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1.
Layered double hydroxide pillared by Paratungstate A ion, Mg 12Al 6(OH) 36(W 7O 24)·4H 2O, was prepared via anion exchange reaction of the synthetic precursor, Mg 4Al 2(OH) 12TA· xH 2O (TA 2−=terephthalate), and [W 7O 24] 6− ion. Some physico-chemical properties were measured and the preparation conditions were studied. Trace aqueous organocholorine pesticide, hexachlorocyclohexane (HCH), was totally degraded and mineralized into CO 2 and HCl by irradiating a Mg 12Al 6(OH) 36(W 7O 24)·4H 2O suspension in the near UV area. Disappearance of trace HCH follows Langmuir–Hinshelwood first-order kinetics. The model and mechanism for the photocatalytic degradation of HCH on the Mg 12Al 6(OH) 36(W 7O 24)·4H 2O were proposed, indicating that the interlayer space is the reaction field, and that photogeneration of OH√ radicals are responsible for the degradation pathway. 相似文献
2.
The catalytic effect of a heteropolyacid, H 4SiW 12O 40, on nitrobenzene (20 and 30 μM) oxidation in supercritical water was investigated. A capillary flow-through reactor was operated at varying temperatures ( T=400–500 °C; P=30.7 MPa) and H 4SiW 12O 40 concentrations (3.5–34.8 μM) in an attempt to establish global power-law rate expressions for homogenous H 4SiW 12O 40-catalyzed and uncatalyzed supercritical water oxidation. Oxidation pathways and reaction mechanisms were further examined via primary oxidation product identification and the addition of various hydroxyl radical scavengers (2-propanol, acetone, acetone-d 6, bromide and iodide) to the reaction medium. Under our experimental conditions, nitrobenzene degradation rates were significantly enhanced in the presence of H 4SiW 12O 40. The major differences in temperature dependence observed between catalyzed and uncatalyzed nitrobenzene oxidation kinetics strongly suggest that the reaction path of H 4SiW 12O 40-catalyzed supercritical water oxidation (average activation Ea=218 kJ/mol; k=0.015–0.806 s −1 energy for T=440–500 °C; Ea=134 kJ/mol for the temperature range T=470–490 °C) apparently differs from that of uncatalyzed supercritical water oxidation ( Ea=212 kJ/mol; k=0.37–6.6 μM s −1). Similar primary oxidation products (i.e. phenol and 2-, 3-, and 4-nitrophenol) were identified for both treatment systems. H 4SiW 12O 40-catalyzed homogenous nitrobenzene oxidation kinetics was not sensitive to the presence of OH√ scavengers. 相似文献
3.
The sintering behavior and dielectric properties of the monoclinic zirconolite-like structure compound Bi 2(Zn 1/3Nb 2/3) 2O 7 (BZN) and Bi 2(Zn 1/3Nb 2/3−xV x) 2O 7 (BZNV, x = 0.001) sintered under air and N 2 atmosphere were investigated. The pure phase were obtained between 810 and 990 °C both for BZN and BZNV ceramics. The substitution of V 2O 5 and N 2 atmosphere accelerated the densification of ceramics slightly. The influences on microwave dielectric properties from different atmosphere were discussed in this work. The best microwave properties of BZN ceramics were obtained at 900 °C under N 2 atmosphere with r = 76.1, Q = 850 and Qf = 3260 GHz while the best properties of BZNV ceramics were got at 930 °C under air atmosphere with r = 76.7, Q = 890 and Qf = 3580 GHz. The temperature coefficient of resonant frequency τf was not obviously influenced by the different atmospheres. For BZN ceramics the τf was −79.8 ppm/°C while τf is −87.5 ppm/°C for BZNV ceramics. 相似文献
4.
Friedels salt, the chlorinated compound 3CaO · Al 2O 3 · CaCl 2 · 10H 2O (AFm phase), presents a structural phase transition at about 30°C from a monoclinic to a rhombohedral phase. It has been studied by X-ray powder diffraction and optical microscopy in transmitted light with crossed polarisers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37°C from X-ray single crystal diffraction data. The compound crystallises in the space group R
c with lattice parameters of a = 5.7358(6)Å and c = 46.849(9)Å ( Z = 3 and Dx = 2.111 g/cm 3). The refinement of 498 independent reflections with I > 2σ( I) led to a residual factor of 7.1%. The Friedels salt can be described as a layered structure with positively charged main layers of composition [Ca 2Al(OH) 6] + and negatively charged layers of composition [Cl −,2H 2O]. The chloride anions are surrounded by 10 hydrogen atoms, of which six belong to hydroxyl groups and four to water molecules. The structural phase transition may be related to the size of the chloride anions, which are not adapted to the octahedral cavity formed by bonded water molecules. 相似文献
5.
