Alcohol Fuels Research Articles

Reduction in PM and NOX of a diesel engine integrated with n-octanol fuel addition and exhaust gas recirculation

n-Octanol with its high energy density and high cetane number has similar fuel properties as diesel fuel, and is thus considered an excellent choice for alcohol fuels as a substitute for diesel. This study focused on the effects of exhaust gas recirculation (EGR) combined with the addition of n-octanol on the performance, emissions, and particulate matter (PM) of a direct injection diesel engine. The results show that the curves of the in-cylinder pressure of n-octanol/diesel blends nearly overlap those of pure diesel fuel under the test conditions. At a low EGR ratio, the brake thermal efficiency of n-octanol/diesel blends is higher than that of diesel fuel. With an increase in the EGR ratio, the results show that nitrogen oxide (NOX) emissions decrease, whereas carbon monoxide (CO) and soot emissions significantly increase. However, the use of n-octanol/diesel blends can inhibit the increase in CO and soot emissions appreciably. In addition, with an increase in n-octanol content in the blends, the number concentration of particles on the particle size distribution decreases gradually. To summarize, a simultaneous reduction in NOX and PM emissions under a combined operation of small EGR ratios and n-octanol blends can be realized, thereby improving the brake thermal efficiency.

Bio-inspired hydrophobicity promotes CO2 reduction on a Cu surface.

The aqueous electrocatalytic reduction of CO2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multicarbon products (C2/C3), but competing proton reduction to hydrogen is an ever-present drain on selectivity. Here, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained a 56% Faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO2 at the electrode-solution interface and consequently increase CO2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts.

Bifunctional Electrocatalyst of Pd-C@MoS₂-RGO Hybrid Nanostructures-Size Confined Green Synthesis for Direct Alcohol Fuel Cells.

The objective of the present study was to enhance physical interaction between noble metal catalysts (Pd QDs) and support (MoS₂/RGO) using in-situ carbon atom and improve its bifunctional activity towards alcohol oxidation and water oxidation. A few layers of two-dimensional MoS₂ nanosheets were synthesized over graphene oxide nanosheets via a simple one-pot green synthesis process. Pd QDs were then placed over MoS₂/RGO by a simple green process at room temperature. High resolution transmission electron microscopic (HR-TEM) images revealed that Pd QDs were uniformly distributed over MoS₂/RGO nanosheets and dark regions, confirming the existence of MoS₂ sheets over graphene sheets. The activity of low quantity Pd QDs (5 weight%) grafted MoS₂/RGO hybrid catalyst for electrocatalysis of alcohol and water oxidation reaction was tested. Improved catalytic activity and high peak current response of 11.2 mA cm-2 and 2 mA cm-2 were obtained towards methanol and ethylene glycol oxidation, respectively. Additionally, the oxidation of poisonous intermediates and water were tested with this electrode and enhanced catalytic activity was observed. These characteristic improvements of Pd QDs-MoS₂/RGO nanohybrid are due to the smaller size of Pd particles and effective interaction between MoS₂ and RGO. Therefore, the proposed catalyst could be a promising candidate as an anode material for energy conversion and storage.

Ultrafine bimetallic alloy supported on nitrogen doped reduced graphene oxide toward liquid-fuel oxidation: Profile of improved performance and extended durability

Herein, the ultrafine bimetallic alloy supported on nitrogen doped reduced graphene oxide (PtCu/NrGO) has been developed via wet-reflux strategy and applied as potential catalyst for electro-oxidation of liquid fuels in direct alcohol fuel cells (DAFCs). Possible conversion to PtCu/NrGO from the precursor materials was established in detail using transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photo electron spectroscopy (XPS). The coupled structure of PtCu along with NrGO endowed an efficient catalyst with excellent catalytic activity and stability toward electro-oxidation of various alcohols compared to commercial Pt/C in acidic electrolyte. PtCu/NrGO exhibits the mass activity of 0.917, 0.620 and 0.495 A/mgPt toward the electro-oxidation of methanol, ethylene glycol and glycerol, about 6.8, 6.3 and 8.6 fold increment compared to Pt/C catalyst, respectively. Besides, PtCu/NrGO shows excellent durability with less activity decay even after 500 cycles.

