High-Concentration Silver Impregnation Solution for Ethylene Oxide Catalysts
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Solution Overview
Problem
Conventional silver impregnating solutions for ethylene oxide catalysts are limited to a maximum silver concentration of 31 wt%, leading to challenges in achieving high silver loading without compromising catalyst productivity and stability.
Innovation Solution
A high silver impregnating solution is developed, containing silver ions, a silver concentration enhancer such as an ammonium salt or amino acid, an organic amine, and water, allowing for a silver concentration of at least 33 wt% without precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional silver impregnating solutions are used, then the silver concentration is limited to 31 wt%, but achieving high silver loading becomes difficult without compromising catalyst productivity
Solution Approach 1:
The patent changes the chemical parameters of the impregnating solution by introducing ammonium salts (ammonium carbonate, ammonium bicarbonate, ammonium formate) and amino acids (glycine, alanine) as new solubilizing agents. These additives alter the solution chemistry to increase silver solubility from 31 wt% to 33 wt% or higher, enabling high silver loading while maintaining catalyst productivity through a single impregnation process
Solution Approach 2:
The patent creates a composite impregnating solution system combining silver ions with multiple solubilizing agents (ammonium salts and/or amino acids) in an aqueous medium. This composite approach allows the solution to maintain high silver concentration without precipitation, resolving the contradiction between high silver loading and catalyst productivity
2Quantity of substance
If high water absorption carrier is used to increase silver loading, then silver loading increases, but mechanical strength of the catalyst is lost
Solution Approach 1:
The patent changes the impregnation method by using a high silver concentration solution (33 wt% or higher) that can be applied with controlled water absorption. This allows achieving high silver loading without requiring excessive water absorption carriers, thereby preserving the mechanical strength of the catalyst support
3Quantity of substance
If double impregnation process is used to increase silver loading, then silver loading increases, but process complexity and loss of productivity occur
Solution Approach 1:
The patent merges multiple functions into a single impregnation step by using an aqueous solution containing silver ions at 33 wt% or higher concentration stabilized with ammonium salts and/or amino acids. This single-step process achieves high silver loading without the complexity of double impregnation, maintaining catalyst productivity while simplifying the manufacturing process
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 high silver impregnating solution enables the production of silver-based ethylene oxide catalysts with improved activity, selectivity, and stability, overcoming the limitations of conventional methods.
Implementation Method 1
a silver concentration enhancer selected from at least one ammonium salt having an anionic component that is thermally decomposable, or at least one amino acid
Implementation Method 2
allowing for a silver concentration of at least 33 wt% without precipitation
Implementation Method 3
at least one organic amine; wherein components (i)-(iii) are dissolved in the impregnating solution
Implementation Method 4
the impregnated carrier is then calcined to convert silver ions to metallic silver
Data Source
AI summary
A silver impregnation solution comprising: (i) silver ions, (ii) a silver concentration enhancer selected from at least one ammonium salt having an anionic component that is thermally decomposable; or at least one amino acid, or a combination thereof, (iii) at least one organic amine; and (iv) water; wherein said components (i)-(iii) are dissolved in said impregnation solution, and oxalic acid may or may not be included. The silver impregnation solution can achieve significantly higher silver concentrations, including at least or above 33, 34, or 35 wt%. Methods for producing a silver catalyst by silver impregnation of a refractory support followed by calcination are also described. The resulting silver catalysts possess high silver loadings of typically at least 17, 18, or 19 wt%.