Improving the low-temperature properties of alternative diesel fuels: Vegetable oil-derived methyl esters

This work explores near-term approaches for improving the low-temperature properties of triglyceride oil-derived fuels for direct-injection compression-ignition (diesel) engines. Methyl esters from transesterified soybean oil were evaluated as a neat fuel and in blends with petroleum middle distillates. Winterization showed that the cloud point (CP) of methyl soyate may be reduced to −16°C. Twelve cold-flow additives marketed for distillates were tested by standard petroleum methodologies, including CP, pour point (PP), kinematic viscosity, cold filter plugging point (CFPP), and low-temperature flow test (LTFT). Results showed that additive treatment significantly improves the PP of distillate/methyl ester blends; however, additives do not greatly affect CP or viscosity. Both CFPP and LTFT were nearly linear functions of CP, a result that compares well with earlier studies with untreated distillate/methyl ester blends. In particular, additives proved capable of reducing LTFT of neart methyl esters by 5–6°C. This work supports earlier research on the low-temperature properties; that is, approaches for improving the cold flow of methyl ester-based diesel fuels should continue to focus on reducing CP.     

Study on performance mechanism of pour point depressants with differential scanning calorimeter and X-ray diffraction methods

Adding pour point depressants (PPD) to lower the Cold Filter Plugging Point (CFPP) of diesel fuels is an effective and economic way of improving the cold flow properties of the oils. EVAP is a new type of PPD and has an excellent effect in lowering the CFPP of most Chinese diesel fuels. To further the development of this PPD product, its performance mechanism was studied using four kinds of diesel fuels, each with a different response. Differential scanning calorimeter and X-ray diffraction methods were selected as the research measures. According to the experimental results, the growth rate paralleling to (001) plane was cumbered and the integrity of the crystal was greatly improved. The results analysis shows that the EVAP molecules have taken effect by co-crystallization. The crystallinity of the diesel fuels is an important factor in determining the responsibility of the oils.     

AMSV-a柴油低温流动改进剂的研制

介绍了柴油低温流动改进剂AMSV-a的合成和降凝助滤性能。该剂是以丙烯酸酯、马来酸酐、苯乙烯、醋酸乙烯酯(量比为4∶1∶0 5∶1)为原料,以甲苯为溶剂,以过氧化苯甲酰(用量5 0g/mol共聚单体)为引发剂,恒温80℃聚合6h,得四元共聚物(AMSV),再以对甲苯磺酸为催化剂(用量20g/mol共聚单体),用高碳胺〔n(酐)∶n(胺)=1∶1 5〕进行胺解制得。该剂对大庆-10#柴油的纯降凝度可达25℃,冷滤点降低可达16℃;对胜利0#柴油的纯降凝度可达23℃,冷滤点降低可达14℃;对东明5#柴油的纯降凝度可达20℃,冷滤点降低可达11℃;对濮阳10#柴油的纯降凝度可达17℃,冷滤点降低可达9℃。     

Temperature effect on the viscosities of palm oil and coconut oil blended with diesel oil

One of the major difficulties in using crude vegetable oils as substitute fuels in diesel engines is their relatively high viscosities. Increasing the temperature of the crude vegetable oil, blending it with diesel oil, or the combination of both offers a simple and effective means of controlling and lowering the viscosities of vegetable oils. This work reports viscosity data, determined with a rotational bob-and-cup viscometer, for crude palm oil and cononut oil blended with diesel oil over the temperature range of 20–80°C and for different mixture compositions. All the test oil samples showed a time-independent newtonian type of flow behavior. The reduction of viscosity with increasing liquid temperature followed an exponential relationship, with the two constants of the equation being a function of the volume percentage of the vegetable oil in the mixture. A single empirical equation was developed for predicting the viscosity of these fuel mixtures under varying temperatures and blend compositions.     

