共查询到20条相似文献,搜索用时 31 毫秒
1.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4 S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4 S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe3+的加入促进了光生电荷的分离和H2O2的活化,超氧阴离子自由基(·O2-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O2-作用更大。 相似文献
2.
以FeCl3为铁源, 葡萄糖为碳源, 钛酸四丁酯为钛源, 采用水热法制备了磁载光催化剂Fe3O4/C/TiO2, 用TEM、EDX、VSM、XRD和IR对Fe3O4/C/TiO2的粒径、形貌和物相等进行了表征。研究了该催化剂对三氯苯酚的降解性能, 探讨了其重复使用的可能性, 用荧光光谱法推测了可能的反应机理。结果表明该材料结合了光催化与可再生的优点, 1 g·L-1 Fe3O4/C/TiO2在18 W紫外灯下, 50 min内可将三氯苯酚降解97.9%以上, 6次循环使用后降解率仍保持在95.1%, 降解过程中有羟基自由基生成。 相似文献
3.
A new procedure for the deprotection of carboxylic tert-butyl and 1-adamantyl esters, and N-Boc-amines using H2SO4 in CH2Cl2 is described. The proposed method is simple, cheap, eco-friendly and represents a valid alternative to existing ones, with special significance in large scale applications. 相似文献
4.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B(RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe... 相似文献
5.
《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》1998,1(5-6):361-368
Catalytic hydration of 2-methyl-2-propene to tert-butanol (TBA) and alkylation with methanol to methyl-tert-butyl ether (MTBE) with dodecatungstosilicic acid H4SiW12O40 as catalyst were investigated in a constant flow reactor at 40–80 °C. The catalyst is active in both reactions and exhibits high selectivities. The mechanisms of both reactions involving protonated intermediates were proposed. 相似文献
6.
磁载光催化剂Fe3O4/C/TiO2的制备及对三氯苯酚的降解 总被引:1,自引:0,他引:1
以FeCl3为铁源,葡萄糖为碳源,钛酸四丁酯为钛源,采用水热法制备了磁载光催化剂Fe3O4/C/TiO2,用TEM、EDX、VSM、XRD和IR对Fe3O4/C/TiO2的粒径、形貌和物相等进行了表征。研究了该催化剂对三氯苯酚的降解性能,探讨了其重复使用的可能性,用荧光光谱法推测了可能的反应机理。结果表明该材料结合了光催化与可再生的优点,1 g·L-1 Fe3O4/C/TiO2在18 W紫外灯下,50 min内可将三氯苯酚降解97.9%以上,6次循环使用后降解率仍保持在95.1%,降解过程中有羟基自由基生成。 相似文献
7.
Jayaraman Dessingou 《Tetrahedron letters》2005,46(46):7967-7971
The bis-{N-(2-hydroxynaphthyl-1-methylimine)} anchored 1,3-di-derivative of lower rim p-tert-butyl-calix[4]arene possessing a N2O2, N2O4 or N2O6 binding core was found to be selective for Zn(II) ions even at ?60 ppb by eliciting fluorescence-on behaviour while the other ions, viz., Ti4+, VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Mg2+, Cd2+ and Hg2+ caused no change in the fluorescence. The reaction between 1 and Zn2+ was found to be stoichiometric with the formation of a 1:1 complex; while H+ quenched the fluorescence of the complex, OH− restored it. The studies of the 1:1 isolated complexes of Zn2+, Ni2+ and Cu2+ augmented the results. 相似文献
8.
Novel p-tert-butyl thiacalix[4]arenes functionalized with hydrazide groups at the lower rim in cone, partial cone and 1,3-alternate conformations were synthesized and their receptor properties toward metal ions of p- (Al3+, Pb2+) and d- (Fe3+, Co3+, Ni2+, Cu2+, Ag+, Cd2+) elements were investigated by picrate extraction and dynamic light scattering (DLS). It was shown that the p-tert-butyl thiacalix[4]arenes functionalized with hydrazide groups are effective extractants of soft metal cations. The complex stoichiometry depended on the receptor configuration. All the p-tert-butyl thiacalix[4]arene derivatives with hydrazide fragments were able to form nanoscale aggregates but did not show self-association abilities. 相似文献
9.
FeIIFeIII2F8(H2O)2 and MnFe2F8(H2O)2, grown by hydrothermal synthesis (), crystallize in the monoclinic system with cell dimensions (Å): a = 7.609(5), b = 7.514(6), c = 7.453(4), β = 118.21(3)°; and a = 7.589(6), b = 7.503(8), c = 7.449(5), β = 118.06(3)°, and space group . The structure is related to that of . It is described in terms of perovskite type layers of Fe3+ octahedra separated by Fe2+ or Mn2+ octahedra, or in terms of shifted hexagonal bronze type layers. Both compounds present a weak ferromagnetism below TN (157 and 156 K, respectively). Mössbauer spectroscopy points to an “idle spin” behavior for FeIIFeIII2F8(H2O)2: only Fe3+ spins order at TN, while the Fe2+ spins remain paramagnetic between 157 and 35 K. Below 35 K, the hyperfine magnetic field at the Fe2+ nuclei is very weak: Hhf = 47 kOe at T = 4.2 K. For MnFe2F8(H2O)2, Mn2+ spin disorder is expected at 4.2 K. This “idle spin” behavior is due to magnetic frustration. 相似文献
10.
