Mobile Low-Field 1H NMR Spectroscopy Desktop Analysis of Biodiesel Production

Biodiesel produced mainly by the base-catalyzed transesterification of vegetable oils or animal fats with a short chain alcohol, has become an attractive alternative to petroleum-based diesel fuel. Even though high-field ¹H nuclear magnetic resonance (NMR) is a reliable method for biodiesel quality control, it is restricted by its poor mobility and expensive superconducting coils. As an alternative, this study presents a mobile low-field ¹H NMR spectrometer for the analysis of biodiesel samples derived from different feedstock oils. The low-field ¹H NMR spectra of all the compounds coexisting in a typical transesterification reaction such as rapeseed oil, rapeseed biodiesel, methanol, and glycerol, could be clearly differentiated. Field-dependent characteristic parameters such as relaxation times are provided. The degree of saturation of the different biofuels samples could be reliably estimated via integration of the resolved signals of the spectra. The obtained results agreed well with those measured at high-field ¹H NMR. Since this compositional information is directly related to the biodiesel properties, the presented mobile low-field ¹H NMR device built from permanent magnets arrayed in a Halbach geometry, constitutes an excellent alternative tool for biodiesel quality control.     

Quantification of Ethanol in Ethanol-Petrol and Biodiesel in Biodiesel-Diesel Blends Using Fluorescence Spectroscopy and Multivariate Methods

Ethanol blended petrol and biodiesel blended diesel are being introduced in many countries to meet the increasing demand of hydrocarbon fuels. However, technological limitations of current vehicle engine do not allow ethanol and biodiesel percentages in the blended fuel to be increased beyond a certain level. As a result quantification of ethanol in blended petrol and biodiesel in blended diesel becomes an important issue. In this work, calibration models for the quantification of ethanol in the ethanol-petrol and biodiesel in the biodiesel-diesel blends of a particular batch were made using the combination of synchronous fluorescence spectroscopy (SFS) with principal component regression (PCR) and partial least square (PLS) and excitation emission matrix fluorescence (EEMF) with N-way Partial least square (N-PLS) and unfolded-PLS. The PCR, PLS, N-PLS and unfolded-PLS calibration models were evaluated through measures like root mean square error of cross-validation (RMSECV), root mean square error of calibration (RMSEC) and square of the correlation coefficient (R ²). The prediction abilities of the models were tested using a testing set of ethanol-petrol and biodiesel-diesel blends of known ethanol and biodiesel concentrations, error in the predictions made by the models were found to be less than 2%. The obtained calibration models are highly robust and capable of estimating low as well as high concentrations of ethanol and biodiesel.     

An ultrasonic-accelerated oxidation method for determining the oxidative stability of biodiesel

Biodiesel is considered an alternative energy because it is produced from fats and vegetable oils by means of transesterification. Furthermore, it consists of fatty acid alkyl esters (FAAS) which have a great influence on biodiesel fuel properties and in the storage lifetime of biodiesel itself. The biodiesel storage stability is directly related to the oxidative stability parameter (Induction Time – IT) which is determined by means of the Rancimat® method. This method uses condutimetric monitoring and induces the degradation of FAAS by heating the sample at a constant temperature. The European Committee for Standardization established a standard (EN 14214) to determine the oxidative stability of biodiesel, which requires it to reach a minimum induction period of 6 h as tested by Rancimat® method at 110 °C. In this research, we aimed at developing a fast and simple alternative method to determine the induction time (IT) based on the FAAS ultrasonic-accelerated oxidation. The sonodegradation of biodiesel samples was induced by means of an ultrasonic homogenizer fitted with an immersible horn at 480 Watts of power and 20 duty cycles. The UV–Vis spectrometry was used to monitor the FAAS sonodegradation by measuring the absorbance at 270 nm every 2. Biodiesel samples from different feedstock were studied in this work. In all cases, IT was established as the inflection point of the absorbance versus time curve. The induction time values of all biodiesel samples determined using the proposed method was in accordance with those measured through the Rancimat® reference method by showing a R² = 0.998.     

