Biodiesel synthesized from waste cooking oil in a continuous microwave assisted reactor reduced PM and NOx emissions

Synthesis, catalysts and enhancement technologies of biodiesel from oil feedstock - A review

Biodiesel is considered as one of the most promising alternative fuels due to the depletion of fossil fuels and the need to cope with potential energy shortages in the future. This article provides a thorough analysis of biodiesel synthesis, covering a variety of topics including oil feedstock, synthesis methods, catalysts, and enhancement technologies. Different oil feedstock for the synthesis of biodiesel is compared in the review, including edible plant oil, non-edible plant oil, waste cooking oil, animal fat, microbial oil, and algae oil. In addition, different methods for the synthesis of biodiesel are discussed, including direct use, blending, thermal cracking, microemulsions, and transesterification processes, highlighting their respective advantages and disadvantages. Among them, the transesterification method is the most commonly used and a thorough examination is given of the benefits and drawbacks of utilizing enzymatic, heterogeneous, and homogeneous catalysts in this process. Moreover, this article provides an overview of emerging intensification technologies, such as ultrasonic and microwave-assisted, electrolysis, reactive distillation, and microreactors. The benefits and limitations of these emerging technologies are also reviewed. The contribution of this article is offering a thorough and detailed review of biodiesel production technologies, focusing mainly on recent advances in enhanced chemical reaction processes. This provides a resource for researchers to assess and compare the latest advancements in their investigations. It also opens up the potential for enhancing the value of oil feedstocks efficiently, contributing to the development of new energy sources.

The effect of biodiesel production method on its combustion behavior in an agricultural tractor engine

In this study, biodiesel fuel was produced from waste cooking oil (WCO) using a heterogeneous catalyst under microwave (MB) and conventional (CB) heating, and fueled in an agricultural tractor engine to evaluate the engine performance as well as emissions. The biodiesels presented different fatty acid methyl ester (FAME) profiles where MB had lower unsaturated FAME chains. Beyond the transesterification reaction time, the energy consumed for MB biodiesel production diminished by around eight times compared to that required for CB production. The engine results confirmed the positive influence of blending net diesel fuel with biodiesel for enhancing the engine performance and reducing the emissions. More than 20% increment in the engine power and torque was detected at all engine loads (the engine speed was adjusted at 1500 rpm). The hydrocarbon (HC), carbon monoxide (CO), and smoke opacity (SO) indicated significant reductions compared to when net diesel fuel was used. According to statistical analysis, CB25 and MB25 fuels presented a suitable combination as fuel where MB25 provided better engine performance, lower HC and SO emissions, with CO emissions reaching the minimum amount by CB fuels.

Emission analysis and optimization of antioxidant influence on biofuel stability

Taking the unbalanced properties of biodiesel leading to rapid oxidation as the maxim of this research, with the aid of weightage evaluation and optimization techniques like Criteria Importance Through Intercriteria Correlation and Evaluation based on Distance from Average Solution (EDAS), Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) respectively, the ranking of each sample with elevated stability parameters has been projected through rancimat test for oxidation, kinematic viscosity and acid value test for storage, and thermo gravimetric analyzer test for thermal stability parameters. To make sure that the obtained parameter consequences are truthful, Fourier Transform Infrared Spectroscopy has been used as the correlating tool in this research. Twenty percent of the biodiesel with Tert butyl hydroquinone (T) at 1000 ppm (3) is mixed to diesel and emission characteristics like carbon monoxide, carbon dioxide, hydrocarbon, smoke opacity, and nitrous of oxide have been analyzed for diesel, B20 = 20% biodiesel + 80% diesel, and B20T3. Among every five sets of concentration and antioxidant (T and Pyrogallol-PY) dosed samples, an average of 9.93% elevated oxidation stability, 1.19%, and 4.51% lower kinematic viscosity and acid value, and 25.35% higher thermal stability have been obtained for B100T3 = Pure biodiesel + T3. An elevated appraisal score and performance score of 1.000 and 0.998 by EDAS and TOPSIS respectively for B100T3 blend has also been obtained. Except for carbon dioxide and nitrous of oxide, other emission levels in B20 and B20T3 samples decrease when compared to diesel. While comparing B20 and B20T3 poisonous nitrous of oxide emission levels, the B20T3 sample shows an average decrease of 9.37% when compared to B20 sample due to the suppressing action of antioxidants.

