Yes! You can export from Lightroom to an FTP server. The bigger question is, what is it that you really want to do? If you are simply looking to make images available to clients, there is an easier way to do so through the web galleries that Lightroom creates automatically through the Adobe creative cloud subscription service for photographers for $10 a month. And yes you can limit access.
If you're still interested in learning how to upload images to an FTP server from Lightroom for free, please contact me and I can show you how.
Thanks,
Reid