共查询到20条相似文献,搜索用时 46 毫秒
1.
The primary objective of modifying cotton fabric was to impart bactericidal properties to attract various fields such as defence,
space and textile industrial applications. Chemically initiated graft copolymerization of 4-vinyl pyridine (4-VP) and acrylonitrile
(AN) onto cotton fabric was carried out using ceric ammonium nitrate as a redox initiator. Optimum conditions pertaining to
maximum percentage of grafting were evaluated as a function of concentration of initiator [CAN], concentration of nitric acid,
monomer concentration, water, temperature and reaction time. Maximum grafting of 4-VP (51.63%) and AN (69.23%) was obtained
respectively at optimum
[ \text CAN ] = 2.738 ×10 - 2 \left[ {\text{CAN}} \right] = 2.738 \times {10^{ - 2}} and 2.19 × 10 −2 moles/L,
[ 4 - \text VP ] = 47.55 ×10 - 22\text moles/\text L \left[ {4 - {\text{VP}}} \right] = 47.55 \times {10^{ - 22}}{\text{moles}}/{\text{L}} ,
[ \text AN ] = 18.85 ×10 - 22\text moles/\text L \left[ {\text{AN}} \right] = 18.85 \times {10^{ - 22}}{\text{moles}}/{\text{L}} ,
[ \text HN\text O3 ] = 11.9 ×10 - 2 \left[ {{\text{HN}}{{\text{O}}_3}} \right] = 11.9 \times {10^{ - 2}} and 89.5 × 10 −22 moles/L in 20 and 25 ml of water at an optimum temperature 70 °C and 60 °C with in 180 and 120 min. Antibacterial properties
were induced into the modified cotton fabric by treating the grafted fabric with benzyl chloride. The grafted and quaternized
copolymer were characterized by FTIR and Thermogravimetrical analysis. The bactericidal action of cotton fabric was tested
by filtration test and it was observed that fabric grafted with 4-VP was more effective and efficient antibacterial as compared
to AN grafted cotton sample. 相似文献
2.
Mixed micellization behavior of dimeric cationic surfactants ethanediyl-1,2-bis(dimethyl alkyl ammonium bromide) ( m-2- m where m = 10, 12) with conventional single chain cationic surfactants like cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium
chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl)
were studied in aqueous and aqueous polyethylene glycol (PEG) solutions at 298.15, 308.15 and 318.15 K respectively using
conductometric and viscometric methods. In aqueous solutions, all the combinations (except 12-2-12 + CTAB) were found to behave
nonideally with mutual synergism which decreases with increase in temperature. Various thermodynamic parameters of micellization
like
\Updelta G\textm\texto {{\Updelta}}G_{\text{m}}^{\text{o}} ,
\Updelta H\textm\texto {{\Updelta}}H_{\text{m}}^{\text{o}} and
\Updelta S\textm\texto {{\Updelta}}S_{\text{m}}^{\text{o}} were evaluated and discussed. Similarly in presence of PEG, the thermodynamic properties like
\Updelta G\textt\texto {{\Updelta}}G_{\text{t}}^{\text{o}} ,
\Updelta H\textt\texto {{\Updelta}}H_{\text{t}}^{\text{o}} and
\Updelta S\textt\texto {{\Updelta}}S_{\text{t}}^{\text{o}} associated with the transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound
mixed micelles at various temperatures were also calculated. The negative values of
\Updelta H\textt\texto {{\Updelta}}H_{\text{t}}^{\text{o}} show that aggregation process is more exothermic than micellization whereas the negative values of
\Updelta S\textt\texto {{\Updelta}}S_{\text{t}}^{\text{o}} indicate that the presence of polymer bound mixed micelles decreases the degree of randomness of the system. Viscosity studies
show that in aqueous solutions all the combinations of 10-2-10/12-2-12 display negative departure in the relative viscosity
(η r) from additivity rule which decreases with increase in temperature. Similarly in the presence of 5% PEG solutions the magnitude
of the negative departure decreases for all the combinations and becomes positive in the case of C14BCl and CPC combinations
with the studied gemini surfactants at higher temperatures. 相似文献
3.
