Multilobe Catalyst for Ethylene Oxide Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing catalysts for ethylene oxide production face challenges in achieving a balance between high selectivity, mechanical stability, and low pressure drop, as reducing catalyst body size to facilitate ethylene oxide diffusion leads to increased packing density and pressure drop, while maintaining mechanical strength is crucial.
Innovation Solution
A shaped catalyst body with a multilobe structure, featuring a content of at least 20 wt.% silver, a plurality of passageways extending from one face side surface to another, and specific wall thicknesses to ensure high mechanical stability and efficient gas flow, thereby optimizing selectivity and pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst body size is reduced to facilitate ethylene oxide diffusion, then selectivity is improved, but packing density increases and pressure drop increases
Solution Approach 1:
The catalyst body is segmented into multiple lobes with internal passageways, creating a multilobe structure that divides the internal volume into multiple chambers. This segmentation reduces the diffusion path length for ethylene oxide while maintaining an adequate overall catalyst size, thereby improving selectivity without excessively increasing pressure drop.
Solution Approach 2:
The patent introduces internal passageways that extend through the catalyst body in multiple directions, adding dimensional complexity to the catalyst structure. These passageways provide multiple diffusion pathways for ethylene oxide, effectively reducing the average diffusion distance without simply shrinking the external catalyst dimensions, thus balancing selectivity and pressure drop.
2Reliability
If the catalyst body size is reduced to facilitate ethylene oxide diffusion, then selectivity is improved, but mechanical stability deteriorates
Solution Approach 1:
The multilobe structure segments the catalyst body into multiple interconnected chambers separated by walls of controlled thickness. This segmentation creates a framework that maintains mechanical integrity while providing short diffusion paths within each lobe, improving selectivity without sacrificing overall structural strength.
Solution Approach 2:
The patent specifies particular wall thickness ranges for the separators between lobes, creating local variations in structural properties. The walls are thick enough to maintain mechanical stability but thin enough to allow efficient gas flow and heat transfer, optimizing both structural strength and catalytic performance.
3Reliability
If the wall thickness is reduced to increase surface area, then selectivity is improved, but mechanical stability deteriorates
Solution Approach 1:
The patent defines specific wall thickness ranges (0.5-2.0 mm) for the internal separators, creating local optimization where the wall thickness is precisely controlled to balance mechanical strength and surface area. This local quality control ensures adequate structural support while maximizing the active catalytic surface area for high selectivity.
Solution Approach 2:
The catalyst employs a porous refractory support material that provides high surface area within the constrained wall thickness. The porous structure increases the effective catalytic surface area without proportionally increasing wall thickness, maintaining mechanical stability while improving selectivity through enhanced active sites.
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 catalyst body achieves high mechanical stability, efficient gas flow, and enhanced selectivity by strategically arranging passageways and wall thicknesses, balancing surface area and mechanical strength to improve ethylene oxide production efficiency.
Implementation Method 1
silver deposited on a porous refractory support
Implementation Method 2
the diffusion of the more bulky ethylene oxide takes significantly longer... it would appear favorable to provide a shaped catalyst body wherein the pore volume is located predominantly close to the geometric surface of the shaped catalyst body, allowing ethylene oxide to pass out of the pores more quickly
Implementation Method 3
heterogeneous catalysts comprising silver are used... to carry out the heterogeneously catalyzed gas-phase oxidation
Implementation Method 4
gas-phase oxidation of ethylene
Data Source
AI summary
A shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, comprising silver deposited on a porous refractory support, the shaped catalyst body having a first face side surface, a second face side surface and a circumferential surface, characterized by a content of at least 20 wt.-% of silver, relative to the total weight of the shaped catalyst body; a multilobe structure; a plurality of passageways extending from the first face side surface to the second face side surface, outer passageways being arranged around a central passageway with one outer passageway being assigned to each lobe, wherein neighboring outer passageways are arranged essentially equidistantly to each other and the outer passageways are arranged essentially equidistantly to the central passageway; a minimum wall thickness A between two neighboring passageways in the range of 0.6 to 1.3 mm; a minimum wall thickness B between each outer passageway and the circumferential surface in the range of 1.1 to 1.8 mm; and a BET surface area in the range of 1.6 to 3.0 m2/g. The shaped catalyst bodies allow for a favorable balance between mechanical stability, pressure drop and selectivity. The invention also relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of a shaped catalyst body as defined above. The invention further relates to a process for preparing a shaped catalyst body as above, comprising i) impregnating a refractory support having a BET surface area in the range of 1.4 to 2.5 m2/g with a silver impregnation solution; and ii) subjecting the impregnated refractory support to a calcination process; wherein steps i) and ii) are optionally repeated.