Vinyl Acetate Catalyst Impregnation to Prevent Gold Aggregation
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Solution Overview
Problem
Existing catalyst production methods for vinyl acetate face challenges in achieving high selectivity and suppressing gold particle aggregation, which affects the efficiency of vinyl acetate production.
Innovation Solution
A method involving the impregnation of a carrier with an alkali solution followed by contact impregnation with copper, palladium, and gold compounds in excess amounts, separation when desired amounts are reached, and a reduction treatment to form a catalyst with a controlled alloy state of palladium and gold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If palladium and gold compounds are impregnated on a carrier in the same step with an alkali component, then the carrier is easily impregnated with both metals, but gold atoms may not be close to palladium and gold particles may aggregate due to different hydrolysis rates
Solution Approach 1:
The impregnation process is divided into two sequential steps: first impregnating the carrier with the alkali component, then separately impregnating with the metal compounds. This segmentation allows controlled hydrolysis of each compound, ensuring uniform distribution and close proximity of gold atoms to palladium atoms, while preventing aggregation.
Solution Approach 2:
The carrier is pre-impregnated with the alkali component before introducing the metal compounds. This preliminary action creates a controlled environment that facilitates uniform hydrolysis and distribution of the metal atoms, ensuring that gold atoms are positioned close to palladium atoms rather than aggregating separately.
2Manufacturing precision
If copper-containing compound is added during hydrolysis of gold-containing compound, then gold hydrolysis rate increases and gold atoms are close to palladium, but gold particle aggregation still occurs
Solution Approach 1:
The copper-containing compound is extracted from the hydrolysis mixture and removed. This eliminates the harmful effect of copper-induced gold particle aggregation while preserving the beneficial effect of enhanced gold hydrolysis rate and uniform distribution achieved through the controlled two-step impregnation process.
Solution Approach 2:
The potential harmful aggregation effect of copper is converted into a benefit by using copper-containing compound only as a temporary promoter during the impregnation process, then removing it. The copper temporarily enhances gold hydrolysis and distribution, then is eliminated to prevent aggregation, transforming a potential harm into a controlled beneficial effect.
3Manufacturing precision
If gold-containing compound is slowly hydrolyzed, then gold atoms are supported at low rate, but this causes gold particles to coarsen and aggregate in the solution
Solution Approach 1:
The carrier is pre-impregnated with the alkali component to create a controlled hydrolysis environment before introducing the gold-containing compound. This preliminary action ensures that gold atoms hydrolyze and deposit uniformly on the carrier surface at an appropriate rate, preventing particle coarsening and aggregation while maintaining precise control over the supported amount.
Solution Approach 2:
The alkali component acts as an intermediary that mediates the hydrolysis of the gold-containing compound. It controls the hydrolysis rate to be neither too fast nor too slow, facilitating uniform gold atom deposition on the carrier while preventing aggregation and coarsening of gold particles in the solution.
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
This method significantly improves the selectivity of vinyl acetate production while maintaining high catalytic activity by preventing gold particle aggregation and ensuring close proximity to palladium.
Implementation Method 1
impregnating the carrier with an alkali solution
Implementation Method 2
each compound is hydrolyzed, whereby a palladium hydroxide, a gold hydroxide, and a copper hydroxide are supported on the carrier
Implementation Method 3
a reduction treatment is performed
Data Source
AI summary
A method for manufacturing a catalyst for manufacture of vinyl acetate, the catalyst containing a carrier, copper, palladium, gold, and an acetate, wherein the method comprises, in the following order: step 1) a step for impregnating the carrier with an alkaline solution; step 2) a step for contact-impregnating the carrier with a solution that contains a copper-containing compound, a palladium-containing compound, and a gold-containing compound, the amount of the solution exceeding a desired amount of carried catalyst components; step 3) a step for separating the carrier from the solution once the desired amount of carried catalyst components is carried by the carrier; step 4) a step for performing reduction treatment; and step 5) a step for causing the carrier to carry the acetate.