Preparation of stable mesoporous silica FSM-16 from water glass in the presence of cetylpyridium bromide

The synthesis and characterization of the mesoporous materials FSM-16 (folded sheets mesoporous materials) with highly ordered structure in open-vessel by using cetylpyridium bromide (CPBr) and the single-layered polysilica Kanemite as new template and silicon source, respectively, has been investigated systematically. The hexagonal arrangements of uniformly size pores were characterized by FTIR. XRD. nitrogen adsorption. TG-DTA. SEM and TEM. Especially, the porous products with higher surface areas show remarkable thermal stability up to 1000 C. The potential application as carrier of catalysts or host-guest materials is anticipated. (C) 2001 Elsevier Science B.V. All rights reserved.

Isobutane/butene alkylation over supported heteropoly acid catalysts: I. Influence of the structure of silica

Catalysts consisting of heteropoly acids (HPAs) supported on different silica and mesoporous molecular sieves have been prepared by impregnation and the sol-gel method, respectively, and their catalytic behavior in fixed-bed alkylation of isobutane with butene has been investigated. The activity, selectivity and stability of the supported-HPA catalysts could be correlated with the surface acidity of the catalysts, the structure of supports as well as the time on stream (TOS). In the fixed-bed reactor, the acidity of the heteropoly acid is favorable to the formation of dimerization products (C-8(=)); especially, the pore size of supports was seen to have an important effect on activity and product distribution of the catalysts. Contrary to the traditional solid-acid catalysts, the supported-HPA catalysts own an excellent stability for alkylation, which makes it possible for these supported catalysts to replace the liquid-acid catalysts used in industry.

Iron(II)-8-quinolinol/MCM-41-catalyzed phenol hydroxylation and reaction mechanism

Iron(II)-8-quinolino/MCM-41 is prepared. Its catalysis is studied in phenol hydroxylation using H2O2 (30%) as oxidant. The experiment shows that Iron(II)-8-quinolinol/MCM-41 has good catalytic activity and desired stability. Based on cyclic voltammetry, ESR, and UV-visible spectra studies of iron(II)-8-quinolinol complex in liquid phase, a radical substitution mechanism is proposed and used to demonstrate the experimental facts clearly. (C) 1997 Academic Press.

Hydroxylation of phenol by iron(II)-phenanthroline(Phen)/MCM-41 zeolite

MCM-41 zeolite and Tron (II)-Phen/MCM-41 zeolite have been prepared and characterized by XRD, IR, NH3-TPD, HET and UV-Vis. The Iron( II)-Phen/MCM-41 zeolite+30% H2O2 system is capable for catalyzing hydroxylation of phenol.

Hydroxylation of phenol by iron(II)-phenanthroline(Phen) MCM-41 zeolite

MCM-41 mesoporous molecular sieve and iron(II)-Phen/MCM-41 have been prepared and characterized by XRD, IR, NH3-TPD, BET and UV-Vis. The iron(II)-Phen/MCM-41 molecular sieve + 30% H2O2 system is capable of performing hydroxylation of phenol.

Synthesis and characterization of manganese-modified MCM-41

Manganese-modified mesoporous MCM-41 molecular sieves were synthesized at the absence of alkaline metal ions under mild alkaline condition using cetylpyridinium bromide surfactant as a template, and characterized with X-ray diffraction, N-2 adsorption, transmission electron microscopy, electron spin resonance (ESR), and nuclear magnetic resonance (NMR) spectroscopies. The synthesized MnMCM-41 has a high pore volume of 1.30 cm(3) g(-1) with a corresponding surface area of 1510 m(2) g(-1). The ESR and Si-29 MAS NMR spectra revealed the presence of framework manganese ions in either the as-synthesized or calcined forms. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis of FeCoMnAPO-5 molecular sieve and catalytic activity in cyclohexane oxidation by oxygen

A new FeCoMnAPO-5 with AFI structure was synthesized under hydrothermal conditions and characterized by XRD, FT-IR, X-ray fluorescence, nitrogen adsorption and SEM. The oxidation of cyclohexane with molecular oxygen was studied over the catalyst at 403 K. It show d higher activity compared to FeAPO-5, CoAPO-5 and MnAPO-5. The FeCoMnAPO-5 catalyst was recycled twice without loss of activity or selectivity.

