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. 2024 Feb 4;9(6):6296–6304. doi: 10.1021/acsomega.3c09216

Alternative Methods for Biodiesel Cetane Number Valuation: A Technical Note

Kedir Derbie Mekonnen †,*, Yassin Adem Endris ‡, Kedir Yesuf Abdu §
PMCID: PMC10870361  PMID: 38371778

Abstract

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Biodiesel is an environmentally beneficial and clean energy source that may replace fossil fuels, which are detrimental to the environment and cannot be replenished. Therefore, the physicochemical parameters of biodiesel must be determined in order to verify its quality. The cetane number is a crucial dimensionless fuel property that gauges the fuel ignition quality in power diesel engines. A higher cetane number results in a shorter ignition delay time, and vice versa. Biodiesel’s cetane number may fluctuate due to a variety of fatty acid compositions, including variations in carbon chain length and the degree of unsaturation. The cetane number generally increases with increasing saturation and chain length, while it decreases as chain length is reduced and degrees of unsaturation and branching increase. This is the main reason for why alkanes possess a higher cetane number than alkenes and aromatics. The standard protocols for evaluating the cetane number of biodiesel are ASTM D613 and ISO 5165 test techniques using a monocylindrical cetane engine. However, adhering to these conventional procedures is quite challenging and time-consuming, and the cetane number test result may also be affected by the presence of certain gases and fumes. As a result, many researchers are bothered with cetane number valuation, and occasionally they skip it due to a lack of other options. Consequently, the aim of this paper is to present a set of more straightforward and relevant alternative techniques that can be applied to predict the cetane number of biodiesel when engine-based measurement is not practical. The three techniques with their designed pictographic outlooks conferred in this article include color indicator titration, aniline point, and fatty acid composition-based methods. The reported values of these procedures meet the minimum cut point of the biodiesel cetane number required by ASTM D6751 (≥47) and exhibit minimal variation from the typical standard methods. Nevertheless, the above-mentioned techniques are not applicable to other alternative biofuels except biodiesel products because they have a direct implication on the characteristics of the fatty acid profiles of different oil precursors, such as carbon chain length, degree of saturation or unsaturation, and aromaticity, which make up monoalkyl esters.

1. Introduction

The environment is worsening and worldwide energy scarcity is increasing rapidly due to rapid industrial and metropolitan growth.1−6 The high energy demand is largely satisfied with the use of nonrenewable resources originating from coal, petroleum, and natural gas, which depletes and exhausted gradually.7,8 Apart from gradual depletion, the use of nonrenewable resources has led to atmospheric pollution and global warming.9−13 As a result, researchers worldwide have become motivated in terms of developing clean renewable alternative energy sources that could be readily available, environmentally sustainable, technologically feasible, and techno-economically competitive for socioeconomic prosperity.3,14−16 Previously, wide-ranging research has been performed to explore alternative energies for fossil resources,17 mainly focused on wind, hydropower, and solar.18 But, according to the 21st Century Renewable Energy Policy Network (REN 21), the production of biodiesel has been superior to that of other biofuels and could be an alternative fuel.5,17,19−21

Biodiesel is a liquid biofuel commonly made by the transesterification of triglycerides molecules (hydrophobic substances made from one mole of glycerol with three moles of fatty acids) with alcohol in the presence of a suitable catalyst. The end product contains fatty acids of alkyl esters.22−27 The common sources of biodiesel are various organic raw materials such as edible and nonedible vegetable oils obtained from soybean, canola, rapeseed, Jatropha, mustard, palm, beauty leaf, microalgae, mahua, rubber seed, animal fats, waste cooking oil, etc.12,16,28 However, the use of edible oils as biodiesel feedstock may contribute to price fluctuation and lack of supply due to the competition of human food intake. Therefore, nonedible oils could be promising for biodiesel production.29,30 The main advantages of using biodiesels over fossil fuels include biodiesel being considered a green technology because of its low toxicity and high biodegradability, renewability (as it is made from vegetable oils and animal oils), and relative safety (its higher flash point), less CO emission, versatility (could be used in diesel engine without hardware modification), high cetane number, etc.28,31−35 In addition to several advantages, the use of biodiesel has some drawbacks, such as lower spray speed plus inferior fuel atomization due to higher viscosity, lower calorific value, high corrosion in the copper strip, higher NOx emissions, and largely cold start problems in cold climate environment. Some of the proved systems used to reduce such demerits of biodiesel are blending it with petrol diesel at any ratio because of similar properties, and engine gas recirculation (EGR).1,23,28,36−38

Because of the extensive production and variety of feedstock used in transesterification, quality control of biodiesel with effective approaches is needed to determine its physicochemical properties.27 One of the most important dimensionless quality parameters is the cetane number, which describes the auto ignition characteristics guaranteed for the selection of biodiesel.39,40 The cetane number of biodiesel has been widely described in many literature reports. The standard test methods acceptable to assess cetane number of biodiesel are ASTM D613 and ISO 5165 procedures using a cetane engine,41,42 where the delay of a mixture of cetane and alpha-methylnaphthalene with known cetane number is compared to the fuel ignition delay. But, theses standard experimental determinations need a large quantity of fuel samples for measurement (about 500 mL) and are quite difficult and time-consuming, and hence, numerous predictive models based on some fuel properties have been established.43−49 Furthermore, certain fumes and gases present in the space where the test engine is situated might have a measurable impact on the result of the cetane number test.41 Since the cetane number is one of the most typical properties of biodiesel ignition delay after adding it to the combustion chamber, many researchers are troubled by its value determination when the cetane engine is not accessible and smaller measuring samples are presented. The purpose of this paper is to provide a collection of some simple and significant alternative techniques convenient for evaluating the cetane number of biodiesel to simplify the aforementioned challenges associated with engine-based standard measurements.