A novel electrochemical approach was developed for the kinetic study of the formation of heteropolyanions. The method (dual pulse amperometry, DPA) is based on the detections of currents due to the transfers of polyanions at the nitrobenzene-water interface. In this study, DPA was applied to the kinetic study of the formation of two Keggin anions, viz., [SiMo 12O 40] 4− and [GeMo 12O 40] 4−. Prior to the kinetic study, cyclic voltammetric measurements were performed to confirm that the Keggin anion and its lacunary anion ([H 3SiMo 11O 39] 5− or [H 3GeMO 11O 39] 5−) coexist at equilibrium under certain conditions. In DPA, double voltage pulses of different amplitudes were alternately applied to the interface to follow the concentrations of both the Keggin and the lacunary anions. The concentration-time profiles for the polyanions could be elucidated by the two-step consecutive reactions mechanism. The lacunary anion was then found to be the intermediate of the Keggin anion. 相似文献
6.
The role of La 2O 3 loading in Pd/Al 2O 3-La 2O 3 prepared by sol–gel on the catalytic properties in the NO reduction with H 2 was studied. The catalysts were characterized by N 2 physisorption, temperature-programmed reduction, differential thermal analysis, temperature-programmed oxidation and temperature-programmed desorption of NO. The physicochemical properties of Pd catalysts as well as the catalytic activity and selectivity are modified by La2O3 inclusion. The selectivity depends on the NO/H2 molar ratio (GHSV = 72,000 h−1) and the extent of interaction between Pd and La2O3. At NO/H2 = 0.5, the catalysts show high N2 selectivity (60–75%) at temperatures lower than 250 °C. For NO/H2 = 1, the N2 selectivity is almost 100% mainly for high temperatures, and even in the presence of 10% H2O vapor. The high N2 selectivity indicates a high capability of the catalysts to dissociate NO upon adsorption. This property is attributed to the creation of new adsorption sites through the formation of a surface PdOx phase interacting with La2O3. The formation of this phase is favored by the spreading of PdO promoted by La2O3. DTA shows that the phase transformation takes place at temperatures of 280–350 °C, while TPO indicates that this phase transformation is related to the oxidation process of PdO: in the case of Pd/Al2O3 the O2 uptake is consistent with the oxidation of PdO to PdO2, and when La2O3 is present the O2 uptake exceeds that amount (1.5 times). La2O3 in Pd catalysts promotes also the oxidation of Pd and dissociative adsorption of NO mainly at low temperatures (<250 °C) favoring the formation of N2. 相似文献
7.
The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 °C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl 2O 4·10H 2O converted to Ca 3Al 2(OH) 12 and amorphous aluminum hydroxide. Ca 2Al 2O 5·8H 2O transformed via the intermediate phase Ca 4Al 2O 7·13H 2O to Ca 3Al 2(OH) 12 and gibbsite, Al(OH) 3. The phase Ca 4Al 2O 7·19H 2O reacted via the same intermediate phase to Ca 3Al 2(OH) 12 and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported. 相似文献
8.
Combined effect of H 2O and SO 2 on V 2O 5/AC the activity of catalyst for selective catalytic reduction (SCR) of NO with NH 3 at lower temperatures was studied. In the absence of SO 2, H 2O inhibits the catalytic activity, which may be attributed to competitive adsorption of H 2O and reactants (NO and/or NH 3). Although SO 2 promotes the SCR activity of the V 2O 5/AC catalyst in the absence of H 2O, it speeds the deactivation of the catalyst in the presence of H 2O. The dual effect of SO 2 is attributed to the SO 42− formed on the catalyst surface, which stays as ammonium-sulfate salts on the catalyst surface. In the absence of H 2O, a small amount of ammonium-sulfate salts deposits on the surface of the catalyst, which promote the SCR activity; in the presence of H 2O, however, the deposition rate of ammonium-sulfate salts is much greater, which results in blocking of the catalyst pores and deactivates the catalyst. Decreasing V 2O 5 loading decreases the deactivation rate of the catalyst. The catalyst can be used stably at a space velocity of 9000 h −1 and temperature of 250 °C. 相似文献
9.
