Synthesis,characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using co-templates of gemini surfactant [C₁₈H₃₇N(CH₃)₂(CH₂)₃-N(CH₃)₂C₁₈H₃₇]²⁺ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 ?. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520–600 cm⁻¹ in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N₂ adsorption data showed that the material had a much higher specific surface area (1 200 m²/g) than the conventional MCM-48(1 100 m²/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(1): 105–108 [译自: 燃料化学学报]     

Synthesis of ordered small pore mesoporous silicates with tailorable pore structures and sizes by polyoxyethylene alkyl amine surfactant

Ordered mesoporous silicates with tailorable pore structures and small pore sizes have been synthesized by using polyoxyethylene alkyl amine surfactant PN-430 [CH₃(CH₂)₁₇N(EO)_x(EO)_y, x + y = 5] as a structure-directing agent under acidic condition. Two-dimensional (2-D) hexagonal (p6mm) mesoporous silicates have been prepared via an evaporation-induced self-assembly (EISA) process. The N₂ sorption isotherms show that the product has a small uniform pore size distribution of 1.8 nm by BJH model, a BET surface area of 730 m²/g and a pore volume of 0.36 cm³/g. 3-D cubic (Pm-3n) mesoporous silicate with small uniform pore size (1.76 nm) can also be prepared at high concentration of PN-430 by EISA method in tetrahydrofuran solvent. The solvothermal post-treatment by n-hexane at 70 °C for 3 d to the above material results in the phase transition of the mesostructure from Pm-3n to P6₃/mmc based on XRD and TEM analyses. In comparison, by using nonionic oligometric alkyl-ethylene oxide surfactant such as Brij 78 (C₁₈H₃₇EO₂₀) or Triton X-100 (CH₃C(CH₃)₂CH₂C(CH₃)₂C₆H₄ EO₁₀) as co-templates, high-quality hexagonal (p6mm) small pore mesoporous silicates have also been prepared in ethanol media. Our results show that the blend templates composed of PN-430 and a small amount of nonionic surfactant can increase the efficiency of organic and inorganic hybrid species assembly, improve the quality of the structural regularity, and decrease the pore size to about 1.65 nm.     

Formation of Pd nanoparticles in surfactant-mesoporous silica composites and surfactant solutions

Highly dispersed palladium nanoparticles containing mesoporous silicas MCM-41 and MCM-48 were prepared by one-pot synthesis. The method consists of the simultaneous formation of CTA⁺ surfactant templating MCM-41 mesophase and CTA⁺ micelle-capped PdO, which was reduced by hydrogen to Pd metal with particle size ≈ 2 nm and was observed to stay inside the mesochannels of MCM-41 (pore size ≈ 3.8 nm) by TEM, XAS, and PXRD. During hydrothermal synthesis of Pd/MCM-48, Pd nanoparticles of average size ≈ 6–7 nm were deposited on the MCM-48 of pore size = 4 nm. The deposition is probably derived from ethanol reduction of Pd(II) complex generated from PdCl₂ precursor by hydrolysis of TEOS and C₁₂H₂₅(OCH₂CH₂)₄OH surfactant. The formation of Pd(0) from Pd(II) species in solid mesoporous silicas by hydrogen reduction was monitored by in situ XAS, and compared with the formation of Pd(0) from [PdCl₄]²⁻, [PdCl₃(H₂O)], and Pd(OH)₂ by sodium dodecyl sulfate surfactant and alcohol reduction in aqueous solutions.     

Zeolite synthesis in the presence of flexible diquaternary alkylammonium ions (C2H5)3N(CH2)nN(C2H5)3 with n=3–10 as structure-directing agents

The use of flexible diquaternary alkylammonium ions (C₂H₅)₃N⁺(CH₂)_nN⁺(C₂H₅)₃ (Et₆-diquat-n with n=3–10) as structure-directing agents for zeolite synthesis in the presence of alkali metal cation is described. Among the organic structure-directing agents studied here, a considerable diversity in the phase selectivity was observed only for the Et₆-diquat-5 ion: this cation can produce five different zeolite structures (i.e., P1, SSZ-16, SUZ-4, ZSM-57, and mordenite), depending on the oxide composition of synthesis mixtures. Analysis of the variable-temperature ¹H CRAMPS NMR spectra obtained from the Et₆-diquat-5 molecules in these five zeolites reveals that the host–guest interactions occurring within the respective materials maintain in a manner different from one another even at 160 °C at which the zeolite hosts crystallize.     

