New insights on the theoretical study of hydrolysis mechanism of carbon disulfide (CS2) at low temperature: A density functional theory study

Density functional theory (DFT) is used to investigate the two-step hydrolysis mechanism of CS2. By optimizing the structure of reactants, intermediates, transition states, and products, the conclusion shows that the first step of CS2 (CS2 reacts with H2O first to form COS intermediate); The second step (COS intermediate reacts with H2O to form H2S and CO2). Therefore, hydrogen migration is crucial to the mechanism of CS2 hydrolysis. In the first step of the reaction, the rate-determining step in both the single C=S path and the double C=S path has a higher barrier of 199.9 kJ/mol, but the 127.9 kJ/mol barrier in the double C=S path has a lower barrier of 142.8 kJ/mol in the single C=S path. So the double C=S path is better. Similarly, the order of the barriers for the three paths in the second reaction is C=S path < C=S path and C=O path < C=O path. So the C=S path is better. Also, to further explore the reaction of CS2 hydrolysis, the natural bond orbital (NBO) analysis of the transition states was carried out. Besides, to further explain which reaction path is better, the hydrolysis kinetics of CS2 was analyzed. It was found that the hydrolysis of CS2 was an exothermic reaction, and the increase in temperature was unfavorable to the reaction. During the hydrolysis of CS2, the six reaction paths are parallel and competitive. The results will provide a new way to study the catalytic hydrolysis of CS2.

Mild Hydrothermal Synthesis of 11Å-TA from Alumina Extracted Coal Fly Ash and Its Application in Water Adsorption of Heavy Metal Ions (Cu(II) and Pb(II))

Non-biodegradable copper (Cu) and lead (Pb) contaminants in water are highly toxic and have series adverse effects. Therefore, it is very important to extract heavy metals from wastewater before it is discharged into the environment. Adsorption is a cost-effective alternative method for wastewater treatment. Choosing a low-cost adsorbent can help reduce the cost of adsorption. In this study, conversion of reside after extracting aluminum (REA) produced by sub-molten salt method transform high-alumina coal fly ash (CFA) into 11Å-tobermorite to adsorb Cu(II) and Pb(II) from aqueous solutions at room temperature. The synthesis of the adsorbent was confirmed using scanning electron microscope (SEM), X-ray diffractometer (XRD) and Brunauer–Emmett–Teller (BET) method surface analysis. To study the adsorption characteristics, factors such as initial Cu(II) and Pb(II) concentration, pH, contact time, adsorption characteristics and temperature were investigated in batch mode. The maximum adsorption capacity of Cu(II) and Pb(II) was 177.1 mg·g−1 and 176.2 mg·g−1, respectively. The Langmuir adsorption model was employed to better describe the isothermal adsorption behavior and confirm the monolayer adsorption phenomenon. The pseudo-second-order kinetic model was used to highlight Cu(II) and Pb(II) adsorption kinetics. Thermodynamic analysis indicated the removal Cu(II) and Pb(II) by TA-adsorbent was a nonspontaneous and exothermic reaction. The obtained results are of great significance to the conversion of industrial waste to low-cost adsorbent for Cu(II) and Pb(II) removal from water.

A Disposable DNA Analysis Chip with a Powerless Actuator

A non-instrumented, single-use, affordable, and fully- yet safely-disposable DNA analysis system for Point Of Care (POC) diagnostic process has been proposed by integrating (1) a hydration-reactive mixture for a portable heating element as a powerless actuator, (2) commercially available optical adhesive films as valves, and (3) an exothermic reaction-based recombinant polymerase amplification (RPA) process for non-instrumented DNA amplification. The operational error tolerance of the adhesive valves was evaluated by gas production and long-lasting ability, and the amplification performance of the RPA device was validated by gel electrophoresis. Finally, a DNA analysis device was fabricated and tested based on a hydration reaction with a DNA extraction microfluidic channel and an exothermic reaction-based RPA device. In the DNA extraction process, dimethyl adipimidate (DMA) solution was used to eliminate some required injection steps from the extraction process. The integrated system's functionality was successfully demonstrated, and the suggested system could become a foundation for the ultimate total solution for POC DNA analysis.

