Structural insight into [Fe–S2–Mo] motif in electrochemical reduction of N2 over Fe1-supported molecular MoS2

The catalytic synthesis of NH3 from the thermodynamically challenging N2 reduction reaction under mild conditions is currently a significant problem for scientists. Accordingly, herein, we report the development of a nitrogenase-inspired inorganic-based chalcogenide system for the efficient electrochemical conversion of N2 to NH3, which is comprised of the basic structure of [Fe–S2–Mo]. This material showed high activity of 8.7 mgNH3 mgFe−1 h−1 (24 μgNH3 cm−2 h−1) with an excellent faradaic efficiency of 27% for the conversion of N2 to NH3 in aqueous medium. It was demonstrated that the Fe1 single atom on [Fe–S2–Mo] under the optimal negative potential favors the reduction of N2 to NH3 over the competitive proton reduction to H2. Operando X-ray absorption and simulations combined with theoretical DFT calculations provided the first and important insights on the particular electron-mediating and catalytic roles of the [Fe–S2–Mo] motifs and Fe1, respectively, on this two-dimensional (2D) molecular layer slab

A New Approach to Steganography using Sinc-Convolution Method

Abstract—Both image steganography and image encryption have advantages and disadvantages. Steganograhy allows us to hide a desired image containing confidential information in a covered or host image while image encryption is decomposing the desired image to a non-readable, non-comprehended manner. The encryption methods are usually much more robust than the steganographic ones. However, they have a high visibility and would provoke the attackers easily since it usually is obvious from an encrypted image that something is hidden! The combination of steganography and encryption will cover both of their weaknesses and therefore, it increases the security. In this paper an image encryption method based on sinc-convolution along with using an encryption key of 128 bit length is introduced. Then, the encrypted image is covered by a host image using a modified version of JSteg steganography algorithm. This method could be applied to almost all image formats including TIF, BMP, GIF and JPEG. The experiment results show that our method is able to hide a desired image with high security and low visibility

Probing the Role of Water Chemistry on the Behavior of Clays in Process and Natural Environments Using Solution Calorimetry

Clays, due to their specific surface area and electrical charge density, are among the most active minerals in aquifers, oil and gas reservoirs, and tailings ponds. Important problems, such as limited yield of oil recovery during petroleum exploration, involve the interaction of process fluids with minerals which constitute reservoir pore walls. During mine tailings treatment and management, water chemistry impacts the aggregation and settling of clays. Solution calorimetry is a sensitive probe for species transfer to and from clay surfaces, and for the measurement of the effects of water chemistry (temperature, pH, salinity) on clay particle surfaces, in this case, kaolinite, illite, and montmorillonite. In this work, we show that interactions between clays and surrounding water are temperature-independent for all three clay types and that water chemistry has no measurable effect on the surface properties of illite. For kaolinite, water pH does impact surface properties and has a synergistic impact with salinity at high pH. The surface properties of montmorillonite are sensitive to water pH and salinity. These data and observations extend a solution enthalpy modeling framework for clays and contaminated clays in water and liquid hydrocarbons. In the next phases of this work, entropic effects will be addressed so that a quantitative Gibbs free energy modeling framework for the enthalpy of solution of clays can be constructed and linked to clay settlement kinetics

Development of a nano alumina-zirconia composite catalyst as an active thin film in biodiesel production

A Nano-alumina-zirconia composite catalyst was synthesized by a simple aqueous sol-gel method using AlCl3.6H2O and ZrCl4 as precursors. Thermal decomposition of the precursor and subsequent formation of γ-Al2O3 and t-ZrO2 were investigated by thermal analysis. XRD analysis showed that γ-Al2O3 and t-ZrO2 phases were formed at 700 °C. FT-IR analysis also indicated the phase transition to γ-Al2O3 occurred in corroboration with X-ray studies. TEM analysis of the calcined powder revealed that spherical particles were in the range of 8-12 nm. The nano alumina-zirconia composite particles were mesoporous and uniformly distributed in their crystalline phase. In order to measure the catalytic activity, esterification reaction was carried out. Biodiesel, as a renewable fuel, was formed in a continuous packed column reactor. Free fatty acid (FFA) was esterified with ethanol in a heterogeneous catalytic reactor. It was found that the synthesized γ-Al2O3/ZrO2 composite had the potential to be used as a heterogeneous base catalyst for biodiesel production processes

Probing the Impact of Asphaltene Contamination on Kaolinite and Illite Clay Behaviors in Water and Organic Solvents: A Calorimetric Study

