Synthesis And Characterization Of Niobium Modified Montmorillonite And Its Use In The Acid-catalyzed Synthesis Of β-hydroxyethers

Montmorillonite K10 was ion-exchanged with polyhydroxyniobium obtained from niobium pentachloride by hydrolysis. This modified clay was characterized by X-ray diffraction, thermogravimetric analysis, inductively coupled plasma emission (ICP-OES) and nitrogen adsorption/desorption. The obtained material was used in the alcoholysis of epoxidized methyl oleate with methanol, leading to β-hydroxyethers. The reaction with ion-exchanged montmorillonite (Nb-Mont) was four times faster at 60 °C and three times faster under reflux than the one using the original clay. This proves the increase of Brønsted acidity when polyhydroxyniobium is present. The Nb-Mont was also calcined at 300, 500 and 900 °C to obtain the Nb-pillared montmorillonite. However, the activity of the calcined Nb-Mont decreased with increasing calcination temperature. On the other hand, calcined montmorillonite maintained its basal distance, even after treatment at 900 °C. © 2006 Elsevier B.V. All rights reserved.31101/02/15199203Bergaya, F., Lagaly, G., (2001) Appl. Clay Sci., 19, p. 1Vaccari, A., (1998) Catal. Today, 41, p. 53Laszlo, P., (1987) Science, 235, p. 1473Lagaly, G., Ziesmer, S., (2003) Adv. Colloid Interface Sci., 105, p. 100Yahiaoui, A., Belbachir, M., Hachemaoui, A., (2003) Int. J. Mol. Sci., 4, p. 548Fripiat, J.J., Gastuche, M.C., Richard, R.B., (1962) J. Phys. Chem., 66, p. 806Rios, L.A., Weckes, P.P., Schuster, H., Hausmann, H., Hölderich, W.F., (2003) Appl. Catal. A: Gen., 253, p. 487Gautier, E.C.L., Graham, A.E., McKillop, A., Standen, S.P., Taylor, R.J.K., (1997) Tetrahedron Lett., 38, p. 1881Loh, T.P., Li, X.R., (1999) Tetrahedron, 55, p. 10789Bahulayan, D., Das, S.K., Iqbal, J., (2003) J. Org. Chem., 68, p. 5735Iqbal, Z., Jackson, A.H., Rao, K.R.N., (1988) Tetrahedron Lett., 29, p. 2577Poupaert, J.H., Bukuru, J., Gozzo, A., (1999) Monatsh. Chem., 130, p. 929Singh, D.U., Singh, P.R., Samant, S.D., (2004) Tetrahedron Lett., 45, p. 4805Shinde, A.B., Shrigadi, N.B., Samant, S.D., (2004) Appl. Catal. A: Gen., 276, p. 5Chirchi, L., Ghorbel, A., (2002) Appl. Clay Sci., 21, p. 271Pillai, U.R., Demessie, E.S., (2003) Appl. Catal. A: Gen., 245, p. 103Ding, Z., Kloprogge, J.T., Frost, R.L., Lu, G.Q., Zhu, H.Y., (2001) J. Porous Mater., 8, p. 273Nowak, I., Ziolek, M., (1999) Chem. Rev., 99, p. 3603Chen, Z., Izuka, T., Tanabe, K., (1984) Chem. Lett., p. 1085Hanaoka, T., Takeuchi, K., Matsuzaki, T., Sugi, Y., (1990) Catal. Today, 8, p. 123Ogasawara, K., Iizuka, T., Tanabe, K., (1984) Chem. Lett., p. 645Christiano, S.P., Wang, J., Pinnavaia, T.J., (1985) Inorg. Chem., 24, p. 1222Kloprogge, J.T., Duong, L.V., Frost, R.L., (2005) Environ. Geol., 47, p. 967Kawi, S., Yao, Y.Z., (1999) Microporous Mesoporous Mater., 28, p. 25Xie, W., Xie, R., Pan, W.P., Hunter, D., Koene, B., Tan, L.S., Vaia, R., (2002) Chem. Mater., 14, p. 4837Marinkovic-Neducin, R.P., Kiss, E.E., Cukic, T.Z., Obadovic, D.Z., (2004) J. Therm. Anal. Calorim., 78, p. 307Ding, Z., Frost, R.L., (2004) Thermochim. Acta, 416, p. 11Luna, F.J., Schuchardt, U., (1999) Quim. Nova, 22, p. 104(1991) Adsorption, Surface Area and Porosity, , Gregg S.J., and Sing K.S.W. (Eds), Academic Press, London (Chapter 1)Gil, A., Massinon, A., Grange, P., (1995) Microporous Mater., 4, p. 369Kun, R., Mogyorósi, K., Dékány, I., (2006) Appl. Clay Sci., 32, p. 99Neaman, A., Pelletier, M., Villieras, F., (2003) Appl. Clay Sci., 22, p. 153Valverde, J.L., de Lucas, A., Dorado, F., Romero, A., Garcia, P.B., (2005) Ind. Eng. Chem. Res., 44, p. 2955Chaabene, S.B., Bergaoui, L., Ghorbel, A., (2004) Colloid Surf. A, 251, p. 109Sampieri, A., Fetter, G., Bosch, P., Bulbulian, S., (2004) J. Porous Mater., 11, p. 157Marinkovic-Neducin, R.P., Kiss, E.E., Cukic, T.Z., Obadovic, D.Z., (2004) J. Therm. Anal. Calorim., 78, p. 307Rios, L.A., Weckes, P.P., Schuster, H., Hölderich, W.F., (2005) Appl. Catal. A: Gen., 284, p. 15

