Diagnosis of lubricating oil by evaluating cyanide and carbon molecular emission lines in laser induced breakdown spectra

To prevent engine failure it is essential to change lubricating oil regularly before it loses its protective properties. It is also necessary to monitor the physical and chemical conditions of the oil to reliably determine the optimum oil-change intervals. The present work focuses on studying evolution of the cyanide (CN) and carbon (C₂) molecular spectral emission lines in the laser induced breakdown spectra of lubricating oil as a function of its consumption. The intensities of these molecular bands have been taken as indicator of engine oil degradation at certain mileage. Furthermore, the percentage of decay of CN and C₂ integral intensity values at the corresponding mileage was calculated in order to relate it to the degree of consumption of the motor oil. Such percentage decay of the CN and C₂ integral intensities have been found to increase gradually with increasing mileage which is accompanied with increasing depletion of engine oil. The results of using LIBS technique in the present measurements proved that it is possible to have a direct, straightforward and easy method for prediction of lubricating oil degree of consumption. This may facilitate scheduling the proper time and/or mileage intervals for changing the oil to avoid any possibility of engine failure.     

Confirmation of heavy metal ions in used lubricating oil from a passenger car using chelating self-assembled monolayer

In order to prevent engine failure, the oil must be changed before it loses its protective properties. It is necessary to monitor the actual physical and chemical condition of the oil to reliably determine the optimum oil-change interval. Our study focuses on the condition of the lubricating oil in an operated car engine. Shear stress curves and viscosity curves as a function of the shear rate for fresh and used lubricating oil were examined. Metal nitrate was detected in the lubricating oil from the operated car engine through the use of a chelating self-assembled monolayer.     

Combination of ultrasonic extraction and stripping analysis: an effective and reliable way for the determination of Cu and Pb in lubricating oils

The determination of metals in lubricating oil has been used as an important way to prevent components failures, to provide environmental information and in some cases, to identify adulteration. In this work, an effective and simple procedure is proposed for Cu and Pb determination in lubricating oils. An ultrasonic bath was employed for extraction of these elements from oil samples in a mixture 1:1 (v/v) of concentrated HCl and H₂O₂. A very efficient extraction of Cu and Pb (∼100%) was attained after 30 min of ultrasound, allowing the simultaneous determination of both metals using square-wave anodic stripping voltammetry at thin-film gold electrodes. The extraction procedure was performed in 4 mL polypropylene closed vessels and dozens of samples could be treated simultaneously in the same ultrasonic bath. The regions of the ultrasonic bath, where the maximum efficiency of extraction was attained were evaluated. Over the optimized region, 30 samples can be treated simultaneously. Used lubricating oils from automotive engines were analyzed by using the optimized extraction procedure.     

Thermogravimetric study of aerobic biodegradation of sanitary sewage sludge and lubricating oil

The present study describes the aerobic biodegradation process of a mixture of sanitary sewage sludge and lubricating oil. TG/DTG curves confirmed that the applied aerobic biological treatment decreased the organic material content and caused significant modifications in the thermal behavior of the studied substrates after the functioning period.     

New view on the oxidation mechanisms of crude oil through combined thermal analysis methods

In the previous study, the oxidation behavior of four Chinese crude oils (Oil 1 to 4) in the presence and absence of rock cuttings was investigated by thermogravimetry/derivative thermogravimetry (TG/DTG) techniques and oxidation tube experiments. The present work investigates the thermal behavior of these oils by combining DTG–DTA method. First, we conducted comparative analysis about mass loss rate from DTG curves and endothermic/exothermic phenomenon from DTA curves attempting to clarify the endothermic or exothermic mechanism in crude oil low-temperature oxidation. Finally, we combined the thermal analysis method with low-temperature oil oxidation tube experiment in porous media to ascertain, whether the two methods are consistent in the aspect of low-temperature oxidation mechanism of crude oil by O₂ consumption rate and CO₂ generating rate (carbon bond stripping reaction rate). Results show that crude oils undergo an endothermic oxidation behavior during low-temperature oxidation stage, suggesting the decomposition of hydrocarbon components. Clay can play a catalytic effect on low-temperature oil oxidation. The results of DTG–DTA tests can also better reflect oil oxidation mechanism under real conditions.     