(CH3CH[NH3]CH2NH3)1/2·ZnPO4, a zincophosphate analogue of aluminosilicate zeolite thomsonite

The synthesis and structure of (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, an organically templated zincophosphate (ZnPO) analogue of aluminosilicate zeolite thomsonite (THO), are described. The ZnPO framework is built up from an alternating, vertex-sharing, network of ZnO₄ and PO₄ groups (d_av(Zn–O)=1.944 (8) Å, d_av(P–O)=1.535 (9) Å, θ_av(Zn–O–P)=130.5°) involving distinctive 4=1 secondary building units. The 1,2-diammonium propane cations are highly disordered in the [0 0 1] 8-ring channels. Crystal data: (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, M_r=198.42, orthorhombic, space group Pncn (no. 52), a=14.119 (6) Å, b=14.136 (5) Å, c=12.985 (5) Å, V=2591 (3) ų, Z=10, R(F)=0.057, R_w(F)=0.061 (for a twinned crystal).     

Zn/Cu单晶转换MOF材料的CO2/CH4分离性能研究

CO₂的捕获和分离具有重要的工业和环境意义。采用溶剂热法,以羧基和路易斯碱位点功能修饰的配体和锌离子构筑了阴离子型金属有机框架材料{[Zn₂(N)·(DMF)₃·(CH₃)₂NH₂]·(DMF)₂}_n (NEM-7-Zn)。为了提高骨架的稳定性,通过金属离子置换工艺,将NEM-7-Zn转化为高稳定性的铜基框架材料NEM-7-Cu。采用EA、PXRD、TGA及比表面积分析等技术对多孔材料进行综合表征,并测定了NEM-7-Cu对二氧化碳、乙炔和甲烷单组分气体的吸附等温线。实验结果表明,NEM-7-Cu不仅具有较高的CO₂ 吸附性能（74 cm³·g^-1）,更表现出优异的CO₂/CH₄（11.5）和C₂H₂/CH₄（7.1）吸附选择性。通过巨正则Monte Carlo方法（GCMC）计算得到CO₂在NEM-7-Cu中的主要吸附位点为功能基团羧基与路易斯碱位点附近以及Cu的金属团簇附近。     

Structural and Optical Properties of Barium Strontium Titanate (Ba0.5Sr0.5TiO3) Thin Films

Ferroelectric Barium Strontium Titanate (Ba_0.5Sr_0.5TiO₃) or BST thin films on quartz substrates have been prepared by using a modified sol gel processing technique. The starting materials are Barium 2-ethylhexanoate Ba[CH₃(CH₂)₃CH(C₂H₅)CO₂]_2, Strontium 2-ethylhexanoate Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂ and Titanium(IV) isopropoxide [TiOCH(CH₃)₂]₄. The precursors except [TiOCH(CH₃)₂]₄ were synthesized in the laboratory. Transparent and crack-free films were fabricated on quartz substrates by spin coating. The as-fired films were found to be amorphous, which crystallized to cubic phase after annealing at 550°C in air for 1 hr. In this paper we report the structural and optical properties of BST films prepared by the modified sol-gel process.

Communicated by Prof. E. C. Subbarao     

CH4/C2H6/C3H8在MOF-505@5GO上吸附相平衡和选择性

应用溶剂热法合成了不同氧化石墨烯（GO）负载量的MOF-505@GO复合材料,分别采用全自动表面积吸附仪、P-XRD、SEM和Raman对材料进行了性能表征,测定了CH₄、C₂H₆和C₃H₈在MOF-505@GO上的吸附等温线,并进行Langmuir-Freundlich方程拟合,依据IAST理论模型计算了C₂H₆/CH₄和C₃H₈/CH₄二元混合气在MOF-505@5GO上的吸附选择性。研究结果表明,随着GO负载量增大,MOF-505@GO复合材料的孔容及BET比表面积先增大后减小,当GO负载量为5%（质量）时,复合材料MOF-505@5GO的孔容及BET比表面积达到最大,当GO负载量进一步增大至8%（质量）和10%（质量）时,复合材料的孔容及BET比表面积逐渐降低。在0.1 MPa和298 K条件下,MOF-505@5GO对CH₄、C₂H₆和C₃H₈的吸附容量分别为0.88、4.81和5.17 mmol·g^-1,相比MOF-505分别提高了14.9%、30.7%和13.1%。MOF-505@5GO对C₂H₆/CH₄和C₃H₈/CH₄的吸附选择性分别为40.1和3056.1,其对C₂H₆/CH₄和C₃H₈/CH₄具有极高的吸附选择性。     

Phase transitions in R2 SnCl6-type crystals (R = NH3 C2H3, NH3C2H5 and N(CH3)4)

The thermal dilatation in (NH₃ ·CH₃) SnCl₆, (NH₃ · C₂H₅) SnCl₆ and [N(CH₃)] SnCl₆ was measured, and as the results it has turned out that (NH₃ ⁶·C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnCl₆ undergo the first order transitions at 128 K and 158 K, respectively. The low temperature phases of (NH · C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnC1₆ are found to be monoclinic and tetragonal, respectively, No phase transition was observed in (NH₃ ·CH₃)₂ SnCl₆ down to 77 K.     