Comparative study of combustion process and cycle-by-cycle variations of spark-ignition engine fueled with pure methanol, ethanol, and n-butanol at various air–fuel ratios

The combustion characteristics and cycle-by-cycle variations of a spark-ignition engine fueled with pure methanol, ethanol, and n-butanol were comparatively analyzed. All experiments were performed using a natural gas/alcohols dual-fuel engine with the alcohol fuel energy substitution ratio of 100%. The engine was kept under a low load with a brake mean effective pressure of 0.387 MPa. Engine speed was kept constant at 1600 r/min and air–fuel ratio (λ) was set in the range of 1–1.5 and varied in intervals of 0.1. The results showed that the pure methanol fuel yielded the highest peak cylinder pressure (Pmax) and peak heat-release rate (HRRmax) of the engine, followed by ethanol and then n-butanol. Moreover, Pmax and HRRmax decreased with the increase in λ, and the corresponding crank angles were reduced for the three primary alcohol fuels. The flame-development and flame-propagation periods of methanol were shorter than those of ethanol and n-butanol. The indicated mean effective pressure (IMEP) was distributed in a wider range with the increase in λ for the engine fueled with ethanol and n-butanol. However, for methanol, the IMEP was distributed in a relatively narrow range under all conditions of λ. When λ was increased from 1.0 to 1.5, the coefficient of variation in IMEP (COVIMEP) of methanol increased from 1.36% to 2.65%, the COVIMEP of ethanol increased from 1.71% to 10.46%, and the COVIMEP of n-butanol increased from 2.06% to 15.66%. Thus, methanol had a higher burning rate, lower cycle-by-cycle variations, and a better lean-burn capability than that of ethanol and n-butanol.

Experimental and kinetic modeling study of n-propanol and i-propanol combustion: Flow reactor pyrolysis and laminar flame propagation

Flow reactor pyrolysis and laminar flame propagation are investigated for n-propanol and i-propanol, which are the smallest alcohol fuels with isomeric structures. Pyrolysis products of propanol isomers at 0.04–1 atm are detected using the synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental observations demonstrate ethylene and propene are respective dominant hydrocarbon products in the n-propanol and i-propanol pyrolysis, while the most abundant oxygenated products are formaldehyde, acetaldehyde and ethenol in the n-propanol pyrolysis and acetone and acetaldehyde in the i-propanol pyrolysis. Higher concentrations of aromatic and oxygenated pollutants are observed in the i-propanol pyrolysis. The laminar burning velocities of propanol isomers are measured in a high-pressure constant-volume cylindrical combustion vessel at the initial temperature of 423 K, pressures of 1–10 atm and equivalence ratios of 0.6–1.5. A general trend that n-propanol has much faster LBVs than i-propanol is noticed under all investigated conditions. A kinetic model of propanol isomers is developed and validated against the present experimental data, as well as other experimental data in literature covering wide ranges of temperatures, pressures and equivalence ratios. Rate of production analysis and sensitivity analysis are performed together to provide insight into the fuel isomeric effects on key reaction pathways and fuel reactivities. In the flow reactor pyrolysis, different dominant primary decomposition pathways of n-propanol and i-propanol lead to the differences in both molecular structures and concentration levels of pyrolysis products. In laminar flame propagation, different radical pool distributions of propanol isomers are illustrated and found to be largely influenced by fuel isomeric structures. The linear structure of n-propanol promotes the formation of more active radicals like formyl, vinyl and ethyl, while the branched structure of i-propanol facilitates the production of more stable radicals including methyl and allyl. Thus, the promoted chain-branching in n-propanol flames and enhanced chain-termination in i-propanol flames can explain the higher laminar burning velocities and reactivities of n-propanol than that of i-propanol.

