Modified Zeolite Catalyst for Naphtha Cracking Coke and Heat Balance
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Solution Overview
Problem
Existing catalytic cracking processes for producing light olefins and aromatics face challenges in managing coke selectivity during fluidization without compromising yields and selectivity, and there is a need for an efficient apparatus and catalyst to enhance the production of light olefins and aromatics while maintaining unit heat balance.
Innovation Solution
A catalyst is prepared by mixing ortho-phosphoric acid, hydrous kaolin clay, ammonia stabilized colloidal silica, and modified alumina with ZSM-5 zeolite, followed by spray drying and calcination, which includes a modified alumina only on the surface of ZSM-5 zeolite to enhance coke formation and selectivity, and a process involving a riser, gas-solid separation, stripping, and regeneration to optimize hydrocarbon cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite catalysts are used for catalytic cracking of naphtha, then light olefin yield is enhanced, but coke selectivity becomes difficult to manage during fluidization
Solution Approach 1:
The catalyst incorporates metal phosphates specifically on the zeolite surface rather than uniformly throughout, creating localized active sites that promote light olefin formation while controlling coke deposition. The metal phosphate coating is applied only where needed to enhance catalytic activity without causing excessive coke formation throughout the entire catalyst structure.
Solution Approach 2:
The invention creates a composite catalyst system combining zeolite with metal phosphates (such as gallium phosphate, indium phosphate, or zinc phosphate). This composite structure integrates the shape-selective properties of zeolite with the coke-promoting characteristics of metal phosphates, achieving both high light olefin yield and manageable coke selectivity through synergistic material interaction.
2Productivity
If reaction temperature is increased to enhance cracking activity, then light olefin production increases, but energy consumption increases
Solution Approach 1:
The catalyst modification changes the chemical parameters of the catalytic system by introducing metal phosphates that alter the reaction mechanism. This allows the cracking reaction to proceed at lower temperatures (500-650°C) while maintaining high light olefin production, as the metal phosphate-modified zeolite provides alternative reaction pathways with lower energy barriers.
3Productivity
If catalyst activity is increased to improve cracking efficiency, then light olefin yield increases, but heat balance of the unit becomes difficult to sustain
Solution Approach 1:
The invention converts the previously harmful coke deposition into a beneficial feature by using metal phosphates that selectively promote coke formation. The coke produced on the catalyst surface serves as an internal heat source through its combustion during regeneration, helping to sustain the unit heat balance while the controlled coke formation does not excessively block active sites or reduce catalytic activity.
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 yields of light olefins and aromatics with improved propylene to ethylene ratio and BTX selectivity, while managing coke formation and maintaining heat balance through in-situ coke production and regeneration.
Implementation Method 1
catalytic cracking of naphtha to light olefins and aromatics
Implementation Method 2
solid acid catalysts that include zeolites, metals supported on zeolites
Implementation Method 3
enhance coke formation and selectivity
Implementation Method 4
spray drying and calcination
Implementation Method 5
spray drying and calcination
Implementation Method 6
gas-solid separation
Data Source
AI summary
The present invention pertains to a catalytic cracking. More specifically, the present invention pertains to a process for the preparation of a catalyst for cracking a hydrocarbon stream wherein the catalyst comprises a modified zeolite and a modified alumina. The present invention further provides a process and an apparatus for the cracking of a hydrocarbon stream into higher yield of lighter olefins and aromatics by employing the catalyst while sustaining the unit heat balance. The catalyst of the present invention shows enhanced coke formation, higher propylene to ethylene weight ratio and a higher BTX selectivity when used in the cracking of hydrocarbon stream.