Engine lubricating oil classification by SAE grade and source based on dielectric spectroscopy data

Dielectric spectroscopy (DS) is one of the most powerful and prevailing structural analysis techniques for dielectric materials. Engine lubricating oil is a typical dielectric material. But DS for qualitative or quantitative analysis of engine lubricating oil has received little attention. In this paper, DS in association with support vector machines (SVM) classification technique was employed to classify 20 samples of engine lubricating oils from Mobil, Shell and Esso by Society of Automotive Engineers (SAE) viscosity grade and source (manufacturer). Both distinguishing the multi-grade from the single-grade according to SAE grade and classification according to manufacturer were done perfectly, which proved that DS can provide useful compositional and structural information on engine lubricating oil. The work in this article has laid the foundation for further quantitative determination of properties of engine lubricating oil and will be a good start to application of DS to petroleum analysis and testing.     

Thermal kinetics study of light oil oxidation using TG/DTG techniques

In this study, the oxidation behavior of crude oils in the presence and absence of rock cuttings was investigated by thermogravimetry/derivative thermogravimetry (TG/DTG) techniques. Prior to these tests, the composition of cuttings and properties of crude oils were analyzed. Three obvious reaction regions were observed from the TG/DTG curves which are recognized as low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation. The effects of light components (C_7–15), heavy fractions (asphaltene, paraffin, resin), and cutting on oil oxidation behavior were analyzed. Kinetic analysis of crude oils and oil + cutting mixtures was performed by Arrhenius method, and the data were analyzed at last. Results show that high content C_7–15 hydrocarbons can provide negative effect on the LTO behavior of crude oil. On the contrary, the high content unsaturated heavy hydrocarbons including asphaltene, paraffin, and resin are benefit for the oxidation performance. In addition, a shortened FD stage and higher peak temperature in LTO region are observed by addition of cutting. Cutting especially clay in it plays an active role of catalyzing in oil oxidation reaction.     

Viscosity modification of lubricating oil based on high-concentration silica nanoparticle colloidal system

In this study, colloidal systems with SiO₂ nanoparticle as viscosity modifier additive were synthesized in the lubricating oil via an in situ Stober sol-gel method. The fluid characters of lubricating oil and viscosity variation were carefully investigated via rheological methods. The results showed that the lubricating oil transformed from Newtonian fluid to non-Newtonian fluid with increasing the concentration of nanoparticles, and smaller particles displayed better thickening effect toward lubricating oil. For the system with highly concentrated nanoparticle (20?wt%), the rheological behavior mainly depends on the size of nano-SiO₂. The lubricating oil with smaller nano-SiO₂ particles displayed higher structural strength and response rate, resulting in good recoverability after high-speed shear. The viscosity changed with temperature and also displayed a thermo-responsive behavior, which significantly alleviated the effect of shear thinning on the viscosity under high temperature. This study presented a new strategy for effectively tuning the fluid characters and modifying the viscosity of lubricating oils by adding highly concentrated inorganic nanoparticles.     

马瑞原油在空气和氮气中的热解-氧化性能

低温氧化是注空气采油及原位燃烧采油技术中的重要化学反应,为深入认识原油在有氧环境下复杂热反应过程中的低温氧化特性,我们采用热重/差热分析法(TG/DTA)研究了线性升温和等温条件下马瑞(Merey)原油的热反应行为。 结果表明,Merey原油在空气及线性升温条件下的受热过程分4个阶段:气化段、低温氧化段、热解段和高温氧化段;相邻阶段的物理、化学主导过程的重叠增加了分析原油热反应特征的难度。 升温速率提高,气化段和低温氧化段的终止温度不变;热解段和高温氧化段的终止温度以及热解段的峰温随升温速率的增加而升高。 N₂气与空气下Merey原油的热重/微分热重(TG/DTG)数据对比表明,升温速率越高,空气下的高温氧化段与热解段重叠程度越大,这有利于燃烧但会降低原油采收率。 空气下等温时的TG/DTA结果表明随升温速率增加,升温至300 ℃时的失重率降低,不利于原油轻组分的气化。 反应温度越高,气化过程时间越长,失重分数越大。 Merey原油在低于300℃时低温氧化反应不是主导反应。     

新型汽车发动机油用添加剂的研究进展

本文介绍了汽车发动机油用添加剂尤其是多功能添加剂的发展概况、作用机理、种类、结构及应用效果，并对未来润滑油添加剂的发展方向提供了一些参考，为我国润滑油品的高档化发展提出了几点想法。     

A thermogravimetric study of structural changes of lime wood (Tilia cordata Mill.) induced by exposure to simulated accelerated UV/Vis-light

A series of experiments were carried out to investigate photodegradation of lime wood (Tilia cordata Mill.) during artificial UV/Vis light irradiation for 600 h. Photodegradation of the wood samples was evaluated by thermogravimetry throughout the irradiation period at an interval of 100 h.The alteration of wood was observed by means of the peak temperatures of DTG variation and by the mass losses observed during heating, evaluated on the basis of the measured thermal data. The results obtained indicate a shifting of the DTG maxima to lower temperatures which may be related to the decreasing in the stability components during photodegradation. The values of the overall activation energies corresponding of the decomposition process progressively decreases.The decreased temperatures decomposition processes, weight losses and integral area of the peaks assigned to lignin, the increased integral area of the peaks assigned to hemicelluloses could be explained by new formed structures, mainly due to formation of reactive species.     

Gas-liquid chromatographic determination of the gaseous products of the two-stage pyrolysis of heavy oils

The two-stage pyrolysis of fuel oil and vacuum residues separated from Egyptian crude oil have been carried out using a batch-type reactor technique. In the first stage, feedstocks undergo catalytic cracking in the presence of platinum as a catalyst at temperatures ranging between 380 and 460 °C and 440 and 520 °C for fuel oil and vacuum residues, respectively. Products are carried by argon gas for subsequent pyrolysis in the second stage at temperatures ranging between 700 and 820 °C and 700 and 800 °C for fuel oil and vacuum residues, respectively. The gas yields are about 94.1 and 82.0 wt% of the total products. The gases comprise saturated (C₁----C₅) and unsaturated hydrocarbons (ethylene, propylene, and butenes). By using platinum wire in the pyrolysis of fuel oil, the ethylene yield increases slightly as the temperature of the first stage increases, while it remains almost unchanged in the pyrolysis of vacuum residue. On the other hand, the propylene yield decreases slightly as the temperature of the first stage increases in the two feedstocks. By using a platinum sheet, the ethylene yield is doubled under the same conditions and increases slightly with an increase of temperature in the second stage. On the other hand, the propylene yield varies inversely with the temperature of the second stage by using platinum, whether as wire or sheet, although the yield is higher when platinum sheet is used under the same conditions.     

Potentiometric Stripping Analysis for Simultaneous Determination of Copper and Lead in Lubricating Oils After Total Digestion in a Focused Microwave-Assisted Oven

The determination of metals in lubricating oil has been used as an important means of preventing components failures, to provide environmental information, and to solve criminal issues. In this study derivative potentiometric stripping analysis (DPSA) was used for the simultaneous determination of copper and lead in lubricating oils of vehicular engines. The samples were completely digested in a focused microwave-assisted oven using a powerful oxidant mixture (HNO₃, H₂SO₄, H₂O₂). The optimized heating program to digest about 1mL of lubricating oil takes 45minutes. The residual carbon content after digestion was below 0.3%m/m for all samples. Copper and lead were also determined by graphite furnace atomic absorption spectrometry (GFAAS), and the results obtained were in good agreement with those obtained by electrochemical measurements. Recoveries of 94–109 and 93–103%, for copper and lead, respectively, were obtained for new and used lubricating oil samples.     

