Kerosene production from power-based syngas

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Kerosene production from power-based syngas – A technical comparison of the Fischer-Tropsch and methanol pathway

lStefan Bube, Nils Bullerdiek, Steffen Voß, Martin Kaltschmitt

Highlights
•Fischer-Tropsch pathway surpasses methanol pathway in total product efficiency.

•Methanol pathway yields highest kerosene-related carbon and energy efficiency.

•Methanol pathway shows thermodynamic advantages due to direct CO2 conversion.

•Chain growth probabilities above 90% favor Fischer-Tropsch pathway efficiencies.

•MTO olefin selectivity mainly determines efficiencies of the methanol pathway.

Abstract
To achieve long-term greenhouse gas (GHG) neutrality within the aviation sector, substituting fossil aviation fuels with Sustainable Aviation Fuels (SAF) derived from renewable energy sources is essential. Among the synthetic SAF options produced through Power-to-Liquid (PtL) processes, the Fischer-Tropsch (FT) and methanol pathway are of significant interest. However, to assess and compare these pathways, detailed technical process analyses are required to provide a sound basis for economic and environmental assessments. Thus, this research paper investigates and compares both SAF production pathways starting from power-derived syngas within an in-depth technical analysis, providing novel insights into overall process characteristics and efficiencies. Carbon and energy flows are derived from steady-state flowsheet simulations. A variation of technical parameters (FT pathway: FT chain growth probability and hydrocracking behavior, Methanol pathway: Dehydration olefin-selectivity and oligomerization product distribution) is carried out to assess impacts on carbon and energy efficiency, indicating uncertainties and parameter ranges for optimized kerosene production. The results show a very high carbon efficiency of the FT pathway (98 to 99%) regarding the total liquid products, while the carbon efficiency regarding kerosene lies between 60 and 77%. For the methanol pathway, a higher kerosene carbon efficiency can be achieved (60 to 90%); however, the total product efficiency (74 to 92%) is notably lower. The energy efficiencies of both pathways behave similarly to carbon efficiency, with the methanol pathway benefiting from thermodynamic advantages, leading to higher energy efficiency at equal carbon efficiency. Within the FT pathway, kerosene efficiency increases at high chain growth probabilities, while a high olefin-selectivity is crucial for efficient kerosene production within the methanol pathway. The analysis results provide comprehensive insights into the technical behavior of the overall processes which contributes to an improved understanding of the production pathways.



Read the full article: https://www.sciencedirect.com/scienc...16236124004162

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The Fischer-Tropsch (FT) pathway is a process for turning a mixture of carbon monoxide and hydrogen (called syngas) into liquid hydrocarbons, which are the building blocks for fuels like diesel and gasoline. Here's a breakdown of the key points:

The Chemistry: In the presence of a catalyst and at elevated temperatures and pressures, the FT pathway transforms syngas into a variety of hydrocarbons. Ideally, the process produces long-chain alkanes (CnH2n+2), with a chain length (n) typically between 10 and 20. These are straight-chain molecules, making them suitable for diesel fuel.

The Feedstock: Syngas itself can be derived from various sources like coal, natural gas, or even biomass through a process called gasification.

Sustainability Potential: The FT pathway is interesting because it can potentially be a sustainable way to produce fuels. If the syngas comes from renewable sources like biomass or captured carbon dioxide, the FT fuels could be considered carbon-neutral. This is why it's seen as a promising technology for producing sustainable aviation fuels (SAF).

History: Developed in the 1920s by Franz Fischer and Hans Tropsch, the FT process was first used to produce synthetic fuels from coal in Germany during World War II. Today, it's gaining renewed interest due to its potential for sustainable fuel production.

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Gemini? "Methanol pathway yields highest kerosene-related carbon and energy efficiency" please tell me about this.

That's right, the methanol pathway is generally considered to be more efficient than the Fischer-Tropsch (FT) pathway for producing kerosene (jet fuel) in terms of both carbon utilization and energy consumption. Here's a breakdown of why:

Simpler Conversion: The methanol pathway involves converting syngas (CO and H2) into methanol (CH3OH) first, then dehydrating (removing water) the methanol to produce hydrocarbons suitable for kerosene. This two-step process is generally more efficient than the single-step conversion in the FT pathway, which can lead to a wider range of hydrocarbon chain lengths besides the ideal ones for kerosene.

Reduced Energy Input: The methanol pathway typically operates at milder temperatures and pressures compared to the FT process. This translates to lower energy consumption during the conversion process.

Carbon Efficiency: Since the methanol pathway targets the specific hydrocarbon chain lengths needed for kerosene, there's less carbon wasted in generating unwanted byproducts compared to the broader product range of the FT process.

However, it's important to consider some nuances:

Technology Maturity: The FT pathway has a longer history of commercial application compared to the methanol route for kerosene production. This means FT technology might be more readily available and less expensive to implement currently.

Feedstock Dependence: The efficiency benefits of the methanol pathway can be dependent on how the syngas is sourced. If renewable sources like captured CO2 are used, the overall carbon footprint can be minimized.

Overall, the methanol pathway shows promise for more sustainable and efficient production of kerosene-like fuels. However, FT technology still holds value due to its established presence and ongoing advancements. As research progresses, both pathways might play a role in the future of sustainable aviation fuels.

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In the context of fuel production, like the Fischer-Tropsch (FT) and methanol pathways we discussed (above), carbon efficiency refers to how well the process utilizes carbon to create the desired fuel.

Here's a breakdown:

Goal: Minimize wasted carbon emissions throughout the fuel production process.

Concept: Imagine you start with a certain amount of carbon in the raw materials (like syngas). Carbon efficiency measures how much of that carbon ends up in the final usable fuel (like kerosene) compared to being lost as other products (like CO2 emissions) during various stages of production.

Benefits: Higher carbon efficiency translates to several advantages:

Reduced greenhouse gas emissions from the fuel production process.
More sustainable fuel production, as less raw carbon is wasted.
Potentially increased fuel yield from the same amount of starting material.
Here's an analogy: Think of carbon efficiency like using ingredients in a recipe. You want most of the flour and sugar to end up in the delicious cake, not wasted in spills or scraps. In fuel production, you want most of the carbon to become your target fuel, not get released as unwanted emissions.