EsMOVS柴油降凝剂的研制

对柴油降凝剂ＥｓＭＯＶＳ的合成、用途、使用条件、影响因素等作了阐述。此降凝剂对抚顺石油二厂－１０＃柴油的纯降凝度是１８℃，冷滤点纯降低度是９℃。对其它柴油也有一定的降凝助滤效果。     

Studying the efficiency of the diesel fuel isodewaxing process on a zeolite-containing nickel–molybdenum catalyst

A GIP-14 diesel fuel isodewaxing catalyst based on a mixture of zeolites with different pore structures and entrance sizes and transition metals Ni and Mo as hydrogenating components is developed. Its stability during operation is studied. It is shown that the cold filter plugging point (CFPP) of the diesel fuel reaches values below–38°C at its yield of 92–93 wt %, temperatures of 305–310°C, and a feedstock hourly space velocity (FHSV) of 3 h^?1. A pilot diesel fuel sample is tested according to GOST (Russian State Standard) R 55475–2013. Comparative tests of domestic and foreign catalysts show that the developed GIP-14 catalyst conforms to international standards and allows the production of diesel fuel with required cold flow properties under milder conditions (300°C against 320–325°C for the foreign catalyst) at a higher FHSV (3 h^?1 against 2 h^?1). The production of GIP-14 catalyst is planned to be launched in 2017.     

Properties of rapeseed oil for use as a diesel fuel extender

Chemical and thermal analyses were carried out on degummed and filtered (5 μm) rapeseed oil (referred to as SRO, i.e., semirefined rapeseed oil) to determine its suitability as a diesel fuel extender. The upper rate for inclusion of SRO with diesel fuel is 25%. This fuel blend had a phosphorus level of 2.5 ppm, which was comparable to rape methyl esters (1.0 ppm phosphorus). Thermogravimetric analyses were used to estimate the cetane ratings of the fuels. A 25% SRO/diesel blend had an estimated cetane index of 32.4 compared to 38.1 for diesel fuel only. Differential scanning calorimetry and thermogravimetric analyses were used to compare the volatility ranges of the fuels. SRO needed higher temperatures for volatilization (i.e., 70–260°C for diesel fuel vs. 280–520°C for SRO). This indicated poorer cold-starting performance of SRO compared with diesel fuel. SRO fuel is a low-sulfur, high-oxygen fuel giving SRO a more favorable emissions profile than pure diesel fuel.     

Upgrading coal-derived liquids to diesel fuel

Distilled fractions of a coal-derived liquid from the H-Coal process were upgraded to diesel fuel by catalytic hydrotreatment. The total hydrotreated products were distilled into naphtha (<180°C) and diesel fuel fractions (>180°C) and the diesel fractions were analysed for hydrocarbon-type composition, hydrogen content and some diesel fuel properties. GC—MS-analyses were carried out on the hydrocarbon-type fractions to identify individual chemical compounds. To investigate the effect of different distillation cut points on diesel fuel yield and properties, cut points for one hydrotreated product were varied. The diesel fuel cetane numbers were correlated with percentage hydrogen, total aromatics and saturates. Cetane numbers above 40 were obtained for diesel fuels containing (i) more than 75% saturates, (ii) less than 15% total aromatics and (iii) a hydrogen content above 12.8%. Compounds identified by GC—MS-analyses (in the diesel fractions) were typical aromatic and cycloparaffin compounds. Normal-and iso-paraffin compounds were not detected. By varying the distillation cut point from 135 to 180°C, the cetane number of the residual diesel fraction improved from 37 to 44. This increase is ascribed to the removal of aromatic compounds in the 135–180°C boiling point range.     

Cold flow properties of fuel mixtures containing biodiesel derived from animal fatty waste

The aims of the present study were to evaluate the cold temperature behavior of methyl esters of vegetable and animal origin and of their mixtures with fossil diesel fuel, as well as to investigate the effectiveness of different depressants. Various blends of rapeseed oil methyl esters, linseed oil methyl esters, pork lard methyl esters and fossil diesel fuel were prepared, and both cloud point and cold filter plugging point (CFPP) were analyzed. It was found that mixtures with CFPP values of –5 °C and lower may contain up to 25% of pork lard methyl esters; whereas the ratio of summer fossil diesel fuel and rapeseed oil methyl esters may vary over a wide range, i.e. such mixtures can be used in a diesel engine in the summer. In the transitory periods it is possible to use up to 20% animal and vegetable ester blends (3 : 7) with winter fossil diesel, whereas only up to 5% of esters can be added to the fuel used in winter. In order to improve the cold properties of rapeseed oil, pork lard and linseed oil methyl ester mixtures, various additives were tested. Depressant Viscoplex 10–35 with an optimal dose of 5000 mg/kg was found to be the most effective.     

