Cetane Number Of Diesel Fuels Research Articles

A Simulation of the Effect of Iraqi Diesel Fuel Cetane Number on the Performance of a Compression Ignition Engine

Cetane Number (CN) or cetane rating is an indication of the compression energy required for ignition and a diesel fuel’s combustion speed. It is similar to an octane rating in gasoline but in inverse terms. CN is a pivotal factor in verifying diesel fuel quality. In this work, the diesel engine performance has been analyzed through simulations and the findings have been compared with experimental results. The study has been conducted to evaluate the effect of diesel fuels with different cetane numbers (CN 51.4 to CN 54.6) used in Iraq. The experimental work has been performed on an innovative research engine: a multi-cylinder CI engine with four strokes, an indirect injection fuel system, and a constant compression ratio. The theoretical part of the study has dealt with the modelling of the same engine using simulation and analysis engineering software, specifically the Lotus Engine Simulation (v.6.01a). The same operating conditions have been created at different loads. It has been found out that increasing the cetane number has resulted in an improvement in all the engine performance elements. Simulation results have revealed a good agreement with the experimental findings, with errors not exceeding 3%.

Development of a Mathematical Model for Calculating the Cetane Number of Diesel Fuel Based on Their Hydrocarbon Composition and Intermolecular Interactions of Mixture Components

ABSTRACT The authors studied hydrocarbon compositions of diesel fuel with a cetane improver and its relationship with the cetane number. The paper presents the results of these studies. The influence of synergistic and antagonistic effects in determining the cetane number of diesel fuels resulting from the interaction of various hydrocarbons (paraffins, naphthenes, aromatics) with the cetane improver is shown. These effects can be attributed to forces of intermolecular interaction of hydrocarbons with the additive, which influence the thermodynamic probability and the rate of formation of various hydrocarbon radicals during the combustion of the diesel fuel in engine conditions (t = 2000°C, p = 50 atm.). Energies of interaction of hydrocarbons with the cetane improver were estimated on the basis of quantum chemical calculations. Using the results of quantum chemical modeling, the authors developed a mathematical model to predict an increase in the cetane number of diesel fuels depending on the concentration of the additive for different fuel compositions, while taking into account intermolecular interactions of mixture components.

Linear transformations of multivariate calibration models in near infrared spectroscopy: A comparative study

It was shown that linear transformations are suitable for use in multivariate calibration in near infrared spectroscopy as data compression tools. Partial Least Squares calibration models were built using spectral data transformed by expansion in the series of classical orthogonal polynomials, Fourier and wavelet harmonics. These models allowed effective prediction of the cetane number of diesel fuels, Brix and pol parameters of syrup in sugar production and fat and total protein content in milk. Depending on the compression ratio, prediction errors were no larger than 30% of corresponding errors obtained by the use of the non-transformed models. Although selection of the most suitable transformation depends on the calibration data and on the cross-validation method, in many cases Fourier transform gave satisfactory results.

Physicochemical properties of Euro standard diesel fuel

It is known that the quality of diesel fuel is characterized by both performance indicators and environmental properties of fuel. At the same time, the introduction of modern norms and standards that are associated with the modification of the component composition of fuel sets the task of controlling the physicochemical properties of diesel fuels. To solve the task, fuel samples, purchased from different fuel producers, and diesel fuel samples with an unknown prehistory, stored for a long time in the laboratory, were investigated. Mixtures of fuel with kerosene were also investigated. Diluted kerosene fuel, when it is used, reduces not only the power, but also the engine life. The density of the objects of the study was measured with oil meters. The viscosity and fractional composition of the fuels were determined using the VPZh-4 viscosimeter and the ARNS-1E oil distillation apparatus, respectively. Cetane numbers were measured by the OCTAN-IM indicator. As a result of the carried out researches it is established that the density, viscosity, fractional composition of diesel fuels correspond to those presented in the GOST standards. The acidity of samples with a long storage time and an unknown prehistory is greater than the GOST indicator value. The average value of the cetane number of diesel fuels measured by the OCTAN-IM indicator and different from the parameters required by the regulations is identical to the value given in the world fuel charter standard (ISO 5156). In all, without exception, fuels are present unsaturated and aromatic hydrocarbons. It is shown that in the fuel produced by different manufacturers, the ratio of unsaturated and aromatic hydrocarbons can be different. The density, viscosity and other characteristics of the mixture containing 10% kerosene are identical to the normalized values for diesel fuel. The density of the mixture containing 30% kerosene is not only below the norm, but also below the measured values of the density of diesel fuels.

