Hydrous EthanolâDieselâAl2O3 Nanoemulsified Fuel

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Hydrous ethanol – diesel – AlO nano emulsified fuel characterization, stability and corrosion effect Vishal Vasistha, and Rabinder Singh Bharj Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b00049 • Publication Date (Web): 08 Jul 2019 Downloaded from pubs.acs.org on July 17, 2019

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Hydrous ethanol – diesel – Al2O3 nano emulsified fuel characterization, stability and corrosion effect First author* (Corresponding Author) Vishal Vasistha Research Scholar, Department of Mechanical Engineering, Dr B. R. Ambedkar National Institute of Technology Jalandhar, Punjab, India – 144011, Email: [email protected], Contact No: +919056577596 Second author Dr Rabinder Singh Bharj Associate Professor, Department of Mechanical Engineering, Dr B. R. Ambedkar National Institute of Technology Jalandhar, Punjab, India – 144011 Email: [email protected], Contact No: +919779284553

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GRAPHICAL ABSTRACT

ABSTRACT The aim of the present work is to study the stability aspect of hydrous ethanol-diesel-Al2O3 nano (HEDA) emulsified fuel and its corrosive effect on different metals along with measurement of its physico-chemical properties: density, specific gravity, kinematic viscosity, phase separation layer, pH value, and colour. The freeze-thaw cycles were used as a storage condition to analyze the stability measures. The close and open cap static immersion methods were used to study the corrosion effect on aluminium, stainless steel and mild steel via weight loss technique. The results reported an increase in the density, specific gravity and kinematic viscosity while a decrease in the stability with an increase in water and ethanol percentage in the HEDA emulsion, without the formation of a phase separation layer. The highest water containing emulsion 2 ACS Paragon Plus Environment

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category (W20) was reported to be the least stable on the basis of stability test results, out of which W20H20D80 was noticed to be the most unstable, while W5H10D90 was observed to be the most stable HEDA emulsion. The static immersion open cap condition showed a greater corrosive effect than the close cap condition. Mild steel is not recommended to manufacture fuel system components of a diesel engine if HEDA emulsion is used as a fuel. The HEDA emulsified fuel combustion can exhibit a toxic effect on living beings and the environment in the prolonged period of time. KEYWORDS Hydrous ethanol, Corrosion, Stability, Emulsion, Surfactant, Al2O3 nano particles INTRODUCTION In the current scenario, environmental degradation and diminishment of earthborn fossil fuels are stimulating the world’s desire to discover novel, effective and efficient alternate renewable fuels. Biofuels might be an answer to this quandary, but their commercialization in the developing and under-developed nations is restricted due to their high production cost, low storage stability and inadequate feedstock availability. Emulsified fuels seem to be the best solution for such challenges. The storage stability plays a significant role in the selection of a suitable alternative fuel. The poor stability of the fuel can corrode the fuel system components and/or impact the function of fuel. A surfactant can improve the stability of an emulsion by reducing the surface tension between its immiscible layers. The former studies related to the present work can be divided into three categories: (1) Characterization, (2) Stability, and (3) Corrosion effect.


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(1) Characterization El-Din and his research group prepared water-in-diesel nano emulsions using the combination of surfactants Span 80 and Tween 80 and measured the physical properties of density and viscosity. They observed an increase in density and viscosity at any particular temperature with an increase in water concentration in water-in-diesel emulsions 3. Water has a much higher density than mineral diesel, which could possibly enhance the density and viscosity of water-in-diesel emulsion, compared to neat diesel. Taib et al. investigated the effect of palm methyl ester addition in diesel-ethanol blended fuel and found an increase in density, viscosity and heating value 6. A decrease in density and viscosity of ethanol-diesel blends was reported with an increase in ethanol concentration 8, 17. A lower value of the density of ethanol might have resulted in decreased density and viscosity of ethanol-diesel blends. The characterization of diesel-biodiesel-ethanol blend showed a decrease in density and kinematic viscosity with an increase in ethanol concentration 12, 13. (2) Stability Basha and Anand 1 reported five day’s storage stability of water (15%)-diesel (83%) and water- diesel-alumina nano (25/50/100 ppm) emulsified fuel using 2% surfactant mixture of Span 80 and Tween 80. The higher content of water, mixing with diesel emulsified fuel, may reduce the storage stability period because surfactant molecules may not be sufficient to combine with all water molecules. The metal oxide nano particles tend to settle down very soon in the absence of surfactant. Patil et al. used the same surfactant mixture to create the most stable water-in-diesel emulsified fuel 2. The combination of two or more surfactants was found to be more effective than an individual surfactant. The synergistic effect of a mixed surfactant system could possibly reduce surface and interfacial tension between different compounds of an 4 ACS Paragon Plus Environment

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emulsion, which could result in an improvement in the stability of the emulsion. The synergistic effect represents an attractive interaction between hydrophilic and hydrophobic groups of different compounds of an emulsion 3. Sajeevan et al. used 2% dodecenyl succinic anhydride surfactant to achieve stable cerium oxide nano-blended diesel fuel 4. Ghannam et al. utilized 2% Triton X-100 to get the most stable water-in-diesel emulsion 5. In general, 2% surfactant was optimized to achieve the highest emulsion stability for water-in-oil (w/o) emulsions 1, 4-5. The different emulsion categories may require different amounts of surfactant. The lower quantity of surfactant may not be adequate to stabilize an emulsion or to achieve the optimum stability of an emulsion. The higher quantity of surfactant (> 2%) would not improve the stability further because optimum stability was achieved using 2% surfactant, but the viscosity and the cost of the emulsion could be increased. The increased viscosity may create an improper fuel injection into an engine, which may result in engine performance retardation. The increased cost may put a barrier for the fuel to be commercialized. The emulsion stability is affected by various factors such as stirrer speed and time, surfactant concentration, and temperature. The emulsion stability may get affected at lower temperatures, especially in winter season, so some kind of provision has to be made for maintaining an optimum temperature of the emulsion to avoid the undesirable thermal effect on its stability. The temperature range greater than optimum temperature can cause wastage of energy. The mixing speed, time and hydrophilic-lipophilic balance (HLB) value were optimized as 5000 rpm, 20 minutes and 9 respectively 2. All the emulsion categories have been assigned a particular HLB value range to achieve the optimum stability and its 8-12 for water-in-oil (w/o) emulsion category. In the present study, the HEDA emulsion is treated as w/o emulsion. Water-in-diesel nanoemulsion stability was increased with an increasing surfactant concentration with lower water content 3. The stability of diesel-hydrous ethanol-palm


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methyl ester blends was changed with respect to the temperature and ethanol content 6. The ethanol concentration may suppose to affect the hydrogen bonding between ethanol and other compounds of blend. Thus, it can be predicted that the stability of proposed HEDA emulsified fuel may change with ethanol concentration. The emulsion stability improvement was reported with an increased stirring time, sonication duration and surfactant concentration 7, but at the same time, it consumed a lot of input energy. This energy could be calculated to decide the commercial cost of the emulsion. A variation in temperature and the percentage of blend constituent's had a significant effect on the alcohol-diesel and ethanol-biodiesel-diesel blend stability 8-9. It was observed that an increase in stirrer speed, diesel to water concentration and emulsification time improved the water-in-diesel emulsion stability 10. The use of water and low temperature accelerated a phase separation in the diesel-bioethanol fuel blends 11. The high ethanol content in the emulsified fuel reduced its storage stability 8-9, 11-13. Biodiesels were used as a part of the emulsified fuel where they performed as the emulsion stabilizer 6, 9, 12-14. The mixing of biodiesels prevents the use of expensive commercial surfactant but they have to be used in higher concentration to maintain emulsion stability that further restricts their implementation in diesel engines. It is due to their high viscosity characteristic which does not comply with fuel injection regulations. Lapuerta and his research group studied the different types of phase separation for ethanol-diesel and ethanol-biodiesel-diesel blends 9. The palm oil blended micro-emulsions were found to be more stable compared to canola and algae vegetable oil emulsions 14. The effect of metal nano particles was studied on the stability of emulsified fuels 1, 4, 7. The dynamic light scattering results reported the cerium oxide nano blended diesel fuel with 35 ppm cerium oxide nano particles as the most stable fuel 4. The metal nano particles have a great 6 ACS Paragon Plus Environment

