Protein adsorption on the mesoporous molecular sieve silicate SBA-15: effects of pH and pore size

A mesoporous molecular sieve silicate, SBA-15, with three pore sizes (38.1 A, 77.3 A, and 240 A) has been synthesized using a non-ionic, tri-block copolymer as a template in a sol-gel method. The effects of synthesis conditions on the pore size and pore-size distribution of this adsorbent have been described. The adsorption of proteins on these crystalline, ordered, materials has been studied. The kinetics of adsorption and equilibrium capacity have been probed with three proteins of different dimensions. The effects of electrostatic interactions and protein size are illustrated. It has been shown that SBA-15 materials can be tailored to show size selectivity for proteins, and very high capacities (450 mg/g) can be obtained. Furthermore, the rates of adsorption are shown to be dependent on the pore size, protein structure and solution pH.     

Hydroxylation of phenol over ts-2, a titanium silicate molecular sieve

The influence of different process parameters on the hydroxylation of phenol with H₂O₂ over the titanium silicate molecular sieve TS-2 has been investigated. Apart from the primary products vis., p- and o-dihydroxybenzenes, the corresponding quinones are also formed. Higher Ti contents in the catalyst (TS-2) and higher catalyst concentrations lower the formation of the secondary oxidation products. Solvents have an influence on the relative amounts of the two dihydroxybenzenes in the product. H₂O₂ efficiency of up to 74% is obtainable at ∼ 28% phenol conversion to dihydroxybenzenes.     

Formation of small pore SAPO-44 type molecular sieve

The hydrothermal transformation of silico–aluminophosphate gel with cyclohexylamine to SAPO-44 has been examined. The hydrothermal crystallisation products of the SAPO have been investigated by X-ray diffraction, FTIR, nitrogen and water adsorption, thermogravimetric analysis, surface analysis and ²⁷Al, ³¹P, and ²⁹Si MAS NMR. Structural changes were observed in the silico–aluminophosphate gel with and without organic template and during the hydrothermal crystallisation. The silico–aluminophosphate gel converted to pure SAPO-CHA phase in 168 h at 473 K. The surface of SAPO-44 was silicon rich as compared with that of SAPO-34 and SAPO-18. The ²⁷Al MAS NMR signal of tetrahedrally coordinated Al observed in the silico–aluminophosphate gel without the organic template was changed to octa-, penta- and tetrahedrally coordinated aluminium upon the addition of the cyclohexylamine template to the SAPO gel. After 3 h of hydrothermal treatment at 473 K however, the ²⁷Al MAS NMR signals of the octahedral and pentacoordinated aluminium were removed. This was also confirmed by ³¹P and ²⁹Si MAS NMR. The tetrahedrally coordinated P and Si were detected within 3 h at 473 K. The sorption capacity and adsorption–desorption trends of the SAPO gels and the crystallisation products were found to be different. ²⁹Si MAS NMR results indicated that the percentage of Si (4Al) and its distribution were significantly affected by the crystallization period. SAPO-44 was thermally stable up to 973 K with phase change observed over the calcination temperature of 1193 K. The SAPO gels and the crystallisation products have also been investigated for their catalytic behaviour in n-hexane and ethanol conversion reactions.     

ITQ-15: the first ultralarge pore zeolite with a bi-directional pore system formed by intersecting 14- and 12-ring channels, and its catalytic implications

The pore topology of ITQ-15 zeolite consists of an ultra-large 14-ring channel that is intersected perpendicularly by a 12-ring pore; acid sites have been introduced in its framework and this unique structure shows advantages over unidirectional ultralarge pore zeolites for diffusing and reacting large molecules.     

The synthesis,characterization, and structure solution of SSZ-58: a novel two-dimensional 10-ring pore zeolite with previously unseen double 5-ring subunits

The synthesis, structure solution, and characterization of the novel zeolite SSZ-58 are described. SSZ-58 was synthesized under hydrothermal conditions using 1-butyl-1-cyclooctylpyrrolidinium cation as a structure-directing agent. The framework topology of SSZ-58 was determined with the FOCUS Fourier recycling method. SSZ-58 possesses 12 tetrahedral atoms in the asymmetric unit of its highest topological symmetry, and to date it is the most complex zeolite structure solved from powder data. Rietveld refinement of synchrotron powder X-ray diffraction data in space group Pmma confirmed the proposed model. SSZ-58 contains layers of atoms that are linked together by double five-membered rings (D5R), or 5(2)4(5) subunits, that have not been observed before in any zeolite or zeotype structures. SSZ-58 possesses a two-dimensional channel system consisting of 10-membered ring pores that intersect to form large cavities circumscribed by 12- and 16-membered ring pores.     

