Influence Of Water Addition Research Articles

Investigation on the effect of water addition on benzene oxidation over palladium-oxide nanoparticle via ReaxFF molecular dynamics

Additives in the benzene oxidation process will have a greater impact. The oxidation processes of benzene (C6H6) with water addition are studied by reactive force field molecular dynamics (ReaxFF MD). The possible reaction pathways of C6H6 and the effect of water addition at 2000 K are discussed. The influence of water addition is investigated, the results show that the types of product are basically the same no matter with or without the water addition. But the addition of water will cause the increase of hydroxyl groups, occupying the active sites that should belong to the oxygen group, thus inhibits the oxidation of C6H6. And the hydroxyl group mainly affects the benzene oxidation process by affecting the oxidation of the carbon components in benzene, but has little effect on the dehydrogenation of benzene. This may be helpful to understand the water inhibition during the oxidation process that found in the experiments.

Chemical effect of water addition on the ammonia combustion reaction

• Influence of water addition on ammonia combustion reaction are studied via ReaxFF; • Water addition is shown to promote the overall ammonia oxidation; • H 2 O enhances the conversion between NO and HNO at the middle stage of oxidation; • The number of NOx molecules decreases with reduction of O 2 concentration in O 2 /H 2 O environment. Ammonia has become an emerging fuel. However, its combustion product NOx is polluting, and it is necessary to explore its conversion process. To determine the effect of water addition on ammonia oxidation and NOx, reaction molecular dynamics simulations are performed to study the chemical reactions of ammonia. Ammonia oxidation is studied in O 2 /N 2 and O 2 /H 2 O environments in a determining density and O 2 /NH 3 ratio equal under high temperature conditions. This work focuses on the initial reaction path of ammonia combustion established through chemical trajectory analysis. The ammonia oxidation behavior, the distribution of the main products, and the corresponding time evolution behavior on the atomic scale are also studied. Finally, the interconversion processes of molecules containing N elements in the ammonia oxidation products are analyzed. Results show that when N 2 molecules are replaced by H 2 O molecules, the formation of HNO increases with the net flux of the reactions: N H + O H → H 2 N O , H 2 N O → H + H N O . We also investigate the effect of different O 2 concentrations. An increase of NO and HNO molecules with O 2 concentration mainly from the reactions: O 2 + H → O + O H , H 3 N O + O H → H 2 N O + H 2 O , H 2 N O → H + H N O and H N O + O H → H 2 O + N O . In addition, the conversion affected by water addition between NO and HNO occurs mainly in the middle time of the oxidation, and H 2 O enhances the severity of the oxidation with the number of OH radicals. Water addition provides a new way to control NOx emissions in ammonia combustion, that is, converting it into other H-containing compounds.

Thermal decomposition and evaluation thermokinetic parameters for explosive type

In Taiwan, due to intensive religious ceremonial activities, the flying and pyrotechnic fireworks of firecrackers are commonly used. In the course of the activities, the use of water as a cooling measure has been pointed out in the past literature that it may cause pyrotechnic materials to deteriorate and reduce their thermal stability. To determine the possible influence of water addition on pyrotechnic deterioration, this study estimates the degree of thermal hazard of pyrotechnic based on the analysis of heat release, reaction kinetics, and the heat exchange model of pyrotechnic deterioration. The explosion sound (ES) firecracker was used to analyze the thermal hazard and mixed water (ES + W) to simulate the dampness condition using differential scanning calorimetry. Thermodynamic equations simulating thermal hazard safety parameters, combined with thermokinetic and thermal runaway data results, were used to discuss the safety and potential thermal hazard characteristics of ES, as the safety of fireworks in storage, transportation, process conditions, and operation assessment to curtail the probability of accidents. The results showed that if the initial exothermic temperature of ES + W is higher than ES, a thermal decomposition reaction will occur at a lower temperature, and the exothermic heat rises and the apparent activation energy decreases, indicating that the ES will increase its instability after being damp. The presence of water degenerated the ES and resulted in a violent reaction during the release process to explode the ES, which increased the chance of accidents among the onlookers.

