Multi-Stage Fluidized Bed Reactor for Light Olefin Yield
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Solution Overview
Problem
Current methods for producing light olefins, such as ethylene and propylene, face challenges with low yields due to uneven carbon deposition on catalysts and fluctuating reaction temperatures, leading to inefficient conversion processes.
Innovation Solution
A method involving a dense phase fluidized bed reactor with multiple secondary pre-carbon deposition and reaction zones, where hydrocarbons with four or more carbons are pre-deposited on catalysts, and then reacted with oxygen-containing compounds, followed by regeneration, to optimize carbon content uniformity and increase light olefin yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MTO process is used with SAPO-34 molecular sieve catalyst, then high selectivity for light olefins can be achieved after induction period, but catalyst activity is lost due to carbon deposition and requires prolonged time to reach optimal performance
Solution Approach 1:
The patent applies preliminary action by pre-depositing carbon on the catalyst before the main MTO reaction. This is achieved by introducing a hydrocarbon feedstock containing 2-4 carbon atoms in a first reaction zone to form a pre-carbon deposited catalyst, which then eliminates the induction period in the second reaction zone where methanol conversion occurs.
2Productivity
If multiple reaction zones are added to increase residence time and convert unreacted methanol, then light olefin yield can be increased, but conversion efficiency of hydrocarbons remains relatively low due to catalyst deactivation
Solution Approach 1:
The patent segments the reaction process into distinct functional zones: a first reaction zone for pre-carbon deposition using hydrocarbon feedstock, and a second reaction zone for methanol-to-olefins conversion. This segmentation allows each zone to perform its specific function optimally, with the pre-carbon deposited catalyst maintaining high activity in the second zone.
Solution Approach 2:
The first reaction zone performs preliminary carbon deposition action on the catalyst using hydrocarbon feedstock, creating a pre-carbon deposited catalyst that maintains high activity for the subsequent methanol conversion in the second reaction zone, thereby improving overall conversion efficiency.
3Duration of action of stationary object
If catalyst circulation is implemented to maintain activity, then continuous operation is possible, but carbon deposition still occurs and requires regeneration cycles
Solution Approach 1:
The patent applies preliminary action by pre-depositing carbon on the catalyst in the first reaction zone before the catalyst enters the second reaction zone for methanol conversion. This pre-carbon deposition prevents further carbon accumulation during the main reaction, extending catalyst activity duration and reducing regeneration frequency.
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 yield of light olefins by controlling carbon deposition and reaction conditions, resulting in improved selectivity and economic efficiency, with carbon-based yields reaching up to 93.2% as demonstrated in examples.
Implementation Method 1
a hydrocarbon with four or more carbons is introduced from k feeding branch lines of pre-carbon deposition zone in parallel into k secondary pre-carbon deposition zones in a dense phase fluidized bed reactor, and is brought into contact with a completely regenerated and/or fresh catalyst, so as to be converted into a light olefin product-containing stream
Implementation Method 2
the gas phase product stream and the entrained catalyst are passed into a cyclone separator
Implementation Method 3
the spent catalyst is passed into a regenerator to remove therefrom the deposited carbon
Data Source
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AI summary
The present invention relates to a method for improving the light olefin yield in the process of preparation of a light olefin using an oxygen-containing compound. More specifically, the present invention provides a method for preparing a light olefin using an oxygen-containing compound, in which, a multi-stage dense phase fluidized bed comprising k secondary pre-carbon deposition zones (k≥1) and n secondary reaction zones (n≥1) is used as a reactor, and a multi-stage dense phase fluidized bed regenerator comprising m secondary regeneration zones (m≥2) is used as a main equipment. By the method of re-refining the hydrocarbons with four or more carbons obtained in the separation section, or adding naphtha, gasoline, condensate oil, light diesel oil, hydrogenation tail oil or kerosene in the reaction zone, the invention primarily solves the problems in the prior art of the uniformity of carbon deposition amount and the carbon content of the catalyst being difficult to control, and the light olefin yield being low.