Selective Formation of Linear Alkanes from n-Hexadecane Primary Hydrocracking in Shape-Selective MFI Zeolites by Competitive Adsorption of Water

MFI type zeolites have been known for decades for their strong tendency toward gas formation in hydrocracking. Our strategy for selectivity control in hydrocracking turns strong adsorption in micropores, responsible for secondary cracking, to an advantage. Enhancing diesel yield is a challenging goal in hydrocracking catalysis. Additionally, linear alkanes increase the diesel fuel cetane number and, consequently, effect a dramatic reduction in exhaust emissions. This study demonstrates for a set of Pt on mesoporous MFI zeolite catalysts that the gains in activity and selectivity attributed to enhanced mass transport are but modest by comparison to the effects of the competitive adsorption of water. Water suppresses secondary cracking, and primary cracking is now reported over MFI zeolites. Furthermore, competitive adsorption of water in shape-selective MFI zeolites facilitates desorption of the primary n-C16 cracking products and suppresses subsequent isomerization resulting in high yields of linear alkan...

Decalin ring opening over NiWS/SiO2-Al2O3 catalysts in the presence of H2S

Selective ring opening (SRO) is an attractive route for increasing the cetane number of diesel fuels. Noble metal-based catalysts have been proposed for this purpose. However, considering the type of processes producing diesel, more sulfur-resistant catalysts would be preferred for SRO. In the present study, we investigated the performance of bifunctional NiW sulfide catalysts supported onto amorphous silica-alumina in gas-phase decalin hydroconversion at high hydrogen pressure (5MPa) in the presence of 0.8% H2S concentration at 350–380°C. Two-dimensional gas chromatography (GC×GC) was extensively employed to identify the reaction products and determine their distributions in the form of chemical families. The impact of acidity due to two different SiO2 contents (40 and 70wt.%) in the support, as well as promoting the catalytic systems by P or F doping, were studied on the one hand. On the other hand, the improvement of the hydrogenation function by the use of chelating agents was investigated. Up to 17% in selectivity to ring-opening products was obtained. The reaction mechanism is shown to be mostly governed by the acidic function, which promotes the formation of skeletal-isomerization products, while the sulfide phase allows hydrogen activation.

Effect of metal–acid site balance on hydroconversion of decalin over Pt/Beta zeolite bifunctional catalysts

The main objective of this work is contributing to the understanding of the ring opening of naphthenic model molecules, an important reaction to improve the cetane number of diesel fuels. Accordingly, the hydroconversion of decalin was studied over a series of Pt/Beta catalysts with different metal contents in order to evaluate the effect of changing the proportion of hydrogenation/acid functions of the catalyst on conversion and products distribution. The overall reaction rate did not change by increasing the hydrogenation activity (metal content) of the catalyst. However, ring contraction and ring opening product yields increased with metal content up to 1.0wt% and then became constant for higher metal contents, while cracking product yields followed an opposite trend, decreasing with increasing metal content up to 1.0wt%. This behavior clearly provides evidence of a bifunctional mechanism in the hydroconversion of decalin over Pt/BEA catalysts, since the selectivity depends on the metal/acid function balance. Although decalin is a saturated molecule, its naphthenic character and probably the presence of a tertiary carbon in its structure facilitate activation of the molecule directly on the strong acid sites of zeolite, even at relatively moderate temperatures. Thus, it is not necessary to form an olefin on a metal site, which would undergo subsequent protonation, as in a classical bifunctional mechanism, such as in hydroisomerization and hydrocracking of n-paraffins. However, the hydrogenation component of the catalyst influences the selectivity of the reaction, controlling the process of desorption/adsorption of any intermediate olefins formed. Greater hydrogenation activity implies lower availability of adsorbed carbocations that can be converted to cracking products. This proposition is consistent with the results obtained by varying the content of metal and poisoning of the hydrogenation sites in the catalysts.