1.1. Fundamentals of Cetane Number (CN)

Cetane number is one of the most important fuel properties tha measure the autoignition characteristics of the fuel in a power diesel engine, mostly critical during cold starting engine conditions.38,49−51 This dimensionless number is highly responsible for ignition delay (the time interval between the start of fuel injection and the start of combustion), and it depends on the composition of the fuel. The higher the cetane number, the better the ignition quality and the shorter the ignition delay time. Thus, a fuel having a higher cetane number shows its higher combustibility, shorter ignition delay, and noiseless plus smoother fuel combustion, which determines the power as well as the economic performance of the engines. Conversely, lower cetane number leads to hard starting of the engine in cold environments, increased knocking, deposit formation caused by incomplete combustion, generation of pollutants from engine exhaust (hydrocarbons emissions) and affects the ignition delay.28,38,43,52−54 In this approach, cetane number affects not only the exact rate of heat release but also responsible for pollutant emission as well as radiation of combustion noise.43 As the fatty acids chain length and degree of saturation increased, the cetane number of biodiesel is also linearly improved. In this respect, alkanes possess higher cetane number than alkenes. Generally, biodiesel has greater cetane number relative to the pure conventional diesel fuels, due to the presence of saturated molecules, longer fatty acid carbon chains, and more oxygen contents associated with the carbonyl groups.28,43,45 The amount of oxygen that compos biodiesel ranges in 10–11% which can be used to increase the combustion efficiency of engines and decrease the fuel’s oxidation potential.17 The minimum values of the cetane number for biodiesel dictated by ASTM D6751 and EN 14214 standards are 47 and 51, respectively.43

1.2. Alternative Techniques

The proposed cetane number prediction methods based on the different physicochemical characteristics of biodiesel addressed in this paper include titration, aniline point, and fatty acid composition-based techniques. Their detailed information is explained below.

1.2.1. Titration Method from Saponification and Iodine Value

Saponification Value (ASTM D1962)

The saponification value of fuel represents the milligrams of KOH needed to saponify 1 g of sample.28 It measures the chain length and average molecular weight of fatty acids. A lower saponification value corresponds with long chain fatty acids due to fewer carboxylic functional groups being present in the unit mass of fat.54 One of the standard procedures for determining the saponification value of biodiesel is via the ASTM D1962 titration method. In this method, 1 g of sample is dissolved in 10 mL of ethanol followed by further addition of 25 mL of 0.5 N ethanolic KOH to the sample-solvent mixture and refluxing for 30 min, as shown in Figure 1 and which is termed as a test sample. Afterward, the sample is allowed to cool until it reaches room temperature. Finally, 2–3 drops of phenolphthalein indicator is added in to the cooled solution, and the excess KOH is titrated with 0.5 N HCl solution until the end point (disappeared of pink color) using a burette dropper as shown in Figure 1. The procedure for the blank titration (without sample) is similar to the sample test titration. Then, the saponification value is determined by eq 1.8,55

graphic file with name ao3c09216_m001.jpg 1

Where N is the normality of KOH, mol/mL; Vt is the volume of HCl consumed for the test sample titration, mL; Vb is the volume of HCl consumed for blank sample titration, mL; and WS is the weight of biodiesel sample, g.

Figure 1.

Figure 1

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Titration method for saponification value measurement.

Iodine Value (EN 14111)

Iodine value is defined as grams of iodine absorbed by 100 g of sample. It measures the degree of unsaturation in the biodiesel. High levels of unsaturation results polymerization of glycerides because of epoxide formation as a result of addition of oxygen in double bonds. This can lead to the formation of deposits and thus decline the lubricating properties of the fuel.8,54,56 However, the iodine value cannot be trusted for evaluating the unsaturation level since a composition with lots of fatty acids gives an equal iodine value. Thus, it is just a measure of the number of C=C bonds present and does not account for the position of the double bonds.57 In general, biodiesel with a low iodine value is more efficient and combustible than fuel with a higher value, but it could possess poor cold-flow characteristics.54 For biodiesel, the ASTM standard does not specify the iodine value;28 however, European standards EN 14213 and EN 14214 state iodine values of 130 and 120, respectively. The standard procedure for iodine value determination is EN 14111. In this technique, 10 mL of chloroform solvent is poured into two separate flasks as presented in Figure 2. In one flask, 1 g of biodiesel sample is added to be dissolved as a test, and the second flask containing only solvent is used as a blank. In both flasks, 20 mL of iodine monochloride reagent was added and thoroughly mixed followed by setting in a dark place for incubation for about 30 min. Subsequently, 10 mL of KI solution was added into each test sample by taking care of complete mixing by rinsing the beaker sides with 50 mL of distilled water. Both the test and blank samples were then titrated with 0.1 N sodium thiosulfate (Na2S2O3) aqueous solution until the color changed to pale straw. Next, 1 mL of starch indicator was added into both flasks and alteration of the color to purple could be observed. The solution was again back-titrated until the purple color changed to colorless. Finally, the iodine value can was determined by eq 2.8,55,58,59

graphic file with name ao3c09216_m002.jpg 2

Where N is the normality of Na2S2O3, mol/mL; Vb is the volume of Na2S2O3 for the blank sample, mL; Vt is the volume of Na2S2O3 for the test sample, mL; and WS is the weight of sample, g.

Figure 2.

Figure 2

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Titration method for iodine value measurement.

