Two-Stage Silver Impregnation for Ethylene Oxide Catalyst
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Solution Overview
Problem
Current silver-based ethylene oxide catalysts face challenges in achieving high activity, selectivity, and stability, with existing methods failing to maintain effective performance over time, leading to reduced industrial efficiency and economic viability.
Innovation Solution
A two-stage silver impregnation process is employed, where a sub-catalytic level of silver is initially deposited as isolated atoms or nanoparticles on a carrier, followed by additional silver and promoting species to achieve a catalytically effective level, enhancing the catalyst's performance through improved coverage of active sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-stage impregnation process is used to deposit silver on the carrier, then the manufacturing process is simple, but the catalyst activity and selectivity are insufficient
Solution Approach 1:
The single-stage impregnation process is divided into two distinct stages: (1) deposition of sub-catalytic silver (0.01-1 wt%) to form isolated atoms or nanoparticles, and (2) addition of catalytic silver (at least 10 wt%) and promoting species. This segmentation allows each stage to serve a specific function, resulting in superior catalyst performance compared to conventional single-stage methods.
2Ease of manufacture
If conventional impregnation methods are used, then the manufacturing cost is lower, but the catalyst selectivity and stability are reduced
Solution Approach 1:
The first impregnation stage performs a preliminary action by depositing sub-catalytic silver in sub-monolayer amounts to create isolated atoms or nanoparticles on the carrier surface. This preliminary deposition optimizes the surface coverage and creates a foundation for the second stage, where additional silver and promoters are added to achieve the final catalytically active structure with enhanced selectivity.
3Productivity
If high silver content is deposited in a single stage, then the catalyst activity is achieved, but the silver distribution and coverage are suboptimal
Solution Approach 1:
The two-stage process creates local quality variations in silver distribution: the first stage creates isolated silver atoms or nanoparticles with sub-monolayer coverage, while the second stage adds additional silver to reach catalytic levels. This staged approach ensures optimal local distribution and coverage that cannot be achieved through single-stage uniform deposition.
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 results in a catalyst with improved activity, selectivity, and stability, outperforming conventional single-stage impregnation processes, with increased selectivity and prolonged usability, effectively addressing the limitations of existing catalysts.
Implementation Method 1
subjecting the refractory carrier having a sub-catalytic level of silver ion to conditions under which silver ions become at least partially reduced to elemental silver
Implementation Method 2
silver-based ethylene oxide catalysts for the oxidative conversion of ethylene to ethylene oxide
Implementation Method 3
oxidative conversion of ethylene to ethylene oxide
Data Source
AI summary
A method for producing a catalyst effective in the oxidative conversion of ethylene to ethylene oxide, the method comprising: (i) impregnating a porous refractory carrier with a sub-catalytic level of silver ion in a range of 0.1 wt % to 1 wt % of silver by weight of the carrier and silver, and at least partially reducing said silver ion to elemental silver to produce a low-silver catalyst precursor having isolated silver atoms or silver nanoparticles on surfaces of said refractory carrier; and (ii) further impregnating the low-silver catalyst precursor with a catalytic amount of silver ion of at least 10 wt % total amount of silver and at least one promoting species by weight of the carrier and silver, and subjecting the further impregnated carrier to an elevated temperature of at least 200° C. to completely reduce silver ion to elemental silver in the carrier. The low-silver catalyst precursor produced in step (i) is also described in detail. Methods for using the catalyst produced in step (ii) for the oxidative conversion of ethylene to ethylene oxide are also described.