聚乙二醇对合成ZSM-5分子筛形貌影响的研究

为了探索更多具有应用价值的特殊形貌ZSM-5分子筛,本文通过在常规水热合成条件下添加晶形控制剂聚乙二醇(PEG)的方法,制得了不同形貌的ZSM-5沸石分子筛.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和红外光谱(FTIR)等手段对样品进行表征,分析表明:在晶化过程中,PEG对ZSM-5分子筛晶粒起到了晶形控制剂的作用,并且实验中PEG聚合度较小时分子筛的形貌以不规则的椭球形为主,PEG聚合度增大至45时得到的分子筛为较规则的条状结构.相同聚合度的PEG随在体系中加入量的不同对产物的形貌尺寸影响也有较大差异,在PEG量较小时分子筛有较多没有成型的小晶粒,PEG适量时为规则的条状结构.PEG量较大时大量的表面-OH使得离子之间发生空间位阻从而对分子筛晶体形貌控制作用不明显,分子筛主要为短粗的椭球形.     

介孔ZSM-5沸石的合成研究进展

介孔ZSM-5沸石具备良好的水热稳定性、形状选择性和活性,对大分子扩散有较好的扩散性能,逐渐成为催化材料研究领域的热点.本文综述了近年来介孔ZSM-5沸石的研究进展,重点介绍了介孔ZSM-5沸石的不同合成方法,包括后处理法、模板法和无介孔模板剂法,同时通过对比不同制备方法,指出各种方法的优缺点,最后对介孔ZSM-5沸石的合成与催化发展进行了展望,认为研发简单、经济和环保的新合成路线是介孔ZSM-5沸石今后的研究方向.     

ZSM-5分子筛的合成及改性研究进展

ZSM-5分子筛由于其独特的结构、物化性能、选择性和稳定性被广大研究者所关注.综述ZSM-5分子筛的合成方法,包括水热合成法、极浓体系合成法、溶剂热法、无溶剂法、限定空间法和干凝胶法,讨论了这些方法的优缺点.简述ZSM-5分子筛的改性技术和最新应用进展,最后对其发展前景进行了展望.     

On the Synthesis and Characterization of Zeolite ZSM-20

ZSM-20 is a silicon-rich analog of the faujasite-structure, the synthesis of which is complicated. Starting from known synthesis recipes its crystallization in the system Na₂O · Al₂O₃ · SiO₂ · H₂O is investigated in the presence of tetraethylammoniumhydroxyde as templating agent. The aim was to find the critical conditions for its synthesis. The synthesis products obtained are investigated by X-ray diffraction, thermal analysis and i.r. spectroscopy.     

The investigations on the synthesis of zeolite ZSM-5 (I)

The effect of the composition of reacting mixtures on the crystallinity of zeolite ZSM-5 was investigated. The mixture of ethanol and ammonia was used as a templating agent. The quantitative determination of the phase composition of the obtained preparations was made on the ground of X-ray diffraction. The ZSM-5 zeolite of ab.90% phase purity, contaminated with mordenite, quartz and amorphous material, was obtained.     

The investigations on the synthesis of zeolite ZSM-5 (II)

Physical parameters, i.e. the effect of temperature and time of crystallization on the content of zeolite ZSM-5 in the obtained preparations were investigated. Two standard reacting mixtures were tested. The mixture of ethanol and ammonia was used as a templating agent. The phase composition of the preparations was determined on the ground of the X-ray diffraction method.     

酸碱改性ZSM-5分子筛及其噻吩烷基化性能的研究

首先采用碱处理HZSM-5分子筛,然后采用不同浓度的柠檬酸酸洗碱处理后的HZSM-5分子筛,制备具有微孔-介孔多级孔HZSM-5分子筛.通过XRD、SEM、BET和NH3-TPD等表征手段对处理后催化剂进行表征,考察了碱处理后酸洗对HZSM-5分子筛孔结构性质的影响,结果表明:适当浓度的柠檬酸酸洗碱处理后的ZSM-5分子筛,能够清除掉残留在分子筛孔道内的杂质,增大了分子筛的孔径;在小型固定床反应器上,研究了改性前后分子筛的噻吩烷基化反应活性和稳定性,结果表明:碱处理后采用适当浓度的柠檬酸酸洗后,催化剂的初活性虽然低于碱改性的分子筛,但稳定性较好,更适合噻吩烷基化反应.     

