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Artificial fuels have been researched for more than a decade now in an attempt to find alternative sources of energy. With global climatic conditions rapidly approaching the end of their safe line, an emphasis on escalating the change has been seen in recent times. Synthetic fuels are a diverse group of compounds that can be used as replacements for traditional fuels, such as gasoline and diesel. This paper provides a comprehensive review of synthetic fuels, with a focus on their classification and production processes. The article begins with an in-depth introduction, followed by virtually classifying the major synthetic fuels that are currently produced on an industrial scale. The article further discusses their feedstocks and production processes, along with detailed equations and diagrams to help readers understand the basic science behind synthetic fuels. The environmental impact of these fuels is also explored, along with their respective key players in the industry. By highlighting the benefits and drawbacks of synthetic fuels, this study also aims to facilitate an informed discussion about the future of energy and the role that synthetic fuels may play in reducing our reliance on fossil fuels.

SignificanceCO2 is a greenhouse gas. Synthesis of liquid fuel using CO2 and H2 is promising for the sustainability of mankind. The reported technologies usually proceed via CO intermediate, which needs high temperature, and tend to cause low selectivity. Direct hydrogenation of CO2 to liquid fuel, not via CO, is a challenging issue. In this work, we designed a Co6/MnOx nanocatalyst that could successfully avoid the CO route. The reaction could proceed at 200 °C, which is much lower than those reported so far. The selectivity of the liquid fuel in total products reached 53.2 C-mol%, which is among the highest reported to date. Synthesis of liquid fuels (C5+ hydrocarbons) via CO2 hydrogenation is very promising. Hydrogenation of CO2 to liquid hydrocarbons usually proceeds through tandem catalysis of reverse water gas shift (RWGS) reaction to produce CO, and subsequent CO hydrogenation to hydrocarbons via Fischer–Tropsch synthesis (FTS). CO2 is a thermodynamically stable and chemically inert molecule, and RWGS reaction is endothermic and needs a higher temperature, whereas FTS reaction is exothermic and is thermodynamically favored at a lower temperature. Therefore, the reported technologies have some obvious drawbacks, such as high temperature, low selectivity, and use of complex catalysts. Herein we discovered that a simple Co6/MnOx nanocatalyst could efficiently catalyze CO2 hydrogenation. The reaction proceeded at 200 °C, which is much lower than those reported so far. The selectivity of liquid hydrocarbon (C5 to C26, mostly n-paraffin) in total product could reach 53.2 C-mol%, which is among the highest reported to date. Interestingly, CO was hardly detectable during the reaction. The in situ Fourier transform infrared characterization and 13CO labeling test confirmed that the reaction was not via CO, accounting for the eminent catalytic results. This report represents significant progress in CO2 chemistry and CO2 transformation.

Direct synthesis of liquid fuel (C 5+ hydrocarbons) through CO 2 hydrogenation has attracted considerable interest. However, it is plagued by high selectivity of C 1 by-products (CO and CH 4 ) and low reaction activity. Herein, we report that Na-FeZn catalysts promoted by a combination of metal additives and investigate their synergistic effect in the catalytic CO 2 hydrogenation reaction. The CO 2 conversion is high to 40.6% with the 68.3% C 5+ selectivity. The characteristic results reveal the specific surface area has a great influence on the catalytic performance. Furthermore, the synergistic effect of Mn in the catalyst enhances CO 2 adsorption while weakening H 2 adsorption, thus remarkably promoting the carbon chain growth and limiting the production of C 1 products. This study offers a promising approach to modulating the metal electronic environment and improving carbon efficiency for CO 2 hydrogenation reactions. Graphical Abstract We present a simple NaFeZnMn-S nanocatalyst that can effectively catalyze CO 2 hydrogenation to C 5+ hydrocarbons. The selectivity towards C 5+ hydrocarbons is as high as 68.3% at 40.6% CO 2 conversion.

