Tubular Alumina Support Pore Structure Optimization
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Solution Overview
Problem
Conventional alumina supports for catalysts in gas-phase reactions face challenges in maintaining high catalytic activity while minimizing by-product formation, as they often exhibit unintended side reactions due to excessive pore volume and activity.
Innovation Solution
An alumina support with a tubular shape, specific pore volume distribution, and structural characteristics, including a BET specific surface area of 140 to 280 m2/g, total pore volume of 0.04 to 0.15 cm3/g, and macropore volume of 0.02 cm3/g or less, is developed, along with a method involving alumina hydrate with multiple particle size distribution peaks and compression molding with a fatty acid metal salt to enhance catalytic activity and reduce by-product yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pore volume of alumina support is increased to enhance catalytic activity, then the catalytic reaction activity is improved, but the by-product formation increases due to unintended side reactions
Solution Approach 1:
The patent applies local quality by creating distinct pore size zones within the alumina support structure. Mesopores (2-50 nm) provide high surface area for catalytic activity, while macropores (50-20000 nm) are controlled to minimal volumes to prevent unwanted side reactions. This spatial differentiation of pore functions allows the support to simultaneously enhance desired catalytic activity while suppressing harmful by-product formation through selective reactant access and product desorption pathways.
2Strength
If compression molding pressure is increased to ensure support strength, then the mechanical strength is improved, but the specific surface area and pore volume decrease
Solution Approach 1:
The patent employs parameter changes by optimizing the compression molding pressure to a specific range (5-20 MPa) that balances mechanical strength development with pore structure preservation. Additionally, the use of alumina hydrate with controlled particle size distribution (D50: 45-100 μm, D10: 1-10 μm, D90: 180-400 μm) and addition of fatty acid metal salt (0.1-5 wt%) modifies the compaction behavior, allowing adequate strength to be achieved without excessive pressure that would collapse the porous structure and reduce surface area.
3Ease of operation
If the macropore volume is increased to improve material transport, then the diffusion of reactants is enhanced, but the catalytic selectivity decreases due to increased side reactions
Solution Approach 1:
The patent utilizes porous materials with a carefully engineered hierarchical pore structure. The alumina support contains controlled volumes of both mesopores (2-50 nm) and macropores (50-20000 nm), with the macropore volume specifically limited to 0.02 cm³/g or less. This porous architecture enables adequate material transport through the larger macropores while the restricted volume prevents excessive residence time that would lead to side reactions, thereby maintaining high catalytic selectivity.
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 alumina support increases catalytic reaction activity and reduces by-product yield, particularly in chlorination reactions, by optimizing pore structure and surface area, leading to high selectivity for dichloroethane production with a copper chloride catalyst.
Implementation Method 1
an alumina compact has high strength and high apparent density, maintains high levels of adsorptive properties and surface activity, and inhibits the shrinkage of mesopores serving as adsorption sites
Data Source
AI summary
An alumina support for a catalyst for a gas-phase reaction that increases the catalytic activity and allows a reduction in by-product yield, and a catalyst for a gas-phase reaction that is a metal compound supported on the alumina support are provided. The alumina support for a catalyst for a gas-phase reaction has a tubular shape with at least one hollow through hole and a BET specific surface area of 140 to 280 m2/g. In this alumina support, a volume (total pore volume) of pores with a diameter of not less than 15 nm and not more than 20000 nm is 0.04 to 0.15 cm3/g, and a volume of pores with a diameter of not less than 1000 nm and not more than 20000 nm is 0.02 cm3/g or less, as measured by the mercury intrusion technique, and a tapped bulk density is 620 to 780 g/L.