Synthesis Conditions of ZSM-5-Type Zeolites

Various experiments of the synthesis of chromium-containing ZSM-5-type zeolites were carried out in correspondence to a cubus in the space of the variables of synthesis. By means of correlation coefficients, F-values, stepwise multiple linear regression and cluster analysis the dependence of goal/characterization parameters on the synthesis variables were investigated. The computations show plausible explanations of the experimental results and gave additional hints which combinations of properties of the ZSM-5-type zeolite should be possible to design in the investigated space of synthesis conditions.     

以粉煤灰为原料采用两步法制备高纯度ZSM-5型沸石的研究

采用经碱熔融-离心提取处理后的粉煤灰为原料,经水热反应研究两步法合成高纯度ZSM-5型沸石的过程,探讨了碱灰比、焙烧温度对硅铝溶出量的影响,研究了碱度、晶化时间、晶化温度与硅铝比对合成ZSM-5型沸石的影响.结果表明:碱灰比为2.3∶1,焙烧温度为680 ℃时可获得最高的硅铝溶出量;当SiO2/Na2O =7(摩尔比),SiO2/Al2O3=45(摩尔比),晶化时间为68 h,晶化温度为180 ℃时可获得高纯度的ZSM-5型沸石.     

Synthesis and Characterisation of Scandium (III)-, Yttrium (III)-, and Lanthanum (III) Violurate Complexes

Sc³⁺-, Y³⁺ -and La³⁺ violurate complexes were prepared. The isolated complexes are freely soluble in water, dilute mineral acids, MeOH, Me₂CO, DMF, DMS, partially soluble in AcOH and insoluble in EtOH, CHCl₃ and CCl₄. Molecular compositions of the complexes were formulated on the basis of elemental analysis, molar conductivity and infrared spectra. The IR spectra of violuric acid and its metal complexes reveal that bonding takes place through coordination bond between the central metal ion and the oxygen atom of the oxygen atom of the oximino (C N = O) group and convalenet bond between the central metal ion and oxygen atom of the phenolic (ketonic, C O H) group in the case of 1:2 and 1:3 complexes, and through coordination bond between the central metal ion and C O H and N H groups in the case of 2:3 complexes. All the isomorphous complexes detected by the X-ray powder patterns [the (2:3) Sc³⁺-VA and (2:3) Y³⁺-VA complexes, (1:2) Sc³⁺-VA, (1:2) Y³⁺-VA and (1:2) La³⁺-VA complexes, and the (1:3) Y³⁺-VA and (1:3) La³⁺-VA complexes] have similar X-ray, eletronic and IR spetrograms and chemical formulae. The electronic spectra in DMF and in nujol mulls characterise the octahedral stereochemistry for the investigated complexes.     

Synthesis and structure of tris(N-methylaminoethanoldithiocarbamato)arsenic(III)

The title compound was synthesized by the interaction of arsenic(III)chloride with freshly prepared N-methylaminoethanoldithiocarbamic acid in methanol. The compound crystallized in the triclinic system, space groupP with two molecules per unit cell, the dimensions area=6.509(10)Å,b=14.077(3)Å,c=14.195(3)Å, =64.16(2)^o, =84.67(2)^o and =84.00(2)^o. The molecule is monomeric with three short (mean 2.320(3)Å) and three long (mean 2.927(2)Å) As-S bonds. Asymmetry in the As-S bonds is due to the presence of stereochemically active lone pair on arsenic and the coordination polyhedron deviates from the usual D₃ symmetry to C₃ symmetry. Disorder exists in one of the dithiocarbamate ligands probably due to the O...O interaction arising from the water molecule. The anisobidenticity of the As-S bond distances is as a consequence of stereochemical requirement of the ligand and the lone pair of electrons on arsenic.     

