Fischer-Tropsch Products Research Articles

Cross-sectoral assessment of CO2 capture from U.S. industrial flue gases for fuels and chemicals manufacture

Although CO2 impacts the environment negatively, it can be a valuable resource due to its carbon content. The U.S. industry emits over 825 Mt of CO2 annually, with an expected increase in the future. This article analyzes 27 different technology combinations for capturing and using CO2 for industrial feedstocks, including the production of synthetic methane, methanol, and Fischer-Tropsch fuels. The study also estimates and compares the energy requirements for capturing and converting CO2 from 16 different industrial sources, as well as the energy requirements for hydrogen production through state-of-the-art and emerging electrolyzer technologies. Additionally, the study develops a combined scenario that outlines a design for applying an inclusive approach to achieve net-zero CO2 emissions in the industrial sector, incorporating multiple decarbonization measures. The results suggest that the use of CO2 for methane production has the potential to replace all natural gas demands considered in the base case and combined scenarios. However, using CO2 utilization-based Fischer-Tropsch products alone to replace naphtha feedstock and transportation fuels is not sufficient to achieve complete decarbonization in the studied end uses. CO2 utilization-based methanol could potentially substitute for several times the current U.S. methanol production and meet the current global demand for methanol. Moreover, the study conducts an economic analysis to estimate the costs of CO2 utilization, which vary for different industrial sectors and depend on the technologies employed. Overall, this study provides valuable information for policymakers and industry stakeholders who are striving to develop effective strategies to decarbonize the industrial sector.

Insights into Fischer–Tropsch catalysis: current perspectives, mechanisms, and emerging trends in energy research

Fischer–Tropsch (FT) synthesis is an important module for the production of clean and sustainable fuels and chemicals, making it a topic of considerable interest in energy research. This mini-review covers the current literature on FT catalysis and offers insights into the primary products, the nuances of the FT reaction, and the product distribution, with particular attention to the Anderson–Schulz–Flory distribution (ASFD) and known deviations from this fundamental concept. Conventional FT catalysts, particularly Fe- and Co-based catalysis systems, are reviewed, highlighting their central role and the influence of water and water–gas shift (WGS) activity on their catalytic behavior. Various mechanisms of catalyst deactivation are also investigated, and the high methanation activity of Co-based catalysts is illustrated. To make this complex field accessible to a broader audience, we explain conjectured reaction mechanisms, namely, the carbide mechanism and CO insertion. We discuss the complex formation of a wide range of products, including olefins, kerosenes, branched hydrocarbons, and by-products such as alcohols and oxygenates. The article goes beyond the traditional scope of FT catalysis by addressing topics of current interest, including the direct hydrogenation of CO2 for power-to-X applications and the use of bifunctional catalysts to produce tailored FT products, most notably for the production of sustainable aviation fuel (SAF). This mini-review provides a holistic overview of the evolving landscape of FT catalysts and is aimed at both experienced researchers and those new to the field while covering current and emerging trends in this important area of energy research.

Off-grid vs. grid-based: Techno-economic assessment of a power-to-liquid plant combining solid-oxide electrolysis and Fischer-Tropsch synthesis

The economic performance of Power-to-Liquid processes depends substantially on the power source’s features, i.e., electricity costs and full load hours. Off-grid solutions can ensure cheap, green electricity without being exposed to fluctuating electricity markets. A techno-economic assessment of a Power-to-Liquid plant combining solid-oxide electrolysis and Fischer-Tropsch synthesis has been conducted. Off-grid and grid-based scenarios of three process configurations at plant scales from 1 to 1000 MWel. rated electrolyzer power were evaluated. Net production costs of Fischer-Tropsch products ranging from 2.42 to 4.56 €2022/kg were obtained for the grid-based scenarios. In contrast, values of 1.28 to 2.40 €2022/kg were determined for the evaluated off-grid scenarios. Scaling up the plant showed a weakened decrease in net production costs after surpassing a threshold of 100 MWel. due to substantial relative electricity costs of up to 88 %. Thus, future Power-to-Liquid projects should be designed at a scale of 100MWel. rated electrolyzer power. In addition, an availability exceeding 4000 h/a is recommended for off-grid plants, e.g., by implementing hybrid renewable power plants as well as electricity and syngas storage technologies.