Simultaneous IR/TG study of calcium carbonate in two aged cement pastes

Two aged cement pastes (7 years) were studied for H₂O and CO₂ evolution, the combined amounts of which were measured by TG and identified by thermo-IR analysis. This indicated the presence of three forms of carbonates, which decomposed at different temperatures. The displacement with time of the evaporation of sorbed water to higher temperatures (500–700°C, TG, MS) shows the possibility of its incorporation into carbonate hydrates and/or hydroxy hydrates, postulated previously. The decomposition of all the hydration products needed a thermal energy increasing with ageing (increased temperature measured by TG). The carbonation process proceeded for 7 years in the weaker paste, whereas it terminated before 5 years in the stronger one. The CSH water content did not change with ageing, whereas that of portlandite was lowered, which though did not account for the increase in carbonate content (TG). Possibly some Ca²⁺ from the CSH gel was involved in this process. In the stronger paste the growth with time of organic matter was found (IR, TG/DTG).     

Self-Assembled Structures of Diglycerol Monolaurate- and Monomyristate in Olive Oil

We have investigated the phase behavior and self-assembled structures of diglycerol monolaurate-and monomyristate (abbreviated as C₁₂G₂ and C₁₄G₂, respectivley) in olive oil over a wide range of temperatures and compositions. At lower temperatures, both the surfactants appear in solid state (α-solid), which does not swell with olive oil. The α-solid transforms into lamellar liquid crystal (L_α) phase upon heating and the solid melting temperature is practically constant at all surfactant/oil compositions, but the C₁₂G₂ melts earlier than the C₁₄G₂. There appear the dispersions of L_α phase and α-solid in the dilute regions of the C₁₂G₂/olive oil and the C₁₄G₂/olive oil systems, respectively, at 25°C. The L_α phase can solubilize some amount of olive oil, but as the oil concentration increases the excess oil separates out from the L_α phase, and there appears L_α dispersion in the dilute surfactant concentration region. The L_α phase eventually transforms into isotropic solutions (reverse micelles) with further heating. The structures (shape and size) of the reverse micelles have been characterized by small-angle x-ray scattering technique. It has found that the C₁₂G₂ and C₁₄G₂ surfactants form reverse rod-like micelles in olive oil above the L_α melting temperature and the micellar size increases with surfactant concentration, but decreases with temperatures.     

Investigation on the performance,emissions and combustion characteristics of CRDI engine fueled with tallow methyl ester biodiesel blends with exhaust gas recirculation

This paper demonstrates the study of performance, combustion and emission characteristics of a common rail diesel injection (CRDI) engine with the influence of exhaust gas recirculation (EGR) (5, 15 and 25%) at various fuel injection pressures (400, 500 and 600 bar) under the effective load conditions (0, 25, 50, 75 and 100%). The experiments were carried out in a controlled manner using the CRDI engine fuelled with 80% (D80) diesel (98% purity) blended with 20% (B20) tallow biodiesel. The engine has been operated at a rated speed of 1500 rpm on all load conditions, fuel injection timings of 10°, 15° and 20° bTDC, fuel injection pressures of 400, 500 and 600 bar, respectively. Combustion-influenced performance characteristics such as variation of in-cylinder pressure and net heat release rate in J deg^?1 are also studied with the above operating conditions. It was observed that the usage of 20% biofuel blend shows considerable improvement in combustion, and it further enhances with an increase in the injection pressures. Besides, EGR (up to 25%) reduced significant pollutants at higher operating pressures (600 bar) at higher load conditions. It was also observed that CO₂ emission increased with increase in the % EGR with an increase in the load conditions. However, for CO emission increased up to 50% load condition and subsequently tends to decrease due to improved combustion at higher load; hence higher temperature. NO_x, smoke opacity continue to increase with the increase in pressure and the percentage increase in EGR due to its attainment of adiabatic temperature, which leads to the pathway for the Zeldovich mechanism. The present work shows light on the usage of tallow methyl ester produced from the wastes in the tannery industry as alternate biofuel operating the CRDI engines without compromising its combustion and emission characteristics to deliver the same power as petro-diesel.

