Silver Impregnation Solution Preparation Without Powder Contact
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Solution Overview
Problem
Existing methods for preparing silver impregnation solutions for oxidative conversion of ethylene to ethylene oxide are inefficient and pose occupational and environmental hazards due to direct contact between oxalic acid and silver oxide powders, leading to potential explosions and safety risks.
Innovation Solution
A method involving separate reactors for neutralization and complexation steps, where oxalic acid and silver oxide are added metered through different conduits to prevent direct contact, with controlled temperature and agitation to ensure safe and efficient production of the silver impregnation solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If oxalic acid and silver oxide powders are handled separately and mixed in a single reactor, then the process is simple and compact, but explosive reactions may occur due to direct contact between the powders
Solution Approach 1:
The patent divides the single reactor into two separate reactors: a first reactor for preparing the aqueous oxalic acid-organic amine solution and a second reactor for adding silver oxide. This segmentation prevents direct contact between oxalic acid and silver oxide powders, eliminating the explosive reaction risk while maintaining process efficiency.
Solution Approach 2:
The patent introduces an aqueous organic amine solution as an intermediary medium. Oxalic acid is first dissolved in this intermediary solution, and only then is silver oxide added. The intermediary solution acts as a barrier that prevents direct contact between the two powders, safely enabling their combination.
2Productivity
If silver oxide is added to aqueous oxalic acid-organic amine solution in a single reactor, then the process is efficient and compact, but safety hazards arise from handling hygroscopic powders
Solution Approach 1:
The patent segments the process into two separate reactors: the first reactor handles the aqueous oxalic acid-organic amine solution preparation, while the second reactor handles the silver oxide addition. This segmentation isolates the safety risks associated with handling hygroscopic silver oxide powder from the solution preparation process, maintaining both productivity and reliability.
3Speed
If oxalic acid and silver oxide are mixed directly, then the silver complex formation is rapid, but explosive reactions occur upon contact
Solution Approach 1:
The patent uses an aqueous organic amine solution as an intermediary that enables rapid silver complex formation without direct powder contact. The oxalic acid is dissolved in this intermediary, and silver oxide is added to the solution, allowing the silver complex to form quickly while the intermediary prevents the explosive reaction between the powders.
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 method ensures safe and efficient production of silver impregnation solutions by preventing direct contact between oxalic acid and silver oxide, minimizing hazards and optimizing reactor use, thereby enhancing operational safety and efficiency.
Implementation Method 1
oxalic acid provides oxalate anion to counter the charge balance of silver cation in the ethylenediamine/water solution to form a soluble [Ag2C2O4]— ethylenediamine complex
Implementation Method 2
The silver oxalate intermediate is then dissolved in an aqueous solution of an organic amine which converts the silver oxalate into water soluble complexes
Data Source
AI summary
A method for preparing a silver impregnation solution comprises (a) charging a neutralization reactor R1 with an aqueous organic amine; (b) adding oxalic acid powder through a first feeding conduit to the neutralization reactor R1 to obtain an aqueous oxalic acid-organic amine solution; (c) directing the aqueous oxalic acid-organic amine solution from the neutralization reactor to a complexation reactor R2; (d) adding particulate silver oxide through a second feeding conduit to the complexation reactor R2 to obtain a silver impregnation solution; and, optionally, (e) subjecting the silver impregnation solution to filtration. The silver impregnation solution is used for producing a catalyst effective in the oxidative conversion of ethylene to ethylene oxide. The method allows for the preparation of a silver impregnation solution in an efficient and occupationally and environmentally safe way. Security hazards which can occur when oxalic acid and silver oxide are added to an aqueous amine solution using the same powder feeding equipment or the same reactor are avoided.