新型层柱化合物合成、表征及催化活性

将含过氧铌一、三取代钨硅、钨磷过氧杂多阴离子利用离子交换法嵌入Zn2Al类水滑石中制得层柱化合物,利用XRD,IR,UV等方法对产物的结构进行了表征。结果表明在层柱化合物中过氧杂多阴离子仍然保持Keggin结构,并且过氧键没被破坏。层柱化合物在酯化反应中显示优良的催化性能。     

过氧杂多阴离子型层柱化合物的合成、表征及催化活性

通过离子交换法,将含Zr过渡金属离子1,3取代钨硅、钨磷过氧杂多酸盐嵌入Zn2Al类水滑石中,获得了层柱化合物,并用XRD,IR,UV等手段对产物的结构进行了表征.结果表明过氧杂多阴离子进入水滑石层间后,水滑石的层间距从0.92增大到1.47 nm,且过氧链没被破坏.层柱化合物在酯化反应中显示优良的催化性能.     

Kinetics of acetic acid esterification with 2-ethoxyethanol over an Al-pillared clay catalyst

The Al-pillared clay catalyst obtained by exposing activated clay powder to sulfuric acid and aluminium salts and calcining in air at 373 - 673 K, was found to be highly active for the title reaction. The results indicated that pillared layer clay of the mixed oxide has been employed as parent catalysts for their definite structure and special properties which can be modified by the substitution of L and B acid sites cations. Solid acid catalyst of supported aluminium was found to be highly active and selective at the 373 - 473 K temperature range for heterogeneous esterification. The activity is mainly attributed to the Lewis (and a considerably small number of Br?nsted) acid sites whose number and strength increased due to pillaring. The water produced in the esterification can be induced by Al³⁺, which makes the catalyst surface to form strong B acid. Their acidities are obtained by pH measurement. If only B acid sites are > 70%, and pH < 1 in the 2-ethoxyethanol, there exists an activity of esterification. The used catalyst gave identical results with that of the fresh one. X-ray diffraction spectra show that the composition and active phase of the used catalysts are the same as the fresh ones. The kinetic study of the reaction was carried out by an integral method of analysis. The kinetic equation of surface esterification is y = 2.36x - 0.98. This revised version was published online in June 2006 with corrections to the Cover Date.     

Zeolite Y from kaolin clay of Kachchh,India: Synthesis,characterization and catalytic application

Kaolin clay obtained from Kachchh, Gujarat was used as alumina and silica source to synthesize zeolite Y by hydrothermal method. The synthesis route comprised of the following steps: sulfuric acid treatment at 110 ​°C (4 ​h) for impurity removal followed by calcination at 600 ​°C for 4 ​h, thermal activation of kaolin into metakaolin by NaOH fusion at 850 ​°C (8 ​h); aging of reaction mixtures at 50 ​°C (24 ​h); crystallization (24 ​h) followed by washing and drying. The synthesized zeolite Y was examined by multiple characterization techniques which revealed a pore volume of 0.22 ​cm³/g with pore size of 2.89 ​nm having essential surface area of 320 ​m²/g, indicating a porous material having majority of micropores and remaining mesopores. The zeolite exhibited good catalytic activity for succinic acid esterification using ethanol to produce monoethyl and diethyl succinate. The conversion of SA (72%) and yield (60%) of valuable diester indicated good conversion rate and selectivity at moderate reaction conditions. Detailed structural comparison with zeolite Y synthesized using standard chemical route is also carried out. This work demonstrated an effective way of preparing environmentally benign porous zeolite Y having high surface area and pore volume that can be useful for catalytic applications.     