Two new organic–inorganic hybrid compounds
[\text Cu\textI ( \text en ) 2 ( \text H 2 \text O )] 2 { ( \text SiW\textVI 1 1 \text W\textV 1\text O 40 ) 2 [ \text Cu\textII ( \text en ) 2 ( \text H 2 \text O )] 2 [\text Cu\textII ( \text en ) 2 ] 2 }·6 \text H 2 \text O [{\text{Cu}}^{\text{I}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)]_{ 2} \left\{ {\left( {{\text{SiW}}^{\text{VI}}_{ 1 1} {\text{W}}^{\text{V}}_{ 1}{\text{O}}_{ 40} } \right)_{ 2} \left[ {{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)\left] {_{ 2} } \right[{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} } \right]_{ 2} } \right\}{\cdot}6 {\text{H}}_{ 2} {\text{O}} ( 1) and (H 2
L) 2[SiW 12O 40]·H 2O ( 2) [en = ethylenediamine, L = 1,4-bis(3-pyridinecarboxamido)benzene], have been hydrothermally synthesized and characterized by IR, elemental analyses,
TG analysis, and single-crystal X-ray diffraction. Structural analyses indicate that compound 1 exhibits an interesting three-dimensional(3D) cross-like supramolecular network through arrangement of a 1D organic–inorganic
hybrid chain
{ ( \text SiW\textVI 1 1 \text W\textV 1 \text O 40 ) 2 [ \text Cu\textII ( \text en ) 2 ( \text H 2 \text O )] 2 [\text Cu\textII ( \text en ) 2 ] 2 } 2- . \left\{ {\left( {{\text{SiW}}^{\text{VI}}_{ 1 1} {\text{W}}^{\text{V}}_{ 1} {\text{O}}_{ 40} } \right)_{ 2} \left[ {{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)\left] {_{ 2} } \right[{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} } \right]_{ 2} } \right\}^{ 2- } . The compound 2 consists of protonated L ligand and [SiW 12O 40] 4− anion. The protonated L ligands have been extended into a 2D network via hydrogen-bonding interactions. The guest [SiW 12O 40] 4− clusters have been incorporated into the square voids of the 2D host network as templates. The electrochemical behavior and
electrocatalysis of compound 2 bulk-modified carbon paste electrode ( 2-CPE) have been studied. 相似文献
4.
The reactions of K 3[Cu(CN) 4], R 3SnCl (R = Me or ph) and 2,3-dimethyl quinoxaline (dmqox) in H 2O/acetonitrile media at room temperature afford the 3D-supramolecular coordination polymers (SCP)
3¥ [ \text Cu 2 ( \text CN ) 2 \text dmqox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 2} {\text{dmqox}}} \right] , 1 and
3¥ [ \text Cu 2 ( \text CN ) 4 ·( \text Ph 3 \text Sn ) 2 ·\text dmqox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 4} \cdot \left( {{\text{Ph}}_{ 3} {\text{Sn}}} \right)_{ 2} \cdot {\text{dmqox}}} \right] , 2. The structure of the tin free 1 consists of parallel zigzag chains connected by dmqox to form 2D-sheets containing hexagonal 18-atom fused Cu 6(CN) 4(dmqox) 2 rings. The interwoven sheets along the a axis are close packed by extensive H-bonds developing 3D-network structure. The structures of 1 and 2 are investigated by elemental analysis IR, NMR and mass spectra. The ESI + and ESI − mass spectra of 2 support its polymeric nature while the ESI + mass spectrum confirms the expected M. W. suggested by elemental analysis. The 13C-NMR spectrum of 2 supports the fact that the network structure of 2 contains the rhombic [Cu 2(μ 3-CN) 2] motif. The structure of 2 was compared with the structure of the reported prototype
3¥ [ \text Cu 2 ( \text CN ) 4 ·( \text Ph 3 \text Sn ) 2 ·\text qox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 4} \cdot \left( {{\text{Ph}}_{ 3} {\text{Sn}}} \right)_{ 2} \cdot {\text{qox}}} \right] as well as the other related structures. 相似文献
5.
P-octyl polyethylene glycol phenyl ether (Triton X-100) and cetyltrimethylammonium bromide (CTAB) were mixed to be used as
surfactant for preparing reverse microemulsion with n-hexane, n-hexanol and water. Effects of weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant
on the conductivity were studied. The results indicate that the conductivity of the mixed surfactants reverse microemulsion
is greatly higher than that of the single surfactant system. The reverse microemulsion has been modified to be with good conductivity.
The weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant have obvious effects on the
conductivity of the reverse microemulsion. Furthermore, the electrochemical behavior of potassium ferricyanide [K 3Fe(CN) 6] in the mixed surfactants reverse microemulsion was investigated by cyclic voltammetry. The result shows that the redox processes
of
\text Fe( \text CN ) 6 3- / \text Fe( \text CN ) 6 4- {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 3- } / {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 4-} present good reversibility and are controlled by diffusion in the system. 相似文献
6.
12-Tungstophosphoric acid supported on montmorillonite K10 (PWA/mont-K10) catalysed Pechmann condensation reaction was reported.
The catalyst was characterized by XRD, FTIR, UV–Vis DRS, surface area and pore size analysis, TGA and acidity by DRIFTS using
pyridine. The morphology of the catalyst was studied by SEM. The activity of mont-K10, mont-KSF,
\textSO 4 2 - \mathord | / |
\vphantom \textSO 4 2 - \textZrO 2 \textZrO 2 {{{\text{SO}}_{ 4}^{{ 2 {-}}} } \mathord{\left/ {\vphantom {{{\text{SO}}_{ 4}^{{ 2 {-}}} } {{\text{ZrO}}_{ 2} }}} \right. \kern-\nulldelimiterspace} {{\text{ZrO}}_{ 2} }} , 12-tungstophosphoric acid, and PWA/mont-K10 was investigated by condensation reaction of resorcinol with ethyl acetoacetate
in the absence of solvent. Effect of molar ratio, amount of catalyst, reaction temperature and time on the yield of 7-hydroxy-4-methylcoumarin
had been investigated on PWA/mont-K10. PWA/mont-K10 catalysed condensation of ethyl acetoacetate with phenol and a few substituted
phenols had also been carried out to yield corresponding coumarins. The recycled catalyst showed reduced activity after single
use. 15 wt% PWA on mont-K10 was found to be effective for synthesis of coumarin derivatives without employing any solvent. 相似文献
7.
Abstract The kinetics of ammonia oxidation with oxygen over a Rh(110) surface were studied in the pressure range 10 −5–10 −4 mbar. Nitrogen was found to be the preferred product at low partial pressures ratios
\text p\texto 2 :\text p\textNH 3 {\text{p}}_{{{\text{o}}_{ 2} }} :{\text{p}}_{{{\text{NH}}_{ 3} }} , while the NO pathway was favored with oxygen rich gas mixtures and at high temperature. The reactive sticking coefficient
of O 2 reaches up to 0.05 under steady state conditions. Pronounced hysteresis effects in the reaction rates were found in T-cycling
experiments. Sustained oscillations in the reaction rates occurred under isothermal conditions at T = 620 K at a total pressure
of 4 × 10 −5 mbar. 相似文献
8.
Three fluorinated cationic surfactants were prepared by condensing N-methyl diethanol amine pentafluoro benzoate with stoichiometric amounts of octyl, dodecyl or hexadecyl bromide. The surface
properties and parameters were investigated to find the relationship between the structures of the hydrophobic portion of
such compounds. The properties studied include surface tension, critical micelle concentration (CMC), effectiveness (Π cmc), maximum surface excess (Γ max) and minimum surface area (A min) were investigated with respect to different concentrations at 25 °C. Standard free energies of micellization and adsorption
of the prepared surfactants in the aqueous solution were studied. The values of Γ max, standard free energies of micellization
\Updelta \text G\textmic\texto \Updelta {\text{G}}_{\text{mic}}^{\text{o}} and adsorption
\Updelta \text G\textads\texto \Updelta {\text{G}}_{\text{ads}}^{\text{o}} were found to increase with the chain length, while the cmc and minimum surface area occupied by one molecule A min were found to decrease. The biocidal activity was determined through the inhibition zone diameter of prepared compounds which
were measured against five strains of a representative group of microorganisms. 相似文献
9.
