Alexander Badalyan

Oxidation of aldehydes using silica-supported Co(II)-substituted heteropolyacid

A supported Co(II)-substituted heteropolyacid salt, Cs6H2P2W17O61Co·OH2, on silica was prepared and characterized by BET surface area measurements, thermal analysis (TGA/DTA) and infrared spectroscopy. The infrared spectroscopy and thermal analysis revealed that the supported heteropolyacid salt preserves Wells-Dawson structure and is stable upto 500 ◦ C. The BET result shows that by supporting the above heteropolyacid salt on silica, surface area increases. The supported heteropolyacid was used as a heterogeneous catalyst for the oxidation of aldehydes to corresponding carboxylic acids with molecular oxygen. Silica-supported heteropolyacid is an effective catalyst for the oxidation of aldehydes to carboxylic acids.

Particle mobilization in porous media: temperature effects on competing electrostatic and drag forces

The fluid flow in natural reservoirs mobilizes fine particles. Subsequent migration and straining of the mobilized particles in rocks greatly reduce reservoir permeability and well productivity. This chain of events typically occurs over the temperature ranges of 20-40 degrees C for aquifers and 120-300 degrees C for geothermal reservoirs. However, the present study might be the first to present a quantitative analysis of temperature effects on the forces exerted on particles and of the resultant fines migration. Based on torque balance between electrostatic and drag forces acting on attached fine particles, we derived a model for the maximum retention concentration and used it to characterize the detachment of multisized particles from rock surfaces. Results showed that electrostatic force is far more affected than water viscosity by temperature variation. An analytical model for flow toward wellbore that is subject to fines migration was derived. The experiment-based predictive modeling of the well impedance for a field case showed high agreement with field historical data (coefficient of determination R-2=0.99). It was found that the geothermal reservoirs are more susceptible to fine particle migration than are conventional oilfields and aquifers.

Development of an automated gas adsorption apparatus for the characterization of the surface area, pore size distribution, and density of powdered materials

An automated apparatus for the characterization of the surface area, pore size distribution, and density of powdered materials is described. A newly developed liquid nitrogen level control system maintains the nitrogen level around the tube containing the sample within ±0.2 mm of the initial predefined level. The dosing volume and pneumatically operated control valves are maintained at 25.00±0.05 °C. Equilibrium pressure is measured with the accuracy of ±0.05% of reading. The apparatus may be operated either in a manual or an automatic mode. The control software developed, using the VISIDAQ Version 3.11 software package, operates involving equilibrium and barometric pressure measurements, opening and closing pneumatically operated valves, and transferring experimental data to MS EXCEL spreadsheets. The subroutines developed within the spreadsheet program plot the adsorption and desorption isotherms, calculate the sample specific surface area and density, and provide αs- and t-plots and mesopore and microp...

Size-Exclusion Colloidal Transport in Porous Media--Stochastic Modeling and Experimental Study

Suspension, colloidal, and emulsion flow in rocks with particle size-exclusion may have a strong effect on the reservoir and on the well behavior during fines migration and production, drilling-fluid invasion into oil- or gas-bearing formations, or injection of seawater or produced water. The stochastic microscale equations for size-exclusion colloidal transport in porous media (PM) are derived. The proposed model includes the following new features: It accounts for the accessible flux in the expression for capture rate, it accounts for the increase of inlet concentration caused by the injected particles entering only the accessible area, and it accounts for the dilution of effluent accessible flux in the overall flux of the produced suspension.

Analysis of uncertainties in manometric gas-adsorption measurements II. Uncertainty in αs-analyses and pore volumes

We describe procedures to propagate the uncertainty in adsorption data and alpha(S)-values to generate uncertainty in apparent primary, secondary, and total micropore volumes for porous activated carbons exhibiting Type I and IV character. The alpha(S)-data are interpolated from selected non-porous reference material (NPRM) adsorption isotherm data with some adsorbents exhibiting surface chemistry quite different from and some similar to that of the porous adsorbents (PA). We show that a statistically constant apparent total micropore volume can be determined independent of the NPRM surface chemistry. In contrast, NPRM surface chemistry appears to influence our ability to identify unequivocally the filling and condensation ranges of micropore filling, leading to statistically different apparent primary and secondary micropore volumes.

Influence of broth dilution on the disruption of Escherichia coli

The effect of cell concentration (5 to 150 g/L wet wt after broth dilution) on homogenizer disruption efficiency and homogenate viscosity is reported for E. coli. Broth dilution increases homogenizer efficiency and decreases feed and homogenate viscosity. However, this increase in disruption efficiency is not sufficient to warrant dilution of the broth prior to homogenization. The optimal feed concentration is the maximum possible that does not lead to practical handling difficulties due to high viscosity.

