Enterprice level companies (and Publci companies with public purchases) have a centralized procurement process where purchase requisitons from different departments are consoildated to start a tender (RFQ) process in order to contract a vendor which will supply the goods within a period.

The end result - is purchase agreement. Actual deliveries are done partially within an agreement period.

As of now, when RFQ has been approved - purchase requisition automatically generates Purchase order.
The requirement is to generate Purchase agreement as a result of RFQ, which is possible to do manually, but not within Purchase requisition process.

It may require developments around budget funds allocation