Efficient catalyst regeneration through solvent-based wax extraction for Co/Al2O3 Fischer-Tropsch catalysts

The regeneration of Fischer-Tropsch (FT) catalysts plays a crucial role in sustaining their catalytic activity and longevity in sustainable production processes. This research investigates the effectiveness of various solvents, including n-hexane, n-heptane, toluene, xylene, and the liquid fraction of FT products (LF-FT), for catalyst regeneration and extracting wax from the 15 wt%Co/Al2O3 catalyst. Toluene, with a unique combination of key parameters such as polarity, solubility, boiling point, aromatic structure, and chemical interactions, exhibited the highest wax removal efficiency of 90.6%. However, due to its 41 °C lower boiling point compared to toluene and very similar wax removal efficiency, n-hexane appears as a more energy-efficient and cost-effective option for this process. The regenerated catalysts showed comparable characteristics, including the textural properties (surface area, pore size, and pore volume), crystallinity, and reducibility, to fresh catalysts. The slightly lower reduction temperature in the regenerated catalyst indicates a higher possibility for the formation of cobalt active sites during the catalyst reduction process with hydrogen, leading to an increased potential for higher catalytic activity. The LF-FT, comprising paraffins, iso-paraffins, olefins, napthenes, and aromatics, provided a unique combination of aliphatic and aromatic moieties, enhancing the solubility of both polar and nonpolar components in FT wax and improving the wax removal efficiency to 91.5%. The higher boiling point and operating temperature of the LF-FT also contributed to its better performance. Efficient separation of hydrocarbons from solvents allowed for solvent reusability in subsequent FT wax removal cycles, making it advantageous for large-scale applications.

Optimization and evaluation of the distribution of Fischer-Tropsch products over a cobalt-based catalyst utilising design expert software

Modelling biomass to liquid via the Fischer-Tropsch synthesis (FTS) system allows researchers to investigate the most efficient parameters while running the system under optimal conditions. As part of the design of experiments (DOE) procedure, a special data simulation method based on response surface methodology (RSM) is utilized to thoroughly analyse the impact of operating circumstances. The objective of this study was to examine the factors that affect the production of C1, C2–C4, and C5+ in FTS process, and then optimize the critical factors utilising factorial design and response surface techniques. The parameters evaluated were reaction temperature, reaction pressure and the crystallite size of cobalt. The effects of these factors and their potential for synergy were explored simultaneously using multivariate DOE, with the yield of different hydrocarbon composition selectivity's as the measured responses. In the concept generation phase, optimization was based on the literature consulted, which proved to be an effective method for determining the optimization parameters. The detailed conceptual design included the generation of models using statistical methods and response surface models. Finally, the optimized design was validated using catalysts and parameters obtained during the optimization process, and this were compared to the output recorded in the theoretical modelling. The optimized parameters resulted in performance consistency, with the theoretical model for each group of hydrocarbons being validated by actual experiments. The established models were seen to characterize hydrocarbon distributions accurately and repeatedly over a wide range of reaction conditions (200–270 °C, 5–20 Bar, and 3–26 nm) using a cobalt-based catalyst. According to the detailed quantitative models developed, for higher C5+ production, 220 °C, 10 barg and 11 nm (cobalt crystallite) benchmark parameters were set to produce 19.3 % C1, 11.4 % C2–C4 and 69 % C5+ selectivity's. Comparative analysis showed a 1.9 %, 3.9 % and 0.3 % percentage difference between the theoretical output and the actual output of C1, C2–C4 and C5+, respectively.

Carbon Neutral Fuels and Chemicals from Standalone Biomass Refineries

The urgency to eliminate man-made greenhouse gas emissions and achieve energy security/independence by all countries justifies an energy policy that considers the major role of renewable biomass as a source of organic feedstock for producing adequate organic chemicals and biofuels on a sustainable basis and economically. This paper investigates a three-stage thermochemical process to convert wet biomass into a tailored mix of syngas for producing green methanol, hydrogen, and Fischer-Tropsch products. The three-stage thermochemical process involves the torrefaction of wet biomass using hot carbon monoxide gas, pyrolysis of torrefied biomass to produce biochar, and final gasification of the pyrolysis gases by auto thermal reforming up to 1400o C temperature. The proposed process is suitable to utilize a wide variety of biomass materials such as freshly harvested biomass without field drying, agro waste, forest/plantation litter, organic municipal solid wastes, sludge from sewage water treatment plants, solid biomass rejects from anaerobic digesters, bagasse from sugar or first-generation ethanol plants, organic solid rejects from second-generation ethanol plants, waste glycerides from biodiesel plants, industrial organic waste, etc. The proposed process offers valorization of biomass so that the net income of farmers is enhanced a fewfold by selling freshly harvested biomass. The economic analysis found that carbon-neutral hydrogen, methanol, etc can be produced below the prevailing costs of such products derived from fossil crude oil or natural gas without considering carbon credits. It is feasible in a standalone biomass refinery to use any biomass as only one bulk raw material/feedstock without any harmful emissions to water bodies or the atmosphere except carbon neutral carbon dioxide gas if not sequestrated.

