Dual Guard Bed Iodide Removal for Ethylene Oxide Catalyst Protection

Solution Overview

Problem

The silver-based epoxidation catalysts used in ethylene oxide production are susceptible to poisoning by gaseous iodide-containing impurities like alkyl iodides and vinyl iodide, leading to reduced selectivity and activity, and shortened catalyst lifespan, necessitating the development of effective guard bed systems to remove these impurities from recycle gas streams.

Innovation Solution

A process involving two guard bed systems, one with silver deposited on a support material and another with palladium and gold, is used to treat recycle gas streams, reducing alkyl iodide and vinyl iodide impurities to low levels, thereby protecting the epoxidation catalyst from poisoning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single guard bed material is used to remove iodide impurities, then the device complexity is reduced, but the removal effectiveness for both alkyl iodide and vinyl iodide impurities is insufficient

Engineering Contradiction:

Improveguard bed system structureVSAvoidimpurity removal effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The guard bed system is divided into two separate beds: a first guard bed containing silver-based material for removing alkyl iodide impurities, and a second guard bed containing palladium-based material for removing vinyl iodide impurities. This segmentation allows each bed to specialize in removing specific impurity types, achieving comprehensive impurity removal while maintaining manageable system complexity through modular design.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If the recycle gas stream is not treated, then the device complexity and operating costs are reduced, but the epoxidation catalyst suffers from poisoning by iodide impurities, leading to reduced selectivity and activity

Engineering Contradiction:

Improvegas treatment systemVSAvoidcatalyst performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The guard bed systems are positioned upstream in the recycle gas loop to preliminarily remove iodide impurities before the gas enters the epoxidation reactor. This preliminary action protects the catalyst from exposure to harmful impurities, maintaining catalyst selectivity and activity throughout operation without requiring complex downstream treatment or frequent catalyst replacement.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If guard bed systems are implemented to remove iodide impurities, then the catalyst performance is maintained, but the device complexity and capital investment increase

Engineering Contradiction:

Improvecatalyst selectivity and activityVSAvoidguard bed system configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The guard bed materials utilize porous structures with high surface area to volume ratios, enabling efficient impurity removal through adsorption and catalytic conversion. The porous nature of these materials provides numerous active sites for reacting with iodide impurities, achieving effective catalyst protection with relatively compact bed volumes and manageable system complexity.

Inventive Principle:

Principle #31Porous materials

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 process effectively reduces the concentration of alkyl iodide and vinyl iodide impurities in the recycle gas stream, maintaining the performance and longevity of the epoxidation catalyst, ensuring high selectivity and activity.

Implementation Method 1

contacting at least a portion of a recycle gas stream comprising an alkyl iodide impurity and a vinyl iodide impurity with a first guard bed material to yield a partially treated recycle gas stream, wherein the first guard bed material comprises a first support material, and deposited on the first support material, silver in an amount of from 2% to 10% by weight

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

contacting at least a portion of a recycle gas stream comprising an alkyl iodide impurity and a vinyl iodide impurity with a first guard bed material to yield a partially treated recycle gas stream, wherein the first guard bed material comprises a first support material, and deposited on the first support material, silver in an amount of from 2% to 10% by weight

Methodology Applied

Scientific EffectCatalytic decomposition: Catalysis

Implementation Method 3

contacting at least a portion of the partially treated recycle gas stream with a second guard bed material to yield a treated recycle gas stream, wherein the second guard bed material comprises a second support material, palladium and gold

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 4

contacting at least a portion of the partially treated recycle gas stream with a second guard bed material to yield a treated recycle gas stream, wherein the second guard bed material comprises a second support material, palladium and gold

Methodology Applied

Scientific EffectCatalytic decomposition: Catalysis

Data Source

PatentUS10526300B2Processes and systems for removing iodide impurities from a recycle gas stream in the production of ethylene oxide

Publication Date: 2020.01.07 SHELL USA INC

AI summary

Processes for reducing the amount of a gaseous iodide-containing impurity present in a recycle gas stream used in the production of ethylene oxide, in particular alkyl iodide and vinyl iodide impurities, are provided. Processes for producing ethylene oxide, ethylene carbonate and/or ethylene glycol, and associated reaction systems are similarly provided.