Aqueous Glycerol Research Articles

Effect of distance between impeller blade tip and surface on mass transfer to a local electrode in a stirred vessel in a wide range of Sc number

ABSTRACT Stirred vessels are encountered in a wide scale of applications from bench to industrial processes, and the knowledge of the heat/mass transfer rates in these vessels is required for their design, operation and control. This work submits an investigation on the mass transfer to a small circular surface immersed in a stirred vessel in the parameter ranges of 267 < Re < 9437, 1473 < Sc < 61,422, and 0.022 < x/dK < 0.22 for the distance between the impeller blade tip and the transfer surface. The Reynolds number was based on the impeller diameter. The electrochemical limiting diffusion current technique having a potassium ferri-/ferrocyanide system was applied for mass transfer coefficient measurements. Aqueous glycerine solutions were prepared to attain a wide range of Sc numbers. The rate of mass transfer is enhanced with increasing rotation rate, decreasing blade tip-to-electrode surface distance, and decreasing glycerine concentration. The experimental data were well correlated by the relation .

Сapillatry effects manifested in the process of draining a liquid film that evaporated into a gas cross flow

The aim of the work is to determine the regularities of changes in the width of the flowing liquid film evaporating into a gas cross flow resulting from thermocapillary and concentration-capillary effects (Marangoni effect).&#x0D; The research was carried out experimentally employing an installation with a heated (working) surface, on which a liquid film (water or aqueous glycerol solution) was flowing. A flow of air was fed into the space between the working surface and the enclosing wall located at a distance from it, evenly in height and perpendicularly to the film movement. The film width was measured along the height of the working surface and the obtained dependencies were presented as graphs for different parameters of the flowing process.&#x0D; In all experiments, the graphs have an initial section with a sharp decrease in the film width, below which its change occurs smoothly. The degree of reduction in the film width depending on the parameters of the flowing process can reach 80%. In laminar mode, the reduction of the film width is more uniform than in turbulent mode, when some rise of the curves beyond the initial section is observed and can be explained by intensive mixing of the liquid. As the initial liquid flow increases, the degree of reduction in the film width decreases. Significant influence on the change in the film width is exerted by the temperature of the working surface during the flow of water: with increasing temperature, the film width decreases. At values of this temperature greater than 100℃, the rise of the curves is observed, possibly associated with the transition to volumetric evaporation.&#x0D; When the glycerol solution is flowing, the temperature of the working surface less influences the change in film width, although its decrease along the height of the working surface is greater than for water. The process parameters such as initial liquid temperature, initial solution concentration, and velocity and air temperature have relatively little effect on the change in film width. To correct the area of the film evaporation surface, determined by technological calculation, the width of the average evaporation surface is introduced under capillary effects. Its value increases with the initial liquid flow. For water, this dependence is characterized by a jump-like decrease in the film width in the transition from laminar to turbulent flow mode. This effect is absent on the dependence for glycerol solution, which can be explained by its higher viscosity. As the temperature of the working surface increases, the width of the average evaporation surface of the film decreases, some decrease being also observed with an increase in air velocity. Empirical equations for estimation of the correction factor were obtained. Capillary effects in this case are expressed by decrease in the width of the film at the height of its runoff, which leads to the need to correct the area of the film evaporation surface determined by technological calculation.

Kinetic Study of Pd-Promoting Effect on Cu/ZnO/Al2O3 Catalyst for Glycerol Hydrogenolysis to Produce 1,2-Propanediol at Low Hydrogen Pressure