Coupling winter small grain cover crops (CC) with manure (M) application may increase retention of manure nitrogen (N) in
corn ( Zea mays L.), -soybean [ Glycine max (L.) Merr], cropping systems. The objective of this research was to quantify soil N changes after application of liquid swine
M ( Sus scrofa L.) at target N rates of 112, 224, and 336 kg N ha −1 with and without a CC. A winter rye ( Secale cereale L.)-oat ( Avena sativa L.) CC was established prior to fall M injection. Surface soil (0–20 cm) inorganic N concentrations were quantified every
week for up to 6 weeks after M application in 2005 and 2006. Soil profile (0–120 cm in 5, 20-cm depth increments) inorganic
N, total N, total organic carbon and bulk density were quantified for each depth increment in the fall before M application
and before the CC was killed the following spring. Surface soil inorganic N on the day of application averaged
318 \text mg \text N \text kg - 1\textsoil 318\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}}} in 2005 and
186 \text mg \text N \text kg - 1\textsoil 186\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}} } in 2006 and stabilized at
150 \text mg \text N \text kg - 1\textsoil 150\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}}} in both years by mid-November. Surface soil NO 3-N concentrations in the M band were more than 30 times higher in the fall of 2005 than in 2006. The CC reduced surface soil
NO 3-N concentrations after manure application by 32% and 67% in mid- November 2005 and 2006, respectively. Manure applied at
224 kg N ha −1 without a CC had significantly more soil profile inorganic-N (480 kg N ha −1) in the spring after M application than manured soils with a CC for the 112 (298 kg N ha −1) and 224 (281 kg N ha −1) N rates, and equivalent inorganic N to the 336 (433 kg N ha −1) N rate. These results quantify the potential for cover crops to enhance manure N retention and reduce N leaching potential
in farming systems utilizing manure. 相似文献
10.
The reactions of K 3[Cu(CN) 4], R 3SnCl and bipodal ligands, where R = (n-Bu) 3SnCl and L = quinoxaline (qox) and R = Me 3SnCl and L = quinazoline (qaz) afford the red needle crystals of
¥3 [ \text Cu2 ( \text CN ) 2 m\text-( qox) ] 2 {}_{\infty }^{3} \left[ {{\text{Cu}}_{2} \left( {\text{CN}} \right)_{2} \mu {\text{-(qox)}}} \right]_{2} , 1 and the orange needle crystals of [Cu 2(CN) 2μ(qaz)] n, 2. 1 was subjected to single crystals X-ray study while 2 was investigated by IR, 1H NMR and mass spectra as well as TGA. The crystal structure of 1 exhibits puckered CuCN chains connected by qox molecules forming 2D-sheets. The 2D-sheets contain hexagonal nets stacked
in A···A···A fashion. The paralleled sheets are close packed via extensive H-bonds, π–π stacking, strong Cu-Cu interaction
and short Cu–C contacts which develop 3D-network. Unique rhombic [Cu 2(μ 3-CN) 2] motifs result as consequence of interwoven of the 2D-sheets. The structure of 2 exhibits different XRPD pattern than that of 1 although, the two structures have the same Cu:CN:L stoichiometric ratio. The emission spectra of 1 and 2 display bands around 390, 420 and 475 nm corresponding to MC transition, 1(n,π*) → S o and MLCT, respectively. Thus, 1 and 2 can be considered as examples of room-temperature luminescent Cu-containing polymers which can be used in applications as
molecular sensing systems. Also, the oxidative degradation of Metanil Yellow (MY) dye has been investigated by hydrogen peroxide
catalyzed by 1 or 2. The catalytic activity of 1 is more pronounced than that of 2. 相似文献
11.
A series of novel dialkyl disulfonate gemini surfactants (2C n-SCT where n is the carbon number of the hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine.
The chemical structures of the prepared compounds were confirmed by 1H NMR, 13C NMR, IR spectra, and ESI–MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25 °C were determined
by surface tension and electrical conductivity methods. With the increasing length of the carbon chain, the values of their
CMC initially decreased, and then increased with an alkyl chain length of 14. The surface tension measurements of 2C n-SCT (except for n = 14) determined that there is a low CMC, a great efficiency in lowering the surface tension, and a strong
adsorption at the air–water interface. In addition, adsorption and micellization behavior of 2C n-SCT were estimated from p C
20, the minimum average area per surfactant molecule ( A
min), and standard free energy micellization and adsorption (
\Updelta G\textmic° \text and \Updelta G\textads° \Updelta G_{\text{mic}}^{^\circ } \,{\text{and}}\,\Updelta G_{\text{ads}}^{^\circ } ). These properties are significantly influenced by the chain length n, and the adsorption is promoted more than the micellization. 相似文献
12.