Liqiang Luo Yuting Zhang Fang LiXiaojing Si Yaping DingDongmei Deng Tianlin Wang 《Analytica chimica acta》2013
A series of spinel-type CoxNi1−xFe2O4 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) magnetic nanomaterials were solvothermally synthesized as enzyme mimics for the eletroctrocatalytic oxidation of H2O2. X-ray diffraction and scanning electron microscope were employed to characterize the composition, structure and morphology of the material. The electrochemical properties of spinel-type CoxNi1−xFe2O4 with different (Co/Ni) molar ratio toward H2O2 oxidation were investigated, and the results demonstrated that Co0.5Ni0.5Fe2O4 modified carbon paste electrode (Co0.5Ni0.5Fe2O4/CPE) possessed the best electrocatalytic activity for H2O2 oxidation. Under optimum conditions, the calibration curve for H2O2 determination on Co0.5Ni0.5Fe2O4/CPE was linear in a wide range of 1.0 × 10−8–1.0 × 10−3 M with low detection limit of 3.0 × 10−9 M (S/N = 3). The proposed Co0.5Ni0.5Fe2O4/CPE was also applied to the determination of H2O2 in commercial toothpastes with satisfactory results, indicating that CoxNi1−xFe2O4 is a promising hydrogen peroxidase mimics for the detection of H2O2. 相似文献
11.
In the ferrous ion, benzoic acid and xylenol orange (FBX) dosimetric system, benzoic acid (BA) increases the G(Fe3+) value. Xylenol orange (XO) controls the BA sensitized chain reaction as well as forms a complex with Fe3+. In the aerated FBX system each √H, √OH and H2O2 oxidizes 8.5, 6.6 and 7.6 Fe2+ ions, respectively; and these values respectively increase to 11.3, 7.6 and 8.6 in oxygenated solution. About 8% √OH reacts with XO and the remaining with BA. The above fractional values are due to this competition. This √OH reaction with XO oxidizes 1.8% and 2.1% ferrous ions only in aerated and oxygenated solutions, respectively. There is a competition between √H reactions with O2 and with BA, but both lead to the production of H2O2. The oxidation of Fe2+ by √OH reactions at different concentrations of H2O2 is linear with absorbed dose while the √H reactions make the oxidation of Fe2+ non-linear with dose. This is due to competition reaction of H-adduct of BA between O2 and Fe3+. 相似文献
12.
N. Suryakiran 《Tetrahedron letters》2006,47(46):8039-8042
Facile N-tert-butoxycarbonylation of amines is described by the treatment of various primary, secondary, benzylic and aryl amines with di-tert-butyl dicarbonate in the presence of catalytic amounts of La(NO3)3·6H2O under solvent-free conditions at room temperature to afford N-tert-butylcarbamates in excellent yields. 相似文献
13.
BF3·OEt2-catalyzed methyl group migration of 4-methyl-4-tert-butyldioxycyclohexadienone, which is obtained by ruthenium-catalyzed oxidation of p-cresol with tert-butyl hydroperoxide, in hexafluoro-2-propanol/toluene gave toluquinone efficiently. The reaction can be applied to the regio-selective short-step syntheses of vitamin K3 and vitamin K1 from p-cresol. 相似文献
14.
A. O. Kuzmin E. R. Savinova V. N. Parmon 《Reaction Kinetics and Catalysis Letters》1999,66(2):351-357
The partial oxidation of ethane to ethanol and acetaldehyde in the H2/O2 fuel cell under mild conditions is reported. The reaction proceeds at the carbon gasdiffusion cathode in the presence of
transition metal ions (Fe2+, Cu2+) at ambient pressure and temperature 343 K. 相似文献
15.
The structures of the two new ferrites BaLa2Fe2O7 and SrTb2Fe2O7 with tetragonal symmetry have been resolved by X-ray and neutron diffraction performed on powder samples. In both compounds the arrangement of atoms present a close resemblance with the idealized Sr3Ti2O7 structure. It consists of a packing along the c axis of two different blocks. One is formed by the adjunction of two perovskite cells and the other one by a halved rocksalt Sr(Ba)O cell. The iron cation lattice is built by infinite double layers perpendicular to the c axis with the shortest Fe3+Fe3+ distances inside the double layers much shorter than between the layers. In BaLa2Fe2O7, Ba2+ is located on a regular 12-coordinated site and La3+ in a regular 9-coordinated polyhedron. Fe3+ is surrounded by five oxygen neighbours at 1.98 Å, building a rather regular tetragonal pyramid, with a sixth oxygen at 2.25 Å. In SrTb2Fe2O7, Sr has only eight close neighbours at ~2.80 Å and four more distant at 3.15 Å. Tb3+ has seven close neighbours, six building a distorted octahedron with the largest triangular face capped by the seventh oxygen. Fe3+ again has five neighbours, but due to the lowering of the symmetry, the square pyramid has become a distorted trigonal bipyramid. 相似文献
16.
