Effect of Metal Oxides (CeO2, ZnO, TiO2, and Al2O3) as the Support for Silver-Supported Catalysts on the Catalytic Oxidation of Diesel Particulate Matter.

This work presented the influence of metal oxides as the support for silver-supported catalysts on the catalytic oxidation of diesel particulate matter (DPM). The supports selected to be used in this work were CeO2 (reducible), ZnO (semiconductor), TiO2 (reducible and semiconductor), and Al2O3 (acidic). The properties of the synthesized catalysts were investigated using XRD, TEM, H2-TPR, and XPS techniques. The DPM oxidation activity was performed using the TGA method. Different states of silver (e.g., Ag° and Ag+) were formed with different concentrations and affected the performance of the DPM oxidation. Ag2O and lattice oxygen, which were mainly generated by Ag/ZnO and Ag/CeO2, were responsible for combusting the VOCs. The metallic silver (Ag°) formed primarily on Ag/Al2O3 and Ag/TiO2 was the main component promoting soot combustion. Contact between the catalyst and DPM had a minor effect on VOC oxidation but significantly affected the soot oxidation activity.

The influence of plastic pyrolysis oil on fuel lubricity and diesel engine performance.

This study investigates the viability of using plastic oils derived from High-density polyethylene (HDPE), Polypropylene (PP), and Polystyrene (PS) as alternative fuels for diesel engines. The research focuses on comparing the physical and chemical properties, fuel lubricity, engine performance, combustion characteristics, and exhaust emissions of these plastic oils. Analysis revealed that PS exhibits different fuel properties compared to diesel, with a carbon range distribution similar to gasoline, while HDPE and PP properties closely resemble diesel fuel. To prevent potential engine damage, PS was excluded from engine tests. PP displayed the best fuel lubricity, attributed to its higher kinematic viscosity and sulphur content, reducing direct friction. Diesel followed, with PS and HDPE in decreasing order of lubricity. Diesel's lubricity was influenced by the 7% palmitic methyl ester content in the fuel. In engine tests, HDPE demonstrated BTE similar to diesel, while PP exhibited lower BTE due to combustion retardation, leading to increased energy losses and higher BSFC. The combustion characteristics, in-cylinder pressure, and heat release rate of HDPE closely resembled diesel, while PP showed significantly delayed combustion due to low oxygen content and higher kinematic viscosity. Notably, NOX emissions from PP were lower than diesel and HDPE at all engine loads due to heat losses, resulting in a low in-cylinder temperature unsuitable for NOX emission. HDPE produced higher NOX emissions than diesel at low and middle loads due to its higher H/C ratio, promoting high thermal NOX formation. HC emissions from both HDPE and PP were higher than diesel due to increased fuel supply, hindering chemical bond breakdown. Similarly, CO emissions increased for HDPE and PP due to insufficient time for complete combustion, with HDPE producing more CO due to its heavy composites and lower cetane index. Smoke emissions from both HDPE and PP surpassed diesel, attributed to lower oxygen and higher sulphur content, leading to increased sulphurate particulate matter formation, and lower fuel density referring to the high amount of fuel supplied to the engine.

Comprehensive analysis of properties of green diesel enhanced by fatty acid methyl esters.

This study systematically investigates the lubricating properties of bio-hydrogenated diesel (BHD), a synthetic diesel produced through biomass hydrogenation of vegetable oil. Despite having similar chemical properties to petroleum diesel, BHD has poor lubricating properties due to the removal of sulfur and oxygenated compounds during the hydrogenation process, which could damage the engine. To address this issue, fatty acid methyl esters (FAME) was added as an additive to BHD to enhance its fuel and lubricating properties. FAME is a polar molecule with good lubricating properties that adsorb on the surface to protect against wear. The study found that adding as little as 5% FAME significantly improved the lubricating properties of BHD. The wear scar diameter (WSD) decreased from 609 µm to 249 µm, and the average film was 94% with an average coefficient of friction of 0.138 by only 5% FAME addition investigated by High Frequency Reciprocating Rig with ISO 12156-1: 2018. This shows that blending FAME with BHD could reduce engine wear and improve its lubricating properties. Disc samples were analyzed using a Scanning Electron Microscope (SEM), OLS5100 3D laser microscopy, and Fourier Transform Infrared Microscopy (FTIR) to examine the worn surface both physically and chemically. An increase in the percentage of FAME addition to BHD resulted in a smoother worn surface, exhibiting reduced delamination and debris compared to pure BHD. This effect was attributed to the protective film formed by FAME. The study highlights the potential of FAME as an additive to enhance the lubricating properties of BHD and reduce engine wear.

