Heavy Aromatic Solvents for Catalyst Soft Coke Removal
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Solution Overview
Problem
Current methods for catalyst reactivation in hydrocarbon conversion processes, such as solvent washing and hot hydrogen stripping, are insufficient for reliable and efficient removal of soft coke deposits, leading to catalyst deactivation and reduced process efficiency.
Innovation Solution
Utilizing a heavy aromatic solvent stream from an aromatic recovery complex, with a high Hildebrand solubility parameter, to dissolve and remove soft coke from catalyst surfaces, thereby restoring catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solvent washing or hot hydrogen stripping is used to remove soft coke, then catalyst activity can be partially restored, but the removal is unreliable and inefficient, leading to catalyst deactivation
Solution Approach 1:
The patent applies parameter changes by selecting solvents with specific Hildebrand solubility parameters (δ between 18-22 MPa^1/2) and aromaticity indices (AI ≥ 0.35) to optimize soft coke removal. This quantitative parameter approach transforms the unreliable conventional washing into a controlled process where solvent properties are precisely matched to coke composition, ensuring reliable and efficient catalyst reactivation.
Solution Approach 2:
The patent uses an intermediary substance approach by introducing specially selected aromatic solvents that act as mediators between the coke deposits and catalyst surface. These solvents with specific solubility parameters serve as intermediate carriers that selectively dissolve soft coke while leaving the catalyst intact, enabling reliable removal without direct mechanical or thermal treatment that could damage the catalyst.
2Quantity of substance
If heavy feedstreams with high concentrations of nitrogen, sulfur, and PNA compounds are processed, then feedstock utilization is improved, but catalyst deactivation accelerates and unit efficiency decreases
Solution Approach 1:
The patent applies preliminary action by implementing solvent washing to remove soft coke deposits before they can convert to hard coke and cause permanent catalyst deactivation. This preventive maintenance approach allows continuous processing of heavy feedstreams with high nitrogen, sulfur, and PNA concentrations while periodically restoring catalyst activity, thereby extending catalyst life cycle without reducing feedstock utilization.
Solution Approach 2:
The patent enables self-service by allowing the catalyst to be regenerated in-situ within the reactor system using circulated solvents. The catalyst bed itself serves as the reaction zone for both hydrocracking and solvent washing operations, eliminating the need for external regeneration facilities and enabling continuous self-maintenance of catalyst activity during heavy feedstock processing.
3Ease of manufacture
If single-stage once through hydrocracking is used, then cost effectiveness is improved, but product yields are relatively low with maximum conversion rate of about 60%
Solution Approach 1:
The patent applies continuity of useful action by implementing periodic solvent washing cycles within the continuous hydrocracking process. The reactor operates continuously for hydrocracking, and when soft coke accumulates, solvent is circulated through the same reactor to remove deposits without shutting down the process. This continuous operation with intermittent regeneration maintains high conversion rates (>60%) while preserving the cost-effectiveness of single-stage processing.
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
The aromatic solvent effectively removes soft coke deposits, reducing pressure drops and maintaining catalyst activity, and can be applied in both hydrotreating and hydrocracking processes, enhancing the efficiency and longevity of catalysts.
Implementation Method 1
a heavy aromatic solvent for soft coke washing and removal comprises C9+, C10+, or C11+ heavy aromatic compounds
Data Source
AI summary
Compositions and methods for restoring catalytic activity by dissolving soft coke with a solvent, one method including detecting soft coke deposition on a catalyst composition; preparing an aromatic bottoms composition with a Hildebrand solubility parameter of at least about 20 SI to remove the soft coke from the catalyst composition; and washing the catalyst composition with the aromatic bottoms composition until at least a portion of the soft coke deposition is removed.