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impact on the stability of emulsified fuel because of their small size and high surface area characteristic but their optimum concentration to be mixed with the fuel has to be determined. A very low or high quantity could have an adverse effect on the stability of the fuel. A higher concentration of metal nano particles will certainly increase the cost of emulsified fuel. Abdalla and his research group 7 studied the stability aspect of different nano metals with diesel and biodiesel blends. The blends were stable only for two weeks. The short-chain alcohol-diesel blends showed poor stability. The butanol-diesel blend showed better stability than ethanol-diesel blend 15-16. The hydrous/anhydrous ethanol-ethyl acetate-diesel micro-emulsions have been stabilized for the temperature range of 5 - 45°C using ethyl acetate as a surfactant 17. (3) Corrosion effect Low et al. performed the corrosion detection checks on aluminium, stainless steel and mild steel, which were immersed in Tri-fuel (diesel-biodiesel-ethanol) for two months and two weeks. A little weight loss was detected in each metal 13. From the literature review, it is apparent that the addition of surfactants can improve the stability of diesel emulsified fuels. Generally, 2% surfactant concentration is used to achieve the maximum stability for w/o emulsions 1, 4-5. The HEDA emulsified fuel comes under the category of w/o emulsions. For other emulsion categories, surfactant concentration may vary. Stirring speed, temperature, process duration, surfactant quantity and percentage of fuel constituents also affect the stability of emulsified fuels 2-3, 6-11. The present research focuses on the storage stability and the corrosive effects of hydrous ethanol-diesel-Al2O3 nano emulsified fuel. To our knowledge, no reports currently exist on this particular type of emulsified fuel formulation. A novel HEDA emulsion preparation method has 7 ACS Paragon Plus Environment

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been designed to maximize the storage stability. Firstly, the different coloured sediments (obtained from centrifuge test) have been discussed. The sediment colour may help to detect the reason behind its formation 39. A particular colour of the sediment could be formed due to the respective colour of some HEDA emulsion constituents like Al2O3 nano particles and surfactant. Thus, the formation of sediments can be avoided by proper mixing of that particular coloured constituent. This research paper presents a new concept of adding hydrophobic alumina nano particles to hydrous ethanol-diesel emulsion. The novel hydrogen bonding mechanisms of HEDA emulsified fuel formulation have been discussed. The formation of metal corrosion in the form of metal oxides has been presented via chemical reactions between metal and oxygen obtained from atmosphere/sample container/HEDA emulsion. A series of experiments (with varying agitation time and speed, ultrasonication duration and process steps) has been performed to optimize the HEDA emulsified fuel preparation method. This optimization can enhance the storage stability. The increased storage stability may result in less corrosion due to little contamination. MATERIALS AND METHODS Materials Al2O3 nano powder 1, 36, 37 was obtained from Nano Partech, Chandigarh, India. Ethanol (analytical grade) 15, 16 was received from Merck, Germany. The purity of ethanol was ≥ 99.9% and the water content in ethanol was ≤ 0.1%. Span 80 and Tween 80 1, 2, 24, 25 were bought from Oxford Laboratory, Mumbai, India. Triple deionized water (reagent grade) 28 was collected from Organo Biotech Laboratories Pvt. Ltd., Mumbai, India. Aluminium, stainless steel and mild steel 8 ACS Paragon Plus Environment

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pieces were procured from a potential supplier in Jalandhar, India. The specifications of Span 80, Tween 80 and ethanol are listed in Table 1. Hydrous ethanol was used as 5-20% (w/w) of the HEDA emulsion with an increment of 5%. Triple deionized water was used as 5-20% (w/w) of the hydrous ethanol in HEDA emulsion with an increment of 5%. The surfactant was mixed as 2% (w/w) of HEDA emulsion as optimized and duly reported by Patil et al. 2 and Ghannam et al. 5

. In the above statements, w/w means weight/weight basis (dispersed and continuous phase

percentages are calculated on a weight basis). Al2O3 nano particles were added in the fixed quantity of 100 ppm to each HEDA emulsion. An increased dosing level of nano particles may increase the viscosity of emulsion and chances of agglomeration 4, 7. The lesser cost and better heat transfer characteristics of Al2O3 nano particles encouraged its usage among all other nano metal additives 18. Triple deionized water was free from minerals to give the accurate results. The properties of Al2O3 nano particles are shown in Table 2. Emulsified Fuel Preparation Method The HEDA emulsions were prepared in five stages, as shown in Fig. 1. In the first stage, Span 80 (HLB - 4.3) and Tween 80 (HLB - 15) surfactants were mixed with the help of ultrasonicator at 40 kHz frequency and 30°C temperature for 30 minutes to make the mixture homogeneous. The mixture of low and high HLB value surfactants showed better emulsion stability 2. The ratio of Span 80 to Tween 80 was selected as 1.273:1 to achieve the HLB value of 9 to make the emulsion most stable 5. The ratio was calculated in the similar way as done by Croda Europe Ltd. 24

. The chemical structure of both the surfactants is in the form of head (Hydrophilic region) and

tail (Hydrophobic region), as depicted in Fig. 2. Tail hydrocarbon chain (Oleic acid) has common chemical structure in both the surfactants while head part has sorbitan and polyethoxylated sorbitan chemical group in Span 80 and Tween 80, respectively. Tween 80 9 ACS Paragon Plus Environment

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surfactant has such a complex structure that it can be mixed with Span 80 only via hydrogen bonding between them 25. A brown viscous solution was obtained in the first stage. During the second stage, diesel, ethanol and surfactant mixture were blended according to the emulsion specifications (Table 3), using mechanical stirrer at 1200 rpm and 30°C for 10 minutes. Hydroxyl (-OH) group of ethanol is polar, which represents hydrophilic nature of ethanol, while carbon chain is non-polar and hydrophobic. In general, higher carbon chain compounds show higher hydrophobicity. As carbon chain increases in alcohols, hydrophobic nature dominates over hydrophilic nature. But in ethanol, carbon chain is short, so it behaves as a hydrophilic substance. The same nature groups of substances make hydrogen bonds together, i.e. hydrophilic-hydrophilic bond and hydrophobic-hydrophobic bond. Thus, ethanol molecules are more likely to bond with hydrophilic group of Span 80 and Tween 80 molecules while diesel (n-cetane) is possibly attached with hydrophobic group of Span 80 and Tween 80 surfactant molecules, as shown in Fig. 2. A white coloured solution was obtained in the second stage. Further, in the third stage, the agitation speed was increased to 5000 rpm for the next 20 minutes, along with the addition of water. Water molecules are attracted towards hydrophilic (water loving) regions of Span 80 and Tween 80 emulsifiers and hydrogen bond is formed between them, as shown in Fig. 3. The third stage process generated additional foam compared to the second stage solution. In the next stage, Al2O3 nano particles were added with the aid of ultrasonicator, at 40 KHz and 30°C for 30 minutes. The ultrasonication technique is best suited to mix nano particles to avoid agglomeration. Al2O3 nano particles are hydrophobic in nature and are likely to be attached with hydrophobic portion of emulsifiers Span 80 and Tween 80, as represented in Fig. 3. At last, the


