PNNL

Abstract

The objective of this project is to develop a strategy for the integration of catalytic NOX emission control and particulate matter emission control into a single device for the successful application to heavy-duty on-road diesel engine exhaust aftertreatment. The critical attributes of such a device, for successful application to PACCAR fleet, are as follows: 1. Must have sufficient filtration efficiency and successfully demonstrate soot management strategies (i.e., oxidation) to be economically attractive and regulatory compliant for particulate matter abatement. 2. In particular, the integrated device must retain sufficiently high soot oxidation capacity with NO2 (i.e., passive soot oxidation) across an applicable engine test cycle to be economically attractive. 3. Must exhibit sufficient catalytic NOX reduction activity in an economically-attractive fashion that is regulatory compliant. Wall-flow diesel particulate filter (DPF) technology has been successfully developed and deployed for particulate matter (PM) removal from engine exhaust.1-3 Thus, DPF technology will be the basis of PM filtration for this effort, and PM removal efficiency will not be a fundamental focus of study is this project. Selective catalytic reduction (SCR) technology employing base metal-exchanged zeolite has also been successfully developed and deployed for the abatement of oxides of nitrogen (i.e., NOX) from diesel engine exhaust.4-8 Thus, SCR technology with base metal-exchanged zeolites will be the basis of NOX abatement for this effort. This project will develop a strategy for the integration of SCR and DPF technologies into a single device (herein referred to as SCRF) for the successful application to heavy-duty on-road diesel engine exhaust aftertreatment. The key technical accomplishments to be pursued in this work are as follows: 1. Integration of a DPF with a binary catalyst system consisting of an SCR phase and a selective catalytic oxidation (SCO) phase to enable sufficient passive soot oxidation capacity within the device. 2. The SCR-SCO binary catalyst system will be successful in enabling the availability of NO2 for achieving the necessary passive soot oxidation capacity within the integrated device while retaining high NOX reduction efficiency and minimizing the parasitic oxidation of NH3 (with O2). 3. Fundamental understanding of the interaction of the SCR and SCO catalyst phases will be achieved to lead to an optimized binary catalyst system, identifying the necessary engineering requirements and system limitations for their integration, with a view to proper function and optimal integration. 4. Develop the necessary understanding of aging and poisoning behavior of the binary catalyst system as it compares to current state-of-the-art SCR catalysts for determining the impacts of the SCO phase and mitigating of those that adversely impact aging behavior of the system. 5. Develop models that incorporate the SCRF catalyst system that can accelerate the optimization of the system by providing SCRF operational insight while simultaneously minimizing experimental testing. 6. Develop the necessary understanding to potentially lead to the design and optimization of 4-way devices, which will address PM, hydrocarbons, CO, and NOX in a single unit.