Composite Zeolite SCR Catalyst for Diesel NOx Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current SCR catalysts for diesel engines face challenges with low low-temperature NH3-SCR catalytic activity, poor thermal stability, complex composition, and high preparation costs, which hinder effective NOx reduction and fuel efficiency.
Innovation Solution
A composite zeolite SCR catalyst comprising a Cu-based zeolite and a hydrogen-type zeolite, with a specific mass ratio and hydrothermal treatment, offering improved NOx removal efficiency and stability at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high-silica zeolite catalysts are employed to ensure stability, then thermal stability is improved, but low-temperature NH3-SCR catalytic activity deteriorates
Solution Approach 1:
The patent employs a composite zeolite structure combining high-silica CHA zeolite (providing thermal stability) with copper ions and alkali metal cations (enhancing low-temperature catalytic activity). The composite catalyst integrates the advantages of different materials: the stable CHA framework maintains structural integrity at high temperatures, while the copper-alkali metal active sites promote NH3-SCR reactions at low temperatures, thus resolving the contradiction between thermal stability and low-temperature activity.
Solution Approach 2:
The patent applies local quality by creating distinct functional zones within the zeolite structure. The high-silica CHA framework provides the stable structural backbone, while specific regions containing copper ions and alkali metal cations (particularly at exchange sites and pore surfaces) provide enhanced catalytic activity. This spatial differentiation of properties allows the catalyst to simultaneously achieve thermal stability from the framework and low-temperature activity from the active sites.
2Reliability
If aluminum-rich zeolite molecular sieve catalysts are used to achieve excellent NH3-SCR catalytic activity, then low-temperature catalytic activity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent creates a composite system where aluminum-rich active sites (providing high catalytic activity) are embedded within a high-silica CHA framework (providing thermal stability). The copper ions and alkali metal cations are introduced into the high-silica framework, creating aluminum-containing active centers that enhance NH3-SCR activity while the overall high-silica structure maintains thermal stability, thus resolving the contradiction between activity and stability.
3Reliability
If complex composition catalysts are used to improve NOx removal efficiency, then catalytic performance is improved, but preparation cost deteriorates
Solution Approach 1:
The patent optimizes the composition parameters by precisely controlling the Si/Al ratio, copper content (2-7 wt% CuO), and alkali metal content (0.1-0.4 wt% pure metal) within specific ranges. This parameter optimization achieves high NOx removal efficiency while avoiding excessive use of expensive materials. The controlled composition ensures catalytic performance without requiring complex multi-component formulations, thus reducing preparation costs.
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 composite catalyst achieves NOx removal efficiency of over 80% at 300°C and maintains stability after hydrothermal treatment, providing a cost-effective and efficient solution for diesel engine emissions reduction.
Implementation Method 1
The main technical means to purify NOx emissions from diesel vehicles and diesel engines is to convert nitrogen oxides to N2 by selective catalytic reduction with ammonia (NH3) as a reductant (NH3-SCR), the central to which is the utilization of high-performance NH3-SCR catalysts.
Implementation Method 2
Cu-based zeolite and hydrogen-type zeolite composite catalyst... achieves NOx removal efficiency of over 80% at 300°C
Data Source
AI summary
Disclosed are a composite zeolite SCR catalyst, a preparation method therefor and use thereof. The composite zeolite SCR catalyst comprises a Cu-based zeolite and a first hydrogen-type zeolite; the composite zeolite SCR catalyst has a NOx removal efficiency of more than or equal to 80% at more than or equal to 300° C.; the composite zeolite SCR catalyst is subjected to hydrothermal treatment at 750-950° C. for 10-16 h, and the hydrothermally treated composite zeolite SCR catalyst has a NOx removal efficiency of more than or equal to 60% at more than or equal to 300° C. The composite zeolite SCR catalyst of the present application is used in the technology of selective catalytic reduction on nitrogen oxides with ammonia, and the composite zeolite SCR catalyst has simple composition, low preparation cost, great catalytic performance and good hydrothermal stability.