M.M. Rashed

State of the art of biodiesel production processes: a review of the heterogeneous catalyst

A broadened focus on energy, the fast growing value of petroleum oil, harmful atmospheric emissions because of the evolution of greenhouse gases, natural contamination, and quick reduction approaches to obtain fossil fuels are critical factors in the search for alternative energy sources. The need for developing renewable energy sources with fewer environmental effects is increasing because of the problems caused by the extensive use of fossil fuels. Currently, creating energy from low-carbon origins and introducing eco-friendly modern technology are the main targets of researchers in the field. Biodiesel has been identified as an alternative renewable liquid fuel source that can be derived through thermal cracking, esterification and transesterification of different triglycerides. Among these processes, the most popular and convenient technique for biodiesel production is the transesterification of triglyceride with the help of a suitable alcohol and a catalyst. Many scientists have introduced different types of catalysts to optimize the reaction conditions and the biodiesel production yields. Catalyst selection involves the determination of the water content and the free fatty acids in the oil. Homogeneous base catalysts provide faster reaction rates than homogeneous acid catalysts. Recently researchers have paid attention to heterogeneous catalysts because of their high activity, high selectivity, catalyst recovery, reusability, easy separation from the products, and water tolerance properties. Biocatalysts present significant advantages in terms of environmental issues over conventional alkali-catalyzed processes. This review article focuses on various technologies used for biodiesel production, as well as the benefits and limitations of the different types of catalysts in the relevant production technologies. We also conduct a comparative study of biocatalysts and homogeneous and heterogeneous catalysts in biodiesel production technologies at the laboratory scale, as well as their industrial applications.

A comprehensive review on the assessment of fuel additive effects on combustion behavior in CI engine fuelled with diesel biodiesel blends

Development in transport technology is a major issue owing to the increase the number of vehicles, which in turn increases emissions, which result in global warming. The world’s present transportation systems are greatly dependent on petroleum which will deplete rapidly due to limited reserves of fossil fuel. In addition, transportation is responsible for more than 25 percent of the world’s greenhouse gas (GHG) emissions, and this share is rising, which is a threat for future. As an alternative, biodiesel has drawn attention due to its renewability, biodegradability, high conductivity, low sulfur content, flash point, low aromatic content, increased lubricity etc. with less carbon monoxide and carbon dioxide emission. On the other hand, as the viscosity of biodiesel is greater than diesel due to its higher molecular mass and chemical structure, problems such as pumping, combustion, atomization in the injector system, injector deposit, plugging of filters, carbon deposits on piston and head of engine occur. Most previous studies concluded that although particulate emissions from biodiesel fuelled engines are much less than in gasoline, NOx emissions increases significantly. The adjustment of ignition delay in the premixed combustion phase, faster rate of fuel burn, advanced start of combustion, low radiation heat transfer and variable adiabatic flame temperature is mainly responsible for NOx formation and other emissions. Hence fuel additives may play an important role to counteract such problems and achieve various specified standards. Researchers have used many additives to improve the quality of biodiesel such as metal-based additives, oxygenated additives, cetane improvers, ignition promoters, cold-flow improvers, antioxidants and lubricity improvers etc. This literature review characterizes the combustion behavior of diesel engines fuelled by diesel, biodiesel and its blends including additives. It was found that combustion characteristics were improved by introducing additives into diesel and biodiesel blends, while exhaust emissions are also reduced.

Stability of biodiesel, its improvement and the effect of antioxidant treated blends on engine performance and emission

Biodiesel consists of long chain fatty acid esters derived from vegetable oils, animal fats, and used oils. Biodiesel contains different types, amounts, and configurations of unsaturated fatty acids, which are prone to oxidation. Biodiesel stability is affected by its interaction with atmospheric oxygen, light and temperature, storage conditions, and factors causing sediment formation. It can be classified broadly into three types: oxidation stability, thermal stability, and storage stability. Oxidative degradation occurs in biodiesel upon aerobic contact during storage, as well as upon contact with metal contaminants. Thermal instability focuses on the oxidation rate at higher temperatures, which is characterized by the formation of insolubles and increase in the weight of oil and fat. Storage stability is concerned with interaction between the physical and chemical characteristics of biodiesel with environmental factors, such as light, metal contamination, color changes, and sediment formation. Antioxidant concentration greatly influences engine performance and emission. The BSFC of biodiesel fuel with antioxidants is less than that of fuel without antioxidants. Moreover, an antioxidant can significantly reduce NOx formation during engine operation. Among the available synthetic antioxidants, only three antioxidants (TBHQ, PY, and PG) can significantly increase biodiesel stability. This article presents an overview of the stability of biodiesel, including the methods available for the prediction of its different stability properties. Feasible remedies to improve the stability of biodiesel and the effect of antioxidants in stabilized blends on engine performance and emission are also discussed.