A detailed understanding of the impacts of trace compounds and asphaltene adsorption on the behavior of clays contributes to the development of production processes for heavy oils and bitumen with lower environmental impacts, to the treatment of tailings from mined bitumen, and to the mitigation of impacts from oil spills in natural environments. Probes, such as solution calorimetry, are sensitive to species transfer to and from clay surfaces and outcomes can be interpreted unambiguously when supplemented with thermogravimetric analysis and scanning electron microscopy measurements. In this study, the effects of asphaltene coating on the enthalpy of solution of kaolinite and illite clays in toluene, <i>n</i>-heptane, and deionized water were investigated at 60 °C and atmospheric pressure. Asphaltene coating increases organic compound sorption but does not impact water sorption vis-à-vis uncoated clay particles or water displacement from clay particles by organic liquids as solvents or as trace contaminants in water. Experimental outcomes are interpreted using a quantitative mass and energy balance model framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Mechanistic and quantitative insights underlying the stability of asphaltene-coated clay dispersions in tailings ponds and the behaviors of these clays in diverse industrial and natural environments are discussed

Probing Contaminant Transport to and from Clay Surfaces in Organic Solvents and Water Using Solution Calorimetry

Clays, in tailings, are a significant ongoing environmental concern in the mining and oilsands production industries, and clay rehabilitation following contamination poses challenges episodically. Understanding the fundamentals of clay behavior can lead to better environmental impact mitigation strategies. Systematic calorimetric measurements are shown to provide a framework for parsing the synergistic and antagonistic impacts of trace (i.e., parts per million level) components on the surface compositions of clays. The enthalpy of solution of as-received and “contaminated” clays, in as-received and “contaminated” organic solvents and water, at 60 °C and atmospheric pressure, provides important illustrative examples. Clay contamination included pre-saturation of clays with water and organic liquids. Solvent contamination included the addition of trace water to organic solvents and trace organic liquids to water. Enthalpy of solution outcomes are interpreted using a quantitative mass and energy balance modeling framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Underlying surface energies are shown to dominate the energetics of the solvent–clay interaction, and organic liquids as solvents or as trace contaminants are shown to displace water from as-received clay surfaces. This approach can be readily extended to include pH, salts, or other effects and is expected to provide mechanistic and quantitative insights underlying the stability of clays in tailings ponds and the behaviors of clays in diverse industrial and natural environments

Development of a nano alumina-zirconia composite catalyst as an active thin film in biodiesel production

578-582A nano-alumina-zirconia composite catalyst has been synthesized by a simple aqueous sol-gel method using AlCl3.6H2O and ZrCl4 as precursors. Thermal decomposition of the precursor and subsequent formation of γ-Al2O3 and t-ZrO2 have been investigated by thermal analysis. XRD analysis show that γ-Al2O3 and t-ZrO2 phases are formed at 700 °C. FT-IR analysis also indicate the phase transition to γ-Al2O3 occur in corroboration with X-ray studies. TEM analysis of the calcined powder reveal that spherical particles were in the range of 8-12 nm. The nano alumina-zirconia composite particles are mesoporous and uniformly distributed in their crystalline phase. In order to measure the catalytic activity, esterification reaction has been carried out. Biodiesel, as a renewable fuel, is formed in a continuous packed column reactor. Free fatty acid (FFA) is esterified with ethanol in a heterogeneous catalytic reactor. It is found that the synthesized γ-Al2O3/ZrO2 composite has the potential to be used as a heterogeneous base catalyst for biodiesel production processes

Development of a nano alumina-zirconia composite catalyst as an active thin film in biodiesel production

578-582A nano-alumina-zirconia composite catalyst has been synthesized by a simple aqueous sol-gel method using AlCl3.6H2O and ZrCl4 as precursors. Thermal decomposition of the precursor and subsequent formation of γ-Al2O3 and t-ZrO2 have been investigated by thermal analysis. XRD analysis show that γ-Al2O3 and t-ZrO2 phases are formed at 700 °C. FT-IR analysis also indicate the phase transition to γ-Al2O3 occur in corroboration with X-ray studies. TEM analysis of the calcined powder reveal that spherical particles were in the range of 8-12 nm. The nano alumina-zirconia composite particles are mesoporous and uniformly distributed in their crystalline phase. In order to measure the catalytic activity, esterification reaction has been carried out. Biodiesel, as a renewable fuel, is formed in a continuous packed column reactor. Free fatty acid (FFA) is esterified with ethanol in a heterogeneous catalytic reactor. It is found that the synthesized γ-Al2O3/ZrO2 composite has the potential to be used as a heterogeneous base catalyst for biodiesel production processes