The promoting effect of Pd on a Cu/ZnO/Al2O3 catalyst for the aqueous glycerol hydrogenolysis process to produce 1,2-propanediol was studied. At a lower hydrogen pressure (2.07 MPa), using the Cu/ZnO/Al2O3 catalyst with 2 wt% Pd doped, could significantly improve the glycerol conversion (97.2%) and 1,2-propanediol selectivity (93.3%) compared with the unpromoted catalyst (69.4% and 89.7%, respectively). A power-law kinetic model, which took into account all the elementary reactions including glycerol dehydration and its reverse reaction, acetol hydrogenation, side reactions and ethylene glycol formation, was developed to comprehensively investigate the effect of Pd. Though the rate of glycerol dehydration using the Pd-promoted catalyst was found to be slightly lower, mainly due to the reduced number of acidic sites after adding Pd, the glycerol conversion rate was notably higher compared with using the unpromoted catalyst, mainly attributed to the enhanced activity of acetol hydrogenation by Pd. The rapid hydrogenation of acetol can inhibit the reverse reaction of glycerol dehydration, resulting in a higher glycerol conversion rate, so that glycerol dehydration is considered as the rate-determining step. In contrast, when the unpromoted catalyst was used, the rate of reverse glycerol dehydration was drastically increased due to the elevated acetol concentration, especially at a lower hydrogen pressure, resulting in a slower glycerol conversion rate; thus, acetol hydrogenation became the rate determining step. In addition, Pd can improve the reducibility of the catalyst, allowing the CuO to be reduced in situ during the reaction. Therefore, catalyst deactivation due to any potential oxidation of metallic copper during the reaction can be prevented.

Comparison of bubble removal performances of five membrane oxygenators with and without a pre-filter.

When employing minimal invasive extracorporeal circulation (MiECC), the removal of bubbles in the circuit is important to prevent air embolism. We investigated the bubble removal performance of the FHP oxygenator with a pre-filter and compared it with that of four oxygenators, including the Fusion oxygenator, Quadrox oxygenator, Inspire oxygenator, and FX oxygenator. A closed test circuit filled with an aqueous glycerin solution was used. Air injection (10mL) was performed prior to the oxygenator, and the number and volume of the bubbles were measured at the inlet and outlet of each oxygenator. At the inlet of the five oxygenators, there were no significant differences in the total number of bubbles detected. At the outlet, bubbles were classified into two groups according to the bubble size: ≥100μm and <100μm. Tests were performed at pump flow rates of 4 and 5L/min. For bubbles ≥100μm, which are considered clinically detrimental, the FHP was the lowest number and volume of bubbles at both pump flow rates compared to the other oxygenators. Regarding the bubbles <100μm, the number of bubbles was higher in the FHP than those in others; however, the volume of bubbles was significantly lower at 4L/min and tended to be lower at 5L/min. The use of the FHP with the pre-filter removed more bubbles ≥100μm in the circuit than that by the other oxygenators.

Visible-light-driven hydrogen production over ZIF-8 derived Co3O4/ZnO S-scheme based p-n heterojunctions

Photocatalytic hydrogen evolution has become an alternative tool for green fuel production from water. Nevertheless, the surface texture and vast bandgap energies are still open issues before realizing the visible light application. This study yields mesoporous hexagonal ZnO nanoparticles by calcinating the obtained zeolitic imidazolate framework (ZIF-8). In addition, the ZIF-8 is combined with a Co2+ source to yield 1.0–4.0 wt% Co3O4/ZnO p-n nanoheterojunctions by the same method. The produced heterojunctions formed 35 nm of Co3O4 nanoparticles on mesoporous ZnO exteriors and exhibited very high surface areas of 1571–1691 m2 g−1. The addition of Co3O4 to ZnO bared more exhaustive harvesting of visible light and reduced the bandgap from 3.45 to 2.76 eV. The photocatalytic hydrogen evolution over derived Co3O4/ZnO was performed in 10% aqueous glycerol solution and hexachloroplatinic acid as hole scavenger and cocatalyst precursor, correspondingly. The 3% Co3O4/ZnO verified superior H2 evolution of 2241 μmol g−1h−1, an 1834-times greater than the pure ZnO. The adjusted dose of this novel photocatalyst showed estimable reusability for five successive runs. The resourceful light-harvesting, minimizing bandgap and suppressing recombination explained the enhanced H2 evolution in the occurrence of Pt cocatalyst.