BY分子筛的合成、表征及其裂化性能考察

采用水热晶化法合成了含杂原子硼的Y型分子筛,利用MAS NMR、XRD、IR等表征方法,证明了硼进入Y型分子筛的骨架中。利用吡啶吸附红外光谱、轻油微反装置分别测定了Y和BY分子筛的表面酸性及其裂化性能。结果表明,硼的引入增加了Y分子筛的B酸中心数目以及裂化和氢转移反应活性,导致裂化汽油中的烯烃明显降低,芳烃随之增加。     

氧化硅柱层状铁钛酸盐的合成和表征

通过先将K0.8Fe0.8Ti1.2O4与n-C6H13NH3Cl反应得到正己铵离子柱撑的层状铁钛酸盐, 然后再与NH2(CH2)3Si(OC2H5)3反应, 最后将所得产物在空气中焙烧可得到氧化硅柱层状铁钛酸盐。采用XRD, IR,TG/DTA, Mossbauer谱, X荧光分析以及比表面和孔径大小分布测定等手段对所得新材料进行了表征。结果表明: 所得二个氧化硅柱层状铁钛酸盐均具有较高的热稳定性(>650℃)和比表面(98.0m^2/g和163.8m^2/g), 平均孔径为1.82nm和1.90nm。     

规整Mn-Zn-Mg-Al-CO3四元LDHs层状材料的水热合成、结构及性能

以Mn(NO3)2.6H2O、Zn(NO3)2.6H2O、Mg(NO3)2.6H2O和Al(NO3)3.9H2O为原料,采用水热合成法,一步合成了Mn-Zn-Mg-Al-CO3四元LDHs层状材料。采用ICP、元素分析仪、XRD、FTIR、TG-DSC、SEM、低温氮吸附-脱附等对样品进行了表征。探讨了pH值、反应温度、反应时间和原料配比对Mn-Zn-Mg-Al-CO3四元LDHs层状材料合成的影响。结果表明,在pH=10、反应温度控制在140℃、反应时间为24 h的条件下,可以合成出结构规整、晶形良好、各层间排列紧密有序的含不同比例金属阳离子的Mn-Zn-Mg-Al-CO3四元LDHs层状材料。其吸附等温线符合V型吸附,H3滞后环,晶体内层间存在2 nm以上的孔,晶体内部结构的有序性高,层间碳酸根离子的排列整齐,通道内孔密度大、孔径小、比表面积大。     

Mg-Ni-Al-EDTA柱撑LDHs层状材料的水热合成、结构及性能

以Mg(NO3)2.6H2O、Ni(NO3)2.6H2O、Al(NO3)3.9H2O和[CH2N(CH2COOH)2]2为原料,采用水热合成法,合成了Mg-Ni-Al三元EDTA柱撑LDHs层状材料。采用ICP、元素分析仪、XRD、FTIR、TG-DSC、SEM等手段对样品进行了表征。探讨了pH值、反应温度、反应时间和原料配比对EDTA柱撑LDHs材料合成的影响。结果表明,在pH=8、反应温度控制在140℃、反应时间为24 h时,可以合成出结构规整、晶形良好、各层间排列紧密有序的含不同比例金属阳离子的EDTA柱撑LDHs材料。Mg-Ni-Al三元EDTA柱撑LDHs层状材料通过层间EDTA对Co2+的螯合作用,可以在较短时间内吸附溶液中的Co2+,去除率在97%以上。pH值、吸附时间、吸附温度、固体投加量及初始Co2+浓度对去除率均有不同程度的影响。     

Syntheses,characterization and catalytic activity of peroxo tantalum polyoxotungstates

