Composite Molecular Sieve Catalyst for Fluidized Bed Cracking
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Solution Overview
Problem
Current catalytic cracking processes for producing ethylene and propylene in fluidized-bed reactors face challenges with high reaction temperatures, low catalyst activity, and poor selectivity, as well as inadequate hydrothermal stability and regeneration of molecular sieves used in existing catalysts.
Innovation Solution
A catalyst comprising a composite molecular sieve support with a specific chemical formula, including rare earth elements and transition metals, co-grown with molecular sieves such as ZSM-5, Y zeolite, β zeolite, MCM-22, SAPO-34, and mordenite, which enhances acid amount and acidity, allowing for better processing of complex feedstocks and achieving higher ethylene and propylene yields at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If molecular sieves with high silica to alumina ratio are used as catalytic materials, then ethylene and propylene selectivity is improved, but hydrothermal stability deteriorates and regeneration becomes difficult
Solution Approach 1:
The patent uses composite molecular sieves containing multiple types of molecular sieves (ZSM-5, Y zeolite, β zeolite, MCM-22, SAPO-34, and mordenite) with different pore structures and catalytic properties. This composite structure combines the high selectivity of high-silica molecular sieves with the hydrothermal stability of other components, resolving the contradiction between selectivity and stability.
Solution Approach 2:
The patent modifies the chemical composition parameters of the molecular sieves by incorporating rare earth elements (La, Ce, Nd) and transition metals (Mn, Fe, Co, Ni, Cu, Zn, Cr, Mo) in specific amounts. These parameter changes enhance both the selectivity and hydrothermal stability simultaneously, rather than trading one for the other.
2Productivity
If high reaction temperature is used in steam pyrolysis, then ethylene and propylene production is improved, but energy consumption and equipment requirements increase
Solution Approach 1:
The patent replaces the thermal energy-driven steam pyrolysis process with a catalyst-driven catalytic cracking process. The composite molecular sieve catalyst provides active sites that lower the activation energy required for cracking, enabling ethylene and propylene production at lower temperatures (500-700°C) compared to conventional steam pyrolysis (750-900°C), thus reducing energy consumption.
Solution Approach 2:
The patent changes the temperature parameter from high-temperature steam pyrolysis to moderate-temperature catalytic cracking. By introducing the catalyst, the reaction can proceed efficiently at lower temperatures while maintaining high productivity, directly addressing the energy consumption issue.
3Adaptability or versatility
If conventional catalysts are used in fluidized-bed reactors, then processing capability is improved, but catalyst activity and selectivity deteriorate
Solution Approach 1:
The patent employs a composite molecular sieve catalyst system that combines multiple molecular sieve types with complementary properties. ZSM-5 provides high selectivity for light olefins, Y zeolite offers high activity, β zeolite contributes to hydrothermal stability, and other components fill specific catalytic niches. This composite structure maintains high activity and selectivity while adapting to fluidized-bed reactor conditions.
Solution Approach 2:
The patent applies the concept of local quality by assigning different functional roles to different components within the composite catalyst. Each molecular sieve type and metal addition provides specific local catalytic functions (e.g., cracking, isomerization, aromatization) that collectively enhance overall catalyst performance in the fluidized-bed reactor.
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 higher ethylene and propylene yields with improved selectivity and stability, effectively processing complex raw materials by leveraging the synergistic catalytic effects of co-grown molecular sieves, resulting in enhanced catalytic performance and reduced coking.
Implementation Method 1
catalytic cracking is the most attractive and promising. The object thereof is to find a suitable cracking catalyst so as to increase the selectivity to ethylene and propylene
Implementation Method 2
most catalytic cracking researchers generally use molecular sieves having a high silica to alumina ratio as catalytic materials
Data Source
AI summary
A catalyst for catalytic cracking in a fluidized-bed is disclosed. The catalyst comprises a support and a composition having the chemical formula (on the basis of the atom ratio): AaBbPcOx for use in the industrial production of ethylene and propylene by catalytically cracking naphtha.