Bifunctional Catalyst for C9+ Aromatic Dealkylation
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Solution Overview
Problem
The refining and petrochemical industry faces challenges in producing high-purity benzene and xylenes due to the hydrogenation of C9+ aromatics, which results in saturated by-products that complicate separation and reduce catalyst efficiency, particularly when processing heavy C9+ aromatics, leading to issues with catalyst selectivity and ring saturation.
Innovation Solution
A catalyst system comprising a metallic function from a metal constrained within microporous material with cages defined by 8 tetrahedral atoms or fewer and an acidic function from an additional zeolite with channels defined by 10 or more tetrahedral atoms, coupled by a binder, is used to dealkylate C9+ aromatic hydrocarbons, hydrogenate olefins, and transalkylate to produce xylene while minimizing ring saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydrogenation catalyst is used to saturate olefins formed during dealkylation, then olefin saturation is improved, but aromatic ring saturation increases causing reduced yields and increased separation difficulty
Solution Approach 1:
The catalyst system is segmented into two distinct functional components: a metal function (Pt, Pd, Rh, Ir) for selective olefin hydrogenation and an acidic zeolite function for dealkylation. This segmentation allows each component to perform its specific function with high selectivity, preventing the unwanted hydrogenation of aromatic rings while effectively saturating olefins.
Solution Approach 2:
The invention uses a composite catalyst material combining metal particles (0.1-5 wt%) with acidic zeolite support (e.g., ZSM-5, ZSM-11, ZSM-22). The composite structure enables synergistic effects where the metal provides hydrogenation activity and the zeolite provides shape-selective dealkylation, achieving high olefin saturation with minimal aromatic ring saturation.
2Productivity
If transalkylation activity is increased to produce more xylene, then xylene production is improved, but catalyst life is reduced due to coke formation from C10+ precursors
Solution Approach 1:
The invention converts the harmful effect of olefin accumulation (which leads to coke formation) into a beneficial outcome by selectively hydrogenating olefins to alkanes. This eliminates the coke precursors while maintaining high transalkylation activity, thus extending catalyst life without sacrificing xylene production.
Solution Approach 2:
The catalyst performs preliminary hydrogenation of olefins before they can undergo polymerization and coke formation. By removing olefins in advance through selective hydrogenation, the system prevents the formation of C10+ coke precursors that would otherwise deactivate the catalyst.
3Productivity
If dealkylation activity is increased to process more C9+ aromatics, then conversion efficiency is improved, but unsaturated species accumulate causing carbon deposit and blocking active sites
Solution Approach 1:
The invention converts the harmful unsaturated species (olefins) generated during dealkylation into beneficial saturated species (alkanes) through selective hydrogenation. This eliminates carbon deposit formation while maintaining high dealkylation activity for processing C9+ aromatics.
Solution Approach 2:
The metal function acts as an intermediary that captures and saturates olefins immediately after they are generated by the acidic zeolite function during dealkylation. This intermediary action prevents olefins from accumulating and forming carbon deposits on the catalyst surface.
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 catalyst system effectively dealkylates C9+ aromatics, hydrogenates olefins to alkanes, and transalkylates to produce xylene with high purity, reducing ring loss and maintaining catalyst activity, thus enhancing the separation of desired aromatics and extending catalyst life.
Implementation Method 1
a metal function to saturate olefins formed during dealkylation
Implementation Method 2
a metal constrained within cages and/or channels of a microporous material, wherein the cages and/or channels of the microporous material are defined by 8 tetrahedral atoms or fewer
Data Source
AI summary
A catalyst may include a metallic function derived from a metal constrained within cages and/or channels of a microporous material, wherein the cages and/or channels of the microporous material are defined by 8 tetrahedral atoms or fewer; and an acidic function derived from an additional zeolite having cages and/or channels defined by 10 or more tetrahedral atoms, wherein the microporous material providing the metallic function and additional zeolite providing the acidic function are coupled by a binder.