Study of antioxidant effect on oxidation stability and emissions in a methyl ester of neem oil fuelled DI diesel engine

Biodiesel as an alternative diesel fuel prepared from vegetable oils or animal fats has attracted more and more attention because of its renewable and environmental-friendly nature. But biodiesel undergoes oxidation and degenerate more quickly than mineral diesel. Further several studies report NO_x emissions increases for biodiesel fuel compared with conventional diesel fuel. In this paper, the experimental investigation of the effect of antioxidant additive (Butylated hydroxytoluene) on oxidation stability and NO_x emissions in a methyl ester of neem oil fuelled direct injection diesel engine has been reported. The antioxidant additive is mixed in various proportions (100–400 ppm) with methyl ester of neem oil. The oxidation stability was tested in Rancimat apparatus and emissions, performance in a computerized 4-stroke water-cooled single cylinder diesel engine of 3.5 kW rated power. Results show that the antioxidant additive is effective in increasing the oxidation stability and in controlling the NO_x emissions of methyl ester of neem oil fuelled diesel engines.     

Parametric studies on the storage stability and aging effect of biodiesel treated with Eucalyptus oil as a cost-effective green-antioxidant additive

Oxidation stability is one of the most significant fuel quality standards for biodiesel and mainly distresses the stability of biodiesel. Therefore, the present work aims to report the Eucalyptus oil (EO) as a natural green antioxidant additive to evaluate the oxidation stability of biodiesel produced from dairy waste scum, Bauhinia variegata and Butea monosperma oil. The obtained results have also been compared with the conventional synthetic antioxidant, butylated hydroxy toluene (BHT). The oxidation stability of the biodiesel treated with these additives was evaluated using the professional biodiesel Rancimat instrument. Further, the fuel properties kinematic viscosity and acid value were measured during the storage period. The obtained results showed an increase in the induction period in the biodiesel sample treated with EO, indicating a protective effect and inhibiting the oxidation initiation step. As a result, the oxidation stability of dairy waste scum methyl ester (DWSME), B variegata methyl ester (BVME) and B monosperma methyl ester (BMME) was found to be ~10, ~8 and ~8 hours, respectively, during 90 days storage when the natural antioxidant EO with a concentration of 4000 ppm was used and these obtained values were in the limit of EN 14214 standard. Interestingly, these values were found to be on par with the oxidation stability of DWSME (~11 hours), BVME (~9 hours) and BMME (~9 hours), when the synthetic antioxidant BHT was used with a concentration of 3000 ppm during the 90 days storage. Although the addition of EO as antioxidant resulted in increase in kinematic viscosity and acid value of the biodiesel samples, those values well-fall in the ASTM 6751 standard limit. On the other hand, synthetic antioxidant BHT showed enhanced results as compared to the EO. However, the effectiveness of the proposed natural antioxidant additive (EO) is on par with the synthetic antioxidant (BHT), which can be replaced for cost-effectiveness, non-toxic and safer consumption of biodiesel as compared to synthetic antioxidant-treated biodiesel.     

Enhancing the oxidation stability of Mahua oil methyl ester with the addition of natural antioxidants