Based on the saponification and iodine values, the cetane number of biodiesel was then predicted with eq 3.8,53,60,61 For example, biodiesel derived from waste cooking oil,8 castor bean,59 Croton macrostachyus (Bisana) kernel oil,62 and Aegle Marmelos Correa55 shows cetane numbers of 57.11, 51.48, 50.78, and 58, respectively, which are acceptable and meet the ASTM D6751 specification.8,55

graphic file with name ao3c09216_m003.jpg 3

Where CN is the cetane number; IV is the iodine value; and SV is the saponification value.

1.2.2. Using Aniline Point (ASTM D4737)

Aniline (C6H5NH2) is an aromatic amine that can be used as a solvent selective to naphthenes and paraffins at higher temperatures, and aromatic molecules at low temperatures. Aniline is commonly used to evaluate the aromaticity of oil products via evaluating the aniline point. The aniline point is the lowest temperature at which equal volumes of oil based sample and aniline become completely miscible. When the aromaticity of the sample increases, the aniline point decreases because of the complete mixing at lower temperature. But the rise of the paraffinicity and the molecular weight of the oil product increase the aniline point. Olefins and naphthenes show values between aromatics and paraffins.63,64 In conditions where the cetane number test cannot be done by the ASTM D613 standard method in a monocylindrical engine, it is possible to follow the ASTM D4737 procedure using the cetane index and the aniline point through eqs 4–6. In this method, equal volumes of aniline and biodiesel sample (about 10 mL of each) are initially added in to a U-shaped glass test tube in which their immiscibility is clearly seen. A temperature reading thermometer is placed in to the test tube as revealed in Figure 3. Then, the mixture is gradually heated until it becomes a completely mixed, homogeneous solution. The temperature reading where the homogenate mixture observed is noted as the aniline point and converted to Fahrenheit. The aniline point of a fuel and its ignitability are correlated by an intermediate empirical expression of diesel index (DI), which is calculated based on the density of fuel, and finally the cetane number can be determined from it.25,38,63−65

1.2.2. 4
1.2.2. 5
1.2.2. 6

Where SG is specific gravity of biodiesel at 60 °F (15.5 °C).

Figure 3.

Figure 3

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Aniline point measurement

1.2.3. Using Fatty Acid Composition

The chemical composition of a feedstock determines the properties of the biodiesel being produced. Hence, the degree of unsaturation and fatty acid chain length are the important parameters in determining the physiochemical properties. The presence of saturation and long-chain fatty acids can increase the cetane number of biodiesel. Saturated fatty acids are fatty acids that do not contain a double bond in their structure, whereas unsaturated ones contain a double bond. The level of unsaturation is directly linked with the iodine value, and the molecular weight of fatty acids is connected with the saponification value.53,66,67 Thus, the fatty acid structure and the level of unsaturation influence the ignition delay, which upsets the performance and causes an increase in exhaust emissions. Therefore, the cetane number of biodiesel can be predicted from its fatty acid composition using the empirical correlation with the saponification and iodine values, eqs 7–9.40,53,54,68−75 The benefit of these equations is that the relative influence of each fatty acid component on the total iodine and saponification numbers can be simply evaluated.52 The iodine value decreased with chain length while growing linearly with an increasing degree of unsaturation. As both the carbon length and molecular weight increased, the saponification number decreased because of their inverse relationship. Similarly, the saponification number decreases as the degree of unsaturation increases. Moreover, a comparative study of the cetane number determination of biodiesel derived from six different feedstocks, i.e., coconut, palm kernel, soybean, corn, olive, and canola, using the fatty acid composition and ASTM D613 standard techniques has been reported in the literature. The individual fatty acid profiles and contributions of all derived biodiesel products to the saponification and iodine numbers are depicted in Figures 4a–f and 5a–f, respectively. Based on these values, the calculated cetane number and the measured ones using the standard techniques, as well as the errors committed between the two methods, are clearly shown in Table 1.54 The findings indicated that there is no noticeable difference between the calculated and measured cetane numbers, and hence, the suggested fatty acid composition method can reasonably predict the cetane number of biodiesel products.

1.2.3. 7
1.2.3. 8
1.2.3. 9

Where Ai is the percentage composition of each fatty acid in the oil or its ester; DB is the number of double bonds present in each unsaturated fatty acid or its ester; and Mwi is the molecular weight of each fatty acid or its ester component.

Figure 4.

Figure 4

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Contribution of fatty acid percentage to the saponification number of biodiesel derived from (a) coconut oil, (b) palm kernel oil, (c) soyabean oil, (d) corn oil, (e) olive oil, and (f) canola oil.

Figure 5.

Figure 5

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Graphical depiction of contribution of fatty acids to the iodine value of biodiesel derived from (a) coconut oil, (b) palm kernel oil , (c) soyabean oil, (d) corn oil, (e) olive oil, and (f) canola oil.