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HEDA emulsion was agitated once more at 5000 rpm and 30°C for 20 minutes to make it more uniform and stable. A uniform temperature of 30°C was maintained throughout the emulsion formulation process to avoid emulsion instability due to temperature variation. During emulsion formulation, it was observed that the lower range of temperatures ( 20°C) created difficulty in its formation, especially for the highest water containing emulsion category. It is because the larger amount of water produced higher cooling effect due to high latent heat of vaporization of water. The final emulsion was yellow transparent fluid. Storage Conditions The corrosion detection tests were performed on aluminium, stainless steel and mild steel for two months and two weeks, under close and open cap static immersion conditions 13. Freeze-thaw cycles were implemented on the HEDA emulsions as a storage condition. Freeze-thaw cycles are used to measure the stability of emulsions. The various storage conditions (Refrigerator, cycling chamber, elevated temperature, light exposure, ambient temperature, and freeze-thaw cycles) can be used as test conditions for emulsion stability testing 20. For each cycle, the emulsions were kept in a refrigerator at -20°C for 24 hours and then at room temperature for next 24 hours 19-20. Two such cycles were employed for the emulsions, as done by Khar et al. 19. The HEDA emulsions were kept at 50°C for 30 days to perform the heat storage test 21. Analytical Techniques The density, specific gravity and API gravity were measured by a digital density meter using ASTM standard D4052 at 20°C. The digital density meter works on the oscillating U-tube technique in which oscillation frequency is measured electronically to calculate the density, specific gravity and API gravity values. Kinematic viscosity was measured using the 11 ACS Paragon Plus Environment

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Cannon-Fenske routine viscometer, using ASTM standard D445-12 at 40°C. The HEDA emulsions were inspected for change in colour, phase separation and sediment formation during the freeze-thaw condition. The emulsion stability was investigated in the centrifuge, at 25°C and 5000 rpm for 30 minutes, using ASTM standard D1796 14, 19. Different coloured sediments were observed after the centrifugation. The sediment percentage was calculated for each emulsion. The pH value was measured by the digital pen-type pH meter at room temperature. The pH meter was calibrated before each measurement as per the instruction manual to achieve higher accuracy. The technical details of instruments are displayed in Table 4. The measurements were taken twice and their average values are displayed in Table 5-7. The heat storage test was conducted at 50°C for 30 days. The samples were kept in the laboratory oven. Kinematic viscosity was measured before and after the heat storage test, as displayed in Table 8. Aluminium, stainless steel and mild steel metals were selected for the corrosion detection method. The metal pieces were cleaned and smoothened properly. The pieces underwent static immersion into the HEDA emulsions for two months and two weeks under the close and open cap conditions, as suggested by Low and his research group 13. The metal pieces were weighed precisely before static immersion. After static immersion, the metal pieces were dried out, properly cleaned and weighed again. The weight loss measurements are shown in Table 9 and 10. RESULTS AND DISCUSSION In the present study, several analytical techniques have been used to measure the stability aspect of HEDA emulsified fuel and the results obtained from these techniques have been studied in detail in this section of the manuscript. Here, the results of the stability tests and their causes are


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discussed in depth. The results are affected by the chemical hydrogen bonding between the different compounds of the HEDA emulsified fuel. Further, these results have been elaborated in the following sub-sections: Density, specific gravity and API gravity The density measurement of a new fuel has an important role in investigation of combustion behavior of fuel. The higher density of a fuel may produce larger sized fuel droplets that may create a difficulty in fuel atomization, resulting in poor combustion. The density measurement at different pressures and temperatures can predict the reaction of HEDA emulsified fuel with air when injected into an internal combustion engine. The density and the specific gravity of HEDA emulsions increased slightly, compared to mineral diesel, while the reverse trend was noted for the API gravity, in accordance with the results reported by Chandra et al 17. It was due to the presence of water, surfactant and Al2O3 nano particles 3, 7, 10. From the standpoint of chemistry, the increase in density occurred due to incorporation of oxygen via aluminium oxide nano particles, H2O molecules, ethyl alcohol and other oxygenated compounds. The change in density can likely be related to an increase in hydrogen bonding between oxygenated compounds of HEDA emulsions. The combination of hydrophilic (Ethanol), hydrophobic (Diesel and Al2O3 nano particles) and amphiphilic (Span 80 and Tween 80) compounds were found responsible for the density increase via hydrogen bonding 27. The API gravity indicates the density measurement of petroleum liquids, established by the American Petroleum Institute. Specific gravity and API gravity are related to the density of petroleum liquids. The highest density, specific gravity and API gravity variations were found 13 ACS Paragon Plus Environment

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between W20H15D85 and W20H20D80 as 0.0039 g/cm3, 0.0039 and 0.81 respectively. W20H20D80 exhibited a drastic decrease in the density values (Fig. 4) which indicated a poor emulsion formation. It could be due to the highest amount of hydrous ethanol in the HEDA emulsion. The lowest density, specific gravity and API gravity changes were found between W15H10D90 and W15H15D85 as 0.0001 g/cm3, 0.0001 and zero. Fig. 4 depicts the density variation for all the categories. Specific gravity and API gravity followed the similar pattern with regards to density so only the density variation is shown in Fig. 4. It was observed that the density increased with an increase in hydrous ethanol. Comparing the density variation trends of all the categories, it can be concluded that the low-density variation showed better emulsion stability. Kinematic viscosity The kinematic viscosity of the HEDA emulsions increased with an increase in water and ethanol percentages simultaneously 3, 10, 15. This increase in viscosity occurred due to the high viscosity of water and surfactant. Al2O3 nano particles contributed to an increase in the viscosity of the HEDA emulsions 4, 7. Actually, high molecular weight of surfactants Span 80 and Tween 80 boosted the viscosity of the HEDA emulsions. The significant fraction of heavier components (aromatics) and heteroatom containing species in diesel, Span 80 and Tween 80 resulted in a substantial increase in emulsion viscosity 26. The increased viscosity was closely related to crosslinks formation between surfactants and other oxygenated or non-oxygenated compounds. The viscosity rise was observed for HEDA emulsions possibly due to hydrogen bonding among compounds that enhanced the interactive forces between molecules 27.


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Kinematic viscosity should be maintained to the nearest limit of diesel (1.7-4.1 cst@40°C) to follow the fuel injection regulation 6, 12. All the HEDA emulsions followed this viscosity limit, except W20H5D95, as shown in Fig. 5. The reason could be that W20H5D95 was a part of the highest water containing emulsion category. W20H20D80 emulsion showed a drastic decrease in kinematic viscosity, as shown in the rectangular box (Fig. 5), which could be due to sediment deposition. It could be the limit of hydrous ethanol in the HEDA emulsion. The viscosity pattern was noticed to be almost similar to the density variation pattern. During freeze-thaw condition, the highest and the lowest viscosity variations were observed for W20H5D95 and W5H10D90 emulsions, respectively. The high amount of water in HEDA emulsions was responsible for the higher viscosity variation. Further, the effect of different temperatures can be studied on viscosity and density variations of HEDA emulsions as the emulsified fuel preparation, transportation and storage may be accomplished at different temperatures. pH value The measured pH values of HEDA emulsions varied in the range of 5.08 to 7.21. It showed the acidic nature of emulsions. The pH of an emulsion indicates the hydrogen ion concentration in that emulsion. High hydrogen ion activity in an emulsion shows low pH value, which means that the emulsion is acidic. The freeze-thaw condition did not have a significant effect on the pH value. A stable emulsion shows a constant pH value during the storage condition 22. Observing the pH variation pattern of HEDA emulsions (Fig. 6), it was clear that low pH variations during the freeze-thaw cycles represented a stable emulsion in accordance with the results reported by Yani et al. 22. W15H20D80 showed the least pH variation, as exhibited in Fig. 6. The pH of W20H20D80 emulsion was drastically lowered, which indicated that the emulsion was less stable. 15 ACS Paragon Plus Environment

