De or het patentering?

The correct Dutch article is:

de patentering

Rule Words ending in -ing: almost always de. See the rule

How to use patentering

the patenteringde patentering
this patenteringdeze patentering
that patenteringdie patentering
our patenteringonze patentering
your patenteringjouw patentering
every patenteringelke patentering
which patentering?welke patentering?
a big patentering / the big patenteringeen grote patentering, de grote patentering