Fast Fluidized-Bed Reactor for Propylene Alkylation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing propylene and C4 hydrocarbons from methanol suffer from low reaction rates of ethylene alkylation and high content of light fractions, leading to low unit volume production capacity and economic inefficiencies due to carbon deposition on catalysts, which inhibits the alkylation of olefins.
Innovation Solution
A fast fluidized-bed reactor system with a dense phase zone at the bottom and a dilute phase zone above, where the catalyst is regenerated and the light fractions are recycled to react with oxygen-containing compounds, enhancing the alkylation reaction rate and reducing the inhibition of MTO on olefin alkylation, while a catalytic cracking lift pipe is used to convert hydrocarbons with 5 or more carbons into propylene and C4 hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If methanol-to-olefin reaction is carried out using SAPO catalyst, then the activity for alkylation of olefins is high initially, but carbon deposition rapidly decreases the reaction rate of alkylation
Solution Approach 1:
The reaction system is divided into two separate reactors: a first reactor for MTO reaction and a second reactor for alkylation reaction. This segmentation allows each reactor to use catalysts optimized for its specific function, preventing carbon deposition from inhibiting the alkylation catalyst activity.
Solution Approach 2:
A distillation column is introduced as an intermediary device between the two reactors to separate and purify the olefin stream before it enters the alkylation reactor. This removes carbon-containing by-products that would otherwise deposit on the alkylation catalyst and reduce its activity.
2Quantity of substance
If light fractions are recycled to increase alkylation rate, then propylene and C4 hydrocarbon yield improves, but unit volume production capacity decreases due to high light fraction content
Solution Approach 1:
The system changes the concentration parameter of light fractions in the reaction feed by controlling the recycling ratio and using distillation to adjust the composition. This optimizes the balance between alkylation rate enhancement and reactor productivity.
Solution Approach 2:
Instead of recycling all light fractions, only a controlled portion is recycled to the reactors while the rest is removed as product or used for other purposes. This partial recycling approach maintains high alkylation rates without excessively diluting the reactor feed with light fractions.
3Device complexity
If MTO reaction and alkylation are performed in one reactor, then the process is simplified, but the MTO reaction inhibits the alkylation of olefins due to carbon deposition
Solution Approach 1:
The reaction system is divided into two separate reactors: a first reactor for MTO reaction and a second reactor for alkylation reaction. This segmentation allows each reactor to use catalysts optimized for its specific function, preventing carbon deposition from inhibiting the alkylation catalyst activity.
Solution Approach 2:
The alkylation reaction is extracted from the MTO reaction system into a separate reactor. This removes the harmful effect of carbon deposition from the MTO reaction on the alkylation catalyst, allowing the alkylation reaction to proceed at high rates with a dedicated catalyst.
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 significantly increases the reaction rate of ethylene alkylation, reduces the content of light fractions in the product gas, and enhances the unit volume production capacity, achieving high yields of propylene and C4 hydrocarbons with improved process economics.
Implementation Method 1
a fast fluidized-bed reactor (1), the fast fluidized-bed reactor (1) comprises a reactor shell (2), n reactor feed distributors (3-1~3-n), a first reactor gas-solid separator (4), a second reactor gas-solid separator (5), a reactor heat extractor (6), a product gas outlet (7) and a reactor stripper (8)
Implementation Method 2
b) regenerating the spent catalyst by a fluidized-bed regenerator (14) to form a regenerated catalyst
Implementation Method 3
a first reactor gas-solid separator (4), a second reactor gas-solid separator (5)
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. The main characteristics of the method lie in that: returning 70 wt.% or more of the light fractions in the generated product to a dense phase zone of a fast fluidized-bed reactor from a reactor feed distributor at the bottom-most of the fast fluidized-bed reactor to react ethylene and the oxygen-containing compounds to perform an alkylation reaction in presence of a catalyst to produce products of propylene and the like, and circulating 80 wt.% or more of the hydrocarbons with 5 or more carbons into a catalytic cracking lift pipe to perform a cracking reaction to generate a product containing propylene and C4 hydrocarbons, which is subsequently fed into a dilute phase zone of the fast fluidized-bed reactor. The method and device of the present invention improve the reaction rate of ethylene alkylation, and the unit volume production capacity of reactor is high.