Make a selection (manually select what you want or build a collection), Export as Catalog. Make new Catalog, Import as Catalog. Everything (Keywords, etc) get copied over. In theory you could do this with a single image to ‘clone’ the original catalog’s data to start fresh without additional images.
And no, I think unless you have hundred of thousands of images in a catalog, one big catalog makes far more sense! Separate the images using smart collections, with keywords etc.