Fast Fluidized-Bed Reactor for Ethylene Alkylation
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Solution Overview
Problem
Current 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 unit volume production capacity due to carbon deposition and inhibition of the MTO reaction.
Innovation Solution
A method involving a fast fluidized-bed reactor with a dense phase zone and a regenerator, where oxygen-containing compounds are fed from multiple distributors, and the catalyst is regenerated to maintain high activity, allowing for efficient alkylation of ethylene and reducing the inhibition of MTO reaction, thereby increasing the yield of propylene and C4 hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If methanol-to-olefin reaction is carried out using acidic molecular sieve catalyst, then propylene and C4 hydrocarbons are produced, but carbon deposition occurs on the catalyst leading to reduced activity and inhibited alkylation reaction
Solution Approach 1:
The patent extracts the harmful carbon deposits from the catalyst by introducing a sulfur-containing compound that selectively reacts with and removes carbon from the catalyst surface. This allows the catalyst to maintain its activity while continuing to produce propylene and C4 hydrocarbons efficiently.
Solution Approach 2:
The sulfur-containing compound acts as an intermediary substance that mediates between the carbon deposits and the catalyst. It selectively binds to and removes carbon from the catalyst surface without damaging the catalyst's active sites, thus preserving catalyst activity while eliminating the harmful effect of carbon deposition.
2Productivity
If light fractions are recycled to increase alkylation rate, then propylene yield improves, but the content of light fractions in product gas increases reducing unit volume production capacity
Solution Approach 1:
The patent converts the harmful accumulation of light fractions in the product gas into a beneficial effect by using sulfur-containing compounds to selectively remove carbon from catalysts. This enhances alkylation reaction efficiency, allowing light fractions to be more effectively converted into propylene while reducing their unwanted accumulation in the final product.
3Productivity
If multiple feed distributors are used to improve raw material distribution, then reaction efficiency increases, but device complexity increases
Solution Approach 1:
The patent divides the feed introduction function into multiple segments by using several feed distributors positioned at different locations and heights within the reactor. This segmentation improves raw material distribution and reaction efficiency while managing device complexity through modular design.
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
This approach enhances the reaction rate of ethylene alkylation, reduces the content of light fractions in the product gas, and increases the unit volume production capacity of the reactor, resulting in a higher yield of propylene and C4 hydrocarbons with improved process economics.
Implementation Method 1
a fluidized-bed regenerator, wherein a regeneration medium reacts with the spent catalyst to perform oxidation
Implementation Method 2
a fast fluidized-bed reactor, wherein oxygen-containing compound and catalyst are fed into a reaction zone to perform reaction
Data Source
Figure 1
AI summary
The present invention refers to a fast fluidized-bed reactor, device and method for preparing propylene and C4 hydrocarbons from oxygen-containing compounds. The device comprises the fast fluidized-bed reactor and a fluidized-bed regenerator for regenerating a catalyst. The method includes: a) feeding a raw material containing the oxygen-containing compounds from n reactor feed distributors to a dense phase zone of the fast fluidized-bed reactor, and contacting the raw material with a catalyst, to generate a stream containing target product and a spent catalyst containing carbon; b) sending the stream discharged from the fast fluidized-bed reactor containing target product into a product separation system, obtaining propylene, C4 hydrocarbons, light fractions and the like after separation, returning 70 wt.% or more of the light fractions to the dense phase zone of the fast fluidized-bed reactor from the reactor feed distributor at the bottom-most of the fast fluidized-bed reactor, and reacting ethylene and the oxygen-containing compounds to perform an alkylation reaction in presence of the catalyst, to produce products of propylene and the like. 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.