Cavitation based cleaner technologies for biodiesel production and processing of hydrocarbon streams: A perspective on key fundamentals,missing process data and economic feasibility – A review

The present review emphasizes the role of hydrodynamic cavitation (HC) and acoustic cavitation in clean and green technologies for selected fuels (of hydrocarbon origins such as gasoline, naphtha, diesel, heavy oil, and crude oil) processing applications including biodiesel production. Herein, the role of cavitation reactors, their geometrical parameters, physicochemical properties of liquid media, liquid oxidants, catalyst loading, reactive oxygen species, and different types of emulsification and formation of radicals, formation as well as extraction of formed by-products are systematically reviewed. Among all types of HC reactors, vortex diode and single hole orifices revealed more than 95 % desulfurization yield and a 20 % viscosity reduction in heavy oil upgrading, while multi-hole orifice (100 holes) and slit Venturi allowed obtaining the best biodiesel production processes in terms of high (%) yield, low cost of treatment, and short processing time (5 min; 99 % biodiesel; 4.80 USD/m³). On the other hand, the acoustic cavitation devices are likely to be the most effective in biodiesel production based on ultrasonic bath (90 min; 95 %; 6.7 $/m³) and desulfurization treatment based on ultrasonic transducers (15 min; 98.3 % desulfurization; 10.8 $/m³). The implementation of HC-based processes reveals to be the most cost-effective method over acoustic cavitation-based devices. Finally, by reviewing the ongoing applications and development works, the limitations and challenges for further research are addressed emphasizing the cleaner production and guidelines for future scientists to assure obtaining comprehensive data useful for the research community.     

Determination of the Biodiesel Content in Diesel/Biodiesel Blends: A Method Based on Fluorescence Spectroscopy

Blends of biodiesel and diesel are being used increasingly worldwide because of environmental, economic, and social considerations. Several countries use biodiesel blends with different blending limits. Therefore, it is necessary to develop or improve methods to quantify the biodiesel level in a diesel/biodiesel blend, to ensure compliance with legislation. The optical technique based on the absorption of light in the mid-infrared has been successful for this application. However, this method presents some challenges that must be overcome. In this paper, we propose a novel method, based on fluorescence spectroscopy, to determine the biodiesel content in the diesel/biodiesel blend, which allows in loco measurements by using portable systems. The results showed that this method is both practical and more sensitive than the standard optical method.     

Modeling of process intensification of biodiesel production from Aegle Marmelos Correa seed oil using microreactor assisted with ultrasonic mixing

Conventionally, the batch type reactors were used for the production of biodiesel. However, in recent years, the usage of microreactors has started emerging as a significant substitute for biodiesel production due to its higher conversion rate at a short duration. These microreactors have a significantly high surface to volume ratio and high heat-mass transfer rate. The disadvantage of this type of reactors is its low mixing rate of the reagents. This can be overcome with the assistance of ultrasonic mixing. The main objective of this paper is to study the interlaced effect of a continuous flow microreactor and ultrasonic mixing on trans-esterification of Aegle Marmelos Correa seed oil using sodium methoxide catalyst. Results of microreactors with 0.3 mm and 0.8 mm diameter were compared. The effects of process parameters namely, flow rate (2–10 mL/min), reaction temperature (45–65 °C), catalyst amount (0.5–2.5 wt%), oil to methanol molar ratio (1:6–1:18) and ultrasonic mixing time (30–150 s) were studied using response surface methodology (RSM). The biodiesel yield of 98% and 91.8% were obtained for 0.3 mm and 0.8 mm microreactors, respectively. The maximum biodiesel yield observed in 0.3 mm reactor under following optimum conditions: 6.8 mL/min flow rate, 48 °C reaction temperature, 1.3 wt% catalyst, 1:9 oil to methanol molar ratio and 83 s ultrasonic mixing time. The predictive and generalization abilities of RSM and artificial neural network (ANN) models were evaluated and compared. The study showed that ANN and RSM models could predict the yield with an R² value of 0.9955 and 0.9900 respectively. However, the ANN model predicted the yield with the least mean square error value of 0.00001294, which is much lower than RSM.     

