Synthesis, characterization of bimetallic Sn-Zn-MCM41 and its catalytic performance in the hydroxylation of phenol

A series of Sn-Zn modified-MCM41 has been synthesized by direct hydrothermal method and characterized using ICP, XRD, TG/DTA, FT-IR, HRTEM and N_2-adsorption techniques. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H₂O₂. Results indicated that all the samples exhibited typical hexagonal arrangement of mesoporous structure with high surface area and the heteroatoms were probably incorporated into the framework of MCM41. Catalytic tests revealed that the bimetallic incorporated materials were effective catalysts in the hydroxylation of phenol. The conversion of phenol could be reach to 56.8% for the catalysts with Sn: Zn: Si = 2.69: 4.57: 100 (molar ratio) under the optimized reaction conditions. Moreover, the materials containing Sn and Zn exhibited higher catalytic activity than monometallic Sn and Zn modified MCM41.     

Synthesis, characterization of bimetallic Sn-Zn-MCM41 and its catalytic performance in the hydroxylation of phenol

A series of Sn-Zn modified-MCM41 has been synthesized by direct hydrothermal method and characterized using ICP, XRD, TG/DTA, FT-IR, HRTEM and N_2-adsorption techniques. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H₂O₂. Results indicated that all the samples exhibited typical hexagonal arrangement of mesoporous structure with high surface area and the heteroatoms were probably incorporated into the framework of MCM41. Catalytic tests revealed that the bimetallic incorporated materials were effective catalysts in the hydroxylation of phenol. The conversion of phenol could be reach to 56.8% for the catalysts with Sn: Zn: Si = 2.69: 4.57: 100 (molar ratio) under the optimized reaction conditions. Moreover, the materials containing Sn and Zn exhibited higher catalytic activity than monometallic Sn and Zn modified MCM41.     

Effects of fluoride ion on the formation of earthworm‐like mesoporous silica

In a strong acidic environment, ordered earthworm‐like mesoporous silica has been synthesized with CTAB templating and fluoride ion (F^?) as a counterion. The synthesized products were characterized by small‐angle X‐ray diffraction (SXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption‐desorption isotherms, and Fourier‐transform infrared spectroscopy (FTIR). The effects of F/Si mole ratio on the morphology, surface area, and the pore size of the sample were discussed. It was found that a F/Si mole ratio at 0.083 induced the formation of 3D hexagonal mesophase, whereas higher F/Si mole ratios led to the formation of 2D hexagonal mesoporous silica, the optimum molar ratio of F/Si for the formation of delicate earthworm‐like mesoporous silica was observed at 0.250. The effects of the F/Si mole ratio, surfactant chain length, acid concentration, and shear flow on morphology were also studied.     

Reactions of turpentine using Zr-MCM-41 family mesoporous molecular sieves

The mesoporous molecular sieve Zr-MCM-41 was synthesized under hydrothermal conditions. Zr-MCM-41 material was impregnated using sulfuric acid to prepare SO ₄^2-/Zr-MCM-41. The obtained materials were characterized by XRD, FT-1R, N₂ adsorption/desorption and NH₃-TPD analysis technique. The results indicated that SO ₄^2-/Zr-MCM-41 was of better mesoporous structure, long range ordering and crystallites, and that SO ₄^2-existed in the skeleton of Zr-MCM-41 and enhanced its acidity. SO₄^2-/Zr-MCM-41 were firstly used as catalyst in the esterification of terpineol. The catalytic results were compared with those obtained by using sulfuric acid (33%), HY, HZSM-5 and SO₄^2-/ZrO₂ as catalysts. It was showed that SO₄^2-/Zr-MCM-41 were not only of better catalytic activity and selectivity, but also of better regenerable performance. The effects of synthesis methods of catalysts and Si/Zr mole ratio on catalytic properties were also studied. In addition, AlCl₃ was supported on the synthesized mesoporous molecular sieves to get composite catalysts that were firstly used to catalyze the polymerization of -pinene. It was showed that the catalytic result of the composite catalyst was better than that AlCl₃ alone.*To whom correspondence should be addressed. E-mail: yushitao@elong.com     