     

Thermal decomposition of ammonium copper chromate: effect of the addition of barium

The influence of the addition of barium (as barium chromate) to ammonium copper chromate on its thermal decomposition has been investigated by TG, DTG and DTA in the temperature range 303–1273 K. The solid products formed in the decomposition at different temperatures were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and also by measuring their specific surface area. The addition of BaCrO₄ at different concentrations (0–19.8%) was found not to change the general trend in the decomposition of ammonium copper chromate (which occurs in four distinct steps), except small changes in the temperature corresponding to DTG and DTA peaks. However, the sintering (or crystal growth) of the solid product is largely reduced by the presence of BaCrO₄.     

Thermal analysis of pyrotechnical mixtures II

A two-component pyrotechnical mixture containing MnO₂ and Pb₃O₄ has been investigated by TG, DTG and DTA. It was found that under 48 % MnO₂ content the oxygen release exceeds the value calculated on the basis of the reactions MnO₂ → Mn₃O₄ and Pb₃O₄ → PbO. Above a MnO₂ content of 7.5 % the decomposition is partly delayed and shifted to higher temperatures. With under 60% of MnO₂, at about 700? the components react exothermally with an increase in weight. The combined heats of the reactions MnO₂ → Mn₂O₃ and Pb₃O₄ → PbO give the highest value at 83 % of MnO₂.     

Osmotic swelling behavior of globules of W/O/W emulsion liquid membranes

The osmotic swelling behavior of water-in-oil-in-water (W/O/W) type emulsion liquid membranes (ELMs) was investigated. Using an optical microscope equipped with a camera, the changes in the size of the W/O/W globules were monitored over a long period of time (up to about 4 h). The osmotic pressure gradient between the internal and external aqueous phases was induced by creating a concentration difference of d-glucose between the two aqueous phases. The results indicate that the swelling ratio, defined as the ratio of globule diameter at time t to globule diameter at t=0, decreases with the increase in ϕ_W/O(0) (initial volume fraction of internal aqueous phase droplets). The swelling ratio generally increases with the increase in the concentration of surfactant present in the membrane (oil) phase. The permeation coefficient of water also increases with the increase in the surfactant concentration. With the increase in ϕ_W/O(0) up to about 0.42, the permeation coefficient decreases only slightly. However, with further increase in ϕ_W/O(0), a sharp reduction in the permeation coefficient occurs. The mechanism of water transfer in ELMs of the present work is reasoned to be the diffusion of hydrated surfactants.     

Application of a fractionary factorial design to the determination of tin in lubricating oils by continuous flow hydride generation-atomic absorption spectrometry

The determination of wear metals and metalloids in used lubricating oils allows the prediction of equipment failure. A number of procedures to determine wear metals in lubricating oils by atomic spectrometry has been published. Industry has lately shown a special interest in the determination of tin, since its appearance at certain levels in used oils indicates severe engine wear. Therefore, a method for the determination of the total tin content in used lubricating oils by hydride generation-atomic absorption spectrometry (HG-AAS) is described. Unused marine lubricating oils spiked with the analyte were digested in closed vessels in a microwave oven and the diluted product was used for continuous stannane generation. There are many factors that influence effective SnH₄ generation; therefore, fractionary factorial design was used to obtain an adequate sensitivity and also to stabilize the signal. Six variables were taken into account and a 2^6–2 _IV design was used with spiked samples containing 30 ng g^–1 Sn. The reproducibility, stability, calibration curve and limit of detection were established. The method was applied to different kinds of used lubricating oils. In all cases, the results were higher than those obtained in the industry by simple dilution.