Influence of zinc ion implantation on surface nanomechanical performance and corrosion resistance of biomedical magnesium-calcium alloys

It is believed that magnesium and its alloys may find applications in biomedical fields as implants, bone fixation devices, and tissue engineering scaffolds. However, their corrosion rate must be controlled. In this study, biomedical magnesium-calcium (Mg-Ca) alloys were ion-implanted with zinc. The surface nanomechanical performance and corrosion behavior of the ion-implanted Mg-Ca alloys are determined. The results show that zinc ion implantation at a dose of 0.9 × 10¹⁷ ions/cm² significantly improves the surface hardness and modulus. However, the results on corrosion resistance reveal that zinc ion implantation degrades the corrosion behavior of Mg-Ca alloys. Thus, zinc is not a favorable element for the ion implantation treatment of biomedical Mg-Ca alloys.     

Raman and IR spectroscopy study of corrosion products on the surface of the hot‐dip galvanized steel with alkaline mud adhesion

The corrosion products formed on hot‐dip galvanized steel sheets for the automobile application with adhesion of alkaline mud containing different Cl⁻ ion contents are investigated by means of Raman and infrared (IR) spectroscopy. Results show that the Cl⁻ ion content in alkaline mud has great influence on the corrosion behavior of the galvanized steel. The Cl⁻ ions are responsible for the formation of the Zn₅Cl₂(OH)₈· H₂O layer on the surface of the steel at the early stage of corrosion. The rest of the Cl⁻ ions then penetrate and interrupt corrosion product layer resulting in pitting corrosion. Subsequently, the red corrosion product of α‐FeOOH (shaped as needle‐like structure) is formed, which then transforms into black rust of Fe₃O₄ (having a shape of slim needle). It is interesting to find out that pitting depth is inversely proportional to the Cl⁻ ion content. However, corrosion rate decreases with the increase of the Cl⁻ ions in mud. Copyright © 2009 John Wiley & Sons, Ltd.     

Modification of medical metals by ion implantation of copper

The effect of copper ion implantation on the antibacterial activity, wear performance and corrosion resistance of medical metals including 317 L of stainless steels, pure titanium, and Ti-Al-Nb alloy was studied in this work. The specimens were implanted with copper ions using a MEVVA source ion implanter with ion doses ranging from 0.5 × 10¹⁷ to 4 × 10¹⁷ ions/cm² at an energy of 80 keV. The antibacterial effect, wear rate, and inflexion potential were measured as a function of ion dose. The results obtained indicate that copper ion implantation improves the antibacterial effect and wear behaviour for all the three medical materials studied. However, corrosion resistance decreases after ion implantation of copper. Experimental results indicate that the antibacterial property and corrosion resistance should be balanced for medical titanium materials. The marked deteriorated corrosion resistance of 317 L suggests that copper implantation may not be an effective method of improving its antibacterial activity.     

Analysis of EIS characteristics of CO2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO₂ corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO₂ corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical impedance spectra. Additionally, pitting of N80 steel could lead to additional capacitive reactance in impedance spectrum. The ion diffusion coefficient in corrosion scale and porosity of corrosion scale could be calculated by Warburg impedance coefficient, the results shown that the value of H⁺ diffusion coefficient in N80 and 4Cr corrosion scale is (3.46 and 1.76) × 10⁻¹⁰ m² s⁻¹, respectively. The protective ability of 4Cr corrosion scale was better than that of N80 corrosion scale.     