Hydroisomerization of long-chain alkane over Pt/SAPO-11 catalysts synthesized from nonaqueous media

SAPO-11 molecular sieves were synthesized from nonaqueous media. The effects of Si and Al sources as well as solvents on the catalytic performance of SAPO-11 were investigated by the hydroisomerization reaction of n-dodecane. The samples were characterized by XRD, XRF, N-2-adsorption, SEM, NH3-TPD, IR-NH3 and Si-29 CP MAS NMR. The SAPO-11 samples synthesized with tetraethoxysilane as the Si source showed higher Si incorporation contents than the SAPO molecular sieves prepared with polymeric Si sources (fumed silica and Si colloidal gel). The reaction results showed that Pt/SAPO-11 catalysts synthesized from ethylene glycol and glycerol media with the monomeric Si and Al sources (tetraethoxysilane, aluminum isopropoxide) exhibited higher catalytic activities than those catalysts with the polymeric Si or Al (pseudo-boehmite) sources, due to the larger external surface area and higher acidity of the former ones. Especially, the catalyst synthesized in an ethylene glycol medium possessed the highest catalytic activity. Over this catalyst, 88% conversion of n-dodecane was achieved at a low temperature of 250 degrees C.

Meiofauna Techniques

Meiofaunal organisms are mobile multicellular animals that are smaller than macrofauna and larger than microfauna. The size boundaries of meiofauna are generally based on the standardised mesh apertures of sieves with 500 μm (or 1000 μm) as upper and 63 μm (or 42 μm) as lower limits. Meiofauna are ubiquitous, inhabiting most marine substrata, often in high densities. Meiofauna are highly diverse, and several phyla are only known to occur as meiofauna. Owing to their small size and high densities, specialised techniques are required to collect, preserve and examine meiofauna. These are described, along with approaches to determine biomass of these small animals. Their small size also makes them useful candidates for manipulative experiments, and culturing of individual species and approaches to experiments on whole communities are briefly discussed.

Meiobenthos and macrobenthos are discrete entities and not artefacts of sampling a size continuum: Comment on Bett (2013)

Species size distributions for metazoan benthic invertebrates conform to the highly conservative bimodal pattern, regardless of the sieve mesh sizes or numbers of sieves used in their extraction. This pattern is not an artefact of sampling a size continuum as suggested by computer simulations using just 2 fixed mesh sizes in Bett (2013; Mar Ecol Prog Ser 487:1-6). Meiobenthos and macrobenthos are coherent entities, each with a distinct suite of functional attributes, and should not be regarded as a single unit for ecological modelling purposes.

Zeolite Encapsulated Complexes Of Fe,Co,Ni,Cu And Pd:Synthesis , Characterization And Catalysis-2003

This thesis deals with the synthesis, characterization and catalysis activity studies of some zeolite encapsulated complexes. Encapsulation inside the zeolite cages makes the catalysts more stable. Further, the framework prevents the complexes from dimerising. Catalysis by metal complexes encapsulated in the cavities of zeolites and other molecular sieves has many features of homogeneous, heterogenous and enzymatic catalysis. Serious attempts has been made to gain product selectivity in catalysis .The catalytic activity shown by the encapsulated complexes can be correlated to the structure of the active site inside the zeolite pore. It deals with the studies on the partial oxidation of benzyl alcohol to benzaldehyde. The oxidatio was carried out using hydrogen peroxide as oxidant in presence of PdYDMG and CuYSPP as catalysts. The product (benzaldehyde) was detected using TLC and confirmed using GC.The catalytic activity of the complexes was tested for oxidation under various conditions. The operating conditions like the amount of the catalyst, reaction time, oxidant to substrate ratio, reaction temprature, and solvents have been optimized. No further oxidation products were obtained on continuing the reaction for four hours beyond the optimum time. Maximum conversion was obtained at room temperature and the percentage conversion decreased with increase in temperature. Activity was found to be dependent on the solvent used. With increasing awareness about the dangers of environmental degradation, research in chemistry is getting increasing geared to the development of “green chemistry,” by designing environmentally friendly products and processes that bring down the generation and use of hazardous substances.

Scandalous Subjects

This essay explores the problems and possibilities of the postcolonial as word and orientation, as category and entity. It sieves postcolonial expressions through critical filters to make two tasks palpable. On the one hand, faced forthwith are the scandals of the nation and the West as well as the outrage of the postcolonial itself. On the other hand, brought to the front are protocols of probing that do not merely lead to an undoing of “foundations” but point to procedures of critical affirmation embedded within a history without guarantee. Here are to be found dispositions that carefully question and prudently elaborate issues of power and difference, authority and alterity, including through critical considerations of modernity and its philosophical and historical discussions in the West.-----Este artículo explora los problemas y posibilidades de lo postcolonial en tanto que concepto y orientación, categoría y entidad. Tamiza las expresiones postcoloniales a través de los filtros de la crítica para lograr que dos tareas devengan palpables. Por una parte, a lo primero que nos enfrentamos es a los escándalos de la nación y de Occidente, así como al ultraje de lo postcolonial en sí mismo. Por otra parte, se destacan protocolos de investigación que no conducen simplemente a un menoscabo de los ‘fundamentos’ sino que apuntan a procedimientos de afirmación crítica enraizados en lo que yo llamo una historia sin garantía. Aquí se encuentran disposiciones que cuestionan de manera juiciosa y elaboran con prudencia asuntos de poder y diferencia, autoridad y alteridad y que incluyen consideraciones críticas de la modernidad y sus discusiones filosóficas e históricas en Occidente.

