Two-Step Pyrolysis for Crosslinked Rubber Decomposition
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Solution Overview
Problem
Existing methods for decomposing crosslinked rubber, such as pyrolysis and microbial decomposition, result in low yields of monomers, with pyrolysis causing gasification and aromatization, and microbial methods being slow and inefficient.
Innovation Solution
A two-step pyrolysis method is employed, where crosslinked rubber is first pyrolyzed at temperatures between 150°C and 400°C to suppress gasification and aromatization, and then the decomposition products are pyrolyzed under an inert gas atmosphere and in the presence of a catalyst at temperatures between 300°C and 950°C to enhance monomer recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If crosslinked rubber is pyrolyzed at high temperature, then decomposition occurs, but gasification and aromatization result in lower yields of monomers
Solution Approach 1:
The patent divides the pyrolysis process into two distinct temperature stages: a first pyrolysis stage at lower temperature (150-400°C) to break crosslinks and form oligomers, and a second pyrolysis stage at higher temperature (300-950°C) to decompose oligomers to monomers. This segmentation prevents premature gasification and aromatization by controlling the temperature progression, thereby improving monomer yield.
Solution Approach 2:
The first pyrolysis step at lower temperature serves as a preliminary action that breaks the crosslinked structure and forms oligomers before the second high-temperature pyrolysis step. This preliminary decomposition prevents direct gasification and aromatization that would occur if high temperature was applied immediately, thus preserving monomer yield.
2Productivity
If microorganisms are used to decompose crosslinked rubber, then decomposition occurs, but a long time is required and monomer yield is low
Solution Approach 1:
The patent replaces the biological decomposition system (microorganisms) with a thermal decomposition system (pyrolysis). By using controlled heating at specific temperature ranges, the process achieves much faster decomposition rates compared to microbial methods, while also improving monomer yield through optimized thermal conditions.
3Productivity
If crosslinked rubber is pyrolyzed at high temperature, then decomposition occurs, but gasification and aromatization reduce monomer yield
Solution Approach 1:
The patent changes the temperature parameter dynamically during the pyrolysis process. By implementing a two-stage temperature profile (first stage: 150-400°C, second stage: 300-950°C), the process optimizes the thermal conditions to maximize monomer formation while minimizing harmful gasification and aromatization reactions that occur at excessively high temperatures.
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 method significantly improves the yield of monomers from crosslinked rubber, making it more economically and environmentally viable for material reuse.
Implementation Method 1
a first decomposition step of pyrolyzing a crosslinked rubber containing a diene rubber at a temperature of 150° C. or more and 400° C. or less
Implementation Method 2
a second decomposition step of pyrolyzing a decomposition product obtained by the first decomposition step under an inert gas atmosphere and in the presence of a catalyst at a temperature of 300° C. or more and 950° C. or less
Implementation Method 3
a second decomposition step of pyrolyzing a decomposition product obtained by the first decomposition step under an inert gas atmosphere and in the presence of a catalyst
Data Source
AI summary
The present disclosure addresses the problem of providing a method for decomposing a crosslinked rubber that can improve monomer yield. The solution is a method of decomposing a crosslinked rubber that includes: a first decomposition step of pyrolyzing a crosslinked rubber containing a diene rubber at a temperature of 150° C. or more and 400° C. or less, and a second decomposition step of pyrolyzing a decomposition product obtained by the first decomposition step under an inert gas atmosphere and in the presence of a catalyst at a temperature of 300° C. or more and 950° C. or less. Preferably 80 mass % or more of the diene rubber in the crosslinked rubber is decomposed to diene oligomers having a weight-average molecular weight of 100 to 50,000 via the first decomposition step.