Influence of Water Addition on the Latent Heat Degradation of Sodium Acetate Trihydrate

To promote the development of thermal energy storage (TES), the sodium acetate trihydrate (SAT) presents interesting thermal properties. However, this material may suffer from aging throughout thermal cycles. Various solutions were explored in the literature to limit this aging, mainly based on the use of additives such as water. In this study, two samples were prepared. The first one consisted of raw SAT material whereas 3 wt.% of supplementary water has been added to the second one. They were then poured into 350 cm3 bricks, which were placed in an experimental test bench. After 35 cycles between 20 and 70 °C, a drop of about 10% of the latent heat was observed for the first sample. This behavior was like the literature data. For the second sample, the decrease of latent heat was more rapid (about 30%). Contrary to our expectations, the water addition seems not beneficial for the improvement of thermal stability. Interestingly, we noticed that the drop of the latent heat was fully reversible after sample stirring. This degradation might not be related to a thermal destructive mechanism but rather to a global segregation phenomenon. This segregation may be due to the breaking of hydrogen bonding between anhydrous sodium acetate and water, resulting in the separation of the two species.

Influence of water addition on MILD ammonia combustion performances and emissions

The global energy shift towards the exploitation of Renewable Energy Sources requires the development of proper energy storage and back-up technologies to deal with their intermittency and seasonality. Renewable Energy chemical storage offers the possibility of efficiently storing large amounts of energy for long time. On the other hand, ammonia is increasingly considered a feasible alternative to the use of hydrogen, due to the existence of already well assessed production technologies and transport infrastructures. However, the exploitation of ammonia as an energy carrier poses some relevant challenges. The most relevant ones concern combustion stability and NOx emissions, when ammonia is burned in traditional conditions. A promising approach to ensure combustion stability while containing NOx emissions relies on the shift from traditional to new combustion modes. MILD Combustion has been proven as a reliable alternative to reach these targets. At the same time, water addition to reactants is a well-known strategy that promote DeNOx routes in fossil fuel combustion.In this work, combustion of ammonia-air mixtures assisted by water is studied in a cyclonic burner exercised under MILD operative conditions, to evaluate the effect of water addition on NOx emissions and process stability. The analyses were carried out in premixed and non-premixed feeding conditions.Results highlighted that water addition to the reactant mixture may represent a very simple and efficient solution in determining the reduction of NOx emissions in ammonia combustion, especially in fuel-lean conditions.Moreover, the comparison between premixed and non-premixed configuration shows that it is possible to enhance the process performance through a simultaneous optimization of the burner internal flow-field and reactants injection strategies.

Hydrogen and/or syngas production through combined dry and steam reforming of biogas in a membrane reactor: A thermodynamic study

The possibility of valorizing biogas by producing pure H2 and/or syngas while minimizing the net CO2 emissions was analyzed, combining both dry and steam reforming of biogas. For this purpose, a multifunctional membrane reactor (MR) with a hydrogen permselective membrane was used. The MR, which allows obtaining ultra-pure hydrogen in the permeate side, is compared with a conventional reactor (CR). All analyses were performed from thermodynamic equilibrium calculations based on the Gibbs free energy minimization method. The temperature was varied up to 800 °C and 550 °C for the CR and the MR, respectively. The influence of water addition in the feed on the productivity of hydrogen and CO2 reduction was assessed as well. Results showed that the CR is more suitable to obtain syngas with high purity (only CO and H2) because it allows operating at very high temperatures. The syngas H2/CO ratio can be adjusted for further applications depending on the co-fed amount of water. However, in the permeate side of the MR high-purity hydrogen with a productivity of 73 mol per 100 mol of biogas fed can be obtained. This productivity is equivalent to an H2 production of 131 kg/h, assuming the biogas generation capacity of an existing landfill plant; still, by CO2 recycling, net CO2 emission can be reduced up to 50%.