Experimental and optimization study on the effects of diethyl ether addition to waste plastic oil on diesel engine characteristics.

This study investigates the impact of adding diethyl ether (DEE) to pyrolysis oil derived from mixed plastic waste on engine performance, combustion characteristics, and emissions. The blending of different DEE concentrations (5%, 10%, and 15% by volume) with waste plastic oil (WPO) was analyzed. Experiments were conducted on a four-cylinder diesel engine, varying engine loads while maintaining engine speed. The results indicate that WPO mainly comprises middle-distillate hydrocarbons (52.58% C13-C18 and 26.15% C19-C23). While WPO had lower specific gravity, density, and flash point, it met diesel fuel specifications for kinematic viscosity and cetane index. The addition of DEE led to decreased properties in all blended fuels, except for the cetane index. Engine performance declined with WPO-DEE blends at low engine loads but improved at high engine loads with minimal variation as DEE concentration increased. DEE addition resulted in a shorter ignition delay and earlier combustion, although increasing DEE concentration did not further advance combustion. NOx emissions significantly decreased with DEE addition, while HC and CO emissions remained unaffected at high engine loads. To optimize the process, the non-dominated sorting genetic algorithm II (NSGA-II) with generalized regression neural networks (GRNNs) was employed as a surrogate multi-objective function. The GRNNs model demonstrated excellent performance, achieving high R2 values of 0.952 and 0.918, low RMSE values of 0.659 and 0.310, and MdAPE values of 2.675% and 5.098% for brake thermal efficiency (BTE) and NOx, respectively. The NSGA-II algorithm with GRNNs model proved successful in predicting the multi-objective function in the optimization process, even with limited data. The Pareto frontier analysis revealed an optimal DEE percentage of approximately 10% to 14% for maximum BTE and minimum NOx, with engine loads distributed around 30, 40, and 100 N m.

Kinetic Analysis of Devolatilized Diesel-Soot Oxidation Catalyzed by Ag/Al2O3 and Ag/CeO2 Using Isoconversional and Master-Plots Techniques.

This work presented the kinetic analysis of devolatilized diesel-soot combustion accelerated by Ag/Al2O3 and Ag/CeO2 catalysts. Isoconversional and master-plots techniques were employed to estimate activation energy and identify the reaction model. The apparent activation energy of uncatalyzed soot oxidation was 101.85 kJ/mol, and it was reduced to 61.85 and 82.78 kJ/mol for the combustion catalyzed by Ag/Al2O3 and Ag/CeO2, respectively. The reaction-order model, f(α) = (1- α)n, with n of 1.4, 1, and 1 showed the best fit for the uncatalyzed soot oxidation and soot oxidation catalyzed by Ag/Al2O3 and Ag/CeO2, respectively. The proposed single-step reaction models were quite capable of reproducing experiments for the uncatalyzed soot oxidation and soot oxidation catalyzed by Ag/CeO2. In the presence of Ag/Al2O3, the oxidation rate at the first 20% of conversion was faster than the 1st-order reaction reflecting that the soot was rapidly oxidized by highly active species generated by Ag/Al2O3. The oxidation of the remaining soot closely followed the 1st-order reaction mechanism.

Oleaginous yeast, Rhodotorula paludigena CM33, platform for bio-oil and biochar productions via fast pyrolysis.

An oleaginous yeast Rhodotorula paludigena CM33 was pyrolyzed for the first time to produce bio-oil and biochar applying a bench-scale reactor. The strain possessed a high lipid content with the main fatty acids similar to vegetable oils. Prior to pyrolysis, the yeast was dehydrated using a spray dryer. Pyrolysis temperatures in the range of 400-600 °C were explored in order to obtain the optimal condition for bio-oil and biochar production. The result showed that a maximum bio-oil yield of 60% was achieved at 550 °C. Simulated distillation gas chromatography showed that the bio-oil contained 2.6% heavy naphtha, 20.7% kerosene, 24.3% biodiesel, and 52.4% fuel oil. Moreover, a short path distillation technique was attempted in order to further purify the bio-oil. The biochar was also characterized for its properties. The consequence of this work could pave a way for the sustainable production of solid and liquid biofuel products from the oleaginous yeast.