Formulation of Canola-Diesel Microemulsion Fuels and Their Selective Diesel Engine Performance

Vegetable oils have been considered as an alternative to diesel fuel due to their comparable properties and performance. However, the high viscosity of vegetable oil causes engine durability problems with long-term usage. Vegetable oil viscosity can be reduced by blending with diesel fuel in thermodynamically stable mixtures using microemulsion fuel formulation techniques. This work focuses on the formulation of microemulsion fuels comprising diesel fuel and canola oil as the oil phase with ethanol and sec-butanol as viscosity reducers as well as 1-octanol and oleyl amine as surfactant/cosurfactant. Selective tests on an instrumented diesel engine were performed for formulated microemulsion fuels and No. 2 diesel fuel for comparison. The results show that formulated microemulsion fuels have fuel properties that meet the ASTM requirements for viscosity, cloud point, and pour point for biodiesel. Even more important, they have phase stability over a wide range of temperatures (−10 to 70 °C). Although all of the microemulsion fuels showed higher fuel consumption than diesel fuel, some of the microemulsion fuels had significantly reduced CO and NO_x emissions as well as reduced particulates when compared to baseline diesel fuel. The research demonstrates the potential of these microemulsion fuels as alternative to neat diesel fuel.     

选择性溶剂萃取生产低凝柴油的溶剂筛选和溶剂选择性的表征

酮类、酯类、氯代烃类溶剂分别对减一线油和常三线油进行了选择性萃取生产低凝柴油的实验。溶剂乙酸乙酯的选择性好,可降低减一线油和常三线油冷滤点分别为18°C和16°C,同时对柴油燃烧性能的影响较小,是选择性萃取生产低凝柴油的最佳溶剂。比较了各溶剂的脱蜡率、脱出的各碳数正构烷烃的质量分布和脱蜡油的冷滤点,引入了由高碳数正构烷烃脱出量、脱蜡率和冷滤点降低值三个因子组成的综合评价参数。该参数能表征本工艺要求的选择性,并直观地指导对两种油样均优的萃取溶剂的选择。     

Optimised Mixture Formation for Diesel Fuel Processing

Mixture formation plays an important role in the diesel reforming process. It is important to maintain proper O₂/C and H₂O/C ratios to avoid hot spots and coking. Fuel must be completely evaporated before entering the reaction zone in order to prevent catalyst damage by coking. Computational fluid dynamics (CFD) is used to optimise the mixing process. Turbulent mixing, diesel spray injections and evaporation and simplified chemical reactions have been calculated. This revealed critical parts of the existing construction. However, experimental verification is necessary. To identify thermodynamic conditions for a possible carbon formation process, experiments with idealised model fuels as well as with real diesel fuel were carried out. Flow visualisation experiments serve for the verification of the CFD simulations. Quartz glass reactors as models of the reformers were operated under real mixing temperatures (400 °C) to observe the effect of the flow profile on fuel sprays. Experiments with coloured fuels were used to visualise the flow and concentration profiles in the mixing chamber. Results were compared with CFD models. Two patented reformers were designed as a result of the CFD optimisation. These were operated for 500 h and 1,000 h respectively with a commercially available diesel, showing very promising results.     

A PM 2.5 Inlet Impactor Designed for a High Flow Application

Two potential strategies for reducing diesel emissions are exhaust aftertreatment and the use of reformulated or alternative fuels. Little is yet known about the impact on ultrafine particle emissions of combining exhaust aftertreatment with such increasingly common fuels. This paper reports ultrafine particle size distribution measurements for a study in which the impact of such fuels on emissions from a heavy duty diesel engine employing different aftertreatment configurations was evaluated. Eight different fuels were tested: Canadian No. 1 and No. 2 diesel; low sulfur diesel fuel; two different ultra low sulfur diesel fuels (< 30 ppm S); Fischer-Tropsch diesel fuel; 20% biodiesel blended with ultra low sulfur diesel fuel; and PuriNO_x?. The fuels were tested in combination with four exhaust configurations: engine out, diesel oxidation catalyst (DOC), continuously regenerating diesel particle filter (CRDPF), and engine gas recirculation with CRDPF (EGR-DPF). In general, aftertreatment configuration was found to have a greater impact on ultrafine particle size distributions than fuel composition, and the effects of aftertreatment tended to be uniform across the entire particle size distribution. Steady state tests revealed complex behavior based on fuel type, particularly for PuriNOx. This behavior included bimodal particle size distributions with modes as low as 8–10 nm for some fuels. Unlike previous results for gravimetric PM from this study, no significant correlation for ultrafine emissions was found for fuel properties such as sulfur level.     