L-精氨酸衍生物的合成及其性质研究

以L-精氨酸(L-Arginine)和香兰素(Vanillin)为原料,首先合成新型的具有手性的希夫碱配体L(C_(14)H_(14)KN_3O_4),其次配体L分别与金属盐(CH_3COO)_2Ni·2H_2O、BaCl_2、(CH_3COO)_2Zn·2H_2O进行配位反应,得到3种新型的金属配合物(C_(16)H_(19)ZnKN_3O_7、C_(14)H_(14)BaClKN_3O_4和C_(18)H_(20)KN_3NiO_8),目标产物用IR、荧光分光光度计和元素分析仪等表征其结构,并用紫外漫反射光谱在可见光照射下,考察了配体L和3种新型的金属配位化合物的催化性能。实验结果推测配体L和L金属配合物均具有光催化性质,L金属配合物的催化性能更强。     

低碳烷烃烯烃在超微孔柔性Cu(Qc)2上的吸附行为

采用实验研究与分子模拟相结合的方法研究了低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附热力学、动力学和吸附分离机理。用常温合成方法制备了超微孔金属-有机骨架材料Cu(Qc)₂,测定了低碳烷烃烯烃（CH₄/C₂H₄/C₂H₆/C₃H₆/C₃H₈）在Cu(Qc)₂上的吸附相平衡和吸附动力学。使用Materials Studio中的Fortcite模块模拟低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附机理以及材料的结构形变。结果表明Cu(Qc)₂具有优良的C₂H₆ /C₂H₄吸附选择性和吸附动力学,而对C₃H₈ /C₃H₆的吸附选择性很低。273 K和0.1 MPa下,C₂H₆/C₂H₄在Cu(Qc)₂上的IAST选择性达4.6。298 K和0.05 MPa下C₂H₆/C₂H₄在Cu(Qc)₂上的扩散时间常数分别达1.42×10^-3和1.48×10^-3_{s^-1,扩散活化能分别为16.62 和16.43 kJ/mol。应用装填Cu(Qc)2的固定床可在常温条件下实现C2H6 /C2H4二元混合气的完全分离。模拟结果显示Cu(Qc)2为二维堆叠结构,材料会由于吸附不同分子而发生不同程度的结构形变。甲烷易从变大的层间扩散脱附,导致其在材料上的吸附量很低;C2H6/C2H4两者都能稳定吸附在层中的孔道中,其分离推动力主要来源于两种气体在材料上明显的吸附热差异;C3H8/C3H6会分别吸附在两种不同的环境,吸附热差异小导致Cu(Qc)2对C3H8 /C3H6的吸附选择性低。}     

Poly(ethylene oxide)–LiX rubbery electrolytes with X–X disulfonamide anions having two or three ether groups in their structures

This work deals with poly(ethylene oxide), PEO–MX (M=Li, K and Cs) amorphous electrolytes with ⁻X–X⁻, [CF₃SO₂NCH₂(CH₂OCH₂)₂CH₂NSO₂CF₃]²⁻ (EDSA) and [CF₃SO₂NCH₂CH₂(CH₂OCH₂)₃CH₂CH₂NSO₂CF₃]²⁻ (TTSA) disulfonamide anions. These dianions have X⁻ end-groups identical to anions [CF₃SO₂N(CH₂)₂OCH₃]⁻ (MESA) and [CF₃SO₂N(CH₂)₃OCH₃]⁻ (MPSA), one of which (MPSA) was reported to yield chelate-like associated species (presumably LiX₂⁻ triplets) at concentrations above EO/Li=20 in PEO. This feature of LiMPSA, evidenced through glass transition temperature (T_g) measurements, does not apply to Li₂EDSA and Li₂TTSA. Though none of these lithium salts form crystalline intermediate compounds with PEO, the limit of solubility of LiMESA (EO/Li=16) does not allow a clarification of this point for this salt. At lower concentrations, however, a conductivity comparison with the potassium and caesium salts shows that the apparent degree of dissociation (=C_Li+/C_Li) of LiMESA is comparable to that of LiMPSA. As opposed to both these salts and to some extent to Li₂EDSA, a much greater dissociation takes place for Li₂TTSA, the anion of which contains an inner, third ether group in its structure.     