Fine powders of submicron-sized crystallites of BaTiO 3 were prepared at 85–130°C by the hydrothermal method, starting from TiO 2.ξH 2O gel and Ba(OH) 2 solution. The products obtained below 110°C incorporated considerable amounts of H 2O and OH − in the lattice. As-prepared BaTiO 3 is cubic and converts to the tetragonal phase after heat treatment at 1200°C, accompanied by the loss of residual OH − ions. Hydrothermal reaction of SnO 2.ξH 2O gel with Ba(OH) 2 at 150–260°C gives rise to the hydrated phase, BaSn(OH) 6.3H 2O, due to the amphoteric nature of SnO 2.ξH 2O which stabilises Sn(OH) 62− anions in basic media. On heating in air or releasing the pressure in situ at 260°C, BaSn(OH) 6.3H 2O converts to BaSnO 3 through an intermediate, BaSnO(OH) 4. Solid solutions of Ba(Ti,Sn)O 3 are directly formed from (TiO 2 + SnO 2)..ξH 2O gel up to 35 mol% SnO 2. At higher Sn contents, the hydrothermal products are mixtures of BaSn(OH) 6.3H 2O and BaTiO 3, which on annealing at 1000°C result in monophasic Ba(Ti,Sn)O 3. The sintering characteristics and the dielectric properties of the ceramics prepared out of these fine powders are presented. The dielectric properties of fine-grained Ba(Ti,Sn)O 3 ceramics are explained on the basis of the prevailing diffuse phase transition behaviour. 相似文献
10.
A series of La(Co, Mn, Fe) 1−x(Cu, Pd) xO 3 perovskites having high specific surface areas and nanosized crystal domains was prepared by reactive grinding. The solids were characterized by N 2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O 2, NO + O 2, C 3H 6, in the absence or presence of 5% H 2O, Fourier transform infrared (FTIR) spectroscopy, as well as activity tests towards NO reduction by propene under the conditions of 3000 ppm NO, 3000 ppm C 3H 6, 1% O 2, 0 or 10% H 2O, and 50,000 h −1 space velocity. The objective was to investigate the influence of H 2O addition on catalytic behavior. A good performance (100% NO conversion, 77% N 2 yield, and 90% C 3H 6 conversion) was achieved at 600 °C over LaFe 0.8Cu 0.2O 3 under a dry feed stream. With the exposure of LaFe 0.8Cu 0.2O 3 to a humid atmosphere containing 10% water vapor, the catalytic activity was slightly decreased yielding 91% NO conversion, 51% N 2 yield, and 86% C 3H 6 conversion. A competitive adsorption between H 2O vapor with O 2 and NO molecules at anion vacancies over LaFe 0.8Cu 0.2O 3 was found by means of TPD studies here. A deactivation mechanism was therefore proposed involving the occupation of available active sites by water vapor, resulting in an inhibition of catalytic activity in C 3H 6 + NO + O 2 reaction. This H 2O deactivation was also verified to be strictly reversible by removing steam from the feed. 相似文献
11.
A series of bifunctional Ni-H 3PW 12O 40/SiO 2 catalysts for the hydrocracking of n-decane were designed and prepared. The evaluation results of the catalysts show that Ni-H 3PW 12O 40/SiO 2 catalysts possess a high activity for hydrocracking of n-decane and an excellent tolerance to the sulfur and nitrogen compounds in the feedstock. Under the reaction conditions: reaction temperature 300 °C; H 2/ n-decane volume ratio of 1500; total pressure of 2 Mpa and the LHSV 2 h −1, the conversion of n-decane over reduced 5%Ni-50%H 3PW 12O 40/SiO 2 catalysts is as high as 90%, the C 5+ selectivity equal to 70%. In order to reveal the structure and nature of the catalysts, a number of characterizations including XRD, Raman, H 2-TPD, NH 3-TPD, XPS and FT-IR of pyridine adsorption were carried out. The characteristic results show that the high activity of the catalysts and high C 5+ selectivity can be related to the unique structure of the H 3PW 12O 40 and its suitable acidity. 相似文献
12.