Assessment on the use of biodiesel in cold weather: Pour point determination using a piezoelectric quartz crystal

In order to use biodiesel safely, as an alternative fuel for diesel engines, without fear of cold weather, the pour point of the blends needs to be estimated. This paper is aimed to propose an alternative and easy to use methodology, based on a piezoelectric quartz crystal, to determine the pour point of biodiesels and blended fuels.Impedance and phase of impedance vs. frequency of the piezoelectric quartz crystal change significantly during cooling of biodiesel and biodiesel blended fuels and allows to confirm the role of ethanol as a cold flow improver for biodiesel. Pour point is readily determined by finding the minimum series or parallel frequencies of a barred piezoelectric quartz crystal in contact with the biodiesel blended fuel along cooling. This new methodology only needs the measurement of series frequency, which can be accomplished with high precision by connecting a frequencymeter to a home made oscillator that drives the piezoelectric quartz crystal. Although inexpensive, this new methodology is no more based on visual inspection as the ASTM D97 method, and allows data to be acquired more frequently than the 3 °C intervals recommended by the time consuming standard methodology. In the new proposed methodology, data is acquired while the fuel is at the controlled temperature, which is not possible with the ASTM method, where the test jar needs to be removed from the thermostatic bath for visual inspection.Pour points of biodiesel blends with a commercial diesel fuel determined by this new methodology were compared with the ones obtained by the official ASTM methodology. For samples with pour points ranging from 2.3 °C (pure biodiesel) to −15.0 °C (pure commercial fuel diesel), median pour point values obtained for replicate measurements performed by the two methodologies were not statistically different (α = 0.05), although the results obtained by the new methodology were more precise.     

Solubility limitations of residual steryl glucosides,saturated monoglycerides and glycerol in commercial biodiesel fuels as determinants of filter blockages

Newer, improved high pressure common rail diesel engines require increased protection from damaging particles in fuel, resulting in tighter, low-micron filtration requirements. The unobstructed flow of fuel through filters underlies the well-known efficiencies and reduced exhaust emissions of diesel engines, and when flows are hindered, these efficiencies become severely compromised. Biodiesel fuels frequently contain saturated monoglycerides, glycerol (GLY) and/or steryl glucosides, systemic impurities that become problematic when low concentrations exceed ill-defined solubility limits, usually unexpectedly at low temperatures. Here, filters and blended fuels from seven flow obstruction incidents were subjected to detailed compositional analyses. With one exception the fuels contain estimated levels within international specifications, yet exhibit heterophase (HP) formation in the laboratory at 2°C, well above measured cloud points. Feedstock composition, pretreatment and/or purification processes are found to modulate insolubility risks. Interferences in standard gas chromatography methods used without modification can hide or complicate estimates of residual levels of GLY. The data show that classical variables controlling solubility, such as concentrations and temperatures, play important roles in setting the risks associated with in situ formation of HPs from these common impurities. Further, such risks are likely attenuated considerably by reductions in critical impurities beyond currently specified limits.     

Storage stability of marine diesel fuels

The cause of instability in marine diesel fuels was investigated by ageing several fuels at 65 °C for various periods. Aged and unaged fuel samples were chromatographically separated into acid, base and neutral fractions, and the fractions were analysed in detail to obtain a clearer understanding of the mechanism of colour change and sediment formation. The results suggest that oxidation of neutral compounds to polar intermediates may be a major pathway for sediment formation and darkening of marine diesel fuels. Considerable loss of polar compounds, both those originally present and those newly formed, to sediment was also found. Within a compound class, the more aromatic higher molecular weight members were observed to be the most active in sediment formation.     

