Annular Multimetal Oxide Catalyst for Propene Oxidation
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Solution Overview
Problem
In heterogeneously catalyzed gas phase partial oxidations, high propene hourly space velocities lead to high hotspot temperatures in catalyst beds, accelerating catalyst aging and reducing selectivity of target product formation, necessitating the use of diluted catalysts that limit hourly space velocity.
Innovation Solution
Employing annular unsupported catalysts with a multimetal oxide composition of specific stoichiometric ratios, particularly Co/Fe and Co/Mo ratios, to maintain high propene conversion and selectivity of acrolein formation at reduced hotspot temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high propene hourly space velocity is used, then productivity is improved, but hotspot temperature increases causing catalyst aging and reduced selectivity
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating multiple metal oxides (molybdenum, tungsten, cobalt, iron, bismuth, silicon, potassium) in specific molar ratios. This compositional parameter change enables the catalyst to maintain high activity and selectivity at lower hotspot temperatures, thus allowing higher space velocities without the penalty of excessive temperature rise and catalyst deactivation
Solution Approach 2:
The patent uses a composite catalyst system consisting of multiple metal oxides working synergistically. The multimetal oxide composition (Mo-W-Co-Fe-Bi-Si-K) creates a composite material that combines the benefits of each component: Mo and W provide structural stability, Co and Fe enhance catalytic activity, Bi improves selectivity, and Si-K provide structural support. This composite structure enables the catalyst to withstand higher space velocities by distributing heat more effectively and maintaining stability at reduced hotspot temperatures
2Quantity of substance
If high hotspot temperature is used to maintain conversion, then propene conversion is improved, but catalyst aging accelerates and selectivity decreases
Solution Approach 1:
The patent optimizes the molar ratios of metal oxides in the catalyst composition, specifically setting Co/Fe from 2 to 4 and Co/Mo from 0.3 to 0.6. These parameter changes in catalyst composition create active sites that are more efficient at lower temperatures, maintaining high propene conversion (≥90 mol%) while reducing the need for high hotspot temperatures that would accelerate catalyst aging
Solution Approach 2:
The patent converts the potential harm of high space velocities (which cause temperature spikes) into a benefit by designing a catalyst that actively manages heat. The multimetal oxide composition creates a catalyst bed that distributes heat more uniformly, transforming the harmful localized hotspots into beneficial moderate temperature zones that maintain conversion while protecting catalyst longevity
3Manufacturing precision
If diluted catalyst is used to reduce hotspot temperature, then selectivity is improved, but hourly space velocity is limited
Solution Approach 1:
Instead of diluting the catalyst with inert material, the patent changes the compositional parameters by incorporating multiple metal oxides in optimized ratios. This approach maintains high catalyst density (undiluted) while the synergistic effect of Mo-W-Co-Fe-Bi-Si-K oxides ensures high selectivity (≥80 mol% acrolein) through controlled reaction pathways that prevent over-oxidation, even at high space velocities
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
Achieves propene conversion of ≥90 mol% and acrolein selectivity of ≥80 mol% at elevated temperatures with reduced hotspot temperatures, enhancing catalyst longevity and product selectivity.
Implementation Method 1
preparing acrolein by heterogeneously catalyzed partial gas phase oxidation
Implementation Method 2
the reaction gas mixture, as it flows through the fixed catalyst bed, passes through a maximum value (known as the hotspot value). This maximum value is composed of the external heating of the fixed catalyst bed and the heat of reaction
Data Source
AI summary
An annular unsupported catalyst for the heterogeneously catalyzed partial gas phase oxidation of propene to acrolein at a propene hourly space velocity on the fixed catalyst bed of ≧120 1 (STP)/1·h and a total CO2 and saturated hydrocarbon content of the starting reaction gas mixture of below 15 mol %, the catalysts of the fixed catalyst bed are the annular unsupported catalysts whose active composition is a multimetal oxide in which the molar Co/Fe ratio=from 2 to 4 and the molar Co/Mo ratio=from 0.3 to 0.7.