The Fine  −  Kinney is a risk assessment method widely used in many industries due to its ease of use and quantitative risk evaluation. As in other methods, it is a method that recommends taking a series of control measures for operational safety. However, it is not always possible to implement control measures based on the determined priorities of the risks. It is considered that determining the priorities of these measures depends on many criteria such as applicability, functionality, performance, and integrity. Therefore, this study has studied the prioritization of control measures in Fine − Kinney-based risk assessment. The criteria affecting the prioritization of control measures are hierarchically structured, and the importance weights of the criteria are determined by the Bayesian Best–Worst Method (BBWM). The priorities of control measures were determined with the fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje (FVIKOR) method. The proposed model has been applied to the risk assessment process in a petrol station’s liquid fuel tank area. According to the results obtained with BBWM, the most important criterion affecting the prioritization of control measures is the applicability criterion. It has an importance weight of about 42%. It is followed by performance with 31%, functionality with 18%, and integrity with 10%, respectively. FVIKOR results show that the “Periodic control of the ventilation device” measure is the top priority for Fine − Kinney risk assessment. “The absence of any ducts or sewer pits that may cause gas accumulation in the tank area and near the dispenser; Yellow line marking of entry and exit and vehicle roads; Placing of speed limit warning signs” has been determined as a secondary priority. On conclusion, this proposed model is expected to bring a new perspective to the work of occupational health and safety analysts, since the priority suggested by Fine − Kinney risk analysis methods is not always in the same order as the one in the stage of taking action, and the source, budget, and cost/benefit ratio of the measure affect this situation in practice.

Since plastic wastes are commonly found and accumulate in numerous types and forms, the pyrolysis of plastic waste mixtures seems more feasible to be selected for large-scale production. However, the process typically produces less liquid than individual plastic pyrolysis. This study proposed a viable approach for catalytic pyrolysis by using natural mineral catalysts without modification. Bentonite was selected as a natural mineral catalyst while HZSM-5 was used for performance comparison. The process was evaluated in situ using a fixed-bed reactor at temperatures between 400 °C and 500 °C. The mixture of plastic waste composition was designed based on the non-recycled plastics data. The results showed that 42.55 wt% of liquid yield was obtained from thermal pyrolysis using Malaysia’s non-recycled plastics data. It was then found that using HZSM-5 and bentonite catalysts significantly boosted liquid products to about 56 and 60%, respectively. The presence of catalysts also positively minimized tar formation and eliminated wax formation in the liquid product. Furthermore, the catalytic process showed remarkable improvements in aromatics and alkane compounds in the liquid while only alkenes were found to be high when bentonite was used.

Long-distance oil pipeline is the most economical way to transport the crude oil and liquid chemical raw materials. The spillage liquid may enter the covered drain to form the flame spread over sub-flash liquid fuel. In this paper, a self-designed fuel-storable quartz glass pipe with the size of 100 cm long and 10 cm inner diameter is used to simulate a long-narrow confined space. The n -butanol flame spread behavior in the circular confined space is investigated by controlling the sealing ratio of the tube. The results show that the flame spreading behavior in the confined space is significantly different from that in the open space. There is the flame shuttle behavior at the sealing ratio β  = 10% and the self-extinguishing behavior of the flame occurs at β  = 55%. As the sealing ratios β  > 10%, there is an obvious “retraction” behavior, resembling flame spreading over a hydrocarbon fuel in an open environment. However, the controlling mechanism is essentially different. For flame spread over butanol in a tube, the flame retreating is due to the insufficient oxygen supply. By contrast, for the flame spread over hydrocarbon fuel in an open space, the flame retreating is due to the evident difference of the flashpoint and fire point of the hydrocarbon fuel. The flame pulsation frequency increases from 2.0 to 5.7 Hz as the sealing ratio increases from β  = 2% to 40%; then, it decreases to 1.3 Hz at β  = 55%. The increase of the pulsation frequency in the initial stage indicates that the flame burns inadequately due to the reduced oxygen supply in the large sealing ratio. At β  = 2%, the instantaneous velocity alternates between a low speed of 1–3 cm s −1 and a high speed of 5–8 cm s −1 , with an average velocity of 1.9 cm s −1 . This flame spreading behavior is regarded as the quasi-uniform propagation. At β  = 45%, the average velocity reaches 2.3 cm/s. At β  = 55%, the average velocity of flame is 0.54 cm s −1 , indicating that the flame is difficult to spread forward. When the flame passes through the oxygen concentration sensor, there is a low oxygen concentration valley in the range of 1–5%. In middle area of the tube, the combustion can maintain owing to the oxygen concentration below 12%. This paper provides some theoretical support and guidance for fire safety and rescue in the long-narrow confined space.