Synthesis and Structure of Di(1,2,4,6-tetraphenylpyridinium) Octachlorodirhenate(III)

The (NC₅H₂(C₆H₅)₄)₂[Re₂Cl₈] · 2CH₃CN compound was prepared by the reaction of (n-Bu₄N)₂[Re₂Cl₈] with the 1,2,4,6-tetraphenylpyridinium tosylate in the acetonitrile; it crystallizes upon cooling of the solution at –15°C. The structure consists of the ((C₆H₅)₄C₅H₂N)⁺ cation and Re₂Cl ₈ ^2? anion with virtual D_4h symmetry. The average Re–Re and Re–Cl bond distances are 2.2205 and 2.3431 Å, respectively. In the structure, the Re₂Cl ₈ ^2? anions are disordered, such that 71.34% of the Re–Re units are aligned in one direction while 28.66% are aligned orthogonal to it. The principal crystallographic data are as follows: sp. gr. R?3; a = 26.554(1) Å, c = 23.666(1) Å; V = 14451.6(1) ų; Z = 9; D_x = 1.643 g cm^–3.     

ZSM-5预晶化时间对SAPO-34/ZSM-5复合分子筛物化性质及MTO反应的影响

采用原位两步晶化法制备了SAPO-34/ZSM-5复合分子筛,考察了SAPO-34分子筛合成体系的晶化pH,进一步研究了ZSM-5预晶化时间对SAPO-34/ZSM-5复合分子筛物化性质及MTO催化性能的影响.采用XRD、SEM、BET和NH3-TPD等手段对分子筛样品进行表征分析.结果表明,ZSM-5预晶化不同时间合成SAPO-34/ZSM-5复合分子筛的结构、形貌和催化性质有较大影响.预晶化时间为6 h制得复合分子筛SZ-ZSM-5(6 h)形成紧密的复合相结构,表现出丰富的微-介孔的多级孔分布和适宜的弱酸位和中强酸分布等特性,在MTO反应中甲醇转化率为98.4;,低碳烯烃选择性为93.4;,催化寿命达1400 min,具有较优越的催化性能.     

Synthesis,Crystal Structures and Magnetic Properties of Two Three-Dimensional Cerium(III) and Erbium(III) Coordination Polymers

Abstract  

Two lanthanide(III) coordination polymers, namely [Ce(pzdc)_1.5(H₂O)] _n (1), [Er(pzdc)(μ₂-OH)(H₂O)] _n ·nH₂O (2) (H₂pzdc = pyrazine-2,5-dicarboxylic acid), have been hydrothermally synthesized and characterized by single crystal X-ray diffraction and magnetic measurements. Polymer 1 crystallizes in triclinic space group P-1, with a = 6.2875(6), b = 6.7396(6), c = 13.3858(14) Å, α = 82.858(4), β = 83.118(4), γ = 63.452(4)°, V = 502.16(8) Å³, and Z = 2. Polymer 2 crystallizes in monoclinic space group P2(1)/c, with a = 11.706(4), b = 6.151(2), c = 14.063(5) Å, β = 92.255(3), V = 502.16(8) Å³, and Z = 4. Single-crystal X-ray diffraction studies show that compound 1 possess a 3D framework structure consisted of double chains. Compound 2 features a 3D open framework structure with a dinuclear Er(III) secondary building unit. Magnetic studies for complex 1 show stronger antiferromagnetic coupling between the Ce(III) ions.     

Synthesis and crystal structure of an unsymmetric dysprosium(III) cryptate

Synthesis, crystal and molecular structure of [Dy(H₃L)(NO₃)(H₂O)](ClO₄)₂ H₂O are reported. The complex crystallizes in the orthorhombic system, space group Pbca with lattice parameters a = 16.8036(3) Å, b = 20.9756(3) Å, c = 25.1113(4) Å, and D _calc = 1.797 Mg m^–3 for Z = 8. The coordination number of dysprosium(III) is 9, and its coordination geometry is a distorted monocapped square antiprisms. In the cryptate, a water molecule acts as a guest molecule encapsulated in the cryptate.     

