Fluidized-Bed Reactor for Light Olefins via Segmented Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current processes for producing light olefins from methanol and/or dimethyl ether, such as those using aluminum phosphate or silicoaluminophosphate molecular sieves, face challenges in achieving high yield and selectivity for ethylene and propylene due to side reactions at higher temperatures and catalyst residence times.
Innovation Solution
A fluidized-bed reactor process is employed, where methanol or dimethyl ether is introduced at the bottom and reacts in a dense phase zone with a catalyst, followed by the introduction of a terminating agent in the transition zone or gas-solid separating zone to enhance product separation and reduce side reactions, utilizing catalysts like SAPO-34, ZSM-5, and ZSM-35, and incorporating a whirl-flow quickly-separating unit and cyclone for efficient gas-solid separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher reaction temperature is used to increase conversion rate, then productivity is improved, but selectivity to ethylene and propylene deteriorates due to side reactions
Solution Approach 1:
The reactor is divided into distinct functional zones: a dense phase reaction zone for high-temperature conversion and a separate gas-solid separation zone for product separation. This segmentation allows the reaction to proceed at high temperature for productivity while the separation zone prevents side reactions, maintaining selectivity.
Solution Approach 2:
A gas-solid separating zone with cyclone separators acts as an intermediary between the reaction zone and product output. This intermediary structure separates catalyst particles from gaseous products, preventing catalyst-induced side reactions in the separation zone and maintaining product selectivity while allowing high conversion rates.
2Productivity
If longer catalyst residence time is used to increase conversion, then productivity is improved, but side reactions increase reducing selectivity
Solution Approach 1:
The gas-solid separation zone with cyclone separators rapidly separates products from catalyst, rushing the gaseous products through the separation zone before they can undergo side reactions. This quick separation prevents harmful side reactions while maintaining high conversion rates through adequate catalyst contact time in the reaction zone.
Solution Approach 2:
By segmenting the reactor into reaction and separation zones, the patent allows long catalyst residence time in the reaction zone for high conversion while preventing side reactions in the separation zone through rapid gas-solid separation, thus resolving the contradiction between productivity and harmful side reactions.
3Productivity
If catalyst activity is increased to improve conversion, then productivity is improved, but temperature control becomes difficult leading to reduced selectivity
Solution Approach 1:
The reactor is segmented into a dense phase reaction zone where high-temperature conversion occurs and a separate gas-solid separation zone. This segmentation allows high catalyst activity in the reaction zone for productivity while the separation zone acts as a thermal buffer, preventing temperature runaway and maintaining selectivity through rapid product removal.
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 process significantly enhances the yield of ethylene and propylene by reducing side reactions and improving selectivity, with yields ranging from 44.7% to 49.3% ethylene and 29.1% to 39.9% propylene under optimized conditions.
Implementation Method 1
reacting the feed in a dense phase zone and a transition zone of the fluidized-bed reactor by contacting it with a catalyst, to form an effluent I comprising unreacted feed, reaction products and entrained solid particulate catalyst
Implementation Method 2
introducing a feed comprising methanol and/or dimethyl ether into a fluidized-bed reactor from its bottom, and reacting the feed in a dense phase zone and a transition zone of the fluidized-bed reactor
Implementation Method 3
passing the effluent II into the gas-solid separating zone in upper portion of the fluidized-bed reactor, where gas-solid separation is accomplished
Data Source
AI summary
A process for producing light olefins from methanol and/or dimethyl ether is disclosed. It comprises: (a) introducing a feed comprising methanol and/or dimethyl ether into a fluidized-bed reactor from its bottom, and contacting the feed in a dense phase zone and a transition zone of the fluidized-bed reactor with a catalyst, to form an effluent I comprising unreacted feed, reaction products and entrained solid particulate catalyst; (b) introducing a terminating agent consisting of water, alcohol, ether, hydrocarbons, and aromatic at upper portion of the transition zone and/or lower portion of a gas-solid separating zone of the fluidized-bed reactor into the effluent I, to give an effluent II; and (c) passing the effluent II into the gas-solid separating zone in upper portion of the fluidized-bed reactor, where gas-solid separation is accomplished to give a gaseous product stream and solid catalyst.