The influence of propylene glycol ethers on base diesel properties and emissions from a diesel engine

The oxygenated additives propylene glycol methyl ether (PGME), propylene glycol ethyl ether (PGEE), dipropylene glycol methyl ether (DPGME) were studied to determine their influence on both the base diesel fuel properties and the exhaust emissions from a diesel engine (CO, NOx, unburnt hydrocarbons and smoke). For diesel blends with low oxygen content (⩽4.0wt.%), the addition of these compounds to base diesel fuel decreases aromatic content, kinematic viscosity, cold filter plugging point and Conradson carbon residue. Also, each compound modifies the distillation curve at temperatures below the corresponding oxygenated compound boiling point, the distillate percentage being increased. The blend cetane number depends on the type of propylene glycol ether added, its molecular weight, and the oxygen content of the fuel. The addition of PGME decreased slightly diesel fuel cetane number, while PGEE and DPGME increased it.Base diesel fuel-propylene glycol ether blends with 1.0 and 2.5wt.% oxygen contents were used in order to determine the performance of the diesel engine and its emissions at both full and medium loads and different engine speeds (1000, 2500 and 4000rpm). In general, at full load and in comparison with base diesel fuel, the blends show a slight reduction of oxygen-free specific fuel consumption. CO emissions are reduced appreciably for 2.5wt.% of oxygen blends, mainly for PGEE and DPGME. NOx emissions are reduced slightly, but not the smoke. Unburnt hydrocarbon emissions decrease at 1000 and 2500rpm, but not at 4000rpm. At medium load, the effect of the additives is much less significant, due to the fact that the ratio oxygen from additive/oxygen from air is much lower.

Effects of ethylene glycol ethers on diesel fuel properties and emissions in a diesel engine

The effect of ethylene glycol ethers on both the diesel fuel characteristics and the exhaust emissions (CO, NO x , smoke and hydrocarbons) from a diesel engine was studied. The ethers used were monoethylene glycol ethyl ether (EGEE), monoethylene glycol butyl ether (EGBE), diethylene glycol ethyl ether (DEGEE). The above effect was studied in two forms: first by determining the modification of base diesel fuel properties by using blends with oxygen concentration around 4 wt.%, and second by determining the emission reductions for blends with low oxygen content (1 wt.%) and with 2.5 wt.% of oxygen content. The addition of DEGEE enhances base diesel fuel cetane number, but EGEE and EGBE decrease it. For concentrations of ⩾4 wt.% of oxygen, EGEE and diesel fuel can show immiscibility problems at low temperatures (⩽0 °C). Also, every oxygenated compound, according to its boiling point, modifies the distillation curve at low temperatures and the distillate percentage increases. These compounds have a positive effect on diesel fuel lubricity, and slightly decrease its viscosity. Blends with 1 and 2.5 wt.% oxygen concentrations were used in order to determine their influence on emissions at both full and medium loads and different engine speeds. Generally, all compounds help to reduce CO, and hydrocarbon emissions, but not smoke. The best results were obtained for blends with 2.5 wt.% of oxygen. At this concentration, the additive efficiency in decreasing order was EGEE > DEGEE > EGBE for CO emissions and DGEE > EGEE > EGBE for hydrocarbon emissions. For NO x , both its behaviour and the sequence are opposite to that of CO.