A comprehensive review on biodiesel cold flow properties and oxidation stability along with their improvement processes

Biodiesel, which comprises fatty acid esters, is derived from different sources, such as vegetable oils from palm, sunflower, soybean, canola, Jatropha, and cottonseed sources, animal fats, and waste cooking oil. Biodiesel is considered as an alternative fuel for diesel engines. However, biodiesel has poor cold flow behavior (i.e., high cloud point & pour point) and oxidation stability compared with petroleum diesel because of the presence of saturated and unsaturated fatty acid esters. Consequently, the performance of biodiesel during cold weather is affected. When biodiesel is oxidized, the subsequent dregs can adversely affect the performance of the fuel system as well as clog the fuel filter, fuel lines, and injector. This phenomenon results in start-up and operability problems. Cold flow behavior is usually assessed through the pour point (PP), cloud point (CP), and cold filter plugging point (CFPP). Earlier studies on cold flow focused on reducing the devastating effect of poor cold flow problems, such as lowering the PP, CP, and CFPP of biodiesel. This present paper provides an overview of the cold flow behavior and oxidation stability of biodiesel, as well as their effect on the engine operation system. The improvements on the behavior of cold flow of biodiesel are also discussed.

A comprehensive study on the improvement of oxidation stability and NOx emission levels by antioxidant addition to biodiesel blends in a light-duty diesel engine

Moringa oleifera oil, a non-edible biodiesel feedstock with high unsaturated fatty acid content, was used in this study. MB20 (20% Moringa oil methyl ester and 80% diesel fuel blend) was mixed with three antioxidants, namely, N,N′-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-1,4-phenylenediamine (NPPD) and 2-ethylhexyl nitrate (EHN), at a concentration of 1000 ppm. The effects of these antioxidants on the oxidation stability of biodiesel as well as on the exhaust emission and performance of a single-cylinder diesel engine were analysed. After the Rancimat test, oxidation stability was enhanced by the antioxidants in the order of DPPD > NPPD > EHN. Results also showed that DPPD-, NPPD- and EHN-treated blends reduced NOx emissions within 5.9–8.80% compared with those in the untreated blend because of suppressed free radical formation. Antioxidant-treated blends contained high amounts of carbon monoxide and hydrocarbon and showed improved smoke opacity, thereby indicating that emissions were below the diesel fuel emission levels. Results demonstrated that antioxidant addition to MB20 improves engine performance characteristics. This study shows that MB20 blends with antioxidants can be used in diesel engines without any modification.

Experimental assessment of non-edible candlenut biodiesel and its blend characteristics as diesel engine fuel

Exploring new renewable energy sources as a substitute of petroleum reserves is necessary due to fulfilling the oncoming energy needs for industry and transportation systems. In this quest, a lot of research is going on to expose different kinds of new biodiesel sources. The non-edible oil from candlenut possesses the potential as a feedstock for biodiesel production. The present study aims to produce biodiesel from crude candlenut oil by using two-step transesterification process, and 10%, 20%, and 30% of biodiesel were mixed with diesel fuel as test blends for engine testing. Fourier transform infrared (FTIR) and gas chromatography (GC) were performed and analyzed to characterize the biodiesel. Also, the fuel properties of biodiesel and its blends were measured and compared with the specified standards. The thermal stability of the fuel blends was measured by thermogravimetric analysis (TGA) and differential scan calorimetry (DSC) analysis. Engine characteristics were measured in a Yanmar TF120M single cylinder direct injection (DI) diesel engine. Biodiesel produced from candlenut oil contained 15% free fatty acid (FFA), and two-step esterification and transesterification were used. FTIR and GC remarked the biodiesels’ existing functional groups and fatty acid methyl ester (FAME) composition. The thermal analysis of the biodiesel blends certified about the blends’ stability regarding thermal degradation, melting and crystallization temperature, oxidative temperature, and storage stability. The brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) of the biodiesel blends decreased slightly with an increasing pattern of nitric oxide (NO) emission. However, the hydrocarbon (HC) and carbon monoxides (CO) of biodiesel blends were found decreased.

