Modified Zeolite Catalyst for Mixed Plastics Recycling
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Solution Overview
Problem
Current methods for recycling plastics, such as catalytic hydrocracking and pyrolysis, face challenges including high temperatures, long reaction times, variability in product quality, and issues with polyvinyl halides and PET, which require costly and time-consuming pre-sorting and can lead to reactor damage, making them non-viable for continuous operation.
Innovation Solution
A modified zeolite catalyst process involving a two-stage ion-exchange and steam calcination method to reduce sodium oxide content and unit cell size, followed by transition metal ion-exchange, results in a catalyst with improved stability and reduced unit cell size, enabling efficient recycling of mixed plastics waste into fuels like gasoline, diesel, and LPG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional zeolite catalysts are used in hydrocracking and pyrolysis of waste plastics, then the process can convert plastics into fuels, but the catalyst has limited lifetime and becomes spent after a period of use due to reduced crystallinity
Solution Approach 1:
The patent applies parameter changes by modifying the zeolite catalyst's physical and chemical properties through controlled steaming and ion exchange processes. Specifically, the unit cell size is reduced from typical values to 24.2-24.5 Å, and sodium content is reduced to ≤0.1 wt%, which fundamentally alters the catalyst's stability and resistance to deactivation during prolonged use.
Solution Approach 2:
The patent implements preliminary action by pre-modifying the zeolite catalyst structure before it enters the reactor. The steaming and ion exchange treatments are performed in advance to create a more stable catalyst framework that resists degradation during the hydrocracking process, preventing the catalyst from becoming spent prematurely.
2Productivity
If high temperatures (400 to 700°C) are used for hydrocracking and pyrolysis of waste plastics, then the conversion process can proceed, but the reaction times are long and energy consumption is high
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (400-700°C) to a lower range of 200-400°C. This parameter change is enabled by the modified zeolite catalyst with reduced unit cell size and sodium content, which provides higher catalytic activity at lower temperatures, thereby reducing energy consumption while maintaining productive conversion rates.
3Adaptability or versatility
If mixed waste plastics including PVC and PET are processed, then recycling efficiency increases, but halogenated organics and hydrogen halides are produced causing reactor damage and requiring pre-sorting
Solution Approach 1:
The patent converts the harmful effect of halogenated compounds into a benefit by using the modified zeolite catalyst to promote dehalogenation reactions. The catalyst's unique structure with reduced unit cell size and low sodium content facilitates the removal of halogen atoms from PVC, converting potentially damaging halogenated organics and hydrogen halides into less harmful products, thereby protecting the reactor while accepting mixed plastics.
4Productivity
If the unit cell size and sodium oxide content of zeolite catalysts are reduced to improve stability, then catalyst lifetime increases, but the catalyst may become deactivated if reduced too much
Solution Approach 1:
The patent optimizes the parameters of unit cell size and sodium oxide content by reducing them to specific ranges (unit cell size: 24.2-24.5 Å, sodium content: ≤0.1 wt%) rather than eliminating them completely. This controlled parameter change achieves maximum stability and lifetime while preserving sufficient catalytic activity, avoiding the deactivation that would occur with excessive reduction.
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
The modified zeolite catalysts achieve stable operation at lower temperatures, reduce product variability, and extend catalyst lifetime, facilitating continuous recycling of mixed plastics waste into high-quality fuel products.
Implementation Method 1
The zeolite is then subjected to a two-stage ion-exchange process
Implementation Method 2
The ion-exchanged zeolite is then steam calcined
Implementation Method 3
catalytic hydrocracking and catalytic and non-catalytic pyrolysis
Data Source
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AI summary
The present invention relates to a method for the recycling of plastics materials, in particular waste plastics materials, into chemical feed stocks and hydrocarbon fractions. The present invention also relates to novel zeolite based catalysts used in such methods. The present invention also relates to methods of manufacturing such zeolite based catalysts. Plastics waste is traditionally disposed of by land-fill, incineration or recycling by re- processing the waste into raw material for reuse. Each of these disposal methods has its disadvantages. The drawbacks of land-fill are self apparent. Although incineration may include energy recovery, there still remains the obvious problem of CO2 emission and the emission of other toxic pollutants. Additionally, recycling the plastics requires sorting of the plastics waste because certain types of plastics materials are not recyclable, and mixtures of plastics can be problematic. The present invention provides an improved method for the recycling of waste plastics including mixed waste streams.