Influence of Water Addition on Lipid Oxidation in Protein Oleogels

The aim of the present study is the investigation of lipid oxidation in protein based oleogels. For this purpose, oleogels are prepared by suspension of freeze dried whey protein isolate aggregates and small amounts of water (<10%) in purified oleic rich safflower oil. The formation of conjugated dienes positively correlates with the addition of water. In contrast, a lower concentration of aldehydes is measured by headspace gas chromatography in oleogels with higher water addition, indicating a water facilitated degradation of aldehydes reacting with proteins. Determination of water activity indicates the presence of water droplets at higher water addition to oleogels. Furthermore, changes in the surface appearance (greasy‐glossy to dull) and the texture (consistent gel vs. crumbly) structure are indicative of microstructural changes due to increased water addition. The study suggests that water droplet formation is responsible for the marked increase in lipid oxidation. However, cross reaction of aldehydes with proteins is suggested to result in lowering the levels of secondary lipid oxidation products hexanal and propanal in oleogel.Practical Applications: The practical applications of the present work are related to the fabrication, processing, storage and consumption of oleogels and other protein‐lipid‐matrices. The results clearly indicate oleogels are prone to oxidation and proteins are involved by cross‐reaction resulting in visible browning during storage. Oxidation products such as hexanal (marker for secondary lipid oxidation) may not reflect the level of oxidation due to degradation by cross‐reactions with proteins.The aim of the present study is the investigation of lipid oxidation in protein based oleogels. The formation of conjugated dienes positively correlates with the addition of water. In contrast, a lower concentration of aldehydes is measured in oleogels with higher water addition. Water activity indicates the presence of water droplets at higher water addition to oleogels, which are likely responsible for the marked increase in lipid oxidation. However, cross reaction of aldehydes with proteins is suggested to result in lowering the levels of secondary lipid oxidation products hexanal and propanal in oleogels.

Influence of water addition on the modification of polyethylene surface by nitrogen atmospheric pressure plasma jet

ABSTRACTPolyethylene (PE) has many excellent material properties (low density, high flexibility, good chemical resistance, etc.), and is widely used in industrial and medical fields. However, the practical applications of PE are sometimes limited due to its poor wettability. In this article, we employ pure nitrogen atmospheric pressure plasma jet (APPJ) and N2‐H2O APPJ to hydrophilize PE surfaces. Wettability, time stability, chemical composition, micromorphology, and mechanical properties of the treated surfaces are investigated by contact angle measurement, X‐ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and electric digital display push–pull machine. The pure nitrogen APPJ can hydrophilize PE surfaces without inducing obvious microstructure changes, and relatively better wettability (water contact angle = 13°) could thereby be achieved. On the other hand, the N2‐H2O APPJ creates micro/nanoscale pores on the treated hydrophilic surfaces, contributing to the better time stability and lower tensile strength. The results reported here clearly demonstrate the great potential of nitrogen APPJs with different water mixing ratios in controlling surface wettability and microstructures of polymer surfaces. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47136.

Efficient and Air‐Stable Aqueous‐Processed Organic Solar Cells and Transistors: Impact of Water Addition on Processability and Thin‐Film Morphologies of Electroactive Materials

AbstractThe authors report the development of a desirable aqueous process for ecofriendly fabrication of efficient and stable organic field‐effect transistors (eco‐OFETs) and polymer solar cells (eco‐PSCs). Intriguingly, the addition of a typical antisolvent, water, to ethanol is found to remarkably enhance the solubility of oligoethylene glycol (OEG) side chain‐based electroactive materials (e.g., the highly crystalline conjugated polymer PPDT2FBT‐A and the fullerene monoadduct PC61BO12). A water–ethanol cosolvent with a 1:1 molar ratio provides an increased solubility of PPDT2FBT‐A from 2.3 to 42.9 mg mL−1 and that of PC61BO12 from 0.3 to 40.5 mg mL−1. Owing to the improved processability, efficient eco‐OFETs with a hole mobility of 2.0 × 10−2 cm2 V−1 s−1 and eco‐PSCs with a power conversion efficiency of 2.05% are successfully fabricated. In addition, the eco‐PSCs fabricated with water–ethanol processing are highly stable under ambient conditions, showing the great potential of this new process for industrial scale application. To better understand the underlying role of water addition, the influence of water addition on the thin‐film morphologies and the performance of the eco‐OFETs and eco‐PSCs are studied. Additionally, it is demonstrated that the application of the aqueous process can be extended to a variety of other OEG‐based material systems.