Boosting selective C2H2/CH4, C2H4/CH4 and CO2/CH4 adsorption performance via 1,2,3-triazole functionalized triazine-based porous organic polymers

Nitrogen-rich porous organic polymers have shown great potentials in gas adsorption/separation, photocatalysis, electrochemistry, sensing and so on. Herein, 1,2,3-triazole functionalized triazine-based porous organic polymers (TT-POPs) have been synthesized by the copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) polymerization reactions of 1,3,5-tris(4-azidophenyl)-triazine with 1,4-diacetylene benzene and 1,3,5-triacetylenebenzene, respectively. The characterizations of N₂ adsorption at 77 K show TT-POPs possess permanent porosity with BET surface areas of 666 m²·g^-1 (TT-POP-1) and 406 m²·g^-1 (TT-POP-2). The adsorption capacities of TT-POPs for CO₂, CH₄, C₂H₂ and C₂H₄, as well as the selective separation abilities of CO₂/N₂, CO₂/CH₄, C₂H₂/CH₄ and C₂H₄/CH₄ were evaluated. The gas selective separation ratio of TT-POPs was calculated by the ideal adsorbed solution theory (IAST) method, wherein the selective separation ratios of C₂H₂/CH₄ and C₂H₄/CH₄ of TT-POP-2 was 48.4 and 13.6 (298 K, 0.1 MPa), which is comparable to other adsorbents (5.6-120.6 for C₂H₂/CH₄, 10-26 for C₂H₄/CH₄). This work shows that the 1,2,3-triazole functionalized triazine-based porous organic polymer has a good application prospect in natural gas purification.     

[C16H33N(CH3)3]3[PO4(WO3)4]催化脂肪酸甲酯环氧化性能

在无酸、无溶剂条件下,以[C₁₆H₃₃N(CH₃)₃]₃[PO₄(WO₃)₄]为反应控制相转移催化剂,研究各因素对脂肪酸甲酯(FAME)环氧化反应的影响。结果表明,水相pH对环氧化反应的影响最大,反应适宜pH为4;适宜反应条件为过氧化氢与脂肪酸甲酯中双键摩尔比为1.05:1,反应温度50～60℃,反应时间5 h。在此反应条件下催化剂循环5次不失活,产品环氧值大于4.0%,碘值小于5 g I·(100 g)^-1。并通过元素分析与红外光谱,研究了催化剂在反应过程中的变化,认为磷钨杂多阴离子的分解是导致催化剂失活的关键原因。     

Elucidation of a preparation method for copper ion-exchanged ZSM-5 samples exhibiting extremely efficient N2-adsorption at room temperature: effect of counter ions in the exchange solution

The adsorption of N₂ on a copper ion-exchanged ZSM-5 sample (CuZSM-5) prepared by ion exchange using an aqueous solution of copper propionate, Cu(C₂H₅COO)₂, was examined at room temperature by measuring the FT-IR spectra, adsorption isotherms and heat of adsorption. This sample was found to be extremely efficient in terms of N₂ adsorption with regard to both the amount and the energy (i.e., heat) of adsorption, compared with samples prepared by a conventional ion-exchange method using an aqueous solution involving Cu²⁺ and simple counter ions, Cl⁻ or NO₃⁻. To clarify the specificity of the newly-prepared sample, the ion-exchange of ZSM-5 with Cu²⁺ was carried out by employing aqueous solutions involving Cu²⁺ and various types of counter ions [propionate (C₂H₅COO⁻), acetate (CH₃COO⁻), formate (HCOO⁻), chloride (Cl⁻) and nitrate (NO₃⁻) ions]. When the ion exchange was performed by using a Cu(C₂H₅COO)₂ or Cu(CH₃COO)₂ solution, the Cu²⁺ species with propionate or acetate ligand (in the monomer state) were ion-exchanged in ZSM-5, as confirmed by the DR, EPR and FT-IR spectra for CuZSM-5. In contrast, Cu²⁺ species were present in the form of aquo-complexes in samples prepared with other solutions. This distinct difference can be ascribed to the difference in the pK_a values of the counter ions; carboxylate ions, with a high pK_a value, are inclined to form a complex with Cu²⁺. Using this newly applied Cu(C₂H₅COO)₂ solution, the present ion-exchange method has the potential to develop new effective materials that possess the specific adsorption and catalytic properties of CuZSM-5.     