57Fe Mössbauer effect spectra have been obtained as a function of temperature for a series of Fe2O3Cr2O3 compositions in the range 0.2–75% Fe2O3. From 30% of Fe2O3 upwards, the dependence of the reduced internal magnetic field on reduced temperature, , was found to be identical with that for α-Fe2O3, indicating the persistence of Fe2O3-type ordering over this composition range. For 0.2% of 57Fe2O3 in Cr2O3, the reduced field values fall far below those for α-Fe2O3 or Cr2O3, and weak coupling of Fe3+ with Cr3+ has been inferred.A Morin transition similar to that for α-Fe2O3 was not present for samples containing 75% of Fe2O3. Quadrupole shifts ? were found to be negative and diminishing between 75 and 30% Fe2O3, and positive between 20 and 0.2%. The limiting value at lowest dilution of 0.113 ± 0.010 mm/sec corresponds to a nuclear quadrupole coupling constant e2qQ of 0.45 ± 0.04, approximately half that for α-Fe2O3. Cone angles for Fe3+ spin vectors in the spin-spiral arrangements for intermediate compositions have been derived, and are similar to, but less extreme than those deduced from neutron diffraction data. 相似文献
17.
The synthesis of tert-butyl acrylate by atom transfer radical polymerization (ATRP) is reported. This polymer was prepared using FeCl2 · 4H2O(PPh3)2 catalyst system in conjunction with methyl 2-bromopropionate as initiator, in bulk and in solution using acetone as a solvent. The addition of solvent was necessary in order to decrease the polymerization rate and to afford low polydispersity polymers. The number-average molecular weights of the resulting polymers increased in direct proportion to the monomer conversion, and the polydispersities (Mw/Mn) were as low as 1.2. In addition, the preparation of an AB diblock copolymer of poly (n-butyl methacrylate)-block-poly (tert-butyl acrylate) by ATRP is reported. The resulting polymers and copolymers were characterized by means of size exclusion chromatography and 1H-NMR Spectroscopy. 相似文献
18.
Thermal degradation of a mixed-valence oxalate based molecular material {N(n-C4H9)4[FeIIFeIII(C2O4)3]}?? was investigated by thermogravimetric (TG) analysis. Considering the mass loss at each step of TG profile, possible step-wise thermal degradation reaction pathways of the precursor material are proposed which indicate the formation of hematite and magnetite as the solid end product of the degradation reaction. The IR spectroscopy and powder X-ray diffraction (XRD) studies of the thermally degraded samples supplement the proposed reaction pathways. 相似文献
19.
以质子化层状钙钛矿氧化物H1.9K0.3La0.5Bi0.1Ta2O7 (HKLBT)作为产氢催化剂, Pt/WO3作为产氧催化材料进行Z 型体系下完全分解水反应. 考察了不同载流子传递介质及不同载流子浓度对反应活性的影响. 结果表明, 以Fe2+/Fe3+为载流子传递介质时可以实现水的完全分解(H2/O2体积比为2:1), 8 mmol·L-1的FeCl3作为初始载流子传递介质时, 产氢、产氧活性分别为66.8和31.8 μmol·h-1, 氢氧体积比为2.1:1. 受光催化材料对载流子传递介质氧化还原速度的限制, 过高的载流子传递介质浓度并不能提高光催化活性. 相似文献
20.
《Journal of mass spectrometry : JMS》2018,53(8):717-724
On‐surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe2+/H2O2) and Fenton‐like (Mn+/H2O2; Mn+ = Fe3+, Co2+, Cu2+, Mn2+) systems was investigated by using paper spray ionization mass spectrometry (PS‐MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS‐MS analyzes). The results indicated the following order in the rates of such reactions: Fe2+/H2O2 ≫ H2O2 ≫ Cu2+/H2O2 > Mn+/H2O2 (Mn+ = Fe3+, Co2+, Mn2+) ~ Mn+ (Mn+ = Fe2+, Fe3+, Co2+, Cu2+, Mn2). The superior capability of Fe2+/H2O2 in causing the degradation of sildenafil indicates that Fe2+ efficiently decomposes H2O2 to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H2O2 can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe3+, Co2+, Cu2+, and Mn2+. A unique oxidation by‐product was detected in the reaction between Fe2+/H2O2 with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on‐surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS‐MS shows to be a convenient platform to promptly monitor on‐surface oxidation reactions. 相似文献