Certified GKH Gardening Expert
You can plant any shrub in a container as long as you provide it enough space for the roots and enough water. If you would like a patio lilac, I would recommend looking for dwarf varieties as these stay smaller and make it easier to provide they water and root space they need.
Also keep in mind that plants in containers experience conditions that are one zone lower than yours because they are not insulated in the ground. So, if you live in zone 5, you need a lilac that is tolerant to zone 4 if you plan on growing it in a container.