Continuous diesel soot control with minimal back pressure penatly using conventional flow substrates and active direct soot oxidation catalyst disposed thereon

Abstract

There is disclosed high cell density or tortuous / turbulent flow through monolithic catalyst devices for the direct catalytic, and (semi) continuous oxidation of diesel particulate matter. The catalysts relate to OIC / OS materials having a stable cubic crystal structure, and most especially to promoted OIC / OS wherein the promotion is achieved by the post-synthetic introduction of non-precious metals via a basic (alkaline) exchange process. The catalyst may additionally be promoted by the introduction of Precious Group Metals.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of provisional application 61 / 308,879, filed Mar. 27, 2008, and is a continuation-in-part of application Ser. No. 12 / 240,170 filed Sep. 29, 2008, and application Ser. Nos. 12 / 363,310 and 12 / 363,329, both filed Jan. 30, 2009, all of which are relied on and incorporated herein by reference.INTRODUCTION AND BACKGROUND[0002]Over the last thirty years increasingly stringent legislative limits have been introduced to regulate the emissions from both petrol (gasoline) and diesel internal combustion engines. See Regulation (EC) No 715 / 2007 of the European Parliament and of the Council, 20 Jun. 2007, Official Journal of the European Union L 171 / 1, see also Twigg, Applied Catalysis B, vol. 70 p 2-25 and R. M. Heck, R. J. Farrauto Applied Catalysis A vol. 221, (2001), p 443-457 and references therein. In the case of diesel / compression ignition engines this has led to the implementation of the Diesel Oxidation Catalyst (...

AI Technical Summary

Benefits of technology

The patent describes a method and apparatus for effectively converting particulate matter in diesel engines. The invention involves combining a base metal modified Oxygen Storage (OS) material with a conventional flow substrate, such as metallic or ceramic materials. The substrate has a high number of channels or cells per unit area, which provides a synergy that allows for high conversion of particulate matter without the need for high temperature regeneration cycles. The use of a flow substrate with a high cell density and turbulent flow provides optimal interaction and reaction between the entrained soot particles and the active catalytic coating. The method also allows for increased washcoat adhesion and higher concentrations of active materials, further enhancing performance and hydrothermal durability. The use of a flow through monolith optimizes the textural characteristics of the washcoat for activity and reduces back pressure penalty.

Problems solved by technology

Secondly, the high cell density restricts the flow path through the monolith, again increasing the potential for particulate collisions and retention / reaction on the active wash-coat, but without the large backpressure penalties associated with the conventional DPF.

However, the use of this ‘hyper-milling’ to obtain the very small particles for in-wall coating has been found to be extremely destructive to the activity, stability and surface areas of the OS and alumina components employed in typical formulations.

As a result such a process can adversely affect the rate of release and total Oxygen Storage capacity of the OS.

In addition the hyper-milling can result in cation extraction and phase disproportionation for the OS with further poisoning of any PGM function arising from the deposition of extracted cations.

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