INVESTIGATION OF THE NEUTRALIZATION PROCESS OF SULFATION PRODUCTS IN THE SURFACTANTS PRODUCTION

The process of sulfation products neutralization in the production of surfactants is not basic, but at this stage the positive effects obtained at the stage of sulfation of organic matter with sulfur trioxide gas are fixed. To preserve the degree of sulfation obtained, it is necessary to carry out the neutralization process under conditions precluding the occurrence of hydrolysis in an acidic medium. The neutralization reaction takes place with a high heat release of about 40 kJ / mol. Analysis of the literature data showed that the neutralization process is not well covered. Little data and hardware and technological design of the process. The process of neutralization in industrial conditions is carried out in apparatus with mechanical turbine mixers, to remove the heat of the exothermic reaction, the paste from the neutralizer is fed into a water-borne heat exchanger and returns to the neutralizer again. The purpose of this study is to determine the optimal technological parameters of the process of neutralization of sulfate products and the development of a mathematical model of this process. The results of experimental studies of the process of sulfation products neutralization with an aqueous solution of sodium hydroxide are presented. During the research, the influence of technological parameters on the quality indicators of neutralization products was determined, the main of which is the degree of sulfation. The optimal technological parameters for carrying out this process in a reactor with a stirrer under laboratory conditions were found. Based on the data obtained in the basis of this process, the use of a continuous-action reactor with a turbine mixer and with a combined heat exchanger. For the transition to an industrial reactor-neutralizer, a mathematical model has been developed, which makes it possible, by means of mathematical modeling, to correct technological parameters in industrial conditions.

Porosity Effect of the Silver Catalyst in Hydrogen Peroxide Monopropellant Thruster

In monopropellant system, hydrogen peroxide is used with catalyst to create an exothermic reaction. Catalyst made of silver among the popular choice for this application. Since the catalyst used is in porous state, the effect of its porosity in the hydrogen peroxide monopropellant thruster performances is yet unknown. The porosity changes depending on factors including catalyst pact compaction pressure, bed dimension, and type of catalyst used. As researches on this topic is relatively small, the optimum porosity value is usually left out. The performance of the thruster indicated by the pressure drop across the catalyst bed. Porosity of the catalyst bed adds additional momentum sink to the momentum equation that contributes to the pressure gradient which lead to pressure loss inside thruster. The effect of porosity influences the performance and precision of the thruster. Study of the pressure drop by the catalyst bed requires a lengthy period and expensive experiments, however, numerical simulation by mean of Computational Fluid Dynamics (CFD) can be an alternative. In this paper, 90 wt% hydrogen peroxide solution with silver catalyst is studied in order to investigate the influence of porosity to the performances of the thruster, and to find the optimum porosity of the thruster. Species transport model is applied in the single-phase reaction simulation using the EDM for turbulence-chemistry interaction. Through this study, the effect of porosity towards the thruster performances represented in term of pressure drop, exit velocity, bed temperature, and thrust, and porosity of 0.4 found to be as an optimal value.

Improve Oil Production From Tar-Impacted Reservoirs Using In-Situ Steam Generation and Ionic Liquids

One of the typical production challenges is occurrence of impermeable layers of highly viscous asphaltenic oil (known as tarmat) at oil/water contact within a reservoir. Tar forms a physical barrier that isolates producing zones from aquifer or water injectors. As a result of tar occurrence, is a rapid pressure decrease that can be observed in such reservoirs, increasing number of dead wells, and declining productivity. Another indirect consequence of Tar presence is poor sweep efficiency that leads to water cut increase by a drastic magnitude. An innovative approach was developed to establish better sweep efficiency, transmissibility and pressure maintenance of Tar impacted-areas using thermochemical treatment. The treatment consists of injecting exothermic reaction-components that react downhole and generate in-situ pressure and heat. The in-situ reaction products provide heat and gas-drive energy to mobilize tar, improve sweep efficiency and maintain flooding for better pressure maintenance. Typically, downhole heat generation through chemical reaction releases substantial heat which could be employed in various thermal stimulation operations. Nano/ionic liquids, high pH solutions, solvents and nano metals were combined with the exothermic reaction to improve tar mobilization. Based on lab testing, the new technology showed more recovery than conventional steam flooding. Permeable channels were created in a tar layer with sandback samples, which enhanced transmissibility, pressure support and sweep efficiency. The effect of thermochemical treatment and ionic liquid on bitumen texture will be described. Impact of In-situ generated heat on injectivity will also be presented. The novel method will enable commercial production from tar-impacted reservoirs, and avoid costly steam flooding systems. The developed novel treatment relates to in-situ steam generation to maximize heat delivery efficiency of steam into the reservoir and to minimize heat losses due to under and/or over burdens. The generated in-situ steam and gas can be applied to recover deep oil reservoirs, which cannot be recovered with traditional steam, miscible gas, nor polymer injection methods.