We investigated endogenous plant hormones and needle growth in Pinus tabulaeformis plants grown in open-top chambers and exposed to ambient or elevated concentrations of carbon dioxide (CO 2) and/or ozone (O 3). Exposure to elevated CO 2 for 100 days significantly increased the change in fresh needle weight, indole-3-acetic acid (IAA), isopentenyl-adenosine
(iPA), and dihydrozeatin riboside (DHZR) content. Abscisic acid (ABA) content decreased, and no effect was observed on zeatin
riboside (ZR) content or changes in needle dry weight. The ratios of IAA/ABA and total cytokinins (CKs)/ABA
( \text ZR + \text DHZR + \text iPA/\text ABA ) \left( {{\text{ZR}} + {\text{DHZR}} + {\text{iPA}}/{\text{ABA}}} \right) were increased. Elevated O 3 significantly decreased IAA and ZR, and decreased the ratios of IAA/ABA and CKs/ABA. Ozone treatment increased ABA content
but did not change iPA or DHZR content or change fresh or dry needle weights. The combination treatment significantly increased
ABA content and the IAA/ABA ratio but decreased the total CKs/ABA ratio and had no effect on CKs or IAA content or change
in fresh and dry needle weights. The results indicate that elevated CO 2 ameliorated the effects of elevated O 3 on tree growth. 相似文献
13.
In order to investigate the partial electronic conduction in the high oxide ion conductor of the system Bi 2O 3-Y 2O 3 under low oxygen pressure, e.m.f. and polarization methods were employed. Although the electrolyte was decomposed when the \(P_{{\text{O}}_{\text{2}} }\) was lower than the equilibrium \(P_{{\text{O}}_{\text{2}} }\) of Bi, Bi 2O 3 mixture at each temperature, the ionic transport number was found to be close to unity above that \(P_{{\text{O}}_{\text{2}} }\) . The hole conductivity ( σ p) and the electron conductivity ( σ p) could be expressed as follows, $$\begin{gathered} \sigma _p \Omega cm = 5 \cdot 0 \times 10^2 \left( {P_{O_2 } atm^{ - 1} } \right)^{{1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}} \exp \left[ { - 106 kJ\left( {RT mol} \right)^{ - 1} } \right] \hfill \\ \sigma _p \Omega cm = 3 \cdot 4 \times 10^5 \left( {P_{O_2 } atm^{ - 1} } \right)^{ - {1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}} \exp \left[ { - 213 kJ\left( {RT mol} \right)^{ - 1} } \right] \hfill \\ \end{gathered} $$ These values were much lower than the oxide ion conductivity under ordinary oxygen pressure. 相似文献
14.
The piezoelectric ceramic Pb 0.94Sr 0.06(Zr 0.53Ti 0.47)O 3 + 0.1 wt% (Ni 2O 3 + Cr 2O 3) + x wt%CeO 2 (PCrNi-4) was prepared using a traditional solid state sintered method. The effects of CeO 2 doping on phase structure, microstructure, piezoelectric, and dielectric properties were analyzed by means of XRD, SEM, and
electrical property measurements. The results indicate that when CeO 2 doping content is 0.3 wt% and sintering temperature is 1,280 °C, the dielectric loss value of the ceramic is the least with
a value of 0.00238, and the dielectric factor
e 33\textT \varepsilon_{33}^{\text{T}} , piezoelectric strain factor d
33, planar electromechanical coupling coefficient K
p and mechanical quality factor Q
m of the ceramic is 1400, 375 pCN −1, 0.68, and 460, respectively. 相似文献
15.
Dispersion copolymerization of dimethyl diallyl ammonium chloride with acrylamide has been investigated by the dilatometer
technique using the mixture of poly(vinylpyrrolidone) and poly(dimethyl diallyl ammonium chloride) as the composite stabilizer
and 2,2′-azobis(2-methylpropionconidine)dihydro chloride as the initiator. Monomer reactivity ratios of AM and DMDAAC were
determined by the application of Fineman-Ross methods. The analysis of reactivity ratios revealed that DMDAAC is less reactive
than AM, and copolymers formed are statistically in nature. The influences of the molar ratio of AM to DMDAAC, concentrations
of monomers, stabilizer and initiator, etc. on polymerization rate and intrinsic viscosity of polymer have been examined.
