Energy & Fuels
ISSN / EISSN : 0887-0624 / 1520-5029
Published by: American Chemical Society (ACS) (10.1021)
Total articles ≅ 18,697
Latest articles in this journal
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01684
This study presents a continuing effort to unravel the wax deposition mechanisms using a state-of-the-art microscopic in situ visualization technique. The investigation focuses on understanding the effect of the flow rate on the particulate deposition mechanism. The existence of the particulate deposition mechanism is proven by the presence of wax crystals at a distance more significant than the mass transfer boundary layer thickness calculated from the film mass transfer theory, reinforcing that molecular diffusion is not the only one responsible for wax deposition. The flow rate study presents a direct relation between the flow regime and the particulate deposition mechanism. The lower the Reynolds number, the stronger this mechanism is observed. Under laminar and transition flow regimes, the deposit thickness and growth rate of the deposit are considerably greater than those calculated under the turbulent flow regime. The number of available crystals at the boundary layer for different flow rates is qualitatively analyzed. It is concluded that, under laminar and transition conditions, a larger number of crystals is available for deposition compared to turbulent cases. This effect can be explained by the larger induced shear forces on the flow at higher Reynolds numbers.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01061
Furanic ethers including furfuryl ether (FE) and tetrahydrofurfuryl ether (TFE) are considered as boosters for raising the octane number and cetane number, respectively. In this work, heterogeneous catalysts are used to synthesize FE from furfuryl alcohol and are found to be effective, and then they hydrogenate FE into TFE. Among the solid acids including HZSM-5, SiO2–Al2O3, SiO2, and Al2O3, it was discovered that the SiO2–Al2O3 complex with about 2.0% Al2O3 content exhibited excellent activity with 69% ethyl furfuryl ether (EFE) yield achieved. SiO2–Al2O3 demonstrated a decrease in its activity after being recycled six times. However, after calcination, SiO2–Al2O3 regained its activity. SiO2–Al2O3 maintained its activity and stability due to the Lewis acid site and the large pore size. In situ hydrogenation of EFE into ethyl tetrahydrofuran ether was performed using Ru/C, Pd/C, Pd/Al2O3, Raney Ni, Ni/Al2O3, Ni/CeO2, and Ni/SiO2 catalysts. Only Raney Ni demonstrated both high activity and stability.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01214
Bio-oil from biomass pyrolysis is a promising alternative and clean source of biofuels, chemicals, and materials. Its chemical composition, physical and chemical properties, and multiphase behavior change over time, because of aging, which significantly affects its storage, handling, transportation, upgrading, and application. This Review focuses on studying bio-oil aging, and its outlook, primarily covering the following four components: (1) the chemical composition, physical and chemical properties, and multiphase behavior of bio-oil; (2) the indicators for measuring the degree of aging and aging characteristics, including physical and chemical properties change during long-term and accelerated aging of bio-oil; (3) the aging mechanisms and kinetics emphasizing the reactions during the aging process and different kinetic models based on different aging indicators; (4) the potential approaches to slowing bio-oil aging. This Review presents highlights in developing aging mechanisms and kinetics that will allow the reader to have an in-depth understanding of the effect of aging on bio-oil properties and the approaches to improve the resistance of bio-oil aging.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01582
The increasing demand of energy has expedited the research on developing low-cost and environment-friendly organic solar cells (EFOSCs). The commercial application of non-fullerene-fused ring electron acceptors (FREAs) having the 1,1-dicyanomethylene-3-indanone (IC) end group is limited due to the presence of two highly toxic −C≡N groups. This research projects the first theoretical design and exploration of environment-friendly groups transforming promising end-capped electron acceptor molecules for high-performance environment-friendly organic solar cells. For the first time, we developed FCO-based (acceptor–donor–acceptor (A–D–A)) type, novel W-shaped environment-friendly electron acceptor molecules (W1–W6) by modifying the toxic −C≡N group of FCO (reference synthesized molecule R) with three nontoxic electron-withdrawing (−CF3, −SO3H, −NO2) groups. Frontier molecular orbital (FMO) analysis, density of state (DOS) graphs, electron