Methyl Halide Conversion Catalyst with 8-Membered Ring Pores
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Solution Overview
Problem
Current processes for converting methyl halides into ethylene and propylene face challenges such as low selectivity, high formation of by-products like aromatics and coke, and catalyst deactivation, which reduces the efficiency and stability of the conversion process.
Innovation Solution
A process involving a first catalyst composition with molecular sieves having a Si/Al atomic ratio of 2 to 18 and specific pore structures, used in conjunction with a cracking catalyst, operates at temperatures below 400°C to achieve high selectivity and stability in converting methyl halides to ethylene and propylene, minimizing the formation of aromatics and coke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalysts (HZMS-5, MgZMS-5, SSZ-75, SAPO-34, chabazite) are used for converting methyl halides into olefins, then conversion and selectivity to ethylene and propylene can be achieved, but catalyst deactivation occurs rapidly (within 1.5-3 hours on stream) and significant amounts of by-products (aromatics, C4-C5 olefins, coke) are formed
Solution Approach 1:
The patent modifies the molecular sieve structure by controlling the Si/Al ratio (2-18) and pore size (8-membered ring or less) to change the catalytic properties. This structural parameter change allows the catalyst to maintain stability for at least 24 hours on stream while reducing by-product formation to less than 10%, resolving the contradiction between catalyst reliability and harmful by-product generation
Solution Approach 2:
The patent creates specific local environments within the catalyst by designing molecular sieves with specific pore sizes (8-membered ring or less) and Si/Al ratios. This local structural quality control allows selective promotion of desired reactions while suppressing side reactions that lead to coke and aromatic formation, thereby improving catalyst stability without sacrificing selectivity
2Productivity
If reaction temperature is increased to improve conversion rate, then productivity increases, but selectivity to ethylene and propylene decreases and more by-products are formed
Solution Approach 1:
The patent changes the catalyst's physical parameters (pore size, Si/Al ratio) to achieve high conversion rates at lower temperatures. The molecular sieve structure with 8-membered ring pores and controlled Si/Al ratio enables efficient mass transfer and selective catalysis, allowing the system to maintain high productivity while preserving selectivity to ethylene and propylene without forming significant by-products
3Manufacturing precision
If molecular sieves with small pore diameter (CHA framework, SSZ-13) are used to inhibit larger molecules, then selectivity to light olefins improves, but catalyst deactivation occurs very rapidly (less than 3 hours on stream)
Solution Approach 1:
The patent creates a composite catalyst system combining molecular sieves with specific pore structures (8-membered ring or less) and controlled Si/Al ratios. This composite structure maintains the shape-selective properties for light olefin production while the optimized composition prevents rapid deactivation, extending catalyst lifetime to at least 24 hours on stream while maintaining high selectivity
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 achieves high selectivity to ethylene and propylene with improved catalyst stability, maintaining efficiency for at least 24 hours and reducing aromatics formation to less than 10%, thereby enhancing the overall yield and process efficiency.
Implementation Method 1
providing a first catalyst composition and a second catalyst composition, said second catalyst composition comprising a cracking catalyst; contacting said feedstream with said first catalyst composition in a first reaction zone under first reaction conditions
Implementation Method 2
one or more molecular sieves with a Si/Al atomic ratio ranging from 2 to 18, wherein said one or more molecular sieves comprise a plurality of pores with a shape of an 8-membered ring or less
Implementation Method 3
subjecting at least a part of said first product stream to an Olefin Catalytic Cracking (OCC) with said second catalyst composition in a second reaction zone under second reaction conditions
Data Source
AI summary
The present disclosure concerns a process for converting methyl halides to ethylene and propylene, said process comprising the steps of (a) providing a feedstream comprising methyl halides; (b) providing a first and second catalyst composition, said second catalyst composition comprising a cracking catalyst; (c) contacting said feedstream with said first catalyst composition in a first reaction zone under first reaction conditions to provide a first product stream; and (d) subjecting at least a part of said first product stream to an Olefin Catalytic Cracking with said second catalyst composition in a second reaction zone under second reaction conditions to provide a second product steam. The process is remarkable in that said step (c) is performed under 400° C., and in that said first catalyst composition comprises molecular sieves with a Si/Al atomic between 2 and 18 and with a plurality of pores with a shape of an 8-membered ring or less.