Pd-Au Shell Catalyst Concentration Profile for Vinyl Acetate
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Solution Overview
Problem
Existing Pd- and Au-containing shell catalysts have an undesirable distribution of catalytically active species, with maxima of concentration either extending deeply into the catalyst support or being too homogeneous, leading to suboptimal catalytic performance.
Innovation Solution
A Pd- and Au-containing shell catalyst with a concentration profile where the maxima of palladium and gold concentrations are within 0 to 40 micrometers from the catalyst surface, and the distance between these maxima is between 0 to 10 micrometers, achieved through specific processes involving recirculating motion of catalyst supports and controlled application of precursor compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spray impregnation methods are used to apply catalytically active species to catalyst supports, then a shell-like distribution is achieved, but the concentration maxima extend too deeply into the support or are too homogeneous, reducing catalytic effectiveness
Solution Approach 1:
The patent applies local quality by creating a non-uniform concentration distribution of Pd and Au species within the catalyst shell. The concentration maxima are positioned at specific depths (0-40 μm from surface) with controlled spacing (0-10 μm between maxima), rather than uniform distribution. This localized concentration optimization enhances catalytic effectiveness by positioning active species where they most effectively interact with reactants.
Solution Approach 2:
The patent employs parameter changes by controlling the spray impregnation process parameters including temperature (5-30°C below activation temperature), spray solution concentration, and multiple sequential application steps. These parameter adjustments enable precise control over the depth and distribution of catalytically active species, achieving the desired concentration profile with maxima at controlled depths.
2Ease of manufacture
If the catalytically active species are distributed uniformly over the entire catalyst support, then ease of manufacture is improved, but catalytic activity decreases due to suboptimal species distribution
Solution Approach 1:
The patent applies preliminary action by performing multiple sequential spray impregnation steps with controlled drying and activation between steps. This staged approach allows precise control over species distribution before final activation, achieving optimal concentration profiles while maintaining practical manufacturability through standardized process steps.
3Length of stationary object
If the concentration maxima of Pd and Au are positioned deeply within the catalyst support, then the shell thickness is increased, but the catalytic effectiveness is reduced due to excessive depth
Solution Approach 1:
The patent replaces mechanical control methods with controlled chemical deposition through spray impregnation. By controlling the spray solution properties, temperature, and sequential application, the concentration maxima are positioned at optimal depths (0-40 μm) without requiring mechanical drilling or physical placement, achieving precise depth control through chemical process parameters.
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 improved distribution of Pd and Au in the shell catalyst results in enhanced catalytic performance, specifically in the production of vinyl acetate monomer, with higher activity, selectivity, and productivity compared to traditional catalysts.
Implementation Method 1
subjecting a bed of a catalyst support to a recirculating motion, wherein the bed is heated to a temperature of 60° C. to 120° C.
Implementation Method 2
sequential or simultaneous application of a dissolved Pd-containing precursor compound and a dissolved Au-containing precursor compound by spray application onto the bed of the catalyst support
Data Source
AI summary
The present invention relates to a Pd- and Au-containing shell catalyst which is characterised by an improved Pd and Au distribution. The invention also relates to two methods for producing said catalyst and to a method for producing vinyl acetate monomer using said catalyst.