Fuel Processing Technology最新文献

Co-firing NH₃ with conventional hydrocarbon fuels is an important approach for reducing CO₂ emissions in existing combustion systems. Besides CO₂, the blending of NH₃ would also notably affect soot formation and its oxidation behaviors. In the present study, we focus on the effects of NH₃ on the nanostructure and oxidation characteristics of soot produced in diffusion flames of n-heptane/toluene mixtures. Two configurations of laminar co-flow diffusion flame, including both normal and inverse diffusion flames (NDF and IDFs), were used for investigation. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (Raman), and Thermogravimetric analysis (TGA) were employed for soot characterization. The HRTEM and Raman spectra showed that with the increase of NH₃ blending ratio, the fringe length (L_a) and the degree of graphitization decreased while the microcrystal tortuosity (T_f) increased. The results are in consistent with TGA analysis which suggests the promoting effects of NH₃ on the soot oxidation reactivity. Difference between NDF and IDF with respect to the soot nanostructure and oxidation activity were discussed. It is our hope that the present results could deepen our understanding on the effects of NH₃ on soot nanostructure and oxidation behavior and benefit the design of particulate filters for combustion devices fueled with hydrocarbon/NH₃ mixtures.

In the current study, we examined the impact of spark duration strategy on a large bore compression ignition engine fueled with propane direct injection. An artificial neural network also was used to forecast engine in-cylinder performance characteristics. A rapid compression and expansion machine (RCEM) with a spark plug was tested with a high-pressure direct injection propane of 200 bar. While the timing of the injection was set to 20 °CA bTDC, the spark duration can range from 0.7 to 5.0 milliseconds. Crank angle degree, pressure, ignition coil number and spark duration were used as input parameters in the ANN model to predict in-cylinder performance, while engine performance parameters such as heat release rate (HRR), turbulent kinetic energy (TKE), tumble ratio, indicated power, and combustion efficiency (${\eta }_c$) were used as output parameters. The ANN model was created using the neural network toolbox and standard backpropagation with the Levenberg-Marquardt training algorithm was used with the learning rate and training epochs of the ANN model set to 0.001 and 1000, respectively. The accuracy of the model was validated by comparing the predicted datasets with the experimental data. The five projected parameters of heat release rate (HRR), turbulent kinetic energy (TKE), tumble ratio, indicated power, and combustion efficiency (${\eta }_c$) showed $R^2$ values of 0.9833, 0.9860, 0.9728, 0.9807, 0.9052, and 0.9999, respectively, and $\mathrm{MSE}$ values of 0.1419, 0.0023, 0.6428, 0.0106, 0.0050, and 0.0134. The $R^2$ of the validation dataset was nearly 0.98, which is close to that of the training dataset. The coefficients of determination ($R^2$) were greater than 0.9 in the projected results, and the $\mathrm{MSE}$ was reasonably low, indicating that a predictive model based on ANN model could predict in-cylinder performance of a large bore compression ignition engine.

In this study, Co-based catalysts supported over Ti-Al oxide and promoted with La, Ce, Mg, and K metals were assessed for CO₂ reforming of methane reaction to produce syngas. Titania-alumina mixed oxide supports were prepared using the template-assisted-solvothermal method, and then Co and promotors were co-impregnated over the as-prepared support. Different characterizations of catalysts showed that variation in promotor metal impacts these catalysts' physical and chemical properties. The Ti-Al oxide support possessed the perfect hexagonal morphology. Potassium-promoted catalysts possessed the highest number of basic sites, whereas the La-promoted catalyst possessed the highest number of acidic sites. La promotion improved the Co dispersion, while Mg promotion enhanced the metal support integration. La-promoted catalysts are deactivated because of active metal oxidation and the generation of hard carbon. The carbon was deposited in all catalysts; however, the activity of the Mg-promoted catalyst was unaffected. The intermediate surface basicity and strong metal support interaction improved the Mg-promoted catalyst's stability. The La and Mg-promoted catalysts possessed lower apparent activation energies.