Mathematical modeling and evaluation of permeation and membrane separation performance for Fischer–Tropsch products in a hydrophilic membrane reactor

Abstract A mathematical model was constructed to estimate the performance of an MFI-membrane reactor used for Fischer–Tropsch synthesis to produce a mixture of liquid hydrocarbons. In order to accurately evaluate the reactor’s performance a parametric study was performed. Under certain operational conditions, such as the total initial pressure in the reaction zone (1–4 MPa) and the hydrogen/carbon monoxide ratio (H2/CO: 1 to 2) on the performance of the studied reactor. The selectivity (productivity) of the hydrocarbon products (S i ), the quantity of hydrocarbons permiated (θ i ) and the separation factors of each space (α i ) were predicted. With increasing pressure, it is observed that θ CO and θ H 2 ${\theta }_{{H}_{2}}$ are decreasing from 0.62 to 0.45 and from 0.55 to 0.49 respectively. However, as the H2/CO ratio rises, this measurement shows a slight increase. Aside from, the separation factors of the majority of the current species are unaffected by the H2/CO ratio increasing, while the separation factors of carbon monoxide and hydrogen are increasing. Similarly the selectivity of water, methane, carbon dioxide and ethane increases with increasing H2/CO ratio. Based on these findings it is revealed that the membrane can enable permeability for all species present in the products mixture with varying separation factors, and that the ability to separate species other than water from the reaction side is essentially non-existent.

Analysis of integrated CO2 capture and utilization via calcium-looping in-situ dry reforming of methane and Fischer-Tropsch for synthetic fuels production

Calcium-looping is an attractive approach for removing CO2 in flue gas from the coal-fired power plant to form CaCO3. The integration of CO2 capture via calcium-looping and in-situ dry reforming of methane with CaCO3 allows the simultaneous CaCO3 decomposition to regenerate CaO and syngas production. The produced syngas is expected for further utilization, e.g. Fischer-Tropsch synthesis to produce valuable fuels. In this work, an integrated process of calcium-looping in-situ dry reforming of methane and Fischer-Tropsch was developed using Aspen Plus. Moreover, two other processes were also simulated as the comparison, consisting of the serial process of calcium-looping CO2 capture, ex-situ dry reforming of methane with CO2 and Fischer-Tropsch and the standalone process of calcium-looping CO2 capture. The results indicate that the reduction in the demand for CaO sorbent and the enhancement in Fischer-Tropsch products yield and carbon conversion efficiency are achieved by integrating in-situ dry reforming of methane with CaCO3. Additionally, integrating CO2 capture and in-situ dry reforming of methane with CaCO3 in the case of the integrated process is efficient for enhancing the system efficiency and energy availability. Compared with the serial process, the integrated process shows a drop in the heat energy requirement of 28.08% and possesses the energy conversion efficiency of 43.74% and exergy efficiency of 41.81%. This work exhibits the prospect of the integrated process of calcium-looping in-situ dry reforming of methane and Fischer-Tropsch in the field of CO2 capture and utilization for Fischer-Tropsch fuels production.

Evaluation of CO2 sources for Power-to-Liquid plants producing Fischer-Tropsch products