A rapid decrease in the availability of non-renewable fossil fuels has initiated the search for alternative fuels. Biodiesel obtained from various feedstocks has proved to be an effective alternative source for diesel engines due to its convincing fuel characteristics. The oxidation property of biodiesel is influenced by external factors such as sunlight and exposure to atmosphere.The oxidation stability of biodiesel can be improved by the addition of antioxidants which may be synthetic or natural. Natural antioxidants are more effective than synthetic ones in terms of economic value as well as prevention of adverse carcinogenic effects. Natural antioxidants, namely, ginger, Moringa oleifera, oregano, basil, and clove were extracted and used for the present study. The antioxidant activity of the additives was analyzed by DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The DPPH scavenging effect was calculated in terms of % by using absorbance values recorded with UV spectrophotometer. Among the antioxidants used, clove additive was found to be more efficient in enhancing the oxidation stability, with scavenging effect of 42.23%, 47.67%, 51.62%, and 55.61% for 500, 1000, 1500, and 2000 ppm, respectively. It was also observed that the scavenging activity increased with the concentration of antioxidant additives, and the maximum value was recorded at a concentration of 2000 ppm. Mahua oil methyl ester (MOME) was selected as biodiesel for the present study for which the oxidation stability has to be evaluated. The oxidation stability of MOME was measured in terms of induction period using the Rancimat method which does not meet the required standards. The oxidation stability of MOME, MOME + ginger 2000, MOME + M. oleifera 2000, MOME + oregano 2000, MOME + basil 2000, and MOME + clove 2000 was evaluated. The highest induction period was observed to be 38.44 h for MOME + clove 2000 blend. Hence, clove additive was found to be more effective among the selected natural antioxidants in terms of increasing the scavenging effect as well as increasing the oxidation stability of MOME. Thus, the addition of natural antioxidants can be recommended to improve the oxidation stability of biodiesel based on their scavenging effect which can be further validated by means of the Rancimat method in terms of the induction period     

Effect of natural antioxidants on the oxidation stability of methyl ester of rubber seed oil

Biodiesel has been proved as a promising solution amidst other alternate fuels in terms of its characteristics compared to diesel. The oxidation property of biodiesel results in the degradation of its quality. This problem can be solved by the addition of suitable antioxidants which improves the oxidation stability of the fuel. Usage of natural antioxidants offsets the defects in synthetic antioxidants, because they are renewable, nontoxic as well as cost effective. The effect of natural antioxidant additives on the oxidation stability of the Methyl Ester of non-edible Rubber Seed oil (MERB) has been experimentally investigated in this study. Natural antioxidants Ginger, Moringa oleifera Lam, Basil and Oregano have been mixed in varying proportions (500, 1000, 1500 and 2000 ppm) and the antioxidant characteristics of the additives were identified by using Fourier Transform Infra-Red (FTIR) analysis. The induction period, which denotes the oxidation stability was worked out with Rancimat apparatus. From this study it was found out that the oxidation stability of MERB increased when natural antioxidant additives were added. Among the antioxidants used, Ginger was found to be more effective in enhancing the oxidation stability, with induction period values of 11.5 h, 18.5 h, 23 h and 26.5 h for proportions 500, 1000, 1500 and 2000 ppm respectively.     

生物柴油与柴油热稳定性对比和热动力学分析

利用热重分析技术对生物柴油和0#柴油进行燃烧特性分析,比较两者的热稳定性。根据DTG-DTA曲线及实验数据,利用Achar微分法和Coats-Redfen积分法计算了活化能,并推断出生物柴油和柴油在低温段和高温段的非等温动力学方程。实验表明:生物柴油的挥发分较高,易于燃烧;但低温段表面活化能高于生物柴油,热稳定性优于柴油。     

An overview of biodiesel oxidation stability

Oxidation Stability is one of the most important properties of fatty acid alkyl esters (biodiesel fuel) and primarily affects the stability of biodiesel during extended storage. Degradation by oxidation yields products that may compromise fuel properties, impair fuel quality and engine performance. In Europe, standardization and fuel quality assurance are crucial factors for biodiesel market acceptance, and storage stability is one of the main quality criteria. An overview of researches into biodiesel oxidation stability is presented in an attempt to convey the significance of this important property of biodiesel fuel. Aspects covered include: significance of biodiesel oxidation stability, oxidation chemistry, methods used for characterization of stability, factors known to influence stability, and consequences of biodiesel oxidation for diesel engines. The purpose of this work was to review the findings from some of the key prior research efforts available in the literature and to identify aspects of biodiesel oxidation stability in need of further study.     

