Composite Zeolite Catalyst for Aromatic Transalkylation
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Solution Overview
Problem
Existing catalyst systems for the transalkylation of C9+ aromatics face challenges in maintaining activity and catalyst life, especially when processing increasing amounts of C9+ aromatics, which leads to rapid aging and reduced selectivity for valuable products like xylenes.
Innovation Solution
A catalyst composition comprising a mixture of MEL framework zeolites like ZSM-11, MOR framework zeolites like mordenite, and optionally MFI framework zeolites like ZSM-5, combined with a silica binder and specific metal components such as Pt and Sn, demonstrates superior performance in terms of aromatic selectivity, xylene yield, and reduced catalyst aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing catalyst systems are used for transalkylation of C9+ aromatics, then transalkylation activity is maintained, but catalyst aging accelerates and selectivity for xylenes decreases
Solution Approach 1:
The patent employs a composite catalyst system comprising multiple zeolite types (MOR framework zeolite with 30-70 wt%, MFI framework zeolite with 5-40 wt%, and MEL framework zeolite with 5-40 wt%) combined with specific metal components (Pt, Sn, Ga, In, or Zn). This composite structure integrates the strengths of different zeolite frameworks to maintain transalkylation activity while improving selectivity for xylenes and reducing catalyst aging, directly resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent applies local quality by assigning different functional roles to different zeolite components within the catalyst system. The MOR framework zeolite provides high transalkylation activity, the MFI framework zeolite enhances xylene selectivity, and the MEL framework zeolite improves catalyst stability. This functional differentiation allows each component to optimize specific aspects of performance, simultaneously improving reliability and productivity.
2Productivity
If increased amounts of C9+ aromatics are processed, then feedstock utilization improves, but catalyst aging accelerates and activity decreases
Solution Approach 1:
The patent incorporates metals (Pt, Sn, Ga, In, or Zn) within the zeolite structure that act as protective elements against catalyst deactivation. These metals cushion the catalyst against the harsh conditions of processing high amounts of C9+ aromatics by preventing coking and maintaining active sites, thereby extending catalyst lifetime while enabling higher feedstock conversion rates.
Solution Approach 2:
The patent optimizes the silica-to-alumina ratio parameters of the zeolite components to enhance catalyst stability under high C9+ processing conditions. By adjusting these compositional parameters, the catalyst maintains its structural integrity and activity even when processing increased amounts of heavy aromatics, simultaneously improving productivity and extending catalyst lifetime.
3Productivity
If transalkylation activity is enhanced, then xylene production increases, but dealkylation activity and olefin saturation become challenging
Solution Approach 1:
The patent designs a multi-functional catalyst system where the zeolite components provide transalkylation activity, the metal components (Pt, Sn, Ga, In, or Zn) provide dealkylation activity and olefin saturation capability. This universal catalyst performs multiple functions simultaneously, enabling high xylene production while maintaining the necessary dealkylation and hydrogenation activities through the synergistic combination of different functional components.
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 catalyst composition achieves high aromatic selectivity, improved xylene yield, and significantly reduced catalyst aging, allowing for extended catalyst lifetime and simplified activation and start-up processes, even with higher silica to alumina ratios.
Implementation Method 1
a catalyst composition comprising: (i) a zeolite mixture comprising a first zeolite having an MEL framework type and/or an MFI framework type and a second zeolite having a MOR framework
Implementation Method 2
a metal such as Pt, and a silica binder... a combination of a first metal in Groups 7-10 and a second metal in Groups 2, and 11 to 15 in the Periodic Table of Elements
Data Source
AI summary
Methods and corresponding catalysts are provided for conversion of an aromatic feed containing C8+ aromatics (particularly C9+ aromatics) to form a converted product mixture comprising, e.g., benzene and/or xylenes. The aromatic feed can be converted in the presence of a catalyst that includes a silica binder, a mixture of a first zeolite having an MEL framework (such as ZSM-11 and/or an MFI framework (such as ZSM-5), and a second zeolite having an MOR framework, such as mordenite, particularly a mordenite synthesized using TEA or MTEA as a structure directing agent, and a metal. The catalyst can further include one or more metals supported on the catalyst.