How to recycle catalytic converters?

I would like any information on how to recycle old catalytic converters. I would also like to know if anyone knows where to buy the machine to refine the scrap. Do all converters have precious metal in them? which ones have more which ones have less? is there a place that anyone know where i can get this information. I would like to start buying them and refining them myself but im not sure where to start. If anyone has any information it would be greatly appreciated. Thanks