Catalytic Cracking Process for High Propylene Yield
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Solution Overview
Problem
Current processes for producing propylene and aromatics from hydrocarbon oils face limitations such as low yields, reliance on scarce light feedstocks, high production costs, and inability to simultaneously produce light olefins and aromatics efficiently.
Innovation Solution
A multi-step process involving hydrotreating, catalytic cracking, and steam cracking, with specific temperature and WHSV conditions in multiple reaction zones, using zeolite-based catalysts and recycling of catalysts and gases to enhance propylene and aromatics production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam cracking is used to produce propylene from light oils, then propylene can be produced, but the propylene yield is low (only about 15% by weight) and light feedstocks are scarce
Solution Approach 1:
The patent changes the feedstock type from light oils to heavy oils (vacuum gas oil) and adjusts reaction parameters (temperature 400-800°C, WHSV 0.1-750 h⁻¹) to achieve high propylene yield (exceeding 30%) from heavy feedstocks, resolving the contradiction between propylene yield and light feedstock availability
Solution Approach 2:
Instead of using conventional steam cracking with light oils, the patent inverts the approach by using heavy oils as feedstock and employing catalytic cracking with zeolite catalysts to produce light olefins, thereby overcoming the limitation of scarce light feedstocks
2Productivity
If FCC is used to produce propylene from heavy oils, then propylene yield improves, but the process cannot simultaneously produce aromatics efficiently
Solution Approach 1:
The patent employs a dual-function catalytic cracking system using zeolite catalysts that can simultaneously produce both light olefins (propylene, ethylene) and aromatics (toluene, xylene) from heavy oil feedstock, achieving multi-product production in a single process
Solution Approach 2:
The patent divides the reaction process into multiple reaction zones with different temperature conditions (first zone: 400-600°C for olefin production, second zone: 600-800°C for aromatic production) to simultaneously optimize both propylene and aromatics yields
3Productivity
If conventional catalytic cracking is used, then propylene can be produced, but production cost is high
Solution Approach 1:
The patent optimizes reaction parameters including temperature (400-800°C), WHSV (0.1-750 h⁻¹), and catalyst type (zeolite-based) to improve propylene yield (exceeding 30%) and reduce production costs by increasing feedstock utilization efficiency
Solution Approach 2:
The patent implements catalyst regeneration in-situ within the reaction system, where coke deposited on the catalyst is burned off using process gases, enabling continuous operation without catalyst replacement and reducing operational costs
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 process achieves propylene yields exceeding 30% and produces aromatics like toluene and xylene, addressing the shortage of chemical feedstocks and increasing refinery benefits by converting the refinery mode from fuel production to chemical industry production.
Implementation Method 1
a feedstock comes into contact with a catalytic cracking catalyst and reacts under the conditions of a reaction temperature between 400° C. and 800° C., and a WHSV between 0.1 h−1 and 750 h−1
Implementation Method 2
The active component of the catalyst is mainly an intermediate pore size zeolite
Implementation Method 3
uses a catalyst with ZSM-5 and/or ZSM-11 zeolites as active components
Implementation Method 4
the reaction temperature of at least one reaction zone among the reaction zones at the down stream side of the first reaction zone is higher than that of the first reaction zone
Data Source
AI summary
A process for producing light olefins and aromatics, which comprises reacting a feedstock by contacting with a catalytic cracking catalyst in at least two reaction zones, wherein the reaction temperature of at least one reaction zone among the reaction zones downstream of the first reaction zone is higher than that of the first reaction zone and its weight hourly space velocity is lower than that of the first reaction zone, separating the spent catalyst from the reaction product vapor, regenerating the separated spent catalyst and returning the regenerated catalyst to the reactor, and separating the reaction product vapor to obtain the desired products, light olefins and aromatics. This process produces maximum light olefins such as propylene, ethylene, etc from heavy feedstocks, wherein the yield of propylene exceeds 20% by weight, and produces aromatics such as toluene, xylene, etc at the same time.