Monometallic rhodium-containing four-way conversion catalysts for gasoline engine emissions treatment systems

A catalyzed particulate filter located in an emission treatment system downstream of a gasoline direct injection engine for treatment of an exhaust stream comprising hydrocarbons, carbon monoxide, nitrogen oxides, and particulates and downstream of a three-way conversion (TWC) composite comprising a first TWC catalytic material on a flow-though substrate, the catalyzed particulate filter comprising:

• a particulate filter having a wall thickness in the range of about 6 mils (152 μm) to about 14 mils (356 μm) and a porosity in the range of 55 to 70%;
• and
• a second three-way conversion (TWC) catalytic material in an amount in the range of about 0.17 to about 5 g/in3 (10 to 300 g/L), the second TWC catalytic material comprising rhodium as the only platinum group metal
• wherein the catalyzed particulate filter has a coated porosity that is less than an uncoated porosity of the particulate filter and a coated backpressure that is substantially the same as an uncoated backpressure of the particulate filter.

A method of making emission treatment system for a gasoline direct injection engine, the method comprising:

• positioning a three-way conversion (TWC) composite comprising a first TWC catalytic material on a flow-through substrate downstream of the gasoline direct injection engine;
• and
• positioning the catalyzed particulate filter downstream of the TWC composite, wherein:
• the obtaining a catalyzed particulate filter comprises a second three-way conversion (TWC) catalytic material permeating walls of a particulate filter, the particulate filter having a wall thickness of about 6 mils (152 μm) to about 14 mils (356 μm) and a porosity of 55 to 70%;
• and
• the second TWC catalytic material comprises rhodium as the only platinum group metal.