In addition to the climate crisis’s looming dangers, Europe was recently affected by profoundly volatile energy markets, entailing soaring inflation and political uncertainty. Power-to-Liquid processes have the potential to curb global warming by valorizing CO2 to produce synthetic fuels and platform chemicals while simultaneously substituting fossil energy imports. The impact of the CO2 source, i.e., cement production, biogas upgrading and solid biomass combustion, on Power-to-Liquid plants was evaluated by implementing the designed configuration, including CO2 capture, solid-oxide electrolyzer, Fischer-Tropsch synthesis and steam reforming, in IPSEpro, a stationary equation-based process simulation tool. Maximum Power-to-Liquid efficiency of 63.8% and maximum carbon efficiency of 88.6% were obtained by exploiting CO2 emitted by a biogas upgrading unit. Solid-oxide electrolyzers ranging from 23 MWel. (biogas) to 504 MWel. (cement) are required to process CO2 streams from 4.5 to 100 t/h. In addition, the mass and energy balances of the three considered configurations were determined and embedded in a process flow diagram. The presented study aims to facilitate future decisions concerning carbon capture and utilization policy by assessing the CO2 source’s influence on Power-to-Liquid plants’ key performance indicators. Furthermore, the underlying work supports a sustainable realization of Power-to-Liquid plants by offering a framework for exploiting CO2 sources.

Evaluating microbial contaminations of alternative heating oils.

Since 2008, European and German legislative initiatives for climate protection and reduced dependency on fossil resources led to the introduction of biofuels as CO2-reduced alternatives in the heating oil sector. In the case of biodiesel, customers were confronted with accelerated microbial contaminations during storage. Since then, other fuel alternatives, like hydrogenated vegetable oils (HVOs), gas-to-liquid (GtL) products, or oxymethylene ether (OME) have been developed. In this study, we use online monitoring of microbial CO2 production and the simulation of onset of microbial contamination to investigate the contamination potential of fuel alternatives during storage. As references, fossil heating oil of German refineries are used. Biodiesel blends with fossil heating oils confirmed the promotion of microbial activity. In stark contrast, OMEs have an antimicrobial effect. The paraffinic Fischer-Tropsch products and biogenic hydrogenation products demonstrate to be at least as resistant to microbial contamination as fossil heating oils despite allowing a diversity of representative microbes. Through mass spectrometry, elemental analysis, and microbial sequencing, we can discuss fuel properties that affect microbial contaminations. In summary, novel, non-fossil heating oils show clear differences in microbial resistance during long-term storage. Designing blends with an intrinsic resistance against microbial contamination and hence reduced activity might be an option.

Fluidized bed gasification of solid recovered fuels in a 500 kWth pilot plant

On the way to climate-neutrality with low resource consumption, the economics worldwide needs ways to obtain high-quality products from existing material flows. If waste is used as a feedstock for gasification, high-quality syngas is obtained from which new products for the chemical industry (e.g. methanol) or the transport sector (Fischer-Tropsch products) can be obtained. The fluidized bed-based High-Temperature-Winkler process is particularly suitable for the gasification of solid recovered fuel (SRF) and biomass that are difficult to grind since the feedstock can be processed in lump form. The gasification characteristics of SRF pellets were investigated in a 500 kWth pilot gasifier at the Technical University of Darmstadt. After a co-gasification with pre-dried lignite, a mono SRF gasification could be realized. This paper presents the effects of operating temperature and the SRF content in the feedstock on the syngas quality, which is characterized by the target components CO and H2, the undesired fraction of CH4, and some representative higher hydrocarbons. It could be shown, that the syngas gas components CO and H2 depend mainly on the gasification temperature and not on the used feedstock. On the other hand, the higher amount of volatiles in the SRF fraction rises the methane concentration and the amount of higher hydrocarbons in the syngas. It was observed that these components are decomposed at higher gasification temperatures and an almost tar-free syngas is produced.

Carbon negative transportation fuels – A techno-economic-environmental analysis of biomass pathways for transportation

