Protecting catalyst from phosphorus poisoning

A method of protecting the catalyst materials in a catalytic converter vehicle emissions control system from the poisoning effect of phosphorus, said converter being located in the exhaust path of an internal combustion engine, comprising contacting at least one engine gas stream selected from the crankcase ventilation stream and the exhaust gas recirculation stream with a bed of solid adsorbent capable of removing phosphorus and phosphorus compounds in said gas stream, and circulating said treated gas stream to the intake side of the engine, the phosphorus content of said exhaust stream being reduced by absorption from that present in the absence of said solid adsorbent treatment said bed being heated principally only by the stream being treated.