A.M. Ruhul

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.

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.

Production, characterization, engine performance and emission characteristics of Croton megalocarpus and Ceiba pentandra complementary blends in a single-cylinder diesel engine

Compounding energy demand and environmental issues necessitate suitable alternative or partial replacement of fossil fuels. Among the possible sources, biodiesel from non-edible vegetable oil sources is more economically feasible and possesses characteristics close to those of petroleum diesel. Two potential non-edible biodiesel feedstocks “Croton megalocarpus” and “Ceiba pentandra” were used for biodiesel production through esterification and transesterification process on a laboratory scale. Biodiesel characterization, engine performance and emission characteristics were investigated in an unmodified direct injection, naturally aspirated, single-cylinder diesel engine. 20% (v/v) of each of C. megalocarpus (CM), C. pentandra (CP) and their combined blends (CMB20, CPB20, CMB15CPB05, CMB10CPB10, and CMB05CPB15) were tested under varying engine speeds ranging from 1000 rpm to 2400 rpm at full load conditions. CMB20 and CPB20 reduced the brake power (BP) by 2.63% and 3.70%, brake thermal efficiency (BTE) by 5.97% and 3.72%, carbon monoxide (CO) emission by 1.09% and 2.39%, hydrocarbon (HC) emission by 1.48% and 4.62% and smoke emission by 12.35% and 17.13%, respectively compared to petroleum diesel. On the other hand, CMB20 and CPB20 increased the brake specific fuel consumption (BSFC) by 9.74% and 7.63%, NOX emission by 13.19% and 15.45%, respectively. A mixture of 10% of both biodiesels with diesels (CMB10CPB10) provides better performance and emission characteristics. CMB10CPB10 reduced BP, BTE, CO, HC and smoke by 0.53%, 0.50%, 5.21%, 8.38% and 20.71%, respectively and increased BSFC and NOX by 3.90% and 18.66%, respectively compared to conventional diesel. A combined blend of CM and CP could be a sustainable substitute for fossil diesel in the context of performance and emission.

Analysis of thermal stability and lubrication characteristics of Millettia pinnata oil

Lubricants are mostly used to reduce the friction and wear between sliding and metal contact surfaces, allowing them to move smoothly over each other. Nowadays, due to the increase in oil prices and reduction of oil reserves, it is necessary to replace mineral oil, which will also protect the environment from hazards caused by these oils. It is essential to find an alternative oil for the replacement of mineral-oil-based lubricants, and vegetable oil already meets the necessary requirements. Vegetable-oil-based biolubricants are non-toxic, biodegradable, renewable and have a good lubricating performance compared to mineral-oil-based lubricants. This study analyzes the thermal stability and lubricating characteristics of different types of vegetable oil. The friction and wear characteristics of the oils were investigated using a four-ball tester, according to ASTM method 4172. Millettia pinnata oil has good oxidation stability due to the presence of higher percentages of oleic acid in its fatty acid composition. Millettia pinnata oil also shows a higher kinematic viscosity. Rice bran oil shows a higher viscosity index than other oils, and it is better for boundary lubrication. In thermogravimetric analysis, it was found that Millettia pinnata oil remains thermally stable at 391 °C. Millettia pinnata oil showed a lower coefficient of friction and rice bran oil showed a lower wear scar diameter compared to other vegetable oils and lube oils. A lower wear scar surface area was found with rice bran oil compared to other vegetable and commercial oils. Therefore, due to a better lubricating performance, Millettia pinnata oil has great potential to be used as a lubricating oil in industrial and automotive applications.

Evaluation of the characteristics of non-oxidative biodiesels: a FAME composition, thermogravimetric and IR analysis

This experiment evaluates the effects of non-oxidative biodiesel (low oxygen content biodiesels) characteristics and their engine performances. Biodiesels produced from different feedstocks typically contains 10% to 15% oxygen by weight, which enhances the combustion quality and reduces the emissions of hydrocarbons (HCs) and carbon monoxide (CO). However, it produces a higher amount of nitrogen oxides (NOx) due to an increasing number of combustion products, resulting in a higher cylinder temperature. In addition, lean air–fuel mixtures can contribute to higher NOx emissions because biodiesel is more oxygenated than diesel. In this study, biodiesels produced from different feedstocks by a transesterification process were used to reduce the oxygen content by dipping an iron bar in the biodiesels, which absorbs oxygen and gets oxidized. Then, the oil characteristics, such as the percentage of saturated and unsaturated fatty acids, thermal degradation, stability and existing functional groups, were analyzed using fatty acid methyl ester (FAME) composition analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy analysis of neat biodiesel and non-oxidative biodiesel. Herein, Pongamia and Moringa biodiesels, containing normal and reduced weight percentages of oxygen, were evaluated to improve the quality and stability of biodiesels used in the diesel engine, which will also reduce the NOx emissions. Non-oxidative biodiesels had some positive effect on their properties, which can further reduce the NOx emissions. Herein, non-oxidative Pongamia and Moringa had quite similar characteristics and the former was observed to perform better in the reduction of NOx and other emissions as well.