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Visual inspection All HEDA emulsions were transparent yellow coloured fluids with no separation layer and sediment during the freeze-thaw condition, except W20H20D80 emulsion, as shown in Fig. 7. It could be due to the dominating quantity of diesel in HEDA emulsions as diesel is a yellow coloured fuel. The W20H20D80 emulsion was observed as green coloured non-transparent fluid with white sediment, accumulated at the bottom. The white sediment may represent poor mixing of Al2O3 nano particles. The change in colour may indicate the limit of water and ethanol content in the HEDA emulsion. The surfactant quantity may not be sufficient to form a stable W20H20D80 emulsion. There could be a possibility of stabilizing W20H20D80 emulsion by increasing the surfactant percentage 13. It was the highest water containing emulsion so it could be possible that all the water molecules did not share hydrogen bonding with the hydrophilic (water loving) portion of surfactants Span 80 and Tween 80. The transparent HEDA emulsions with no separation layer and sediment represented stable emulsions 12-13, 17. Further, the HEDA emulsions can be examined for droplet size measurement using the microscopic techniques. The sediment formation in W20H20D80 emulsion may be avoided by increasing the surfactant concentration and/or emulsification time. An in-depth visual analysis can be performed using an adequate imaging instrument. Centrifuge study The centrifuge sediment percentages of the HEDA emulsions were calculated in the similar way as done by Patil et al.2. Increase in ethanol and water concentrations in HEDA emulsions raised the sediment level while the higher sediment percentage showed lower emulsion stability 2. The higher disperse phase in the emulsion increased sediment level. The sediment level was varied


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from 1.29 to 7.14% during the freeze-thaw condition. There was no phase separation layer during the centrifugation, which confirmed the stability of HEDA emulsions in accordance with the results obtained by Do et al. 14 and stated by Khar et al. 19. The higher level of sediments indicated heterogeneous mixing of HEDA emulsion components. The heavier compounds (having higher molecular weights), like Span 80 and Tween 80, were collected at the bottom (closed end) of the centrifuge tube by the action of centrifugal force. The HEDA emulsion constituents got separated during centrifugation because of density and size differences among them. The emulsion constituent with larger size and higher density moves faster, towards the bottom of the tube, while smaller and lesser dense particles remain in the emulsion as continuous phase 28. The centrifugation of HEDA emulsions produced different colour sediments, as shown in Fig. 8. The white sediment possibly showed some amount of agglomerated Al2O3 nano particles. The brown sediment most likely represented unmixed surfactant. The black sediment could be the result of carbon deposits from diesel and ethanol. The highest amount of sediments was observed for the highest water containing emulsion category, except W20H20D80. Further, the emulsions can be analyzed at different centrifuge speeds. Zeta potential measurement may also give better explanations for sediment formation. Heat storage test The viscosity rise varied between 19.08% and 79.50%. The rise in emulsion viscosity lower than 20% indicates one year stability at room temperature, when stored at 50°C for one month. So, the lowest rise in kinematic viscosity showed the highest stability period 21. W20H5D95 emulsion expressed the least viscosity rise but its initial viscosity was too high to make this emulsion worthy. On the other hand, W20H20D80 emulsion showed the highest viscosity rise which indicated lower stability duration 21. The change in colour was observed from yellow to red after 17 ACS Paragon Plus Environment

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the heat storage test, as shown in Fig. 9. It could be due to the heat absorbed by the HEDA emulsions. For general liquids, the viscosity decreases with an increase in the temperature but the presence of a non-ionic surfactant in the HEDA emulsions increased the viscosity with temperature due to unusual rheological behavior. This behavior was caused by the growth of contour length of wormlike micelles (head and tail part of Span 80 and Tween 80) of the HEDA emulsions 23. The increase in contour length of micelles was likely pointing to strong hydrogen bonding between hydrophobic-hydrophobic and hydrophilic-hydrophilic groups, present in the substances of HEDA emulsions. The small angle neutron scattering can be used for detailed study. Corrosion detection The loss in the weight of the metal was detected due to an undesirable oxidation reaction between the metal and the HEDA emulsions. This agreed with Low et al 13. The corrosion was responsible for the metal weight loss. This corrosion could be due to the presence of water, contaminant and/or ionic impurities. This type of corrosion comes under crevice corrosion as it occurs in a confined space with limited oxygen content. The weight loss of ≤ 0.0002 gram could be neglected and considered to be an indicator to the non-corrosive nature of emulsion 13. The weight loss for most of the metals was found below 0.0002 gram. The short immersion period of two months and two weeks was not sufficient to judge any significant weight loss. The open cap condition offered more oxygen-rich surface to the immersed metals than the close cap condition, as shown in Eq. (1). It was noticed by the change in emulsion colour, as shown in Fig. 10. 𝑀𝑒𝑡𝑎𝑙 + 𝐻𝐸𝐷𝐴 + 𝑂2 → 𝑀𝑒𝑡𝑎𝑙 𝑂𝑥𝑖𝑑𝑒

(1)


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Energy & Fuels

O2 in Eq. (1) is the additional oxygen from the atmosphere. In the close cap static immersion condition, the metals were oxidized using oxygen from the HEDA emulsion, while the additional oxygen from atmosphere oxidized the metals in the open cap condition. Aluminium is a highly reactive metal so it reacts with oxygen and water present in HEDA emulsion, atmospheric air, and sample container air, at a very fast rate to form Al2O3 and Al(OH)3, as shown in the Eqs. (2) - (6). The partial oxidation of Al metal produced Al(OH)3, which was further converted into Al2O3 on complete oxidation. 𝐴𝑙 → 𝐴𝑙 3+ + 𝑒 −

(2)

𝑂2 + 𝑒 − → 𝑂2−

(3)

𝐴𝑙 3+ + 𝑂2− → 𝐴𝑙2 𝑂3

(4)

𝐴𝑙 + 𝑂2 + 𝐻2 𝑂 → 𝐴𝑙(𝑂𝐻)3

(5)

𝐴𝑙 + 𝐻2 𝑂 → 𝐴𝑙(𝑂𝐻)3

(6)

Aluminium metal can have a limited corrosion on its surface because the outer Al2O3 surface behaves like a protective layer from further corrosion. It was justified by the corrosion detection results via metal loss technique, as shown in Fig. 11 and Fig. 12. Mild steel has iron (Fe) as its main component while carbon is only 0.1-0.3%. Iron in mild steel has a great tendency to be corroded and rusted, which results in weight loss of mild steel, according to the following Eqs. (7) - (11). The partial oxidation of Fe metal produced Fe(OH)2 which was further converted into Fe2O3 on complete oxidation. Fe2O3.H2O was visualized as red rust on the metal surface.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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𝐹𝑒 → 𝐹𝑒 2+ + 𝑒 −

(7)

𝑂2 + 𝑒 − + 𝐻2 𝑂 → 𝑂𝐻 −

(8)

𝐹𝑒 2+ + 𝑂𝐻 − → 𝐹𝑒(𝑂𝐻)2

(9)

𝐹𝑒(𝑂𝐻)2 + 𝑂2 → 𝐹𝑒2 𝑂3 + 𝐻2 𝑂

(10)