The Influence of Water Addition on High-Temperature Tribological Properties of Interstitial Free Steel Sliding against Different Counterparts

ABSTRACT The influence of only water addition on the hot metal forming process has not yet been reported in regard to tribological performance. In the present study, simulation tests were carried out on a pin-on-disc tribometer to evaluate the effects of water lubrication on the wear and friction behaviors of interstitial free (IF) steel sliding against different countersurface materials at 800°C in comparison with those in dry sliding. The opposing materials were selected as GCr15 steel and ceramic-based compounds including ZrO2, SiC, and Si3N4. It has been found that Si-based component–IF steel pairs exhibit the lowest wear losses despite achieving relatively high friction. Water addition adversely impairs the friction and wear characteristics on steel-steel tribopairs, whereas it shows insignificant effects on the pair involving ceramic-based components except ZrO2. Varying tribological responses can be found among different mated surfaces under water lubrication. X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy were utilized to examine the worn surface. The acting mechanism of water addition for different rubbing pairs was further discussed from the aspects of oxide tribochemistry.

In Situ Analysis of the Li–O2 Battery with Thermally Reduced Graphene Oxide Cathode: Influence of Water Addition

The Li–O2 battery technology holds the promise to deliver a battery with significantly increased specific energy compared to today’s Li-ion batteries. As a cathode support material, reduced graphene oxide has received increasing attention in the Li–O2 battery community due to the possibility of increased discharge capacity, increased battery cyclability, and decreased charging overpotential. In this article we investigate the effect of water on a thermally reduced graphene oxide cathode in a Li–O2 battery. Differential electrochemical mass spectroscopy reveals a decreased electron count for batteries with 1000 ppm water added to the electrolyte in comparison to dry batteries, indicating additional parasitic electrochemical or chemical processes. A comparable capacity of the wet and dry batteries indicates that the reaction mechanism in the Li–O2 battery also depends on the surface of the cathode and not only on addition of water to the electrolyte as demonstrated by the solution-based mechanism. In situ s...

Influence of water addition on mechanical properties of thermoplastic starch foils

Abstract The aim of this paper is to study the influence of water on the mechanical properties of thermoplastic starch films. Experimental observations of Young modulus and the breaking force of thermoplastic starch foils with different percentages of polyvinyl alcohol and keratin additives and screw rotation speeds are reported. Thermoplastic starch foils are prepared by the extrusion method with the bowling from potato starch and glycerol as a plasticizer. Young modulus and the breaking force were determined by the random marker method. Measurements of Young modulus and the breaking force of the films were performed after their production and after dosing with water. It was observed that in all cases Young modulus decreases after dosing with water, but the breaking force lied in the same range. Thermoplastic starch foils produced at the screw rotation speed equal to 60 r.p.m. have the best mechanical properties. The highest value of Young modulus and the breaking force were obtained for samples with a 1% keratin additive.

Influence of water addition on the structure of plasma-deposited allyl alcohol polymer films