The rate of polymerization (R p) can be represented by Rp μ [ M] 1.44, Rp μ [ S] 0.39, Rp μ [ I] 0.60 {R_{\rm{p}}} \propto {[M]^{1.44}},{R_{\rm{p}}} \propto {[S]^{0.39}},{R_{\rm{p}}} \propto {[I]^{0.60}} . The overall activation energy for the rate of polymerization is 37.38 kJ/mol over the temperature range 35–55°C.Based on
the experimental results, the polymerization mechanisms were discussed. 相似文献
16.
The kinetics of atom transfer radical polymerization of N-(S)-α-methylbenzylmethacryloylamine (S-(-)-α-MBMA) and α-methylbenzylmethacrylate
(α-MBM) monomers, as assessed by % conversion, were determined at 48 °C in a toluene/ethanol mixture (60:40) by a dilatometry
method. The effect of the presence of — CONH- or — COOR- moieties on the ATRP polymerization of such monomers was investigated.
Controlled polymerizations were performed with the catalyst system [ M ]/[ R - X ]/[ Mt n - Y ]/[ L ] \left[ {\hbox{M}} \right]/\left[ {{\hbox{R}} - {\hbox{X}}} \right]/\left[ {{\hbox{M}}{{\hbox{t}}^{\rm{n}}} - {\hbox{Y}}} \right]/\left[ {\hbox{L}} \right] at molar ratios of 100:15:15:15; 200:15:15:15; 300:15:15:15; and 400:15:15:15, where R-X was EBIB or MCP, M tn-Y(CuBr or CuCl) and L (Me 6TREN). Also with N-S-(-)-α-MBMA, some studies used ATCA and ABPA as R-X. Plots of the ln[M] 0/[M] vs t as well as from the log Rp vs log [M] showed that the ATRP processes followed a pseudo first-order kinetics with respect to the monomer concentration and
that the molecular weight of the resulting polymers increased with the conversion. The ATRP results for both monomers showed
a similar trend and revealed that the presence of N-S-(-)-α-MBMA (amide group) affects the polymerization, i.e. it did not
react when the EBIB/CuBr/Me 6TREN catalyst system was used. The M n and M w were determined by 1H-NMR and GPC. PDI values fell between 1.19 and 1.5, and indicated that the majority of the systems showed good control of
polymerization. 相似文献
17.
The influence of CO 2 and H 2O on the activity of 4% Sr-La 2O 3 mimics that observed with pure La 2O 3, and a reversible inhibition of the rate is observed. CO 2 causes a greater effect, with decreases in rate of about 65% with O 2 present and 90% in its absence, while with H 2O in the feed, the rate decreased around 35-40% with O 2 present or absent. The influence of these two reaction products on kinetic behavior can be described by assuming competitive adsorption on the surface, incorporating adsorbed CO 2 and H 2O in the site balance, and using rate expressions previously proposed for this reaction over Sr-promoted La 2O 3. In the absence of O 2, the rate expression is $$r_{N_2 } = \frac{{k'P_{{\text{NO}}} P_{{\text{CH}}_{\text{4}} } }}{{{\text{(1 + }}K_{{\text{NO}}} P_{{\text{NO}}} {\text{ + }}K_{{\text{CH}}_{\text{4}} } P_{{\text{CH}}_{\text{4}} } {\text{ + }}K_{{\text{CO}}_{\text{2}} } P_{{\text{CO}}_{\text{2}} } {\text{ + }}K_{{\text{H}}_{\text{2}} {\text{O}}} P_{{\text{H}}_{\text{2}} {\text{O}}} {\text{)}}^{\text{2}} }},$$ which yields a good fit to the experimental data and gives optimized equilibrium adsorption constants that demonstrate thermodynamic consistency. With O 2 in the feed, nondifferential changes in reactant concentrations through the reactor bed were accounted for by assuming integral reactor behavior and simultaneously considering both CH 4 combustion and CH 4 reduction of NO, which provided the following rate law for total CH 4 disappearance: $$(r_{{\text{CH}}_{\text{4}} } )_{\text{T}} = \frac{{k'_{{\text{com}}} P_{{\text{CH}}_{\text{4}} } P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} + k'_{{\text{NO}}} P_{{\text{NO}}} P_{{\text{CH}}_{\text{4}} } P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} }}{{{\text{(1 + }}K_{{\text{NO}}} P_{{\text{NO}}} {\text{ + }}K_{{\text{CH}}_{\text{4}} } P_{{\text{CH}}_{\text{4}} } {\text{ + }}K_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} P_{{\text{O}}_{\text{2}} }^{{\text{0}}{\text{.5}}} {\text{ + }}K_{{\text{CO}}_{\text{2}} } P_{{\text{CO}}_{\text{2}} } {\text{ + }}K_{{\text{H}}_{\text{2}} {\text{O}}} P_{{\text{H}}_{\text{2}} {\text{O}}} {\text{)}}^{\text{2}} }}.$$ The second term of this expression represents N 2 formation, and it again fit the experimental data well. The fitting constants in the denominator, which correspond to equilibrium adsorption constants, were not only thermodynamically consistent but also provided entropies and enthalpies of adsorption that were similar to values obtained with other La 2O 3-based catalysts. Apparent activation energies typically ranged from 23 to 28 kcal/mol with O 2 absent and 31-36 kcal/mol with O 2 in the feed. With CO 2 in the feed, but no O 2, the activation energy for the formation of a methyl group via interaction of CH 4 with adsorbed NO was determined to be 35 kcal/mol. 相似文献
18.
