Hydrocracking HPNA Removal via Ionic Liquid Extraction and Adsorption
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Solution Overview
Problem
The formation of heavy poly-nuclear aromatic (HPNA) compounds in hydrocracking processes leads to equipment fouling and catalyst deactivation, reducing the efficiency and lifespan of hydrocracking units, and existing methods for removing these compounds are either inefficient or costly.
Innovation Solution
A process that combines adsorption and ionic liquid extraction to remove HPNA compounds from hydrocracking unit recycle streams, either starting with adsorption followed by ionic liquid extraction or vice versa, to produce a reduced-HPNA hydroprocessed bottoms stream, which can be recycled back into the hydrocracking unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrocracking is performed at elevated temperature and pressure to process heavy feeds, then conversion of heavy molecules to lighter products is improved, but heavy poly nuclear aromatic (HPNA) compounds form and accumulate in the recycle stream
Solution Approach 1:
The patent extracts HPNA compounds from the recycle stream using a two-step process: first adsorption on solid adsorbents (such as zeolites or activated carbon) to remove bulk HPNAs, then liquid-liquid extraction with selective solvents (such as polar solvents or ionic liquids) to remove remaining HPNAs. This separation allows the recycle stream to be returned to the hydrocracker without HPNA accumulation, enabling continuous operation at elevated temperatures and pressures.
2Reliability
If HPNA compounds are removed from the recycle stream using conventional methods, then equipment fouling and catalyst deactivation are reduced, but the process becomes more complex and costly
Solution Approach 1:
The patent segments the HPNA removal process into two distinct functional stages: adsorption using solid adsorbent materials to capture the majority of HPNA compounds, followed by liquid-liquid extraction using selective solvents to remove residual HPNAs. This segmentation allows each stage to be optimized independently and enables the use of relatively simple, well-established unit operations that can be integrated into existing hydrocracking facilities without requiring complex new equipment.
Solution Approach 2:
The patent introduces solid adsorbents and selective liquid solvents as intermediary substances that facilitate HPNA removal. These intermediaries selectively bind to or dissolve HPNA compounds from the recycle stream, allowing the HPNAs to be separated and removed while leaving the desired hydrocarbon products intact. The intermediaries can then be regenerated or disposed of separately, simplifying the overall process.
3Device complexity
If single-stage once through hydrocracking is used, then process simplicity is improved, but product yield is limited to about 60% conversion rate
Solution Approach 1:
The patent applies preliminary action by removing HPNA compounds from the recycle stream before the hydrocracking reaction occurs. By preventing HPNA accumulation in advance, the process enables more aggressive hydrocracking conditions (higher temperature, pressure, and catalyst activity) that would otherwise lead to rapid catalyst deactivation. This preliminary removal of harmful substances allows the system to achieve higher conversion rates (exceeding 60%) while maintaining process simplicity through the use of a single-stage configuration.
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 extends the catalyst lifecycle, improves hydrocracking unit efficiency, and increases product yields and quality by significantly reducing HPNA concentrations in the recycle stream, thereby avoiding the need for costly purging or additional fractionation steps.
Implementation Method 1
treating said hydrocracking unit bottoms recycle stream with an adsorbent to remove HPNA compounds
Implementation Method 2
treating said hydrocracking unit bottoms recycle stream with an ionic liquid to extract HPNA compounds
Data Source
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AI summary
A process for the treatment of a hydrocracking unit bottoms recycle stream, and preferably the fresh hydrocracker feed to remove heavy poly-nuclear aromatic (HPNA) compounds and HPNA precursors employs, in the alternative, an adsorption step which removes most of the HPNA compounds followed by an ionic liquid extraction step to remove the remaining HPNA compounds, or a first ionic liquid extraction step which removes most of the HPNA compounds followed by an adsorption step to remove the remaining HPNA compounds. Ionic liquids of the general formula Q+A- are identified for use in the process; organic polar solvents are identified for removal of the HPNA compounds in solution. Suitable adsorbents are identified for use in packed bed or slurry bed columns that operate within specified temperature and pressure ranges.