Killkenny parish records are included on the pay-site
www.irish-roots.net - but I dont see any Patrick Molloy born in Kilkenny around that time - search for all Ireland between 1807 and 1815 lists the following Baptisms :
Mulloy Patrick 1808 Co. Meath
Mulloy Patrick 1808 Co. Galway
Molloy Patrick 1810 Co. Westmeath
Molloy Patrick 1811 Co. Westmeath
Mulloy Patrick 1811 Co. Meath
Mulloy Patrick 1813 Co. Meath
Mulloy Patrick 1814 Co. Meath
Molloy Patrick 1815 Co. Dublin
Molloy Patrick 1815 Co. Limerick
there are 24 Molloy records for other names for that timeframe in Kilkenny (City & County) - a few of which are spelt Mulloy. Many of the parish records commence after 1811 so Patricks birth could have been missed.
There is also a marriage of a Patrick Molloy in 1833 - so age 22 by the dates you have
Church Marriage Molloy Patrick 1833 Co. Kilkenny
The record is from the Catholic Parish of Callan - which is centred around the town of the same name - and about 16km south-west of Kilkenny City. It's not possible to tell the Bride's name without paying for the transcript - €5. The index searches on this site are free once you register.
Shane