Fe–Mn–Al–C Alloys: a Study of Their Corrosion Behaviour in SO2 Environments

The corrosion reaction of four Fe–Mn–Al alloys exposed to a cycling, dry–humid, SO₂ (0.001% by volume) polluted atmosphere was studied. ICEMS, XPS, AES-SAM and transmission Mössbauer spectroscopy at different temperatures were employed to characterize the corrosion products. The analytical results indicate that (i) ferrihydrite is the main component of the rust; (ii) there is an abundant presence of Mn²⁺ and SO₃ ^2–/SO₄ ^2– on the top of the corrosion layer, the concentration of SO₄ ^2– increasing with the number of cycles; and (iii) the magnetic hyperfine pattern exhibited by the series of low-temperature spectra of the rust is quite different from that observed in the rust formed under similar corrosive environments on iron and weathering steel. This latter finding is correlated with a slow rate of transformation of the Fe³⁺ species formed at the early stages of corrosion into -FeOOH, the usual final product of this type of corrosion processes. The sulphate anions, abundant inside the electrolyte during the wet periods, could be incorporated to the ferrihydrite structure being responsible for the Mössbauer spectral pattern recorded from the corrosion products at low temperatures.     

Development of a reduced biodiesel surrogate model for compression ignition engine modeling

Methylbutanoate (MB), a C₄ methyl ester, represents the simplest surrogate that captures the chemical effects of the ester moiety in biodiesel and biodiesel surrogates. An updated chemical kinetic model has been developed to characterize the ignition and flame characteristics of MB. The mechanistic elements within this model that relate to the MB and smaller ester/oxygenate sub-mechanisms are drawn from the prototypical Fisher et al. model and from more recent theory and modeling efforts. The MB model development which is based on an iterative procedure involving global sensitivity analyses to identify elementary reactions that govern ignition and subsequent high level ab initio based theoretical updates to these reaction rates are presented. The MB model makes reasonable predictions of ignition delays and laminar flame speeds.The C₅–C₇ submechanisms from the LLNL n-heptane (NH) model were merged with the present MB model to obtain a detailed chemical kinetics model for a surrogate blend representing biodiesel. The detailed MB-NH model (661 species) was reduced using graph based techniques. The robust reduction techniques employed result in a reduced model (145 species) that is in good agreement with the detailed model over a wide range of conditions. 3-D compression ignition (CI) engine simulations utilizing this reduced chemistry model for MB-NH blends as a surrogate for biodiesel show good agreement with the experimental data suggesting the utility of this model for predictions of combustion and emission characteristics of biodiesel in realistic CI engine simulations.     

Influence of Ni deposition and subsequent N ion implantation at different substrate temperatures on nano-structure and corrosion behaviour of type 316 and 304 stainless steels

Ni thin films of 250 nm thicknesses were coated on type 304 and 316 stainless steels and post N⁺ ion implanted at 15 keV energy with a fluence of 5 × 10¹⁷ N⁺ cm⁻² at different substrate temperatures. Surface nano-structure of the samples were analysed using X-ray diffraction (XRD), atomic force microscopy (AFM) before corrosion test and scanning electron microscopy (SEM) after corrosion test. Corrosion behaviour of the samples in 1.0 M H₂SO₄ solution was investigated by means of potentiodynamic technique. Nano-structure and crystallography of the films showed the development of Ni₃N(1 1 1) and Ni₄N(2 0 0) orientations with a minimum surface roughness and grain size at 400 K substrate temperature. The highest corrosion resistance with a corrosion current of 0.01 μA cm⁻² (for SS(316)) and 0.56 μA cm⁻² (for SS(304)) was achieved in case of samples which were N⁺ ion implanted at 400 K. Results for both types of stainless steels showed good agreement and the better performance of SS(316) was attributed to the 2% molybdenum contents in the alloy composition of this type of stainless steel, which enhances the effectiveness of nitrogen in retarding the corrosion process.     

