Zeolite Catalyst for Ethylene and Propylene Production
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Solution Overview
Problem
Existing methods for catalytically converting hydrocarbon starting materials to produce ethylene and propylene using zeolite catalysts result in low yields of these products due to dimerization and decomposition of olefins, requiring complex recycling processes that increase costs and apparatus complexity.
Innovation Solution
A method involving a medium pore diameter zeolite catalyst with silver and no protons, under specific reaction conditions, separates reaction mixtures into hydrogen and hydrocarbons of 1-3 carbon atoms, and hydrocarbons of 4 or more carbon atoms, allowing for the direct recycling of the latter as a hydrocarbon starting material without purification, thereby stabilizing the catalyst and enhancing ethylene and propylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite catalysts are used for catalytic conversion of hydrocarbons to produce ethylene and propylene, then the reaction proceeds, but the yields of ethylene and propylene are low due to dimerization and decomposition of olefins
Solution Approach 1:
The patent changes the chemical composition parameters of the zeolite catalyst, specifically using a low-silicon zeolite with SiO2/Al2O3 molar ratio of 50 or less, and incorporates rare earth metals (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium) at controlled concentrations (0.1-10 wt%). These parameter changes modify the catalyst's acid site distribution and stability, suppressing olefin dimerization and decomposition while enhancing ethylene and propylene production.
Solution Approach 2:
The patent creates a composite catalyst material by combining low-silicon zeolite with rare earth metals. This composite structure leverages the synergistic effects between the zeolite framework and rare earth metal sites, where the rare earth metals modify the acid strength and provide alternative reaction pathways that favor ethylene and propylene formation while minimizing unwanted side reactions.
2Productivity
If complex recycling processes are implemented to recycle olefins of 4 or more carbon atoms, then olefin conversion efficiency improves, but apparatus cost and operating cost increase
Solution Approach 1:
The patent extracts and removes the need for complex recycling apparatus by designing a catalyst that inherently minimizes the formation of olefins requiring recycling. The low-silicon zeolite with rare earth metals suppresses olefin dimerization, reducing the quantity of C4+ olefins that would otherwise need to be separated and recycled, thereby eliminating or simplifying the recycling train.
Solution Approach 2:
The patent converts the potentially harmful side reactions (olefin dimerization and decomposition) into beneficial outcomes by using the rare earth metal-modified zeolite catalyst to selectively promote ethylene and propylene formation pathways. The catalyst transforms what would be waste streams into valuable products, reducing the need for downstream separation and recycling operations.
3Duration of action of stationary object
If conventional zeolite catalysts are used, then catalytic conversion occurs, but catalyst deterioration happens over time
Solution Approach 1:
The patent changes the structural parameters of the zeolite by using a low-silicon composition (SiO2/Al2O3 ≤ 50) and incorporating rare earth metals, which enhance the catalyst's thermal and mechanical stability. The rare earth metals strengthen the zeolite framework and reduce coke formation, thereby extending catalyst life and maintaining reliability over extended operation periods.
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 enables efficient and stable production of ethylene and propylene by simplifying the recycling process, reducing catalyst deterioration, and maintaining high yields over extended periods.
Implementation Method 1
catalytic conversion of hydrocarbon starting materials containing olefins using catalysts containing zeolite
Implementation Method 2
contacting a hydrocarbon starting material containing at least one olefin of 4-12 carbon atoms with a catalyst containing a medium pore diameter zeolite
Data Source
AI summary
A process for efficiently and stably producing ethylene and propylene which comprises bringing a hydrocarbon feedstock comprising at least one C4-12 olefin into contact with a zeolite-containing catalyst to obtain a reaction mixture containing ethylene and propylene, separating the reaction mixture into a fraction comprising ingredients ranging from hydrogen to C3 hydrocarbons and a fraction comprising C4 and higher hydrocarbons, and recycling the C4 and higher hydrocarbons as they are to a reactor.