CuO Impregnated mesoporous silica KIT-6: a simple and efficient catalyst for benzene hydroxylation by C–H activation and styrene epoxidation reactions

Copper oxide doped mesoporous KIT-6 materials were synthesized by ultrasonication as impregnation method. The highly ordered nature of mesoporous CuO-KIT-6 materials analyzed by low angle X-ray diffraction. The high surface area, pore diameter and mesoporous nature of synthesized materials were confirmed by BET surface area analysis. Si–O–Si, Si–OH and Cu–O–Si bonds in the framework of CuO-KIT-6 were verified by FTIR spectroscopy. The Cu²⁺ ← O^2? charge-transfer transitions and d–d transitions of dispersed Cu²⁺ on ordered mesoporous KIT-6 were identified by DRS UV–Vis spectroscopy. The morphology of the synthesized CuO-KIT-6 materials was analyzed by HR-SEM. The 3D ordered nature of CuO-KIT-6 confirmed by TEM analysis. The highly ordered 3D mesoporous CuO-KIT-6 materials are excellent catalyst for benzene hydroxylation reaction through C-H activation and styrene epoxidation reaction with 30 % aqueous H₂O₂. The catalyst CuO-KIT-6 itself showed a good conversion towards both reactions.     

Novel synthesis of ordered mesoporous materials Al-MCM-41 from bentonite

This paper reports the synthesis of ordered mesoporous materials Al-MCM-41 with a specific surface area of 1018 m²/g from bentonite. Pretreated bentonite was simultaneously used as silica and aluminum sources without addition of silica or aluminum reagents. Orthogonal experiments were adopted to optimize the processing parameters. The samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption measurements and Fourier transform infrared spectra (FTIR) techniques. The obtained materials were hexagonal Al-MCM-41. Calcination removed the surfactant while new bonds increased the crosslinking of the frameworks. Proper Si/Al molar ratio was critical for the formation of highly ordered mesoporous materials.     

Structural aspects of mesoporous AlPO4-5 (AFI) zeotype using microwave radiation and alumatrane precursor

A new route for preparation of mesoporous AlPO₄-5 (AFI) zeotype has been synthesized using alumatrane precursor, prepared from aluminum hydroxide and triisopropanolamine (TIS) by the oxide one pot synthesis (OOPS), via microwave technique using triethylamine (TEA) as a structure-directing agent. The influences of the reaction mixture composition, HF acid, water content and the crystallization temperature and time were investigated. The prepared materials were characterized using X-ray diffraction, SEM and BET. The results showed a mesoporous AlPO₄-5 zeotype having a uniform rod-like structure with surface area around 120–180 m²/g. The high crystallinity with narrow size distribution of crystals was obtained at a high amount of structure-directing agent (the mole ratio of TEA/Al₂O₃ = 3.5). The presence of fluorine ion retarded the nucleation and growth rate, leading to a bigger crystal size. The crystal of the AFI grew preferentially in the c-direction with the reaction time and the water content. The use of lower reaction temperature to obtain good crystalline material can be compensated by a longer reaction time.     

Zirconium incorporated micro/mesoporous silica solid acid catalysts for alkylation of <Emphasis Type="Italic">o</Emphasis>-xylene with styrene

