2 Experimental Section

2.1 Chemicals

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Inorganic chemicals

 

AlO(OH) (Pural SB)

SASOL Germany GmbH

Magnesium (Mg)

Aldrich, small turnings, 99.98%

Magnesium carbonate (MgCO3)

Fluka, 99%

Magnesium hydroxide[(Mg(OH)2]

Fluka, 99%

Magnesium fluoride (MgF2)

Aldrich, 98%

Magnesium nitrate hexahydrate [Mg(NO3)2⋅6H2O]

Fluka, 99%

Potassium acetate (KC2H3O2)

Merck, 99%

Potassium bromide (KBr)

Fluka, 99%

Potassium carbonate (K2CO3)

Fluka, 99%

Potassium hydrocarbonate (KHCO3)

Merck, 99%

Potassium hydroxide (KOH, pellets)

Merck, 85%

Potassium nitrate (KNO3)

Fluka, 99%

Carbon dioxide (CO2)

Messer Griesheim, 99.995 vol.-%

Hydrofluoric acid (HF)

Merck, 40%

Hydrofluoric acid (HF, gas)

Solvay Fluor, Germany

Hydrotalcite (Pural MG30, 50, 61, 70)

SASOL Germany GmbH

Zirconyl chloride octahydrate (ZrOCl2⋅8H2O)

Fluka, 99%

  

Organic chemicals

 

1-Butene

Aldrich, 99%

Methyl vinyl ketone

Aldrich, 99%

2-Methylcyclohexane-1,3-dione

Acros, 98%

2-Acetylcyclopentanone

Aldrich, 98%

2-Acetylcyclohexanone

Acros, 99%

Dimethyl phthalate

Acros, 99%

Methanol

Aldrich, 99%

2-methoxycarbonylcyclopentanone

Acros, 99%

Pyridine

Merck, 99%

DMSO-d 6

Chemotrade, 99.5%

CDCl3

Chemotrade, 99.5%

2.2 Catalyst preparation

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Wet impregnation, thermal decomposition and sol-gel methods are used in the preparation of the catalysts. The details are shown in the following chapters.

2.3 Characterization

Element analysis

C, N, H contents were determined by elemental analysis (Leco CHNS-932 element analyzer). K, Zr, Mg, Al contents were determined by ICP-OES (UNICAM 701). F contents were determined according to Seel by the method described in [1]. 1020 mg of sample was dissolved by melting in a mixture of K 2 CO 3 /Na 2 CO 3 in a platinum crucible. The mixture was cooled down to room temperature and dissolved in distilled water. About 1 g of silica and 20 mL of 98% H 2 SO 4 were slowly added to the solution. This solution was then distilled under a water vapor flow in order to support the formation of H 2 SiF 6 and its evaporation. After the condensation of H 2 SiF 6 , the fluoride content in the aqueous solution was determined with an F sensitive electrode.

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X-ray diffraction (XRD)

X-ray powder diffraction (XRD) analysis was performed with Cu Kα radiation (λ = 1.5418 Ǻ, 40 kV, and 35 mA) using RD 7 (Rich. Seifert GmbH & Co. KG, Freiberg, Germany) over the 2θ range from 5 to 65° or 90°.

N2 adsorption/desorption experiments

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Nitrogen adsorption/desorption experiments were carried out at 77 K using a Micromeritics ASAP 2010 system; samples were degassed at 200 °C (or 100 °C) overnight. The specific surface area was calculated using the BET method. Pore volumes and pore distributions were calculated using the BJH method.

CO2-TPD

CO2-TPD was used to measure the strength of basic sites. The pelleted sample (approximately 300 mg, 0.3–0.5 mm diameter fraction) was pretreated in a nickel reactor under Ar (70 mL/min) at 600 °C for 1 h. The sample was then cooled to 50 °C and exposed to a stream of Ar and CO2. The sample was flushed for over 1 h at 50 °C to remove physisorbed CO2, after which, the TPD program (10 °C/min, up to 600 °C, held for 30 min) was started. The desorption of gas phase CO2 was detected by monitoring the band at 2349 cm 1 with FTIR spectroscopy (FTIR system 2000, Perkin-Elmer).

