Catalyst Active Mass Coverage for Acrylic Acid Selectivity
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Solution Overview
Problem
Catalysts used for the partial gas phase oxidation of acrolein to acrylic acid suffer from low selectivity of acrylic acid formation due to overoxidation to COx, with high acrolein conversion often requiring conditions that reduce selectivity, especially at lower temperatures.
Innovation Solution
A catalyst with a shaped carrier body coated with a catalytically active multi-element oxide material containing Mo, V, and optionally Nb and W, with a specific active mass coverage and geometric surface area, optimized to reduce overoxidation and enhance acrylic acid selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher temperatures are used to achieve high acrolein conversion, then conversion efficiency improves, but selectivity of acrylic acid formation deteriorates due to overoxidation to COx
Solution Approach 1:
The patent applies parameter changes by optimizing the active mass coverage (q) to a specific range (0.05-0.25 mg/mm²) and controlling the geometric surface area (Sm) of the support body. These parameter adjustments allow the catalyst to achieve high acrolein conversion while maintaining high acrylic acid selectivity by preventing excessive overoxidation that occurs at higher temperatures with conventional catalysts.
Solution Approach 2:
The patent uses composite materials by combining a specifically designed support body with controlled geometric surface area and porosity characteristics, coated with a catalytically active oxide mass containing Mo, V, and optionally Nb and W in optimized ratios. This composite structure enables simultaneous high conversion and high selectivity by controlling mass transfer and active site distribution.
2Productivity
If active mass coverage is increased to enhance catalytic activity, then conversion improves, but selectivity deteriorates due to increased overoxidation
Solution Approach 1:
The patent applies parameter changes by establishing an optimal active mass coverage range (q = 0.05-0.25 mg/mm²) that balances catalytic activity and selectivity. This parameter optimization ensures sufficient acrolein conversion while preventing excessive overoxidation to COx, resolving the contradiction between conversion and selectivity.
Solution Approach 2:
The patent applies local quality by creating a controlled distribution of active mass on the support body surface with specific geometric characteristics. The optimized active mass coverage ensures appropriate catalytic activity at the surface while the controlled geometric surface area and porosity prevent excessive overoxidation, achieving both high conversion and high selectivity simultaneously.
3Productivity
If geometric surface area is increased to provide more active sites, then conversion improves, but selectivity worsens due to increased overoxidation reactions
Solution Approach 1:
The patent applies parameter changes by optimizing the geometric surface area (Sm) of the support body and controlling the active mass coverage (q) within specific ranges. This parameter optimization ensures that the catalyst provides sufficient active sites for high acrolein conversion while maintaining the selectivity required to prevent excessive overoxidation to COx.
Solution Approach 2:
The patent applies porous materials by using a support body with controlled porosity and specific geometric surface area characteristics. The optimized porous structure provides adequate active sites for high conversion while the controlled pore architecture and surface area prevent excessive overoxidation, simultaneously achieving high productivity and high selectivity.
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 catalyst achieves high acrolein conversion while maintaining high selectivity of acrylic acid formation, even at elevated temperatures, by controlling the active mass coverage and geometric surface area, thereby minimizing overoxidation to COx.
Implementation Method 1
a catalyst for the production of an α,β-unsaturated carboxylic acid by gas-phase oxidation of an α,β-unsaturated aldehyde, comprising a support body with an active mass applied thereto, characterized in that the active mass covering q is at most 0.22 mg/mm2, where Q is the active mass fraction of the catalyst in wt% and Sm is the specific geometric surface area of the support body in mm2/mg
Implementation Method 2
gas-phase oxidation of an α,β-unsaturated aldehyde
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention relates to a catalyst for producing an α,β-unsaturated carboxylic acid by gas phase oxidation of an α,β-unsaturated aldehyde, comprising a moulded body support having an active material applied thereto, characterised in that the active material covering q is a maximum 0.3 mg/mm2, Q being the active material part of the catalyst in wt.-% and Smbeing the specific geometric surface of the moulded body support in mm2/mg. The invention also relates to a method for producing said catalyst and to a method for producing an α,β-unsaturated carboxylic acid by gas phase oxidation of an α,β-unsaturated aldehyde on a fixed bed catalyst which contains the bulk material of the catalyst. Due to said catalyst, the over-oxidation into COx is reduced and the selectivity of the formation of acrylic acid is increased, whilst maintaining a continuous high yield in acroleine.