Analyzing the Cooling Rate and Its Effect on Distribution of Pattern and Size of the Titanium Diboride Particles Formed

In this work, we synthesize Al/TiB2 metal matrix composites (MMC) based on the effect of cooling rate in the melt while pouring into the permanent mold condition. The objective of this paper is to achieve the desired distribution pattern and increased TiB2 particles’ size in the Al/TiB2 MMC ingot. Two halide salts, viz., potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4), are procured and measured. The two salts were mixed with the aluminium melt in the crucible, and it is stirred manually with help of a graphite rod. Because of the exothermic reaction, the melt reacts very quickly and that is what dropped the salts slowly. The salt particles were synthesized because of the exothermic reaction, and it will allow the particles to grow. The size and distribution of particles differ at different place in the MMC. An FEA tool ProCAST was used to analyze the cooling rate of the melt, and SEM is used to study the microstructure of the ingot at different places. The microstructures helped to identify the size of reinforcement in the MMC. The TiB2 particles are distributed more at this location at 810°C, and the TiB2 particles formed various clusters in this zone as 70%–80%. Also, the tribological characteristics are analyzed with the help of the results.

Core Scale FEM Modeling of Thermochemical Fracturing on Cement Cube Samples

Brownfields and depleting conventional resources of fossil fuel energy are not enough to fulfill the tremendously increasing energy demands around the globe. Unconventional oil and gas resources are creating a huge impact on the enhancement of the global economy. Tight rocks are usually located in deep and high-strength formations. In this study, numerical simulation results on a new thermochemical fracturing approach is presented. The new fracturing approach was implemented to reduce the breakdown pressure of the unconventional tight formations. The hydraulic fracturing experiments presented in this study were carried out on ultra-tight cement block samples. The permeability of the block samples was less than 0.005mD. Thermochemical fracturing was carried out by a thermochemical fluids that caused a rapid exothermic reaction which resulted in the instantaneous generation of heat and pressure. Different salts of nitrogen such as sodium nitrite and ammonium chloride were used as a thermochemical fluid. The instantaneous generation of the heat and pressure caused the creation of micro-cracks. The fracturing results revealed that the novel thermochemical fracturing was able to reduce the breakdown pressure in ultra-tight cement from 1095 psi to 705 psi. The reference breakdown pressure was recorded from the conventional fracturing technique. A finite element (FEM) analysis was conducted using commercial software ABAQUS. In FEM, two approaches were used to model the thermochemical fractures namely, cohesive zone modeling (CZM) and concrete damage plasticity models (CDP). The sensitivity analysis of peak pressure and time to reach the peak pressure is also presented in this study. The sensitivity analysis can help in better designing thermochemical fluids that could lead to the maximum generation of micro-cracks and multiple fractures.

Alcohol Assisted Solution-Combustion Technique for the Synthesis of Phase-Pure BaSnO3 Nanoparticles at 130 °C

Lowering the synthesis temperature to obtain phase pure BaSnO3, which is the host material for high figure-of-merit (FOM) perovskite transparent conductors (TCs), can expand the horizons for its optoelectronic applications, with an obvious reduction in the thermal budget. In this work, we have developed a novel solution combustion technique for the synthesis of BaSnO3 nanoparticles. A peroxo/superoxo precursor to the nanoparticles is first synthesized by co-precipitation of the tin and barium salts via the H2O2 assisted or the `CSMC' route. The phase evolution, under different drying conditions of the wet precursor to crystalline BaSnO3 nanoparticles is then studied. We find that the crystallization temperature of BaSnO3 is significantly reduced by adding an organic solvent such as ethanol or propanol to the precursor; temperatures as low as 130 °C yield phase pure BaSnO3 nanoparticles. We establish that the organic solvent increases the reactive O2 ligand content, which plays a pivotal role in the synthesis. Due to this, an exothermic reaction occurs around 130 °C, thereby providing the heat of reaction for conversion of the precursor to phase-pure BaSnO3. Importantly, this method should also allow for the facile incorporation of dopants, paving the way for synthesis of high FOM TCs at low temperatures. Such low synthesis temperatures enable BaSnO3 to be used in devices having temperature limitations during device processing, such as heterojunction Si solar cells or perovskite-based solar cells in an n-i-p architecture.

Chemical properties of complex aluminum ions

The objective of this research work was to study the synthesis of metallic salts and to analyze their properties. For this purpose, tests were carried out using basic and acid solutions. These tests allowed to identify that the reaction of aluminum in the presence of sulfuric acid is an exothermic reaction whose first stage is the formation of the tetrahydroxoaluminate (III) ion complex, a process in which a significant amount of heat is released from the system and a large amount of hydrogen gas for the oxidation of aluminum, a second stage in which sulfuric acid was added to neutralize the basicity of the solution transforming the complex into disulfate-aluminate (III), Then a third stage consisted in subjecting the solution in an ice bath to decrease the solubility of the complex and the formation of whitish crystals and finally the removal of excess crystals by washing with ethanol, these tests revealed the importance of excess sulfuric acid in the stabilization of the aluminate ion and the ease of the complex ion to bind to water molecules, thus determining important properties of the reaction as the type, orientation, solubility and the intermediates affected by the metal catalysis.