Synthesis and structure of ytterbium (III) complex containing tetrachlorophthalate dianions

A novel tetrachlorophthalato-Yb(III) complex [Yb(tcph)(H₂O)₇]Htcph·H₂tcph·H₂O (1) (H₂tcph=tetrachlorophthalic acid) has been synthesized and characterized by the single crystal X-ray diffraction analysis. Colorless crystals of 1 crystallize in the triclinic space group P-1, with a=6.8504(5) ?, b=16.1921(12) ?, c=19.0123(14) ? and α=67.4470(10)°, β=86.5290(10)°, γ=81.6480(10)°, V=2.113 g/cm³ and Z=2. Unique reflections with I > 2σ(I) on refinement afford values of R ₁=0.0219 and wR ₂=0.0565.     

Synthesis and crystal structure of an unsymmetric gadolinium(III) cryptate

The synthesis and crystal and molecular structure of [Gd(H₃L)(NO₃)(H₂O)](ClO₄)₂ are reported. The complex crystallizes in the orthorhombic system, space group Pbca with lattice parameters a = 16.974(8), b = 20.010(4), c = 25.202(4) Å, and D_calc = 1.736 mg m^–3, forZ = 8. The coordination number of gadolinium (III) is nine, and its coordination geometry is a distorted monocapped square antiprisms. In the complex, three benzene rings make dihedral angles of 91.7, 92.7, 66.3°, respectively. A water molecule acts as a guest molecule encapsulated in the cryptate.     

Crystal and molecular structure ofmer-trichlorotris(pyridme)chromium(III), CrCl3(C5H5N)3

The crystal and molecular structure of 1,2,6-trichlorotris(pyridine)chromium(III) is discussed. Monoclinic crystals were indexed in the nonstandard space group, P2₁/n (No. 14). The unit cell contains four molecules:a=9.088(1) Å,b=12.442(1) Å,c=15.557(1) Å, and=91.33°;d _x=1.49 g cm^–3,d _m=1.49 g cm^–3. A total of 4056 unique reflections was recorded on a Syntex automated four-circle diffractometer usingMo K radiation. After the appropriate Lorentz and polarization corrections were made, the structure was solved by standard Patterson techniques. Least-squares refinement and difference Fourier analysis revealed all other atoms. The final agreement factors areR=0.062 andR _w=0.052. The nearly planar pyridine ring systems were found to pivot in a fan-blade arrangement about the plane described by the three nitrogen atoms and one chlorine atom. The geometry about the central chromium atom agrees with the expected octahedral configuration.     

Synthesis, spectroscopic studies, and crystal structure of tris(tetra-n-butylammonium) hexakisisothiocyanatoindate(III)

The reaction of a 1:10 molar ratio between indium chloride and tetra-n-butylammonium thiocyanate in ethanol affords the complex [(n-C₄H₉)₄N]₃[In(NCS)₆] (1), the structure of which has been established by X-ray diffraction. This compound crystallizes in the cubic space group Pa3¯ with eight formula units in the unit cell. The formula unit consists of three separate cationic tetra-n-butylammonium groups and an independent hexakisisothiocyanatoindium anionic group. The six near linear thiocyanate ligands coordinate octahedrally through the nitrogen atom to the indium metal center. The coordination of the n-butyl groups to the ammonium-nitrogen atom is tetrahedral. The complex has also been characterized by IR, ¹H and ¹³C NMR, physical properties, and X-ray powder analysis.     

Synthesis, modeling of the structure and kinetic study of the thermal decomposition of La(III) and Nd(III) complexes with 3-hydroxypicolinic acid

Synthesis, spectroscopic studies, prediction of the structure and thermal decomposition of the La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O (3-OHpic = 3-hydroxypicolinic acid) complexes are described. Elemental analysis and the IR vibrational data are consistent with the complex formulae. The absorption spectra in ethanol of the La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O show maximum absorptions at 214 and 211 nm, respectively, which are shifted to 225 nm in the free ligand. The ab initio method RHF/STO-3G/ECP(MWB52) was used to optimize the geometry and the INDO/S-CI model for calculating the electronic spectra of these complexes. A good agreement between theoretical and experimental UV absorption spectra has been obtained. The thermal decomposition was studied by non-isothermal thermogravimetry. Thermal decomposition reactions of the complexes La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O are best described by R2 and R3 kinetic models.