Synthesis, characterization and catalytic evaluation of cubic ordered mesoporous iron-silicon oxides

Iron was successfully incorporated in FDU-1 type cubic ordered mesoporous silica by a simple direct synthesis route. The (Fe/FDU-1) samples were characterized by Rutherford back-scattering spectrometry (RBS), small angle X-ray scattering (SAXS). N(2) sorption isotherm, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The resulting material presented an iron content of about 5%. Prepared at the usual acid pH of -0.3, the composite was mostly formed by amorphous silica and hematite with a quantity of Fe(2+) present in the structure. The samples prepared with adjusted pH values (2 and 3.5) were amorphous. The samples` average pore diameter was around 12.0 nm and BET specific surface area was of 680 m(2) g(-1). Although the iron-incorporated material presented larger lattice parameter, about 25 nm compared to pure FDU-1, the Fe/FDU-1 composite still maintained its cubic ordered fcc mesoporous structure before and after the template removal at 540 degrees C. The catalytic performance of Fe/FDU-1 was investigated in the catalytic oxidation of Black Remazol B dye using a catalytic ozonation process. The results indicated that Fe/FDU-1 prepared at the usual acid pH exhibited high catalytic activity in the mineralization of this pollutant when compared to the pure FDU-1. Fe(2)O(3) and Fe/FDU-1 prepared with higher pH of 2 and 3.5. (C) 2010 Elsevier B.V. All rights reserved.

Immobilization of glucose oxidase enzyme (GOD) in large pore ordered mesoporous cage-like FDU-1 silica

Large pore ordered mesoporous silica FDU-1 with three-dimensional (3D) face-centered cubic, Fm3m arrangement of rnesopores, was synthesized under strong acid media using B-50-6600 poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) triblock copolymer (EO(39)BO(47)EO(39)), tetraethyl orthosilicate (TEOS) and trimethyl-benzene (TMB). Large pore FDU-1 silica was obtained by using the following gel composition 1TEOS:0.00735B50-6600:0.00735TMB:6HCl:155H(2)O. The pristine material exhibited a BET specific surface area of 684 m(2) g(-1), total pore volume of 0.89 cm(3) g(-1), external surface area of 49 m(2) g(-1) and microporous volume of 0.09 cm(3) g(-1). The enzyme activity was determined by the Flow Injection Analysis-Chemiluminescence (FIA-CL) method. For GOD immobilized on the FDU-1 silica, GOD supernatant and GOD solution, the FIA-CL results were 9.0, 18.6 and 34.0 U, respectively. The value obtained for the activity of the GOD solution with FIA-CL method is in agreement with the 35 U, obtained by spectrophotometry. (C) 2011 Elsevier B.V. All rights reserved.

Adsorption of Pb(2+), Cu(2+) and Cd(2+) in FDU-1 silica and FDU-1 silica modified with humic acid

Ordered mesoporous silica with cubic structure, type FDU-1, was synthesized under strong acid media using B-50-6600 poly(ethylene oxide)-poly(butilene oxide)-poly(ethylene oxide) triblock copolymer (EO(39)BO(47)EO(39)) and tetraethyl orthosilicate (TEOS). Humic acid (HA) was modified to the synthesis process at a concentration of 1.5 mmol per gram of SiO(2). Thermogravimetry, small angle X-ray diffraction, nitrogen adsorption and high resolution transmission electron microscopy were used to characterize the samples. The pristine FDU-1 and FDU-1 with incorporated 1.5 mmol of HA were tested for adsorption of Pb(2+), Cu(2+) and Cd(2+) in aqueous solution. Incorporation of humic acid into the FDU-1 silica afforded an adsorbent with strong affinity for Cd(2+), Cu(2+) and Pb(2+) from single ion solutions. Adsorption of Cu(2+) was significantly enhanced after incorporation of humic acid, a fact that can be explained by the formation of complexes with carboxylic and phenolic groups at low concentrations of the metal cation. The results demonstrated the potential applicability of FDU-1 with incorporated HA in the removal of low concentrations of heavy metal cations from aqueous solution, such as wastewaters, after usual precipitation of metal hydroxides in alkaline medium and proper pH conditioning in the range between 6 and 7. (C) 2007 Elsevier Inc. All rights reserved.