SAPO-34晶粒形貌对甲醇转化制低碳烯烃反应的影响

分别采用微波和水热法合成了具有片状及立方结构的SAPO-34分子筛.结果发现,片状SAPO-34分子筛晶粒厚度为130nm,比表面积为593m²/g;立方结构SAPO-34分子筛粒径为1.5-2.5μm,比表面积为708m²/g.二者具有数量相近的强酸中心,后者的弱酸位数量略少.甲醇制烯烃反应结果表明,在450℃和1.0h^-1的反应条件下,片状SAPO-34分子筛的催化寿命可达380min,乙烯选择性最高为51.77%,乙烯、丙烯及丁烯的总选择性最高为90.20%;而立方结构SAPO-34的催化寿命仅为212min,乙烯选择性最高为49.84%,乙烯、丙烯及丁烯的总选择性最高只有86.81%.这可能源于片状晶粒的扩散路径较短,抑制了低碳烯烃的进一步转化及积碳的生成,因此具有较高的低碳烯烃选择性及较长的寿命.     

Synthesis and Structure of KBGe2O6: the first chiral zeotype borogermanate with 7-ring channels

Among the known zeolite topologies, odd rings are rare with the exception of 5-ring. We report here the hydrothermal synthesis and structural characterization of a novel compound, KBGe(2)O(6), the first germanate-based zeotype material with 7-ring channels. It crystallized in the orthorhombic system, space group P2(1)2(1)2(1) (No. 19), a = 4.8037(3) A, b = 10.2063(7) A, c = 10.7402(10) A, V = 526.57(5) A(3), Z = 3. The framework topology of this compound is previous unknown with the vertex symbol 4.6.4.6.6.7(2)(vertex1), 4.6.4.6.6.7(2)(vertex2), and 6.6.6.6.6(2) x 7(2)(vertex3). It is worth noting that the structure of the compound is chiral containing helices condensed from GeO(4) tetrahedra, which arrange around 2(1) screw axes. Furthermore, the K(+) ions within the channels are mobile and can be partially ion-exchanged with Na(+) at room temperature.     

SAPO-34分子筛中多甲基苯分子与卤代甲烷偕甲基化反应的密度泛函理论研究

利用周期性密度泛函理论研究了SAPO-34分子筛催化转化卤代甲烷制取低碳烯烃反应的碳池主要成分多甲基苯分子的偕甲基化反应。氯甲烷和溴甲烷分子在SAPO-34分子筛内的吸附能分别是–18和–22 kJ/mol,由于氯和溴原子相似的电负性,氯甲烷和溴甲烷分子的吸附能并未被精确区分。以氯甲烷和溴甲烷为甲基化试剂,得到了几种多甲基苯分子的偕甲基化反应能及能垒,结果表明,六甲基苯分子(HMB)的偕甲基化反应为放热反应,而其余甲基苯分子的偕甲基化反应为吸热反应。对于上述两种甲基化试剂,体积最大的HMB均表现出最低的偕甲基化反应能垒,这可能是由于分子筛骨架与多甲基苯分子之间的静电相互作用增强了HMB的反应活性所致。     

New all-atom force field for molecular dynamics simulation of an AlPO(4)-34 molecular sieve

A force field of the triclinic framework of AlPO(4)-34, important in methanol-hydrocarbon conversion reactions, was developed using an empirical potential function. Molecular dynamics simulation of an AlPO(4)-34 triclinic framework segment of 1216 atoms, containing the template molecules isopropylamine and water, was performed with explicit consideration of atomic charges. The average RMS difference between instantaneous positions of the framework atoms during 1 ns simulation and their positions in the structure determined from single crystal X-ray diffraction was calculated, and the average structure of the flexible framework was determined. The computed Debye-Waller factors and simulated FTIR spectra are in good agreement with the experimental data. The new force field permits detailed molecular dynamics simulations of flexible, charged aluminophosphate molecular sieves which should lead to a better understanding of the catalytic processes and the crucial role played by templating molecules.     

