Zeolite-Modified Precious Metal Catalyst for Silicon Poisoning
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Solution Overview
Problem
Existing catalysts used for purifying exhaust gases containing organic and silicon compounds suffer from decreased catalytic activity due to silicon poisoning, requiring complex reactor structures and inefficient removal methods, and lack cost-effective solutions for high space velocity applications.
Innovation Solution
A catalyst composition combining alumina with precious metals and zeolite, where the zeolite is used in a range of 1 wt.% to 70 wt.% relative to alumina, with optional zeolite acid content and precious metal carriers like Pt, Pd, Rh, or Ru, to maintain long-term activity and silicon resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a precious metal-carried alumina catalyst is used for treating exhaust gas containing silicon compounds, then the catalyst can oxidize organic compounds effectively, but silicon poisons the precious metal causing decreased catalytic activity
Solution Approach 1:
The patent introduces zeolite as an intermediary substance that selectively adsorbs silicon compounds from the exhaust gas, preventing them from reaching and poisoning the precious metal catalyst. The zeolite acts as a protective barrier, allowing the precious metal to maintain its catalytic activity while still oxidizing organic compounds effectively.
Solution Approach 2:
The patent creates a composite catalyst system combining precious metal-carried alumina with zeolite. This composite structure integrates the oxidation capability of precious metal with the silicon-removal capability of zeolite, achieving both functions in a single catalyst bed without requiring separate stages.
2Reliability
If an adsorbent containing alkali metal or alkaline earth metal is provided in the preceding stage to remove silicon compounds, then silicon poisoning is prevented, but the reactor structure becomes complicated and high boiling substances accumulate causing safety issues
Solution Approach 1:
The patent merges the silicon removal function and organic compound oxidation function into a single catalyst bed by combining zeolite and precious metal-carried alumina. This eliminates the need for separate preceding and succeeding stages, simplifying the reactor structure to a single-stage system while maintaining silicon resistance and oxidation capability.
Solution Approach 2:
The patent makes the single catalyst bed universally functional by incorporating both zeolite (for silicon removal) and precious metal-carried alumina (for organic compound oxidation). This multi-functional catalyst performs multiple tasks simultaneously: removing silicon compounds, preventing catalyst poisoning, and oxidizing organic compounds, eliminating the need for specialized preceding stages.
3Reliability
If zeolite is used as a carrier for precious metal to treat exhaust gas containing silicon compounds, then catalytic activity is maintained, but the cost increases due to expensive zeolite material
Solution Approach 1:
The patent uses a composite structure where zeolite and precious metal-carried alumina work together. The zeolite removes silicon compounds while the alumina supports the precious metal for oxidation reactions. This composite approach allows the use of less expensive alumina as the primary support while incorporating only the necessary amount of zeolite for silicon removal, reducing overall material cost compared to using zeolite as the sole carrier.
Solution Approach 2:
The patent effectively divides the functions between two materials: zeolite handles silicon removal while alumina handles organic compound oxidation. This functional copying allows each material to specialize in its optimal role, with alumina serving as a cost-effective support for precious metal that doesn't require the expensive zeolite structure for its oxidation function.
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 catalyst composition effectively maintains high catalytic activity over time, suppressing changes in organic compound removal rates and improving silicon resistance, allowing for efficient purification of exhaust gases at high space velocities with reduced zeolite usage and simplified reactor designs.
Implementation Method 1
Precious metal-carried alumina catalysts, which oxidize organic compounds to remove them
Implementation Method 2
providing an adsorbent, such as zeolite, alumina or activated carbon... so that silicone is removed in the preceding stage
Data Source
AI summary
The challenge for the present invention is to provide a catalyst composition restrained from declining in performance over time in purifying an exhaust gas containing an organic compound a silicon compound, a catalyst containing the catalyst composition, and a method for producing the catalyst.This challenge is solved by using a catalyst composition containing zeolite added to precious metal-carried alumina, and the silicon resistance of the catalyst is improved greatly. The amount of acid of the zeolite added is preferably in the range of 0.4 mmol·NH3/g to 1.5 mmol·NH3/g.