One hundred and fifty nanometre thick polymer films made of allyl alcohol and H2O addition were deposited onto aluminium substrates using the radio-frequency (rf) pulsed plasma mode. The structure–property relationships of polymer films were studied in dependence on the precursor ratio allyl alcohol-water. Both the regularity of structure and composition of such thin films in comparison to chemically polymerized allyl alcohol were investigated using by bulk-sensitive Fourier transform infrared spectroscopy (FTIR) in the spectral range of 4000–500 cm−1 as well as surface-sensitive X-ray photoelectron spectroscopy (XPS). The intention of this work was to increase the yield in OH groups by addition of water to the allyl alcohol precursor. For an unambiguous identification of the functionality of the deposited films, the OH groups were labelled with trifluoroacetic anhydride and subsequently measured by XPS as well as quantitatively by FTIR. As expected, the O/C ratio grew with increasing water admixture by oxidation of both the plasma polymerized allyl alcohol layer to preferably aldehyde and/or carboxylic acid groups. In contrary, the concentration of OH groups in the deposited polymer film decreases dramatically with increasing admixture of water to the allyl alcohol plasma. It has been shown that the additional water has produced preferably higher oxidized C-Ox species with two or three C–O bonds. This fits also very well with the observation that almost no deuterium is introduced into the surface of plasma polymer if D2O was added instead of H2O.

Wet or dry mechanochemical synthesis of calcium phosphates? Influence of the water content on DCPD–CaO reaction kinetics

Mechanosynthesis of calcium phosphates can be performed under wet or dry conditions. In most papers and patents, grinding under wet conditions was selected. So far, only a few papers were devoted to dry mechanosynthesis of calcium phosphates. To understand why wet mechanosynthesis was preferred, the influence of water addition on the kinetics of the mechanochemical reaction of dicalcium phosphate dihydrate with calcium oxide was investigated. The DCPD disappearance rate constant k and the final reaction time t f were determined in each case and correlated with the water content present in the slurry. Results showed that the addition water (i) slowed down the reaction rate and (ii) increased the powder contamination by mill material (hard porcelain) due to ball and vial erosion; and that (iii) wet milling did not generate the expected products, in contrast to dry grinding, because porcelain induced hydroxyapatite decomposition with the formation of β-tricalcium phosphate and silicon-stabilized tricalcium phosphate. Consequently, dry mechanosynthesis appears preferable to wet milling in the preparation of calcium phosphates of biological interest.

Influence of Water Addition on the Kinetics of Mechanochemical Synthesis of Hydroxyapatites from DCPD+CaO

Influence of Water Addition on the Kinetics of Mechanochemical Synthesis of Hydroxyapatites from DCPD+CaO

Investigation of excited-state proton transfer in 2-naphthol derivatives containing a carboxyl group in organic solvents and in methanol–water mixtures

Excited-state proton transfer (ESPT) in 2-naphthol derivatives with electron withdrawing substituent (SO 2NH) dissolved in methanol and methanol–water mixtures is investigated. The analogs studied contain also a carboxyl group, situated at various distances from the proton donating phenolic group. The method of investigation consists in measuring the steady state fluorescence spectra. The parameter R of these spectra (ratio of fluorescence quantum yields at two defined wavelengths) given by Weller’s equation was fitted to the experimental values of R as a function of water concentration in the mixtures. From this procedure, ESPT rate constant and other parameters of this reaction were obtained. It was found that the carboxyl group contained in the molecule of 2-naphthol derivative greatly enhances ESPT reaction in methanol. This effect depends on the flexibility of a chain linking the aromatic system with the carboxyl group. ESPT reaction in five various analogs of 2-naphthol with an electron withdrawing substituent and a carboxyl group was compared. Influence of water addition and the fluorophore concentration, on ESPT was studied in detail. The effect of organic acid addition to the methanolic solution was also investigated. Influence of other organic solvents on ESPT is compared to that of methanol. Our results indicate that proton transfer to the carboxyl group and a preferential binding of other polar molecules play an essential role in the kinetics of proton transfer reaction The role of these catalytic effects is more pronounced in low polar media than in water solutions. By analogy to our model systems, conclusions concerning the proton transfer reaction in biological energy transformation systems can be drawn.