Utilizing Waste Plastic Bottle-Based Pyrolysis Oil as an Alternative Fuel.

In the present work, an experimental investigation is carried out on the use of waste plastic oil produced from waste poly(ethylene terephthalate) (PET) bottles (WPOB) as an alternative fuel for diesel engines. The physical and chemical properties of WPOB were analyzed, and it was found that it has fuel properties similar to those of petroleum fuels. The WPOB was tested in a diesel engine to evaluate the effect of WPOB on combustion and emissions characteristics. In addition, particulate matter (PM) emissions generated by the combustion of WPOB were analyzed. The combustion of WPOB was retarded with respect to diesel fuel, resulting in higher carbon-based emissions. The thermogravimetric analysis (TGA) results show that the temperature to reach the maximum rate of soot oxidation was lower with WPOB combustion. Because of the significant delay at the start of combustion and increase in emissions, the direct use of WPOB in the diesel engine is not recommended. It is suggested that WPOB can be used as a blend component to reduce the amount of diesel fuel used in diesel engines. Thus, further study on the effect of diesel fuel blended with WPOB on the combustion and emissions characteristics was performed. The results reveal that the maximum WPOB present in diesel fuel to avoid the increase in carbon-based emissions is 20% by volume to keep combustion and emissions characteristics similar to those of diesel fuel.

Distilled Waste Plastic Oil as Fuel for a Diesel Engine: Fuel Production, Combustion Characteristics, and Exhaust Gas Emissions.

Waste plastic oil (WPO) derived from pyrolysis of plastic debris and municipal waste is one of the promising alternative fuels because of its similar carbon chain characteristics and physical properties to diesel fuel. WPO also contains naphtha which is gasoline-like and may not be well-suited to a diesel engine. Technically, naphtha should be eliminated from WPO by distillation, and the resulting product is called distilled waste plastic oil (WPOD). This work experimentally investigates the influences of these fuels burned in a diesel engine on combustion characteristics and exhaust gas emissions. Both WPO and WPOD fuels contribute to the larger amount of nitrogen oxides than diesel fuel. Carbon-based emissions increase when the engine operates with these pyrolysis fuels by retarding the ignition onset of their combustion occurrences. Meanwhile, their shorter-carbon-chain links provide a lower smoke index. However, brake thermal efficiency and brake specific fuel consumption are beneficial because of their high calorific value and cetane index.

Effects of Diesel-Biodiesel-Ethanol Fuel Blend on a Passive Mode of Selective Catalytic Reduction to Reduce NO x Emission from Real Diesel Engine Exhaust Gas.

The effects of ethanol on combustion and emission were investigated on a single-cylinder unmodified diesel engine. The ethanol content of 10-50 vol % was chosen to blend with diesel and biodiesel fuels. Selective catalytic reduction (SCR) of nitrogen oxides (NO x ) in the passive mode was also studied under real engine conditions. Silver/alumina (Ag/Al2O3) was selected as the active catalyst, and H2 (3000-10000 ppm) was added to assist the ethanol-SCR. The low cetane number of ethanol resulted in longer ignition delay. The diesel-biodiesel-ethanol fuel blends caused an increase in fuel consumption due to their low calorific value. The brake thermal efficiency of the engine fuelled with relatively low ethanol fraction blends was higher than that of diesel fuel. Unburned hydrocarbons (HC) and carbon monoxide (CO) increased, while NO x decreased with ethanol quantity. The higher ethanol quantity led to increases in the HC/NO x ratio which directly affected the performance of NO x -SCR. Addition of H2 considerably improved the activity of Ag/Al2O3 for NO x reduction. The proper amount of H2 added to promote the ethanol-SCR depended strongly on the temperature of the exhaust where a high fraction of H2 was required at a low exhaust temperature. The maximum NO x conversion of 74% was obtained at a low engine load (25% of maximum load), an ethanol content of 50 vol %, and H2 addition of 10000 ppm.