Table 1. Comparison of Biodiesel Cetane Number (CN) Determined with ASTM D613 and Analytical Methodsa,54.
Biodiesel Measured CN by ASTM D613 Calculated CN with eq 9 Absolute error Percent error (%) ASTM D6751 limit
Coconut 66.30 ± 1.04 65.85 ± 0.99 0.45 0.6787 ≥47
Palm kernel 62.50 ± 0.94 65.10 ± 0.98 2.60 4.1600
Soyabean 47.00 ± 0.71 45.51 ± 0.68 1.49 3.1702
Corn 48.20 ± 0.72 47.58 ± 0.71 0.62 1.2863
Olive 58.60 ± 0.88 56.44 ± 0.85 2.16 3.6860
Canola 48.50 ± 0.73 49.20 ± 0.74 0.7000 1.4433
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a

Absolute error = |Measured – Calculated|; Inline graphic

Conclusion

The article offers insightful details on the multiple approaches to biodiesel cetane number (ignition delay) valuation with their respective pictographic outlooks rather than adopting the extremely challenging and lengthy standard processes of ASTM D613 and ISO 5165. The aniline point, the color indication titration method based on saponification and iodine values, and the fatty acid composition-based approach with a committed average percentage error of 2.75% from the conventional monocylindrical cetane engine systems are some of the alternative schemes covered in this paper that exhibit minimal deviation. Moreover, the reported outcomes of these techniques meet the minimum cut point of the biodiesel cetane number specified in the ASTM D6751 requirement (≥47). However, the aforementioned alternative methods are not applicable for other biofuels, except biodiesel products, because they have a direct correlation with the fatty acid profiles of various oil precursors, like carbon chain length, degree of saturation or unsaturation, and aromaticity, which constitute monoalkyl esters. In general, the important alternative techniques to be applied when the cetane test engine is not possible are compiled and shared with researchers who are having trouble computing the biodiesel cetane number.

Acknowledgments

The authors acknowledge the scientific community for providing the different tactics used to forecast the cetane number of biodiesel in conditions where engine-based measurement is not possible.

The authors declare no competing financial interest.