The design of micro/mesoporous silica materials with solid acid catalysts for the catalytic reactions can inject new vitality into the development of nanostructures. In this paper, zirconium was successfully incorporated into micro/mesoporous silica by the direct hydrothermal synthesis, employing P123 and protic ionic liquid as the structure-directing agent. The physico-chemical properties of the micro/mesoporous silica-zirconia were characterized by means of X-ray scattering, N₂ gas sorption, scanning electron microscopy, transmission electron microscopy and NH₃ desorbed TPD methods. The influence of Si/Zr ratio and different calcination temperature on the acidity and catalytic properties were discussed. Also, the catalytic activities of solid acid catalysts were evaluated by the alkylation of o-xylene with styrene. The results indicate that the heteroatom of zirconium has been successfully incorporated into the structure framework and the solid acid catalysts still possess hierarchically porous structure. The prepared catalytic materials contain moderate to strong acid sites, meanwhile, the amount of strong acid sites increases with a decrease of Si/Zr ratio. The SZ-10-SO₄ ^2? (molar ratio of Si/Zr = 10) catalyst was found to be the most promising and gave the highest selectivity among all catalysts, which was due to the strong interaction between H₂SO₄ and micro/mesoporous materials in the presence of Zr, thus prevent H₂SO₄ leaching from the materials. It is worth noting that SZ-10-937 (calcined at 937 K) also has the higher yield of PXE, which maybe the enhancement of crystallization of tetragonal ZrO₂ made the strong acid sites for SZ-973 sample be more than that of the other samples with the increase of calcination temperature.     

Ordered mesoporous sulfated silica-zirconia materials with high zirconium contents in the structure

A series of mesoporous sulfated silica-zirconia materials with various Si/Zr molar ratios (2.0–5.0) have been prepared using tri-block copolymer as a template, which were characterized by X-ray diffraction, TEM, nitrogen adsorption, UV-Vis diffuse reflectance spectroscopy, infrared spectroscopy, thermal gravimetric analysis, and catalytic reactions. XRD patterns displayed that ordered mesoporous sulfated silica-zirconia materials were obtained when the molar ratio of Si/Zr was not less than 4.0 (ZrSiS-4 and ZrSiS-5). When the molar ratio of Si/Zr was less than 4.0, the samples had a separated phase of amorphous sulfated zirconia (ZrSiS-2 and ZrSiS-3). Furthermore, TEM images (ZrSiS-4 and ZrSiS-5) revealed that the mesostructure of these materials were highly ordered. N₂ adsorption (ZrSiS-4 and ZrSiS-5) exhibited typical IV adsorption isotherms and uniform pore distribution. UV-Vis reflectance and IR spectra suggested (ZrSiS-4 and ZrSiS-5) that Zr atoms were incorporated into the walls of mesoporous silica. Cracking reactions of cumene and 1,3,5-triisopropylbenzene (TIPB) showed that, the ordered mesoporous sulfated silica-zirconia materials were very active in acidic catalytic reactions, especially for the cracking of large molecules.     

X-ray photoelectron spectroscopic investigation of nanocrystalline calcium silicate hydrates synthesised by reactive milling

X-ray photoelectron spectroscopy (XPS) has been used to analyse a series of mechanochemically synthesised, nanocrystalline calcium silicate hydrates (C-S-H). The samples, with Ca/Si ratios of 0.2 to 1.5, showed structural features of C-S-H(I). XPS analysis revealed changes in the extent of silicate polymerisation. Si 2p, Ca 2p and O 1s spectra showed that, unlike for the crystalline calcium silicate hydrate phases studied previously, there was no evidence of silicate sheets (Q³) at low Ca/Si ratios. Si 2p and O 1s spectra indicated silicate depolymerisation, expressed by decreasing silicate chain length, with increasing C/S. In all spectra, peak narrowing was observed with increasing Ca/Si, indicating increased structural ordering. The rapid changes of the slope of FWHM of Si 2p, Δ_Ca-Si and Δ_NBO-BO as function of C/S ratio indicated a possible miscibility gap in the C-S-H-solid solution series between C/S 5/6 and 1. The modified Auger parameter (α′) of nanocrystalline C-S-H decreased with increasing silicate polymerisation, a trend already observed studying crystalline C-S-H. Absolute values of α′ were shifted about − 0.7 eV with respect to crystalline phases of equal C/S ratio, due to reduced crystallinity.     