𝐹𝑒 + 𝑂2 + 𝐻2 𝑂 → 𝐹𝑒2 𝑂3 . 𝐻2 𝑂

(11)

The weight loss of mild steel was recognizable with W15H20D90 and W20H20D80 under both the conditions as depicted in Fig. 11 and Fig. 12. The highest weight loss (0.00054 gram) was detected on aluminium immersion in W15H15D85, under the open cap condition, as displayed in Fig. 12. Stainless steel did not show significant metal loss under close and open cap conditions. It could be due to the presence of significant amount of chromium in stainless steel which minimizes the tendency of corrosion. A similar phenomenon of formation of protective oxide layer also occurs in stainless steel like in aluminium metal. Significant metal corrosion was detected for the higher water containing emulsion categories (W15 and W20) because high amount of metal oxide was formed due to the availability of high oxygen content in water. From the observed results of corrosion detection technique, it was clear that the significant weight loss of metals was detected for the higher water containing emulsion categories (W15 & W20) while these emulsion categories were considered to be least stable according to the stability test results. Thus, there looked to be a direct relation between them. The least stable HEDA emulsions showed the maximum corrosive effect on metals. It could be due to poor hydrogen bonding between the compounds of HEDA emulsions that might result in the higher concentration of free oxygen radicals and ions which could oxidize the metals severely.


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Energy & Fuels

The corrosion detection was not studied by the stages within the defined time frame so it was impossible to track which emulsion corroded the metal first. The various species of metals will be recommended for future work. Later on, this work can be precised by the surface examination of metals with Scanning Electron Microscope or X-Ray Spectroscopy. Effect of HEDA emulsion on environment and health The effect of HEDA emulsion on earth’s environment, via tailpipe emissions, can be predicted on the basis of previous studies 29-33. Although, the ethanol content in ethanol-diesel blend decreased carbon monoxides (CO) and unburnt hydrocarbons (UHC) with an increase in NOx 33, the presence of hydrous ethanol in HEDA emulsion is likely to decrease NOx and soot content along with an increase in UHC and CO 29-30. The above statement clearly indicates that the effect of water content seems to dominate over ethanol, in concern of emissions from hydrous ethanol-diesel emulsified fuel. The soot oxidation reactivity could be increased due to thermal cracking of a large number of hydrocarbons and aromatic compounds, available in HEDA emulsion 42. An increase in soot oxidation reactivity can possibly lower the soot content in exhaust emissions. At high combustion temperature, hydrocarbons and aromatic compounds in HEDA emulsions could be decomposed and form very small porous carbon layers on the surface of soot. This phenomenon can possibly increase the active surface area (ASA) of soot. The higher ASA would thus result in higher soot oxidation reactivity. Increased soot oxidation reactivity would oxidize a larger amount of soot that could result in lower emissions of soot from the tailpipe. But, a lower combustion temperature produces more disordered nanostructure of soot particles. However, a significant change in soot nano structure is not expected due to a very low quantity of water in proposed HEDA fuel, as observed by Ruiz et al. 32.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

An availability of oxygenated compounds, water and ethanol in the HEDA fuel can reduce a significant level of soot emissions, owing to lower carbon-to-hydrogen ratio and absence of aromatic species in their chemical structure which are the main precursors for tendency to form soot 40. However, surfactants could behave like a combination of surface functional groups (SFGs) to treat the soot surface thermally at high temperatures and help to oxidize the soot particles at a faster rate 41. The presence of SFGs, aliphatic C-H, C-OH and C=O on the surface of soot particles, shows a significant effect on soot oxidation reactivity during combustion phases of a fuel. However, aliphatic C-H groups have higher impact than the oxygenated SFGs 41. Wang et al. 41 reported higher C-H groups at the early stage of pre-mixed combustion phase of diesel fuel but later on, at high temperature and pressure, the concentration of C-H group decreased due to enhanced dehydrogenation and carbonization reactions that resulted in sharp increase in apparent activation energy of soot surface. The same pattern was followed during diffusion phase of diesel combustion. The HEDA emulsified fuel has a larger number of aliphatic C-H and oxygenated SFGs in their compounds than diesel, which may possibly enhance the active sites on the surface of soot. A large number of active sites are expected to promote higher oxidation of soot and therefore reduce its emission. The catalytic behaviour of Al2O3 nano particles (present in HEDA fuel), is expected to stabilize SFGs on the soot surface at high temperatures due to dehydrogenation reactions to improve the soot oxidation reactivity. Collura and his research group 42 reported the decomposition of SFGs, soluble organic fraction (SOF) and volatile organic fraction (VOF) of diesel fuel by their interactions with soot at higher temperatures. The SOF can be divided into volatile and non-volatile categories. Light hydrocarbons come under the volatile section while heavy


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Page 23 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

hydrocarbons and aromatics are a part of the non-volatile section because of their high molecular weights. Span 80 and Tween 80 (non-volatile SOF) in HEDA fuel can add the effect of a change in the surface chemistry of soot along with the oxygenated SFGs (volatile SOF) at high combustion temperature, compared to neat diesel. NOx formation depends on three major factors: combustion temperature, fuel-air mixture stoichiometry, and the rate of combustion reaction. The water content in HEDA emulsion lowers the combustion temperature on account of its high latent heat of vaporization characteristic 30. The lowering of combustion temperature can reduce the high emission level of NOx in the exhaust. But at the same time, the oxidization of HC and CO slows down, owing to insufficient combustion temperature. It leads to incomplete oxidation of HC and CO into H2O and CO2, resulting in higher HC and CO emissions. The lower level of exhausted NOx minimizes the tendency of ground level (Tropospheric zone) ozone growth that may contribute to global warming and health hazardous in humans like respiratory problems, asthma, lungs malfunction, irritation to eye, nose, and throat as well as damage to plants 34. The emission of NOx in the environment causes smog formation that affects normal breathing in human beings. Smog formation is the next stage of tropospheric ozone formation in which the ground level ozone combines with NOx to form smog. The presence of ethanol in the HEDA emulsion is responsible for acetaldehyde and formaldehyde emissions from tailpipe 35. The photo-oxidation of acetaldehyde and formaldehyde can contribute to an enhancement in ground level ozone and NOx. The addition of Al2O3 nanoparticles into biodiesel reported a decrease in HC, CO and Smoke opacity with an increase in NOx 36-37. It might follow the same pattern for HEDA emulsions. To predict the effect of Al2O3 nano particles on emission aspects of HEDA emulsified fuel, the


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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combustion phenomenon of Al2O3 nano particles is discussed. Al2O3 nano particles are converted into Al2O and atomic oxygen at high combustion temperatures. Al2O cannot remain in stable condition during combustion at high temperatures, so it dissociates into aluminium and oxygen 37, as shown in Eqs. (12) and (13). 𝐴𝑙2 𝑂3 → 𝐴𝑙2 𝑂 + 2𝑂

(12)

𝐴𝑙2 𝑂 → 2𝐴𝑙 + 𝑂

(13)

The additional oxygen generated from combustion of Al2O3 nano particles (Eqs. 12 and 13) is likely to oxidize CO and HC completely, which reduces the emission of these pollutants into the environment. But at the same time, it can make the fuel-air mixture leaner, which results in higher NOx concentration. The reduction in soot can be expected in the presence of oxygen-rich combustion environment 37. Aluminium released during combustion (Eq. 13) may affect the functioning of the enzyme system (used in the intake of nutrients) in terrestrial and aquatic animals, when exhausted into atmosphere form the diesel engine tailpipe. This environmental aluminium may combine with atmospheric water vapour or rain water and reach roots of a plant, causing lack in the growth of the plant. Since the plants are a part of the terrestrial food chain, the entire food chain may be disturbed 38. The implementation of Al2O3 nano particles into a fuel imposes toxicity on human lungs and inhibits regular growth of plants like corn, soybean, carrot, and cabbage 34. Al2O3 nano particles act as oxygen-donor catalyst during a chemical reaction between fuel and air. They release atomic oxygen during combustion, which is highly reactive. This additional oxygen attracts more fuel to be burnt, thus a larger quantity of fuel reacts with the overall oxygen in the same time