An experimental performance comparison of Newtonian and non-Newtonian fluids on a centrifugal blood pump

The use of substitute fluid with similar rheological properties instead of blood is important due to ethical concerns and high blood volume consumption in pump performance test before clinical applications. The performance of a centrifugal blood pump with hydrodynamic journal bearing is experimentally tested using Newtonian 40% aqueous glycerin solution (GS) and non-Newtonian aqueous xanthan gum solution of 600 ppm (XGS) as working fluids. Experiments are performed at four different rotational speeds which are 2700, 3000, 3300, and 3600 rpm; experiments using GS reach between 8.5% and 37.2% higher head curve than experiments using the XGS for every rotational speed. It was observed that as the rotational speed and flow rate increase, the head curve difference between GS and XGS decreases. This result can be attributed to the friction reduction effect when using XGS in experiments at high rotation speed and high flow rate. Moreover, due to different fluid viscosities, differences in hydraulic efficiency were observed for both fluids. This study reveals that the use of Newtonian fluids as working fluids is not sufficient to determine the actual performance of a blood pump, and the performance effects of non-Newtonian fluids are remarkably important in pump performance optimizations.

Superior Macro-Scale Tribological Performance of Steel Contacts Based on Graphene Quantum Dots in Aqueous Glycerol

Superior Macro-Scale Tribological Performance of Steel Contacts Based on Graphene Quantum Dots in Aqueous Glycerol

Quantitative determination of glycerol concentration in aqueous glycerol solutions by metamaterial-based terahertz spectroscopy

Glycerol is an important quality indicator for foodstuffs. There is an increasing request for one more accurate, reliable, and convenient detection of the glycerol concentrations. Terahertz radiation is highly sensitive to the low-frequency intermolecular interactions between the glycerol and waters. Considering the enhancement property of localized field from the metamaterials, terahertz spectroscopy has been utilized for the determination of glycerol content with metamaterial-based biosensor, where the interaction between the analyte and the terahertz wave can be greatly increased. But the quantitative sensing performance was poor due to the sensitivity limitation of single-mode resonance of metamaterial and the lack of appropriate modeling methods. We propose the optimized structural design with internal coupling and multiple resonances. The induced remarkable changes in the lineshape of different transmitted dip regions imply that our metastructure biosensor is of high sensitivity to the change of surrounding environment on the surface dielectric constant, which has been also verified by coupled Lorentz oscillator theory. Furthermore, the optimal partial least squares regression model with variables of spectral lineshape for the first dip region covering the frequency range of 0.45–0.85 THz was established. It shows more accurate and reliable predictions of glycerol concentrations with residual predictive deviation value of 6.095. Metamaterial-based terahertz spectroscopy combined with statistical modeling with lineshape features can provide one new strategy for quantitative sensing. It has great potential for the improvement of determination of analyte concentrations in the practical applications of food, pharmaceutical or cosmetic area.

A novel methodology for measuring batch settling velocities of particles using Electrical Resistance Tomography

This study demonstrates how to measure batch settling velocities of particles in columns at an unconventionally high vertical spatial resolution of 1 mm using Electrical Resistance Tomography (ERT). A novel methodology, which utilized a titled vessel fitted with an ERT sensor array and novel analytical equations, was tested on dilute Newtonian suspensions of fairly monodisperse spherical glass beads (4.8% v/v) with a d50 diameter of 123 µm in aqueous glycerol solutions at 80, 85 and 90 wt% concentrations. The model yielded settling velocities of 0.13, 0.076 and 0.043 mm/s for the three suspensions respectively, each approximating their predicted values with errors of 16.3, 14.4 and 2.29%, respectively. Data fluctuations were discerned in the dataset but their effect on the dataset quality was minimized by increasing the time step sizes by factors of 3, 4 and 9 for the 80, 85 and 90 wt% glycerol solutions, respectively.

