Intra-crystalline Binary Catalysts for SCR Durability
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Solution Overview
Problem
Current emissions control systems for internal combustion engines, particularly diesel engines, face challenges such as high NOx emissions, urea deposit buildup, and reduced fuel economy due to engine gas recirculation, leading to inefficient emissions control and durability issues with zeolite-based SCR catalysts, especially at low temperatures and cold start conditions.
Innovation Solution
Development of an intra-crystalline binary catalyst composition featuring a zeolite with covalently bound metal oxide nanoparticles, enhancing ammonia storage, NOx reduction, and passive soot oxidation, while maintaining durability and reducing water holding capacity for improved cold-start performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional zeolite-based SCR catalysts are used to reduce NOx emissions, then NOx conversion is achieved, but urea deposit buildup occurs and catalyst durability deteriorates
Solution Approach 1:
The patent employs a composite catalyst system combining Cu-SSZ-13 zeolite with extra-ellipsoidal metal oxide nanoparticles (such as ZrO2, CeO2, or TiO2). This composite structure integrates the high NOx conversion capability of Cu-SSZ-13 with the thermal stability and water resistance properties of metal oxide nanoparticles, thereby maintaining catalyst durability while achieving effective emissions reduction.
Solution Approach 2:
The metal oxide nanoparticles are specifically positioned on the extra-ellipsoidal surface of the Cu-SSZ-13 zeolite crystals rather than within the internal pores. This local placement creates distinct functional zones: the internal zeolite structure handles NOx conversion while the external metal oxide layer provides thermal stability and resistance to urea deposit formation, addressing durability issues without compromising NOx reduction performance.
2Loss of energy
If engine gas recirculation is increased to improve fuel economy, then fuel consumption decreases, but NOx emissions increase and cold start performance deteriorates
Solution Approach 1:
The patent modifies the catalyst's physical and chemical parameters by incorporating metal oxide nanoparticles with different thermal properties and surface characteristics. These parameter changes enable the catalyst to maintain high NOx conversion efficiency across a broader temperature range, including lower temperatures associated with cold starts, thereby decoupling the trade-off between fuel economy and NOx emissions.
3Quantity of substance
If water holding capacity of zeolite is increased to improve ammonia storage, then ammonia storage capacity increases, but cold start performance deteriorates due to heat capacity effects
Solution Approach 1:
The patent creates a spatial differentiation where the internal zeolite structure maintains high water content for ammonia storage, while the external metal oxide nanoparticle layer provides thermal stability. This local quality distinction allows the catalyst to store sufficient ammonia while minimizing the heat capacity penalty during cold starts, as the metal oxide layer on the surface responds more quickly to temperature changes.
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 intra-crystalline binary catalyst composition achieves efficient NOx reduction and passive soot oxidation at low temperatures, improves catalyst durability, and reduces manufacturing costs, addressing the limitations of traditional zeolite-based SCR catalysts in emissions control systems.
Implementation Method 1
a zeolite with covalently bound metal oxide nanoparticles, enhancing ammonia storage
Implementation Method 2
efficient NOx reduction
Implementation Method 3
The SCR system 104 includes a selective catalytic reduction catalyst which interacts with NOx gases to convert the NOx gases into N2 and water
Implementation Method 4
passive soot oxidation
Data Source
AI summary
The present disclosure describes, inter alia, binary catalyst compositions including a (metal) zeolite having a crystal lattice that incorporates a metal oxide, wherein the metal oxide is covalently bound to elements within the crystal lattice. The metal oxide forms an integral part of the (metal) zeolite crystal lattice, forming covalent bonds with at least the Si or Al atoms within the crystal lattice of the (metal) zeolite, and is dispersed throughout the (metal) zeolite crystal lattice. The metal oxide can substitute atoms within the crystal lattice of the (metal) zeolite.