共查询到20条相似文献,搜索用时 31 毫秒
1.
K. S. Gupta R. K. Mehta A. K. Sharma P. K. Mudgal S. P. Bansal 《Transition Metal Chemistry》2008,33(7):809-817
For getting an insight into the mechanism of atmospheric autoxidation of sulfur(IV), the kinetics of this autoxidation reaction
catalyzed by CoO, Co2O3 and Ni2O3 in buffered alkaline medium has been studied, and found to be defined by Eqs. I and II for catalysis by cobalt oxides and
Ni2O3, respectively.
The values of empirical rate parameters were: A{0.22(CoO), 0.8 L mol−1s−1 (Co2O3)}, K
1{2.5 × 102 (Ni2O3)}, K
2{2.5 × 102(CoO), 0.6 × 102 (Co2O3)} and k
1{5.0 × 10−2(Ni2O3), 1.0 × 10−6(CoO), 1.7 × 10−5 s−1(Co2O3)} at pH 8.20 (CoO and Co2O3) and pH 7.05 (Ni2O3) and 30 °C. This is perhaps the first study in which the detailed kinetics in the presence of ethanol, a well known free
radical scavenger for oxysulfur radicals, has been carried out, and the rate laws for catalysis by cobalt oxides and Ni2O3 in the presence of ethanol were Eqs. III and IV, respectively.
For comparison, the effect of ethanol on these catalytic reactions was studied in acidic medium also. In addition, alkaline
medium, the values of the inhibition factor C were 1.9 × 104 and 4.0 × 103 L mol−1 s for CoO and Co2O3, respectively; for Ni2O3, C was only 3.0 × 102 only. On the other hand, in acidic medium, the values of this factor were all low: 20 (CoO), 0.7 (Co2O3) and 1.4 (Ni2O3). Based on these results, a radical mechanism for CoO and Co2O3 catalysis in alkaline medium, and a nonradical mechanism for Ni2O3 in both alkaline and acidic media and for cobalt oxides in acidic media are proposed. 相似文献
(I) |
(II) |
(III) |
(IV) |
2.
M. H. Pournaghi-Azar H. Dastangoo R. Fadakar bajeh baj 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):75-81
In the present work the uranyl hexacyanoferrate (K2UO2[Fe(CN)6]) is deposited on the palladized aluminum (Pd-Al) electrode from a
\textUO22 + + \textFe( \textCN )6 - 3 {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K2UO2[Fe(CN)6] from the Pd-Al surface. The operational conditions including: pH, K3Fe(CN)6 concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was
linear in concentration range 10–460 μM. of
\textUO22 + {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K2UO2[Fe(CN)6] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores. 相似文献
3.
Jia Cao Wenliang Wang Yue Zhang Weina Wang Tianlei Zhang Jian Lv Chunying Li 《Theoretical chemistry accounts》2011,129(6):771-780
The reaction mechanism of CH3SCH2CH3 with OH radical is studied at the CCSD(T)/6-311+G(3df,p)//MP2/6-31+G(2d,p) level of theory. Three hydrogen abstraction channels,
one substitution process and five addition–elimination channels are identified in the title reaction. The result shows hydrogen
abstraction is dominant. Substitution process and addition–elimination reactions may be negligible because of the high barrier
heights. Enthalpies of formation [
\Updeltaf H(298.15\textK)o \Updelta_{f} H_{(298.15{\text{K}})}^{o} ] of the reactants and products are evaluated at the CBS-QB3, G3 and G3MP2 levels of theory, respectively. It is found that
the calculated enthalpies of formation by the aforementioned three methods are in consistent with the available experimental
data. Rate constants and branching ratios are estimated by means of the conventional transition state theory with the Wigner
tunneling correction over the temperature range of 200–900 K. The calculation shows that the formations of P1 (CH2SCH2CH3 + H2O) and P2 (CH3SCHCH3 + H2O) are major products during 200–900 K. The three-parameter expressions for the total rate constant is fitted to be
k\texttotal = 1.45 ×10 - 21 T3.24 exp( - 1384.54/T) k_{\text{total}} = 1.45 \times 10^{ - 21} T^{3.24} \exp ( - 1384.54/T) cm3 molecule−1 s−1 from 200 to 900 K. 相似文献
4.