Effects of Laser Peening Parameters on Plastic Deformation in Aqueous Glycerol Solution as Plasma Confinement Layer

Effects of Laser Peening Parameters on Plastic Deformation in Aqueous Glycerol Solution as Plasma Confinement Layer

Hydrogen photo-production from glycerol on platinum, gold and silver-modified TiO2-USY62 catalysts

In this work, photocatalysts consisting of TiO2 supported on zeolite (USY62) were synthesized by sol-gel method and, subsequently, a noble metal (Pt, Au, or Ag) was incorporated by impregnation or photodeposition. Zeolite-TiO2 composites were characterized by SEM, TEM, XRD, N2 adsorption-desorption, Raman and UV–vis spectroscopy, and well-dispersed anatase TiO2 particles (ca. 10 nm) that exhibited a blue-shift in the UV–vis absorption due to the size quantization effect were produced. The photocatalytic activity of all zeolite-TiO2 composites was examined by the photoreforming of aqueous glycerol solution (10% w/w) under UV and solar-simulated radiation. The activity of the zeolitic photocatalysts decreased in the order Pt > Au > Ag, being catalysts prepared by photodeposition more active than those prepared by impregnation. Moreover, Zeolite-supported TiO2, led to a TiO2 with smaller deactivation in H2 production than unsupported TiO2, which can be ascribed to the small TiO2 particle size or an interaction zeolite-TiO2. All in all, a photocatalyst (USY-Ti-PPt) with TiO2 up to four times more active than unsupported TiO2 under UV radiation was prepared.

Simultaneous Measurement of Refractive Index and Flow Rate Using a Co2+-Doped Microfiber

This paper has proposed and experimentally demonstrated an integrated Co2+-doped microfiber Bragg grating sensor (Co-MFBGS) that can measure the surrounding liquid refractive index (LRI) and liquid flow rate (LFR) simultaneously. The Co-MFBGS provides well-defined resonant modes of core and cladding in the reflection spectrum. By monitoring the wavelength of the cladding mode, the LRI can be measured; meanwhile, by monitoring the wavelength of the core mode caused by the heat exchange, the LFR can be measured. The LRI and LFR can be distinguished by the wavelength separation between cladding mode and core mode. The experimental results show that in aqueous glycerin solution, the maximum measurement sensitivity for LRI detection is −7.85 nm/RIU (refractive index unit), and the LFR sensitivity is −1.93 nm/(μL/s) at a flow rate of 0.21 μL/s.

Oxygen-vacancy-mediated catalytic methanation of lignocellulose at temperatures below 200°C

<h2>Summary</h2> Biomethane is a clean energy and a key platform chemical for modern chemical industries. The conversion of biomass, especially the most abundant lignocellulose, into biomethane is challenging and shows low selectivity either in chemical or biological processes. Herein, we report the direct methanation of biomass at temperatures below 200°C with >95% selectivity using interfacial oxygen-vacancy (V_O)-mediated catalysis over Ru/TiO₂. The biomass feedstock is oxidized by TiO₂ to form CO₂ and V_O, and CO₂ is then <i>in situ</i> reduced on Ru sites to CH₄, restoring the oxygen to V_O simultaneously. Various biomass resources were converted into methane with 82%–99% yields. Even lowering the temperature to 120°C, about 0.24 mmol g⁻¹ h⁻¹ of CH₄ with >99% selectivity was steadily produced from 50 wt % aqueous glycerol for 432 h. <i>In situ</i> X-ray photoelectron spectroscopy, infrared spectrometry, and DFT calculation confirm the V_O-mediated catalysis process over Ru/TiO₂.

Fabrication and Nanomechanical Characterization of Thermoplastic Biocomposites Based on Chemically Treated Lignocellulosic Biomass for Surface Engineering Applications