Synergistic effect of metal deactivator and antioxidant on oxidation stability of metal contaminated Jatropha biodiesel

Biodiesel is relatively unstable on storage and European biodiesel standard EN-14214 calls for determining oxidation stability at 110 °C with a minimum induction time of 6 h by the Rancimat method (EN-14112). According to proposed National Mission on biodiesel in India, we have undertaken studies on stability of biodiesel from tree borne non-edible oil seeds Jatropha. Neat Jatropha biodiesel exhibited oxidation stability of 3.95 h. It is found possible to meet the desired EN specification for neat Jatropha biodiesel and metal contaminated Jatropha biodiesel by using antioxidants; it will have a cost implication, as antioxidants are costly chemicals. Research was conducted to increase the oxidation stability of metal contaminated Jatropha biodiesel by doping metal deactivator with antioxidant, with varying concentrations in order to meet the aforementioned standard required for oxidation stability. It was found that usage of antioxidant can be reduced by 30–50%, therefore the cost, even if very small amount of metal deactivator is doped in Jatropha biodiesel to meet EN-14112 specification.     

Study of the oxidation stability and exhaust emission analysis of Moringa olifera biodiesel in a multi-cylinder diesel engine with aromatic amine antioxidants

In this study, the two most effective aromatic amine antioxidants N,N′-diphenyl-1,4-phenylenediamine (DPPD) and N-phenyl-1,4-phenylenediamine (NPPD), were used at a concentration of 2000 ppm. The impact of antioxidants on the oxidation stability, exhaust emission and engine performance of a multi-cylinder diesel engine fuelled with MB20 (20% Moringa oil methyl ester and 80% diesel fuel blend) were analysed at varying speed conditions at an interval of 500 rpm and a constant load. It was observed that, blending with diesel enhanced the oxidation stability of the moringa biodiesel by approximately 6.97 h, and the addition of DPPD and NPPD to MB20 increased the oxidation stability up to 34.5 and 18.4 h, respectively. The results also showed that the DPPD- and NPPD-treated blends reduced the NOx emission by 7.4% and 3.04%, respectively, compared to the untreated blend. However, they do have higher carbon monoxide (CO) and hydrocarbon (HC) levels and smoke opacities, but it should be noted that these emissions are still well below the diesel fuel emission level. The results show that the addition of antioxidant with MB20 also improves the engine's performance characteristics. Based on this study, MB20 blends with amine antioxidants can be used in diesel engines without any modification.     

Effect of fuel on the soot nanostructure and consequences on loading and regeneration of diesel particulate filters

An automotive diesel engine was tested in three representative modes of soot accumulation, active regeneration and spontaneous regeneration of its catalyzed diesel particulate filter (DPF), among the typical driving operation modes. During the engine tests, pressure and temperature along the DPF were measured, and soot samples were taken from the exhaust manifold upstream of the DPF for their thermal, structural and morphological characterization. The collected soot samples were subjected to: Transmission Electron Microscopy (TEM) for morphological analysis, thermal heating under oxidant atmosphere for studying the oxidation kinetics, Raman spectroscopy for describing their nanostructure and X-ray diffraction spectroscopy (XRD) for studying their internal lattice parameters. When the engine was operated in a typical accumulation mode, the pressure drop across the DPF increased up to 80 hPa with diesel fuel, while pressure drop stopped increasing after 4000 s of engine testing with biodiesel. In the regeneration mode, the DPF regenerated more slowly in the biodiesel case as a consequence of lower post-injected fuel energy and thus lower exhaust temperature. In the self-regenerating mode, the DPF was charged more slowly with biodiesel than with diesel fuel and its break even temperature was 40 °C lower with biodiesel fuel. These results provide further evidence that biodiesel soot is more reactive to oxidation. Although thermogravimetric results confirmed this tendency based on the differences on the pre-exponential factor, Raman spectra showed that biodiesel soot reached more ordered graphite-like structures and lower amorphous carbon concentration and XRD analysis showed that biodiesel soot displayed a higher degree of graphitization. The TEM analysis of the agglomerates showed that soot primary particles obtained with biodiesel fuel were significantly smaller and had higher specific active surface than those of diesel soot. From these results, an interpretation of the differences in soot oxidation between both soot samples was made based on the different length scales, from the carbon fringes to the particulate filter.     

