It IS possible to perform redirections (using mod_alias or mod_rewrite) via .htaccess but it operates using the requested file information, not "keyword" content within web pages. Perhaps you're using the term "keyword" incorrectly? Above, it looks like you're talking about changing directories or extensionless filenames.
One of my "soapbox" speeches ("Specificity") is to start any mod_rewrite redirection by specifying EXACTLY what you want to change (which implies that is ONLY what you want to change) and what you want to change it to. Once you have your specification, it's a simple matter to write the mod_rewrite code to perform the redirection.
You might benefit from reading the mod_rewrite tutorial linked in my signature as it contains explanations and sample code. It's helped may members <snip/> and should help you, too.