are Tasks then the Timeline Gantt is based off of the earliest Task start, last Task finish.
A feature enhancement will be to show the Project Requests in the Executive tab Timeline Gantt - I will submit this to our product team!
Steve Thompson | Solutions Consultant
Daptiv