Composite Catalyst for Direct Light Olefin Synthesis
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Solution Overview
Problem
The existing Fischer-Tropsch synthesis technology for converting synthesis gas to light olefins has limitations in selectivity, with only up to 58% selectivity of C2-C4 hydrocarbons and a wide distribution of hydrocarbons, including methane and long-chain hydrocarbons, making it inefficient for producing light olefins like ethylene and propylene.
Innovation Solution
A composite catalyst material composed of multicomponent metal composites and inorganic solid acid with hierarchical pore structures is used, allowing CO molecules to react with dissociated oxygen atoms to form CO2, avoiding hydrogen consumption and enabling the direct conversion of synthesis gas to light olefins with high selectivity, bypassing the need for additional processes like methanol synthesis and water-gas shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional Fischer-Tropsch synthesis is used to convert synthesis gas to light olefins, then the process can produce hydrocarbons, but the selectivity of C2-C4 hydrocarbons is limited to no more than 58% and a wide distribution of hydrocarbons including methane and long-chain hydrocarbons is generated
Solution Approach 1:
The patent segments the Fischer-Tropsch synthesis process into two distinct functional zones within the same reactor: a water-gas shift zone (upper part) that converts CO to H2 and CO2, and a Fischer-Tropsch synthesis zone (lower part) that produces hydrocarbons. This segmentation allows optimization of each zone's function, with the water-gas shift zone adjusting the H2/CO ratio to favor light olefin production in the synthesis zone, thereby improving selectivity beyond the traditional 58% limit.
Solution Approach 2:
The patent changes key process parameters including operating temperature (200-400°C), pressure (0.1-10.0 MPa), and H2/CO ratio (2:1 to 6:1) to optimize light olefin selectivity. By controlling the water-gas shift reaction to produce specific H2/CO ratios and maintaining appropriate temperature and pressure conditions in the Fischer-Tropsch zone, the patent achieves C2-C4 hydrocarbon selectivity exceeding 58%, with light olefin selectivity reaching 50-85%.
2Device complexity
If direct conversion of synthesis gas to light olefins is attempted, then the process flow can be simplified, but achieving high selectivity of light olefins remains a challenge
Solution Approach 1:
The patent merges the water-gas shift process and Fischer-Tropsch synthesis into a single integrated reactor system with two functional zones. This combination eliminates the need for separate water-gas shift reactors and methanol synthesis units required by conventional indirect routes, simplifying the overall process flow while maintaining high light olefin selectivity through the synergistic interaction between the two zones.
Solution Approach 2:
The patent uses CO2 produced in the water-gas shift zone as an intermediary that diffuses into the Fischer-Tropsch synthesis zone. The CO2 acts as a mediator that influences the reaction environment, helping to suppress methane and long-chain hydrocarbon formation while promoting light olefin production, thereby achieving high selectivity in the direct conversion process.
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 achieves a selectivity of 50%-85% for light olefins, significantly exceeding traditional Fischer-Tropsch limits, reduces production costs, and simplifies the process flow, making it more economically viable for producing light olefins from coal-based synthesis gas.
Implementation Method 1
CO is generally considered to adsorb and dissociate on the surface of the catalyst
Implementation Method 2
CO is generally considered to adsorb and dissociate on the surface of the catalyst
Implementation Method 3
CO is generally considered to adsorb and dissociate on the surface of the catalyst and is hydrogenated to generate CHx intermediate species
Implementation Method 4
These surface CHx intermediates go through polymerization on the catalyst surface, growing into longer carbon chain hydrocarbons
Data Source
AI summary
The present invention discloses catalyst and method for producing light olefins directly from synthesis gas by a one-step process, and particularly relates to method and catalyst for directly converting synthesis gas into light olefins by a one-step process. The provided catalysts are composite materials formed of multicomponent metal oxide composites and inorganic solid acids with hierarchical pore structures. The inorganic solid acids have a hierarchical pore structure having micropores, mesopores and macropores. The metal composites can be mixed with or dispersed on surfaces or in pore channels of the inorganic solid acid and can catalyze the synthesis gas conversion to a C2-C4 light hydrocarbon product containing two to four carbon atoms. The single pass conversion of CO is 10%-60%. The selectivity of light hydrocarbon in all hydrocarbon products can be up to 60%-95%, wherein the selectivity of light olefins (C2═—C4═) is 50%-85%.