Oxidation stability of biodiesel derived from high free fatty acid feedstock

At present, with fluctuating feedstock prices, the biodiesel manufacturing industries are facing some downfall. High free fatty acid (FFA) non-edible oil, which is a byproduct of vegetable oil refineries, is available at low price and in considerable quantities at vegetable oil refinery sites. This high FFA oil can be utilized as a potential low cost feedstock for biodiesel production. In the present work, high FFA (51.6%) oil was synthesized into biodiesel by a two-step process. Except oxidation stability, other fuel properties of the produced biodiesel were found to be comparable with that of biodiesel specifications. Oxidation stability was found to be only 2.1 h at 110°C as determined by the Rancimat apparatus.

In order to study and further improve the oxidation stability, the biodiesel (B100) was dosed with a suitable antioxidant (pyrogallol) and stored for 6 months. The acid value, peroxide value, and kinematic viscosity which are closely associated with oxidation behavior were studied. It was found that biodiesel dosed with an antioxidant showed the least increase in the acid value, peroxide value, and kinematic viscosity. Also, induction period was improved and found to be within the American Society for Testing and Materials limit . Thus, the high FFA oil-based biodiesel with a suitable antioxidant can be used as a potential feedstock to resolve the issue of the high cost of biodiesel production.     

The effect of biodiesel oxidation on engine performance and emissions

Biodiesel is an alternative fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Previous research has shown that biodiesel-fueled engines produce less carbon monoxide, unburned hydrocarbons, and particulate emissions compared to diesel fuel. One drawback of biodiesel is that it is more prone to oxidation than petroleum-based diesel fuel. In its advanced stages, this oxidation can cause the fuel to become acidic and to form insoluble gums and sediments that can plug fuel filters. The objective of this study was to evaluate the impact of oxidized biodiesel on engine performance and emissions. A John Deere 4276T turbocharged DI diesel engine was fueled with oxidized and unoxidized biodiesel and the performance and emissions were compared with No. 2 diesel fuel. The neat biodiesels, 20% blends, and the base fuel (No. 2 diesel) were tested at two different loads (100 and 20%) and three injection timings (3° advanced, standard; 3° retarded). The tests were performed at steady-state conditions at a single engine speed of 1400 rpm. The engine performance of the neat biodiesels and their blends was similar to that of No. 2 diesel fuel with the same thermal efficiency, but higher fuel consumption. Compared with unoxidized biodiesel, oxidized neat biodiesel produced 15 and 16% lower exhaust carbon monoxide and hydrocarbons, respectively. No statistically significant difference was found between the oxides of nitrogen and smoke emissions from oxidized and unoxidized biodiesel.     

Examination of the oxidation behavior of biodiesel soot

In this work, we expand upon past work relating the nanostructure and oxidative reactivity of soot. This work shows that the initial structure alone does not dictate the reactivity of diesel soot and rather the initial oxygen groups have a strong influence on the oxidation rate. A comparison of the complete oxidation behavior and burning mode was made to address the mechanism by which biodiesel soot enhances oxidation. Diesel soot derived from neat biodiesel (B100) is far more reactive during oxidation than soot from neat Fischer-Tropsch diesel fuel (FT100). B100 soot undergoes a unique oxidation process leading to capsule-type oxidation and eventual formation of graphene ribbon structures. The results presented here demonstrate the importance of initial properties of the soot, which lead to differences in burning mode. Incorporation of greater surface oxygen functionality in the B100 soot provides the means for more rapid oxidation and drastic structural transformation during the oxidation process.     

Improving the low-temperature properties of biodiesel: Methods and consequences

Biodiesel is widely accepted as an additive for fossil derived diesel in compression ignition engines. It offers many advantages including: higher cetane number; reduced emissions of particulates, NO_x, SO_x, CO, and hydrocarbons; reduced toxicity; improved safety; and lower lifecycle CO₂ emissions. A characteristic of biodiesel limiting its application is its relatively poor low-temperature flow properties, which are primarily a consequence of the fatty acid make-up of the oil feedstock. Attempts to influence the fatty acid profile of either the oil feedstock or the biodiesel product include winterisation and fractionation which reduce the fraction of saturated fatty acids and result in large reductions in yield. A reduction in saturated fatty acids reduces ignition quality of the fuel, while an increase in unsaturation reduces oxidation stability. Additives designed for petroleum diesel have been used with limited success and specific additives for biodiesel remain in their infancy. The addition of branched moieties either to the alkyl head-group of the ester or as a side-chain to the tail-group can reduce the cloud point. Specifically, the removal of the double bonds on the ester group and the addition of a side-chain may provide a benefit in terms of low-temperature properties and offer improved oxidation stability. However, a negative impact on ignition quality and viscosity may result.     