References

  1. Mekonnen K.; Sendekie Z. NaOH-Catalyzed Methanolysis Optimization of Biodiesel Synthesis from Desert Date Seed Kernel Oil. ACS Omega 2021, 6 (37), 24082–24091. 10.1021/acsomega.1c03546. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Silitonga A. S.; Shamsuddin A. H.; Mahlia T. M. I.; Milano J.; Kusumo F.; Siswantoro J.; Dharma S.; Sebayang A. H.; Masjuki H. H.; Ong H. C. Biodiesel Synthesis from Ceiba Pentandra Oil by Microwave Irradiation-Assisted Transesterification: ELM Modeling and Optimization. Renewable Energy 2020, 146, 1278–1291. 10.1016/j.renene.2019.07.065. [DOI] [Google Scholar]
  3. Panchal B.; Chang T.; Kang Y.; Qin S.; Zhao Q.; Wang J.; Bian K.; Sun Y. Synthesis of Polymer Based Catalyst : Optimization and Kinetics Modeling of the Transesteri Fi Cation of Pistacia Chinensis Oil with Diethyl Carbonate Using Acidic Ionic Liquids. Fuel 2020, 276, 118121 10.1016/j.fuel.2020.118121. [DOI] [Google Scholar]
  4. Chand L.; Kumar K.; Gupta N.; Kumar S. A Review on Municipal Solid Waste as a Renewable Source for Waste-to- Energy Project in India : Current Practices, Challenges, and Future Opportunities. Journal of Cleaner Production 2020, 277, 123227 10.1016/j.jclepro.2020.123227. [DOI] [Google Scholar]
  5. Rezania S.; Oryani B.; Park J.; Hashemi B.; Yadav K. K.; Kwon E. E.; Hur J.; Cho J. Review on Transesteri Fi Cation of Non-Edible Sources for Biodiesel Production with a Focus on Economic Aspects, Fuel Properties and by-Product Applications. Energy Conversion and Management 2019, 201, 112155 10.1016/j.enconman.2019.112155. [DOI] [Google Scholar]
  6. Sahani S.; Roy T.; Sharma Y. C. Studies on Fast and Green Biodiesel Production from an Indigenous Nonedible Indian Feedstock Using Single Phase Strontium Titanate Catalyst. Energy Conversion and Management 2020, 203, 112180 10.1016/j.enconman.2019.112180. [DOI] [Google Scholar]
  7. Nisar N.; Mehmood S.; Nisar H.; Jamil S.; Ahmad Z.; Ghani N.; Oladipo A. A.; Qadri R. W.; Latif A. A.; Ahmad S. R.; Iqbal M.; Abbas M. Brassicaceae Family Oil Methyl Esters Blended with Ultra-Low Sulphur Diesel Fuel (ULSD): Comparison of Fuel Properties with Fuel Standards. Renewable Energy 2018, 117, 393–403. 10.1016/j.renene.2017.10.087. [DOI] [Google Scholar]
  8. Sahar; Sadaf S.; Iqbal J.; Ullah I.; Bhatti H. N.; Nouren S.; Habib-ur-Rehman; Nisar J.; Iqbal M. Biodiesel Production from Waste Cooking Oil : An Efficient Technique to Convert Waste into Biodiesel. Sustainable Cities and Society 2018, 41, 220–226. 10.1016/j.scs.2018.05.037. [DOI] [Google Scholar]
  9. Ma Y.; Liu Y.. Biodiesel Production, 2nd ed.; Elsevier, 2019. 10.1016/B978-0-12-816856-1.00021-X [DOI] [Google Scholar]
  10. Mishra V. K.; Goswami R. A Review of Production, Properties and Advantages of Biodiesel. Biofuels 2018, 9, 273–289. 10.1080/17597269.2017.1336350. [DOI] [Google Scholar]
  11. Shinde K.; Kaliaguine S. A Comparative Study of Ultrasound Biodiesel Production Using Different Homogeneous Catalysts. chemengineering 2019, 3, 18. 10.3390/chemengineering3010018. [DOI] [Google Scholar]
  12. Thangaraj B.; Solomon P. R.; Muniyandi B.; Ranganathan S.; Lin L. Catalysis in Biodiesel Production — a Review. Clean Energy 2019, 3, 2–23. 10.1093/ce/zky020. [DOI] [Google Scholar]
  13. Mekonnen K. D. Fourier Transform Infrared Spectroscopy as a Tool for Identifying the Unique Characteristic Bands of Lipid in Oilseed Components: Confirmed via Ethiopian Indigenous Desert Date Fruit. Heliyon 2023, 9 (4), e14699 10.1016/j.heliyon.2023.e14699. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Arshad M.; Bano I.; Khan N.; Shahzad M. I.; Younus M.; Abbas M.; Iqbal M. Electricity Generation from Biogas of Poultry Waste : An Assessment of Potential and Feasibility in Pakistan. Renewable and Sustainable Energy Reviews 2018, 81, 1241–1246. 10.1016/j.rser.2017.09.007. [DOI] [Google Scholar]
  15. Leng L.; Li W.; Li H.; Jiang S.; Zhou W. Cold Flow Properties of Biodiesel and the Improvement Methods: A Review. Energy Fuels 2020, 34 (9), 10364–10383. 10.1021/acs.energyfuels.0c01912. [DOI] [Google Scholar]
  16. Ong H. C.; Tiong Y. W.; Goh B. H. H.; Gan Y. Y.; Mofijur M.; Fattah I.M. R.; Chong C. T.; Alam M. A.; Lee H. V.; Silitonga A.S.; Mahlia T.M.I Recent Advances in Biodiesel Production from Agricultural Products and Microalgae Using Ionic Liquids : Opportunities and Challenges. Energy Conversion and Management 2021, 228, 113647 10.1016/j.enconman.2020.113647. [DOI] [Google Scholar]
  17. Mahlia T.M.I.; Syazmi Z.A.H.S.; Mofijur M.; Abas A.E. P.; Bilad M.R.; Ong H. C.; Silitonga A.S. Patent Landscape Review on Biodiesel Production : Technology Updates. Renewable and Sustainable Energy Reviews 2020, 118 (2019), 109526 10.1016/j.rser.2019.109526. [DOI] [Google Scholar]
  18. Li G.; Zhang J.; Li H.; Hu R.; Yao X.; Liu Y. Towards High-Quality Biodiesel Production from Microalgae Using Original and Anaerobically-Digested Livestock Wastewater. Chemosphere 2020, 128578 10.1016/j.chemosphere.2020.128578. [DOI] [PubMed] [Google Scholar]