Page 25 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

compared to non-Al2O3 nano fuel. The acceleration in fuel-oxygen reaction rate results in higher heat release rate during combustion, higher peak pressures and temperatures inside the combustion chamber. As we all know that high temperature is the main cause for higher NOx formation, so higher combustion temperatures will result in higher NOx emissions. This, in turn, is responsible for an increase in acidification and eutrophication process which has toxic effect on human organs and affects the regular growth of plants as well. Past studies have reported its significant toxic effect to human beings and environment, but still, further research is required to prove it hazard 34, 36-37. CONCLUSIONS In the present study, Al2O3 nano particles have been added in the hydrous ethanol-diesel emulsion and the stability concerns are discussed. The various stability tests have been performed on the HEDA emulsions and positive results are obtained. The corrosion detection checks were executed on three different common metals to study the corrosion effect using the different HEDA emulsions. The effects of HEDA emulsified fuel, especially the additional compound Al2O3 nano particles, have been anticipated on the environment and living beings. From this study, the following conclusions can be revealed: (1) The stability of the HEDA emulsions decreased with an increase in water and ethanol content. (2) The highest water containing emulsion category (W20) was observed to be the least stable, out of which, W20H20D80 could be the most unstable. (3) W5H10D90 was observed to be the most stable HEDA emulsion. (4) The static immersion open cap condition offered higher corrosive effect.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(5) Mild steel is not recommended to manufacture fuel system components when HEDA emulsified fuel is injected into a diesel engine. (6) The combustion of HEDA emulsified fuel can exhibit a toxic effect on living beings and the environment in prolonged period of time. ACKNOWLEDGEMENTS The authors acknowledge TEQIP-II Cell, Dr. B. R. Ambedkar National Institute of Technology Jalandhar, Punjab, India for financial support (Ref. No. NITJ/TEQIP-II/R&D/2017/6067-76). REFERENCES (1) Basha, J.S.; Anand, R.B. An experimental study in a CI engine using nano additive blended water-diesel emulsion fuel. Int. J. Green Energy 2011, 8, 332-348. (2) Patil, H.; Gadhave, A.; Mane, S.; Waghmare, J. Analyzing the stability of the water-in-diesel fuel emulsion. J. Dispersion Sci. Technol. 2015, 36, 1221-1227. (3) El-Din, M.R.N.; El-Hamouly, S.H.; Mohamed, H.M.; Mishrif, M.R.; Ragab, A.M. Water-in-diesel fuel nanoemulsion: Preparation, stability and physical properties. Egypt. J. Pet. 2013, 22, 517-530. (4) Sajeevan, A.C.; Sajith, V. Diesel engine emission reduction using catalytic nano particles: An experimental investigation. J. Eng. 2013, 1-9. (5) Ghannam, M.T.; Selim, M.Y.E. Stability behavior of water-in-diesel fuel emulsion. Pet. Sci. Technol. 2009, 27 (4), 396-411.


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Energy & Fuels

(6) Taib, N.M.; Mansor, M.R.A.; Mahmood, W.M.F.W.; Shah, F.A.; Abdullah, N.R.N. Investigation of diesel-ethanol blended fuel properties with palm methyl ester as co-solvent and blends enhancer. MATEC Web Conf. 2017, 90 (01080), 1-11. (7) Abdalla, S.; Al-Wafi, R.; Pizzi, A. Stability and combustion of metal nano-particles and their additive impact with diesel and biodiesel on engine efficiency: A comprehensive study. J. Renewable Sustainable Energy 2017, 9 (022701), 1-47. (8) Lapuerta, M.; Garcia-Contreras, R.; Campos-Fernandez, J.; Dorado, M.P. Stability, lubricity, viscosity, and cold-flow properties of alcohol-diesel blends. Energy Fuels 2010, 24, 4497-4502. (9) Lapuerta, M.; Armas, O.; Garcia-Contreras, R. Effect of ethanol on blending stability and diesel engine emissions. Energy Fuels 2009, 23, 4343-4354. (10) Vellaiyan, S.; Amirthagadeswaran, K.S. The role of water-in-diesel emulsion and its additives on diesel engine performance and emission levels: A retrospective review. Alexandria Eng. J. 2016, 55, 2463-2472. (11) Lapuerta, M.; Armas, O.; Garcia-Contreras, R. Stability of diesel-bioethanol blends for use in diesel engines. Fuel 2007, 86, 1351-1357. (12) Lee, K.H.; Mukhtar, M.; Hagos, F.Y.; Noor, M.M. A study of the stabilities, microstructures and fuel characteristics of tri-fuel (diesel-biodiesel-ethanol) using various fuel preparation methods. IOP Conf. Ser.: Mater. Sci. Eng. 2017, 257 (012077), 1-15. (13) Low, M.H.; Mukhtar, M.; Hagos, F.Y.; Noor, M.M. Tri-fuel (diesel-biodiesel-ethanol) emulsion characterization, stability and the corrosion effect. IOP Conf. Ser.: Mater. Sci. Eng. 2017, 257 (012080), 1-11. 27 ACS Paragon Plus Environment

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(14) Do, L.D.; Singh, V.; Chen, L.; Kibbey, T.C.G.; Gollahalli, S.R.; Sabatini, D.A. Algae, canola, or palm oils-diesel microemulsion fuels: Phase behaviors, viscosity and combustion properties. Int. J. Green Energy 2011, 8 (7), 748-767. (15) Mehta, R.N.; Chakraborty, M.; Parikh, P.A. Comparative study of stability and properties of alcohol-diesel blends. Indian J. Chem. Technol. 2012, 19, 134-139. (16) Mehta, R.N.; Chakraborty, M.; Parikh, P.A. Study of stability, physical properties and engine performance of alcohol blended fuels. Indian J. Chem. Technol. 2014, 21, 182-187. (17) Chandra, R.; Kumar, R. Fuel properties of some stable alcohol-diesel microemulsions for their use in compression ignition engines. Energy Fuels 2007, 21, 3410-3414. (18) Venkatesan, H.; Sivamani, S.; Sampath, S.; Gopi, V.; Kumar M, D. A comprehensive review on the effect of nano metallic additives on fuel properties, engine performance and emission characteristics. Int. J. Renew. Energy Res. 2017, 7 (2), 825-843. (19) Khar, R.K.; Pathan, S.A.; Jain, G.K.; Ahmad, S.A.F.J. Microemulsion: Practical applications and concepts. Pharmstudent 2010, 25 (5), 26-32. (20) Particle Sciences, Drug Development Services, USA. Emulsion stability and testing. Technical Brief 2011, 2, 1-2. (21) Lubrizol, Technical Data Sheet (TDS-114). Introducing pemulen polymeric emulsifiers 2017, 1-7. (22) Yani, S.; Aladin, A.; Wiyani, L.; Modding, B. Evaluation of viscosity and pH on emulsions of virgin coconut oil beverages. IOP Conf. Ser.: Earth Environ. Sci. 2018, 175 (012026), 1-6.