Mesoporous silica MCM-41 with rod-shaped morphology: Synthesis and characterization

A new synthesis route has been established to prepare highly pure mesoporous silica material (Si-MCM-41) with rod-like morphology. To improve the stability and to bring about the long range ordering in the mesoporous material, a series of tetra-alkylammonium salts has been employed in the new procedure in addition to the surfactant, cetyl-trimethylammonium bromide. The mesoporous silica materials have been characterized by small-angle X-ray diffraction (SAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ sorption and solid state ²⁹Si NMR measurements. The XRD study revealed that an excellent long range structural ordering of mesoporous material can be achieved using tetra-butylammonium bromide as a promoter. SEM study showed that rod-shaped single crystal like particles were formed in hydrothermal synthesis. TEM study revealed the presence of hexagonal voids on the face of the rod-shaped particles while nitrogen sorption study establishes the mesoporosity of the material. A high degree of cross-linking of -Si-O-Si- networks in the mesoporous silica has been evidenced in ²⁹Si NMR study.     

Highly ordered mesoporous CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and CuFe<Subscript>2</Subscript>O<Subscript>4</Subscript> with crystalline walls

The highly ordered mesoporous CoFe₂O₄ and CuFe₂O₄ with crystalline walls can be synthesized by hard template with using mesoporous silica SBA-15 as hard template and using ferric nitrate, cobalt nitrate, and copper nitrate as metal precursors. These new mesoporous materials above have high surface areas, narrow pore size distribution, and large pore volumes, which are believed to be valuable for the potential application in the field of sensors, catalysis, message recording, magnetics, and biology. This work provides a method to fabricate the highly ordered mesoporous materials composed of multi-metal oxides with crystalline walls. The development of such versatile approach is of great significance in practical application. It can be envisaged that this established method is significantly expandable to the controlled synthesis of the mesoporous functional materials with diverse compositions.     

手性磷酸锌钠的低热固相合成及调控

对合成多孔功能材料手性磷酸锌钠的新方法进行了研究,以聚乙二醇-400 （PEG-400）为表面活性剂,Na₃PO₄·12H₂O和无机锌盐为原料,用低热固相反应一步法成功合成得到P6₁22空间群的手性NaZnPO₄·H₂O。实验考察了不同的锌盐、磷酸盐,以及不同pH值对产物的影响。结果表明, pH值起着重要的作用,其调控着产物的结构;锌盐的种类不影响产物的结构;磷酸盐的种类则通过pH值的调控作用对产物产生影响。当pH在11、7～9、5、3左右时,得到的产物分别为(1) P6₁22空间群的手性NaZnPO₄·H₂O与非手性的NaZnPO₄(OH)的混合物;(2)P6₁22空间群的手性的 NaZnPO₄·H₂O;(3)非手性的NaH(ZnPO₄)₂;(4)非手性的Zn₃(PO₄)₂·4H₂O。以PEG-400为表面活性剂,Na₃PO₄·12H₂O及无机锌盐为原料,在P/Zn=1.18（摩尔比）,pH=7～9,反应混合物于50℃陈化6 h的条件下,合成产物为手性NaZnPO₄·H₂O。     

Continuous synthesis of Zn2SiO4:Mn fine particles in supercritical water at temperatures of 400-500 °C and pressures of 30-35 MPa

Sub-micron sized Zn₂SiO₄:Mn²⁺ phosphors particles were continuously synthesized in supercritical water with a flow reactor. Colloidal silica or sodium silicate was used as the Si source. Zn and Mn sources were chosen from their nitrates, sulfates, and acetates. The syntheses were carried out at temperatures from 400 to 500 °C, at pressures from 30 to 35 MPa, at NaOH concentrations from 0.014 to 0.025 M, and for residence times from 0.025 to 0.18 s. Sodium silicate formed α- and β-Zn₂SiO₄:Mn²⁺ phases regardless of the Zn and Mn sources, while colloidal silica formed phases dependent on the type of Zn and Mn sources used in addition to the use of alkali. As the reaction temperature increased, the crystallinity of α-Zn₂SiO₄:Mn²⁺ phase increased and the Mn substitution into the Zn sites of the α-Zn₂SiO₄ phase decreased. Of the conditions studied, the most highly crystalline α-Zn₂SiO₄:Mn²⁺ was produced at a temperature of 400 °C, a pressure of 30 MPa, a NaOH concentration of 0.14 M, and a residence time of 0.13 s with Zn and Mn sulfates and colloidal silica as starting materials. The α-Zn₂SiO₄:Mn²⁺ fine particles synthesized were round in shape, had an average diameter of 268 nm, and exhibited a green-emission with a peak wavelength of 524 nm.     

Rapid Room Temperature Synthesis of Hexagonal Mesoporous Silica Using Inorganic Silicate Sources and Cationic Surfactants under Highly Acidic Conditions

The room-temperature synthesis of mesoporous silica was investigated by using cationic surfactants and inorganic Si sources, like sodium silicate and colloidal silica. Mesoporous silica analogous to the hexagonal MCM-41 could be obtained over a wide range of pH below ca. 11 within short synthesis time (3 h), when the Q⁴-state Si was absent in the Si source solution prior to mixing with an aqueous solution of cationic surfactants. It was suggested that the strongly acidic conditions (pH < 1) were favorable to give mesoporous silica materials with higher surface area and larger mesopore volume.     

The influence of the mixed alkaline earth effect on the structure and properties of (Ca,Mg)–Si–Al–O–N glasses

Alkaline earth oxynitride glasses of (Ca, Mg)–Si–Al–O–N with different CaO/(CaO + MgO) molar ratios (0, 0.25, 0.5, 0.75, and 1) were successfully prepared using the sol-gel method, and their structural compositions were characterised by Raman and FT-IR techniques. The glass dynamic properties of thermal expansion coefficient, glass transition temperature (T_g), and static properties of density, molar volume, Vickers hardness and compressive strength were systematically measured and analysed. The results showed that the static properties exhibited an overall regular change as the CaO/(CaO + MgO) ratio gradually increased, while the dynamic properties had an obvious mixed alkaline earth effect, which represented the appearance of an extreme value point in CaO/(CaO + MgO) mole ratios of 0.25 and 0.75, respectively. The typical thermal expansion coefficient and T_g of mixed alkaline earth oxynitride glasses deviated far from the linear connection between single alkaline earth oxynitride glasses. Raman spectra and infrared spectra revealed that the ratio value of the Q³/(Q²+Q⁴) decreased (Qⁿ: n = no. of bridging anions joining SiO₄ tetrahedra) in the mixed alkaline earth oxynitride glasses with increasing the amount of Ca, confirming that Ca decreased the crosslinking between individual tetrahedra via the transformation of Q³ species into Q² and Q⁴ species.     

Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay

Calcined clays can be potential supplementary cementitious materials if effects of heat-treatment on their structure and reactivity are understood. This work reports structural characterization of an interstratified illite/smectite clay, including a quartz impurity, upon heating using ²⁷Al and ²⁹Si MAS NMR spectroscopy and ICP-OES analysis. During dehydroxylation (600–900 °C) the Q³-type SiO₄ sites become disordered and octahedral AlO₆ sites transform into tetrahedral sites, resulting in an amorphous material with substantial pozzolanic properties, as demonstrated by reactivity tests and hydration studies of a Portland cement–calcined clay blend. At higher temperatures (above 950 °C), inert Q⁴-type phases crystallize which radically reduce the reactivity. At optimum calcination temperature (900 °C), the amorphous material contains highly dissolvable elemental species as seen from complementary ICP-OES analysis. The quartz impurity exhibits a unique variation in ²⁹Si spin–lattice relaxation times upon heat-treatment which is ascribed to changes in the concentration of impurity ions in quartz.     