M. G. Zuev 《Russian Journal of Inorganic Chemistry》2010,55(1):93-95
Solid-phase interactions in the V2O5-Ta2O5-MoO3 system were studied. The formation of com- pounds TaVO5 and VTa9O25 in the V2O5-Ta2O5 binary system was verified. Tetragonal VTa9O25-base solid solutions of the general formula Ta5 + 4x
V5 − 4x
O25 (x = 0.25–1) and TaVO5-base solid solutions of the general formula Ta
x
Mo1 − x
V2 − x
O8 − 3x
(x = 0.625–1) were found to form. Subsolidus phase equilibria in the V2O5-Ta2O5-MoO3 were determined. 相似文献
5.
The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory,
the molar enthalpy of solution of the title compound at infinite dilution was calculated to be DsolHm¥ = 14.34 kJ·mol-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters bMX(0)L, bMX(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and CMXfLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies (
φ
L) and relative partial molar enthalpies of the compound ([`(L)]2)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the
cation C5H7N2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be DfHmo(C5H7N2+,aq)=-(2.096±0.801) kJ·mol-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}. 相似文献
6.
E. Yu. Pikalova V. G. Bamburov A. A. Murashkina A. D. Neuimin A. K. Demin S. V. Plaksin 《Russian Journal of Electrochemistry》2011,47(6):690-696
CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical
devices: electrolytic cells, oxygen sensors, and solid oxide fuel cells. In this work, studies are presented of the effect
of the dopant cation radius and its concentration on the physico-chemical properties of the Ce1 − x
Ln
x
O2 − δ solid solutions (x = 0–0.20; Ln = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) and also of multicomponent solid solutions of Ce1 − x
Ln
x/2Ln′
x/2O2 − δ (x = 0–0.20; Ln = Sm, La, Gd and Ln′ = Dy, Nd, Y) and Ce1 − x − y
Sm
x
M
y
O2 − δ (M = Ca, Sr, Ba) obtained using the solid-phase synthesis technique. Electric properties of the samples were studied in the
temperature range of 623–1173 K and in the oxygen partial pressure range of 0.01–10−22 MPa. The values of oxygen critical pressure ( pO2 * )\left( {p_{O_2 }^* } \right) are presented, at which the ionic and electron conductivity values are equal. The values were calculated on the basis of
experimental dependences at 1023 K at the assumption that the ionic conductivity value is determined only by the dopant concentration
and its effective ionic radius and is independent of the oxygen partial pressure. 相似文献
7.
8.
D. S. Zakharova O. A. Chertkova A. A. Chelkin L. G. Bruk O. N. Temkin 《Russian Chemical Bulletin》2013,62(3):844-846
Kinetic isotope effects for oxidation reactions of ethylene and cyclohexene in solutions of cationic palladium(ii) complexes in MeCN-H2O(D2O) systems, were measured. It was established that the ratio of the initial reaction rates ${{R_0^{H_2 O} } \mathord{\left/ {\vphantom {{R_0^{H_2 O} } {R_0^{D_2 O} }}} \right. \kern-0em} {R_0^{D_2 O} }} $ is equal to 1 for both reactions with the use of cationic complexes of the type Pd(MeCN) x (H2O)4?x 2+, which differs from oxidation reactions catalyzed by chloride palladium complexes in the same solutions, where the ratio ${{R_0^{H_2 O} } \mathord{\left/ {\vphantom {{R_0^{H_2 O} } {R_0^{D_2 O} }}} \right. \kern-0em} {R_0^{D_2 O} }} $ = 5.0±0.16 and 4.73±0.14 at H+ molar fraction of 0.48 and 0.16, respectively (H+ molar fraction was calculated based on the sum of [H+] and [D+]). 相似文献
9.
Ponnusamy Sami Kandasamy Venkateshwari Natarajan Mariselvi Arunachalam Sarathi Kasi Rajasekaran 《Transition Metal Chemistry》2010,35(2):137-142
l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate,
[ \textPV\textV \textV\textV \textW 1 0 \textO 4 0 ]5 - , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the
reaction are cystine and two electron-reduced heteropoly blue, [PVIVVIVW10O40]7−. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C.
The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order
kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction
proceeds through an outer-sphere mechanism. For the dianion −SCH2CH(NH3
+)COO−, the rate constant for the cross electron transfer reaction is 96 M−1s−1 at 25 °C. The self-exchange rate constant for the
- \textSCH2 \textCH( \textNH3 + )\textCOO - \mathord