Impact of Carbon Nanotubes and Di-Ethyl Ether as additives with biodiesel emulsion fuels in a diesel engine – An experimental investigation

In the current global energy scenario, fossil fuels face challenges with regards to exorbitant demand, environmental hazards and escalating costs. In this regard, the technical community is in quest for alternative resources. In this context, biodiesel fuel is potentially considered as alternative fuels for compression ignition engines. Hence, in this current investigation, biodiesel and biodiesel emulsions are prepared from a vegetable oil and further subjected for the blending with potential additives such as CNT (Carbon Nanotubes) and DEE (Di-Ethyl Ether) to improve the working attributes of the diesel engine. The entire investigation was carried out in five stages. In the first stage, both pure diesel and biodiesel (derived from jatropha oil) fuels were tested in the diesel engine to obtain baseline readings. In the second stage, water–biodiesel emulsion fuel was prepared in the proportion of 91% of biodiesel, 5% of water and 4% of emulsifiers (by volume). In the third stage, 50 ppm of CNT, 50 ml of DEE and combined mixture of CNT+DEE (50 ppm CNT+50 ml DEE) were mixed with the water–biodiesel emulsion fuel separately to prepare the CNT and DEE blended water–biodiesel emulsion fuels respectively. In fourth stage, the prepared emulsion fuels were subjected to stability investigations. In the fifth stage, all the prepared stable emulsion fuels were subjected for experimental testing in a diesel engine. It was observed that the CNT and DEE blended biodiesel emulsion fuels reflected better performance, emission and combustion attributes than that of pure diesel and biodiesel. At the full load, the brake thermal efficiency, NO and smoke emission of CNT+DEE fuels was 28.8%, 895 ppm and 36%, whereas it was 25.2%, 1340 ppm and 71% for pure diesel respectively. It was also observed that on adding CNT and DEE with the biodiesel emulsion fuels, the ignition delay was shortened and henceforth, the additive blended biodiesel emulsion fuels exhibited higher brake thermal efficiency and reduced emissions (NO, smoke) than that of pure diesel and biodiesel.     

Effect of diethyl ether additive in Jatropha biodiesel-diesel fuel blends on the variable compression ratio diesel engine performance and emissions characteristics at different loads and compression ratios

An investigational analysis was performed to assess the effect of diethyl ether (DEE) that acts as an oxygenated additive in Jatropha biodiesel and diesel fuel blends on the performance enhancement and emission reduction of a variable compression ratio (CR) diesel engine. The DEE (10% vol) is added to different concentration levels of Jatropha biodiesel (B5, B10, and B20). The Jatropha biodiesel (JME) is prepared by the transesterification reaction and DEE is prepared through acid distillation of ethanol. The various tests were conducted by varying the loads at 25%, 50%, 75%, and 100% (3, 6, 9, and 12 kg). The DEE was entirely miscible with diesel and Jatropha biodiesel, the addition of DEE increases the cetane and calorific value, kinematic viscosity of the fuel blends compared with neat diesel or Jatropha biodiesel. The results illustrate that at higher loads and CRs, the engine performance parameters such as brake thermal efficiency enhances and reduces the brake-specific fuel consumption for DEE-Jatropha biodiesel-diesel fuel blends. Blend A3 (10% DEE + 20% JME + 70% diesel) demonstrated an overall improvement in the engine performance parameters and emission characteristics compared with A1, A2, and diesel fuel blends. It is concluded that the DEE-JME-diesel fuel blend is a promising source of fuel for diesel engine at maximum load.     

