Mo-Bi-Fe Catalyst Calcination Rate Control
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Solution Overview
Problem
Existing Mo—Bi—Fe catalysts used in the ammoxidation process for producing unsaturated nitriles have limitations in terms of catalytic efficiency, with room for improvement in reaction product yield.
Innovation Solution
A method for producing a Mo—Bi—Fe catalyst involving a slurry preparation step with a low decomposition temperature additive, followed by controlled calcination with a temperature raising rate of 10° C./min or less, and gas replacement in the calcination atmosphere within 180 seconds, to optimize the catalyst's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a slurry containing additive with low decomposition temperature is used and temperature is raised rapidly during calcination, then productivity is improved, but catalyst performance deteriorates
Solution Approach 1:
The calcination process is divided into multiple temperature stages: a first calcination at 200-400°C to remove the additive, followed by a second calcination at 400-700°C to form the catalyst. This segmentation allows controlled removal of the additive without compromising catalyst performance, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The additive is introduced into the slurry before calcination to improve dispersion of metal compounds. The additive decomposes during the first calcination stage, leaving behind improved dispersion characteristics in the final catalyst. This preliminary action enables better catalyst performance while maintaining efficient calcination.
2Loss of time
If temperature raising rate is increased during calcination, then production time is reduced, but unsaturated nitrile yield decreases
Solution Approach 1:
The calcination is segmented into two distinct temperature zones with different heating rates. The first stage (200-400°C) uses a controlled heating rate to remove the additive, while the second stage (400-700°C) can use faster heating. This segmentation reduces total calcination time while maintaining high unsaturated nitrile yield by protecting the catalyst formation process.
3Reliability
If additive is added to improve metal compound dispersion, then catalyst activity is improved, but catalyst stability deteriorates due to excessive temperature raising
Solution Approach 1:
The additive is added to the slurry before calcination to achieve optimal dispersion of metal compounds. During the first calcination stage at 200-400°C, the additive decomposes and leaves behind the dispersed metal oxide structure. This preliminary dispersion action ensures high catalyst activity while the controlled temperature profile maintains composition stability.
Solution Approach 2:
The heating rate is optimized as a critical parameter: 1-10°C/min during the first calcination to allow additive decomposition without disrupting the dispersed structure, and 10-50°C/min during the second calcination to form the final catalyst. This parameter optimization maintains both activity and stability.
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 results in a catalyst with enhanced catalytic efficiency, achieving a high yield of unsaturated nitriles such as acrylonitrile during the ammoxidation process.
Implementation Method 1
an additive having a decomposition temperature of 500° C. or less
Implementation Method 2
a calcination step of calcining the dried material to obtain a calcined material
Implementation Method 3
a step of bringing an olefin into contact with ammonia and molecular oxygen in a presence of the catalyst to produce the unsaturated nitrile
Data Source
AI summary
A method for producing a catalyst, including a slurry preparation step of preparing a slurry comprising a Mo compound, an Fe compound, a Bi compound, and an additive having a decomposition temperature of 500° C. or less; a drying step of drying the slurry to obtain a dried material; and a calcination step of calcining the dried material to obtain a calcined material, wherein the calcination step comprises a step of raising temperature of a calcination atmosphere to a predetermined temperature, and a temperature raising rate is 10° C./min or less at least at a temperature equal to or lower than the decomposition temperature of the additive.