The Catalog is the core of Lightroom. Without it Lightroom won't know anything about your pictures, where they are or what changes you have made. If you don't want the Catalog then you might as well uninstall Lightroom altogether. In any case, deleting the Catalog will save you very little space. I suggest you look elsewhere to make your space savings - restore points, recycle bin, temp files, data (including image files)you no longer want, purge the Lightroom cache and reduce the allocated size etc. etc.. Or simply buy a larger disk drive, or an external one and shift some stuff off the laptop and onto that.