Toolstar and postcron both do what you are looking for.

https://postcron.com/en/ or http://www.toolsstar.com



if you have a wordpress website, there are a variet of free methods for doing this since you can update your site an unlimited number of times based on a cron job and then have it push to facebook or any other social media account

Try bufferapp.com it is one of the best

I can list half a dozen reasons why posting every 10-20 minutes is a bad idea, but that's not what your question is :)



If you want to be able to track statistics, I suggest you use Buffer ( https://buffer.com/r/343ca2 ) because they're a fantastic company and their software is quite impressive. I'm also slightly biased because it's who I use. You only get 10 slots in the free version (that's pretty normal across the industry) so if you want this to be free and high quality, you'll likely have to sign up for the free accts for both big players:



Buffer ( https://buffer.com/r/343ca2 )

Hootsuite ( hootsuite.com )



There's at least one more FB posting service out there, but it's not free after 30-days:

Sprout Social ( sproutsocial.com )



Here's a full breakdown for ya!

http://www.werockyourweb.com/sprout-social-vs-buffer-vs-hootsuite-vs-tweetdeck-vs-sendible/