Theta-Phase Alumina Catalyst Support for Exhaust Gas Treatment
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Solution Overview
Problem
Catalyst systems using platinum group metals and base metal promoters face challenges in maintaining catalytic activity over the lifetime due to issues like migration and deactivation, particularly when using alpha-phase alumina as a support material.
Innovation Solution
The method involves preparing a gamma-phase alumina support body, passivating it to yield a theta-phase alumina body, and applying catalytic metals like rhodium, copper, or nickel to the passivated theta-phase alumina support, which is then disposed within a shell for exhaust gas treatment, optimizing the catalytic activity and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If gamma-phase alumina support body is used, then high surface area is achieved, but catalytic activity is reduced due to migration and deactivation
Solution Approach 1:
The patent changes the phase parameter of alumina from gamma-phase to theta-phase through controlled passivation heating at 700-1200°C. This phase transformation fundamentally alters the support properties, enabling lower surface area while maintaining catalytic activity through improved metal-support interactions and reduced deactivation mechanisms.
Solution Approach 2:
The patent applies preliminary passivation treatment to the gamma-phase alumina support body before metal deposition. This pre-treatment transforms the support phase and creates optimized surface properties that prevent migration and deactivation during subsequent catalytic operation, rather than addressing these issues after they occur.
2Reliability
If passivation is performed at high temperature for extended period, then theta-phase alumina is formed with improved catalytic properties, but manufacturing time is increased
Solution Approach 1:
The patent optimizes the passivation process by controlling temperature parameters (700-1200°C range) and time parameters (at least 7.5 hours). This parameter optimization achieves complete phase transformation to theta-phase alumina with improved catalytic properties while managing manufacturing time through defined process boundaries.
Solution Approach 2:
The passivation process maintains continuous heating at optimal temperature for the required duration to ensure complete phase transformation. This continuous action ensures thorough theta-phase formation and surface passivation, achieving reliable catalytic performance through uninterrupted process execution.
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
This approach results in enhanced catalytic activity and reduced deactivation, maintaining high performance even with lower surface area catalyst supports, as demonstrated by lower light-off temperatures and improved conversion efficiency of exhaust gas constituents.
Implementation Method 1
passivating the gamma-phase alumina support body to yield a theta-phase alumina support body
Implementation Method 2
heating the gamma-phase alumina support body to a temperature of about 700° C. to about 1,200° C.
Implementation Method 3
The catalytic metal can be applied to the passivated theta-phase alumina support body via impregnation.
Implementation Method 4
The catalytic metal can be applied to the passivated theta-phase alumina support body via precipitation.
Implementation Method 5
convert (e.g., oxidize) various constituents of exhaust gas, such as carbon monoxide (CO), unburned and partially-burned hydrocarbons (HC), and nitrogen monoxide (NO)
Data Source
AI summary
Methods for preparing catalytic systems include passivating a gamma-phase alumina support body to yield a theta-phase alumina support body and applying catalytic metal to passivated theta-phase alumina support body. Passivating can include heating, optionally in the presence of steam. The gamma-phase alumina can be lanthanum-doped gamma-phase alumina and can be about 0.1-55 wt. % lanthanum. The catalytic metal can include rhodium, copper, or nickel. The catalytic metal can be rhodium or nickel, and the catalytic metal can be applied to the passivated theta-phase alumina support body at a loading of about 0.1-10 wt. %. The catalytic metal can be copper, and the catalytic metal can be applied to the passivated theta-phase alumina support body at a loading of about 0.1-30 wt. %. The gamma-phase alumina support body can be at least about 90 wt. % gamma-phase alumina. The passivated theta-phase alumina support body can be at least about 80 wt. % theta-phase alumina.