Negative Pressure Catalytic Cracking for Lower Olefins
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Solution Overview
Problem
Current processes for producing lower olefins through catalytic cracking of C4 or higher olefins face challenges such as high reaction pressure, high temperature, low yield and selectivity, poor catalyst stability, and limited suitable feedstocks, resulting in non-ideal yields and short catalyst life.
Innovation Solution
A process involving catalytic cracking of an olefins-enriched mixture using a crystalline aluminosilicate catalyst under negative pressure and moderate temperature, with a SiO2/Al2O3 molar ratio of at least 10, to produce lower olefins, where the reaction pressure is maintained between −0.1 MPa and <0 MPa, and the temperature is between 400°C and 580°C, utilizing ZSM-type molecular sieves to enhance catalyst stability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic cracking is performed under conventional positive pressure conditions, then the reaction can proceed with standard equipment, but the yield and selectivity of lower olefins are reduced due to increased hydrogen transfer reactions and coke deposition
Solution Approach 1:
The patent applies parameter changes by operating the catalytic cracking process under negative pressure conditions instead of conventional positive pressure. This pressure parameter change suppresses hydrogen transfer reactions and reduces coke deposition on the catalyst, thereby improving lower olefin yield and selectivity while extending catalyst life. The negative pressure environment fundamentally alters the reaction dynamics to favor desired products.
2Productivity
If high temperature is used to increase reaction rate, then productivity improves, but catalyst stability and life deteriorate due to accelerated deactivation
Solution Approach 1:
The patent employs parameter changes by operating at moderate temperatures (400-580°C) combined with negative pressure conditions. This combination maintains high reaction rates while significantly reducing catalyst deactivation. The negative pressure environment protects the catalyst from thermal stress and chemical degradation, extending its operational life without sacrificing productivity.
3Ease of operation
If a single reactor configuration is used, then the process is simple to operate, but it is impossible to maintain desirable catalyst stability and achieve high target product yield simultaneously
Solution Approach 1:
The patent applies segmentation by dividing the catalytic cracking process into multiple reactors arranged in series or parallel configurations. This allows different reactors to perform specialized functions - some optimized for conversion while others maintain catalyst stability. The multi-reactor system achieves both high lower olefin yield and sustained catalyst activity, overcoming the limitations of single-reactor designs.
4Ease of manufacture
If conventional catalysts are used under high pressure conditions, then the process operates with standard materials, but the selectivity for lower olefins is reduced
Solution Approach 1:
The patent applies parameter changes by operating with conventional catalyst materials under negative pressure conditions. This pressure parameter modification enhances the selectivity for lower olefins without requiring exotic or specially engineered catalysts. The negative pressure environment inherently favors the desired reaction pathway, allowing standard catalysts to achieve superior 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 process achieves higher yields and selectivity of lower olefins, prolongs catalyst activity and stability, and allows for the use of various feedstocks, effectively addressing the limitations of existing methods by reducing hydrogen transfer reactions and coke deposition.
Implementation Method 1
a process for producing lower olefins by virtue of catalytic cracking of C4 or higher olefins
Data Source
AI summary
A process for producing lower olefins is disclosed. The technical problem is to overcome the defects presented in the prior art including high reaction pressure, high reaction temperature, low yield and selectivity of lower olefins as the target products, poor stability and short life of catalyst, and limited suitable feedstocks. The disclosed process, which is carried out under the conditions of catalytic cracking olefins and adopts as a feedstock an olefins-enriched mixture containing one or more C4 or higher olefins and optionally an organic oxygenate compound, comprises the steps of: a) letting the feedstock contact with a crystalline aluminosilicate catalyst having a SiO2/Al2O3 molar ratio of at least 10, to thereby produce a reaction effluent containing lower olefins; and b) separating lower olefins from the reaction effluent; wherein, the reaction pressure is from −0.1 MPa to <0 MPa.