Atomically Dispersed PGM Catalysts for Exhaust Gas Treatment
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Solution Overview
Problem
Platinum Group Metal (PGM) catalysts in exhaust gas treatment systems for vehicles experience particle growth and sintering at high temperatures, leading to reduced dispersion and activity, resulting in poor catalyst performance over time.
Innovation Solution
The formation of atomically dispersed PGM complexes on a non-modified metal oxide support, stabilized with alkali or alkaline earth metal atoms, oxygen, and hydrogen, which prevents particle growth and maintains active catalytic sites, thereby slowing down the aging process of the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PGM catalysts are used in exhaust gas treatment, then initial catalytic activity is achieved, but particle growth and sintering occur at high temperatures leading to reduced dispersion and activity over time
Solution Approach 1:
The PGM is segmented into individual atoms or very small clusters (2-10 atoms) rather than forming large particles. This atomic-level segmentation is achieved through co-impregnation with alkali/alkaline earth metals followed by controlled calcination, which prevents atom aggregation. The segmented structure maintains high dispersion and prevents sintering, resolving the contradiction between initial activity and long-term stability.
Solution Approach 2:
Alkali metals (K, Na, Li) and alkaline earth metals (Ca, Ba) serve as intermediary substances that stabilize PGM atoms during high-temperature operation. These intermediary metals form stable complexes with PGM atoms, preventing direct PGM-PMG aggregation that would lead to particle growth. The intermediary metals act as spacers and stabilizers, maintaining atomic dispersion over time.
2Reliability
If PGM loading is increased to maintain activity after aging, then catalytic performance is preserved, but cost increases and PGM utilization efficiency decreases
Solution Approach 1:
The invention changes the fundamental parameter of PGM structural state from particulate to atomic/dispersed. This parameter change enables maintaining catalytic activity with significantly reduced PGM loading (as low as 0.1-1.0 wt%) compared to conventional catalysts. The atomic dispersion state provides maximum surface area and active sites per unit mass of PGM, eliminating the need for increased loading to compensate for aging.
Solution Approach 2:
The catalyst forms a composite structure combining PGM atoms with alkali/alkaline earth metals and metal oxide support. This composite approach creates synergistic effects where the alkali/alkaline earth metals enhance PGM stability and dispersibility, while the metal oxide support provides additional catalytic activity. The composite structure achieves superior performance with lower PGM content.
3Duration of action of moving object
If the catalyst operates at high temperatures for extended periods, then exhaust gas treatment function is performed, but operational temperature drift occurs and accelerates aging
Solution Approach 1:
The catalyst undergoes preliminary stabilization during the co-impregnation and calcination process, where alkali/alkaline earth metals are pre-positioned around PGM atoms to form stable complexes. This preliminary action creates a thermally stable structure before actual catalytic operation begins, preventing temperature-driven structural changes and drift during extended operation.
Solution Approach 2:
The alkali/alkaline earth metals provide preliminary anti-action against thermal sintering and particle growth mechanisms. By forming stable complexes with PGM atoms during preparation, these metals preemptively counteract the tendency of PGM atoms to aggregate under high-temperature conditions, preventing temperature drift and maintaining structural integrity throughout operational duration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances PGM utilization efficiency, maintains active catalyst sites, and prevents operational temperature drift, resulting in improved CO and HC oxidation and NOx abatement performance even after aging.
Implementation Method 1
An alkali metal or an alkaline earth metal is bonded to the PGM species. The alkali or alkaline earth metal is part of a structure including oxygen atoms and hydrogen atoms.
Implementation Method 2
The treatment system for the diesel engine includes a diesel oxidation catalyst (DOC), which is capable of oxidizing carbon monoxide (CO) and hydrocarbons (HC). The treatment system for the stoichiometric spark-ignited engine includes a three-way catalyst (TWC), which operates on the principle of non-selective catalytic reduction of NOx by CO and HC.
Data Source
AI summary
A catalytic converter includes a catalyst. The catalyst includes a non-modified metal oxide support and platinum group metal (PGM) complexes atomically dispersed on the non-modified metal oxide support. The PGM complexes include a PGM species selected from the group consisting of an atom of a platinum group metal, a cluster including from 2 atoms to less than 10 atoms of the platinum group metal, and combinations thereof. An alkali metal or an alkaline earth metal is bonded to the PGM species. The alkali or alkaline earth metal is part of a structure including oxygen atoms and hydrogen atoms.