Two-Stage Zeolite Cracking for Higher Propylene Yield
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Solution Overview
Problem
Existing methods for producing propylene face challenges in achieving sustainable production with limited capacity, high GHG emissions, and dependence on petroleum sources, particularly in terms of flexibility and yield.
Innovation Solution
A two-stage catalytic cracking process using different zeolite catalysts in each stage, with specific temperature ranges and separation of lighter and heavier fractions, to optimize conversion and reduce secondary reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-stage catalytic cracking is used to produce propylene from sustainable hydrocarbons, then the process complexity is reduced, but the propylene yield and selectivity deteriorate due to secondary reactions and coking
Solution Approach 1:
The catalytic cracking process is divided into two distinct stages, each with optimized conditions for maximizing propylene yield. The first stage operates at lower temperature (350-500°C) with a first zeolite catalyst to produce initial cracking products, while the second stage operates at higher temperature (450-750°C) with a second zeolite catalyst to convert intermediates to propylene, thereby reducing secondary reactions and coking compared to one-stage processes
2Productivity
If higher cracking temperature is used to increase conversion, then the conversion efficiency is improved, but secondary reactions and coking increase
Solution Approach 1:
The temperature profile is segmented across two stages: the first stage uses moderate temperature (350-500°C) to perform initial cracking with minimal coking, while the second stage uses higher temperature (450-750°C) to maximize propylene production from intermediates. This segmentation allows high overall conversion while controlling secondary reactions and coking through staged temperature increase
Solution Approach 2:
The first cracking stage performs preliminary conversion of sustainable hydrocarbon feed into intermediate products before the second stage. This preliminary action prepares the feed composition for optimal propylene production in the second stage, reducing the burden on high-temperature conditions to perform both conversion and propylene formation simultaneously, thereby reducing coking and secondary reactions
3Ease of manufacture
If conventional cracking catalysts are used for sustainable feedstocks, then the catalyst availability is improved, but the flexibility and adaptability to varying feed compositions deteriorate
Solution Approach 1:
Different zeolite catalysts with specific local properties are assigned to each stage: the first zeolite catalyst is selected for optimal performance with sustainable hydrocarbon feeds at lower temperatures, while the second zeolite catalyst is selected for optimal propylene production from cracked intermediates at higher temperatures. This local optimization of catalyst properties for each stage enhances overall flexibility and adaptability to varying feed compositions while using commercially available catalysts
4Productivity
If steam cracking of naphtha is used to produce propylene, then the production capacity is increased, but the propylene is produced only as a side-product rather than the main product
Solution Approach 1:
The process parameters (temperature, catalyst type, stage configuration) are optimized specifically to make propylene the main product rather than a side-product. The two-stage catalytic cracking with zeolite catalysts at controlled temperatures (350-750°C across stages) achieves high propylene selectivity (up to 80% of liquid products) while maintaining production capacity, unlike steam cracking where propylene is only a side-product
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
Enhances propylene yield and flexibility in handling varying sustainable hydrocarbon feeds, reducing secondary reactions and coking, while minimizing environmental impact.
Implementation Method 1
subjecting a first cracking feed comprising the sustainable hydrocarbon feed to catalytic cracking reaction in the presence of a first cracking catalyst comprising a first zeolite at a temperature within a range from 300 to 700 °C
Implementation Method 2
catalytic cracking reaction in the presence of a first cracking catalyst comprising a first zeolite at a temperature within a range from 300 to 700 °C
Implementation Method 3
subjecting a second cracking feed comprising at least a portion of the first catalytically cracked stream to catalytic cracking reaction in the presence of a second cracking catalyst comprising a second zeolite at a temperature within a range from 350 to 750 °C
Implementation Method 4
catalytic cracking reaction in the presence of a second cracking catalyst comprising a second zeolite at a temperature within a range from 350 to 750 °C
Data Source
Figure 1
Figure 2
Figure 3(A)~3(C)
AI summary
The present disclosure relates to a method for producing propylene D, in particular to methods comprising subjecting a sustainable hydrocarbon feed A to a first catalytic cracking 20 in the presence of a first cracking catalyst comprising a first zeolite, followed by a second catalytic cracking 30 in the presence of a second cracking catalyst comprising a second zeolite. The first and the second zeolite are selected from zeolites of a 10 MR framework type, hierarchical zeolites of a 10 MR framework type and zeolites of a 12 MR framework type, and the second zeolite has a framework type that is different from the first zeolite unless both the first and the second zeolite are hierarchical zeolites of a 10 MR framework type, with the proviso that when the first zeolite is a zeolite of a 10 MR framework type, the second zeolite is a hierarchical zeolite of a 10 MR framework type or a zeolite of a 12 MR framework type.