Global warming and fossil fuel depletion have necessitated alternative sources of energy. Biomass is a promising fuel source because it is renewable and can be carbon negative, even without carbon capture and storage. This study considers biomass as a clean, renewable source for transportation fuels. An Aspen Plus process simulation model was built of a biomass gasification biorefinery with Fischer-Tropsch (FT) synthesis of liquid fuels. A GaBi life cycle assessment model was also built to determine the environmental impacts using a cradle-to-grave approach. Three different product pathways were considered: Fischer-Tropsch synthetic diesel, hydrogen, and electricity. An offgas autothermal reformer with a recycle loop was used to increase FT product yield. Different configurations and combinations of biorefinery products are considered. The thermal efficiency and cost of production of the FT liquid fuels are analyzed using the Aspen Plus process model. The greenhouse gas emissions, profitability, and mileage per kg biomass were compared. The mileage traveled per kilogram biomass was calculated using modern (2019–2021) diesel, electric, and hydrogen fuel cell vehicles. The overall thermal efficiency was found to be between 20 and 41% for FT fuels production, between 58 and 61% for hydrogen production, and around 25–26% for electricity production for this biorefinery. The lowest production costs were found to be $3.171/gal of FT diesel ($24.304/GJ), $1.860/kg of H 2 ($15.779/GJ), and 13.332¢/kWh for electricity ($37.034/GJ). All configurations except one had net negative carbon emissions over the life cycle of the biomass. This is because carbon is absorbed in the trees initially, and some of the carbon is sequestered in ash and unconverted char from the gasification process, furthermore co-producing electricity while making transportation fuel offsets even more carbon emissions. Compared to current market rates for diesel, hydrogen, and electricity, the most profitable biorefinery product is shown to be hydrogen while also having net negative carbon emissions. FT diesel can also be profitable, but with a slimmer profit margin (not considering government credits) and still having net negative carbon emissions. However, our biorefinery could not compete with current commercial electricity prices in the US. As oil, hydrogen, and electricity prices continue to change, the economics of the biorefinery and the choice product will change as well. For our current biorefinery model, hydrogen seems to be the most promising product choice for profit while staying carbon negative, while FT diesel is the best choice for sequestering the most carbon and still being profitable.

Renewable transport fuel production combined with cogeneration plant operation and waste heat recovery in district heating system

For the future energy markets, where the role of fossil fuels will be minimized and district heating systems will become more efficient through the use of waste streams, a new concept is proposed based on tri-generation of Fischer–Tropsch (FT) products, heat, and power. The challenge of combining the transport sector with a District Heating (DH) network and power grid is presented in this article by discussing the operating modes of the gasifier, FT product output (as a raw material for refinery) and waste stream generated after the synthesis reactor, preliminary process management schemes, market factors, and economic attractiveness. The feasibility of the concept was examined for an existing combined heat and power plant in Lithuania, which could become a potential demo plant. To demonstrate the feasibility of this concept, which may help create independence from fossil fuels through the use of syngas (for a sudden increase in heat demand), a techno-economic assessment was performed. The analysis of various scenarios showed that the cost of the FT product may be between 0.67 and 1.47 €/kg for gasifier capacities ranging from 10 to 40 MW. However, the economic attractiveness assessment revealed that the concept is profitable at a liquid biofuel (FT product) prime cost below 1.07 €/kg (without electrolysis capability).

A Circular Approach for Making Fischer–Tropsch E-fuels and E-chemicals From Biogas Plants in Europe

In a mature circular economy model of carbon material, no fossil compound is extracted from the underground. Hence, the C1 molecule from non-fossil sources such as biogas, biomass, or carbon dioxide captured from the air represents the raw material to produce various value-added products through carbon capture and utilization routes. Accordingly, the present work investigates the utilization of the full potential of biogas and digestate waste streams derived from anaerobic digestion processes available at the European level to generate synthetic Fischer–Tropsch products focusing on the wax fraction. This study estimates a total amount of available carbon dioxide of 33.9 MtCO2/y from the two above-mentioned sources. Of this potential, 10.95 MtCO2/y is ready-to-use as separated CO2 from operating biogas-upgrading plants. Similarly, the total amount of ready-to-use wet digestate corresponds to 29.1 Mtdig/y. Moreover, the potential out-take of Fischer–Tropsch feedstock was evaluated based on process model results. Utilizing the full biogas plants’ carbon potential available in Europe, a total of 10.1 Mt/h of Fischer–Tropsch fuels and 3.86 Mt/h of Fischer–Tropsch waxes can be produced, covering up to 79% of the global wax demand. Utilizing only the streams derived from biomethane plants (installed in Europe), 136 ton/h of FT liquids and 48 ton/h of FT wax can be generated, corresponding to about 8% of the global wax demand. Finally, optimal locations for cost-effective Fischer–Tropsch wax production were also identified.