Peroxo-tantalum and tantalum mono-substituted tungstosilicates with the Keggin structure, K₅[-SiW₁₁Ta(O₂) O₃₉]18H₂O (1) and K₅[-SiW₁₁TaO₄₀]14H₂O (2) respectively, and peroxo-tantalum and tantalum mono-substituted tungstophosphates with the Wells–Dawson structure K₇[₂-P₂W₁₇Ta(O₂)O₆₁]16H₂O (3) and K₇[₂-P₂W₁₇TaO₆₂]14H₂O (4), respectively, were prepared by stereoselective synthesis and characterized by elemental analysis, i.r. and u.v. spectroscopy, XPS, ³¹P and ¹⁸³W n.m.r. spectroscopy, and polarography, as well as cyclic voltammetry. The presence of a peroxo group in the complexes (1) and (3) was supported by observation of an i.r. band due to the —O—O— bond at 881 cm^–1, the charge transfer bands of (²—O₂)Ta at ca. 316 and 389 nm, the O_1s binding energy at 532.0 eV and a new irreversible reduction polarographic wave at E_1/2 0.1 V, assigned to the reduction of peroxo group and which enhances the oxidant properties of the heteropoly anions. There are six lines for complex (1) and nine lines for complex (3) in the ¹⁸³W n.m.r. spectra, showing that the complex (1) has a mono-substituted Keggin structure and complex (3) has a mono-substituted ₂-Wells–Dawson structure. The catalytic activities of the complexes with respect to epoxidation of maleic acid with H₂O₂ as oxidant were examined and the best result, 83.5% yield, was obtained for [(C₄H₉)₄N]₅[-SiW₁₁Ta(O)₂O₃₉]·18H₂O.     

Preparation and characterization of PP/clay nanocomposites based on modified polypropylene and clay

X‐ray diffraction and differential scanning calorimeter (DSC) methods have been used to investigate the crystallization behavior and crystalline structure of hexamethylenediamine (HMDA)‐modified maleic‐anhydride‐grafted polypropylene/clay (PP‐g‐MA/clay) nanocomposites. These nanocomposites have been prepared by using HMDA to graft the PP‐g‐MA (designated as PP‐g‐HMA) and then mixing the PP‐g‐HMA polymer in hot xylene solution, with the organically modified montmorillonite. Both X‐ray diffraction data and transmission electron microscopy images of PP‐g‐HMA/clay nanocomposites indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into PP‐g‐HMA matrix. DSC isothermal results revealed that introducing 5 wt % of clay into the PP‐g‐HMA structure causes strongly heterogeneous nucleation, which induced a change of the crystal growth process from a three‐dimensional crystal growth to a two‐dimensional spherulitic growth. Mechanical properties of PP‐g‐HMA/clay nanocomposites performed by dynamic mechanical analysis show significant improvements in the storage modulus when compared to neat PP‐g‐HMA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3242–3254, 2005     

A comparative study of thermal decomposition behaviour of Zn-Cr,Zn-Cr-Al and Zn-Al type layered double hydroxides

Hydrolysis of ZnO in acidic pH provides a facile route for synthesis of layered double hydroxides (LDH) bearing Zn²⁺ with Cr³⁺ and Al³⁺ without having carbonate ion in the inter-layer position. The thermal decomposition of the prepared LDH show that with the increase of Cr³⁺ content in the system there is an increase in the thermal stability of the compounds. In case of Zn-Cr LDH there is a non-mass loss transition around 420°C. Segregation of parent LDH structure to a bivalent oxide and a spinel takes place in both Zn-Cr and Zn-Al LDH only at temperatures above 550°C.Authors are grateful to Director R. R. L. Jorhat for his kind permission to publish the work, as well as acknowledgement is due to Prof. Herbert Poellmann of University of Halle, Germany for some powder XRD runs. Also, acknowledgement is due to Ministry of Environment and Forests, Govt. of India for some financial assistance.     

