Hydrogenation Catalyst for Olefin Polymerization Effluent
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Solution Overview
Problem
In olefin polymerization processes, high hydrogen levels in effluent and recycle streams can hinder the production of desired polymers, leading to costly monomer loss and the generation of off-specification products, particularly when transitioning between different molecular weight production requirements.
Innovation Solution
The process involves using a hydrogenation catalyst, such as titanocene with an aluminum alkyl compound, to reduce hydrogen levels in effluent streams before recycling them to polymerization reactors, thereby avoiding the need for venting and minimizing monomer loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen is added to regulate polymer molecular weight in polymerization reactors, then the desired molecular weight control is achieved, but hydrogen accumulation in effluent and recycle streams occurs which hinders production of polymers with different molecular weights
Solution Approach 1:
The patent extracts hydrogen from the effluent stream using a hydrogen-selective membrane. The membrane selectively removes hydrogen from the polymerization effluent, allowing the treated effluent to be recycled back to the reactor. This enables molecular weight control through hydrogen addition while preventing hydrogen accumulation that would hinder product transitions.
Solution Approach 2:
The patent changes the hydrogen concentration parameter in the recycle stream by using a hydrogen-selective membrane to selectively remove hydrogen. This allows dynamic adjustment of hydrogen levels in the recycled effluent, enabling rapid transitions between different polymer molecular weight products while maintaining precise molecular weight control during production.
2Quantity of substance
If purge streams are used to remove excess hydrogen from recycle streams, then hydrogen levels are reduced, but significant monomer loss occurs
Solution Approach 1:
Instead of purging the entire effluent stream, the patent uses a hydrogen-selective membrane to extract only the hydrogen component from the recycle stream. This selective extraction removes excess hydrogen while retaining and recycling the monomer and other components, dramatically reducing monomer loss compared to conventional purge methods.
Solution Approach 2:
The hydrogen-selective membrane acts as an intermediary that selectively transfers hydrogen from the effluent stream to a separate permeate side. This allows hydrogen removal without requiring physical purging of the main stream, enabling hydrogen level control while preserving monomer for recycling.
3Quantity of substance
If conventional venting methods are used to reduce hydrogen levels, then hydrogen is removed from the system, but transition times are extended and off-specification polymer is generated
Solution Approach 1:
The patent continuously extracts hydrogen from the recycle stream using a membrane, rather than relying on slow venting during transitions. This continuous selective removal enables rapid adjustment of hydrogen levels when transitioning between products, minimizing the time that off-specification polymer is produced.
Solution Approach 2:
The membrane-based hydrogen removal operates continuously rather than intermittently like conventional venting. This continuous action maintains optimal hydrogen levels throughout the process, preventing the extended transition periods and off-specification polymer generation associated with batch venting methods.
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 rapid reduction of hydrogen levels, enabling the production of polymers with desired molecular weights while reducing monomer loss and avoiding the production of off-specification products.
Implementation Method 1
contacting the first effluent with a hydrogenation catalyst under conditions effective to hydrogenate unreacted monomer and produce a second effluent
Data Source
AI summary
A process for reducing the level of hydrogen in certain polymerization effluent and recycle streams containing unreacted propylene monomers and hydrogen by contacting the streams with a hydrogenation catalyst so as to convert at least part of the propylene to the corresponding alkane. The process is particularly applicable to the effluent from a slurry polymerization reactor which has been used to produce a polypropylene homopolymer or copolymer having a first molecular weight and at least part of the effluent is to be supplied to a slurry polymerization reactor to produce a polypropylene homopolymer or copolymer having a second, higher molecular weight.