高圧縮比小型直噴ディーゼル機関におけるHot EGR が 低級アルコール燃料の着火,燃焼特性および熱効率に及ぼす影響

高圧縮比小型直噴ディーゼル機関におけるHot EGR が 低級アルコール燃料の着火,燃焼特性および熱効率に及ぼす影響

An Overview of the Influence of Biodiesel, Alcohols, and Various Oxygenated Additives on the Particulate Matter Emissions from Diesel Engines

Rising pollution levels resulting from vehicular emissions and the depletion of petroleum-based fuels have left mankind in pursuit of alternatives. There are stringent regulations around the world to control the particulate matter (PM) emissions from internal combustion engines. To this end, researchers have been exploring different measures to reduce PM emissions such as using modern combustion techniques, after-treatment systems such as diesel particulate filter (DPF) and gasoline particulate filter (GPF), and alternative fuels. Alternative fuels such as biodiesel (derived from edible, nonedible, and waste resources), alcohol fuels (ethanol, n-butanol, and n-pentanol), and fuel additives have been investigated over the last decade. PM characterization and toxicity analysis is still growing as researchers are developing methodologies to reduce particle emissions using various approaches such as fuel modification and after-treatment devices. To address these aspects, this review paper studies the PM characteristics, health issues, PM physical and chemical properties, and the effect of alternative fuels such as biodiesel, alcohol fuels, and oxygenated additives on PM emissions from diesel engines. In addition, the correlation between physical and chemical properties of alternate fuels and the characteristics of PM emissions is explored.

Alcohol and alkane fuel performance for Gas Generator cycle Air Turbo Ramjet Engine

The present study investigates the feasibility of alcohol fuels for a Gas Generator cycle Air Turbo Ramjet (GG-ATR) Engine in comparison with alkane fuels. The alkane and alcohol fuels in the present study range from C1 species (CH4 and CH3OH) to C4 species (n-C4H10 and 1-C4H9OH).The present study analytically evaluates Specific thrust and Specific impulse (Isp) of GG-ATR engine as functions of gas generator combustion temperature. For both alcohols and alkanes, the peak Gas Generator (GG) combustion temperatures exist for specific thrust and ram combustor temperature. Comparing alcohol to alkane in the lower GG combustion temperature, specific thrusts and Isp of alcohol tend to be higher than those of C2H6, C3H8, and 1-C4H10. GG combustion gases for alcohol fuels contain higher mole fractions of H2O and CO2 than those for alkanes. Because of high mole fractions of H2O and CO2, the ratio of GG combustion gas for alcohols to air flow rate is fortunately close to the stoichiometric ratio, resulting in higher ram combustion temperature. The high ram combustion temperature can contribute to the higher specific thrust and Isp. Lower GG combustion temperature is preferable because of a thermal limit of a turbine blade. Thus, alcohols have superiorities to alkanes for the GG-ATR engine application.

Electro-catalytic Activity of Carbon Nanofibers Supported Palladium Nanoparticles for Direct Alcohol Fuel Cells in Alkaline Medium

Carbon nanofibers (CNFs) were successfully prepared employing a chemical vapor deposition method using chicken oil as a starting material. CNFs acquired from waste chicken fat represent a fascinating alternative to produce low-cost/cheap fuel cell electro-catalysts. The Pd/CNF electro-catalyst was synthesized using carbon nanofibers as a support material without adjusting the pH of the solution. The synthesized nanomaterials were studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Transmission electron microscopy (TEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The FTIR outcomes confirmed that the prepared carbon nanofibers are functionalized with carboxylic acid functional groups which enhance the dispersion of Pd nanoparticles. The Raman spectrum revealed that the synthesized CNFs contain two peaks D and G bands, which correspond to a disordered carbon peak (D) and graphite peak (G). TEM pictures confirmed that the synthesized nanomaterials were of the nanoscale and not uniformed in size. XRD peaks confirmed that the carbon nanofibers were amorphous and Pd (111) was observed in the Pd/CNF electro-catalyst. XPS results showed the composition of the prepared samples and the oxidation states of Pd in Pd/CNF electro-catalyst. The Pd/CNF electro-catalyst prepared by CVD method exhibits superior performance towards the electro-oxidation of ethanol and methanol as compared to the commercial palladium electro-catalyst.