Catechol oxidase activity of dinuclear copper(II) complexes of Robson type macrocyclic ligands: Syntheses, X-ray crystal structure, spectroscopic characterization of the adducts and kinetic studies

Five dinuclear copper(II) complexes, [Cu₂L¹(N₃)₂·2H₂O] (1), [Cu₂L²(N₃)₂·2H₂O] (2), [Cu₂L³(N₃)₂·2H₂O] (3), [Cu₂L⁴(N₃)₂·2H₂O] (4) and [Cu₂L⁵(N₃)₂·2H₂O] (5) of Robson type macrocyclic Schiff-base ligands derived from [2 + 2] condensation of 4-methyl-2,6-diformylphenol with 1,3-diaminopropane (H₂L¹), 1,2-diaminoethane (H₂L²), 1,2-diaminopropane (H₂L³), 1,2-diamino-2-methylpropane (H₂L⁴) and 1,2-diaminocyclohexane (H₂L⁵), respectively have been synthesized and characterized. Catecholase activity of those complexes using 3,5-di-tert-butylcatechol as substrate has been investigated in two solvents, methanol and acetonitrile. The role of the solvent and of the steric properties of the macrocyclic ligand of these complexes on their catecholase activity has been examined thoroughly. Acetonitrile is observed to be a better solvent than methanol as far as their catalytic activity is concerned. However, methanol reveals to be a better choice to identify the enzyme–substrate adduct. The investigation also prompted that chelate ring size does affect on the catalytic efficiency: 6-membered ring (as in H₂L¹) exhibits better activity than its 5-membered counterpart (as in H₂L²). The activity of the 5-membered counter parts also depend upon the steric factor. Moreover, the catalytic activity of the complexes is enhanced to a significant extent by increasing the bulkiness of the substituents on the backbone of macrocyclic H₂L² ligands.     

Syntheses, structures, and reactivities of heteroleptic magnesium amide thiolates

The syntheses and characterizations of a family of novel heteroleptic magnesium amide thiolates are presented. The compounds are synthesized by ligand redistribution chemistry involving reactions of equimolar amounts of magnesium amides and magnesium thiolates. Utilization of the smaller thiolates [Mg(SPh)2]n and [Mg(S-2,4,6-iPr3C6H2)2]n results in the isolation of dimeric species, [Mg(THF)(N(SiMe3)2)(mu-SR)]2 (R = Ph (1), 2,4,6-iPr3C6H2 (2)), with four-coordinate metal centers and bridging thiolate functions. The sterically more encumbered thiolate S-2,4,6-tBu3C6H2 induces the formation of the four-coordinate, monomeric species Mg(THF)2(N(SiMe3)2)(S-2,4,6-tBu3C6H2) (3)). Careful choice of reaction conditions allows the successful syntheses of pure heteroleptic compounds; however, it remains difficult to obtain the compounds in high yields, since a tendency toward product symmetrization and ligand redistribution under re-formation of the starting materials is prevalent. One of these symmetrized products is also included in this report: the dimeric, four-coordinate magnesium thiolate [Mg-(THF)(S-2,4,6-tBu3C6H2)(mu-S-2,4,6-tBu3C6H2)]2 (4), isolated as the product of the reaction between [Mg-(N(SiMe3)2)2]2 and Mg(THF)2(S-2,4,6-tBu3C6H2)2. All compounds were characterized by NMR and IR spectroscopy, elemental analyses, and X-ray crystallography. Crystal data obtained with Mo K alpha (lambda = 0.710 73 A) radiation are as follows. 1: C16H31MgNOSSi2, a = 11.2100(1) A, b = 17.4512(3) A, c = 11.2999(2) A, beta = 97.952(1) degrees, V = 2189.32(6) A3, Z = 4, monoclinic, space group P2(1)/n, R1 (all data) = 0.0934. 2: C25H49MgNOSSi2, a = 11.1691(1) A, b = 11.0578(1) A, c = 26.0671(4) A, beta = 99.906(1) degrees, V = 3171.44(6) A3, Z = 4, monoclinic, space group P2(1)/c, R1 (all data) = 0.0557. 3: C36H71MgNO3SSi2, a = 42.8293(16) A, b = 10.9737(5) A, c = 16.8305(7) A, beta = 98.755(3) degrees, V = 7818.1(6) A3, Z = 8, monoclinic, space group C2/c, R1 (all data) = 0.1331. 4: C80H132Mg2O2S4, a = 18.8806(2) A, b = 19.3850(2) A, c = 27.3012(4) A, beta = 97.250(1) degrees, V = 9912.4(2) A3, Z = 4, monoclinic, space group P2(1)/n, R1 (all data) = 0.1023.     