The “Innovation Liquid Energy” (ger. “Innovation Flüssige Energie” - IFE) Project: Development of a 1MW Power-to-Liquid Plant Based on Co-SOC Electrolysis and Fischer-Tropsch Synthesis

The European climate protection program adopted in 2018 targets for a reduction in greenhouse gas emissions from the current 20% to 40% (compared to 1990) by 2030 ([1]), together with a simultaneous increase in the share of energy from renewable sources from the current 20% to 32%. In the transport sector, an increase in the share of renewable fuels from the current 10% to 14% is aimed for, with a maximum of 7% of this being Generation 1 fuels. Therefore, additional solutions such as power-to-liquid (PtL) fuels are needed to generate an immediate impact on existing fleets in order to achieve European and global CO2 emission targets in mobility.The overall objective of the IFE (Innovation Liquid Energy) project is the development and realization of a Power-to-Liquid plant with a combined water and carbon dioxide high-temperature electrolysis (Co-SOEC) and a Fischer Tropsch synthesis for the production of synthetic fuel. By coupling these two processes in a way which enables heat integration, an increase of the overall electrical efficiency to 55% is to be achieved. The overall plant with a nominal electrolyser power of around 1 MW will constitute of several parts. Carbon dioxide is extracted from industrial waste gas or from a biogas/biomass plant and fed into the electrolyser process. There, a synthesis gas of hydrogen and carbon monoxide is produced based on an innovative Co-SOEC unit with an efficiency higher than 80%. In the next process stage, the syngas is fed into a low-temperature Fischer-Tropsch synthesis, where syncrude is produced with predominantly liquid and paraffinic products. The estimated output of Fischer-Tropsch products is around 500.000 L diesel-equivalent. The diesel fraction is targeted to meet the required quality of the EN15940 standard for alternative paraffinic diesel fuel.The present work shows the status of the project and how specific challenges such as the reuse of the tail gas, the reuse of the aqueous product fraction and heat integration are addressed. Thereby a focus on the development of the co-SOEC unit and the optimization of the overall process towards highest efficiencies is being laid. Furthermore a techno-economic view on the potential cost of Fischer-Tropsch products is given, where, dependent on the electricity cost and full-load operating hours of the plant, FT-diesel costs in the range of 1-3 € seem reasonable (without tax and margin).[1] The European parliament and the council of the European Union:DIRECTIVE (EU) 2018/2001, (L 328/82), Brüssel, 2018 https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018L2001&from=EN

Green Process Design for Reductive Hydroformylation of Renewable Olefin Cuts for Drop-In Diesel Fuels.

CO2‐neutral fuels are a way to cleaner and more sustainable mobility. Utilization of bio‐syngas via Fischer‐Tropsch (FT) synthesis represents an interesting route for the production of tailormade biofuels. Recent developments in FT catalyst research led to olefin‐enriched products, enabling the synthesis of alcohol‐enriched fuels by reductive hydroformylation of the C=C bond. Several alcohols have already proven to be suitable fuel additives with favorable combustion behavior. Here, a hydroformylation‐hydrogenation sequence of FT‐olefin‐paraffin mixtures was investigated as a potential route to alcohols. A liquid‐liquid biphasic system with a rhodium/3,3’,3’’‐phosphanetriyltris(benzenesulfonic acid) trisodium salt (TPPTS) catalyst system was chosen for effective catalyst recycling. After optimizing reaction conditions with a model substrate consisting of 1‐octene and n‐heptane the conversion of an actual olefin‐containing C5‐C10 FT product fraction to alcohols in continuously operated processes for 37 h was achieved with a total turnover number of 23679.

Bifunctional Co‐based Catalysts for Fischer‐Tropsch Synthesis: Descriptors Affecting the Product Distribution

AbstractThe conversion of synthesis gas to hydrocarbons in the Fischer‐Tropsch (FT) synthesis suffers from a broad product distribution not directly providing high fuel quality. This work, therefore, aims at bifunctional catalysts combining the FT and hydroprocessing (HP) reaction for tailoring the product spectrum. Therefore, we applied a bottom‐up synthesis strategy for bifunctional cobalt/zeolite catalysts and investigated the obtained materials by advanced characterizations such as 3D TEM tomography. Based on the results, descriptors are defined for the acidity and the porosity, which are varied by changing the material preparation parameters. The catalytic properties of the obtained materials are studied in FT experiments at industrially relevant conditions (20 bar, 240 and 260 °C) and are correlated to the material properties by means of the respective descriptors. Therefore, the product distribution was analyzed in detail and distinguished between n‐paraffins and 1‐olefins as typical FT‐products as well as paraffinic and olefinic isomers formed in the HP classified in different fractions. It was found that, apart from the acidity, the pore structure plays a vital role in primary and secondary cracking/isomerization reactions. In addition to that, the particular 3D pore structure and thus the individual transport trajectories of the FT products are strongly affecting the cracking and isomerization probability and consequently the product distribution.

