Vacuum Pyrolysis of Plastic Polyolefins for Lubricant Base Stocks
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Solution Overview
Problem
There is a need for alternative pyrolysis processes that can efficiently convert waste plastic into high-yield C20 to C60 wax, which can be subsequently converted into a lubricant base stock, as existing methods often require catalysts, carrier gases, and fluidized-bed reactors that are energy-intensive and require frequent maintenance.
Innovation Solution
A vacuum pyrolysis process with multistage downstream condensation is employed to selectively decompose plastic polymers, minimizing secondary cracking reactions and producing a C20 to C60 wax that is then converted into a lubricant base stock through catalytic hydroisomerization, eliminating the need for catalysts and carrier gases and reducing energy demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluidized-bed pyrolysis is used to convert waste plastic into wax, then rapid heat transfer and good control are achieved, but secondary cracking reactions increase and energy consumption rises
Solution Approach 1:
The patent employs vacuum pyrolysis to create an inert atmosphere in the pyrolysis reactor, eliminating oxygen and preventing unwanted oxidation reactions. This inert environment suppresses secondary cracking reactions while maintaining efficient wax production from waste plastic polymers.
Solution Approach 2:
The patent implements a pre-heating zone before the main pyrolysis reactor where waste plastic is pre-heated to a temperature below the pyrolysis temperature. This preliminary action prepares the feedstock for efficient pyrolysis while controlling the thermal history to minimize secondary cracking reactions in the main reactor.
2Reliability
If catalysts and carrier gases are used in pyrolysis processes, then reaction control is improved, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent removes catalysts and carrier gases from the pyrolysis process, using pure vacuum pyrolysis instead. This extraction of complex components simplifies the overall process while maintaining reliable reaction control through precise temperature and vacuum management.
Solution Approach 2:
The vacuum system itself serves as the control mechanism for the pyrolysis process, eliminating the need for separate catalyst management and carrier gas handling systems. The vacuum environment naturally controls the reaction atmosphere without requiring additional complex equipment.
3Productivity
If high temperatures are used in pyrolysis to maximize wax yield, then decomposition efficiency is improved, but energy consumption increases
Solution Approach 1:
The pre-heating zone prepares the waste plastic feedstock by heating it to a temperature below the main pyrolysis temperature before it enters the high-temperature pyrolysis reactor. This preliminary thermal preparation reduces the energy burden on the main reactor while ensuring efficient wax decomposition and yield.
Solution Approach 2:
The patent optimizes the pyrolysis temperature range and vacuum pressure parameters to maximize wax yield while minimizing energy consumption. By carefully controlling these parameters, the process achieves high decomposition efficiency without excessive energy input.
4Manufacturing precision
If vacuum pyrolysis is used to minimize secondary cracking, then wax quality is improved, but equipment complexity increases
Solution Approach 1:
The vacuum pyrolysis reactor creates an inert atmosphere that prevents secondary cracking reactions and oxidation, ensuring high wax quality with controlled composition. The vacuum system integrates multiple functions including atmosphere control, vapor removal, and pressure management in a single coordinated system.
Solution Approach 2:
The pyrolysis system is divided into distinct zones including a pre-heating zone and a main pyrolysis reactor zone. This segmentation allows each zone to be optimized for its specific function while working together to produce high-quality wax with minimal secondary cracking.
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 effectively produces a desirable C20 to C60 wax with high yield, reducing secondary cracking and energy consumption, and allows for the production of a lubricant base stock that is substantially free of heteroatoms, simplifying downstream processing and improving lubricant properties.
Implementation Method 1
heating the plastic polyolefin polymer at sub-atmospheric pressure, wherein the temperature in the thermal reaction zone of the reactor is from 500 °C to 750 °C, to induce thermal decomposition of the plastic polyolefin polymer
Implementation Method 2
induce thermal decomposition of the plastic polyolefin polymer and to form a thermal decomposition product effluent which comprises a major portion by weight of a C 20 to C 60 wax fraction
Implementation Method 3
condensing a vapour component of the thermal decomposition product effluent from the vacuum pyrolysis reactor in a multistage condensation comprising a plurality of condensation stages connected in series
Implementation Method 4
subjecting the C 20 to C 60 wax fraction of the thermal decomposition product to catalytic hydroisomerization in a hydroisomerization reactor in the presence of hydrogen to form the lubricant base stock
Implementation Method 5
catalytic hydroisomerization in a hydroisomerization reactor in the presence of hydrogen
Data Source
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AI summary
The present invention relates to a process for the preparation of a lubricant base stock from the thermal decomposition of plastic polymer. The present invention provides a process for preparing a lubricant base stock from the thermal decomposition of plastic polyolefin polymer, the method comprising the steps of: i) introducing plastic polyolefin polymer into a thermal reaction zone of a vacuum pyrolysis reactor; ii) heating the plastic polyolefin polymer at sub-atmospheric pressure, wherein the temperature in the thermal reaction zone of the reactor is from 500 °C to 750 °C, to induce thermal decomposition of the plastic polyolefin polymer and to form a thermal decomposition product effluent which comprises a major portion by weight of a C20 to C60 wax fraction; iii) condensing a vapour component of the thermal decomposition product effluent from the vacuum pyrolysis reactor in a multistage condensation comprising a plurality of condensation stages connected in series; and iv) subjecting the C20 to C60 wax fraction of the thermal decomposition product to catalytic hydroisomerization in a hydroisomerization reactor in the presence of hydrogen to form the lubricant base stock.