Diverse applications of polymeric materials have prompted development of eco-friendly, efficient, and economical materials. These characteristics can be obtained by incorporating appropriate fillers in the polymeric matrix. The objective of this work is to investigate impact of aqueous glycerol (Gly) treated rice husk (RH) on surface mechanical properties of produced biocomposites. RH was treated with aqueous Gly (75 wt%) and compounded with low density polyethylene (LDPE) at different loadings (10, 20, and 30 wt%). The resulting mixture was thermally pressed in molds to fabricate biocomposites. Surface mechanical properties such as elastic modulus, hardness, creep rate, and plasticity of biocomposites reinforced with untreated and treated RH were investigated using nanoindenter. Experimental values depicted that hardness (H) and elastic modulus (Es) of treated biocomposites were higher than untreated ones. Treated biocomposites showed the noticeable improvement in elastic modulus by 24 and 37% compared to untreated biocomposites at 20 wt% loading and neat LDPE, respectively. Reductions in the creep rate by 20 and 14% were observed for untreated and treated biocomposites, respectively, in comparison to the neat LDPE. H/E ratio was increased by 23 and 18% for treated and untreated biocomposites, respectively, as compared to virgin LDPE. Furthermore, mechanical and structural properties of untreated and treated RH are reported based on nanoindentation response and Fourier transform infrared spectroscopy (FTIR) techniques The study indicated that aqueous glycerol pretreatment can partially strip off non-cellulosic constituents from lignocellulose matrix to generate cellulose-rich pulp for engineered composite applications.

Fluorophore spectroscopy in aqueous glycerol solution: the interactions of glycerol with the fluorophore.

A common perception exists that glycerol provides an inert-like environment modifying viscosity and index of refraction by its various concentrations in aqueous solution. Said perception is herein challenged by investigating the effects of the glycerol environment on the spectroscopic properties of fluorescein, as a representative fluorophore, using steady-state and time-resolved techniques and computational chemistry. Results strongly suggest that the fluorescence quantum yield, measured fluorescence lifetime (FLT), natural lifetime and calculated fluorescence lifetime are all highly sensitive to the presence of glycerol. Glycerol was found to impact both the ground and first excited states of fluorescein, quenching and modifying both absorption and emission spectra, affecting the fundamental electrical dipoles of the ground and first excited singlet states, and lowering FLT and quantum yield. Furthermore, the Stern-Volmer, Lippert-Mataga, Perrin and Strickler-Berg relations indicate that glycerol acts upon fluorescein in aqueous solution as a quencher and alters the fluorescein geometry. Predictions made by computational chemistry impressively correspond to experimental results, both indicating changes in the properties of fluorescein at around 35% v/v aqueous glycerol, a clear indication that glycerol is not an innocent medium. This study proposes the Strickler-Berg relation as a means of detecting non-negligible effects of a hosting medium on its host fluorophore. These new insights on the molecular structures, the interactions between glycerol and its host fluorophore, and the effects of one on the other may be essential for understanding fundamental phenomena in chemistry and related fields.

Enhanced heat transport in thermal convection with suspensions of rod-like expandable particles

Thermal convection of fluid is a more efficient way than diffusion to carry heat from hot sources to cold places. Here, we experimentally study the Rayleigh–Bénard convection of aqueous glycerol solution in a cubic cell with suspensions of rod-like particles made of polydimethylsiloxane. The particles are inertial due to their large thermal expansion coefficient and finite sizes. The thermal expansion coefficient of the particles is three times larger than that of the background fluid. This contrast makes the suspended particles lighter than the local fluid in hot regions and heavier in cold regions. The heat transport is enhanced at relatively large Rayleigh number ( $\textit {Ra}$ ) but reduced at small $\textit {Ra}$ . We demonstrate that the increase of Nusselt number arises from the particle–boundary layer interactions: the particles act as ‘active’ mixers of the flow and temperature fields across the boundary layers.

Computing the Structural Dynamics of RVFV L Protein Domain in Aqueous Glycerol Solutions.

Many biological and biotechnological processes are controlled by protein–protein and protein–solvent interactions. In order to understand, predict, and optimize such processes, it is important to understand how solvents affect protein structure during protein–solvent interactions. In this study, all-atom molecular dynamics are used to investigate the structural dynamics and energetic properties of a C-terminal domain of the Rift Valley Fever Virus L protein solvated in glycerol and aqueous glycerol solutions in different concentrations by molecular weight. The Generalized Amber Force Field is modified by including restrained electrostatic potential atomic charges for the glycerol molecules. The peptide is considered in detail by monitoring properties like the root-mean-squared deviation, root-mean-squared fluctuation, radius of gyration, hydrodynamic radius, end-to-end distance, solvent-accessible surface area, intra-potential energy, and solvent–peptide interaction energies for hundreds of nanoseconds. Secondary structure analysis is also performed to examine the extent of conformational drift for the individual helices and sheets. We predict that the peptide helices and sheets are maintained only when the modeling strategy considers the solvent with lower glycerol concentration. We also find that the solvent-peptide becomes more cohesive with decreasing glycerol concentrations. The density and radial distribution function of glycerol solvent calculated when modeled with the modified atomic charges show a very good agreement with experimental results and other simulations at .