Exhaust emission study on neat biodiesel and alcohol blends fueled diesel engine

In this study, neat biodiesel with octanol additive was employed in a diesel engine and its effects on engine emission were studied. The five fuels evaluated were neat palm kernal oil biodiesel, octanol blended with biodiesel by 10%, 20%, and 30% volume, and diesel. All the emissions are reduced by the addition of octanol in biodiesel in all loads owing to the higher oxygen concentration of air/fuel mixtures and improved atomization. Hence, it is concluded that the neat biodiesel and octanol blends can be employed as an alternative fuel for existing unmodified diesel engines owing to its lesser emission characteristics.     

Biodiesel improves lubricity of new low sulphur diesel fuels

In this work, biodiesel from waste vegetable oil was used as an additive in low sulphur diesel fuel in automobile engines. The result was a fuel mixture with high lubricating power. According to the lubrication trials, the experimental mixtures complied with lubricity conditions established by European regulations, even when only a small quantity of biodiesel was used. It was also found that the mixtures were compatible with different engine gaskets and engine lubricant. Lastly, bench tests were performed using an automobile engine with mixtures of diesel fuel without conventional lubricant additive and biodiesel. The results showed that engine performance curves were very similar to those obtained with diesel fuel and that contaminating emissions from the engine decreased substantially by including biodiesel in the fuel, except for nitrogen oxides.     

Review of different test methods for the evaluation of stability of biodiesel

The vegetable oil, fats and their biodiesel suffer with the drawback of deterioration of its quality when it is in contact with oxygen unlike petroleum diesel. There are various types of stabilities like oxidation, storage and thermal, playing key roles in making the fuel unstable. The present paper is an attempt to review all type of stability measuring test methods to find out the best method for stability measurement. From the review it is found that there are several methods to measure the stability of biodiesel but two test methods emerges the most likely choice for the purpose of measurement of oxidation stability of biodiesel. These are ASTM 2274 and 743 Rancimat test. A comparison between these two shows that these may be used alternatively. Most commonly used methods to investigate the thermal stability are Rancimat test, ASTM D 6408-08, D 5304-06 and TGA/DTA. Rancimat test has been suggested as an important method to measure the thermal stability of oils, fats and biodiesel fuels.     

Emission analysis of Botryococcus braunii algal biofuel using Ni-Doped ZnO nano additives for IC engines

Microalgae biodiesel has been considered ?as a clean renewable fuel for diesel marine engines. This is due to its optimistic characterizations such as ?rapid growth rate, high productivity, and its ability to convert CO₂ into fuel. In this study, the use of microalgae biodiesel, obtained from Botryococcus braunii, as an alternative fuel for diesel marine engines has been investigated. The diesel engine is verified experimentally using Ni-Doped ZnO nano additive blends with algae biodiesel and neat diesel fuel. The results showed that doped nano additive blends? produce less emission compared to B20.     

Biodiesel production from waste chicken fat based sources and evaluation with Mg based additive in a diesel engine

In this study, chicken fat biodiesel with synthetic Mg additive was studied in a single-cylinder, direct injection (DI) diesel engine and its effects on engine performance and exhaust emissions were studied. A two-step catalytic process was chosen for the synthesis of the biodiesel. Methanol, sulphuric acid and sodium hydroxide catalyst were used in the reaction. To determine their effects on viscosity and flash point of the biodiesel, reaction temperature, methanol ratio, type and amount of catalyst were varied as independent parameters. Organic based synthetic magnesium additive was doped into the biodiesel blend by 12 μmol Mg. Engine tests were run with diesel fuel (EN 590) and a blend of 10% chicken fat biodiesel and diesel fuel (B10) at full load operating conditions and different engine speeds from 1800 to 3000 rpm. The results showed that, the engine torque was not changed significantly with the addition of 10% chicken fat biodiesel, while the specific fuel consumption increased by 5.2% due to the lower heating value of biodiesel. In-cylinder peak pressure slightly rose and the start of combustion was earlier. CO and smoke emissions decreased by 13% and 9% respectively, but NO_x emission increased by 5%.