Propylene Production via Segmented Fluidized-Bed Reactors
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Solution Overview
Problem
Existing methods for producing propylene and C4 hydrocarbons from methanol suffer from low reaction rates of ethylene alkylation, leading to inefficient use of catalysts and reduced selectivity of target products, resulting in low unit volume production capacity and high content of lower-value hydrocarbons in the product gas.
Innovation Solution
A turbulent fluidized-bed reactor system is employed, featuring multi-stage feeding of oxygen-containing compounds and direct regeneration of catalysts, which enhances the alkylation reaction rate by maintaining catalyst activity and uniform concentration of reactants, thereby improving the selectivity of propylene and C4 hydrocarbons production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If methanol-to-olefin reaction is carried out using acidic molecular sieve catalysts, then propylene and C4 hydrocarbons are produced, but the MTO reaction rate is much higher than the alkylation reaction rate, leading to carbon deposition and reduced catalyst activity
Solution Approach 1:
The patent divides the reaction system into two separate reactors: a first reactor for MTO reaction and a second reactor for alkylation reaction. This segmentation allows each reactor to be optimized for its specific function, preventing the MTO reaction from dominating and causing carbon deposition in the alkylation reactor, thus maintaining catalyst activity while achieving high productivity
Solution Approach 2:
The patent introduces an intermediary substance (ethylene) that is produced in the first reactor and then fed to the second reactor for alkylation with methanol. This intermediary approach separates the high-rate MTO reaction from the slower alkylation reaction, allowing the alkylation reactor to receive a controlled amount of ethylene without being overwhelmed by rapid MTO reaction and carbon deposition
2Manufacturing precision
If light fractions are recycled to increase alkylation rate, then selectivity of propylene and C4 hydrocarbons is improved, but the content of light fractions in product gas increases, reducing unit volume production capacity
Solution Approach 1:
The patent changes the operating parameters of the two reactors to optimize the balance between selectivity and productivity. By adjusting temperature, pressure, and catalyst types in each reactor separately, the system achieves high selectivity for propylene and C4 hydrocarbons while controlling the content of light fractions in the final product, thus maintaining high unit volume production capacity
3Device complexity
If a single reactor is used for both MTO reaction and alkylation of olefins, then process complexity is reduced, but the reaction rate of alkylation is suppressed due to rapid MTO reaction and carbon deposition
Solution Approach 1:
The patent segments the reaction system into two separate reactors with different catalysts and operating conditions. The first reactor uses a catalyst optimized for MTO reaction, while the second reactor uses a catalyst optimized for alkylation reaction. This segmentation prevents the MTO reaction from suppressing the alkylation reaction rate and causing excessive carbon deposition, thereby maintaining high productivity
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 system achieves a high yield of propylene and C4 hydrocarbons with reduced content of light fractions and higher unit volume production capacity, effectively increasing the economic viability of the process by optimizing catalyst activity and reaction conditions.
Implementation Method 1
The technology utilized a ZSM-5 molecular sieve catalyst from Sud-Chemie AG to carry out methanol-to-olefin reaction
Implementation Method 2
A turbulent fluidized-bed reactor system is employed
Data Source
Figure 1
AI summary
The present invention refers to a method and device for preparing propylene and C4 hydrocarbons from oxygen-containing compounds. By means of circulating 80 wt.% or more of the hydrocarbons with 5 or more carbons in the product into a catalytic cracking lift pipe to perform a cracking reaction to generate a product containing propylene and C4 hydrocarbons, the method improves the reaction rate of ethylene alkylation, and the unit volume production capacity of reactor is high.