Size exclusion deep bed filtration: Experimental and modelling uncertainties

A detailed uncertainty analysis associated with carboxyl-modified latex particle capture in glass bead-formed porous media enabled verification of the two theoretical stochastic models for prediction of particle retention due to size exclusion. At the beginning of this analysis it is established that size exclusion is a dominant particle capture mechanism in the present study: calculated significant repulsive Derjaguin-Landau-Verwey-Overbeek potential between latex particles and glass beads is an indication of their mutual repulsion, thus, fulfilling the necessary condition for size exclusion. Applying linear uncertainty propagation method in the form of truncated Taylors series expansion, combined standard uncertainties (CSUs) in normalised suspended particle concentrations are calculated using CSUs in experimentally determined parameters such as: an inlet volumetric flowrate of suspension, particle number in suspensions, particle concentrations in inlet and outlet streams, particle and pore throat size distributions. Weathering of glass beads in high alkaline solutions does not appreciably change particle size distribution, and, therefore, is not considered as an additional contributor to the weighted mean particle radius and corresponded weighted mean standard deviation. Weighted mean particle radius and LogNormal mean pore throat radius are characterised by the highest CSUs among all experimental parameters translating to high CSU in the jamming ratio factor (dimensionless particle size). Normalised suspended particle concentrations calculated via two theoretical models are characterised by higher CSUs than those for experimental data. The model accounting the fraction of inaccessible flow as a function of latex particle radius excellently predicts normalised suspended particle concentrations for the whole range of jamming ratios. The presented uncertainty analysis can be also used for comparison of intra- and inter-laboratory particle size exclusion data.

Effects of surface functional groups of activated carbon on adsorption of triclosan from aqueous solution

We report adsorption of triclosan by using activated carbons as a potential method to improve the discharge water purification process. Commercially available activated carbons, P1300, Picazine HP and Hydrodarco C, display different levels of affinity for triclosan from aqueous solution. Surface chemistry of these adsorbents were modified via reduction, oxidation and nitridation, to improve and better understand the adsorption process. The adsorption capacity was greatly influenced by surface group changes, with a decrease in relative affinity on oxidation. Nitridation enhanced the amounts adsorbed over the thermally reduced samples. Surface analysis via X-ray Photoelectron Spectroscopy (XPS) helped us identify the introduced surface functional group changes. Overall, nitridation resulted in an increased basic character of the surface exploiting the Lewis acidic nature of triclosan when it is dissolved in solution. The surface chemistry modified adsorbents suggest that adsorption from solution is a viable methodology for triclosan control during wastewater treatment.

Investigation of the Preyssler phosphotungstate heteropolyanion, [NaP5W30O110]14−, properties with different counter ions

Preyssler heteropolytungstophosphate anions with different counter ions, XxMy[NaP5W30O110], where X = H and M = Cs, Ba, La, Ce, Hg, Tl, Pb and Bi, were prepared and the effect of the counter ion on their behavior was investigated by i.r. spectroscopy, surface area measurements (BET), simultaneous thermal analysis (STA), cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Thermal analyses indicate that the Ce derivative has the highest and the Hg derivative the lowest thermal stability. Only the Cs, Ba and Tl salts show measurable surface area. All heteropolyanions with similar i.r. spectra and electrochemical behavior demonstrate that the heteropolyanion structures are retained. The X-ray photoelectron spectra of the heteropolyacid salts reveal high binding energies for counter ions in comparison with classic salts and strong interaction of counter ion with the oxo oxygens for H+ and Cs+ derivatives.

Stimulation of Unconventional Naturally Fractured Reservoirs by Graded Proppant Injection: Experimental Study and Mathematical Model

The coal permeability declines due to fracture closure during the production and pressure depletion. The recently proposed technique for stimulation of natural coal cleats consists of the injection of microsized high-strength particles into a coal natural fractured system below the fracturing pressure. Coupling this technique with hydraulic fracturing treatment resulted in particles entering cleats under leal-off condition. In the current paper it is shown that the particles must be deposited at specific conditions of the particle-coal repulsion, ensuring the absence of external cake formation. The new method was successfully validated through laboratory injection of microsized glass particles into fractured coal cores. Application of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory resulted in determination of experimental conditions favourable for particle-particle and particle-coal repulsion; these conditions also immobilize the natural fines. At these conditions, no particle attachment to coal surface and no particle agglomeration were observed, thus the conditions exclude formation damage due to external cake formation, particle attraction to coal rock and fines migration. The previously developed mathematical model was used for determination of the duration of particle injection into a coal core at minimum effective stress. Particle placement resulted in almost three-time increase in coal permeability, thus confirming the mathematical model used. The curve for well productivity index-vs-stimulation zone radius reaches maximum at some critical value of stimulation radius; the maximum is determined by the mathematical model. Placing particles beyond this critical radius results in reduction of well productivity index, due to significant hydraulic losses experienced by suspension flowing through narrowing cleat apertures during production stage. Applying the proposed novel technology during hydraulic fracturing treatment leads to improvement in productivity of coal seam gas wells and other unconventional resources (shales, tight gas and geothermal reservoirs) through enhancement of interConnectivity among microfractures around the hydraulically induced fractures.