TG and DSC investigation of the dehydration of the extra large pore aluminophosphate molecular sieve VPI-5 and related materials

The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation of VPI-5 to AlPO₄-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state³¹P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned fragments stemming from the destruction of the water triple helix assemblage. The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating rates. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Preparation,characterization, and catalytic performance of Ta-HMS mesoporous molecular sieve

Various Ta-HMS (hexagonal mesoporous silica) samples with different Ta content were hydrothermally prepared and characterized by XRD, N₂-adsorption, ICP-AES, FTIR, and UV–Vis spectroscopy. The catalytic performance of the samples was also evaluated in the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. The regularity of mesoporous structure decreases while more extraframe Ta ions are formed with increasing the Ta content. Ta-HMS with Ta/Si ratio of 0.015 shows the highest conversion and selectivity in the studied epoxidation reaction. The catalyst can be used for three times without significant activity loss.     

Synthesis and crystal structure of IM-6, a new open framework cobalt-gallium phosphate with ten- and twelve-membered pore openings

A new three-dimensional microporous cobalt-gallium phosphate, named IM-6, has been synthesized under solvothermal conditions with an N-substituted piperazine as organic template. The structure was solved by single-crystal X-ray diffraction (triclinic, P(-)1, a=9.848(20), b=12.470(32), c=12.603(28)A, alpha=63.47(16) degrees, beta=74.56(16) degrees, gamma=76.03(17) degrees). IM-6 exhibits a new framework topology. The inorganic framework is built up of MO(4) (M=Co, Ga) and PO(4) tetrahedra. It displays a two-dimensional interconnected channel system running along the [0(-)11] and [100] directions and delimited by ten- and twelve-membered ring openings, respectively.     

Synthesis and characterization of QD-3: the first organically templated aluminoborate with 11-, 12-, and 14-ring intersecting channels

QD-3, a novel aluminoborate (TETA) 2[Al 2B 10 O 20].0.25H 2O (TETA = triethylenetetramine), has been solvothermally synthesized and characterized by IR, thermogravimetric analysis, power X-ray diffraction, elemental analysis, and single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic system, space group Pna2 1 (No. 33), a = 25.9174(2) A, b = 7.4028(5) A, c = 17.013(4) A, V = 3264.2(2) A (3), and Z = 4. Its structure consists of AlO 4 tetrahedra and B 5O 10 clusters, which are interconnected and form a three-dimensional framework with large 11-, 12-, and 14-ring channels.     

Atomic force microscopy study of the molecular sieve MnAPO-50

Atomic force microscopy (AFM) imaging of MnAPO-50 reveals multiply-nucleated, elliptical terraces, oriented in registry with the facet edges with step heights ranging from one to six template repeat distances on the [100] facets and terraces with step heights ranging from one to thirty three times the c unit cell parameter on the [001] facets.     

Synthesis and characterization of the novel molecular sieve CFSAPO-1

A novel type of molecular sieve named CFSAPO-1 was synthesised hydrothermally in a system of MA(methylamine)-Al₂O₃-P₂O₅-SiO₂-H₂O at 150°C. The molar composition of reactants was: MA: Al₂O₃P₂O₅SiO₂H₂O=(0.8–1.2)1(0.8–1.2)(0.4–3)40. XRD, IR, thermoanalysis, and adsorption studies show that the original product CFSAPO-1 is transformed into a form with molecular sieve properties after calcination. The free dimension of the adsorption window of the form is 5.8–6.2 Å. There were no distinctly thermal effects on the DTA curve at 600°C and 800°C related to two transformations detected by X-ray diffraction.     

不同硅烷对HMS介孔分子筛甲基接枝的对比研究

通过气相沉积法,分别用三甲基氯硅烷(TMCS)和六甲基二硅氮烷(HMDSZ)对HMS介孔分子筛表面进行甲基接枝改性;分别采用XRD、N2-吸附、FTIR、29SiNMR和TG等手段对样品进行表征,并测定了样品的亲水性能.结果表明,两种硅烷都可以在HMS表面接枝,接枝后分子筛的介孔结构依然保持;但是,HMDSZ的接枝效果...     

新型高疏水性富含甲基Ti-HMS介孔分子筛的制备、表征和催化性能

通过共缩合和气相甲基接枝两步法制备了新型的高疏水性富含甲基的Ti-HMS介孔分子筛.采用X光衍射、N2吸附、红外光谱、硅核磁、热重、元素分析(原子发射光谱)、紫外可见光谱等手段和亲水性实验对样品进行表征,并用环己烯环氧化反应进行催化性能测试.结果表明,经过两步接枝甲基后,Ti-HMS仍保持典型的介孔结构特征,拥有较多的甲基含量和较高的疏水性,催化环己烯环氧化活性和选择性均比共缩合法(一步接枝法)Ti-HMS有所提高.     