  19. Conceição J. N.; Marangoni B. S.; Michels F. S.; Oliveira I. P.; Passos W. E.; Trindade M. A. G.; Oliveira S. L.; Caires A. R. L. Evaluation of Molecular Spectroscopy for Predicting Oxidative Degradation of Biodiesel and Vegetable Oil : Correlation Analysis between Acid Value and UV – Vis Absorbance and Fl Uorescence. Fuel Process. Technol. 2019, 183, 1–7. 10.1016/j.fuproc.2018.10.022. [DOI] [Google Scholar]
  20. Srinivasan G. R.; Shankar V.; Chandra Sekharan S.; Munir M.; Balakrishnan D.; Mohanam A.; Jambulingam R. Influence of Fatty Acid Composition on Process Optimization and Characteristics Assessment of Biodiesel Produced from Waste Animal Fat. Energy Sources, Part A: Recovery, Utilization and Environmental Effects 2020, 00 (00), 1–19. 10.1080/15567036.2020.1771477. [DOI] [Google Scholar]
  21. Xiao M.; Lin D.; Li Z.; Zhao J.; Long X.; Wu Z. Synthesis of Biodiesel from Waste Cooking Oil by One-Step Esterification and Its Structural Characterization. Waste and Biomass Valorization 2020, 11 (5), 2087–2100. 10.1007/s12649-018-0500-x. [DOI] [Google Scholar]
  22. Sukasem N.; Manophan S. The Development of Biodiesel Production from and Vegetable Oils by Using Different Proportions of Lime Catalyst and Assessing the Feasibility of Using the Heat Demand-Outdoor Sodium Hydroxide Temperature Function. Energy Procedia 2017, 138, 991–997. 10.1016/j.egypro.2017.10.108. [DOI] [Google Scholar]
  23. Ayoob A. K.; Fadhil A. B. Valorization of Waste Tires in the Synthesis of an Effective Carbon Based Catalyst for Biodiesel Production from a Mixture of Non-Edible Oils. Fuel 2020, 264, 116754 10.1016/j.fuel.2019.116754. [DOI] [Google Scholar]
  24. Bhoi R.; Singh D.; Mahajani S. Reaction Chemistry & Engineering Simultaneous Esterification and Transesterification. Reaction Chemistry & Engineering 2017, 2, 740–753. 10.1039/C6RE00218H. [DOI] [Google Scholar]
  25. De A.; Boxi S. S. Application of Cu Impregnated TiO2 as a Heterogeneous Nanocatalyst for the Production of Biodiesel from Palm Oil. Fuel 2020, 265, 117019 10.1016/j.fuel.2020.117019. [DOI] [Google Scholar]
  26. Encinar J.; Pardal A.; Sanchez N.; Nogales S.; et al. Biodiesel by Transesterification of Rapeseed Oil Using Ultrasound : A Kinetic Study of Base-Catalysed Reactions. Energies 2018, 11, 2229. 10.3390/en11092229. [DOI] [Google Scholar]
  27. Soares S.; Rocha F. R. P. Green Volumetric Procedure for Determining Biodiesel Content in Diesel Blends or Mixtures with Vegetable Oils Exploiting Solubility Differences in an Ethanol : Water Medium. Fuel 2020, 276, 118042 10.1016/j.fuel.2020.118042. [DOI] [Google Scholar]
  28. Singh D.; Sharma D.; Soni S. L.; Sharma S.; Kumari D. Chemical Compositions, Properties, and Standards for Different Generation Biodiesels : A Review. Fuel 2019, 253, 60–71. 10.1016/j.fuel.2019.04.174. [DOI] [Google Scholar]
  29. Chamola R.; Khan M. F.; Raj A.; Verma M.; Jain S. Response Surface Methodology Based Optimization of in Situ Transesterification of Dry Algae with Methanol, H2SO4 and NaOH. Fuel 2019, 239, 511–520. 10.1016/j.fuel.2018.11.038. [DOI] [Google Scholar]
  30. Gupta J.; Agarwal M.; Dalai A. K. Intensified Transesterification of Mixture of Edible and Nonedible Oils in Reverse Flow Helical Coil Reactor for Biodiesel Production. Renewable Energy 2019, 134, 509–525. 10.1016/j.renene.2018.11.057. [DOI] [Google Scholar]
  31. Syafiuddin A.; Chong J. H.; Yuniarto A.; Hadibarata T. The Current Scenario and Challenges of Biodiesel Production in Asian Countries: A Review. Bioresource Technology Reports 2020, 12 (July), 100608 10.1016/j.biteb.2020.100608. [DOI] [Google Scholar]
  32. Grabowski P.; Tomkielski D.; Szajerski P.; Gwardiak H. Changes of Biodiesel Composition after Electron Beam Irradiation. Journal of Radioanalytical and Nuclear Chemistry 2019, 319 (3), 727–736. 10.1007/s10967-018-6364-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Sanchez-Arreola E.; Martin-Torres G.; Lozada-Ramirez J. D.; Hernandez L. R.; Bandala-Gonzalez E. R.; Bach H. Biodiesel Production and De-Oiled Seed Cake Nutritional Values of a Mexican Edible Jatropha Curcas. Renewable Energy journal 2015, 76, 143–147. 10.1016/j.renene.2014.11.017. [DOI] [Google Scholar]
  34. Kamil M.; Ramadan K.; Olabi A. G.; Ghenai C.; Inayat A.; Rajab M. H. Desert Palm Date Seeds as a Biodiesel Feedstock:Extraction, Characterization, and Engine Testing Mohammed. Energy 2019, 12, 3147. 10.3390/en12163147. [DOI] [Google Scholar]
  35. Ezeldin Osman M.; Sheshko T. F.; Dipheko T. D.; Abdallah N. E.; Hassan E. A.; Ishak C. Y. Synthesis and Improvement of Jatropha Curcas L. Biodiesel Based on Eco-Friendly Materials. International Journal of Green Energy 2021, 18 (13), 1396–1404. 10.1080/15435075.2021.1904943. [DOI] [Google Scholar]
  36. Dharma S.; Masjuki H.H.; Ong H. C.; Sebayang A.H.; Silitonga A.S.; Kusumo F.; Mahlia T.M.I. Optimization of Biodiesel Production Process for Mixed Jatropha Curcas – Ceiba Pentandra Biodiesel Using Response Surface Methodology. Energy Conversion and Management 2016, 115, 178–190. 10.1016/j.enconman.2016.02.034. [DOI] [Google Scholar]