On the microexplosion mechanisms of burning droplets blended with biodiesel and alcohol

Microexplosions are reported to occur frequently in droplet combustion of biodiesel mixed with alcohol, which are nominally miscible. We found, however, that they could be prevented if the standing time of fuel samples before burning was sufficiently long. To realize the microexplosion mechanisms, experiments based on suspending droplets and free-falling droplets were conducted. It was found that, before ignition, heterogeneous sites, which appeared similar to small drops, emerged from the droplet surface and subsequently merged into a bigger one, which then deposited at the bottom of the droplet. The diameter of this heterogeneous drop enlarged with increasing ambient humidity. At the same humidity, by using methanol, ethanol and isopropanol, respectively, the experiments showed that the merged heterogeneous drop of biodiesel/methanol was the largest and the smallest one was generated by that mixed with isopropanol. These heterogeneous sites were likely caused by the hygroscopic characteristics of alcohol fuels, which were supposed to mix well with biodiesel fuel and treated as a miscible blend in the first place. The miscibility, however, was destroyed by the absorbed water and phase separation occurred, leading to microexplosions when the droplet was burned. On the other hand, the interior heterogeneous drop vanished after sufficiently long time of standing prior to burning, and consequently no microexplosion was observed during the whole combustion process. For the mixture fuel of alcohol, methanol had higher propensity to absorb water and needed longer standing time for dissolution of the heterogeneous drop, as compared to ethanol and isopropanol, which had lower hygroscopicity. From the results, the heterogeneous sites inside the blended droplet were concluded unambiguously to be the primary cause of microexplosions during the combustion process, leading to the highest burning rate at equi-volume proportion of mixed fuels. In contrast, elimination of the heterogeneous sites in the burning droplets could prohibit microexplosions and yielded the highest burning rate at 25% fraction of alcohol.

