Amorphous Phase Ammoxidation Catalyst Preventing Mo Dissolution
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Solution Overview
Problem
Existing ammoxidation catalysts for propylene suffer from limited conversion of propylene and selectivity of acrylonitrile due to high crystallinity, which leads to catalyst degradation and reduced catalytic performance.
Innovation Solution
The development of an ammoxidation catalyst with a high amorphous phase content, specifically a catalyst comprising metal oxide represented by Chemical Formula 1, which inhibits Mo dissolution and maintains high catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a catalyst with secondary particle structure is used (metal oxide particles and silica particles agglomerated), then the catalyst can be manufactured through conventional spray drying process, but the catalyst exhibits high crystallinity which leads to easy cracking and Mo dissolution during high temperature operation
Solution Approach 1:
The patent changes the manufacturing parameters by controlling the drying process to produce a catalyst with amorphous phase dominant structure instead of crystalline secondary particles. This parameter change in the drying stage prevents the formation of rigid crystalline structures that would crack under thermal stress, while maintaining manufacturability through modified conventional processing.
Solution Approach 2:
The patent creates a composite catalyst structure where metal oxide components are distributed within an amorphous silica matrix rather than forming separate crystalline agglomerates. This composite approach with amorphous phase dominance provides structural flexibility that prevents cracking while maintaining catalytic activity, and the unique XRD peak pattern serves as a fingerprint for this composite structure.
2Stability of the object's composition
If a catalyst with high crystallinity is used, then the catalyst has defined structure, but the catalyst is easily cracked or broken by high temperature and Mo dissolves from inside to surface, degrading catalytic performance
Solution Approach 1:
The patent inverts the conventional approach by making the amorphous phase dominant rather than the crystalline phase. Instead of accepting crystallinity as the stable structure, the invention uses the amorphous phase as the primary structure that resists thermal cracking and prevents Mo dissolution, while still providing defined catalytic properties through the unique XRD peak characteristics.
3Productivity
If conventional catalysts are used, then the catalyst structure is well-established, but the conversion of propylene and selectivity of acrylonitrile are limited due to catalyst degradation
Solution Approach 1:
The patent changes the structural parameters of the catalyst by establishing a new phase composition ratio where amorphous phase dominates over crystalline phase. This parameter change in phase composition prevents the degradation pathways (cracking and Mo dissolution) that limit conventional catalysts, thereby maintaining high propylene conversion rates and acrylonitrile selectivity over extended operation.
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 higher propylene conversion and acrylonitrile yield by maintaining high catalytic activity and preventing Mo dissolution, compared to traditional catalysts with secondary particle structures.
Implementation Method 1
An ammoxidation process of propylene is based on a mechanism of reduction in which ammonia and propylene are reacted and reoxidized
Data Source
AI summary
An ammoxidation catalyst includes a metal oxide represented by Chemical Formula 1, wherein a first peak having intensity of A appears in the 2θ range of 26.3=0.5°, and a second peak having intensity of B appears in the 2θ range of 28.3±0.5° in X ray diffraction analysis by CuKα, and an intensity ratio (A/B) of the first peak to the second peak is 1.5 or more:MoxBiaFebAcBdCeDfOy Chemical Formula 1wherein in Chemical Formula 1,A and B are different from each other, and each independently, are one or more elements of Ni, Mn, Co, Zn, Mg, Ca, and Ba,C is one or more elements of Li, Na, K, Rb, and Cs,D is one or more elements of Cr, W, B, Al, Ca, and V,a to f, x, and y are respectively mole fractions of each atom or atomic group,a is 0.1 to 7, b is 0.1 to 7, provided that the sum of a and b is 0.1 to 7,c is 0.1 to 10, d is 0.01 to 5, e is 0.1 to 10, f is 0 to 10,x is 11 to 14, y is a value determined by each oxidation number of Mo, Bi, Fe, A, B, C, and D.