  37. Izida T.; Silva J. R.; Andrade L. H. C.; Simionatto E.; Simionatto E. L.; Scharf D. R.; Lima S. M. Modeling Transesterification Reaction Kinetics Using Fluorescence Spectroscopy to Interpret Biodiesel Production. Chem. Eng. Sci. 2020, 211, 115292 10.1016/j.ces.2019.115292. [DOI] [Google Scholar]
  38. Sani S.; Kaisan M. U.; Kulla D. M.; Obi A. I.; Jibrin A.; Ashok B. Industrial Crops & Products Determination of Physico Chemical Properties of Biodiesel from Citrullus Lanatus Seeds Oil and Diesel Blends. Industrial Crops & Products 2018, 122, 702–708. 10.1016/j.indcrop.2018.06.002. [DOI] [Google Scholar]
  39. Yasar F. Comparision of Fuel Properties of Biodiesel Fuels Produced from Di Ff Erent Oils to Determine the Most Suitable Feedstock Type. Fuel 2020, 264, 116817. 10.1016/j.fuel.2019.116817. [DOI] [Google Scholar]
  40. Mofijur M.; Rasul M. G.; Hassan N. M. S.; Masjuki H. H.; Kalam M. A.; Mahmudul H. M. Assessment of Physical, Chemical, and Tribological Properties of Different Biodiesel Fuels. In Clean Energy for Sustainable Development 2017, 441–463. 10.1016/B978-0-12-805423-9.00014-4. [DOI] [Google Scholar]
  41. ASTM D613-03: Standard Test Method for Cetane Number of Diesel Fuel Oil; ASTM International, 2003; Vol. 14, pp 1–31.
  42. ISO 5165: Petroleum Products — Determination of the Ignition Quality of Diesel Fuels — Cetane Engine Method; ISO, 1998; pp 1–7.
  43. Giakoumis E. G.; Sarakatsanis C. K. A Comparative Assessment of Biodiesel Cetane Number Predictive Correlations Based on Fatty Acid Composition. Energies 2019, 12 (3), 422. 10.3390/en12030422. [DOI] [Google Scholar]
  44. Martinez G.; Sanchez N.; Encinar J.M.; Gonzalez J.F. Fuel Properties of Biodiesel from Vegetable Oils and Oil Mixtures. Influence of Methyl Esters Distribution. Biomass and Bioenergy 2014, 63, 22. 10.1016/j.biombioe.2014.01.034. [DOI] [Google Scholar]
  45. Bhavani A. G.; Sharma V. K. Production of Biodiesel from Waste Cooking Oil: A Review. Journal of Advanced Chemical Sciences 2018, 4 (1), 549–555. 10.30799/jacs.181.18040105. [DOI] [Google Scholar]
  46. Luning Prak D.; Cooke J.; Dickerson T.; McDaniel A.; Cowart J. Cetane Number, Derived Cetane Number, and Cetane Index: When Correlations Fail to Predict Combustibility. Fuel 2021, 289, 119963 10.1016/j.fuel.2020.119963. [DOI] [Google Scholar]
  47. Singh D.; Sharma D.; Soni S. L.; Inda C. S.; Sharma S.; Sharma P. K.; Jhalani A. A Comprehensive Review on 1st-Generation Biodiesel Feedstock Palm Oil: Production, Engine Performance, and Exhaust Emissions. Bioenergy Research 2021, 14 (1), 1. 10.1007/s12155-020-10171-2. [DOI] [Google Scholar]
  48. Neupane D.; Bhattarai D.; Ahmed Z.; Das B.; Pandey S.; Solomon J. K. Q.; Qin R.; Adhikari P. Growing Jatropha (Jatropha Curcas l.) as a Potential Second-generation Biodiesel Feedstock. Inventions 2021, 6 (4), 60. 10.3390/inventions6040060. [DOI] [Google Scholar]
  49. Vera-Rozo J. R.; Saez-Bastante J.; Carmona-Cabello M.; Riesco-Avila J. M.; Avellaneda F.; Pinzi S.; Dorado M. P. Cetane Index Prediction Based on Biodiesel Distillation Curve. Fuel 2022, 321, 124063. 10.1016/j.fuel.2022.124063. [DOI] [Google Scholar]
  50. Alviso D.; Zárate C.; Duriez T. Modeling of Vegetable Oils Cloud Point, Pour Point, Cetane Number and Iodine Number from Their Composition Using Genetic Programming. Fuel 2021, 284, 119026 10.1016/j.fuel.2020.119026. [DOI] [Google Scholar]
  51. Mekonnen K. D.; Hailemariam K. Valorization of Calcium Hypochlorite Precipitate as a New Source of Heterogeneous Catalyst Development for Biodiesel Production : A Preliminary Experiment. Heliyon 2023, 9 (11), e21959 10.1016/j.heliyon.2023.e21959. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Folayan A. J.; Anawe P. A. L.; Aladejare A. E.; Ayeni A. O. Experimental Investigation of the Effect of Fatty Acids Configuration, Chain Length, Branching and Degree of Unsaturation on Biodiesel Fuel Properties Obtained from Lauric Oils, High-Oleic and High-Linoleic Vegetable Oil Biomass. Energy Reports 2019, 5, 793–806. 10.1016/j.egyr.2019.06.013. [DOI] [Google Scholar]
  53. Patel A.; Arora N.; Mehtani J.; Pruthi V.; Pruthi P. A. Assessment of Fuel Properties on the Basis of Fatty Acid Profiles of Oleaginous Yeast for Potential Biodiesel Production. Renewable and Sustainable Energy Reviews 2017, 77, 604–616. 10.1016/j.rser.2017.04.016. [DOI] [Google Scholar]
  54. Folayan A. J.; Anawe P. A. L.; Aladejare A. E.; Ayeni A. O. Experimental Investigation of the Effect of Fatty Acids Configuration, Chain Length, Branching and Degree of Unsaturation on Biodiesel Fuel Properties Obtained from Lauric Oils, High-Oleic and High-Linoleic Vegetable Oil Biomass. Energy Reports 2019, 5, 793–806. 10.1016/j.egyr.2019.06.013. [DOI] [Google Scholar]
  55. Thangarasu V.; Anand R.. Physicochemical Fuel Properties and Tribological Behavior of Aegle Marmelos Correa Biodiesel. In Advances in Eco-Fuels for a Sustainable Environment.; Elsevier, 2019; pp 309–336. 10.1016/b978-0-08-102728-8.00011-5 [DOI] [Google Scholar]
  56. He D.; Liu L.. Analytical Aspects of Rice Bran Oil; Elsevier, 2019. 10.1016/B978-0-12-812828-2.00007-X [DOI] [Google Scholar]
