Bi-Metal Molecular Sieve Catalyst Sulfur Poisoning Resistance
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Solution Overview
Problem
Copper-based SCR catalysts are prone to sulfur poisoning, leading to deactivation in exhaust gases from lean burn engines, which limits their effectiveness in reducing NOx emissions, especially at low temperatures.
Innovation Solution
A bi-metal molecular sieve catalyst promoted with nickel and copper, where both metals are incorporated during synthesis, providing improved resistance to sulfur poisoning and maintaining high NOx conversion performance even in high-sulfur environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper-based SCR catalysts are used to reduce NOx emissions, then NOx conversion performance is improved, but the catalyst is easily poisoned and deactivated by sulfur in exhaust gases
Solution Approach 1:
The patent introduces a bi-metallic system comprising copper and iron as intermediary elements that work synergistically. The iron component acts as a mediator that enhances the copper catalyst's resistance to sulfur poisoning while maintaining NOx conversion activity, effectively protecting the catalyst from direct sulfur deactivation
Solution Approach 2:
The patent employs a composite catalyst material combining copper and iron in specific ratios (Cu:Fe = 1:2 to 2:1) within a molecular sieve structure. This composite approach creates a synergistic effect where the iron component compensates for copper's sulfur sensitivity, resulting in a catalyst that maintains both high NOx conversion and sulfur tolerance
2Object-affected harmful factors
If nickel is added to promote sulfur resistance, then resistance to sulfur poisoning is improved, but NOx conversion performance at low temperatures deteriorates
Solution Approach 1:
The patent optimizes the nickel content parameter within a specific range (0.5-5 wt%) and controls the Cu:Ni:Fe ratio to balance sulfur resistance and low-temperature activity. By adjusting these compositional parameters, the catalyst achieves both sulfur tolerance and maintained NOx conversion at low temperatures
Solution Approach 2:
The patent creates different functional zones within the catalyst structure where nickel provides sulfur resistance in high-sulfur environments while copper and iron maintain catalytic activity for NOx reduction. The spatial distribution and synergistic interaction of these metals create local functional regions that address both requirements simultaneously
3Productivity
If copper content is increased to improve NOx conversion, then NOx conversion performance is improved, but susceptibility to sulfur poisoning increases
Solution Approach 1:
The patent creates a composite catalyst system where copper (0.5-5 wt%), iron (0.5-5 wt%), and nickel (0.5-5 wt%) are combined in optimized ratios. This composite structure allows the copper component to provide high NOx conversion activity while the iron and nickel components collectively protect against sulfur poisoning, achieving both high productivity and sulfur resistance
Solution Approach 2:
The iron and nickel components serve as protective intermediaries that reduce the copper catalyst's exposure to sulfur. These metals interact with sulfur species preferentially or create a protective environment around the copper sites, allowing high copper content for NOx conversion without proportional increase in sulfur sensitivity
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 nickel-promoted catalyst achieves consistently high NOx conversion at low temperatures and resists deactivation, requiring less frequent regenerations and maintaining catalytic activity in high-sulfur conditions, thus improving environmental air quality and reducing emissions from engines and power plants.
Implementation Method 1
a method for treating an exhaust gas comprising contacting a gas comprising NOx and ammonia reductant with a catalyst to catalytically reduce at least a portion of the NOx to N2
Implementation Method 2
0.5 - 5 weight percent of a transition metal (TM) which is copper, based on the total weight of the molecular sieve, and 0.5 - 5 weight percent nickel, based on the total weight of the molecular sieve, wherein the transition metal and nickel are present in a TM:Ni ratio of about 10:1 to about 1:2, and wherein a majority of the transition metal and nickel are present as extra framework metals
Data Source
Figure 1
AI summary
Provided is a catalyst composition comprising a small pore molecular sieve, about 0.5 - 5 weight percent of a transition metal (TM) selected from copper and/or iron, based on the total weight of the zeolite, and about 0.5 - 5 weight percent nickel, based on the total weight of the molecular sieve, wherein the transition metal and nickel are present in a TM:Ni ratio of about 10:1 to about 1:2. Also provided is a synthesis method for preparing a small pore molecular sieve having both Cu and Ni incorporated in situ. Also provided is a method for using such a catalyst for selectively reducing NOx in an exhaust gas.