Composite Particles for Exhaust Gas Purification
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Solution Overview
Problem
SAPO-34 zeolite in honeycomb structures for NOx purification is prone to lattice constant changes due to water adsorption and desorption, leading to structural breakage.
Innovation Solution
Composite particles with metallic oxide attached to silicoaluminophosphate particles, optimized in terms of Si to Al and P ratio, specific and external surface areas, and ion-exchanged with copper or iron, are used to form a honeycomb structure that suppresses water-induced contraction and expansion, combined with an inorganic binder and fibers for enhanced strength and NOx purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SAPO-34 zeolite is used for NOx purification, then NOx purification performance is improved, but structural stability deteriorates due to water adsorption-induced lattice constant changes
Solution Approach 1:
The invention uses composite particles comprising silicoaluminophosphate particles with metallic oxide attached thereto. This composite structure combines the high NOx purification performance of SAPO-34 with the structural stability provided by the metallic oxide coating, resolving the contradiction between purification efficiency and structural stability during water adsorption/desorption cycles
Solution Approach 2:
The invention optimizes specific physical parameters of the composite particles including surface area (250-450 m²/g), external surface area (30-90 m²/g), and Si to (Al+P) ratio (0.16-0.33). These parameter optimizations enhance both the NOx purification capability and the resistance to structural changes during water adsorption/desorption
2Productivity
If SAPO-34 adsorbs water, then NOx purification continues, but the honeycomb unit breaks due to contraction from lattice constant change
Solution Approach 1:
The invention controls the surface area and external surface area parameters of composite particles within specific ranges (surface area: 250-450 m²/g, external surface area: 30-90 m²/g). These parameter optimizations allow the material to maintain structural integrity while enabling continuous water adsorption for NOx purification
Solution Approach 2:
The metallic oxide-coated silicoaluminophosphate composite structure provides mechanical reinforcement to the honeycomb units, preventing breakage during the contraction-expansion cycles that occur during continuous water adsorption and desorption operations
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 solution provides a honeycomb structure with excellent NOx purification performance and prevents breakage due to water adsorption and desorption, maintaining structural integrity while achieving high NOx purification rates.
Implementation Method 1
having a metallic oxide attached to silicoaluminophosphate particles
Implementation Method 2
The silicoaluminophosphate particles are desirably ion-exchanged with copper ions and/or iron ions
Implementation Method 3
zeolite is known as a material that adsorbs ammonia in the selective catalytic reduction system
Data Source
AI summary
An object of the invention is to provide composite particles that have excellent NOx purification performance and can suppress water adsorption-caused contraction and water desorption-caused expansion and to provide a honeycomb structure that has excellent NOx purification performance and can suppress the breakage of the honeycomb unit due to the adsorption or desorption of water, a method for manufacturing the honeycomb structure, and an exhaust gas purifying apparatus including the honeycomb structure. The composite particles of the invention are composite particles having a metallic oxide attached to silicoaluminophosphate particles with a ratio of an amount of Si to a sum of amounts of Al and P in a range of 0.16 to 0.33, in which a specific surface area is in a range of 250 m2/g to 450 m2/g, and an external surface area is in a range of 30 m2/g to 90 m2/g.