You should be able to achieve this by using Sync selected playlists, artists albums and genres.
Currently, you are either using Sync entire library, which will add all playlists to your iPod, or you are using Sync selected playlists, artists, albums and genres but you have included your Purchased playlist as well.
With the iPod connected to your iTunes, click on the device icon at the top of your iTunes window:

- this displays the Device/Settings/Summary pane
- switch to the Device/Settings/Music panel (1.):

- the Sync Music option (2.) should already be selected
- look at the two options shown above in (3.)
- if the Entire music library option (3.) is selected, all the playlists will be added to your iPod. The various sections numbered (4.) will not be shown
- if the Selected playlists, artists, albums and genres option (3.) is selected, the list of Playlists will be displayed in Playlists (4.). In that panel, deselect the Purchased list and then tap the Sync (or Apply) button in the lower right corner of the iTunes window (not shown in the screenshot)