Alpha Alumina Catalyst Carriers: Caustic Control of Small Pores
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Solution Overview
Problem
Existing alpha alumina carriers for ethylene oxide catalysts have undesirable small pore sizes below 0.3 microns, which negatively impact catalyst performance, and these pore sizes are difficult to control.
Innovation Solution
Treat preformed catalyst carriers with a hot caustic solution and calcine them at high temperatures to reduce the pore volume percentage of small pores below 0.3 microns, or add a caustic solution during catalyst carrier formation to achieve a similar reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alpha alumina carriers are used, then the catalyst carrier structure is simple and easy to manufacture, but the small pore size distribution below 0.3 microns cannot be controlled and negatively impacts catalyst performance
Solution Approach 1:
The patent applies preliminary action by adding a caustic solution to the carrier composition during the preparation stage, before the carrier is formed and calcined. This preliminary treatment modifies the pore structure formation process, ensuring that small pores below 0.3 microns are reduced from the outset rather than requiring post-processing adjustments. The caustic solution is incorporated into the slurry or paste used to form the carrier, allowing pore structure control to be built-in during manufacturing.
Solution Approach 2:
The patent employs parameter changes by introducing a caustic solution (changing the chemical composition parameter) and controlling the calcination temperature (changing the thermal parameter) to transform the pore size distribution. The caustic solution alters the chemical environment during formation, and the high-temperature calcination (typically 1100-1500°C) physically transforms the pore structure, shifting the pore size distribution to eliminate harmful small pores while maintaining larger functional pores.
2Manufacturing precision
If the carrier is treated with hot caustic solution and calcined, then the small pore volume percentage is reduced, but the processing time and temperature requirements increase
Solution Approach 1:
The patent utilizes phase transitions by subjecting the carrier to high-temperature calcination (typically 1100-1500°C), which causes physical and chemical transformations in the alumina structure. During calcination, the carrier undergoes phase changes that densify the material and collapse small pores, while the porous structure and larger pores are maintained. This thermal phase transition efficiently reduces small pore volume in a single processing step, achieving precise pore control without requiring prolonged treatment at multiple temperature stages.
3Manufacturing precision
If caustic solution is added during carrier formation, then the small pore distribution is reduced, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies merging by combining the pore structure modification function with the existing carrier formation process. Instead of adding a separate treatment step, the caustic solution is incorporated into the carrier composition slurry or paste during the normal mixing and forming operations. This integration allows the pore structure control to be achieved through a modified version of the existing manufacturing process, maintaining ease of manufacture while improving pore size distribution precision.
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 method effectively shifts the small pore size distribution to larger pores, improving catalyst performance by reducing the volume of pores below 0.3 microns and enhancing properties like surface area, water absorption, and crush strength.
Implementation Method 1
contacting a preformed catalyst carrier having a pore size distribution of less than 0.3 microns with a caustic solution to provide an admixture of the caustic solution and the preformed catalyst carrier
Implementation Method 2
the admixture is heated to a temperature of about 70° C. or greater to provide a caustic solution treated preformed catalyst carrier
Implementation Method 3
The dried caustic solution treated preformed catalyst carrier is then calcined at a temperature of about 1200° C. or greater
Implementation Method 4
contacting a preformed catalyst carrier having a pore size distribution of less than 0.3 microns with a caustic solution
Data Source
AI summary
Methods are provided in which small pores having a size of less than 0.3 microns are substantially reduced by utilizing a caustic solution. In some embodiments, the reduction of the small sized pores of less than 0.3 microns is achieved by treating a preformed catalyst carrier with a hot caustic solution. In other embodiments, the reduction of small sized pores of less than 0.3 microns is achieved by adding a caustic solution to a carrier composition during the preparation/formation of a catalyst carrier. The caustic solution treated catalyst carrier exhibits a positive/upward shift of the small pore size distribution.