and hole reorganization energy (λe, λh), open-circuit voltage (Voc), transition energy, transition density matrix (TDM) analysis, and exciton-binding energy values of W1–W6 are computed and compared with those of the recently synthesized highly efficient FCO molecule. Results suggest that the photovoltaic, photophysical, and electronic properties of designed molecules W1–W6 are better than those of R. All developed molecules, especially W6, proved to be the preferable optoelectronic material for EFOSCs owing to their low-energy band gap (2.136 eV), highest λmax values of 709.25 and 792.08 nm in gas and chloroform, respectively, with lowest transition energy (1.75 eV), lowest electron mobility (λe = 0.007657 Eh) and hole mobility (λh = 0.006385 Eh), lowest binding energy (Eb = 0.072 eV), and 1.743 V value for open-circuit voltage (Voc) as compared to reference R as well as other developed molecules. Charge transfer analysis among the W6:PM6 blend proved the superposition of orbitals and successful transfer of charge from the highest occupied molecular orbital (HOMO) (PM6) to the lowest unoccupied molecular orbital (LUMO) (W6). Thus, the developed molecules (W1–W6) depicting outstanding optoelectronic properties are recommended as the best nontoxic alternative materials for developing efficient and environment-friendly organic solar cells.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c00960
The CO2 capture system based on the electrochemical desorption at room temperature and atmospheric pressure may solve the high regeneration energy consumption problem of the amine-based postcombustion CO2 capture technology. In our former work, 0.7 M Na2Q was used to absorb CO2, and the pH mediator, tiron (QH2), was used to adjust the pH of the solution during the redox process to desorb CO2 and regenerate the absorbent. However, the absorbent does not completely regenerate due to the poor reduction of Q. In this work, the regeneration of 0.05–0.7 M Na2Q and the modification of graphite felt (GF) electrodes were further investigated. The results show that the reproducibility and the cyclicality of the Na2Q solution with a lower concentration (0.1 M) are better than those of 0.7 M Na2Q under the same conditions. The GF electrodes after acid treatment, heat treatment, phosphorus-doped, or MnO2-modified improve their electrochemical activities under acidic and weakly alkaline conditions. Phosphorus-doped or MnO2-modified GF electrodes also significantly improve the redox reaction under strongly alkaline conditions. The process of CO2 capture combining the Na2Q regeneration with the CO2 absorption is proposed to improve the reducibility of Q. In addition, a possible electrochemical reaction process of the Na2Q system is proposed. QH2 is oxidized to produce Q, in which a 1,4-Michael reaction to produce sodium 1,2,4-trihydroxybenzene-3,5-disulfonate occurs. The byproduct tiron-o-quinone is also produced, which could further polymerize to form oligomers. During the reduction of high-concentration Na2Q, the oligomers precipitate out of the solution, resulting in inhibition of the reduction.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01488
A one-step synthesis of sheet-like RuS2 nanoarchitectures exhibiting traits of a potential cathode material for designing high-performance asymmetric supercapacitors (ASCs) is demonstrated. The synthesis includes direct sulfurization of RuO2 in an inert atmosphere at high temperature that results in densely packed nanosheets of RuS2 with a moderate surface area. Such a structure provides abundant sites for faradaic/non-faradaic reactions for energy storage while facilitating ion migration during charge/discharge processes. Furthered from these traits, the RuS2 electrode exhibits substantially enhanced electrochemical performance as compared to the RuO2 electrode. Detailed analyses suggest that the charge storage at higher scan rates is dominated by capacitive processes, while at lower scan rates, the diffusion-controlled process of charge storage in addition to the capacitive processes is responsible for increased capacitance. The as-assembled activated carbon//RuS2 ASC with an optimum cell voltage of 2 V in an aqueous electrolyte exhibits attractive energy-power combination with excellent cycling performance, which outperforms many other recently reported ASCs.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c00965