Thermal behaviour of synthetic pyroaurite-like anionic clay

Thermal behaviour of synthetic pyroaurite-like anionic clay with molar ratio Mg/Fe=2 was studied in the range of 60-1100°C during heating in air. TG/DTA coupled with evolved gas analysis, emanation thermal analysis (ETA), surface area measurements, XRD, IR and Mössbauer spectroscopy were used. Microstructure changes characterized by ETA were in a good agreement with the results of surface area measurements and other methods. After the thermal decomposition of the pyroaurite-like anionic clay, which took place mainly up to 400°C, a predominantly amorphous mixture of oxides is formed. A gradual crystallization of MgO (periclase) and Fe₂O₃ (maghemite) was observed at 400-700°C by XRD. The MgFe₂O₄ spinel and periclase were detected at 800-1100°C. The spinel formation was also confirmed by Mössbauer spectroscopy.     

皂石的合成、表征及其催化性能

用水热法合成了皂石,并用羟基铝低聚物与其交联制得AICLS。用XRD、~(27)Al和~(29)Si MASNMR及吡啶吸附量表征其晶相、结构和表面酸性。合成产物的结晶度很高。皂石中T—O—T片内四面体层上铝量可由合成条件控制,表明交联密度的柱间距与铝量有关。在异丙苯裂解反应中,AICLS的活性高于皂石,但活性衰减较慢;样品的催化裂化活性与探针分子可抵达的强酸中心数有关。     

Fabrication of ball clay based low-cost ceramic membrane supports and their characterization for microfiltration application

In this study, the uniaxial pressing method was employed to fabricate low-cost ceramic membrane supports using inexpensive clays for microfiltration applications. The primary precursors used to make different membrane supports (S1–S3) were Ball clay and China clay. Thermogravimetric analysis (TGA), particle size distribution (PSD), contact angle measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were performed in addition to water flux, porosity, water permeability, and average pore size measurements to characterize the membrane. SEM analysis revealed that the surface morphology of the membrane supports varies significantly depending on the raw material composition. The contact angle analysis of the supports revealed that they are hydrophilic, which is suitable for microfiltration applications. The water permeability, average pore size, and porosity of the membrane supports (S1–S3) were 4.31 × 10^?6 – 2.77 × 10^?6 m³/m²s kPa, 1.18–0.31 μm, 44–41%, respectively. Furthermore, the membranes' high pH and chlorine resistance show their suitability for use in harsh chemical cleaning. The production cost of membranes based on raw materials, pressing, and sintering was estimated to be Rs.1319/m² ($17.07), Rs. 978/m² ($12.66) and Rs. 924/m² ($11.96) for the supports S1, S2, and S3, respectively. Thus, membrane supports with low-cost clay materials are now suggested for microfiltration applications.     

Synthesis and catalytic properties of tetraorganodistannoxanes containing silicon

Three tetraorganodistannoxanes containing silicon were synthesized and their catalytic properties in esterification and acetalization were observed via the reactions of acetic acid with isoamyl alcohol and butyraldehyde with glycol. The factors affecting the reaction, such as the catalyst dosage, reaction time and solvent, etc. were discussed. The results show that the three tetraorganodistannoxanes displayed similar good catalytic activities compared to dichlorotetrabutyldistannoxane in esterification and acetalization. When the dosage of [ClBu₂SnOSn-(CH₂SiMe₃)₂Cl]₂ was 1.5% based on the mass of reactant, the yield of isoamyl acetate was 91.8% and the yield of butyraldehyde glycol acetal 94.2%. The different alkyl and bridging groups on Sn sites in the structure of tetraorganodistannoxanes showed some influence on the catalytic activities of these compounds. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24 (11): 1265–1272     