A mathematical model for calculating the increase in the cetane number of diesel fuels in the presence of an ignition initiator

A mathematical model was developed for calculating the increase in the cetane number of diesel fuels in the presence of the ignition initiator 2-ethylhexyl nitrate (EHN) as a function of the initial cetane number of the fuel and the concentration of EHN. The accuracy of the results of the calculations with the model is as good as the accuracy obtained on a bench unit. A mechanism of the reaction of EHN with the hydrocarbons in diesel fuel is proposed based on calculations with the PM6 semiempirical quantum-chemical method.

Predicting the Effect of Cetane Improvers on Diesel Fuels

A composition-based model is presented that predicts the effect of cetane improver (specifically 2-ethyl hexyl nitrate) on the cetane number of diesel fuels. A total of 206 different diesel fuels were considered in this work containing varying amounts of improver. The fuels were chosen to span a wide range of compositions, from highly paraffinic to highly naphthenic and, in some cases, highly aromatic fuels. Improver concentrations were varied between 0 to 3500 ppm (v/v), which exceeds the usual commercial application range of 500–1000 ppm. Detailed molecular composition of all the fuels was analyzed using a combination of GC-MS and supercritical fluid chromatographic techniques, while cetane number measurements were made using an Ignition Quality Tester (IQT). Molecular composition was correlated to the cetane number (CN) boost using a simple correlative equation, derived from phenomenological considerations. The model predicts CN boost with a standard error of ±0.8 CN, which is within the experimental error of the measurements.

Detailed Composition-Based Model for Predicting the Cetane Number of Diesel Fuels

We have developed a simple composition-based model for predicting the cetane number of diesel fuels with general applicability to any diesel fuel regardless of the refining process it originates from. The cetane number is correlated to a total of 129 different hydrocarbon lumps determined by a combination of supercritical fluid chromatography, gas chromatography, and mass spectroscopic methods. A total of 203 diesel fuels are considered in this study derived from various diesel-range refinery process streams and their commercial blends. Across the multitude of such process streams and blends, the model predicts the cetane number with a standard error of 1.25 numbers, which is well within the experimental error of the measurement.

Organic Peroxides — Cetane–Increasing Additives for Diesel Fuels

Organic peroxides are examined as additives that increase the cetane number of diesel fuels. In contrast to traditional alkyl nitrates, they are less toxic, do not worsen the anticorrosion properties of fuels, and are very compatible with other additives. In addition, peroxides contain no nitrogen and are considered promising additives in regions where the nitrogen content in fuels is restricted. Peroxide additives have not yet been widely distributed due to their comparatively high cost.

A Neural Network Approach to the Prediction of Cetane Number of Diesel Fuels Using Nuclear Magnetic Resonance (NMR) Spectroscopy

In this work, quantitative relationships between the structural parameters of diesel fuels, as observed by 1H NMR spectroscopy, have been established, with their ignition delay characteristics, using the artificial neural network (ANN) technique. Sixty commercial diesel samples were analyzed for this study. The cetane number (CN) of the samples was determined on an ignition quality tester (IQT). The 1H NMR spectra of the samples were used as their structural characteristics, and relative intensities of various regions in the spectra were used as neural network inputs. The spectra in each case were divided into 18 regions, representing paraffins (normal and iso), cycloalkanes, olefins, and aromatics (different types). The development of the ANN model presented difficulties, because the data set consisted of only 60 samples for 18 input (NMR) parameters and 1 output (CN) parameter. Therefore, the data set was compressed to 8 input parameters by training a primary neural network in which inputs and outputs were the same. The hidden layer of the developed primary network, containing eight nodes, was then used as the inputs and CN was used as the output for the development of the final network. The primary network for data compression and the final network for CN prediction were then appended together. The pattern set was appropriately divided into subsets for development and validation of the final model. The developed model when tested on the unseen data set, gave a very high correlation between the actual and predicted CN values.

