Mixed Plastic Pyrolysis Oil Aromatization and BTX Recovery
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Solution Overview
Problem
The challenge lies in effectively utilizing pyrolysis products from plastic waste due to the presence of residues from additives, which are toxic and hinder the conversion of light naphtha into higher-value gasoline blending components, given the inertness of carbon-carbon and carbon-hydrogen bonds, resulting in unfavorable thermodynamics and low selectivity.
Innovation Solution
A method involving pyrolysis of mixed plastics to produce a stream of plastic pyrolysis oil, followed by aromatization using an aromatization unit with a catalyst to generate an aromatics-rich stream, which is then separated into BTX, gasoline blending, and aromatic fractions, utilizing a fractionator to process the pyrolysis oil into suitable distillate and residual fractions for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If pyrolysis is conducted on mixed plastics to produce pyrolysis oil, then plastic waste is converted into valuable hydrocarbon streams, but toxic residues from additives remain in the pyrolysis products
Solution Approach 1:
The patent extracts and removes toxic residues from the pyrolysis oil through a series of treatment steps including washing with aqueous solutions (caustic soda, sulfuric acid), filtration, and distillation. This separation process isolates the harmful additive residues from the valuable hydrocarbon streams, allowing the pyrolysis oil to be safely processed further into gasoline blending components.
2Productivity
If light naphtha is processed into gasoline blending components, then value-added products are produced, but the inertness of carbon-carbon and carbon-hydrogen bonds results in unfavorable thermodynamics and low selectivity
Solution Approach 1:
The patent employs parameter changes by conducting aromatization reactions at controlled temperatures (400-600°C) and using specific catalysts (zeolites, metal oxides) to alter the reaction conditions. These parameter changes enable the breaking of inert carbon-carbon and carbon-hydrogen bonds under favorable thermodynamic conditions, converting light naphtha into aromatics with high selectivity and yield suitable for gasoline blending.
Solution Approach 2:
The patent introduces catalysts as intermediaries to facilitate the conversion of light naphtha into aromatics. The catalysts (such as zeolites, alumina, silica) act as mediators that lower the activation energy required to break inert bonds, improving reaction selectivity and thermodynamics while enabling the production of high-value gasoline blending components.
3Productivity
If aromatics are produced from pyrolysis oil through aromatization, then valuable aromatic hydrocarbons are generated, but complex separation and purification processes are required
Solution Approach 1:
The patent segments the complex separation process into distinct stages: initial distillation to separate light ends, followed by extraction with solvents to isolate aromatics from non-aromatics, and final purification steps. This segmentation of the separation process into manageable stages reduces overall complexity while maintaining high aromatic recovery and purity.
Solution Approach 2:
The patent utilizes hydraulic and pneumatic principles in the separation process, including liquid-liquid extraction where aromatics are separated from the pyrolysis oil using immiscible solvents. The density differences and phase separation enabled by these principles allow for efficient aromatics recovery without requiring overly complex equipment.
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 the conversion of pyrolysis products into valuable aromatics and gasoline blending components, overcoming the limitations of inert bonds and toxic residues, thereby enhancing the yield and quality of gasoline production.
Implementation Method 1
feeding the plastic pyrolysis oil to an aromatization unit having an aromatization reactor with an aromatization catalyst disposed therein to generate an aromatics rich stream
Implementation Method 2
passing the aromatics rich stream to an aromatics recovery complex to separate the aromatic rich stream into a BTX fraction, a gasoline blending fraction, a gas fraction including hydrogen and C1-C4 hydrocarbons, and an aromatic bottoms fraction
Implementation Method 3
conducting pyrolysis of a plastic feedstock to produce a stream of plastic pyrolysis oil
Data Source
AI summary
Method of producing pyrolysis products from a mixed plastics stream along with an associated system for processing mixed plastics. The method includes conducting pyrolysis of a plastic feedstock to produce a stream of plastic pyrolysis oil; feeding the plastic pyrolysis oil to an aromatization unit having an aromatization reactor with an aromatization catalyst disposed therein to generate an aromatics rich stream; and passing the aromatics rich stream to an aromatic recovery complex to separate the aromatics rich stream into a BTX fraction, a gasoline blending fraction, a gas fraction comprising hydrogen and C1-C4 hydrocarbons, and an aromatic bottoms fraction comprising hydrocarbons boiling above 180° C., where the BTX fraction consists of benzene, toluene and mixed xylenes and the gasoline blending fraction comprises aliphatic hydrocarbons with a boiling range from C5 hydrocarbon up to the aromatic bottoms fraction.