Hard/Soft Template Synthesis of Mesoporous TiO2/Carbon Supports for Fuel Cells

Mesoporous carbons (MC) are attractive catalyst supports for polymer electrolyte membrane fuel cells (PEMFCs) applications because of their low cost, high surface area, good electrical conductivity, and high chemical stability under normal operating conditions.[1] However, carbon corrosion in the cathode compartment can result in a significant reduction in the catalyst electrochemical active surface area (ECSA), that it will negatively impact in the fuel cell performance.[2] Hence, alternative catalyst substrates with a greater chemical stability under acidic and oxidizing conditions have captured significant attention in recent years. [3,4] Among the most promising materials for PEMFCs are carbon nanotubes (CNTs), graphene, and hybrid core/shell metal oxide/mesoporous carbons (MOx/MC). Unfortunately, CNTs and graphene are still too expensive for this application, while studies on hybrid supports, in the case of metal oxides, were limited to low metal oxide contents due to the reduction on surface area observed after the deposition of metal oxide nanoparticles.[5,6] For that reason, the use of ordered mesoporous carbons obtained by carbonization of polymeric materials synthesized in the presence of soft-templates such as surfactants or polyelectrolytes[7] or silica nanoparticles as hard-templates[1] is quite attractive. It can contribute to produce chemically stable materials with an adequate surface area and pore size distribution, and these properties can be modified by merely varying the synthesis and carbonization conditions.[1,4,7] In this study, the effort was oriented to develop mesoporous carbons (MC), and hybrid TiO2/MC catalyst supports with high surface area and tailored micro-mesoporous structure. Carbon materials were obtained by carbonization of a resorcinol-formaldehyde resin synthesized in the presence of silica nanoparticles and poly(diallyldimethylammonium) chloride, a polyelectrolyte as soft template. The deposition of TiO2 nanoparticles was carried out using a sol-gel method that has shown to result in the formation of core/shell TiO2/carbon nanocomposite structures with low TiO2 segregation.[5,6] Both, MC and TiO2/MC substrates were decorated with Pt or PtRu catalyst nanoparticles using standard impregnation methods. The materials were characterized using standard methods (XRD, XPS, TEM, SEM, TGA, ICP-OES, and Raman spectroscopy). The catalytic activity of Pt and PtRu nanoparticles toward the oxygen reduction reaction (ORR), and the oxidation of methanol (MOR) was investigated using a number of electrochemical techniques in a three-electrode cell configuration. The improvement in the catalytic activity of Pt toward the ORR and the chemical stability were both assigned to the high BET surface area of the starting carbon materials (> 500 m2/g) that allowed working with high TiO2 loadings while still keeping a reasonable electrical conductivity. The high TiO2 content seems to improve the catalyst distribution on the support, and the contact between the TiO2 and Pt nanoparticles. Preliminary results for the oxidation of methanol on PtRu/TiO2/MC also show a significant improvement when compared to Pt/MC and Pt/TiO2/MC, but the changes are less significant when compared with PtRu/MC, however more studies are underway to confirm these findings. REFERENCES Forouzandeh F.; Banham D.W.; Feng F.; Li X.; Ye S.; Birss V., ECS Transactions 58 (1) 1739-1749 (2013).Shao Y.Y, Yin G.P., Zang , Gao Y.Z., Electrochim. Acta 51, 5853 (2006).Wang Y-J, Wilkinson D.P., Zhang J., Chem. Rev. 111 (12) 7625-7651 (2011).Bruno M., Viva F.A., Carbon Materials for Fuel Cells BT - Direct Alcohol Fuel Cells: Materials, Performance, Durability and Applications, in: H.R. Corti, E.R. Gonzalez (Eds.), Springer Netherlands, Dordrecht, pp. 231–270 (2014).Odetola C.; Trevani L.; Easton E., Power Sources 294, 254–263 (2015).Odetola C., Easton E.B., Trevani L., J. Hydrogen Energy 41, 8199–8208 (2016)Bruno M.; Viva F.; Petruccelli M.; Corti H., Power Sources 278, 458–463 (2015).

Study of Alternative Fuels and Their Knock Behavior and Various Suppression Methods for Engine Knock

A research in knocking combustion is indispensable because it determines the engine’s durability, fuel consumption, power density as well as its noise and emission performance. In highly boosted spark ignition engines with random pre-ignition events, knocking has been intensively studied both in academia and industries. Ultimately conventional knock in SI engines are reviewed by the suppression methods including the use of injection strategy, knock sensor, and exhaust gas recirculation (EGR). With the population increasing at an ever alarming rate, the world has seen a tremendous increase in the prices of fossil fuels, and are skyrocketing day-by-day. With an incessant consumption of fossil fuels, the global temperature is on the rise either, and we are already on course of achieving the average global temperature of 1.5°C. Considering the unexpected changes in Earth’s weather patterns, switching to alternative fuels would indubitably play a cardinal role in attenuating both – climate catastrophe and toxic gases – such as CO, CO2, NOx, etc., which envenoms the air quality. This paper presents the manoeuvre and origin of the use of alternative fuels in spark ignition engines. We have held accountable three types of fuels - alcoholic fuels, gaseous fuels, and liquid fuels. Additionally this work shows the research directions for the usage of alternative fuels in vehicles powered by spark ignition engines and finally the value of Octane Index of Alcohol-Gasoline blend under particular operating conditions has also been analyzed.

