Molten Salt Oxidative Cracking for Low-Emission Olefin Production
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Solution Overview
Problem
Conventional pyrolysis processes for converting waste plastics into valuable chemicals face challenges with fouling and contaminants, leading to inefficiencies and high carbon dioxide emissions, and require significant external heat input.
Innovation Solution
A process using a molten salt matrix with oxygen in the absence of catalysts to crack carbon-containing feedstocks, enhancing radical reactions and reducing external heat requirements through internal heat generation, while capturing contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional steam cracking is used to produce light olefins from hydrocarbon feedstocks, then high yields of ethylene and propylene can be achieved, but large amounts of CO2 emissions are generated due to the endothermic nature of the process requiring external fuel combustion
Solution Approach 1:
The patent converts the harmful endothermic heat requirement into a beneficial exothermic oxidation process. By introducing oxygen to react with carbon-containing feedstocks in the presence of molten salt, the process generates heat internally through oxidation reactions, eliminating the need for external fuel combustion and thereby reducing CO2 emissions while maintaining high light olefin yields
Solution Approach 2:
The patent changes the fundamental thermal parameter of the cracking process from endothermic to exothermic by introducing oxygen. This parameter change transforms the energy balance, allowing the process to be self-sustaining and reducing external energy input requirements, which directly reduces CO2 emissions associated with fuel combustion
2Productivity
If conventional pyrolysis is used to convert waste plastics into pyrolysis oil, then plastic waste can be converted into valuable chemicals, but fouling from char and contaminants become entrained in liquid products exceeding steam cracker limits
Solution Approach 1:
The patent introduces molten salt as an intermediary medium between the carbon-containing feedstock and the product stream. The molten salt facilitates the oxidation-cracking reaction while preventing direct contact between contaminants and the liquid product, thereby maintaining high purity pyrolysis oil that meets steam cracker feed specifications
Solution Approach 2:
The patent extracts contaminants and char from the reaction system by having them remain entrained in the molten salt phase rather than being carried over into the liquid product stream. This separation mechanism ensures that the pyrolysis oil meets purity requirements for downstream steam cracking processes
3Manufacturing precision
If conventional pyrolysis operates at temperatures around 500°C to avoid side reactions, then aromatization can be minimized, but the process requires significant external heat input and suffers from fouling issues
Solution Approach 1:
The patent makes the process self-sustaining by introducing oxygen that reacts exothermically with the carbon-containing feedstock. The oxidation reactions generate heat internally, eliminating the need for significant external heat input while maintaining temperature control to prevent unwanted side reactions
Solution Approach 2:
The patent changes the energy parameter from requiring external heat input to generating internal heat through oxidation. This fundamental parameter change transforms the process from energy-intensive to energy-self-sufficient, while the molten salt medium helps control the reaction temperature to minimize side reactions
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
Improves product yields of light olefins and oils, reduces reactor size, and decreases waste, achieving efficient conversion of plastics into valuable chemicals with lower emissions.
Implementation Method 1
oxidative cracking is an attractive route for the direct conversion of carbon-containing feedstocks
Implementation Method 2
Pyrolysis is a promising technology that can be used to produce valuable oils and light hydrocarbons
Implementation Method 3
reducing external heat requirements through internal heat generation
Data Source
AI summary
A process for the cracking of a carbon-containing feedstock to produce olefins, aromatics and/or aliphatic includes contacting, in a reactor system, the carbon-containing feedstock with oxygen gas in the presence of a molten salt matrix consisting of a eutectic mixture of alkali metal carbonates, alkali metal hydroxides, alkali metal nitrates, alkali metal halides, alkaline earth metal carbonates, alkaline earth metal hydroxides, alkali earth nitrates, alkaline earth metal halides, rare earth metal carbonates, transition metal carbonates, transition metal hydroxides, transition metal nitrates, transition metal halides, or a mixture of any two or more thereof, to generate an olefin-containing product stream; and collecting an olefin from the olefin-containing product stream; wherein the oxygen is fed with the carbon-containing feedstock in a gas stream comprising from greater than 0 wt % to about 21 wt % oxygen in an inert gas; and the process is conducted in the absence of a catalyst