Silica Layer Thickness Control for Uniform Zeolite Support
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Solution Overview
Problem
Existing honeycomb catalyst bodies used in urea-SCR devices for NOx conversion suffer from insufficient NOx conversion efficiency due to nonuniform support of zeolite catalysts, either from too-thin silica layers causing catalyst piling in neck portions or too-thick layers that bury pores, leading to gas flow issues.
Innovation Solution
A honeycomb catalyst body with a silica layer of 5 to 100 nm thickness on silicon carbide particles, supporting zeolite at 50 g/L or more, ensures uniform catalyst distribution and maintains effective gas flow by avoiding pore burial, thereby enhancing NOx conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silica layer is formed on silicon carbide particles to support catalyst, then catalyst support uniformity is improved, but gas flow may be blocked if the layer is too thick
Solution Approach 1:
The patent applies parameter changes by precisely controlling the silica layer thickness within the range of 5 to 100 nm. This specific thickness parameter ensures that the catalyst is uniformly supported while preventing pore burial that would block gas flow. The oxidation treatment conditions (temperature, time, atmosphere) are also optimized to achieve this critical thickness parameter.
2Manufacturing precision
If silica layer thickness is increased to improve catalyst support, then catalyst distribution uniformity improves, but pore burial occurs leading to pressure loss
Solution Approach 1:
The patent resolves this contradiction by establishing the optimal silica layer thickness parameter of 5 to 100 nm. This parameter range is critical: it is thick enough to provide uniform catalyst support but thin enough to prevent pore burial. The patent also controls the oxidation treatment parameters (temperature, time, atmosphere) to achieve and maintain this critical thickness.
3Productivity
If zeolite catalyst is supported at high loading (50 g/L or more), then NOx conversion efficiency is improved, but catalyst aggregation may occur without proper silica layer
Solution Approach 1:
The patent uses the silica layer as an intermediary between the silicon carbide particles and the zeolite catalyst. This intermediate layer provides a uniform support surface that prevents catalyst aggregation even at high loading densities of 50 g/L or more. The silica layer acts as a mediator that enables high catalyst loading while maintaining uniform distribution.
4Manufacturing precision
If oxidation treatment is performed at high temperature for long duration to form silica layer, then silica layer formation is improved, but manufacturing time and energy consumption increase
Solution Approach 1:
The patent optimizes the oxidation treatment parameters to achieve the desired silica layer thickness of 5 to 100 nm in a reasonable time frame. By controlling temperature, atmosphere composition, and treatment duration, the patent achieves effective silica layer formation without excessive manufacturing time or energy consumption. The specific parameter combination balances quality and efficiency.
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 controlled silica layer thickness and adequate zeolite loading ensure uniform catalyst support, significantly improving NOx conversion efficiency in urea-SCR devices while preventing pressure loss and maintaining effective gas flow.
Implementation Method 1
a silica layer is formed on the surface of each of the silicon carbide particles
Implementation Method 2
the catalyst is supported on the surface of each of the silicon carbide particles via the silica layer therebetween
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3~4
AI summary
The honeycomb catalyst body of the present invention includes: a honeycomb structured body including a porous honeycomb fired body having a large number of cells longitudinally placed in parallel with one another with a cell wall interposed therebetween, the honeycomb fired body being mainly made of silicon carbide particles; and a catalyst containing oxide ceramics or zeolite, the catalyst being supported on the honeycomb structured body, wherein a silica layer is formed on a surface of each of the silicon carbide particles, the catalyst is supported on the surface of each of the silicon carbide particles via the silica layer therebetween, the silica layer has a thickness measured by X-ray photoelectron spectroscopy (XPS) of 5 to 100 nm, and an amount of the oxide ceramics or the zeolite supported is 50 g/L or more.