Complex Oxide Catalyst Preparation Using Citric Acid Complexing Agent
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Solution Overview
Problem
The complexity of catalyst components with varying solubility leads to uneven distribution, affecting performance, and high temperatures required for drying result in waste and toxicity issues in the preparation of complex oxide catalysts for selective oxidation of light alkenes to unsaturated aldehydes, while maintaining high selectivity and stability remains a challenge.
Innovation Solution
A preparation process involving a complexing agent to dissolve precursor salts evenly, followed by drying, molding, and calcination, using a catalyst formula x(Mo12BiaFebCocAdDeOf)/yZ with a heat conduction agent, allowing for milder reaction conditions and prolonged catalyst lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If coprecipitation method is used to prepare complex oxide catalysts with multiple elements, then the catalyst can be prepared with complete components, but the precursor salts with different solubility will result in uneven distribution of catalyst components
Solution Approach 1:
The patent introduces a complexing agent (such as citric acid, ethylenediaminetetraacetic acid, or tartaric acid) as an intermediary substance that forms soluble complexes with metal ions. This complexing agent acts as a mediator that enables uniform dissolution of all precursor salts regardless of their inherent solubility differences, thereby achieving uniform catalyst component distribution without requiring separate dissolution steps for each precursor.
2Quantity of substance
If a huge amount of water is used to dissolve low solubility compounds, then the precursor salts can be dissolved completely, but a lot of heat is wasted during drying and calcining process
Solution Approach 1:
The patent changes the chemical parameters of the dissolution system by introducing complexing agents that alter the solubility characteristics of precursor salts. Instead of using excessive water to achieve dissolution, the complexing agents form stable soluble complexes with metal ions, enabling complete dissolution with minimal water. This parameter change in the chemical environment directly reduces the water content that needs to be evaporated, thereby reducing energy consumption during drying and calcining.
3Manufacturing precision
If pH value is lowered by adding acids to dissolve precursor salts, then the catalyst components can be dissolved evenly, but excess acids corrode reaction devices and produce toxic NOx gas
Solution Approach 1:
The patent replaces the use of strong mineral acids (such as nitric acid and hydrochloric acid) with organic complexing agents (such as citric acid, ethylenediaminetetraacetic acid, or tartaric acid). These organic agents are environmentally friendly, non-corrosive, and do not produce toxic gases during heating. They achieve the same purpose of uniform dissolution through complex formation, eliminating the harmful effects associated with strong acids while maintaining the uniformity of catalyst component distribution.
4Productivity
If high temperature is used to increase catalyst activity, then the conversion of alkene can be improved, but the selectivity to unsaturated aldehydes decreases and catalyst life span is reduced
Solution Approach 1:
The patent introduces a heat conduction agent (such as aluminum oxide, silicon carbide, or graphite) into the catalyst structure. This heat conduction agent improves the thermal conductivity of the catalyst, enabling more efficient and uniform heat distribution throughout the catalyst bed. This thermal management allows the catalyst to operate at lower temperatures while maintaining high activity, thereby improving selectivity to unsaturated aldehydes and extending catalyst life span without sacrificing productivity.
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 process achieves high activity, selectivity, and stability of the catalyst, simplifying the preparation and making it suitable for mass production while reducing operational complexity and environmental impact.
Implementation Method 1
adding a complexing agent during the dissolving process of the precursor salts
Implementation Method 2
drying, molding, and calcination
Implementation Method 3
calcining
Data Source
AI summary
The present invention provides a preparation process of complex oxides catalyst containing Mo, Bi, Fe and Co, which comprising steps as following: dissolving precursor compounds of the components for catalyst and complexing agent in water to obtain a solution, and then drying, molding and calcining the solution to obtain catalyst. The catalyst is used for gas phase oxidation of light alkenes to unsaturated aldehydes. The catalyst has high activity, selectivity and stability. The reaction condition is mild. The preparation process of the catalyst is easy to operate and can be used for mass production.