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1H NMR

1H NMR experiments were preformed on a Bruker AVANCE 400 spectrometer.

27Al MAS NMR

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27Al MAS NMR experiments were preformed by accumulating 64 spectra on a Bruker AVANCE 400 spectrometer at a resonance frequency of 104.3 MHz with excitation of π/6 pulses and a repetition time of 5 s. A commercial Bruker 4-mm probe was used to perform the MAS experiments with a spinning rate of 10 kHz. An aqueous 1 M solution of aluminum chloride was used as reference for the chemical shifts.

19F MAS NMR

Solid state NMR experiments were done on a Bruker AVANCE 400 spectrometer using a 2.5 mm double-bearing magic angle spinning (MAS) probe with a decoupling channel optimized for 19F observation. The samples were characterized at room temperature by measurements of 19F (I = 1/2, 282.4 MHz) nucleus at an ultrafast spinning speed of 30 kHz to reduce most of the 19F dipolar interactions and obtain high-resolution spectra. A recycle delay of 10 s and 64 scans were used. 19F chemical shifts were referenced to CFCl3 at 0 ppm and accurate to ±1 ppm.

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Thermal analysis

Thermogravimetry (TG) and differential thermal analysis measurements (DTA) were performed using a NETZSCH STA409C system equipped with a skimmer-coupled mass spectrometer in air with a heating rate of 10 °C/min from room temperature up to 700 °C (reference: Al2O3).

FTIR measurements

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FTIR spectra of KBr pellets were recorded on a Perkin-Elmer 2000 spectrometer in transmission mode. About 500 mg of KBr were pressed with 1.5–2.0 mg of the sample, and then the samples were measured in the regions 400–4000 cm- 1.

FTIR studies were also carried out on self-supporting wafers (10–40 mg) in a transmission IR quartz cell with CaF2 window. Pyridine (Merck, 99%) was freshly distilled and stored over zeolite A. The samples were pretreated in flowing synthetic air for 1 h and evacuated for 30 min both at 550 °C. The adsorption of pyridine was then performed at 40 °C with 0–15 mbar pyridine with subsequent evacuation for 10 min to remove physisorbed pyridine. The IR spectra were measured every 50 °C during temperature programmed desorption (TPD) from 100 to 300 °C (heating rate of 10 °C/min) after evacuation for 10 min at each temperature. In the case of CO2 adsorption (Messer Griesheim, 99.995 vol.-%), the samples were pretreated under vacuum at 400 °C for 1 h. The measurement conditions were identical to those used after pyridine adsorption except for the evacuation time during TPD of 10 min, which was lengthened to 30 min. IR spectra (64 accumulations, resolution of 2 cm–1) were recorded on a Digilab FTS-60A spectrometer. The spectra were normalized with the wafer weight; the spectrum measured prior to adsorption was used as the background spectrum.

Microcalorimetric measurements

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Microcalorimetric measurements were carried out in Prof. Auroux’s group (Institut de Recherches sur la Catalyse, France).

Gas-phase CO2 adsorption

Microcalorimetric data were collected using a heat flow Tian-Calvet-type calorimeter (C 80, Setaram) connected to a volumetric line with an online injection system for pulsing reactive gases. CO2 (> 99.9%) was pulsed from a storage vessel. After each pulse, the equilibrium pressure was measured with a differential pressure gauge (Barocel, Datametrics). The calorimetric and volumetric data (pressure, adsorbed volume, heats of adsorption, differential and integral enthalpies) were stored and analyzed by a microcomputer. The sample (70–100 mg) was pretreated under vacuum overnight at 400 °C. The first adsorption cycle was complete after a final equilibrium pressure of 0.6 Torr was reached at 40 °C; the system was then evacuated to remove the physisorbed CO2, and a second adsorption cycle was performed. For all the samples measured here, the level of irreversible adsorption was almost constant above 0.2 Torr. Thus, the amounts of totally adsorbed (chemisorbed and physisorbed) and irreversibly (chemisorbed) CO2 were determined from the difference between the isotherms of the first and second cycle of adsorption, respectively.

