MTO Propylene Production via Ethylene Oligomerization and Cracking
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Solution Overview
Problem
Current processes for producing propylene from oxygenate feeds, such as the methanol-to-olefin (MTO) process, face challenges in achieving high propylene production ratios and are costly due to the need for additional infrastructure and capital expenditures to handle by-products like ethylene, which is difficult to transport and convert effectively.
Innovation Solution
Integrating ethylene oligomerization and cracking reactors into the MTO process using silicoaluminophosphate (SAPO) catalysts to convert oxygenate feeds into propylene, ethylene, and butylene, followed by separation and further processing to maximize propylene recovery, including the conversion of C4+ streams into additional propylene and high-value products like butadiene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MTO process is used to produce propylene, then propylene can be obtained, but the propylene to ethylene ratio is limited (best 1.5:1 with SAPO-34, 2:1 with SAPO-18) and significant C4+ byproducts are generated
Solution Approach 1:
The patent converts the harmful C4+ byproducts from MTO process into beneficial propylene through oligomerization and cracking operations. The C4+ stream is oligomerized to form C8+ compounds, which are then cracked to produce additional propylene, effectively turning waste material into valuable product and improving overall propylene yield.
Solution Approach 2:
The patent implements continuous oligomerization of C4+ streams and continuous cracking of oligomerized products to maintain steady propylene production. This continuous process ensures that the conversion of C4+ byproducts to propylene occurs without interruption, maximizing productivity.
2Quantity of substance
If ethylene is produced as byproduct in MTO process, then material balance is maintained, but additional capital expenditure is required for ethylene handling infrastructure and transportation
Solution Approach 1:
The patent converts the problematic ethylene byproduct into a valuable intermediate for propylene production. By oligomerizing ethylene to form higher olefins and then cracking these oligomers, the process transforms ethylene from a disposal burden into a feedstock for additional propylene generation, eliminating the need for separate ethylene handling infrastructure.
Solution Approach 2:
The patent makes the ethylene byproduct serve multiple functions: first as a product of MTO reaction, then as a feedstock for oligomerization, and finally as a precursor for additional propylene through cracking. This multi-functional use of ethylene eliminates the need for separate disposal or handling systems.
3Productivity
If olefin cracking is integrated with MTO process, then propylene production increases (P/E ratio reaches 2.0-3.0:1), but process complexity and operating costs increase
Solution Approach 1:
The patent merges the olefin cracking process with the MTO process by integrating the cracking reactor directly into the MTO product stream workflow. The C4+ stream from MTO is fed directly to the oligomerization reactor, and the oligomerized product is fed to the cracking reactor, creating a unified process system that reduces overall complexity compared to separate processes.
Solution Approach 2:
The patent segments the complex conversion process into distinct functional units: MTO reaction, C4+ separation, oligomerization, and cracking. This segmentation allows each unit to be optimized independently while maintaining overall process efficiency and making the complex process more manageable and controllable.
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 integrated approach significantly increases propylene production selectivity and reduces capital and operating costs by effectively utilizing by-products, achieving up to 85% overall selectivity to propylene and allowing for the production of high-value secondary products.
Implementation Method 1
contact the oxygenate feed with a catalyst comprising a silicoaluminophosphate (SAPO) to provide an effluent stream comprising light olefins
Implementation Method 2
reacting the ethylene stream in an ethylene dimerization or oligomerization reactor in presence of a dimerization or oligomerization catalyst
Implementation Method 3
cracking the C4+ stream and the first process stream in a cracking reactor under cracking conditions to provide a cracked stream comprising additional amounts of ethylene and propylene
Data Source
AI summary
Processes and apparatuses for the production of propylene are provided. In an embodiment, a process is provided for production of propylene from an oxygenate feed comprising passing the oxygenate feed to an oxygenate-to-olefin reactor to contact the oxygenate feed with a catalyst to provide an effluent stream comprising olefins comprising ethylene, propylene and butylene. The effluent stream is separated in a product separation zone to generate a propylene product stream, an ethylene stream and a C4+ stream. The ethylene stream is reacted in an ethylene dimerization or oligomerization reactor in presence of a dimerization or oligomerization catalyst to provide a first process stream. The C4+ stream and the first process stream are cracked in a cracking reactor under cracking conditions to provide a cracked stream comprising additional amounts of ethylene and propylene. Finally, the cracked stream is passed to the product separation zone to recover additional amounts of propylene.