Antimony-Enriched Catalyst for Selective Oxidation
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Solution Overview
Problem
Catalysts used for producing unsaturated aldehydes and unsaturated carboxylic acids through gas phase oxidation reactions, such as those containing molybdenum, tungsten, cesium, antimony, bismuth, iron, nickel, cobalt, and lead, often have insufficient performance and generate many by-products, affecting yield.
Innovation Solution
A catalyst comprising molybdenum, bismuth, antimony, and iron with a specific atom ratio of antimony to molybdenum on the surface greater than in the entire catalyst, optimized using Inductively Coupled Plasma (ICP) and X-ray photoelectron spectroscopy (XPS) ratios, and potentially including additional elements like cobalt and cesium, to enhance selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal oxide catalysts containing multiple elements (molybdenum, tungsten, cesium, antimony, bismuth, iron, nickel, cobalt, and lead) are used for gas phase oxidation, then the catalyst can perform the oxidation reaction, but the selectivity is insufficient and many by-products are generated
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of antimony within the catalyst, specifically concentrating antimony on the catalyst surface through controlled impregnation sequences. This surface enrichment of antimony (achieved by adding antimony after other metals and controlling drying/calcination conditions) creates regions with different compositional properties: the surface layer has high antimony content for selective oxidation, while the bulk maintains the full multi-element composition for structural stability and catalytic activity.
Solution Approach 2:
The patent employs parameter changes by systematically varying the addition sequence and concentration of metal salts during catalyst preparation. Key parameters include: adding antimony at a later stage (after Mo, W, Bi, Fe, Ni, Co are already present), controlling the molar ratios of each metal, adjusting impregnation times and temperatures, and optimizing calcination conditions. These parameter changes result in a catalyst with enhanced selectivity where antimony surface concentration reaches 2-5 times the bulk concentration, thereby reducing by-product formation while maintaining catalytic performance.
2Productivity
If the catalyst composition is optimized to improve selectivity, then the yield of unsaturated aldehydes and carboxylic acids increases, but the catalyst preparation becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-establishing a stable multi-metal oxide framework (containing Mo, W, Bi, Fe, Ni, Co) through systematic impregnation and calcination before introducing antimony in the final impregnation step. This preliminary formation of the base catalyst structure provides a stable support that directs the subsequent antimony distribution, ensuring surface enrichment without requiring complex multi-step procedures. The pre-formed framework acts as a template that simplifies the overall preparation process while achieving the desired compositional gradient.
Solution Approach 2:
The patent employs segmentation by dividing the catalyst preparation into distinct sequential stages: (1) initial impregnation of Mo, W, Bi, Fe, Ni, Co salts followed by drying and calcination to form the base oxide framework, (2) subsequent impregnation of antimony salt, (3) final drying and calcination to achieve surface-enriched antimony distribution. This segmented approach allows each metal to be optimally positioned and distributed, with antimony specifically concentrated on the surface, thereby achieving high selectivity through controlled compositional zoning without requiring overly complex simultaneous multi-metal deposition procedures.
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
Improves the selectivity of unsaturated aldehydes and unsaturated carboxylic acids production by optimizing the antimony distribution, leading to higher yields and reduced by-product formation.
Implementation Method 1
Methods for producing an unsaturated aldehyde or an unsaturated carboxylic acid by performing a gas phase oxidation reaction in the presence of a metal oxide catalyst using an organic compound such as propylene, isobutylene, t-butyl alcohol, or methyl-t-butyl ether are known
Implementation Method 2
A is an atom ratio of the antimony to the molybdenum calculated by Inductively Coupled Plasma (ICP) emission spectroscopy
Implementation Method 3
B is a peak area ratio of the antimony to the molybdenum calculated by X-ray photoelectron spectroscopy
Data Source
AI summary
An object of the present invention is to provide a catalyst capable of improving the selectivity of unsaturated aldehydes and unsaturated carboxylic acids, and a catalyst containing molybdenum, antimony, bismuth, and iron, wherein an atom ratio of the antimony to the molybdenum on a surface of the catalyst is greater than an atom ratio of the antimony to the molybdenum in the entire catalyst is provided.