Aromatic Extraction Before Reforming to Limit Catalyst Deactivation
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Solution Overview
Problem
Catalytic reforming catalysts supported on zeolite in the production of aromatic compounds, such as benzene and toluene, are prone to deactivation due to the formation of carbon-based deposits (coke), which blocks active sites and reduces catalyst efficiency.
Innovation Solution
A process involving a specific sequence of stages including fractionation, aromatic extraction, and catalytic reforming with strategically positioned units and catalysts, such as those with platinum and zeolite, to minimize the initial aromatic content and reduce coke formation, including recycling of aromatic streams and controlled operating conditions like temperature and hydrogen ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic reforming is performed to maximize aromatic production, then the yield of benzene and toluene increases, but the catalyst deactivates rapidly due to coke formation
Solution Approach 1:
The process applies preliminary action by performing extraction of aromatic compounds from the naphtha feedstock before the catalytic reforming step. This pre-extraction removes compounds that would otherwise form coke during reforming, thereby protecting the catalyst from rapid deactivation while still allowing high aromatic yields to be achieved in the subsequent reforming and extraction stages
Solution Approach 2:
The invention applies the extraction principle by using an extractive distillation column with a solvent (such as sulfolane, N-methyl-2-pyrrolidone, or N,N-dimethylformamide) to selectively remove aromatic compounds from the reformate effluent. This separation step isolates the desired aromatics (benzene, toluene, xylenes) from the reformate, preventing coke-forming compounds from contacting the catalyst during subsequent reforming operations
2Object-generated harmful factors
If extraction of aromatic compounds is performed before reforming, then coke formation is reduced, but the process complexity increases
Solution Approach 1:
The process merges the extraction and reforming operations into an integrated flow where the extractive distillation column and reforming units work in sequence. The raffinate stream from extraction is combined with fresh naphtha feed and sent to reforming, while the extract stream containing aromatics is processed separately. This merging allows the system to handle coke reduction and aromatic production in a coordinated manner without requiring completely separate process trains
Solution Approach 2:
The process applies discarding and recovering by separating the reformate into a raffinate stream (discarded from the aromatic product stream but recovered for reuse) and an extract stream (containing the desired aromatics). The raffinate, which contains mostly paraffins and naphthenes that did not form aromatics during reforming, is recycled back to the reforming unit after combining with fresh feed, thereby recovering valuable hydrocarbons that would otherwise be wasted
3Productivity
If raffinate is recycled to reforming unit, then aromatic production is maximized, but the unit for extraction must be repositioned relative to reforming units
Solution Approach 1:
The process applies segmentation by dividing the reforming system into multiple parallel reforming units (first reforming unit and second reforming unit) that process different feed streams. The first reforming unit processes a mixture of fresh naphtha and recycled raffinate, while the second reforming unit processes only fresh naphtha. This segmentation allows independent optimization of each reforming stream and simplifies the integration of the extraction unit, as the extraction column can be positioned to receive effluent from either or both reforming units without requiring complex reconfiguration of the entire process
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 effectively limits catalyst deactivation, increasing the yield of benzene and toluene by reducing coke formation on zeolitic catalysts, thereby enhancing the stability and performance of the catalytic reforming process.
Implementation Method 1
the upper stream and a stream predominantly comprising C6-C7 aromatic compounds obtained on conclusion of stage e) are sent into a unit for extraction of the aromatics in order to obtain an aromatic base and a liquid effluent
Implementation Method 2
The main reactions involved are the dehydrogenation of naphthenes and the dehydrocyclization of paraffins to give aromatics
Implementation Method 3
the dehydrogenation of naphthenes and the dehydrocyclization of paraffins to give aromatics
Implementation Method 4
a naphtha stream is sent into a fractionation unit, generating a first stream comprising C7 and lighter hydrocarbons and a second stream comprising heavier hydrocarbons
Data Source
AI summary
Process for the production of C6-C7 aromatic compounds from a hydrocarbon feedstock of naphtha type comprising the following stages:a) the said feedstock (1) is sent into a first fractionation unit (2) in order to obtain an upper stream (3) comprising C6 and C7 hydrocarbon compounds and a lower stream (4) comprising C8 to C10 hydrocarbon compounds;b) the upper stream (3) and a stream (12) comprising C6 and C7 aromatic compounds obtained on conclusion of stage e) are sent into a unit for extraction of the aromatics (5) in order to obtain an aromatic base (6) and a liquid effluent (7);c) the liquid effluent (7) is sent into a first catalytic reforming unit (8) in order to obtain a first reformate effluent (9);d) the said first reformate effluent (9) is sent into a reformate separation section (10) in order to obtain a first stream (11) comprising C5 hydrocarbon compounds and a second stream (12) comprising C6 and C7 aromatic compounds;e) the second stream (12) comprising C6 and C7 aromatic compounds is recycled in stage b).