Numerous innovative low-carbon ironmaking technologies rely on the use of a high-temperature, highly reducing gas, with examples including the gas-based direct reduction approach, hydrogen-enriched blast furnace fuel injection, and hydrogen-rich carbon circulation oxygen blast furnaces. However, the process of obtaining high-temperature and highly reducing gases inevitably leads to carbon deposition, and effective methods for controlling carbon deposition have yet to be developed for practical applications. Thus, within the context of metallurgical process conditions, this article provides a comprehensive review of the advancements in carbon deposition research by integrating findings from the fields of fuel chemistry and carbon material synthesis. Initially, the thermodynamic fundamentals of the carbon deposition reactions are examined, and subsequently, the influences of temperature, H₂, and catalysis on the carbon deposition reactions are discussed. In addition, the growth and erosion mechanisms of carbon on the surface of the medium are analyzed. Finally, this review consolidates the methods available for controlling carbon deposition, encompassing changes in the process conditions, the development of anti-carbon materials, and research into special processes. This article also identifies gaps in the literature and outlines future directions in related fields, notably proposing the application prospects of the sulfur passivation and thermal plasma reforming technologies in the reforming and heating of highly reducing gases.

The high-value recycling of discarded phenol-formaldehyde resins (PF) remains an unresolved challenge. Herein, we propose a novel approach leveraging γ-Al₂O₃ to convert PF into high-value hexamethylbenzene at a low temperature using a one-pot method. This study explores the degradation capability of PF, methylation reaction efficiency, and hydrodeoxygenation capacity among various cost-effective commercial catalysts: γ-Al₂O₃, ZrO₂, and TiO₂. It reveals the influence of different reaction times on PF pyrolysis and product distribution, and it was found that high value-added hexamethylbenzene exhibited the highest yield (73.33 wt%) with selectivity (75.83%) using γ-Al₂O₃ at 350 °C and 2 h of reaction. Experiments using PF models demonstrate the crucial synergy between γ-Al₂O₃ and C(aryl)-OH in the cleavage of C(aryl)-C(alkyl) bonds and methylation reactions. A pathway for PF C-C/C-O bonds cleavage-methylation tandem reaction is proposed, based on ¹³C methanol isotope experiments. PF undergoes C(aryl)-C(alkyl) bond cleavage to produce phenolic intermediates, which were then methylated; this is accompanied by the cleavage of C(aryl)-OH and C(aryl)-OCH₃, culminating in C-alkylation to form hexamethylbenzene. This research provides new insights into the high-value recycling of PF.

The hydroisomerization of long-chain n-alkanes proves to be an effective approach for the production of renewable second-generation biodiesel, and the development of bifunctional catalysts with synergistic effect between metal and acidic sites was the key to increase the yield of iso‐alkanes. Herein, novel hierarchical SAPO-31 nanoparticles (S31-Hi) were synthesized with varied amounts of the growth inhibitor 1-octyl-3-methylimidazolium chloride ionic liquid (OMIMCl IL) in a one-stage crystallization, and a proposed formation process was discussed. The 0.1Pd/S31-Hi bifunctional catalysts were prepared by loading only 0.1 wt% Pd based on the S31-Hi by wetness impregnation method and their catalytic performances were evaluated for the hydroisomerization of n-hexadecane. The catalytic performance of 0.1Pd/S31-H based on the S31-H synthesized by adding an appropriate amount of OMIMCl ILs was significantly improved, which can be attributed to the enhanced diffusion originating from its smaller crystal size, higher Pd dispersion, and larger C_Pd/C_H+ value, which was beneficial for achieving synergistic catalysis. The iso‐hexadecane yield of 77.8% and proportion of multi-branched isomers of 51.5%, and catalytic stability within 100 h time on stream was obtained over the 0.1Pd/S31-H at n-hexadecane conversion of 89.3%. These catalysts have application potential for the production of second-generation clean biodiesel with excellent low temperature fluidity.