Photocatalytic production of hydrogen and methane from glycerol reforming over Pt/TiO2–Nb2O5

In this study, platinized mixed oxides (TiO2–Nb2O5) were tested on photocatalytic hydrogen production from a glycerol solution under UV light. Different samples with different Ti:Nb ratios were prepared by using a simple method that simultaneously combined a physical mixture and a platinum photochemical reduction. This method led to improved physicochemical properties such as low band gap, better Pt nanoparticle distribution on the surface, and the formation of different Pt species. Niobia content was also found to be an important factor in determining the overall efficiency of the Pt–TiO2–Nb2O5 photocatalyst in the glycerol reforming reaction. The photocatalytic results showed that Pt on TiO2–Nb2O5 enhanced hydrogen production from the aqueous glycerol solution at a 5 wt% initial glycerol concentration. The influence of different operating conditions such as the catalyst dosage and initial glycerol concentration was also evaluated. The results indicated that the best hydrogen and methane production was equal to 6657 μmol/L and 194 μmol/L, respectively after 4 h of UV radiation using Pt/Ti:Nb (1:2) sample and with 3 g/L of catalyst dosage. Moreover, the role of water in photocatalytic hydrogen production was studied through photocatalytic activity tests in the presence of D2O. The obtained results confirmed the role of water molecules on the photocatalytic production of hydrogen in an aqueous glycerol solution.

Nanoparticle de-agglomeration in viscous fluids using different high shear mixer geometries

In the present work, the effect of batch high shear mixer (HSM) geometries is studied on nanoparticles deagglomeration and power draw in water and aqueous glycerol solutions. The kinetics and mechanism of cluster break-up are investigated for disintegrated (less number of larger stator holes), and mesh (higher number of smaller stator holes) heads at different rotor speeds. Mesh head geometry is found to be more efficient for fines generation than disintegrated head. A bi-modal particle size distribution and erosion as dominant break-up mechanism is found. The size of the smallest fines is found to be ≈30 nm for mesh head and ≈50 nm for the disintegrated head. Z-average ranges from 180 to 310 nm for given operating and process conditions. The power draw is more in mesh head and increased with an increase in viscosity. Further, power draw increased with an increase in viscosity of continuous media and rotor speed.

OCT particle tracking velocimetry of biofluids in a microparallel plate strain induction chamber.

.Significance: Imaging biofluid flow under physiologic conditions aids in understanding disease processes and health complications. We present a method employing a microparallel plate strain induction chamber (MPPSIC) amenable to optical coherence tomography to track depth-resolved lateral displacement in fluids in real time while under constant and sinusoidal shear.Aim: Our objective is to track biofluid motion under shearing conditions found in the respiratory epithelium, first validating methods in Newtonian fluids and subsequently assessing the capability of motion-tracking in bronchial mucus.Approach: The motion of polystyrene microspheres in aqueous glycerol is tracked under constant and sinusoidal applied shear rates in the MPPSIC and is compared with theory. Then 1.5 wt. % bronchial mucus samples considered to be in a normal hydrated state are studied under sinusoidal shear rates of amplitudes 0.7 to .Results: Newtonian fluids under low Reynolds conditions () exhibit velocity decreases directly proportional to the distance from the plate driven at both constant and oscillating velocities, consistent with Navier–Stokes’s first and second problems at finite depths. A 1.5 wt. % mucus sample also exhibits a uniform shear strain profile.Conclusions: The MPPSIC provides a new capability for studying biofluids, such as mucus, to assess potentially non-linear or strain-rate-dependent properties in a regime that is relevant to the mucus layer in the lung epithelium.