Thermal behavior of Al-, AlFe- and AlCu-pillared interlayered clays

The purified bentonite parent clay, fraction ≤; 2 mm of montmorillonite type, has been pillared by various polyhydroxy cations, Al, AlFe and AlCu, using conventional pillaring methods. The thermal behavior of PILCs was investigated by combination of X-ray diffraction (XRD), thermal analysis (DTA, TG) and low temperature N2 adsorption/desorption (LTNA). Thermal stability of Al-, AlFe- and AlCu-PILC samples was estimated after isothermal pretreatment in static air on the temperatures 300, 500, 600 and 900°C. Crucial structural changes were not registered up to 600°C, but the fine changes in interlayer surrounding and porous/microporous structure being obvious at lower temperatures, depending on the nature of the second pillaring ion. AlFe-PILC showed higher thermal stability of the texture, the AlCu-PILC having lower values and lower thermal stability concerning both overall texture and micropore surface and volume. Poorer thermal stability of AlCu-PILC sample at higher temperatures was confirmed, the presence of Cu in the system contributing to complete destruction of aluminum silicate structure, by 'extracting' aluminum in stabile spinel form. This revised version was published online in July 2006 with corrections to the Cover Date.     

Syntheses, structures and reactivities of diindenyl-coordinated diiron bridging carbene complexes

Compound [Fe₂(μ-CO)₂(CO)₂(η⁵-C₉H₇)₂] (1) reacts with aryllithium reagents, ArLi (Ar = C₆H₅, p-CH₃C₆H₄, p-CF₃C₆H₄) followed by alkylation with Et₃OBF₄ to give the diindenyl-coordinated diiron bridging alkoxycarbene complexes [Fe₂{μ-C(OC₂H₅)Ar}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (2, Ar = C₆H₅; 3, Ar = p-CH₃C₆H₄, 4, Ar = p-CF₃C₆H₄). Complex 4 reacts with HBF₄ · Et₂O at low temperature to yield cationic bridging carbyne complex [Fe₂(μ-CC₆H₄CF₃-p)(μ-CO)(CO)₂(η⁵-C₉H₇)₂]BF₄ (5). Cationic 5 reacts with NaBH₄ in THF at low temperature to afford diiron bridging arylcarbene complex [Fe₂{μ-C(H)C₆H₄CF₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (6). The reaction of 5 with NaSC₆H₄CH₃-p under the similar conditions gave the bridging arylthiocarbene complex [Fe₂{μ-C(C₆H₄CF₃-p)SC₆H₄CH₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (7). Complex 5 can also react with carbonylmetal anionic compounds Na[M(CO)₅(CN)] (M = Cr, Mo, W) to produce the diiron bridging aryl(penta-carbonylcyanometal)carbene complexes [Fe₂{μ-C(C₆H₄CF₃-p)NCM(CO)₅}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (8, M = Cr; 9, M = Mo; 10, M = W). The structures of complexes 4, 6, 7, and 10 have been established by X-ray diffraction studies.     

Characterization of the nucleophilic reactivities of thiocarboxylate, dithiocarbonate and dithiocarbamate anions

The kinetics of the reactions of thiocarboxylate and thiocarbonate anions with benzhydrylium ions have been determined in acetonitrile solution using laser-flash photolytic techniques. The second-order rate constants (k) correlate linearly with the electrophilicity parameters E of the benzhydrylium ions, as required by the correlation log k (20 °C) = s(N)(N + E) (J. Am. Chem. Soc., 2001, 123, 9500-9512), allowing us to calculate the nucleophile-specific parameters N and s(N) for these anions. With these parameters, a direct comparison of the reactivities of thiocarboxylate, dithiocarbonate and dithiocarbamate anions with other nucleophiles becomes possible.