A new strategy for the transformation of an intermediate of the lignin conversion process, namely cyclohexanone, to fuel-grade products is assessed in this study. In this regard, the conventional hydrodeoxygenation process (with pure hydrogen) was compared to an innovative one with a simulated lignin-derived syngas stream in a wide range of reaction conditions (300–400 °C, 1–15 bar, and small-to-large feed-to-catalyst ratios) and over commercial molybdenum-based (nickle‑molybdenum (NiMo) and cobalt‑molybdenum(CoMo)) catalysts. Cyclohexanone conversion, product distribution, deoxygenation efficacy, and heating value were compared in each case. Cyclohexanone was transformed into cyclohexane, cyclohexene, benzene, cresols, phenol, toluene, and bi-cyclic compounds, which are beneficial in jet-fuel processing. Increasing the reaction temperature and pressure intensified the conversion of cyclohexanone (up to 87.8% conversion at 400 °C and 15 bar over both NiMo and CoMo catalysts), whereas increasing the feed-to-catalyst ratio reduced it. Operating conditions and the reducing gas (pure hydrogen or syngas) had major impacts on the conversion of cyclohexanone, deoxygenation efficiency, product distribution, and the heating value of the final product blend. The results of this study claim that cyclohexanone conversion to fuel-grade hydrocarbons (up to 97.61% over NiMo and 74.71% over CoMo catalysts) is a beneficial route and the conventional hydrodeoxygenation process can be replaced with the syngas-assisted one with a small change in production capacity, still large positive impact on the sustainability and environmental footprints of lignin conversion to biofuels.

In this study, a method was developed to calculate the radius of a spherical expanding flame, with the goal of mitigating the effects of the ignition electrode. This approach allows for a swift determination of the ignition electrode's influence on the spherical expanding flame. It also facilitates accurate computation of the flame radius and offers a systematic means to validate the derived laminar burning velocity. Using this method as a foundation, an evaluation system was established to examine factors that could impact the method's results. Findings suggest that the laminar burning velocity determined by this method aligns more closely with numerical simulations and experimental data from referenced studies. For spherical expanding flames with convex and concave contours near the ignition electrode, the mean flame radius decreases by 0.57% to 1.22% and increases by 1.37% to 2.95%, respectively.

Ammonia (NH₃) has gained increasing recognition as a carbon-free fuel. To enhance NH₃ combustion, reactive gases, like methane (CH₄), are usually added to the combustion system. In this work, the role of CH₄ in NH₃ combustion is systematically studied. A series of reactive force field molecular dynamic (ReaxFF MD) simulations are implemented to investigate effects of CH₄ addition on the consumption of NH₃ and the yields of nitrogen oxides (NO_x) from the atomic perspective: CH₄ accelerates the consumption of NH₃ by shortening the decomposition time of the first NH₃ molecule and increasing the translational kinetic energy of the system; CH₄ modifies the yield of NO_x by complicating the elementary reactions and introducing additional intermediates. The fuel ratio of CH₄ and NH₃ between 0.5 and 1 is suggested for a cleaner and enhanced NH₃ combustion. By summarising the findings from the latest publications and the present work, the role of CH₄ in NH₃ combustion is comprehensively analysed from the macroscale and microscale perspectives: CH₄ accelerates the progress of NH₃ combustion flame, activates chemical reactions, and aggravates NO_x emissions at a low CH₄ content. Taking the NH₃/CH₄ combustion as an example, this study provides an exclusive perspective to understand combustion phenomena from the microscale events to macroscale observations.

Hydrodeoxygenation (HDO) reactions are extensively employed in the conversion of biomass to advanced fuels, which rely heavily on bifunctional catalysts that contain both a metal component and an acidic component. A significant challenge in the development of HDO catalysts is the need to reduce costs while simultaneously enhancing catalytic efficiency. Here, a series of Ru@W/ZrO₂ catalysts with an extremely low loading of Ru (0.5 wt%) were successfully synthesized using different Ru or W loading sequences and different Ru/W mass ratios. The catalysts were applied in the HDO reaction of lignin-derived phenols, and their physical and chemical characteristics were revealed by various characterization techniques, including XRD, H₂-TPD, NH₃-TPD, and XPS. The results suggest that the synthesis method with post-loading Ru leads to improved exposure and utilization of the low-loaded Ru, which effectively serves as the active sites for hydrogenation in catalytic reactions. Under the same reaction conditions, the bifunctional catalyst with post-loading of Ru achieved a complete conversion of phenol into cyclohexane, while the catalyst with simultaneous loading of Ru and W only yielded 42% of cyclohexane. In addition, the Ru/W ratios have also shown significant effects on the HDO performance of the catalyst. The catalyst exhibits the highest hydrogenation activity when the Ru/W ratio is 10, which is further supported by kinetic experiments. This study highlights the significance of the loading sequence of noble metals and the metal/acid ratio in the synthesis of highly active bifunctional catalysts, and also lays the groundwork for the efficient utilization of noble metals in biomass HDO conversion.