Characterization of the corrosion products formed on mild steel in acidic medium with N-octadecylpyridinium bromide as corrosion inhibitor

The characterization of the corrosion products formed on mild steel SAE 1018 after 2 months exposure in aqueous sulfuric acid with and without corrosion inhibitor N-octadecylpyridinium bromide has been carried out by means of transmission ⁵⁷Fe Mössbauer spectroscopy and X-ray powder diffraction (XRD). The major constituent of the rust formed in this environment without corrosion inhibitor is goethite (??-FeOOH). The samples with N-octadecylpyridinium bromide contain rozenite and large amounts of melanterite in the corrosion layers.     

Prediction of NOx emissions from a simplified biodiesel surrogate by applying stochastic simulation algorithms (SSA)

A stochastic simulation algorithm (SSA) approach is implemented with the components of a simplified biodiesel surrogate to predict NOx (NO and NO₂) emission concentrations from the combustion of biodiesel. The main reaction pathways were obtained by simplifying the previously derived skeletal mechanisms, including saturated methyl decenoate (MD), unsaturated methyl 5-decanoate (MD5D), and n-decane (ND). ND was added to match the energy content and the C/H/O ratio of actual biodiesel fuel. The MD/MD5D/ND surrogate model was also equipped with H₂/CO/C₁ formation mechanisms and a simplified NOx formation mechanism. The predicted model results are in good agreement with a limited number of experimental data at low-temperature combustion (LTC) conditions for three different biodiesel fuels consisting of various ratios of unsaturated and saturated methyl esters. The root mean square errors (RMSEs) of predicted values are 0.0020, 0.0018, and 0.0025 for soybean methyl ester (SME), waste cooking oil (WCO), and tallow oil (TO), respectively. The SSA model showed the potential to predict NOx emission concentrations, when the peak combustion temperature increased through the addition of ultra-low sulphur diesel (ULSD) to biodiesel. The SSA method used in this study demonstrates the possibility of reducing the computational complexity in biodiesel emissions modelling.     

Corrosion and wear properties of laser surface modified NiTi with Mo and ZrO2

Because of its biocompatibility, superelasticity and shape memory characteristics, NiTi alloys have been gaining immense interest in the medical field. However, there is still concern on the corrosion resistance of this alloy if it is going to be implanted in the human body for a long time. Titanium is not toxic but nickel is carcinogenic and is implicated in various reactions including allergic response and degeneration of muscle tissue. Debris from wear and the subsequent release of Ni⁺ ions due to corrosion in the body system are fatal issues for long-term application of this alloy in the human body.This paper reports the corrosion and wear properties of laser surface modified NiTi using Mo and ZrO₂ as surface alloying elements, respectively. The modified layers which are free from microcracks and porosity, act as both physical barrier to nickel release and enhance the bulk properties, such as hardness, wear resistance, and corrosion resistance. The electrochemical performance of the surface modified alloy was studied in Hanks’ solution. Electrochemical impedance spectroscopy was measured.     

Fiber-optic sensor for the estimation of microbial corrosion of metals

This paper presents an optical approach to estimate the degree of corrosion of metals by measuring the changes in surface texture. The principle behind this method is based on scattering of light by objects. Source fiber is used to focus the light on the biocorroded metal surface. The resultant scattered and reflected light intensities are measured individually using detector fibers placed at different angles. The degree of corrosion is estimated as a ratio of scattered and reflected light intensities of specimen surface in a relative scale from 0 to 100. The observed optical measurements correlate well with the measured corrosion rate (correlation coefficient (R²)=0.972). A consistent relationship is found between optical measurements and corrosion levels.     