Highly active Ti-rich ordered mesoporous titanium silicate synthesizedunder strong acidic condition

Titanium-rich highly ordered mesoporous silica has been synthesized by using unconventional Ti source TiCl₄ under strongly acidic pH condition in the presence of a cationic surfactant as supramolecular structure directing agent (SDA). The most Ti-rich sample for these mesoporous titanium silicates with two-dimensional hexagonal ordered structure was observed with Si/Ti=7.6 in the product. XRD, N₂ sorption, ²⁹Si MAS NMR, UV-vis diffuse reflectance, FT-IR spectroscopic tools, TEM and SEM image analyses were employed to characterize these materials. BET surface area and mesopore volume for all the samples were high. Strong UV-vis absorption band at 222 nm and FT-IR stretching vibration band of Si-O-Ti at were observed in these Ti-rich samples indicating the presence of titanium in isolated tetrahedral environment and strongly bound inside the mesoporous framework. These Ti-rich ordered mesoporous titanium silicate samples showed excellent catalytic activity in the epoxidation of styrene (sample 2 having Si/Ti=7.6 showed 86% conversion with ca. 85% selectivity for styrene oxide) using dilute aqueous H₂O₂ as oxidant.     

Mechanism of mechanical–chemical synergistic activation for preparation of mullite ceramics from high-alumina coal fly ash

High-alumina coal fly ash (HAFA) is a special solid waste due to the existence of more than 45% alumina and 35% silica, which can be applied to prepare Al-Si series ceramics if the impurities can be removed and the Al/Si mass ratio can exceed 2.55 (Mullite: 3Al₂O₃.2SiO₂). In this work, a new mechanical–chemical synergistic activation–desilication process is proposed, and the contents of different impurities can be lowered up to less than 1%, and the Al/Si mass ratio can be elevated from 1.26 to 2.71. Especially, the mechanism of this process is investigated in detail. The analysis of the mechanism shows that the decrease of Q⁴(3Al) and the increase of Q⁴(0Al), Q⁴(1Al), and Q⁴(2Al) improve amorphous silicate reactivity through synergistic activation, and the exposed amorphous Si-O-/Si-O-Si can be removed by OH- during the desilication process (desilicated ratio>55%), which help the fine mullite to exhibit excellent properties (bulk density > 2.85 g/cm³, apparent porosity < 0.5%) during the sintering process. Finally, this process not only decreases the pollution but also alleviates the shortage of Al/Si resources and promotes the clean development of coal-fired power generation.     

Influence of initial Si/Al ratios on the structural,acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors

Nano-ZSM-5/SBA-15 analog composites (ZSC) were prepared in a two-step process from ZSM-5 precursors with different Si/Al molar ratios (10–50) via high-temperature synthesis in mildly acidic media (200 °C, pH 3.5) aiming to evaluate the influence of the initial Si/Al ratio on their structural, acidic and catalytic properties. The resulting materials were characterized by SAXS, XRD, FTIR, TEM, N₂ sorption, ²⁷Al solid state-NMR, NH₃-TPD, FTIR spectroscopy of adsorbed pyridine, AAS and ICP-AES. Under the applied synthesis conditions, a ZSC material with controlled distribution of nano-ZSM-5 and SBA-15 analog phases can be prepared from ZSM-5 precursors by adjusting the initial Si/Al ratio in the range of 20–30. Increasing the initial Si/Al ratio to 50, only ZSM-5 nanocrystals were obtained whereas reducing the initial Si/Al ratio to 10 led to the formation of a disordered mesoporous SBA-15 analog. The total acidity increases with the crystallinity of the ZSM-5 phase as varying the Si/Al ratio from 10 to 30 despite the decreased amount of incorporated aluminum. However, the acidity declines slightly when raising the Si/Al ratio to 50 because of the low incorporated aluminum. The catalytic performance of the ZSC materials compared to the reference materials, i.e. purely mesoporous Al-SBA-15 and purely microporous H-ZSM-5 was assessed in the gas phase cracking of cumene and 1,3,5-tri-isopropylbenzene (TIPB) as test reactions. The results show that a balanced ratio of nano-ZSM-5 and SBA-15 analog phases obtained by tuning the initial Si/Al ratio is crucial to achieve superior catalytic performance of the ZSC materials in the cracking of both cumene and TIPB.