Non-Noble Metal Zeolite Adsorbent for Low-Temperature NOx Capture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing passive NOx adsorbents, particularly those with noble metal ions like Pd, exhibit insufficient NO adsorption ability and reusability at low temperatures below 200°C, leading to incomplete NOx removal from engine exhaust gases and high costs due to Pd aggregation and limited loading.
Innovation Solution
A small pore zeolite with an eight-ring framework structure doped with non-noble metal ions such as Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Y3+, La3+, Ce3+, Eu3+, or Yb3+ is used as an adsorbent, enhancing NO adsorption and desorption capabilities at low temperatures through ion-exchange processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Pd loading is increased to enhance NO adsorption ability, then NO adsorption capacity is improved, but Pd aggregation occurs resulting in lower NO/Pd ratios and higher costs
Solution Approach 1:
The patent replaces expensive noble metal Pd with cheaper non-noble metal ions (such as Cu2+, Ni2+, Co2+, Mn2+) that can be loaded at higher concentrations without aggregation. These non-noble metals provide sufficient NO adsorption capacity at lower cost, effectively substituting the expensive Pd-based system while maintaining or improving performance.
Solution Approach 2:
The patent changes the metal ion type from noble (Pd) to non-noble metals, fundamentally altering the chemical properties of the adsorbent. This parameter change enables higher metal loading (from <2 wt% Pd to up to 10 wt% or more of non-noble metals) while preventing aggregation and maintaining stable NO adsorption capacity across multiple cycles.
2Quantity of substance
If Pd loading is increased to enhance NO adsorption ability, then NO adsorption capacity is improved, but the cost of adsorbents increases
Solution Approach 1:
The patent substitutes expensive Pd with abundant, low-cost non-noble metal ions such as Cu2+, Ni2+, Co2+, and Mn2+. These metals can be loaded at significantly higher concentrations (up to 10 wt% or more) without the aggregation issues that plague Pd systems, achieving superior cost-performance ratio while maintaining effective NO adsorption capacity.
3Quantity of substance
If Pd-zeolites are used for NO adsorption, then NO adsorption ability is enhanced, but reusability is insufficient due to poor hydrothermal stability
Solution Approach 1:
The patent replaces Pd with non-noble metal ions that exhibit superior hydrothermal stability in the zeolite framework. Metals such as Cu2+, Ni2+, Co2+, and Mn2+ maintain their dispersed state and adsorption activity after multiple adsorption-desorption cycles and exposure to humid conditions, whereas Pd species suffer from aggregation and deactivation, thereby significantly improving reusability.
4Quantity of substance
If noble metal ions like Pd are used, then NO adsorption sites are provided, but complete NOx removal at temperatures below 200°C is not achieved
Solution Approach 1:
The patent changes the metal ion identity from Pd to non-noble metals with different electronic structures and adsorption characteristics. Metals such as Cu2+ and Ni2+ exhibit stronger interaction with NO molecules, enabling complete NOx removal at temperatures below 200°C, whereas Pd-based systems fail to achieve complete removal in this temperature range despite providing adsorption sites.
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
The non-noble metal-doped zeolite adsorbent achieves effective NO capture and release within the temperature range of 183°C to 460°C, improving NOx removal efficiency and reusability, suitable for exhaust systems in internal combustion engines.
Implementation Method 1
Passive NOx adsorption (PNA) has been considered as one of the approaches for addressing such issue. Typically, PNA involves placing an adsorbent upstream of the SCR process to capture the emitted NO during the cold-start period.
Implementation Method 2
Subsequently, the captured NO can be released at elevated temperatures during engine warming-up, at which the downstream SCR process can efficiently carry out the NOx reduction.
Data Source
AI summary
An adsorbent for passive NOx adsorption includes a small pore zeolite having an eight-ring framework structure and a non-noble metal ion doped in the framework structure. An exhaustion system comprising the adsorbent and a method for preparing the adsorbent are also addressed.