Dissociation characteristics and anthropogenic emissions from the combustion of double gas hydrates

Gas hydrates are an alternative and environmentally friendly energy source increasingly in the focus of scientific attention. The physicochemical processes behind gas hydrate combustion are studied experimentally and numerically with a view to improving the combustion efficiency and reducing gas emissions. It is important to estimate the pollutant emission concentrations in the context of combustion conditions. The research deals with the dissociation and combustion behavior of double gas hydrates in a tubular muffle furnace. Gas hydrates of different composition are considered: methane, methane-ethane, methane-propane and methane-isopropanol. Double gas hydrates are characterized by more stable combustion compared to methane hydrate. It is also shown that the double gas hydrate dissociation rate increases by 15-30% with increasing temperature. Dissociation and combustion processes were also modeled as part of the research, accounting for phase transitions in a gas hydrate layer. According to the simulation results, the total dissociation rate of gas hydrate increases by 3 times with an about 2.5-times increase in the powder layer thickness. Our experiments also focused on the impact of furnace temperature and gas hydrate composition on concentrations of anthropogenic gas emissions. We have found that the presence of heavy hydrocarbons such as ethane, propane and isopropanol in double gas hydrates reduce unburned CH₄ emissions by 60%. Also, an increase in the combustion efficiency of double gas hydrates, accompanied by a decrease in the concentrations of unburned CH₄ and CO, affects the yield of CO₂, which increased by 13-35%. When we increased the temperature in the furnace from 750 °C to 1050 °C, concentrations of nitrogen oxides and carbon dioxide increased by up to five times. Thus, the resulting correlations between the key parameters of these processes and a set of the main inputs illustrate the possibility to predict the optimal conditions for the combustion of gas hydrates.

Effects of Cu doping on electrochemical NOx removal by La0.8Sr0.2MnO3 perovskites

Electrochemical removal of nitrogen oxides (NO_x) by perovskite electrodes is a promising method due to its low cost, simple operation and no secondary pollution. In this study, a series of La_0.8Sr_0.2Mn_1-xCu_xO₃ (x = 0, 0.05, 0.1 and 0.15) perovskites are fabricated as the improved electrodes of solid electrolyte cells (SECs) for NO_x removal and the effects of Cu doping are investigated systematacially. Multiple characterization methods are carried out to analyze the physicochemical properties of perovskites firstly. Then the performances of cells based on various perovskites are evaluated by the measurements of electrochemical properties and NO_x conversions. The results show that the Cu-doped electrode has more surface oxygen vacancies and a better redox property, thus having a higher NO_x conversion and smaller polarization resistance. The electrode based on La_0.8Sr_0.2Mn_0.9Cu_0.1O₃ has the maximum 70.8% NO_x conversion and the lowest 36.3 Ω cm² R_p value in the atmosphere of 1000 ppm NO at 700 °C. First-principle calculation reveals that the Cu-doped electrode is easier to form surface oxygen vacancy, while the surface oxygen vacancy plays an important role on electron transfer between electrode and NO_x molecule. This study not only provides a new strategy to enhance the electrode performance for NO_x removal in SECs but reveals the fundamental effect of Cu doping on the properties of La_0.8Sr_0.2MnO₃ perovskites.

Insight into Nanoparticle-Number-Derived Characteristics of Precharged Biodiesel Exhaust Gas in Nonthermal Plasma State

The utilization of biodiesel as an alternative partial replacement of diesel fuel was shown to improve exhaust emissions from diesel engines. Waste cooking oil biodiesel (WCO) has also gained more attention due to edible biofuel supply and the environment. In this study, a nonthermal plasma (NTP) technique was applied to be equipped into the after-treatment system of a four-cylinder diesel engine at medium- and high-load conditions. The exhaust gases in the NTP state from the combustion of WCO and diesel (D100) fuels were partially drawn by spectrometers and nanoparticle-number-derived characteristics were analyzed. The particle number, area, and mass concentrations were in log-normal distribution over equivalent diameters, and they were higher at high load. The concentration of the particulate matter (PM) was lower but was larger in size when the NTP charger was activated due to coagulation principally owing to WCO's number and surface area. The total particle masses were lower for WCO at the two load conditions tested. During NTP charger activation, the mass mean diameters were increased by maximum values of 24.0% for D100 and 5.5% for WCO. The PM removal efficiencies were maximized by 10.8% for D100 and 16.7% for WCO when the NTP charger was in use, and the WCO exhaust was dominantly seen to simultaneously reduce NO _x and PM emissions.

