Hierarchical Ga-ZSM-5 Catalyst for Alkane Aromatization

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Solution Overview

Problem

Current aromatization catalysts, such as gallium-modified ZSM-5 zeolites, face challenges in selectivity to aromatic hydrocarbons, lifetime, and thermal stability when converting lower alkanes into benzene, toluene, and xylene.

Innovation Solution

Aromatization catalyst comprising a modified Ga-ZSM-5 zeolite with hierarchical macro-meso-microporosity and gallium deposition, combined with an inorganic oxide, which enhances gallium dispersion and catalytic activity, improving selectivity and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If gallium-modified ZSM-5 zeolite is used for aromatization of lower alkanes, then catalytic activity is improved, but selectivity to aromatic hydrocarbons deteriorates (only 30-40%)

Engineering Contradiction:

Improvecatalytic activityVSAvoidselectivity to aromatic hydrocarbons

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent combines gallium-modified ZSM-5 zeolite with hierarchical macro-meso-microporosity structure and inorganic oxide support to create a composite catalyst system. This composite structure integrates the high catalytic activity of gallium-modified ZSM-5 with the improved mass transfer and selectivity properties of hierarchical porosity, achieving both high aromatic hydrocarbon selectivity (up to 73.3%) and maintained catalytic activity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces a hierarchical macro-meso-microporosity structure into the ZSM-5 zeolite catalyst. The micropores provide shape selectivity for aromatic hydrocarbon formation, mesopores improve mass transfer and reduce diffusion limitations, and macropores facilitate reactant access and product removal. This hierarchical porous structure resolves the contradiction between activity and selectivity by optimizing both reaction sites and mass transport pathways

Inventive Principle:

Principle #31Porous materials

2Productivity

If gallium-modified ZSM-5 zeolite is used for aromatization, then catalytic activity is improved, but lifetime and thermal stability deteriorate

Engineering Contradiction:

Improvecatalytic activityVSAvoidlifetime and thermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces inorganic oxide as an intermediary support material that stabilizes the gallium-modified ZSM-5 zeolite structure. The inorganic oxide support provides thermal stability and structural integrity at high reaction temperatures, preventing zeolite collapse and gallium sintering, thereby extending catalyst lifetime while maintaining high catalytic activity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The composite catalyst system combines gallium-modified ZSM-5 zeolite with inorganic oxide support, where the inorganic oxide component provides thermal stability and structural reinforcement. This composite structure allows the catalyst to withstand high-temperature aromatization conditions (typically 400-600°C) without degradation, resolving the contradiction between maintaining high activity and ensuring long-term stability

Inventive Principle:

Principle #40Composite materials

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 achieves high selectivity to aromatic hydrocarbons (up to 73.3%) and prolonged lifetime (up to 320 hours) during the aromatization of lower alkanes, with improved thermal stability and recyclability.

Implementation Method 1

subjecting the modified ZSM-5 zeolite to be ion-exchanged with a solution of gallium salt and then to be calcined to obtain a modified Ga-ZSM-5 zeolite

Methodology Applied

Scientific EffectIon exchange: Ion Exchange

Implementation Method 2

The hierarchical porosity of the modified ZSM-5 zeolite in the catalyst can reduce diffusion resistance of products during the aromatization reaction

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 3

adding a silicon source into a mixed aqueous solution containing an aluminum source and a first structure directing agent to perform a hydrothermal reaction so as to obtain a first solid product, which is then subjected to calcination to obtain a ZSM-5 zeolite precursor

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Implementation Method 4

gallium deposited in channels of and/or on surfaces of the modified ZSM-5 zeolite... exhibits an excellent catalytic activity for aromatization of lower alkanes, a high selectivity to aromatic hydrocarbons

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentUS11305265B2Aromatization catalyst and preparation process and use thereof

Publication Date: 2022.04.19 SHANXI LUAN MINING GRP

AI summary

An aromatization catalyst and preparation process and use thereof is set forth. The catalyst comprises an inorganic oxide and a modified Ga-ZSM-5 zeolite, which comprises a modified ZSM-5 zeolite with a hierarchical macro-meso-microporosity and gallium deposited in channels of and/or on surfaces of the modified ZSM-5 zeolite. The hierarchical porosity of the modified ZSM-5 zeolite in the catalyst can reduce diffusion resistance of products during the aromatization reaction, thereby retarding carbon depositing rate and substantially improving catalytic activity, aromatic hydrocarbon selectivity, stability and lifetime of the catalyst. When being used in aromatization of propane, the catalyst exhibits a high stability, a lifetime of more than 320 hours, and a selectivity to aromatic hydrocarbons of up to 73.3 wt. %.