Influence of ethanol blends on the combustion performance and exhaust emission characteristics of a four-cylinder diesel engine at various engine loads and injection timings

The aim of this work is to investigate the effect of ethanol blending to diesel fuel on the combustion and exhaust emission characteristics of a four-cylinder diesel engine with a common-rail injection system. The overall spray characteristics, such as the spray tip penetration and the spray cone angle, were studied with respect to the ethanol blending ratio. A spray visualization system and a four-cylinder diesel engine equipped with a combustion and emission analyzer were utilized so as to analyze the spray and exhaust emission characteristics of the ethanol blending diesel fuel. Ethanol blended diesel fuel has a shorter spray tip penetration when compared to pure diesel fuel. In addition, the spray cone angle of ethanol blended fuels is larger. It is believed that the lower fuel density of ethanol blended fuels affects the spray characteristics. When the ethanol blended fuels are injected around top dead center (TDC), they exhibit unstable ignition characteristics because the higher ethanol blending ratio causes a long ignition delay. An advance in the injection timing also induces an increase in the combustion pressure due to the sufficient premixed duration. In a four-cylinder diesel engine, an increase in the ethanol blending ratio leads to a decrease in NO_x emissions due to the high heat of evaporation of ethanol fuel, however, CO and HC emissions increase. In addition, the CO and HC emissions exhibit a decreasing trend according to an increase in the engine load and an advance in the injection timing.     

Temperature-dependent kinematic viscosity of selected biodiesel fuels and blends with diesel fuel

The kinematic viscosities of four biodiesel fuels—two natural soybean oil methyl esters, one genetically modified soybean oil methyl ester, and one yellow grease methyl ester—and their 75, 50, and 25% blends with No. 2 diesel fuel were measured in the temperature range from 20 to 100°C in steps of 20°C. The measurements indicated that all these fuels had viscosity-temperature relationships similar to No. 2 diesel fuel, which followed the Vogel equation as expected. A weighted semilog blending equation was developed in which the mass-based kinematic viscosity of the individual components was used to compute the mixture viscosity. A weight factor of 1.08 was applied to biodiesel fuel to account for its effect on the mixture viscosity. The average absolute deviation achieved with this method was 2.1%, which was better than the uncorrected mass average blending equation that had an average absolute deviation of 4.5%. The relationship between the viscosity and the specific gravity of biodiesel fuels was studied. A method that could estimate the viscosity from the specific gravity of biodiesel fuel was developed. The average absolute deviation for all the samples using this method was 2.7%. The accuracy of this method was comparable to the weighted mass-based semilog blending equation.     

The kinematic viscosity of biodiesel and its blends with diesel fuel

As the use of biodiesel becomes more wide-spread, engine manufacturers have expressed concern about biodiesel’s higher viscosity. In particular, they are concerned that biodiesel may exhibit different viscosity-temperature characteristics that could result in higher fuel injection pressures at low engine operating temperatures. This study presents data for the kinematic viscosity of biodiesel and its blends with No. 1 and No. 2 diesel fuels at 75, 50, and 20% biodiesel, from close to their melting point to 100°C. The results indicate that while their viscosity is higher, biodiesel and its blends demonstrate temperature-dependent behavior similar to that of No. 1 and No. 2 diesel fuels. Equations of the same general form are shown to correlate viscosity data for both biodiesel and diesel fuel, and for their blends. A blending equation is presented that allows the kinematic viscosity to be calculated as a function of the biodiesel fraction.     

Study of oxygenated biomass fuel blends on a diesel engine

Vegetable methyl ester was added in ethanol–diesel fuel to prevent separation of ethanol from diesel in this study. The ethanol blend proportion can be increased to 30% in volume by adding the vegetable methyl ester. Engine performance and emissions characteristics of the fuel blends were investigated on a diesel engine and compared with those of diesel fuel. Experimental results show that the torque of the engine is decreased by 6%–7% for every 10% (by volume) ethanol added to the diesel fuel without modification on the engine. Brake specific fuel consumption (BSFC) increases with the addition of oxygen from ethanol but equivalent brake specific fuel consumption (EBSFC) of oxygenated fuels is at the same level of that of diesel. Smoke and particulate matter (PM) emissions decrease significantly with the increase of oxygen content in the fuel. However, PM reduction is less significant than smoke reduction. In addition, PM components are affected by the oxygenated fuel. When blended fuels are used, nitrogen oxides (NO_x) emissions are almost the same as or slightly higher than the NO_x emissions when diesel fuel is used. Hydrocarbon (HC) is apparently decreased when the engine was fueled with ethanol–ester–diesel blends. Fuelling the engine with oxygenated diesel fuels showed increased carbon monoxide (CO) emissions at low and medium loads, but reduced CO emissions at high and full loads, when compared to pure diesel fuel.