Cyclooctene Epoxidation Using Nb-mcm-41 Synthesized At Room Temperature

An efficient and simple method for preparing Nb-MCM-41 has been developed. The mesoporous material Nb-MCM-41 was synthesized at room temperature using tetraethoxysilane (TEOS), tetramethylammonium hydroxide (TMAOH), cetyltrimethylammonium bromide (CTMABr) as template and NH 4[NbO(C2O4)2(H2O) 2]·(H2O)3, as the niobium source. The materials were characterized by X-ray diffraction (XRD), FT-IR and diffuse reflectance UV-vis spectroscopies. The characterization showed that most of the niobium was incorporated into the framework of MCM-41. Nb-MCM-41 was tested in the epoxidation of cis-cyclooctene using t-butyl hydroperoxide as oxidant and a catalystxyclooctene molar ratio of 1:1000. The activity of Nb-MCM-41 increases with the temperature of the reaction. Cyclooctene oxide was obtained with 50% yield after 24 h at 333 K, without formation of any by-products.154 C29452950Feig, A.L., Lippard, S.L., (1994) Chem. Rev., 94, pp. 759-805Venuto, P.B., (1997) Stud. Surf. Sci. Catal., 105, pp. 811-851Carvalho, V.A., Varaldo, P.B., Wallau, M., Schuchardt, U., (1997) Zeolites, 18, pp. 408-416Tanabe, K., Okazaki, S., (1995) Appl. Catal., 133, pp. 191-218Morikawa, A., Togashi, A., (1993) Catal. Today, 16, pp. 333-339Desponds, O., Keiski, R.L., Somarjai, (1993) Catal. Lett., 19, pp. 17-32Okazaki, S., Wada, N., (1993) Catal. Today, 16, pp. 349-359Jehng, J.M., Wachs, I.E., (1990) Catal. Today, 8, pp. 37-46Jehng, J.M., Wachs, I.E., (1993) Catal. Today, 16, pp. 417-426Okazaki, S., Okuyama, T., (1983) Bull. Chem. Soc. Japan, 56, pp. 2159-2160Nishimura, M., Asakura, K., Iwasawa, Y., (1986) J. Chem. Soc., Chem. Commun., 15, pp. 1660-1661Kushimoto, T., Ozawa, Y., Baba, A., Matsuda, H., (1993) Catal. Today, 16, pp. 571-578Sheldon, R.A., (1991) Chemtech, pp. 566-576Mineral Commodity Summaries - 2001Sheldon, R.A., (1996) Aspects of Homogeneous Catalysis, 1, pp. 411-423. , B. Cornils, W.A. Herrmann, Eds., VCH, WeinheimPaulino, I.S., Schuchardt, U., (2002) Stud. Surf. Sci. Catal., 141, pp. 93-100Ziolek, M., Nowak, I., (1997) Zeolites, 18, pp. 356-360Ziolek, M., Nowak, I., Lavallet, J.C., (1997) Catal. Lett., 45, pp. 259-265Gao, X.T., Wachs, I.E., Wong, M.S., Ying, J.Y., (2001) J. Catal., 203, pp. 18-24Chenite, A., Lepage, Y., Sayari, A., (1995) Chem. Mater., 7, pp. 1015-1019Anpo, M., Higashimoto, S., (2001) Stud. Surf. Sci. Catal., 135, pp. 123-131Prakash, A.M., Kevan, L., (1998) J. Am. Chem. Soc., 120, pp. 13148-13155Tanaka, T., Nojima, H., Yoshida, H., Nakagawa, H., Funabik, T., Yoshida, S., (1993) Catal. Today, 16, pp. 297-307Arnold, U., Da Cruz, R.S., Mandelli, D., Schuchardt, U., (2001) J. Mol. Catal., 165, pp. 149-15

