Ethylene Glycol Process pH Control for Catalyst Protection
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Solution Overview
Problem
The deactivation of hydrolysis catalysts in the production of ethylene glycol due to the formation of inorganic chlorides from the reaction of chloroethanol with catalysts leads to reduced efficiency and the need for frequent catalyst addition and bleed streams.
Innovation Solution
Maintaining the pH in the bottom section of the ethylene oxide stripper between 9.5 and 12.0 by adding a base, which reduces chloroethanol presence and catalyst decomposition, thereby extending catalyst life and reducing the need for additional catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrolysis catalysts are used to promote ethylene oxide hydrolysis to ethylene glycol, then selectivity to monoethylene glycol is improved, but the catalyst becomes deactivated due to reaction with chloroethanol forming inorganic chlorides
Solution Approach 1:
The patent removes chloroethanol from the system before it can react with and deactivate the hydrolysis catalyst. This preliminary removal action prevents the harmful reaction that would otherwise form inorganic chlorides and deactivate the catalyst, thereby maintaining catalyst activity while preserving high selectivity to monoethylene glycol
Solution Approach 2:
The patent converts the harmful effect of chloroethanol (which deactivates the catalyst) into a beneficial situation by removing it beforehand. The presence of chloroethanol is transformed from a catalyst-deactivating hazard into a controlled intermediate that is eliminated prior to the hydrolysis step, protecting the catalyst while maintaining process efficiency
2Reliability
If catalyst bleed stream is employed to remove deactivated catalyst, then catalyst deactivation is managed, but process complexity and operational requirements increase
Solution Approach 1:
The patent extracts and removes chloroethanol from the process stream before it can reach and deactivate the hydrolysis catalyst. This extraction action eliminates the root cause of catalyst deactivation, thereby managing catalyst performance without requiring additional catalyst bleed streams or complex operational procedures
3Productivity
If additional fresh catalyst is added during operation to compensate for deactivation, then catalyst activity is maintained, but manufacturing cost and operational complexity increase
Solution Approach 1:
The patent takes preliminary action to remove chloroethanol before it can deactivate the catalyst, thereby preventing catalyst consumption. This approach maintains catalyst activity throughout operation without requiring the continuous addition of fresh catalyst, reducing both catalyst consumption and associated costs
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
This approach effectively minimizes catalyst deactivation and the formation of inactive chlorides, enhancing the process efficiency and reducing the requirement for frequent catalyst replenishment and bleed streams.
Implementation Method 1
Maintaining the pH in the bottom section of the ethylene oxide stripper between 9.5 and 12.0 by adding a base
Implementation Method 2
the ethylene oxide may be reacted with water in order to provide monoethylene glycol
Implementation Method 3
ethylene oxide is recovered from the reactor product stream by absorption in water in the absorber section
Data Source
AI summary
A process for the production of ethylene glycol comprising:(i) supplying ethylene and oxygen and an organic chloride moderator to an EO reactor, thereby producing a reactor product stream;(ii) supplying the reactor product stream to an EO absorber, thereby producing a fat absorbent stream;(iii) supplying the fat absorbent stream to an EO stripper, thereby producing a concentrated ethylene oxide stream and a lean absorbent stream;(iv) recirculating the lean absorbent stream to the EO absorber; and(v) supplying the ethylene oxide stream and/or the ethylene carbonate stream to hydrolysis reactors with an alkali metal salt hydrolysis catalyst to form an ethylene glycol stream;wherein the process additionally comprises:(vi) removing a glycol bleed stream from the ethylene oxide stripper; and(vii) adding a base to the ethylene oxide stripper such that the pH in the bottom section of the stripper is maintained from 9.5 to 12.0.