A comparative study on the combustion and emissions of dual-fuel engine fueled with natural gas/methanol, natural gas/ethanol, and natural gas/n-butanol

• Primary alcohol fuels support faster flame development and flame propagation. • Primary alcohol fuels reduce total hydrocarbon and nitrogen oxide emissions. • Methanol has advantages over ethanol and n-butanol in increasing η et . • Adding methanol produces smaller regulated emissions than ethanol and n-butanol. The effects of the addition of primary alcohol fuels (methanol, ethanol, and n-butanol) on the combustion characteristics and performance of natural gas engines are examined by experimentation with a dual-fuel test engine, followed by a comparative analysis of the test results. The test engine was operated under a light load, at a fixed speed of 1600 rpm, and with a brake mean effective pressure of 0.387 MPa. The air-fuel ratio was held constant at the stoichiometric equivalent ratio. The engine performance was analyzed for different natural gas/alcohol fuel mixtures by using four alcohol fuel energy substitute ratios (AESRs): 0% (pure natural gas), 19%, 44%, and 60%. The experimental results indicate that faster burning rates can be obtained by mixing any of the three alcohol fuels with natural gas, compared with pure natural gas. Further, by increasing the AESR, faster flame development and flame propagation times can be obtained, and the crank angle when 50% of the mass is burned approaches the top dead center position. These outcomes lead to an advance in combustion phasing. The addition of primary alcohol fuels in the dual-fuel mode can also reduce total hydrocarbon and nitrogen oxide emissions. Moreover, the brake thermal efficiency of natural gas can be improved significantly by adding methanol, whereas negligible improvements in this aspect are obtained by adding ethanol and n-butanol. The comparative analysis indicates that methanol addition has advantages over ethanol and n-butanol additions in increasing the brake thermal efficiency and reducing the regulated emissions of natural gas engines.

Experimental investigation of iso-butanol/diesel reactivity controlled compression ignition combustion in a non-road diesel engine

As non-road engine emission control programs are developed largely in number of countries around the world, adopting a high efficiency and low emission combustion techniques has become essential. Flexible fuel operation using in-cylinder blending technique is a primary option for using higher octane fuel in a non-road diesel engine to mitigate emissions and fossil fuel dependency. In the present study, iso-butanol/diesel dual fuel reactivity controlled compression ignition concept is preferred considering the benefits of iso-butanol over other alcohol fuels and better combustion control over other low temperature combustion concepts. An experimental investigation is performed on a suitably modified single cylinder non-road diesel engine for the entire load range (0–100% engine full load) focusing on the effect of operating parameters (iso-butanol mass fraction, diesel injection timing, diesel injection pressure, diesel mass in split injection, and intake air temperature) on the dual fuel combustion, performance and emission characteristics. The reactivity controlled compression ignition combustion is analyzed at each load condition and the best operating points are selected based on brake thermal efficiency and emissions. The results indicated that increase in iso-butanol mass fraction with advanced start of injection of direct injected diesel fuel showed a 99% reduction in oxides of nitrogen and a 91% reduction in smoke emissions with 4.5% increase in brake thermal efficiency. Further the drawback in dual fuel combustion, hydrocarbon emission is reduced by 65% with an increase of intake air temperature from 303 K to 338 K. Also, both hydrocarbon and carbon monoxide emissions are reduced with increase in diesel injection pressure and mass of diesel fuel injected in first injection due to the enhanced mixture formation.