Experimental simulation of possible radiation-corrosive processes in container with spent nuclear fuel after groundwater ingress

Radiation corrosion in deaerated water/carbon steel systems has been studied. Kinetics of releasing corrosion products into the water and their sorption on the surface of steel tablets is affected by various factors (redox potential, absorbed dose, temperature, irradiation duration). Concentration of corrosion products in the solution was evaluated using various chemical methods. Total concentration of Fe²⁺/Fe³⁺ ions in liquid phase was determined by UV/VIS spectrometry. Solid phase was analysed using X-ray diffraction method. Corrosion processes were studied in deaerated distilled water and synthetic granitic water. Corrosion cells consisted of glass ampoules with inserted steel tablets, completely filled with deoxygenated water. Corrosion cells were carefully enclosed so that air diffusion into system during experiment was kept at minimum. ⁶⁰Co gamma sources with various dose rates were used for irradiation. The obtained results indicated that radiation noticeably contributed to the formation of corrosion products. Kinetics of radiation corrosion was strongly dependent on the parameters under study. The obtained experimental data should be taken into consideration when predicting effects of corrosion on containers with spent nuclear fuel using mathematical models.     

Poly (3-aminobenzoic acid) @ MWCNTs hybrid conducting nanocomposite: preparation,characterization, and application as a coating for copper corrosion protection

Nowadays, corrosion is a widely observed phenomenon in metal and one of the most important reasons of degradation in industrial parts. As a result, developing and applying the methods to reduce corrosion costs in industry is essential. In this research, emulsion polymerization route was used to prepare poly (3-aminobenzoic acid) @ multi-walled carbon nanotubes (P3ABA@MWCNTs) hybrid conducting nanocomposite film. Different techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to evaluate structure and morphology of resultant materials. P3ABA@MWCNTs hybrid conducting nanocomposite demonstrated an improvement in the crystallinity as well as thermal stability. In this literature for the first time, P3ABA and P3ABA@MWCNTs hybrid conducting nanocomposite films were used as a coating for corrosion protection of copper metal. The corrosion inhibition applicability of the P3ABA and P3ABA@MWCNTs hybrid conducting nanocomposite films on copper immersed in salt solution (3.5 wt.%) was investigated by potentiodynamic polarization, electrochemical impedance spectroscopic (EIS), and open circuit potential (OCP) measurements. The results showed that the presence of MWCNTs in P3ABA matrix considerably improved the corrosion inhibition efficiency of copper metal where corrosion potential (E_corr) and corrosion current density (I_corr) were ?103 mV and 0.562 μA cm^?2, respectively. The good anti-corrosion activity of P3ABA@MWCNTs hybrid nanocomposite was most likely due to physical barrier effect, and anodic protection performance of P3ABA together enhances the overall compactness of the MWCNTs.     

Improving the empirical model for plasma nitrided AISI 316L corrosion resistance based on M?ssbauer spectroscopy

Traditional plasma nitriding treatments using temperatures ranging from approximately 650 to 730 K can improve wear, corrosion resistance and surface hardness on stainless steels. The nitrided layer consists of some iron nitrides: the cubic ?? ^?? phase (Fe₄N), the hexagonal phase ?? (Fe_2???3N) and a nitrogen supersatured solid phase ?? _N . An empirical model is proposed to explain the corrosion resistance of AISI 316L and ASTM F138 nitrided samples based on Mössbauer Spectroscopy results: the larger the ratio between ?? and ?? ^?? phase fractions of the sample, the better its resistance corrosion is. In this work, this model is examined using some new results of AISI 316L samples, nitrided under the same previous conditions of gas composition and temperature, but at different pressure, for 3, 4 and 5 h. The sample nitrided for 4 h, whose value for ??/?? ^?? is maximum (=?0.73), shows a slightly better response than the other two samples, nitrided for 5 and 3 h (??/?? ^?? = 0.72 and 0.59, respectively). Moreover, these samples show very similar behavior. Therefore, this set of samples was not suitable to test the empirical model. However, the comparison between the present results of potentiodynamic polarization curves and those obtained previously at 4 and 4.5 torr, could indicated that the corrosion resistance of the sample which only presents the ?? _N phase was the worst of them. Moreover, the empirical model seems not to be ready to explain the response to corrosion and it should be improved including the ?? _N phase.