Heteropoly Acid Catalyst Synthesis Oxidation Control
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Solution Overview
Problem
The oxidation state of components like molybdenum and antimony in heteropoly acid catalysts affects their activity and stability during the oxidation of unsaturated aldehydes to unsaturated carboxylic acids, as these states can change during catalyst synthesis and process conditions, leading to reduced performance.
Innovation Solution
A method to control the oxidation state of molybdenum and antimony by maintaining them in their highest oxidation states through careful control of synthesis steps, including digestion time, drying conditions, and calcination processes, using oxidizing agents like hydrogen peroxide and ensuring sufficient air contact to prevent reduction, thereby maximizing catalyst activity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If antimony is used to reduce molybdenum to lower oxidation state during catalyst synthesis, then catalyst formation is achieved, but catalyst activity and stability are reduced
Solution Approach 1:
The patent controls the oxidation state parameter of molybdenum by adjusting synthesis conditions (digestion time, drying conditions, calcination temperature) to maintain molybdenum in its highest oxidation state (Mo6+) while using antimony (Sb3+) for catalyst formation. This parameter control resolves the contradiction by optimizing the oxidation state to balance catalyst formation with high activity and stability.
Solution Approach 2:
The patent employs strong oxidants (hydrogen peroxide, air) during the synthesis process to reoxidize reduced molybdenum species back to Mo6+. This accelerated oxidation prevents the formation of inactive lower oxidation states and maintains catalyst activity and stability while still allowing antimony to participate in catalyst formation.
2Ease of manufacture
If molybdenum is reduced to lower oxidation state during synthesis, then catalyst structure is formed, but conversion efficiency is reduced
Solution Approach 1:
The patent implements continuous oxidation throughout the synthesis process (during digestion, drying, and calcination) to continuously maintain molybdenum in the Mo6+ oxidation state. This continuous action ensures that the catalyst structure forms while the active oxidation state is preserved, maximizing conversion efficiency.
Solution Approach 2:
The patent uses oxidation indicators and monitoring methods to detect the oxidation state of molybdenum during synthesis and adjusts process conditions accordingly. This feedback mechanism ensures that molybdenum remains in the highest oxidation state, optimizing both structure formation and conversion efficiency.
3Ease of manufacture
If synthesis time is extended to complete catalyst formation, then catalyst structure is fully developed, but reduction of molybdenum increases
Solution Approach 1:
The patent applies preliminary oxidation actions during each stage of synthesis (digestion, drying, calcination) before molybdenum reduction can occur. By pre-establishing the Mo6+ state and continuously maintaining it through oxidation, the patent prevents reduction even as synthesis time extends, thus stabilizing the oxidation state while completing catalyst formation.
Solution Approach 2:
The patent introduces oxidizing agents and oxygen-containing atmospheres beforehand during synthesis to cushion against reduction. This protective measure ensures that even as synthesis progresses and reduction tendencies increase, the oxidation state remains stable at Mo6+, preventing composition changes that would reduce 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 ensures higher catalyst activity and stability by maintaining molybdenum in its highest oxidation state, leading to improved conversion of unsaturated aldehydes to unsaturated carboxylic acids, as demonstrated by increased relative activity and selectivity in reactor testing.
Implementation Method 1
using oxidizing agents like hydrogen peroxide and ensuring sufficient air contact to prevent reduction
Implementation Method 2
using oxidizing agents like hydrogen peroxide
Implementation Method 3
ensuring sufficient air contact to prevent reduction
Implementation Method 4
the oxidation of unsaturated aldehydes, such as methacrolein, to unsaturated carboxylic acids, such as methacrylic acid
Data Source
AI summary
The invention is for a method for making a heteropoly acid compound catalyst from compounds containing molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony and boron in which molybdenum, vanadium, phosphorus, cesium, copper, bismuth and boron are at their highest oxidation states and antimony has a 3+ oxidation state. The catalyst contains oxides of molybdenum, vanadium, phosphorus, cesium, copper, bismuth, antimony, boron and, optionally, other metals. The catalyst has the formula:Mo12VaPbCscCudBieSbfBgOx where Mo is molybdenum, V is vanadium, P is phosphorus, Cs is cesium, Cu is copper, Bi is bismuth, Sb is antimony, B is boron, O is oxygen, a is 0.01 to 5.0, b is 0.5 to 3.5, c is 0.01 to 2.0, d is 0.0-1.5, e is 0.0-2.0, f is 0.01-3.0, g is 0.0-4.0 and x satisfies the valences. Molybdenum is reduced by antimony and reoxidized during catalyst synthesis.