Performance and emission characteristics of a compression ignition engine running with linseed biodiesel

The energy crisis facing the world today is the result of the continuous depletion of fossil fuels caused by high usage demand. To alleviate the situation, researchers and scientists have been searching for low-cost, eco-friendly, and readily available substitutes to fossil fuel. Biodiesel can be a promising alternative source of energy. This study investigated the parameters of a direct-injection water-cooled diesel engine run with linseed biodiesel blends. These parameters include brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), and emission characteristics. Then, the performance of this engine was compared with that of a diesel fuel-run engine by evaluating the BSFC, BTE, and mechanical efficiency. Results show that the BSFC decreases as the load increases for all fuel blends and increases as the percentage of biodiesel in the blend increases; a 25.6% increase in BSFC is obtained at a low load. The BTE increases with increasing load; at a low load, the highest reduction in BTE is 15.38%. The CO emission reduces by approximately 5.49% at a low load for the B30 blend and 27.7% at a high load for the B20 blend compared with diesel. For pollution investigation, the emissions of NOX, HC, and CO were measured. The CO emission reduces by approximately 5.49% while HC and NOX emissions respectively increase by 15.8% and 19.5% at a low load.

Comparative study of gas-to-liquid fuel, B5 diesel and their blends with respect to fuel properties, engine performance and exhaust emissions

Gas-to-liquid (GTL) fuel is regarded as a promising alternative diesel fuel. It can be used either directly as a diesel fuel or in blends with petroleum-derived diesel or biodiesel. This study investigated the fuel properties, engine performance and exhaust emissions of B5 diesel, GTL fuel and their blends. The main fuel properties of the blended fuels showed a linear variation with the fraction of GTL fuel in the blend. The density and viscosity of the blends decreased with the addition of GTL fuel, but the flash point, cetane number and calorific value increased. The engine performance test results showed an average increase in power of 1.15–5.18%, but a lower brake-specific fuel consumption (1.11–5.58%) for GTL fuel and its blends compared with B5 diesel alone. The emission analysis results showed that the GTL fuel and its blends had a slight reduction in NOx emissions (2.33–11.3%) and a significant reduction in CO (6.92–21.52%), hydrocarbon (8.62–31.76%) and smoke (12.2–48.88%) emissions compared with B5 diesel. These indicate the potential for the application of B5 diesel–GTL blends.

Impact of edible and non-edible biodiesel fuel properties and engine operation condition on the performance and emission characteristics of unmodified DI diesel engine

ABSTRACT The purpose of this work is to test the feasibility of biodiesel as a substitute for diesel used in a direct injection (DI) diesel engine. The biodiesel was produced by an esterification and transesterification process. Experiments were conducted with diesel–biodiesel blends containing 10 and 20% biodiesel with the diesel fuel. The results of the biodiesel blends are compared with baseline diesel which was assessed at constant speed in a single cylinder diesel engine at various loading conditions. The physicochemical properties of palm and Calophyllum inophyllum biodiesel and their blends meet the standard specification ASTM D6751 and EN 14214 standards. The maximum brake thermal efficiency was attained with diesel fuel, 10% palm biodiesel (PB10) and 10% C. inophyllum biodiesel (CI10) at all load condition except low load condition. Engine emission results showed that the 20% C. inophyllum with 80% diesel blend exhibited 6.35% lower amount of brake specific carbon monoxide, and the PB20 blend and CI20 blend reduced brake specific hydrocarbon emission by 7.93 and 9.5%, respectively. NOx emission from palm and C. inophyllum biodiesel blends are found to be 0.29–4.84% higher than diesel fuel. The lowest smoke intensity is found at 27.5% for PB10 and CI10 biodiesel blends compared with diesel fuel.

Performance Evaluation of Rice Bran and Moringa Blended Biodiesel in CI Engine

Biofuels are taken to a notable option for research to energy sources because of their beneficial effect to milieu. In this study, two potential sources namely; Moringa and Rice bran oils are investigated critically as potential sources for biodiesel production. The work was classified into some steps. Firstly, biodiesel production from the two feedstock, secondly, measure the important physicochemical properties of biodiesels, and finally engine test is carried out with biodiesel-diesel blends under constant torque with variable speed. The results show that with the increasing speed, BSFC increases for both biodiesel blends and diesel and biodiesel blends shows only about 2% more BSFC than diesel. Exhaust temperature of biodiesel is about 5-8% higher than diesel but this difference is decreasing with increasing speed. It can be concluded that rice bran and moringa oil would be the feasible option for biodiesel as they satisfy ASTM standard limit and their performance is nearly similar to diesel.