Catalytic Transformations Of Ethanol For Biorefineries

Brazil and the USA are the major bioethanol producers in the world, and the main application of this alcohol is as fuel. Since Brazilian ethanol is the cheapest in the world, there is a crescent interest in its use as a building block for biorefineries. Bioethanol can be used for the direct production of drop-in chemicals, such as ethylene, propylene, 1,3-butadiene and larger hydrocarbons, as well as for the production of oxygenated molecules, such as 1-butanol, ethyl acetate, acetaldehyde, and acetic acid. 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Intrinsic backgrounds from Rn and Kr in the XENON100 experiment

In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon (222Rn), thoron (220Rn) and krypton (85Kr). We detail the event selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of ∼4 years, from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode

Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data

We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 yr, from January 2010 to January 2014. A profile likelihood method, which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of 431-14+16 day in the low energy region of (2.0-5.8) keV in the single scatter event sample, with a global significance of 1.9σ; however, no other more significant modulation is observed. The significance of an annual modulation signature drops from 2.8σ, from a previous analysis of a subset of this data, to 1.8σ with all data combined. Single scatter events in the low energy region are thus used to exclude the DAMA/LIBRA annual modulation as being due to dark matter electron interactions via axial vector coupling at 5.7σ

First Dark Matter Search Results from the XENON1T Experiment

We report the first dark matter search results from XENON1T, a ∼2000−kg-target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the Laboratori Nazionali del Gran Sasso in Italy and the first ton-scale detector of this kind. The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042±12)−kg fiducial mass and in the [5,40]  keVnr energy range of interest for weakly interacting massive particle (WIMP) dark matter searches, the electronic recoil background was (1.93±0.25)×10−4  events/(kg×day×keVee), the lowest ever achieved in such a dark matter detector. A profile likelihood analysis shows that the data are consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10  GeV/c2, with a minimum of 7.7×10−47  cm2 for 35−GeV/c2 WIMPs at 90% C.L

Search for bosonic super-WIMP interactions with the XENON100 experiment

We present results of searches for vector and pseudoscalar bosonic super-weakly interacting massive particles (WIMPs), which are dark matter candidates with masses at the keV-scale, with the XENON100 experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days ×34  kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the (8–125)  keV/c2 mass range, excluding couplings to electrons with coupling constants of gae>3×10−13 for pseudo-scalar and α′/α>2×10−28 for vector super-WIMPs, respectively. These limits are derived under the assumption that super-WIMPs constitute all of the dark matter in our galaxy

Dark Matter Search Results from a One Ton-Year Exposure of XENON1T

We report on a search for weakly interacting massive particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber with a fiducial mass of (1.30±0.01) ton, resulting in a 1.0 ton yr exposure. The energy region of interest, [1.4,10.6] keVee ([4.9,40.9] keVnr), exhibits an ultralow electron recoil background rate of [82-3+5(syst)±3(stat)] events/(ton yr keVee). No significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6 GeV/c2, with a minimum of 4.1×10-47 cm2 at 30 GeV/c2 and a 90% confidence level

XENON1T dark matter data analysis: Signal and background models and statistical inference

The XENON1T experiment searches for dark matter particles through their scattering off xenon atoms in a 2 metric ton liquid xenon target. The detector is a dual-phase time projection chamber, which measures simultaneously the scintillation and ionization signals produced by interactions in target volume, to reconstruct energy and position, as well as the type of the interaction. The background rate in the central volume of XENON1T detector is the lowest achieved so far with a liquid xenon-based direct detection experiment. In this work we describe the response model of the detector, the background and signal models, and the statistical inference procedures used in the dark matter searches with a 1  metric ton×year exposure of XENON1T data, that leads to the best limit to date on WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6  GeV/c2