Mixed Metal Oxide Catalyst for Ammoxidation
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Solution Overview
Problem
Historical catalysts for ammoxidation of propylene to acrylonitrile often resulted in increased acrylonitrile yield at the expense of hydrogen cyanide and acetonitrile yields, limiting overall conversion efficiency.
Innovation Solution
A novel catalyst composition comprising a complex of metal oxides with specific atomic ratios of bismuth, iron, and other elements, including sodium, potassium, nickel, and molybdenum, which maintains high acrylonitrile production while preserving hydrogen cyanide and acetonitrile yields, achieved through a unique preparation process involving a precipitate slurry formation and calcination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional bismuth-molybdenum-iron catalysts are used to increase acrylonitrile yield, then acrylonitrile production is improved, but hydrogen cyanide and acetonitrile yields decrease
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic ratios of metal components (Bi: 0.05-7, Fe: 0.1-7, Mo: 12, Ce: 0.01-5, Al: 0-5, Na: 0-5, K: 0-5, Ca: 0-5, Mg: 0-5) and the preparation conditions (calcination temperature 400-600°C, precipitate slurry composition) to achieve a catalyst that produces high acrylonitrile yield without significantly reducing hydrogen cyanide and acetonitrile yields, thus resolving the trade-off between main product and coproduct yields
Solution Approach 2:
The patent uses composite materials by creating a complex multi-metal oxide catalyst system combining bismuth, molybdenum, iron, cerium, aluminum, and optional alkali/alkaline earth metals. This composite catalyst structure synergistically enhances acrylonitrile production while maintaining coproduct yields, overcoming the limitations of simpler binary or ternary catalyst systems
2Reliability
If complex multi-step catalyst preparation processes are used, then catalyst performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple preparation steps into a more integrated process by forming a precipitate slurry containing multiple metal components (Bi, Mo, Ce, Al, Na, K, Ca, Mg) simultaneously, then calcining the combined slurry in one step. This combining approach maintains catalyst performance while reducing the number of separate preparation operations compared to traditional sequential methods
Solution Approach 2:
The patent applies preliminary action by preparing a precipitate slurry that pre-positions multiple metal components in specific ratios before final calcination. This preliminary formation of the precipitate structure ensures proper distribution and interaction of metal oxides, achieving high catalyst performance while simplifying the overall preparation workflow
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 greater overall conversion of propylene to acrylonitrile, hydrogen cyanide, and acetonitrile, with improved attrition resistance and stability, as evidenced by higher yields and lower attrition losses compared to conventional methods.
Implementation Method 1
contacting at an elevated temperature, propylene, ammonia and oxygen in the vapor phase in the presence of a catalyst, said catalyst comprising a complex of metal oxides
Implementation Method 2
achieved through a unique preparation process involving a precipitate slurry formation and calcination
Implementation Method 3
achieved through a unique preparation process involving a precipitate slurry formation and calcination
Data Source
AI summary
A process and novel catalyst for the production of acrylonitrile, acetonitrile and hydrogen cyanide characterized by the relative yields of acrylonitrile, acetonitrile and hydrogen cyanide produced in the process and by the catalyst, which are defined by the following:α=[(% AN+(3×% HCN)+(1.5×% ACN))÷% PC]×100wherein % AN is the Acrylonitrile Yield and % AN≧81,% HCN is the Hydrogen Cyanide Yield,% ACN is the Acetonitrile Yield,% PC is the Propylene Conversion, andα is greater than 100.