Preparation, characterization, and catalytic performance of a novel methyl-rich Ti-HMS mesoporous molecular sieve with high hydrophobicity

A novel methyl-rich Ti-containing hexagonal mesoporous silica (Ti-HMS) molecular sieve with high hydrophobicity has been prepared by a two-step method involving co-condensation followed by vapor-phase methyl grafting. The sample was characterized by XRD, N₂ adsorption, FTIR, UV-visible and ²⁹Si NMR spectroscopies, TG, ICP-AES, and hydrophilicity measurements, and its catalytic performance was evaluated using the epoxidation of cyclohexene as a probe reaction. The Ti-HMS material retains a typical mesoporous structure and compared with a co-condensed Ti-HMS prepared in a one-step method possesses more methyl groups and higher hydrophobicity, and also exhibits better catalytic activity and selectivity.     

Co掺杂SAPO-5分子筛制备及其催化氧气氧化环己烷反应性能(英文)

环己醇和环己酮(KA油)是制备尼龙所需材料己二酸和己内酰胺的重要中间体,也可用作油漆、农药和染料等的溶剂以及染色和褪光丝的均化剂等.工业上制取KA油的方法主要为苯酚加氢法、环己烯水合法和环己烷氧化法,其中环己烷氧化法最为普遍,是非常重要的工业过程.为获得适宜的KA油选择性,工业上普遍采用Co盐为催化剂,将环己烷氧化单程转化率控制在5.0%以下,从而使得产物选择性达到70%以上.该环己烷氧化制KA油过程不仅生产效率较低,而且所用均相催化剂因分离困难而不能重复使用.因此,当前关于环己烷氧化反应催化剂的研究均是围绕多相催化剂进行.氧气选择性氧化环己烷反应因具有更高的原子经济性而逐渐成为环己烷氧化法制KA油研究中最具挑战性的课题.该反应是自由基机理,而Co~(2+),Cr~(3+),Mn~(2+)和Ce~(2+)等金属离子可以促进自由基链反应,因此含有这些金属的多相催化剂被广泛用于该反应.另一方面,AlPO-n系列分子筛由于具有特殊的孔结构和一定的表面酸性,在催化反应中显示出较大的应用潜力.如果进行杂原子掺杂,通过改变分子筛骨架的电荷平衡,可以有效提高其表面酸性.例如磷酸硅铝分子筛(SAPO-5)具有中等强度的酸性和良好的择形性,因而作为固体酸催化剂广泛用于乙醇脱水、甲醇制烯烃、丙烯聚合和苯乙烯环氧化等反应,表现出较高的选择性和良好的稳定性.本文以传统均相Co盐催化剂的多相化为出发点,制备了Co掺杂SAPO-5与分子筛催化剂(Co-SAPO-5),考察了Co掺杂量对催化剂结构、表面性质以及氧气选择性氧化环己烷反应性能的影响.结果表明,一部分Co进入分子筛骨架,同时有少量Co以氧化钻形式高度分散在SAPO-5表面.Co掺杂对SAOP-5催化剂比表面积没有显著影响,但可使其孔体积减小.相反,Co掺杂可以提高SAOP-5分子筛表面B酸性位数量和总酸量.活性测试结果表明,环己烷转化率随着Co-SAPO-5催化剂中Co含量的增加而增加,但KA油选择性在转化率高于6.3%时急剧下降.还考察了反应温度、反应时间、初始氧气压力和催化剂用量对Co-SAPO-5分子筛催化剂性能的影响,得到了最优反应条件.以Co-SAPO-5-0.2(Co/Si摩尔比为0.2)分子筛为催化剂时,KA油总收率最高可达7.8%.另外,Co-SAPO-5催化剂在环己烷氧化反应中显示出很好的稳定性,Co-SAPO-5-0.2催化剂套用6次后活性几乎没有变化.     

Influence of zirconium on the crystallization of ETS-10 molecular sieve

Summary The ETS-10 is a newly formed titano-silicate the structure of which was resolved thanks to the XRD, EDS, HREM and mass NMR. The ETS-10 is a potentially good catalyst. The aim of this research is to study the physicochemical properties of ET(Zr)S-10 obtained from a gel containing different amounts of Zr. The analyses used are XRD, thermal analysis (TG-DSC), SEM, and ²⁹Si NMR.