Zeolite Catalyst Propylene Yield via Acid Site Regulation

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Solution Overview

Problem

The global demand for propylene exceeds supply due to low yields in conventional steam cracking, and catalytic cracking using ZSM-5 zeolites struggles to achieve a propylene to ethylene molar ratio of 2 or higher due to limitations in controlling the distribution and strength of acid sites.

Innovation Solution

Modifying ZSM-5 zeolites with extra-framework aluminium (EFAL) species via incipient-wetness impregnation to precisely regulate the Brønsted to Lewis acid ratio, allowing for higher propylene yields through controlled acid site conversion during catalytic cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional steam cracking is used to produce propylene, then production capacity is maintained, but propylene yield is low and energy consumption is high

Engineering Contradiction:

Improvepropylene yieldVSAvoidenergy consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent changes the reaction conditions by using catalytic cracking instead of steam cracking, operating at lower temperatures (500-700°C vs >750°C) while using zeolite catalysts with specific acid site distributions to achieve higher propylene yield and selectivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces zeolite catalysts as intermediaries to facilitate the cracking reaction, where the catalyst's acid sites act as mediators to promote propylene formation through carbocation mechanisms, replacing the direct thermal cracking process

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If ZSM-5 zeolite catalysts are used for catalytic cracking, then reaction temperature is reduced, but propylene to ethylene molar ratio cannot reach 2 or higher

Engineering Contradiction:

Improvereaction temperatureVSAvoidpropylene to ethylene molar ratio

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating non-uniform distribution of acid sites within the zeolite structure, specifically concentrating Brønsted acid sites in certain regions while maintaining Lewis acid sites in others, to achieve selective propylene formation while suppressing ethylene production

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the acidity parameters of the zeolite catalyst by controlling the Si/Al ratio and adjusting the distribution of Brønsted and Lewis acid sites, optimizing the catalyst to achieve propylene to ethylene molar ratio of 2 or higher at reduced temperatures

Inventive Principle:

Principle #35Parameter changes

3Productivity

If Al content is increased to enhance acidity, then conversion rate of hydrocarbons increases, but selectivity of propylene decreases

Engineering Contradiction:

Improveconversion rateVSAvoidselectivity of propylene

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating specific acid site environments within the zeolite structure, where Brønsted acid sites promote propylene formation through selective beta-scission of carbocations, while the overall high Al content maintains high conversion rates

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite acid site system within the zeolite, combining both Brønsted and Lewis acid sites with specific ratios and distributions, where Brønsted sites (from framework Al) provide propylene selectivity and Lewis sites (from extra-framework Al) enhance overall conversion activity

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 method effectively increases propylene yield and achieves a propylene to ethylene molar ratio of 6 or higher, enhancing the selectivity and efficiency of propylene production in catalytic cracking processes.

Implementation Method 1

catalytic cracking processes using zeolites (such as ZSM-5, Beta and NaA zeolites) as a catalyst enable a reduced reaction temperature

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

the hydrocarbon molecules are bonded to surface acid centers in the ZSM-5 catalysts to generate carbocations, which then produce light olefins including ethylene and propylene by beta cleavage

Methodology Applied

Scientific EffectAcid-base reaction:

Implementation Method 3

Modifying ZSM-5 zeolites with extra-framework aluminium (EFAL) species via incipient-wetness impregnation to precisely regulate the Brønsted to Lewis acid ratio

Methodology Applied

Scientific EffectImpregnation:

Data Source

PatentUS11717813B2Zeolite catalyst for catalytic cracking of hydrocarbons to produce propylene and its preparation and use

Publication Date: 2023.08.08 HENAN UNIVERSITY

AI summary

A method for preparing a zeolite catalyst for catalytic cracking of hydrocarbons to produce propylene is provided, which specifically includes steps of mixing a silicon source, a templating agent, an aluminium source, and a solvent to form a zeolite precursor solution, which is then subjected to hydrothermal crystallization, washing, drying, and calcination to obtain a zeolite precursor; ion-exchanging the zeolite precursor with ammonium ions, followed by drying and calcination; and loading aluminum onto the ion-exchanged zeolite precursor as a carrier via incipient-wetness impregnation by using an aluminium-containing solution, followed by drying and calcination. Zeolite catalysts prepared by the method and use of the catalysts in catalytic cracking of hydrocarbons to produce propylene are also provided.