A scaling model is presented to analyze the nonlinear rheology of unentangled polymer melts filled with high concentration
of small spherical particles. Assuming the majority of chains to be reversibly adsorbed to the surface of the particles, we
show that the emergence of nonlinearity in the viscoelastic response of the composite system subjected to a 2D shear flow
results from stretching of the adsorbed chains and increasing desorption rate of the adsorbed segments due to the imposed
deformation. The steady-state shear viscosity of the mixture in nonlinear shear thinning regime follows the power law h ~ [(g)\dot] - 1/2 , \eta \sim \dot{\gamma }^{ - 1/2} , where [(g)\dot] \dot{\gamma } is the applied shear rate. At large strain amplitude γ 0, the storage and loss moduli in strain sweep tests scale as G¢ ~ g 0 - 1 G^{\prime}\sim \gamma_{0}^{ - 1} and G¢¢ ~ g 0 - 1/2 , G^{\prime\prime}\sim \gamma_{0}^{ - 1/2} , respectively. 相似文献
19.
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y 2O 3–stabilized–ZrO 2 (YSZ), an O 2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O 2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β 1) and 340–500 °C (state β 2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(T ads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O 2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover O ads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, O ads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β 2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
20.
Specific retention volumes, V
g
0, were determined for 21 solute probes on poly (caprolactonediol) (PCLD) in the temperature range 323.15–403.15 K by inverse
gas chromatography. The retention diagrams drawn between ln V
g
0 versus 1/ T are linear for all the solutes since PCLD with ten repeating units in its chain behaving like a non polymeric material under
the conditions applied. The stationary phase with melting temperature ~321 K is in the liquid state in the GC column over
the temperature range studied and hence found to be suitable to determine infinite dilution partial molar thermodynamic properties
of mixing for solutes on PCLD. The V
g
0 values have been used to calculate weight fraction activity coefficients Ω ∞ and Flory–Huggins interaction parameters, χ
12∞. The average partial molar enthalpy of solution,
[`(\Updelta H)] 1S , \overline{\Updelta H}_{1}^{S} , and partial molar enthalpy of mixing,
[`(\Updelta H)] 1¥ , \overline{\Updelta H}_{1}^{\infty } , are calculated using V
g
0 and Ω ∞ respectively. The average molar enthalpy of vaporization Δ H
1
V
for solutes have been calculated using
[`(\Updelta H)] 1¥ \overline{\Updelta H}_{1}^{\infty } and
[`(\Updelta H)] 1S \overline{\Updelta H}_{1}^{S} values and compared with the literature values at 363.15 K which is the average column temperature. The partial molar entropy
of mixing,
[`(\Updelta S)] 1¥ \overline{\Updelta S}_{1}^{\infty } calculated at 363.15 K are in good correlation with the average
[`(\Updelta H)] 1¥ \overline{\Updelta H}_{1}^{\infty } values. The total solubility parameter due to Guillet and the Hansen solubility parameters (HSP) are calculated for PCLD using
χ
12∞ values. In the present work the Hansen solubility parameters have been calculated using a new method following the Hansen
theory and Huang method with less weight on polar and hydrogen bonding components. The errors in the solubility HSP are lower
and the correlation coefficients are better in both the methods compared to unweighted three dimensional model. 相似文献
|