Low-carbon liquid fuels are needed for decarbonization of hard-to-decarbonize segments of the transportation sector. This decarbonization can be limited by the amount of renewable carbon. Thermochemical conversion of biomass/municipal solid waste (MSW) through gasification is a promising route for producing low-carbon fuels. There are two major opportunities for increasing the amount of low-carbon liquid fuel that can be produced from gasification in any region. One is to increase the amount of liquid fuel from a given amount of biomass/MSW, particularly by hydrogen-enhancement of gasification synthesis gas. Second is the potential for large expansion of use of biomass feedstocks from its present level. Such biomass feedstocks include agricultural waste, forestry waste, MSW, and specially grown biomass that does not interfere with food production. The use of MSW may provide advantages of an established network for pickup and transportation of feedstock to disposal sites and the avoidance of methane produced from landfilling of MSW. As a case study, we looked at potential expansion of US low-carbon fuel production, considering the recent projections of the 2024 USDOE report, which estimated potential production of a billion tons/yr of biomass/MSW feedstocks in the US. This report included an estimated potential for liquid biofuel production of 60 billion gallons/yr of diesel energy equivalent fuel without the use of hydrogen enhancement. By hydrogen-enhanced biomass/MSW gasification, this projection could be doubled to 120 billion gallons/yr of diesel energy equivalent fuel. Furthermore, the co-location potential of biomass/MSW resources with potential renewable energy generation sites is explored. This overlap of hydrogen production and biomass production in the US are located in regions such as the US Midwest, Texas, and California. This co-location strategy enhances logistical feasibility, reducing transport costs and optimizing energy system integration; and can be applied to other geographical locations. Hydrogen-enhanced biomass/MSW gasification offers a promising route to substantially increase low-carbon liquid fuel production (e.g., methanol) and support increased liquid fuel production and greenhouse gas reduction goals.

Greener Fischer-Tropsch Processes How can we use our carbon-based resources in the most responsible manner?How can we most efficiently transform natural gas, coal, or biomass into diesel, jet fuel or gasoline to drive our machines?The Big Questions today are energy-related, and the Fischer-Tropsch process provides industrially tested solutions.

This study investigates the critical durability challenges of direct liquid fuel cells using B/N‐H‐based fuels—decaborane (B10H14) and hydrazine borane (N2H4BH3)—for practical applications. Operational tests reveal significant performance degradation in both direct decaborane fuel cells (DDFCs) and direct hydrazine borane fuel cells (DHBFCs). In DDFCs, a severe 81.6% loss of initial peak power density occurs within 1 h, mainly attributed to the structural instability of the anode catalyst layer and cathode catalyst poisoning. For DHBFCs, a 46.4% performance decline is observed in the same period, with the accumulation of electrochemical byproducts at both electrodes being the primary cause. To address these issues, various optimization strategies are used. For DDFCs, replacing the anode substrate, adjusting the ionomer/carbon ratio, and using a more poison‐resistant cathode catalyst prove effective. In the case of DHBFCs, improving the anode gas diffusion layer and adopting AEMs significantly enhance performance. After optimization, DDFCs exhibit only a 6.7% performance degradation over 50 h of operation, while DHBFCs retain 95.7% of their initial performance. These findings provide crucial insights into the degradation mechanisms and optimization approaches for B/N‐H‐based fuel cell systems, facilitating their potential application in practical energy scenarios. This study investigates durability challenges in direct liquid fuel cells using B/N‐H fuels (decaborane and hydrazine borane). Initial tests revealed rapid degradation (81.6% and 46.4% losses) due to electrode instability and product buildup. Optimizations (gas diffusion layer, ionomer/carbon ratio, and ion exchange membrane) significantly enhanced durability.

As a traditional fossil fuel, petroleum fuel is prone to spill fires during storage, transportation, and use, which poses a significant threat to the secure utilization of energy. This research aims to investigate the effect of porous media on the combustion characteristics of spill fire. Quartz sand (diameter is 1.5 mm) is selected as a porous material, and continuous oil spill fire experiments under different oil discharge rates (25–100 mL·min −1 ) are carried out on both smooth substrate and porous bed. The spread process, burning rate, flame height and spread speed are measured and analyzed. The results show that no burning layer shrinkage occurs during the spread process. There is a significant increase in the stable burning length and in the time required to reach the quasi-steady burning phase. The burning rate of spill fire on a porous bed is negatively correlated with the thickness of the sand layer and positively correlated with the oil discharge rate, but it is still lower than the burning rate of pool fire under the same equivalent diameter. Transformer oil spill fire propagation speed is divided into three stages: acceleration-uniform-deceleration. When the oil discharge rate is 50 mL·min −1 , the uniform propagation speed of flame is 0.55, 0.11 and 0.03 cm·s −1 respectively. Flame height is positively correlated with oil discharge rate and negatively correlated with sand thickness. Furthermore, a dimensionless coefficient, d * , is introduced to modify the flame height and burning rate models, and the correctness of the modified model is verified by experimental data. This study is informative for the safe use of liquid fuels.