Improving the Cetane Number of Diesel Fuels

Effect of paraffins C10-C13, C14-C17, C18-C23, tert-butyl hydroperoxide, cumyl hydroperoxide, and isopropyl nitrate as cetane number improvers for summer- and winter-grade diesel fuels, added in amount of 0.4-5 wt %, is studied.

Cetane Number Improvement of Diesel Fuel by Autoxidation

Diesel fuels having low cetane numbers may have ignition problems such as diesel knock, difficult engine starts in cold weather, and need for addition of cetane number improving agents. As organic peroxides are known to be effective cetane number improving additives, hydroperoxides produced in the autoxidation of hydrocarbons can be expected to improve cetane number. In this study, the cetane numbers of diesel fuels autoxidized in the liquid phase under various conditions have been examined. As a result, autoxidized diesel fuels have been found to have higher cetane numbers. Hydroperoxides are also found to be produced in the autoxidation of diesel fuels. It is suggested that hydroperoxides produced from diesel fuel autoxidation should have an important role in increasing its cetane number.

95/04508 Equations for predicting the cetane number of diesel fuels from their physical properties

95/04508 Equations for predicting the cetane number of diesel fuels from their physical properties

Equations for predicting the cetane number of diesel fuels from their physical properties

Twenty-two equations for predicting the cetane number of diesel fuels were tested for accuracy by comparing the predicted values for > 500 fuels with the measured values. All the equations and measured values were taken from the literature. It was found that the predictive capability of certain equations was high: several could predict the cetane number with a standard error of < 2. It is concluded that it is unlikely that the standard error can be reduced significantly below 1.5, because the measured cetane numbers are themselves subject to experimental error. The equations were unable to predict accurately the cetane number of untypical diesel fuels, such as vegetable oils and diesel blends containing alcohols. This was expected, since these empirical equations were constructed from databases for typical diesel fuels only. The measured cetane number of diesel fuels was found to correlate very well with their aniline point. Six of the 22 equations were functions of only the aniline point, and two of them showed very good predictive capability.

Prediction of Physical Properties and Cetane Number of Diesel Fuels and the Effect of Aromatic Hydrocarbons on These Entities.

The gross heat of combustion and cetane number of diesel fuels have been predicted from the experimental values of refractive index ; moreover, cetane number has also been predicted from the gross heat of combustion. These predicted values have agreed well with the experimental values. The effects of aromatic hydrocarbons (aromatics, single-ring aromatics, polynuclear aromatics) on such physical properties as density, refractive index, distillation temperature, kinematic viscosity, gross heat of combustion and cetane number of diesel fuels have been studied systematically. Density, refractive index, and distillation temperature (50% and 90%) increased with increasing mole fraction of polynuclear aromatics, but the gross heat of combustion and cetane number of diesel fuels decreased. The results showed that polynuclear aromatics affected the physical properties and cetane number of diesel fuels.

Two-stage hydroprocessing of synthetic crude gas oil

The hydrocracking of synthetic crude gas oils (SGO), which are commercially produced from Canadian oil sands, is strongly inhibited by nitrogen-containing species. To alleviate the pronounced effect of these nitrogenous compounds, SGO was hydrotreated at severe conditions prior to hydrocracking to reduce its N content from 1665 to about 390 ppm (by weight). Hydrocracking was then performed using a commercial nickel-tungsten catalyst supported on silica-alumina. Two-stage hydroprocessing of SGO was assessed in terms of product yields and quality. As expected, higher gas oil conversions were achieved mostly from an increase in naphtha yield. The middle distillate product quality was also clearly improved as the diesel fuel cetane number increased by 13%. Diesel engine tests indicated that particulate emissions in exhaust gases were lowered by 20%. Finally, pseudo first-order kinetic equations were derived for the overall conversion of the major gas oil components.