  57. Aghbashlo M.; Peng W.; Tabatabaei M.; Kalogirou S. A.; Soltanian S.; Hosseinzadeh-Bandbafha H.; Mahian O.; Lam S. S. Machine Learning Technology in Biodiesel Research: A Review. Prog. Energy Combust. Sci. 2021, 85, 100904 10.1016/j.pecs.2021.100904. [DOI] [Google Scholar]
  58. Saluja R. K.; Kumar V.; Sham R. Stability of Biodiesel – A Review. Renewable and Sustainable Energy Reviews 2016, 62, 866–881. 10.1016/j.rser.2016.05.001. [DOI] [Google Scholar]
  59. Asmare M.; Gabbiye N. Synthesis and Characterization of Biodiesel from Castor Bean as Alternative Fuel for Diesel Engine. American Journal of Energy Engineering 2014, 2 (1), 1–15. 10.11648/j.ajee.20140201.11. [DOI] [Google Scholar]
  60. lyer R. Comments on Reporting Cetane Index as Cetane Number for Biodiesel. Biofuels 2014, 5 (March), 565–568. 10.1080/17597269.2014.1002997. [DOI] [Google Scholar]
  61. Krisnangkura K. A Simple Method for Estimation of Cetane Index of Vegetable Oil Methyl Esters. Journal of the American Oil Chemists Society 1986, 63 (4), 552–553. 10.1007/BF02645752. [DOI] [Google Scholar]
  62. Zamba Z. Z.; Reshad A. S. Synthesis of Fatty Acid Methyl Ester from Croton Macrostachyus (Bisana) Kernel Oil: Parameter Optimization, Engine Performance, and Emission Characteristics for Croton Macrostachyus Kernel Oil Fatty Acid Methyl Ester Blend with Mineral Diesel Fuel. ACS Omega 2022, 7, 20619–20633. 10.1021/acsomega.2c00682. [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Sadeghbeigi R. FCC Feed Characterization. Fluid Catalytic Cracking Handbook 2020, 47–81. 10.1016/B978-0-12-812663-9.00004-7. [DOI] [Google Scholar]
  64. Olubunmi B. E.; Karmakar B.; Aderemi O. M.; G A. U.; Auta M.; Halder G. Parametric Optimization by Taguchi L9 Approach towards Biodiesel Production from Restaurant Waste Oil Using Fe-Supported Anthill Catalyst. Journal of Environmental Chemical Engineering 2020, 8 (5), 104288 10.1016/j.jece.2020.104288. [DOI] [Google Scholar]
  65. Nalgundwar A.; Paul B.; Sharma S. K. Comparison of Performance and Emissions Characteristics of Di CI Engine Fueled with Dual Biodiesel Blends of Palm and Jatropha. Fuel 2016, 173, 172–179. 10.1016/j.fuel.2016.01.022. [DOI] [Google Scholar]
  66. Kumar V.; Thakur I. S. Bioresource Technology Reports Extraction of Lipids and Production of Biodiesel from Secondary Tannery Sludge by in Situ Transesterification. Bioresource Technology Reports 2020, 11 (April), 100446 10.1016/j.biteb.2020.100446. [DOI] [Google Scholar]
  67. Contreras J.; Valdés O.; Mirabal-Gallardo Y.; de la Torre A. F.; Navarrete J.; Lisperguer J.; Durán-Lara E. F.; Santos L. S.; Nachtigall F. M.; Cabrera-Barjas G.; Abril D. Development of Eco-Friendly Polyurethane Foams Based on Lesquerella Fendleri (A. Grey) Oil-Based Polyol. Eur. Polym. J. 2020, 128 (March), 109606 10.1016/j.eurpolymj.2020.109606. [DOI] [Google Scholar]
  68. Ibrahim A. G.; Baazeem A.; Al-zaban M. I.; Fawzy M. A.; Hassan S. H. A.; Koutb M. Sustainable Biodiesel Production from a New Oleaginous Fungus, Aspergillus Carneus Strain OQ275240 : Biomass and Lipid Production Optimization Using Box – Behnken Design. Sustainability 2023, 15, 6836. 10.3390/su15086836. [DOI] [Google Scholar]
  69. Oladipo B.; Betiku E. Optimization and Kinetic Studies on Conversion of Rubber Seed (Hevea Brasiliensis) Oil to Methyl Esters over a Green Biowaste Catalyst. Journal of Environmental Management 2020, 268, 110705 10.1016/j.jenvman.2020.110705. [DOI] [PubMed] [Google Scholar]
  70. Huo K.; Shui L.; Mai Y.; Zhou N.; Liu Y.; Zhang C.; Niu J. Effects of Exogenous Abscisic Acid on Oil Content, Fatty Acid Composition, Biodiesel Properties and Lipid Components in Developing Siberian Apricot (Prunus Sibirica) Seeds. Plant Physiology and Biochemistry 2020, 154, 260–267. 10.1016/j.plaphy.2020.06.020. [DOI] [PubMed] [Google Scholar]
  71. Ma Y.; Wang S.; Liu X.; Yu H.; Yu D.; Li G.; Wang L. Oil Content, Fatty Acid Composition and Biodiesel Properties among Natural Provenances of Siberian Apricot (Prunus Sibirica L.) from China. GCB Bioenergy 2021, 13 (1), 112–132. 10.1111/gcbb.12759. [DOI] [Google Scholar]
  72. Ahmad T.; Danish M.; Kale P.; Geremew B.; Adeloju S. B.; Nizami M.; Ayoub M. Optimization of Process Variables for Biodiesel Production by Transesterification of Flaxseed Oil and Produced Biodiesel Characterizations. Renewable Energy 2019, 139, 1272–1280. 10.1016/j.renene.2019.03.036. [DOI] [Google Scholar]
  73. Mohibbeazam M.; Waris A.; Nahar N. M. Prospects and Potential of Fatty Acid Methyl Esters of Some Non-Traditional Seed Oils for Use as Biodiesel in India. Biomass and Bioenergy 2005, 29, 293–302. 10.1016/j.biombioe.2005.05.001. [DOI] [Google Scholar]
  74. Uddin M.N.; Techato K.; Rasul M.G.; Hassan N.M.S.; Mofijur M. Waste Coffee Oil : A Promising Source for Heating Biodiesel Production. Energy Procedia 2019, 160, 677–682. 10.1016/j.egypro.2019.02.221. [DOI] [Google Scholar]
  75. Bose P. K. Empirical Approach for Predicting the Cetane Number of Biodiesel. International Journal of Automotive Technology 2009, 10 (4), 421. 10.1007/s12239-009-0048-7. [DOI] [Google Scholar]

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