Like I said, there is no way to NOT display the posts on the main blog page. That is where all posts go.
There is a workaround, but it's going to screw up your blog if you've already got posts in that category: just set all posts in that category to have posted five years ago. I'm not sure if they'll show up in your RSS feed or not, though. But new posts won't show on the main blog page. Trouble is, if you've got existing posts in teh category, the new posts will actually come up BELOW them and may not be visible at all on the first page of the Category.
It's also a bad idea, SEO-wise. I dont' know why, but there seems to be a fad for what you're asking for, but believe me, you WANT blog posts to come up on the main page, if only to expose your readers to all the things you're talking about. You can interest people in things they didn't know they were interested in.
Let me make this clear: for a variety of reasons, some technical SEO reasons and some merely social engineering reasons, if you succeed in doing what you want, your hits and your meaningful readership will both decrease.
If you don't like the workaround above and still want to do this, I believe it's possible if you move your blog off Wordpress.com, get independent hosting, install Wordpress.org software there, and implement the solutions they suggest at Wordpress.org.