The aim of this study was to understand the impact of vacuum gas oil (VGO) properties on the deactivation rate of a hydrocracking catalyst (nickel–molybdenum sulfide dispersed on a carrier containing USY zeolite). For this purpose, two hydrotreated feeds of different densities, organic nitrogen (∼120–150 ppmw) and aromatic content, were hydrocracked under operating conditions that favor catalyst deactivation, that is, high temperature (T = 418 °C) and high space velocity (LHSV = 3 h–1). The catalyst performance was followed by measuring the VGO conversion (370 °C+ petroleum cut) and determining the apparent kinetic constants for the main hydrocracking reactions (cracking, hydrodenitrogenation, hydrodesulfurization, and aromatics hydrogenation). The experiments were stopped after different times on stream (either 6 or 30 days) in order to assess the evolution of the catalyst as a function of time. The spent catalysts, obtained from three different reactor locations, were characterized by elemental and textural analyses and by thermogravimetry to investigate the quantity and nature of the coke formed. Catalytic tests with different model compounds (toluene and n-heptane) were carried out to determine the residual activity of the hydrogenating and acid catalyst functions. It was found that, at the evaluated conditions, both the nature and the content of organic nitrogen and aromatics compounds of the feedstock have a determinant role in the deactivation rate. Organic nitrogen determines the ratio between available metal and acid sites. The aromatics generate coke precursors on the available acid sites. Both factors play a coupled role that promotes coke deposition on the catalyst surface, which leads to an increase in the deactivation rate on top of the end boiling point of the feed.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01399
A solid oxide fuel cell anode microstructure is obtained using X-ray technology. A complete three-dimensional (3D) and fine heterogeneous model is built on the basis of the microstructure. The difference between the simulation results of microscopic and macroscopic models is compared. The physical fields of the heterogeneous model are analyzed and the effects of operating conditions are investigated. The results show that the electrochemical reaction at three-phase boundaries does not cause a high concentration gradient in the pore phase. The H2 molar fraction and concentration overpotential almost linearly decrease with the anode depth. However, the decrease of the H2 molar fraction is small, indicating that fuel supply is sufficient. Compared with activation and ohmic overpotentials, the concentration overpotential is negligible. Given the heterogeneity of the microstructure, the physical fields of the anode would fluctuate. The higher the electrochemical reaction rate, the greater the fluctuation of the physical fields. As shown in the microscopic simulation result, the active thickness of the anode is expressed as the analytical function of the operating conditions and microstructure parameters. The active thickness increases with temperature and H2 molar fraction but slightly decreases with the total overpotential. The active thickness is analytically expressed as the function of electrode parameters and operating conditions, which can improve electrode design and optimization.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c01402
Lithium sulfur (Li-S) batteries with high theoretical energy density (∼2.5 kWh kg–1) and high theoretical gravimetric capacity (1672 mAh g–1) have drawn great attention as they are promising candidates for large-scale energy storage devices. Unfortunately, some technical obstacles hinder the practical application of Li-S batteries, such as the formation of polysulfide intermediates between the cathode and anode as well as the insulating nature of the sulfur cathode and other discharge products. Glass fiber (GF) separators provide some cavities to withstand the volume change of sulfur during cycling, leading to long-term cycling stability. Here, the application of polar materials with a novel liquid graphene oxide (L-GO) binder rather than the standard poly(vinylidene fluoride) (PVDF) binder as effective coatings on the GF separator of the Li-S cell has been developed to suppress the shuttle effect. The deposition of silicon dioxide (SiO2), titanium dioxide (TiO2), and poly(1,5-diaminoanthraquinone) (PDAAQ) with the L-GO binder on the GF separator was investigated with a polycarboxylate-functionalized graphene (PC-FGF/S) cathode and a Li metal anode. The cells with modified coatings and L-GO as an efficient binder could accelerate conversion of long-chain polysulfides to short-chain polysulfides and significantly suppress the polysulfide dissolution, resulting in capacity retentions of ∼1020, 1070, and 1190 mAh g–1 for the cells with SiO2/L-GO-, TiO2/L-GO-, and PDAAQ/L-GO-coated separators after 100 cycles. The results demonstrate that ultrathin SiO2-, TiO2-, and PDAAQ-containing coatings with the L-GO binder on the GF separator can drastically improve the cyclability of the Li-S cells even after a long cycling life.
Energy & Fuels; doi:10.1021/acs.energyfuels.1c02172