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(23) Kalur, G.C.; Frounfelker, B.D.; Cipriano, B.H.; Norman, A.I.; Raghavan, S.R. Viscosity increase with temperature in cationic surfactant solutions due to the growth of wormlike micelles. Langmuir 2005, 21, 10998-11004. (24) Croda Europe Ltd., England. Span and Tween. Home Care 2010, D1005 (1), 1-6. (25) Kopanichuk, I.V.; Vedenchuk, E.A.; Koneva, A.S.; Vanin, A.A. Structural properties of Span 80/Tween 80 reverse micelles by molecular dynamics simulations. J. Phys. Chem. B 2018, 122 (33), 8047-8055. (26) Zolfaghari, R.; Abdullah, L.C.; Biak, D.R.A.; Radiman, S. Cationic surfactants for demulsification of produced water from alkaline-surfactant-polymer flooding. Energy Fuels 2018, 33 (1), 115-126. (27) Ball, J.; Anderson, J.E.; Pivesso, B.P.; Wallington, T.J. Oxidation and polymerization of soybean biodiesel/petroleum diesel blends. Energy Fuels 2017, 32 (1), 441-449. (28) Baek, S.; Min, J.; Ahn, Y.; Cha, M.; Lee, J.W. Effect of hydrophobic silica nanoparticles on the kinetics of methane hydrate formation in water-in-oil emulsions. Energy Fuels 2018, 33 (1), 523-530. (29) Bach, F.; Loft, M.; Bartosch, S.; Spicher, U. Influence of diesel-ethanol-water blended fuels on emissions in diesel engines. MTZ 2011, 72, 62-68. (30) Chang, Y.C.; Lee, W.J.; Lin, S.L.; Wang, L.C. Green energy: Water-containing acetone-butanol-ethanol diesel blends fueled in diesel engines. Appl. Energy 2013, 109, 182-191.


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(31) Lopez, A.F.; Cadrazco, M.; Agudelo, A.F.; Corredor, L.A.; Velez, J.A.; Agudelo, J.R. Impact of n-butanol and hydrous ethanol fumigation on the performance and pollutant emissions of an automotive diesel engine. Fuel 2015, 153, 483-491. (32) Ruiz, F.A.; Cadrazco, M.; Lopez, A.F.; Sanchez-Valdepenas, J.; Agudelo, J.R. Impact of dual-fuel combustion with n-butanol or hydrous ethanol on the oxidation reactivity and nanostructure of diesel particulate matter. Fuel 2015, 161, 18-25. (33) Yahuza, I.; Dandakouta, H. A performance review of ethanol-diesel blended fuel samples in compression-ignition engine. J. Chem. Eng. Process Technol. 2015, 6 (5), 1-6. (34) Ojeda, K.A.; Herrera, A.P.; Sierra, M.J.; Tamayo, K. Environmental impact study by life cycle assessment of the use of alumina nanoparticles as an additive in biodiesel/diesel blends. Ing. Compet. 2015, 17 (1), 133 – 142.

(35) Liu, J.; Sun, P.; Zhang, B. Effects of diesel/ethanol dual fuel on emission characteristics in a heavy-duty diesel engine. IOP Conf. Ser.: Mater. Sci. Eng. 2017, 231 (012190), 1-6. (36) Aalam, C.S.; Saravanan, C.G. Effects of nano metal oxide blended mahua biodiesel on CRDI diesel engine. Ain Shams Eng. J. 2015, 1-8. (37) Gurusala, N.K.; Selvan, V.A.M. Effects of alumina nanoparticles in waste chicken fat biodiesel on the operating characteristics of a compression ignition engine. Clean Technol. Environ. Policy 2015, 17, 681-692. (38) Rosseland, B.O.; Eldhuset, T.D.; Staurnes, M. Environmental effects of aluminium. Environ. Geochem. Health 1990, 12, 17-27.


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(39) Lamoureux, S.F.; Bollmann, J. Image acquisition. In Image Analysis, Sediments and Paleoenvironments; Francus, P., Ed.; Springer: Dordrecht, 2005; Vol. 7, Chapter 2, pp 11-34. (40) Surawski, N.C.; Ristovski, Z.D.; Brown, R.J.; Situ, R. Gaseous and particle emissions from an ethanol fumigated compression ignition engine. Energy Convers. Manage. 2012, 54, 145-151. (41) Wang, L.; Song, C.; Song, J.; Lv, G.; Pang, H.; Zhang, W. Aliphatic C-H and oxygenated surface functional groups of diesel in-cylinder soot: Characterizations and impact on soot oxidation behavior. Proc. Combust. Inst. 2013, 34, 3099-3106. (42) Collura, S.; Chaoui, N.; Azambre, B.; Finqueneisel, G.; Heintz, O.; Krzton, A.; Koch, A.; Weber, J.V. Influence of the soluble organic fraction on the thermal behavior, texture and surface chemistry of diesel exhaust soot. Carbon 2005, 43, 605-613.


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TABLES Table 1 - Specifications of Span 80, Tween 80 and Ethanol Materials → Specifications ↓ Manufacturer CAS No. Chemical Formula Mol. Wt.(g/mole) Density (kg/m3@20oC) Appearance

Span 80

Tween 80

Ethanol

Oxford Laboratory 1338-43-8 C24H44O6 428.61 991.85 Brown Liquid

Oxford Laboratory 9005-65-6 C32H60O10 604.822 1080.26 Amber Liquid

Merck 64-17-5 C2H5OH 46.07 795.05 No Color (Transparent)

Table 2 - Properties of Al2O3 nano particles Properties Manufacturer CAS No. Chemical Formula Appearance Ph Value Purity, % Crystal Structure Average Particle Size, nm Surface Area, m2/g

Values Nano Partech 1344-28-1 Al2O3 White Powder 6.6 99.99 Gamma 30-50 15-20

Table 3 - HEDA emulsified fuel matrix (Al2O3 nano particles - 100 ppm in each emulsion) Emulsion Designation W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80

Water in Hydrous Ethanol (%) 5 5 5 5 10 10 10 10

Hydrous Ethanol (%)

Diesel (HSD) (%)

5 10 15 20 5 10 15 20

95 90 85 80 95 90 85 80


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Energy & Fuels

15 15 15 15 20 20 20 20

W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

5 10 15 20 5 10 15 20

95 90 85 80 95 90 85 80

Table 4 – Technical details of measuring instruments Instrument

Make and Model

Ultrasonicator

Labman, LMUC-2 JLab Instruments, JC-PLE2263 (1/12 hp Motor)

Mechanical stirrer

Measuring Range

Uncertainty

40 KHz

± 3 KHz

0 – 7000 rpm

± 50 rpm

Density meter

Antonpaar, DMA 4200 M

0 - 3 g/cc

± 0.01%, Level of confidence – 95%

Cannon-fenske routine viscometer (Size – 75)

Daihan Scientific Co. Ltd., WVB-30

1.6 - 8 cSt

± 0.2%

Centrifuge

Eppendorf, 5810R

(-9) - 40°C, 1 99 min, 200 14000 rpm

pH meter

Medicare Product Inc., pH 02

0.00 – 14.00 pH

± 3°C, ± 1 min, ± 10 rpm up to 5000 rpm afterwards ± 100 rpm ± 0.01 pH

Table 5- Properties measured after HEDA emulsified fuels preparation Properties → Emulsion Designation ↓

API Gravity @15oC

Density @20oC (g/cc)

Specific Gravity @20oC

API Gravity @29.5oC

Kinematic Viscosity@ 40oC (cst)

pH Value

Blend Color

Sediment Content (%)

