Para-xylene Separation via Zeolite Adsorption and C9 Removal
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Solution Overview
Problem
Current processes for separating para-xylene from mixtures of C8 and C9 aromatic hydrocarbons using para-diethylbenzene as a desorbent face challenges due to the close boiling points of C9 aromatics, leading to their accumulation in the desorbent and requiring stringent feedstock limitations to maintain efficiency.
Innovation Solution
A process involving zeolites as adsorbents and para-diethylbenzene as a desorbent, where the C9 aromatic is separated from para-diethylbenzene via distillation, allowing for the efficient separation of para-xylene from a feed stream containing both C8 and C9 aromatic hydrocarbons, with the C9 aromatic being recycled and separated from the desorbent in subsequent distillation steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If para-diethylbenzene is used as a desorbent for separating para-xylene from C8 and C9 aromatic hydrocarbons, then the separation efficiency of para-xylene is improved, but C9 aromatics accumulate in the desorbent due to close boiling points
Solution Approach 1:
The patent extracts and removes C9 aromatics from the desorbent stream through a dedicated removal unit positioned between the adsorptive separation zone and the distillation zone. This extraction process prevents C9 aromatic accumulation in the recycled desorbent while maintaining the effectiveness of para-diethylbenzene for para-xylene separation.
Solution Approach 2:
The patent introduces an intermediary process unit (C9 aromatic removal unit) that mediates between the adsorptive separation zone and the distillation zone. This intermediary removes the harmful C9 aromatics from the desorbent stream, allowing the desorbent to be efficiently recycled without contamination buildup.
2Manufacturing precision
If C9 aromatics are limited in the feed stream to below 0.1%, then para-xylene separation efficiency is maintained, but the process becomes less economically viable due to stringent feedstock requirements
Solution Approach 1:
The patent converts the previously harmful effect of C9 aromatics (which caused accumulation and process inefficiency) into a manageable component by implementing a dedicated removal unit. This allows the process to handle feedstocks with higher C9 aromatic content (up to 10% or more) while maintaining separation efficiency, thereby improving feedstock flexibility and economic viability.
Solution Approach 2:
The patent changes the operational parameters of the separation process by introducing a C9 aromatic removal step, which enables the system to accommodate wider ranges of feedstock composition. This parameter change allows feedstocks with C9 aromatic content up to 10% or higher to be processed effectively, compared to the previous limitation of below 0.1%.
3Quantity of substance
If higher boiling desorbents are used to separate para-xylene from C8 and C9 aromatics, then C9 aromatics can be separated by fractionation, but the process complexity increases
Solution Approach 1:
The patent uses an intermediary removal unit that specifically targets C9 aromatics in the desorbent stream. This intermediary process simplifies the overall system by preventing C9 aromatic accumulation earlier in the process, thereby reducing the burden on subsequent fractionation steps and lowering overall process complexity compared to using higher boiling desorbents.
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 process enables the effective separation and recovery of para-xylene with reduced C9 aromatic accumulation in the desorbent, allowing for higher C9 aromatic concentrations in the feed stream, thereby improving process efficiency and economic viability.
Implementation Method 1
contacting an adsorbent comprising a zeolite with the feed stream and a first desorbent stream in an adsorptive separation zone to produce an extract stream and a raffinate stream
Implementation Method 2
passing at least a portion of at least one of the second desorbent stream and the third desorbent stream to a desorbent distillation zone to produce a fourth desorbent stream comprising para-diethylbenzene, and a C9 aromatic product stream comprising the C9 aromatic
Data Source
AI summary
The invention is an adsorptive separation process for producing a para-xylene product from a feed stream comprising para-xylene, at least one other C8 aromatic, and a C9 aromatic. An adsorbent comprising X or Y zeolite and a desorbent comprising para-diethylbenzene (p-DEB) are used in an adsorptive separation zone to produce an extract stream comprising para-xylene, p-DEB, and the C9 aromatic and a raffinate stream comprising the at least one other C8 aromatic, the C9 aromatic, and p-DEB. The extract stream is separated in an extract distillation zone to produce a second desorbent stream comprising the C9 aromatic and p-DEB and the raffinate stream is separated in a raffinate distillation zone to produce a third desorbent stream comprising the C9 aromatic and p-DEB. At least a portion of at least one of the second desorbent stream and the third desorbent stream is further separated in a desorbent distillation zone to produce a stream comprising the C9 aromatic.