I'm not sure we understand your question. You don't really "close" a catalog except for when you exit Lightroom. If you don't want to work on what you have opened then you simply go to another folder or import some new images. Lightroom doesn't have the normal save and close routine like you have in Photoshop or other photo editors. Adjustments are saved in the catalog as you make them. The catalog contains a history of the adjustments and is only really saved when a backup of the catalog is done.
