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Palladium/Zeolite Adsorber for NOx and CO Exhaust

Battelle Number(s): 31423
Clearance Number: PNNL-SA-152317
Patent(s) Issued
Available for licensing in all fields

Zeolites: Exploring Molecular Channels
  • PNNL’s patented synthesis method for preparing materials to adsorb noxious emissions achieves never-before-seen levels of atomic dispersion and metal loading.

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SUMMARY

Most cars and trucks today—and into the foreseeable future—are powered by diesel or traditional gasoline internal combustion engines. Great strides have been made in improving fuel economy and reducing harmful emissions from these engines through catalytic converters based on selective catalytic reduction. But these technologies have a hard time removing noxious gases, such as carbon monoxide (CO) and nitrogen oxides (NOx), from vehicle exhaust during startup when engine temperatures are low. Solving the “cold start” conundrum of eliminating harmful emissions is viewed as a critical step in the next era of advanced, high performance engine development.

A new simple and scalable modified ion exchange approach invented by PNNL researchers may hold the key. In laboratory tests, the method achieved never-before seen loading and dispersion of metals in a small-pore zeolite (SSZ-13) adsorber and completely removed NOx and CO from the vehicle exhaust flow at relevant cold start-temperatures. The PNNL approach uses a synthesis method to prepare the adsorption materials, starting with the ammonium-form of the zeolite along with nitrate salt solutions of platinum (Pt) and palladium (Pd). Spectroscopic and performance tests under simulated industrial conditions revealed the different ion exchange behaviors of Pt and Pd zeolite adsorbers. Results confirmed full atomic dispersion of Pd in the SSZ-113 micropores at both 1 wt% and 2 wt%, and 90 percent dispersion at 3 wt%.  The record-breaking performance of Pd/SSZ-113 represents a new class of environmentally important passive NOx and CO adsorber (PNA) material with superior performance under industrially relevant conditions.

In previously reported ion exchanged zeolite frameworks, the agglomeration of the active metal limited their atomic dispersion to just 0.3 wt%. PNNL’s modified ion exchange approach uses only wet chemistry and does not require any complicated synthetic procedures.

Applicability

The new synthesis method developed at PNNL that produces atomically dispersed metal in Pd/SSZ-13 allows the preparation of a highly efficient NOx adsorber materials. These materials can be used in conjunction with the currently used selective catalytic reduction of NOx for emission abatement of diesel engine powered vehicles and fleets. 

ADVANTAGES

  • Achieves high loading (between 1-3 wt%) of atomically dispersed transition metals in the micropores of a small-pore zeolite
  • Removes CO and NOx with 100 percent efficiency at relevant cold-start temperatures
  • The approach is simple and scalable.

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