Layered Propylene Ammoxidation Catalyst Coating for Molybdenum Stability
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Solution Overview
Problem
Existing ammoxidation catalysts for propylene, particularly those based on the sol-gel process, suffer from limited yield of acrylonitrile due to molybdenum (Mo) dissolution and evaporation, necessitating continuous catalyst make-up, and have restricted active sites to the external surface of secondary particles.
Innovation Solution
An ammoxidation catalyst is developed with a structure where molybdenum oxide is initially supported in a silica carrier, followed by heterogeneous metals like bismuth, forming a multi-layered coating to stabilize Mo and enhance catalytic performance, with specific metal compositions and support methods to inhibit Mo evaporation and increase active sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sol-gel process is used to prepare the catalyst, then the catalyst can be manufactured with a secondary particle structure, but the weak binding force causes primary particles to split and lose catalytic activity, and metal oxide components evaporate at high temperature
Solution Approach 1:
The patent uses a composite material structure where metal oxide particles are embedded within a silica matrix. This composite approach strengthens the binding between primary particles, preventing splitting and metal oxide evaporation at high temperatures while maintaining the secondary particle structure needed for manufacturing
Solution Approach 2:
The catalyst employs a porous silica matrix that provides a stable framework for supporting metal oxide particles. The porous structure allows for high surface area and active site availability while the matrix itself provides mechanical strength and thermal stability to prevent particle disintegration
2Ease of manufacture
If the catalyst is prepared by sol-gel process with secondary particle structure, then manufacturing is simplified, but the active sites are limited to external surface only, providing small surface area
Solution Approach 1:
The catalyst utilizes a porous silica matrix structure that provides both internal and external surfaces for catalytic activity. The porous architecture increases the total surface area available for reactions while maintaining the secondary particle morphology needed for easy manufacturing and fluidized bed operation
3Productivity
If Mo oxide is used as catalyst component, then catalytic activity for propylene ammoxidation is achieved, but Mo dissolves and evaporates during reaction, requiring continuous make-up
Solution Approach 1:
The porous silica matrix acts as a physical barrier that anchors metal oxide particles, preventing their dissolution and evaporation during high-temperature propylene ammoxidation reactions while still allowing reactants and products to diffuse through the porous structure for maintained productivity
Solution Approach 2:
The composite structure of metal oxide particles embedded in silica matrix creates a stable configuration where the silica component prevents metal oxide loss through dissolution and evaporation, enabling continuous operation without frequent catalyst make-up
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 achieves high yield of acrylonitrile without additional catalyst supply, maintaining catalytic performance by stabilizing Mo and increasing active sites through controlled support and composition, thereby enhancing propylene conversion and selectivity.
Implementation Method 1
molybdenum (Mo) oxide is supported first, and an oxide of heterogeneous metal including bismuth (Bi) is supported later
Implementation Method 2
The catalyst of one embodiment can inhibit dissolution of molybdenum (Mo) and maintain catalytic performance during the ammoxidation reaction of propylene
Data Source
AI summary
There is provided an ammoxidation catalyst for propylene having a structure in which molybdenum (Mo) oxide is supported first, and an oxide of heterogeneous metals including bismuth (Bi) is supported later. Related methods of making and using the catalyst are also provided.