Complete Ni 2+ exchange of a single crystal of zeolite X of composition Na 92Si 100Al 92O 384 per unit cell was attempted at 73°C with flowing aqueous 0.05 M NiCl 2 (pH=4.3 at 23°C). After partial dehydration at 23°C and ≈10 −3 Torr for two days, its structure, now of composition Ni 2(NiOH) 35(Ni 4AlO 4) 2(H 3O) 46Si 101Al 91O 384 per unit cell, was determined by X-ray diffraction techniques at 23°C (space group Fd
, a0=24.788(5) Å). It was refined using all intensities; R1=0.080 for the 236 reflections for which Fo>4σ( Fo), and wR2=0.187 using all 1138 unique reflections measured. At four crystallographic sites, 45 Ni 2+ ions were found per unit cell. Thirty of these are at two different site III′ positions. Twenty of those are close to the sides of 12-rings near O–Si–O sequences, where each coordinates octahedrally to two framework oxygens, to three water molecules which hydrogen bond to the zeolite framework, and to an OH − ion. The remaining 10 are near O–Al–O sequences; only three members of a likely octahedral coordination sphere could be found. In addition, two Ni 2+ ions are at site I, eight are at site I′, and five are at site II. Forty six H 3O + ions per unit cell, 24 at site II′ and 22 at site II, each hydrogen bond triply to six rings of the zeolite framework. Each of the 22 H 3O + ions also hydrogen bonds to a H 2O molecule that coordinates to a site III′ Ni 2+ ion. Six of the eight sodalite cages each contain four H 3O + ions at site II′; the remaining two each contains a tetrahedral orthoaluminate anion at its center. Each tetrahedral face of each orthoaluminate ion is centered by a site I′ Ni 2+ ion to give two Ni 4AlO 4 clusters. The five site II Ni 2+ ions each coordinate to a OH − ion. With 46 H 3O + ions per unit cell, the great tendency of hydrated Ni 2+ to hydrolyze within zeolite X is demonstrated. With a relatively weak single-crystal diffraction pattern, with dealumination of the zeolite framework, and with an apparent decrease in long-range Si/Al ordering likely due to the formation of antidomains, this crystal like others treated with hydrolyzing cations appears to have been damaged by Ni 2+ exchange and partial dehydration. 相似文献
13.
Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports such as activated carbon (AC), TiO 2, Al 2O 3, MgO, SiO 2 and various zeolites. The CO 2 capture capacity and regeneration property were measured in the presence of H 2O in a fixed-bed reactor, during multiple cycles at various temperature conditions (CO 2 capture at 60 °C and regeneration at 130–400 °C). Sorbents such as K 2CO 3/AC, K 2CO 3/TiO 2, K 2CO 3/MgO, and K 2CO 3/Al 2O 3, which showed excellent CO 2 capture capacity, could be completely regenerated above 130, 130, 350, and 400 °C, respectively. The decrease in the CO 2 capture capacity of K 2CO 3/Al 2O 3 and K 2CO 3/MgO, after regeneration at temperatures of less than 200 °C, could be explained through the formation of KAl(CO 3) 2(OH) 2, K 2Mg(CO 3) 2, and K 2Mg(CO 3) 2·4(H 2O), which did not completely converted to the original K 2CO 3 phase. In the case of K 2CO 3/AC and K 2CO 3/TiO 2, a KHCO 3 crystal structure was formed during CO 2 absorption, unlike K 2CO 3/Al 2O 3 and K 2CO 3/MgO. This phase could be easily converted into the original phase during regeneration, even at a low temperature (130 °C). Therefore, the formation of the KHCO 3 crystal structure after CO 2 absorption is an important factor for regeneration, even at the low temperature. The nature of support plays an important role for CO 2 absorption and regeneration capacities. In particular, the K 2CO 3/TiO 2 sorbent showed excellent characteristics in CO 2 absorption and regeneration in that it satisfies the requirements of a large amount of CO 2 absorption (mg CO 2/g sorbent) and fast and complete regeneration at a low temperature condition (1 atm, 150 °C). 相似文献
14.