Techno-economic feasibility of a biomass-to-X plant: Fischer-Tropsch wax synthesis from digestate gasification

A techno-economic analysis is performed, assessing the production costs of Fischer-Tropsch syncrude and waxes of carbon number C20+. The products are obtained from the gasification of digestate from anaerobic digestion inside a dual fluidized bed gasifier (3.11 MWth). The results are compared against the same system fed with lignocellulosic biomass. The syngas is cleaned from impurities and conditioned to reach the desired H2/CO molar ratio of 1.8 at the inlet of the Fischer-Tropsch reactor. The Fischer-Tropsch products distribution is based on experimental data of a cobalt-based catalyst. Two process configurations are studied: (1) the Fischer-Tropsch off-gas are employed to produce electricity; (2) the off-gas are recirculated to the gasifier for enhanced wax production. Co-production of steam is also investigated. The results show an advantageous production of Fischer-Tropsch compounds utilizing digestate over wood biomass. The highest plant efficiency (i.e., biomass-to-liquid fuel) of 56.3% is reached with digestate feedstock and off-gas recirculation, outputting 61.5 kgwax/tdig. The minimum wax production cost is of 3.04 €/kgwax, assuming 7.5% discount rate and 25-years plant operation.

CO2 from direct air capture as carbon feedstock for Fischer-Tropsch chemicals and fuels: Energy and economic analysis

The investigated plant concept integrates the direct air capture technology with the Fischer-Tropsch synthesis. 250 kt/h of air, with a CO2 concentration of 400 ppm, are used as feedstock to produce the synthetic hydrocarbons. The direct air capture is modelled as a high-temperature calcium recovery loop process. An alkaline electrolyser and a reverse water-gas shift reactor produce the required syngas. The Fischer-Tropsch products distribution is described by a carbide model developed for a Co-Pt/ɣAl2O3 catalyst for alkanes and alkenes of carbon number C1-C70. Five integration scenarios are analysed. In the base case, the energy demand of the direct air capture process is supplied with natural gas from the distribution grid. In improved configurations, the effect of Fischer-Tropsch off-gas recirculation to the reverse water-gas shift and/or the direct air capture units is explored, excluding the need of fossil fuel. An electrified direct air capture solution is also included. In the analysed scenarios, the highest system efficiency corresponds to 36.3 %, while the maximum carbon dioxide conversion is of 68.3 %. The maximum waxes production corresponds to 8.7 t/h. Lastly, capital and operating plant costs are allocated in an economic investigation, considering different market electricity costs and financial risk values. In a medium financial risk scenario (interest rate: 7.5 %), the minimum Fischer-Tropsch waxes production cost corresponds to 6.3 €/kgwax, reaching 5.05 €/kgwax at an interest rate of 0%. Lastly, the effect of learning curves over the production cost at the year 2030 and 2050 is included.

Experimental Parameter Study on Synthesis Gas Production by Steam-Oxygen Fluidized Bed Gasification of Sewage Sludge

The conversion of biogenic residues to fuels and chemicals via gasification and synthesis processes is a promising pathway to replace fossil carbon. In this study, the focus is set on sewage sludge gasification for syngas production. Experiments were carried out in a 20 kW fuel input bubbling fluidized bed facility with steam and oxygen as gasification agent. In-situ produced sewage sludge ash was used as bed material. The sensitivity of the key operation parameters gasifier temperature, oxygen ratio, steam to carbon ratio, and the space velocity on the syngas composition (H2, CO, CO2, CH4, CxHy, H2S, COS, NH3, and tars) was determined. The results show that the produced syngas has high H2 and CO concentrations of up to 0.37 m3 m−3 and 0.18 m3 m−3, respectively, and is thus suitable for synthesis of fuels and chemicals. By adjusting the steam to carbon ratio, the syngas’ H2 to CO ratio can be purposely tailored by the water gas shift reaction for various synthesis products, e.g., synthetic natural gas (H2/CO = 3) or Fischer–Tropsch products (H2/CO = 2). Also, the composition and yields of fly ash and bed ash are presented. Through the gasification process, the cadmium and mercury contents of the bed ash were drastically reduced. The ash is suitable as secondary raw material for phosphorous or phosphate fertilizer production. Overall, a broad database was generated that can be used for process simulation and process design.