Thermal stability of alkyl carbonate mixed-solvent electrolytes for lithium ion cells

The thermal stability of some mixed-solvent electrolytes used in lithium cells was measured by differential scanning calorimetry (DSC) using airtight containers. The electrolytes used were ethylene carbonate ( EC)+ diethyl carbonate ( DEC) , EC+ dimethyl carbonate ( DMC) , propylene carbonate (PC)+DEC, and PC+DMC in which was dissolved 1 M LiPF 6 or 1 M LiClO 4. The influence of water addition and lithium metal addition on the thermal behavior of these electrolytes was also investigated. The exothermic peak of LiPF 6 electrolytes containing DEC was found at 255 °C, and the peak temperature of the electrolytes containing DEC was 15–20 °C lower than that of LiPF 6 electrolytes containing DMC. This effect was also observed in the electrolytes including LiClO 4. DMC was found to be more reactive than DEC. The thermal behavior of various kinds of LiPF 6 electrolytes with lithium metal was measured by DSC. The exothermic reaction of 1 M LiPF 6/EC+DEC, 1 M LiPF 6/EC+DMC, and 1 M LiPF 6/PC+DMC with lithium metal began at the melting point of lithium metal because of the break down of the solid electrolyte interface (SEI). The temperature was approximately 180 °C, whereas the self-heating of 1 M LiPF 6/PC+DEC occurred before the melting point of lithium metal. The temperature at which the self-exothermal reaction began was 140 °C. Therefore, the lithium metal in this electrolyte was found to be thermally unstable. When water was added to the above electrolytes with lithium metal, the exothermic reaction began at less than 130 °C, probably due to a collapse of SEI in response to the HF that was a product of the reaction between LiPF 6 and the added water.

Conductivity, viscosity and IR spectra of Li, Na and Mg perchlorate solutions in propylene carbonate/water mixed solvents

The influence of water addition on the electric conductivity, viscosity and IR spectra of Mg, Li and Na perchlorate solutions in propylene carbonate (PC) was examined. Conductivity and viscosity data pointed out ion–solvent and ion–ion associations that were most pronounced in Mg(ClO4)2 solutions. IR investigations were directed towards the spectral region 1000–600 cm-1. The changes of the ν4 band of the perchlorate anion at 624 cm-1 and the changes of solvent bands in the spectral region 980–890 cm-1 caused by water addition to 1 M solutions indicated the formation of contact ion pairs. The appearance and increase in intensity of the otherwise IR-inactive perchlorate band at 931 cm-1, upon water addition, was attributed to cation–H2O–ClO4- solvent shared ion pairs.

Gel Region and Gelation Behavior of Alkoxide Solutions in the B<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>O System

Influence of water addition and catalysts such as HCl and NH4OH on the gel region and the gelation behavior of alkoxide solutions was examined in the B2O3-Na2O system. The resuls are as follows: (1) With the water addition r=0-1, where r=water added/water necessary for complete hydrolysis, gel region was found in the range of B2O3=60-90mol%. With water addition of r>1 gel region was reduced. Crystals precipitated with the addition of HCl. The gel region with NH4OH addition was the same as that observed with water addition. (2) Gelation time was reduced by water addition. No effect on gelation time was found by NH4OH addition. (3) From the measurements of pH and temperature rise in the B(OBu)3-NaOCH3 mixtures, it was inferred that sodium-borate precursors (complex) such as B(OBu)3(ONa) and B(OBu)3-n(ONa)n formed in the B(OBu)3-NaOCH3 mixtures. With water addition, the formation of hydroxide complex such as B(OH)3ONa and B(OH)3-n(ONa)n was also inferred.

Influence of water addition on structural and electrochemical behaviour of liquid ammoniates: A study of LiClO 4·4NH 3 ammoniate/H 2O mixtures

The ammoniates of lithium perchlorate (LiClO 4• xNH 3) can be used as liquid or solid electrolytes in lithium batteries. The compounds possess a very low ammonia pressure and a large electroactivity range at room temperature. The presence of water in the electrolyte is one of the main problems for the lithium anode. From calorimetric measurements on the water-ammoniate system and an X-ray powder diffraction study on crystalline compounds that appear on lithium dipped in the electrolyte, a maximum water content, x = 0.2, can be derived. Above this limit, the thermodynamic properties of the compounds change and the lithium reacts dramatically with the electrolyte. Electrochemical stability ranges behave, over all the water molar fractions studied, in accordance with structural features.