Comparative Analysis of the Combustion Stability of Diesel-Methanol and Diesel-Ethanol in a Dual Fuel Engine

The co-combustion of diesel with alcohol fuels in a compression ignition dual fuel engine is one of the ways of using alternative fuels to power combustion engines. Scientific explorations in this respect should not only concern the combustion process in one engine cycle, which is most often not representative for a longer engine life, but should also include an analysis of multiple cycles, which would allow for indicating reliable parameters of engine operation and its stability. This paper presents experimental examinations of a CI engine with a dual fuel system, in which co-combustion was performed for diesel and two alcohol fuels (methanol and ethanol) with energy contents of 20%, 30%, 40% and 50%. The research included the analysis of the combustion process and the analysis of cycle-by-cycle variation of the 200 subsequent engine operation cycles. It was shown that the presence and increase in the share of methanol and ethanol used for co-combustion with diesel fuel causes an increase in ignition delay and increases the heat release rate and maximum combustion pressure values. A larger ignition delay is observed for co-combustion with methanol. Based on changes in the coefficient of variation of the indicated mean effective pressure (COVIMEP) and the function of probability density of the indicated mean effective pressure (f(IMEP)), prepared for a series of engine operation cycles, it can be stated that the increase in the percentage of alcohol fuel used for co-combustion with diesel fuel does not impair combustion stability. For the highest percentage of alcohol fuel (50%), the co-combustion of diesel with methanol shows a better stability.

Ultrafine Pt Nanoparticles Stabilized by MoS2/N-Doped Reduced Graphene Oxide as a Durable Electrocatalyst for Alcohol Oxidation and Oxygen Reduction Reactions.

Direct alcohol fuel cells play a pivotal role in the synthesis of catalysts because of their low cost, high catalytic activity, and long durability in half-cell reactions, which include anode (alcohol oxidation) and cathode (oxygen reduction) reactions. However, platinum catalysts suffer from CO tolerance, which affects their stability. The present study focuses on ultrafine Pt nanoparticles stabilized by flowerlike MoS2/N-doped reduced graphene oxide (Pt@MoS2/NrGO) architecture, developed via a facile and cost-competitive approach that was performed through the hydrothermal method followed by the wet-reflux strategy. Fourier transform infrared spectra, X-ray diffraction patterns, Raman spectra, X-ray photoelectron spectra, field-emission scanning electron microscopy, and transmission electron microscopy verified the conversion to Pt@MoS2/NrGO. Pt@MoS2/NrGO was applied as a potential electrocatalyst toward the anode reaction (liquid fuel oxidation) and the cathode reaction (oxygen reduction). In the anode reaction, Pt@MoS2/NrGO showed superior activity toward electro-oxidation of methanol, ethylene glycol, and glycerol with mass activities of 448.0, 158.0, and 147.0 mA/mgPt, respectively, approximately 4.14, 2.82, and 3.34 times that of a commercial Pt-C (20%) catalyst. The durability of the Pt@MoS2/NrGO catalyst was tested via 500 potential cycles, demonstrating less than 20% of catalytic activity loss for alcohol fuels. In the cathode reaction, oxygen reduction reaction results showed excellent catalytic activity with higher half-wave potential at 0.895 V versus a reversible hydrogen electrode for Pt@MoS2/NrGO. The durability of the Pt@MoS2/NrGO catalyst was tested via 30 000 potential cycles and showed only 15 mV reduction in the half-wave potential, whereas the Pt@NrGO and Pt-C catalysts experienced a much greater shift (Pt@NrGO, ∼23 mV; Pt-C, ∼20 mV).

The Catalytic Activity of Pt:Ru Nanoparticles for Ethylene Glycol and Ethanol Electrooxidation in a Direct Alcohol Fuel Cell