A multi-component NO x-trap catalyst consisting of Pt and K supported on γ-Al 2O 3 was studied at 250 °C to determine the roles of the individual catalyst components, to identify the adsorbing species during the lean capture cycle, and to assess the effects of H 2O and CO 2 on NO x storage. The Al 2O 3 support was shown to have NO x trapping capability with and without Pt present (at 250 °C Pt/Al 2O 3 adsorbs 2.3 μmols NO x/m 2). NO x is primarily trapped on Al 2O 3 in the form of nitrates with monodentate, chelating and bridged forms apparent in Diffuse Reflectance mid-Infrared Fourier Transform Spectroscopy (DRIFTS) analysis. The addition of K to the catalyst increases the adsorption capacity to 6.2 μmols NO x/m 2, and the primary storage form on K is a free nitrate ion. Quantitative DRIFTS analysis shows that 12% of the nitrates on a Pt/K/Al 2O 3 catalyst are coordinated on the Al 2O 3 support at saturation. When 5% CO2 was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by 45% after 1 h on stream due to the competition of adsorbed free nitrates with carboxylates for adsorption sites. When 5% H2O was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by only 16% after 1 h, but the Al2O3-based nitrates decreased by 92%. Interestingly, with both 5% CO2 and 5% H2O in the feed, the total storage only decreased by 11%, as the hydroxyl groups generated on Al2O3 destabilized the K–CO2 bond; specifically, H2O mitigates the NOx storage capacity losses associated with carboxylate competition. 相似文献
15.
Both NO decomposition and NO reduction by CH 4 over 4%Sr/La 2O 3 in the absence and presence of O 2 were examined between 773 and 973 K, and N 2O decomposition was also studied. The presence of CH 4 greatly increased the conversion of NO to N 2 and this activity was further enhanced by co-fed O 2. For example, at 773 K and 15 Torr NO the specific activities of NO decomposition, reduction by CH 4 in the absence of O 2, and reduction with 1% O 2 in the feed were 8.3·10 −4, 4.6·10 −3, and 1.3·10 −2 μmol N 2/s m 2, respectively. This oxygen-enhanced activity for NO reduction is attributed to the formation of methyl (and/or methylene) species on the oxide surface. NO decomposition on this catalyst occurred with an activation energy of 28 kcal/mol and the reaction order at 923 K with respect to NO was 1.1. The rate of N 2 formation by decomposition was inhibited by O 2 in the feed even though the reaction order in NO remained the same. The rate of NO reduction by CH 4 continuously increased with temperature to 973 K with no bend-over in either the absence or the presence of O 2 with equal activation energies of 26 kcal/mol. The addition of O 2 increased the reaction order in CH 4 at 923 K from 0.19 to 0.87, while it decreased the reaction order in NO from 0.73 to 0.55. The reaction order in O 2 was 0.26 up to 0.5% O 2 during which time the CH 4 concentration was not decreased significantly. N 2O decomposition occurs rapidly on this catalyst with a specific activity of 1.6·10 −4 μmol N 2/s m 2 at 623 K and 1220 ppm N 2O and an activation energy of 24 kcal/mol. The addition of CH 4 inhibits this decomposition reaction. Finally, the use of either CO or H 2 as the reductant (no O 2) produced specific activities at 773 K that were almost 5 times greater than that with CH 4 and gave activation energies of 21–26 kcal/mol, thus demonstrating the potential of using CO/H 2 to reduce NO to N 2 over these REO catalysts. 相似文献
16.
In situ growth of needlelike LaAl 11O 18 grains reinforcing Al 2O 3 composites can be fabricated by a coprecipitation method using La(NO 3) 3√6H 2O and Al(NO 3) 3√9H 2O as starting materials. The new two-step process involved firstly preparing needlelike LaAl 11O 18 grains distributed homogeneously in Al 2O 3 powder and then pressureless sintering the composite powders. The Al 2O 3/25 vol.%LaAl 11O 18 samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m 1/2. 相似文献
17.
Phase changes in high temperature treated (>900 °C) 8 or 20 wt% BaO supported on γ-Al 2O 3 model lean NO x trap (LNT) catalysts, induced by NO 2 and/or H 2O adsorption, were investigated with powder X-ray diffraction (XRD), solid state 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and NO 2 temperature programmed desorption (TPD) experiments. After calcination in dry air at 1000 °C, the XRD and solid state 27Al MAS NMR results confirm that stable surface BaO and bulk BaAl 2O 4 phases are formed for 8 and 20 wt% BaO/Al 2O 3, respectively. Following NO 2 adsorption over these thermally treated samples, some evidence for nanosized Ba(NO 3) 2 particles are observed in the XRD results, although this may represent a minority phase. However, when water was added to the thermally aged samples after NO 2 exposure, the formation of bulk crystalline Ba(NO 3) 2 particles was observed in both samples. Solid state 27Al MAS NMR is shown to be a good technique for identifying the various Al species present in the materials during the processes studied here. NO 2 TPD results demonstrate a significant loss of uptake for the 20 wt% model catalysts upon thermal treatment. However, the described phase transformations upon subsequent water treatment gave rise to the partial recovery of NO x uptake, demonstrating that such a water treatment of thermally aged catalysts can provide a potential method to regenerate LNT materials. 相似文献
18.
