Impact of tribo-morphological transformation of graphene on the viscosity of engine oils

One of the major factors that determines the choice of engine oil is its viscosity. This research investigates the impact of graphene on the viscosity of engine oil before and after IC engine operation. Morphological changes of the graphene flakes have been studied to understand its dependency on the rheological performance of engine oil. Graphene based nanolubricants were synthesized to meet API SN/CF 20W50 grade. Scanning electron microscopy graphs show that the graphene flakes undergo tribomorphological transformations to become tubes, helical coils and percolated structures. However, such changes do not significantly impact the viscosity of engine oil throughout its life-cycle

Mass transfer studies in liquid membrane hydrocarbon separations

The effects of operating parameters on mass transfer coefficients of benzene permeating through liquid surfactant membranes have been studied. The study indicates that major resistance to mass transfer lies in the aqueous membrane phase. Mixing intensities used in forming the emulsion and dispersing it in the external phase have relatively less influence. Using a simple membrane film model approach, these mass transfer coefficients can be predicted within reasonable limits. The membrane film thickness to be used in these predictions varies with the holdup of micro phase in the emulsion, and can be estimated from the recently proposed equation of Kataoka et al. 1. Introduction ~ Liquid membranes were first introduced by Li in 1968 [1,2], and are increasingly becoming important in low energy separation processes. Liquid membranes offer the principle advantages of higher selectivities and surface areas over conventional extraction and solid membrane processes. Liquid membranes, also known as "double emulsions", are of two types, o/w/o and w/o/w emulsions (o=oil; w=water). In the formation of a liquid membrane system, an emulsion of two immiscible phases is prepared, and this is dispersed into a third continuous phase. The encapsulated phase in the emulsion and the third phase are generally miscible, and the interstitial liquid between the phases acts as a liquid membrane. Surfactants or additives are added to the membrane phase to maintain stability, permeability and selectivity. Liquid membrane hydrocarbon separations may be effected by a separation mechanism based on differential permeation rates through the membrane due to differences in solubility and/or diffusion coefficients of components in the membrane. Further, significant enhancement of rates and selectivities can be achieved by encapsulating or trapping a reactive species inside the micro-droplets which will convert the solute species into a nonpermeating product; this *To whom correspondence should be addressed. 0376-7388/90/$03.50 @ 1990 - Elsevier Science Publishers B.V

Thermophysical properties of glycerol and polyethylene glycol (PEG 600) based DES

In this study, the Deep Eutectic Solvent (DES) is prepared based on glycerol and polyethylene glycol 600 (PEG) as hydrogen bond donor and choline chloride (ChCl) as hydrogen bond acceptor. The glycerol based DESs were formed with ratio of 1:2, 1:3, 1:4 and 1:5 whereas three-component DESs of ChCl, PEG and glycerol were synthesized with ratio 1:3:2, 1:4:2 and 1:5:2. The DESs were subjected to DSC, Karl Fishcer, thermal conductivity, viscosity and density testing. The melting temperature (Tm) for PEG based DESs were found to in the region of 18 °C. The moisture content in DESs were identified through Karl Fishcer testing was found to be < 1% which is desired when synthesizing a DES. The thermal conductivity of glycerol based DESs decreases with respect to pure glycerol whereas for PEG based DESs shows positive enhancement of thermal conductivity at temperatures below 60 °C. The viscosity of glycerol DESs decreases with increasing temperature and the value of PEG DESs' viscosities was found to be higher than the pure PEG. All the DES samples have linear decrease across a temperature range with highest density achieved at 1.2155 g/cm3 with temperature of 25 °C for molar ratio of ChCl to glycerol of 1:4 (DES 4)

Uncertainty Modeling of a Chemical System with a Flexible Node by Mapping the Fault Tree into the Response Surface Method

This paper elaborates three novel contributions in the field of chemical process safety. The first contribution is the identification and classification of chemical system variabilities into seven broad categories, namely, media, equipment, component, operator, procedural, management, and external (MECOPME). The identified variabilities lead to epistemic and aleatory types of uncertainties in the probabilistic safety analysis. To deal with the uncertainties caused due to the variabilities, a concept of the flexible node is proposed, which demands a failure probability in the flexible range of a lower level to a higher level instead of a fixed static probability. Since the existing techniques are not robust enough to handle the probability range, the classical fault tree is mapped into a statistically more reliable approach of the response surface method (RSM). The unique idea of using RSM in the failure analysis is demonstrated over the fault tree of an overtemperature scenario in a semipilot scale setup for the hydrogenation process and successfully evaluated over an industrial accident of the release prevention barrier scenario. The contour and surface plots of RSM reveal more information than the traditional approach of minimal cut sets. The statistical markers of RSM are a better substitute for the improvement index for sensitivity analysis. The proposed approach deals with chemical system variabilities and the lack of knowledge of exact occurrence probabilities more effectively.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc

SYNTHESIS AND THERMO-PHYSICAL CHARACTERIZATION OF GRAPHENE BASED TRANSFORMER OIL

Transformer oils serve as coolants and an insulation medium to avoid overheating. Due to low thermal conductivity of transformer oils which may result in overheating and hence nanoparticles are introduced to overcome this challenge. In this research, graphene nanoparticles (GNPs) were dispersed in transformer oil at a concentration of 0.01-0.1 wt% respectively. The stability of the graphenetransformer oil nanofluids (GTNFs) is studied using UV-Vis spectrophotometer.Optical microscope is used to study the dispersion quality and the uniformity of clusters formed at different weight fractions qualitatively. Thermal conductivity and viscosity of the samples were measured over a range of temperature from 20-100 °C. The thermal conductivity and viscosity of GTNFs were observed to be strongly dependent on the temperature and concentration of GNPs. The enhancement in thermal conductivity obtained was from 2.63-69.31 % as the temperatures varies from 20-100 °C, for 0.01-0.1 wt% of GNPs. It was also further observed that the viscosities of the GTNFs were reduced by 8.33-23.97% as the temperature rises allowing more convectional heat flow. It is thus concluded that the increase in thermal conductivity and decrease in viscosity as temperature rises enhances the overall performance of the transformer oil

Optimisation of extractive desulfurization using Choline Chloride-based deep eutectic solvents

Sulfur in fuels is one of the main sources of pollution. Thus, the desulfurization of fuel (gasoline and diesel) is demanding for effective and alternative solutions. Deep eutectic solvents (DES) are gaining rapid interest in extraction processes due to their excellent properties as a solvent. In this study, extractive desulfurization (EDS) of model oil containing dibenzothiophene (DBT) as an organo-sulfur compound was carried using Choline Chloride acting as Hydrogen bond acceptor (HBA) and Propionic acid (Pr) as Hydrogen bond donor (HBD), respectively. Experiments are performed to study the effect of DES molar ratio, temperature and sonication time on DBT removal efficiency with molar ratios of 1:2 and 1:3 (HBA:HBD) using response surface methodology (RSM). DBT is quantitatively analysed using high-performance liquid chromatogram (HPLC) and Fourier transform infrared spectroscopy (FTIR) studies. The results showed high removal efficiency of 64.9% at a temperature of 37 °C, 10 min sonication; 1:3 ratio of ChCl/Pr and at a treat ratio of 1:3 model oil in a single stage extraction. This study will provide an alternative green solution which requires shorter reaction time and lower operating temperature as compared to conventional method i.e. hydrodesulfurization (HDS)

Physical properties optimization of POME-groundnut-naphthenic based graphene nanolubricant using response surface methodology

In this research, different oil blends were produced by mixing naphthenic base oil, groundnut oil, palm oil methyl ester and nanometer thick graphene flakes. The thermophysical properties such as viscosity, thermal conductivity, volatility and suspension stabilities were measured and modeled for each oil and blends. Every individual parameter was modeled following quadratic multiple linear regression analysis and optimized using the desirability approach. The behavior of each selected property as a function of groundnut oil, palm oil methyl ester and graphene concentrations are discussed and consequently optimized to select the best combination of constituents. While groundnut oil, palm oil methyl ester and graphene were used as additives, had various effects independently on the property of naphthenic base oil. The first noteworthy observation is that the blends made with the higher composition of groundnut oil resulted in higher viscosity index, thermal conductivity, nanosuspension stability, and reduced volatility. Secondly, the viscosity index and thermal conductivity of graphene-based groundnut oil compared to pure naphthenic oil enhanced by 49% and 38% respectively. On the other hand, its stability and volatility reduced by 79% and 98% respectively. Thirdly, palm oil methyl ester as an additive was found to be less effective as the groundnut oil composition was increased. Overall, the results of this study show that groundnut oil, palm oil methyl ester and graphene could make excellent metalworking fluids and additives in different combinations