Microwave assisted carbonization and activation of biochar for energy-environment nexus: A review

Conventional thermochemical conversion techniques for biofuel production from lignocellulosic biomass is often non-selective and energy inefficient. Microwave assisted pyrolysis (MAP) is cost and energy-efficient technology aimed for value-added bioproducts recovery from biomass with less environmental impacts. The present review emphasizes the performance of MAP in terms of product yield, characteristics and energy consumption and further it compares it with conventional pyrolysis. The significant role of biochar as catalyst in microwave pyrolysis for enhancing the product selectivity and quality, and the influence of microwave activation on product composition identified through sophisticated techniques has been highlighted. Besides, the application of MAP based biochar as soil conditioner and heavy metal immobilization has been illustrated. MAP accomplished at low temperature creates uniform thermal gradient than conventional mode, thereby producing engineered char with hotspots that could be used as catalysts for gasification, energy storage, etc. The stability, nutrient content, surface properties and adsorption capacity of biochar was enhanced by microwave activation, thus facilitating its use as soil conditioner. Many reviews until now on MAP mostly dealt with operational conditions and product yield with limited focus on comparative energy consumption with conventional mode, analytical techniques for product characterization and end application especially concerning agriculture. Thus, the present review adds on to the current state of art on microwave assisted pyrolysis covering all-round aspects of production followed by characterization and applications as soil amendment for increasing crop productivity in addition to the production of value-added chemicals, thus promoting process sustainability in energy and environment nexus.

Technical Aspects of Biofuel Production from Different Sources in Malaysia—A Review

Due to the depletion of fossil fuels, biofuel production from renewable sources has gained interest. Malaysia, as a tropical country with huge resources, has a high potential to produce different types of biofuels from renewable sources. In Malaysia, biofuels can be produced from various sources, such as lignocellulosic biomass, palm oil residues, and municipal wastes. Besides, biofuels are divided into two main categories, called liquid (bioethanol and biodiesel) and gaseous (biohydrogen and biogas). Malaysia agreed to reduce its greenhouse gas (GHG) emissions by 45% by 2030 as they signed the Paris agreement in 2016. Therefore, we reviewed the status and potential of Malaysia as one of the main biofuel producers in the world in recent years. The role of government and existing policies have been discussed to analyze the outlook of the biofuel industries in Malaysia.

Synthesis of renewable heterogeneous acid catalyst from oil palm empty fruit bunch for glycerol-free biodiesel production

Interest in biodiesel research has escalated over the years due to dwindling fossil fuel reserves. The implementation of a carbon-based solid acid catalyst in biodiesel production eradicates the separation problems associated with homogeneous catalysis. However, its application in the glycerol-free interesterification process for biodiesel production is still rarely being studied in the literature. In this study, novel environmentally benign catalysts were prepared from oil palm empty fruit bunch (OPEFB) derived activated carbon (AC) which is sustainable and low cost via direct sulfonation using concentrated sulfuric acid. The effects of synthesizing variables such as carbonization and sulfonation temperatures with different holding times towards the fatty acid methyl ester (FAME) yield in interesterification reaction with oleic acid and methyl acetate were investigated in detail. It was found that the optimum carbonization temperature and duration together with sulfonation temperature and duration were 600 °C, 3 h, 100 °C and 6 h, respectively. The catalyst possessed an amorphous structure with a high total acid density of 9.0 mmol NaOH g^-1 due to the well-developed porous framework structure of the carbon support. Under these optimum conditions, the OPEFB derived solid acid catalyst recorded an excellent catalytic activity of 50.5% methyl oleate yield at 100 °C after 8 h with 50:1 methyl acetate to oleic acid molar ratio and 10 wt% catalyst dosage. The heterogeneous acid catalyst derived from OPEFB had shown promising properties that made them highly suitable for cost-effective and environmental-friendly glycerol-free biodiesel production.