In this study, we investigated the carbon-supported PtRu nanoparticles with atomic ratios of Pt:Ru of 100:0, 90:10, 70:30, and 50:50 for ethanol and ethylene glycol electrooxidation in alkaline media. The nanoparticles were synthesized using sodium borohydride method with 20 wt% of metals loading on carbon. The nanoparticle mean sizes were 7.3 nm, 5.7 nm, 5.2 nm, and 5.1 nm for Pt/C, Pt90Ru10/C, Pt70Ru30/C, and Pt50Ru50/C, respectively. X-ray diffraction (XRD) analysis revealed that Pt and PtRu electrocatalysts have face-centered cubic (fcc) structure and suggests the alloy formation for all PtRu/C materials, which was further supported by the X-ray photoelectron spectroscopy (XPS). Based on XPS analysis, Pt50Ru50/C has higher amount of Pt oxides on the surface than Pt70Ru30/C. Electrochemical results demonstrated that the addition of Ru to Pt enhances the catalytic activity towards ethanol and ethylene glycol electrooxidadion. The catalyst of Pt50Ru50/C composition showed the lowest onset potential for ethanol and ethylene glycol electrooxidation, which were 160 and 70 mV lower than for Pt/C, respectively. Furthermore, this catalyst outperformed Pt/C and other PtRu/C compositions in chronoamperometric and direct alcohol fuel cell (DAFC) experiments. DAFC experiments using Pt50Ru50/C as anode had the power density 40 and 14% higher than using Pt/C for ethanol and ethylene glycol, respectively. The promotion is due to the bi-functional mechanism and/or electronic effect of two metals in the alloy.

Numerical Prediction of Mixture Formation Process of an Ethanol Spray in a Rapid Compression and Expansion Machine

This study deals with the development of controlled-ignition technology for high performance compression ignition alcohol engines. Among the alcohol fuels, we focused on Ethanol as a promising candidate of alternative fuels replacing from petroleum. In our previous study, visualization tests of spray mixture formation process up to auto-ignition for Ethanol-Diethyl either blend fuels had been conducted by using a constant volume electrical heating combustion chamber. Quantitative evaluation of auto-ignition quality was summarized in a form of 3D map that indicates the effects of surrounding gas pressure, temperature and Oxygen concentration on ignition delay. However, maximum surrounding gas pressure in the experiments was 2.8MPa much less than that of real engine due to the structure of the combustion chamber. As the next step, we originally designed and manufactured a RCEM (Rapid Compression and Expansion Machine with variable compression ratio) in order to investigate the mixture formation process up to auto-ignition of an Ethanol spray under surrounding gas conditions similar to real engine operating conditions with the consideration of the interaction between fluid motion of surrounding gas and fuel injection. Prior to carrying out the experiments, we numerically predicted the auto-ignition quality of an Ethanol spray in the rapid compression and expansion machine. One of the commercial CFD codes; CONVERGE was used in the computational calculation with the considerations of turbulence, atomization, evaporation and detailed chemical reaction. Effect of fluid motion and surrounding gas pressure and temperature inside the combustion chamber of the RCEM on an Ethanol spray mixture formation is mainly discussed in this paper.

Operation of a diesel engine with intake manifold alcohol injection

The usage of ethanol and two different mixtures of ethanol and gasoline (E85 and E65) was investigated on a modified diesel engine designed to work in a dual-fuel combustion mode with intake manifold alcohol injection. The tests were conducted at five operating points covering low, medium and high load and different engine speeds. Additionally, an engine-process simulation model was built for the test engine and selected operating points from the engine test bed measurements were analysed with it. The discussion of the simulation results allows an efficiency analysis and therefore a better understanding of the findings of the engine test stand experiments. With rising alcohol amount, a significant reduction of soot mass and particle count was observed at all operating points. At some load conditions, substituting diesel with ethanol, E65 or E85 led to a reduction of the NOx emissions; however, the real benefit concerning the nitrogen oxides was introduced by the mitigation of the soot–NOx trade-off. The indicated engine efficiency in dual-fuel mode showed an extended tolerance against high EGR rates. It was significantly improved with enhanced substitution ratios at high loads, whereas it dropped at low loads. Substituting diesel with manifold injected alcoholic fuels impressively reduced the engine CO2 emissions at medium and high load operating points. Degrading combustion quality, irregular combustion phenomena and poor process controllability at low load and knock as well as auto-ignition at high load limited the maximum ethanol energy share to approximately 70% and 30%, respectively.