Auto Approve a release

I am trying to auto approve a release which is generated automatically from a requisition using iProcurement. Once the requisition is approved, the release gets generated, however, it does not gets approved automatically. I have done the following setups:

1. Created an Approved Supplier List for the vendor on a Category level

2. Defined the Sourcing Rules

3. Defined Assign Sourcing Rule

4. Defined a BPA with all the lines

5. Setup as a catalogue in iProcurement

6. Given the approval authority to the Buyer

- I now go and select an item from the catalogue and create a requisition

- Approve the requisition

The release is generated as soon as the requisition is approved by my manager