Diesel (HSD) W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80 W15H5D95

39.92 39.06 38.44 38.36 38.25 37.92 37.72 37.81 37.82 37.98

0.8211 0.8252 0.8282 0.8286 0.8292 0.8313 0.8318 0.8314 0.8313 0.8308

0.8225 0.8267 0.8297 0.8301 0.8307 0.8329 0.8333 0.8329 0.8328 0.8322

42.13 41.24 40.59 40.51 40.40 40.06 39.84 39.94 39.95 40.11

2.91 2.86 3.14 3.45 3.57 3.67 3.77 3.52 3.68 3.62

9.03 6.06 6.50 5.79 6.24 7.04 7.21 6.94 6.75 6.82

Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow

0 1.29 2.59 2.65 4.68 4.13 3.99 4.28 2.84 3.15


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

37.89 37.96 37.72 37.98 37.76 37.71 38.49

0.8310 0.8307 0.8318 0.8305 0.8319 0.8320 0.8285

0.8325 0.8322 0.8333 0.8320 0.8333 0.8336 0.8300

Page 34 of 44

40.02 40.09 39.85 40.11 39.89 39.83 40.64

3.53 3.78 3.74 4.14 3.82 3.75 3.22

6.80 6.79 6.77 6.52 6.46 6.02 5.09

Yellow Yellow Yellow Yellow Yellow Yellow Green

3.09 6.19 6.75 6.74 5.81 6.03 5.55

Table 6 - Properties measured after 1st freeze-thaw cycle Properties → Emulsion Designation ↓

API Gravity @15oC



API Gravity @29.5oC


pH Value

Blend Color


Diesel (HSD) W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80 W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

39.33 39.06 38.43 38.32 38.24 37.95 37.77 37.83 37.76 37.91 37.83 37.83 37.56 37.75 37.69 37.54 38.33

0.8240 0.8252 0.8283 0.8289 0.8292 0.8312 0.8316 0.8313 0.8316 0.8309 0.8313 0.8312 0.8326 0.8316 0.8320 0.8327 0.8288

0.8255 0.8267 0.8298 0.8304 0.8307 0.8327 0.8331 0.8328 0.8331 0.8324 0.8328 0.8327 0.8341 0.8331 0.8335 0.8342 0.8303

41.52 41.24 40.59 40.46 40.38 40.09 39.90 39.96 39.88 40.04 39.96 39.96 39.68 39.88 39.81 39.66 40.48

3.28 3.28 3.06 3.54 3.60 3.42 3.57 3.65 3.57 3.57 3.58 3.86 3.77 3.61 3.84 3.83 3.16

9.07 5.88 6.22 6.10 6.05 6.85 6.85 6.87 7.12 6.85 6.75 6.55 6.77 6.84 6.26 6.04 5.12

Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Green

4.67 2.10 3.84 3.23 5.22 2.28 2.24 2.44 5.67 6.01 5.79 4.58 4.71 4.94 6.62 6.71 6.37

Table 7 - Properties measured after 2nd freeze-thaw cycle Properties → Emulsion Designation ↓

API Gravity @15oC



API Gravity @29.5oC


pH Value

Blend Color


Diesel (HSD) W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95

39.27 39.05 38.44 38.19 37.89 37.96

0.8242 0.8252 0.8283 0.8295 0.8310 0.8307

0.8257 0.8267 0.8298 0.8310 0.8325 0.8321

41.46 41.23 40.59 40.34 40.02 40.10

2.82 3.06 3.18 3.27 3.69 3.65

9.02 5.08 5.93 6.00 6.08 6.79

Yellow Yellow Yellow Yellow Yellow Yellow

5.77 1.74 3.58 3.51 4.71 5.26


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Energy & Fuels

W10H10D90 W10H15D85 W10H20D80 W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

37.95 37.95 37.88 37.84 37.87 37.85 37.56 37.59 37.68 37.71 38.40

0.8312 0.8311 0.8314 0.8312 0.8315 0.8314 0.8326 0.8328 0.8322 0.8323 0.8284

0.8327 0.8326 0.8329 0.8327 0.8330 0.8329 0.8341 0.8343 0.8337 0.8338 0.8299

40.09 40.08 40.01 39.97 40.00 39.98 39.68 39.71 39.80 39.84 40.56

3.68 3.67 3.81 3.87 3.80 3.48 3.54 3.94 3.67 3.94 3.37

6.99 6.84 6.67 6.71 6.66 6.90 6.79 6.76 6.23 5.80 5.21

Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Yellow Green

5.74 5.53 2.90 3.57 4.00 6.36 6.14 6.46 7.14 6.10 5.62

Table 8 –Change in viscosity during heat storage test Viscosity → Emulsion Designation ↓ Diesel (HSD) W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80 W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

Kinematic viscosity before heat storage test (cst) 2.91 2.86 3.14 3.45 3.57 3.67 3.77 3.52 3.68 3.62 3.53 3.78 3.74 4.14 3.82 3.75 3.22

Kinematic viscosity after heat storage test (cst) 3.64 5.08 5.19 5.78 5.69 5.42 5.38 5.68 5.74 5.43 5.66 5.39 5.65 4.93 5.41 4.90 5.78

Rise in kinematic viscosity (%) 25.08 77.62 65.29 67.54 59.38 47.68 42.70 61.36 55.98 50.00 60.34 42.59 51.07 19.08 41.62 30.67 79.50

Table 9 - Static immersion weight loss under close cap condition Emulsion Designation W5H5D95 W5H10D90

Weight loss (g) Stainless steel 0 0.00013

Aluminium 0 0 35

ACS Paragon Plus Environment

Mild steel 0.00010 0.00013

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80 W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

0.00004 0.00013 0.00006 0.00016 0.00014 0.00007 0 0.00012 0 0.00004 0.00009 0.00009 0.00001 0.00027

Page 36 of 44

0 0.00004 0 0 0.00023 0 0 0.00002 0.00002 0.00010 0.00004 0.00002 0.00009 0.00004

0.00003 0.00001 0.00001 0 0.00001 0.00005 0 0.00013 0.00006 0.00042 0.00002 0 0.00019 0.00039

Table 10 - Static immersion weight loss under open cap condition Emulsion Designation W5H5D95 W5H10D90 W5H15D85 W5H20D80 W10H5D95 W10H10D90 W10H15D85 W10H20D80 W15H5D95 W15H10D90 W15H15D85 W15H20D80 W20H5D95 W20H10D90 W20H15D85 W20H20D80

Weight loss (g) Stainless steel 0 0.00006 0 0 0.00003 0.00004 0.00002 0 0 0.00001 0.00001 0.00001 0.00005 0.00004 0.00004 0.00005

Aluminium 0 0 0.00002 0.00006 0.00001 0.00004 0.00009 0.00002 0.00002 0.00003 0.00054 0.00002 0.00021 0 0.00004 0.00004


Mild steel 0 0.00001 0.00002 0.00007 0 0.00001 0.00007 0.00005 0.00003 0 0.00009 0.00027 0.00007 0.00004 0.00003 0.00026

Page 37 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

FIGURES

Figure 1. HEDA emulsified fuel preparation stages


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2. HEDA emulsified fuel formulation mechanism (Stage I & II)


Page 38 of 44

Page 39 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 3. HEDA emulsified fuel formulation mechanism (Stage III, IV & V)


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4. Density variation for HEDA emulsions

Figure 5. Viscosity variation for HEDA emulsions 40 ACS Paragon Plus Environment

Page 40 of 44

Page 41 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 6. pH variation for HEDA emulsions before and after freeze-thaw cycles

Figure 7. Visualization of W20H20D80 and other HEDA emulsions


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 8. Centrifuge sediments

Figure 9. HEDA emulsion before and after heat storage test


Page 42 of 44

Page 43 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 10. HEDA emulsion before and after static immersion

Figure 11. Weight loss detection under close cap static immersion 43 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 12. Weight loss detection under open cap static immersion


Page 44 of 44

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