Photodegradation catalyst screening by combinatorial methodology

In this work, a combinatorial methodology was developed for photodegradation catalyst screening. A fluorescence imaging detection system was designed for high throughput analysis, 1,6-hexamethylenediamine was used as the probe molecule for catalyst testing. The photodegradation activity of catalysts was evaluated by 1,6-hexamethylenediamine consumption during the photodegradation reaction. The methodology could provide reliable results. We found that pure TiO₂, ZrO₂, Nb₂O₅, MoO₃, and WO₃ did not show much activity for 1,6-hexamethylenediamine photodegradation under visible light. TiO₂ catalysts doped with different metal ions were tested. When TiO₂ was doped with Ta₂O₅, Nb₂O₅, V₂O₅, MoO₃, or WO₃, higher activity for photodegradation was observed. The doping of La³⁺, Ba²⁺, and Br⁻ to TiO₂ did not improve the catalytic activities. When doping TiO₂ with Mn²⁺, Cl⁻, Al³⁺, Cu²⁺, Fe³⁺, Na⁺, Mg²⁺, Li⁺, F⁻, Co²⁺, or K⁺, catalytic activity was lower than that of pure TiO₂. After elaborate catalysts screening, we discovered new catalysts, such as 50–70% TiO₂/0–20% WO₃/20–40% VO_2.5 and 20–30% TiO₂/30–50% MoO₃/40–60% VO_2.5 as well as 30% WO₃/20% ZrO₂/50% NbO_2.5 (synthesized from ZrCl₄, NbCl₅, and (NH₄)₅H₅[H₂(WO₄)₆]·H₂O in ethanol solution or suspension) and 60–70% WO₃/Nb₂O₅ (synthesized from WCl₆ and NbCl₅ in ethanol solution). We observed that the catalytic activity is sensitive to preparation methods and catalyst specific surface areas. When P123 (HO(CH₂CH₂O)₂₀(CH₂CH(CH₃)O)₇₀(CH₂CH₂O)₂₀H, designated EO₂₀PO₇₀EO₂₀) was used as template to synthesize mesoporous materials, the mesoporous catalysts showed higher activity than regular catalytic materials.     

含L沸石次级结构单元的介孔分子筛的合成

以极低浓度n(CTAB)∶n(SiO₂)=0.06的阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）为模板,以具有L沸石次级结构单元的溶胶为前驱体,在碱性条件下合成介孔分子筛L-MCM-41。样品的XRD、FT-IR、N₂吸附脱附和NH₃-TPD等表征结果表明,合成出的介孔分子筛是孔壁含有L沸石次级结构单元的六方晶相结构,该介孔分子筛的孔壁厚于常规水热方法合成的MCM-41的孔壁,具有较高的水热稳定性和较强的酸性。     

Towards recycling purpose: Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Converting polyethylene terephthalate (PET) wastes to its monomer and valuable chemicals via eco-friendly chemical method is still a challenge task. Previously, phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction. Here, we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling. The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value. Among them, [C₁₆H₃₃N(CH₃)₃]₃PW₁₂O₄₀ (abbreviated as [CTA]₃PW) exhibits the highest activity and the most suitable pH responsive values. Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET, but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid. Additionally, the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive [CTA]₃PW.     

One-step synthesis of hydrothermally stable cubic mesoporous aluminosilicates with a novel particle structure

Hydrothermally stable and highly ordered cubic mesoporous aluminosilicate has been successfully prepared by using a one-step synthesis route. It consists of introducing the zeolite primary building units into the walls of the material. The synthesized material was analyzed by XRD, N₂ adsorption–desorption, FT-IR, HRTEM and other techniques. The characterization results showed that the hydrothermal stability of the material was greatly improved, while the pore system remained highly ordered. The hydrothermal stability is believed to be related with a novel “core-shell” particle structure that formed during the assembling of aluminosilicate precursors with the surfactant molecules together with most zeolite primary building units into the shell.     

Supported Organometallic Catalysts for Olefin Polymerization

The concept of the basic role of the transition metal-carbon bond in the catalytic polymerization of olefins was formulated in the early stages of the study of Ziegler-Natta catalysts (see Ref. 1). In this connection, attempts to use the individual organometallic transition metal compounds as catalysts for olefin polymerization have been made regularly when such compounds were synthesized[2-10]. Polymerization of ethylene in the presence of organometallic compounds containing -CH₃[2, 3], -C₆H₅[7], -CH₂C₆H₅[5, 6], -C₃H₅[4, 10], -CH₂-C(CH₃)₃[10], and -CH₂-Si(CH₃)₃[10] as organic ligands have been reported. In some cases such compounds were considered to be “models of the active centers.” However, considering the experimental results from this point of view led to a discrepancy with the following observations: