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1.
In order to investigate the influence of Cl −/SO 42− molar ratios and hydrolysis temperature on the hydrolysis process and TiO 2 pigment, H 2TiO 3 was prepared with a low concentration of titanyl sulfuric–chloric acid solution by hydrothermal hydrolysis. Under the optimal hydrolysis conditions, 1.5–2.2 μm of H 2TiO 3 samples were achieved. After doping and calcination, anatase TiO 2 pigments demonstrated excellent performance: the achromic ability of tinctorial strength (TCS) and blue phase index (SCX) were 1,429 and 4.07, respectively. As hydrolysis was a significant step in the process, the structure was simplified to a periodic structure of Ti[OH](H 2O) 3Cl(SO 4) to simulate the cluster structures. Based on experimental results and density functional theory (DFT) calculation, the hydrolysis mechanism was presumed to be a process of anionic (OH −, Cl − and SO 42−) competition reaction to explain the formation of anatase-type H 2TiO 3, and the crystal growth direction of H 2TiO 3 was also confirmed to be a (OA) and b (OB). 相似文献
2.
Ternary clusters (NH 3)·(H 2SO 4)·(H 2O) n have been widely studied. However, the structures and binding energies of relatively larger cluster ( n > 6) remain unclear, which hinders the study of other interesting properties. Ternary clusters of (NH 3)·(H 2SO 4)·(H 2O) n, n = 0-14, were investigated using MD simulations and quantum chemical calculations. For n = 1, a proton was transferred from H 2SO 4 to NH 3. For n = 10, both protons of H 2SO 4 were transferred to NH 3 and H 2O, respectively. The NH 4+ and HSO 4− formed a contact ion-pair [NH 4+-HSO 4−] for n = 1-6 and a solvent separated ion-pair [NH 4+-H 2O-HSO 4−] for n = 7-9. Therefore, we observed two obvious transitions from neutral to single protonation (from H 2SO 4 to NH 3) to double protonation (from H 2SO 4 to NH 3 and H 2O) with increasing n. In general, the structures with single protonation and solvated ion-pair were higher in entropy than those with double protonation and contact ion-pair of single protonation and were thus preferred at higher temperature. As a result, the inversion between single and double protonated clusters was postponed until n = 12 according to the average binding Gibbs free energy at the normal condition. These results can serve as a good start point for studies of the other properties of these clusters and as a model for the solvation of the [H 2SO 4-NH 3] complex in bulk water. 相似文献
3.
Infrared multiphoton photooxidation of NH 2D in NH 3 mixtures was observed to produce exclusively HDO, suggesting a single step deuterium separation efficiency of [D 2O]/([D 20]+[H 2O]) ⩾ 50% which is significantly higher than that of the theoretical value, 33%. The results are explained by the large rate differences in the radical scavenging steps, i.e. k(D+O 2) = 2.2 × 10 9M −1 s −1, k(NH 2+O 2) ⩽ 5 × 10 6 M −1 s −1 and k(NH 2+NH 2)=1.6 × 10 10 M −1 s −1. With Ti solid powder as a catalyst, we observed that the formation yields of HDO are at least three to four times higher than those without a catalyst. 相似文献
4.
The reduction of iodine by hydroxylamine within the [H +] range 3×10 −1–3×10 −4 mol.L −1 was first studied until completion of the reaction. In most cases, the concentration of iodine decreased monotonically. However, within a narrow range of reagent concentrations ([NH 3OH +] 0/[I 2] 0 ratio below 15, [H +] around 0.1 mol.L −1, and ionic strength around 0.1 mol.L −1), the [I 2] and [I 3−] vs. time curves showed 2 and 3 extrema, respectively. This peculiar phenomenon is discussed using a 4 reaction scheme (I 2+I −⇔︁I 3−, 2 I 2+NH 3OH ++H 2O→HNO 2+4 I −+5 H +, NH 3OH ++HNO 2→N 2O+2 H 2O+H +, and 2 HNO 2+2 I −+2 H +→2 NO+I 2+2 H 2O). In a flow reactor, sustained oscillations in redox potential were recorded with an extremely long period (around 24 h). The kinetics of the reaction was then investigated in the starting conditions. The proposed rate equation points out a reinforcement of the inhibition by hydrogen ions when [H +] is above 4×10 −2 mol.L −1 at 25°C. A mechanism based on ion-transfer reactions is postulated. It involves both NH 2OH and NH 3OH + as the reducing reactive species. The additional rate suppression by H + at low pH would be connected to the existence of H 2OI + in the reactive medium. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 785–797, 1998 相似文献
5.
In a recent study investigating the suitability of solvent extraction (SX) for the separation of Ta and Nb, it was shown that speciation data would be required to help explain the data obtained. As traditional speciation techniques cannot be readily applied for Ta and Nb, it was decided to determine the suitability of molecular modeling for this purpose. During the SX experiments the aqueous phase consisted of sulfuric acid (H 2SO 4), water, and metal species. In this study density functional theory (DFT) modeling was used to calculate the formation energy of five possible reactions of H 2SO 4 and H 2O. Different functional and basis set combinations were compared as well as the effect of infinite dilution by using the conductor-like screening model (COSMO), which simulates infinite dilution of solvents of varying polarity and includes the short-range interactions of the solute particles. The results obtained were used to determine whether it is possible to predict the reactions and mechanism when H 2SO 4 and H 2O interact during SX. According to the results, the deprotonation of H 2SO 4 was endothermic in a 1:1 acid–water ratio, while being both exothermic in the 1:5 and 1:10 acid–water ratio forming HSO 4− and SO 42− respectively. Furthermore, it was seen that the hydration and dehydration of H 2SO 4 in a bulk H 2O solution was a continuous process. From the energy calculations it was determined that although the H 2SO 4●H 2O, HSO 4−●H 2O, and H 2SO 4●2H 2O species could form, they would most likely react with H 2O molecules to form HSO 4−, H 3O +, and H 2O. © 2018 Wiley Periodicals, Inc. 相似文献
6.
The generation of negative ions from SO 2 in the gas phase was studied using the thermal surface ionization method. Six anion types were measured: O −, S −, SO −, and SO 2− and anions with m/z=96 and m/z=128. The most abundant anion formed was S − and the formation routes are discussed for each of the six anions. O −, S −, and SO − are formed via dissociative electron attachment to the molecule, whereas the generation of SO 2− and anions with m/z=96 and m/z=128 are probably associated with the formation of H 2SO 4 in the gas inlet system and the ion source. Using statistical thermodynamics the dissociation temperatures of SO 2 and SO in the gas phase are calculated and values of above 1800 °C are obtained for both molecules. We also estimated the optimal filament temperatures for the formation of all anions measured, indicating that for SO 2 the optimal temperature is related to the electron affinity of the molecules: the optimal temperature increases with decreasing value of the electron affinity for the molecule corresponding to the respective anion. 相似文献
7.
Liquid-state 29Si NMR was used to investigate the hydrolysis and condensation kinetics of ammonia-catalyzed tetraethoxysilane (TEOS) in methanol
system. The reactive rate constants were calculated by applying first-order reaction approximation and the steady state approximation
theory. The reaction orders with respect to TEOS, ammonia and water were derived, as well as the activation energies and the
Arrhenius constants. It was found that the formation of intermediate species Si(OH)(OEt) 3 was the rate-limiting step and its reaction rate equation was r
TEOS=7.41×10 −3[TEOS][NH 3] 0.333[H 2O] 0.227. Higher reactive temperature benefited the hydrolysis of TEOS. The results presented here indicated quantificationally that
the formation of colloidal SiO 2 particles was controlled by the initial hydrolysis of TEOS. 相似文献
8.
The electrochemical behaviors of melamine (MEL) were studied at paraffin-impregnated graphite electrode in PBS (pH 7.0) and 0.5 M H2SO4. Various methods including UV–vis thin-layer spectroelectrochemistry, infrared spectra (IR) and electrochemicatry have been performed to investigate the characteristics. In 0.1 M PBS (pH 7.0), MEL loses two electrons to form a dication, which couples head-to-head with a neutral molecule of MEL to form a dimer accompanying the production of azocompound, the dimer plays a role of a monomer in the following polymerization. In 0.5 M H2SO4, unstable MEL mostly hydrolyzes to form ammeline, ammelide, s-triazine-2,4,6-trion, and tricyanic acid, respectively; The hydrolysis could be accelerated by electrochemical method; Meanwhile, MEL associates tricyanic acid to give a plane molecule cake by hydrogen bonding. The spectra responses of MEL at 205 and 234 nm are linearly increasing in a same concentration range of 1.0 × 10−7–1.0 × 10−5 M in 0.5 M H2SO4 (determination limit, 1 × 10−8 and 3 × 10−8 (3σ)). The proposed method was successfully applied to the determination of MEL in real sample. 相似文献
9.
PSTA BATAN has synthesized zirconium sulfate (ZS) through two methods. Synthesis pathway (I) from Na 2ZrO 3 (CDZ) and (II) through zirconium oxychloride (ZOC). This research aimed to compare both pathways by utilizing FTIR. Path (I) was done using concentrations of H 2SO 4 65%, contact time of 30, 60, 90, and 150 min, and temperatures of 125, 150, 175, and 225 °C. While path II has been carried out in previous studies [1]. The FTIR image comparison was finished by tracing sulfate derivative functional groups from a wavenumber of 4000–400 cm −1. The O–H stretching at 3441.01 cm −1 as the Zr(OH)Zr group and OH vibration in 3425.68 cm −1 were found at each pathway. However, at pathway (II), we observed another vibration at 3132.40 cm −1 as the NH 3 compound group. Furthermore, the track records of S–O and SO stretching on both pathways were checked at 1635.64, 1095.57, and 956.69 cm −1, respectively, as H 3O +, SO 42−, and SO 32− species. The real difference in pathway (I) was revealed by the presence of H 2SO 4 residue at 802.39 cm −1. At the same time, the Zr–O–Zr and O–Zr–O stretching could be detected in both pathways at the wavenumber of 594.09 and 470.63 cm −1 consecutively. The form of synthesis pathway (I) product was predicted as Zr(SO 4) 2, while the product of path (II) forecasted as Zr(NH 3)(SO 4) 2 compound. 相似文献
10.
It is found that the broadening of the 1100-cm −1 line of SO −24, caused by increasing [H 3O +], is unaffected by addition of 4 M LiCl, NaBr, KCl and NH 4Cl. This finding is in line with the lack of influence of NaCl reported earlier. The significance of these findings, in terms of the reaction mechanism, is discussed. 相似文献
11.
In this study, we investigated the effects of four inorganic anions (Cl −, SO 42−, H 2PO 4−/HPO 42−, and HCO 3−/CO 32−) on titanium dioxide (TiO 2)-based photocatalytic oxidation of aqueous ammonia (NH 4+/NH 3) at pH ∼ 9 and ∼10 and nitrite (NO 2−) over the pH range of 4–11. The initial rates of NH 4+/NH 3 and NO 2− photocatalytic oxidation are dependent on both the pH and the anion species. Our results indicate that, except for CO 32−, which decreased the homogeneous oxidation rate of NH 4+/NH 3 by UV-illuminated hydrogen peroxide, OH scavenging by anions and/or direct oxidation of NH 4+/NH 3 and NO 2− by anion radicals did not affect rates of TiO 2 photocatalytic oxidation. While HPO 42− enhanced NH 4+/NH 3 photocatalytic oxidation at pH ∼ 9 and ∼10, H 2PO 4−/HPO 42− inhibited NO 2− oxidation at low to neutral pH values. The presence of Cl −, SO 42−, and HCO 3− had no effect on NH 4+/NH 3 and NO 2− photocatalytic oxidation at pH ∼ 9 and ∼10, whereas CO 32− slowed NH 4+/NH 3 but not NO 2− photocatalytic oxidation at pH ∼ 11. Photocatalytic oxidation of NH 4+/NH 3 to NO 2− is the rate-limiting step in the complete oxidation of NH 4+/NH 3 to NO 3− in the presence of common wastewater anions. Therefore, in photocatalytic oxidation treatment, we should choose conditions such as alkaline pH that will maximize the NH 4+/NH 3 oxidation rate. 相似文献
12.
Manganese(II) is oxidized by ozone in acid solution, k=(1.5±0.2)×10 3 M −1 s −1 in HClO 4 and k=(1.8±0.2)×10 3M −1 s −1 in H 2SO 4. The plausible mechanism is an oxygen atom transfer from O 3 to Mn 2+ producing the manganyl ion MnO 2+, which subsequently reacts rapidly with Mn 2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length range 200–310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III)+H 2O 2)=2.8×10 3M −1 s −1 at pH 0–2. The mechanism of the reaction involving formation of the manganese(II)-superoxide complex and reaction of H 2O 2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 207–214, 1998. 相似文献
13.
The four ternary limiting isotherms of the system K +− NH 4+ CrO 4−− SO 4−− H 2O are given for 25° C. In the systems K 2SO 4 (NH 4) 2SO 4 H 2O and K 2SO 4 K 2CrO 4 H 2O only one solid phase has been encountered; both systems belong to the type I of the ROOZEBOOM classification. A miscibility gap is present in the systems (NH 4) 2CrO 4 K 2CrO 4 H 2O and (NH 4) 2CrO 4 (NH 4) 2SO 4 H 2O; they belong to ROOZEBOOM'S type V. 相似文献
14.
Cu doped MoSi 2N 4 monolayer (Cu-MoSi 2N 4) was firstly proposed to analyze adsorption performances of common gas molecules including O 2, N 2, CO, NO, NO 2, CO 2, SO 2, H 2O, NH 3 and CH 4 via density functional theory (DFT) combining with non-equilibrium Green's function (NEGF). The electronic transport calculations indicate that Cu-MoSi 2N 4 monolayer has high sensitivity for CO, NO, NO 2 and NH 3 molecules. However, only NH 3 molecule adsorbs on the Cu-MoSi 2N 4 monolayer with moderate strength (−0.55 eV) and desorbs at room temperature (2.36×10 −3 s). Thus, Cu-MoSi 2N 4 monolayer is demonstrated as a potential NH 3 sensor. 相似文献
15.
SnS and SnS 2 are layered semiconductors, with potential promising properties for electro- and photocatalytic hydrogen (H 2) production. The vast knowledge in preparation and modification of layered structures was still not employed successfully in this system to fully maximize its potential. Here, the first report of structural transformation of SnS 2 into SnS with Mo-doping as a bifunctional catalyst for the hydrogen evolution reaction (HER) is reported. The structural phase transition optimized the properties of the material, providing a more delicate morphology with additional catalytic sites. The electrochemical studies showed overpotential of 377 mV at 10 mA cm −2 for HER with Tafel slopes of 100 mV dec −1 in 0.5 m H 2SO 4 for 10 % Mo-SnS. The same structure acts as an efficient photocatalyst in the generation of H 2 from water under visible illumination with rate of 0.136 mmol g −1 h −1 of H 2, which is 20 times higher than pristine SnS 2 under visible light. 相似文献
16.
The gas phase hydration of glyoxal (HCOCHO) in the presence of sulfuric acid (H2SO4) were studied by the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST). The mechanism and rate constant of the ve di erent reaction paths are consid-ered corresponding to HCOCHO+H 2O, HCOCHO+H 2O H 2O, HCOCHO H 2O+H 2O, HCOCHO+H 2O H 2SO 4 and HCOCHO H 2O+H 2SO 4. Results show that H 2SO 4 has a strong catalytic ability, which can signi cantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD(T)/6-311++G(3df, 3pd)//M06-2X/6-311++G(3df, 3pd) level of theory. The rate constant of the H 2SO 4 catalyzed hydrolysis of glyoxal is 1.34×10 -11cm 3/(molecule s), about 10 13 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10 -11cm 3/(molecule s) at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H 2SO 4 catalyst is feasible and could compete with the reaction glyoxal+OH under certain atmospheric condi-tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer 相似文献
17.
Electrosynthesis of NH 3 through the N 2 reduction reaction (NRR) under ambient conditions is regarded as promising technology to replace the industrial energy- and capital-intensive Haber–Bosch process. Herein, a room-temperature spontaneous redox approach to fabricate a core–shell-structured Au@CeO 2 composite, with Au nanoparticle sizes below about 10 nm and a loading amount of 3.6 wt %, is reported for the NRR. The results demonstrate that as-synthesized Au@CeO 2 possesses a surface area of 40.7 m 2 g −1 and a porous structure. As an electrocatalyst, it exhibits high NRR activity, with an NH 3 yield rate of 28.2 μg h −1 cm −2 (10.6 μg h −1 mg −1cat., 293.8 μg h −1 mg −1Au) and a faradaic efficiency of 9.50 % at −0.4 V versus a reversible hydrogen electrode in 0.01 m H 2SO 4 electrolyte. The characterization results reveal the presence of rich oxygen vacancies in the CeO 2 nanoparticle shell of Au@CeO 2; these are favorable for N 2 adsorption and activation for the NRR. This has been further verified by theoretical calculations. The abundant oxygen vacancies in the CeO 2 nanoparticle shell, combined with the Au nanoparticle core of Au@CeO 2, are electrocatalytically active sites for the NRR, and thus, synergistically enhance the conversion of N 2 into NH 3. 相似文献
18.
The deactivation of I( 2P ½) by R-OH compounds (R = H, C nH 2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H 2O, CH 3OH, C 2H 5OH, n-C 3H 7OH, i-C 3H 7OH, n-C 4H 9OH, i-C 4H 9OH, s-C 4H 9OH, t-C 4H 9OH, are respectively, 2.4 ± 0.3 × 10 −12, 5.5 ± 0.8 × 10 −12, 8 ± 1 × 10 −12, 10 ± 1 × 10 −12, 10 ± 1 × 10 −12, 11.1 ± 0.9 × 10 −12, 9.8 ± 0.9 × 10 −12, 7.1 ± 0.7 × 10 −12, and 4.1 ± 0.4× 10 −12 cm 3 molec −1 s −1 at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc. 相似文献
19.
The formic acid catalyzed gas‐phase reaction between H 2O and SO 3 and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc‐pv(T+d)z and CCSD(T)//MP2/aug‐cc‐pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H 2O with SO 3 is lowered through formic acid catalysis from 15.97 kcal mol ?1 to ?15.12 and ?14.83 kcal mol ?1 for the formed H 2O ??? SO 3 complex plus HCOOH and the formed H 2O ??? HCOOH complex plus SO 3, respectively, at the CCSD(T)//MP2/aug‐cc‐pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to ?3.07 kcal mol ?1 from 35.82 kcal mol ?1 with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO 3+H 2O reaction with formic acid is 10 5 times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H 2SO 4 reaction is about 10 ?13 cm 3 molecule ?1 s ?1 in the temperature range 200–280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO 3 and H 2SO 4 in atmospheric chemistry. 相似文献
20.
In the title compounds, 3-(dihydroxyboryl)anilinium bisulfate monohydrate, C 6H 9BNO 2+·HSO 4−·H 2O ( I ), and 3-(dihydroxyboryl)anilinium methyl sulfate, C 6H 9BNO 2+·CH 3SO 4− ( II ), the almost planar boronic acid molecules are linked by pairs of O—H…O hydrogen bonds, forming centrosymmetric motifs that can be described by the graph-set R22(8) motif. In both crystals, the B(OH) 2 group acquires a syn– anti conformation (with respect to the H atoms). The presence of the hydrogen-bonding functional groups B(OH) 2, NH 3+, HSO 4−, CH 3SO 4− and H 2O generates three-dimensional hydrogen-bonded networks, in which the bisulfate (HSO 4−) and methyl sulfate (CH 3SO 4−) counter-ions act as the central building blocks within the crystal structures. Furthermore, in both structures, the packing is stabilized by weak boron–π interactions, as shown by noncovalent interactions (NCI) index calculations. 相似文献
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