A new aluminophosphate compound |(CH 2) 6N 4H 3·H 2O|[Al 11P 12O 48] (denoted AlPO-CJB2) with a three-dimensional open framework and an Al/P ratio of 11/12 has been synthesized solvothermally by using hexamethylenetetramine as a template. It was characterized by X-ray powder diffraction, inductively coupled plasma, elemental (CHN), and thermogravimetric analyses, and the structure was determined by single-crystal X-ray diffraction analysis. AlPO-CJB2 crystallizes in the trigonal space group R-3c with a=14.088(2) Å, c=42.199(9) Å, and Z=6. Its structure features two new kinds of cages, i.e., cage 1, 4 124 36 68 6 and cage 2, 4 126 12. The two cages alternate along the [0 0 1] direction forming an infinite column by sharing a common snowflake-like chiral motif, which is constructed from an AlO 6-centered six four-membered rings. The title compound is constructed from strictly alternating Al polyhedra (AlO 4 and AlO 6) and P tetrahedra (PO 4) via bridging oxygen atoms, and presents a new type of stoichiometry with an Al/P ratio of 11/12 in the aluminophosphate family. Computer simulation was used to determine the possible positions of the organic template within the cages. 相似文献
19.
Levyne-type zeolites were synthesized from gels of initial compositions 4.5Na 2O-6MeQI- xAl 2O 3 30SiO 2-500H 2O, with MeQ = methylquinuclidinium and 0.6 ≤ x ≥ 3 at 150 ≤ t ≥ 190 °C. The 29Si NMR spectra show the presence of two crystallographically different sites in the structure. The 27Al NMR spectra also suggest the presence of two different tetrahedral Al atoms incorporated in the structure. A rather high amount of defect groups SiOM and Si(OM) 2 with M = MeQ, Na and/or H are present in the precursor samples. The Si(OM) 2 groups are eliminated during calcination, and a certain amount of SiOM still persists after calcination. The combined 13C NMR and thermal analysis data allowed one to interpret the nature of the two different types of MeQ + ions occluded in the levyne channels. 相似文献
20.
Five cationic transition metal (ethylenediamine) complexes (M=Cr(III), Co(III), Ni(II), and Cu(II)):paramolybdate anion (Mo 7O 246−) have been synthesis and characterized via their elemental analysis, magnetic susceptibility ( μeff), thermal analysis (TG and DTA), FTIR spectra, and X-ray diffraction (XRD). The FTIR study suggests that the compounds prepared be of the ion-pair type ([M(en) n] m·Mo 7O 24). Thermal study showed that molybdenum in the Cr(III), and Co(III) compounds is reduced from oxidation state (VI) to (V) at high temperature. The stoichiometries of the resulting mixed oxides at elevated temperatures (500–750°C) are: Cr 2O 3·7MoO 2.5, Co 2O 3·7MoO 2.5, 6CoOCl·7MoO 2.5, 3NiO·7MoO 3 and 3CuO·7MoO 3. Above 750°C the molybdenum oxide in the ion-pair compounds start the sublimation process. X-ray diffraction of [Cr(en) 3]·Mo 7O 24, [Co(en) 3]·Mo 7O 24, and [Cu(en) 2(H 2O) 2] 3·Mo 7O 24 shows that these complexes are crystalline solids with a similar structure, while the [Ni(en)(H 2O) 4] 3·Mo 7O 24, and [Co(en)(H 2O) 2Cl 2] 6·Mo 7O 24 ion-pair compounds display a different structure. A novel technique based on photocatalysis to eliminate Cr(VI) ions, a toxic pollutant in the environment, was applied. The photoreduction of Cr(VI) to Cr(III) ion in aqueous suspensions using new-mixed oxides as photocatalysts (Cr2O3·MoO2.5, Co2O3·MoO2.5, NiO·MoO3, and CuO·MoO3) under air-equilibration and irradiation by a medium pressure mercury lamp (UV–VIS) was investigated. 相似文献
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