When you share a post on Facebook, or when Jetpack Publicize publishes a post to your Facebook page, Facebook crawls the page and looks for Open Graph meta tags in the head to build a complete post preview (with an image, title, description, ...).
You can see what Facebook sees by entering one of your posts' URLs in Facebook Debugger:
I would recommend putting the URL of a post that isn't publicizing properly into the Debugger tool to see if you have any errors. If there are any errors, Facebook will reject the post when it’s shared using the Facebook API.
It mentions an error in regards to the article:section tag. You have 2 on your site, so I can't be certain which one is the problem, but I'd bet it's this one:
<meta property="article:section" content="Ciência" />
See how the accent is written out using an HTML entity? I suspect Facebook may be having problems with that. Since your OG tags are output by Yoast's SEO plugin and not by Jetpack, you'll have to ask them for support for that: