Alkylene Glycol Start-Up Stream Injection
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Solution Overview
Problem
The existing process for producing alkylene glycol from alkenes faces challenges during start-up, particularly when little or no aqueous ethylene oxide is produced, leading to uneven catalyst distribution and increased complexity in the ethylene oxide to ethylene glycol section of the plant.
Innovation Solution
A process that involves converting alkenes to alkylene oxides using an epoxidation catalyst, followed by absorption, stripping, carboxylation, hydrolysis, and dehydration, with a specific start-up procedure that includes supplying water, carboxylation-hydrolysis catalyst, and carbon dioxide streams to the carboxylation reactor and providing a start-up stream of alkylene glycol at a designated injection point to maintain catalyst concentration and facilitate a homogeneous distribution throughout the plant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If water, carboxylation-hydrolysis catalyst and carbon dioxide streams are supplied to the carboxylation reactor during start-up without aqueous alkylene oxide stream, then the plant can be prepared for operation, but a homogenous distribution of catalyst solution throughout the entire ethylene oxide to ethylene glycol section results instead of desired concentrated solution in catalyst separation section
Solution Approach 1:
The patent applies preliminary action by introducing a start-up stream comprising alkylene glycol at a specific injection point before normal operation begins. This preliminary introduction of alkylene glycol establishes the proper catalyst concentration distribution pattern in advance, preventing the formation of homogenous catalyst distribution that would occur if only water and catalyst streams were supplied during start-up.
Solution Approach 2:
The patent uses alkylene glycol as an intermediary substance during the start-up phase. Instead of directly supplying water and catalyst streams that would create homogenous distribution, the alkylene glycol start-up stream acts as a mediator to establish the desired concentration gradient, with catalyst being concentrated in the separation section while maintaining proper hydraulic conditions throughout the plant.
2Stability of the object's composition
If sections of the plant are bypassed until aqueous ethylene oxide stream is provided, then catalyst distribution can be controlled, but the overall start-up process complexity increases
Solution Approach 1:
The patent eliminates the need for bypassing sections by taking preliminary action - introducing the alkylene glycol start-up stream at the appropriate injection point before normal operation. This preliminary action establishes proper catalyst concentration distribution from the beginning, allowing all plant sections to be operated in sequence without requiring bypasses or separate start-up procedures for different sections.
Solution Approach 2:
The patent extracts the problematic start-up phase from the overall process by introducing a dedicated start-up stream comprising alkylene glycol. This separate start-up stream handles the specific requirements of establishing catalyst distribution without requiring complex bypass arrangements or separate start-up procedures for catalyst separation section and other plant sections.
3Stability of the object's composition
If alkylene glycol start-up stream is provided at the inlet of carboxylation reactor, then catalyst concentration and hydraulic conditions are maintained, but additional equipment for start-up stream supply is required
Solution Approach 1:
The patent applies universality by using the alkylene glycol start-up stream to simultaneously achieve multiple functions: establishing proper catalyst concentration distribution, maintaining hydraulic conditions throughout the plant, and preparing the system for normal operation. This single start-up stream performs what would otherwise require multiple separate systems including bypass arrangements and separate start-up procedures for different plant sections.
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 allows for a simplified and efficient start-up process, maintaining desired catalyst concentrations and hydraulic conditions, eliminating the need to bypass sections and ensuring stable operation, even during initial phases or when the alkylene oxide section is restarted.
Implementation Method 1
converting the alkene in the presence of oxygen and an epoxidation catalyst to the corresponding alkylene oxide
Implementation Method 2
absorbing the alkylene oxide in an aqueous absorbent
Implementation Method 3
stripping the absorbent to provide an aqueous alkylene oxide stream
Implementation Method 4
converting the aqueous alkylene oxide stream in the presence of one or more carboxylation-hydrolysis catalysts and carbon dioxide to a stream comprising the corresponding alkylene carbonate
Implementation Method 5
converting the stream comprising the alkylene carbonate to a stream comprising the alkylene glycol
Implementation Method 6
removing water from the stream comprising the alkylene glycol to form a dehydrated alkylene glycol stream
Implementation Method 7
purifying the dehydrated alkylene glycol stream in one or more glycol distillation columns
Data Source
AI summary
The invention provides a process for the production of an alkylene glycol from an alkene comprising the steps of : i) converting the alkene to the corresponding alkylene oxide; ii) absorbing the alkylene oxide in an aqueous absorbent; iii) supplying the aqueous alkylene oxide at an inlet to a carboxylation reactor; iv) converting the aqueous alkylene oxide to the corresponding alkylene carbonate; v) converting the alkylene carbonate to the alkylene glycol; vi) removing water from the alkylene glycol to form a dehydrated alkylene glycol; vii) purifying the dehydrated alkylene glycol, wherein the start-up procedure comprises supplying water, carboxylation-hydrolysis catalyst and carbon dioxide streams to the carboxylation reactor and providing a start-up stream comprising the alkylene glycol at an injection point at or downstream of the inlet used in step iii) and recovering an alkylene glycol stream from the glycol distillation column.