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Liquid-phase adsorption: benzoic acid in toluene

Liquid-phase experiments were performed on a Titrys calorimeter (Setaram) with a stirring system. The samples (about 200 mg) were pretreated under vacuum overnight at 400 °C and then transferred to the calorimetric cell, which contained toluene (1.5 mL). The reference cell contained the same amount of toluene before injection. At70 °C, the solution of benzoic acid in toluene (0.0307 mol/L) was injected stepwise (0.2 mL, injection rate: 0.05 mL/min) every 2 h. The amount of unreacted benzoic acid was measured by UV spectrofluorimetry.

X-ray photoelectron spectroscopy (XPS)

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In chapter 5, X-ray photoelectron spectroscopy (XPS) was preformed on VG ESCALAB 220 iXL spectrometer with a Mg K αsource and a monochromated Al K αsource, respectively [measurements were carried out in Institut für Angewandte Chemie Berlin-Adlershof e.V. (ACA)]. In chapter 6, Narrow scan X-ray photoelectron spectra (XPS) were acquired using Kratos Axisultra electron spectrometer with monochromatised Al Kα excitation (h ν= 1486.6 eV) operated at 75 W and in CAE 20mode [measurements were carried out in Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin]. Before recording the spectra the samples were stored overnight in the Extended PrepLock chamber in a vacuum better than 10-6 mbar in order to degas. The vacuum in the spectrometer was better than 10-8 mbar. Binding energy data were referenced to the aliphatic C 1s peak at 284.8 eV. Charge neutralization system was used. The spectrometer energy scale was calibrated following ISO 15427.

Transmission electron microscopy (TEM)

Transmission electron microscopy (TEM) was preformed on Hitachi H-8110 (200 kV, LaB6 gun) with energy dispersive X-ray detector.

2.4 Reaction

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Gas-phase reaction: Double-bond isomerization of 1-butene

The isomerization of 1-butene was performed in a down-flow, fixed-bed glass reactor. Equal volumes of the pelleted, calcined catalyst (about 300–450 mg, 0.3–0.5 mm diameter fraction) were exposed to the feed stream mixture of nitrogen (10 mL/min) and 1-butene (0.6 mL/min) at 150 °C. Prior to the reaction, the catalyst was pretreated in N2 at 600 °C for 2 h. On-line gas chromatography (Shimadzu GC-17A, FID, quartz capillary: PONA (methylsiloxane), 50 m, 0.2 mm x 0.5 μm) was used to determine the composition of the reaction mixture of 1-butene and cis/trans-2-butene after a time-on-stream (TOS) of 10, 30, 60 and 90 min. Due to 100% product selectivity, the reaction conversion is given by the yield of 2-butene product. Product yields were normalized by the mass of the catalyst used at 30 min in order to compare the catalysts’ results with each other.

Liquid-phase Michael additions

↓50

Generally, the reaction was carried out in a 50-mL round-bottom flask at room temperature. Methyl vinyl ketone (22.5 mmol, Aldrich, 99%), a CH-acid compound (15.0 mmol) [2-methylcyclohexane-1,3-dione (Acros, 98%, slightly soluble in methanol), 2-acetylcyclopentanone (Aldrich, 98%) or 2-acetylcyclohexanone (Aldrich, 97%)], dimethyl phthalate (3.75 mmol, Acros, 99%, internal NMR standard), and the solvent, methanol (10 mL, Aldrich, 99%), were stirred together for 30 min to saturate the mixture before the powdered catalyst was added. In general, a catalyst weight of 0.225 g was used. The reaction mixture (0.1 to 0.3 mL) was sampled at certain times and centrifuged. The separated solution was then concentrated on a rotary evaporator to remove solvent and unreacted methyl vinyl ketone. The yield of the target product was analyzed by 1H NMR spectroscopy (solvent: DMSO-d 6 or CDCl3) using the integrals of the CH3 signals of the Michael adducts: 2-methyl-2-(3-oxo-butyl)-cyclohexane-1,3-dione (1.11 and 2.04 ppm, DMSO-d 6), 2-acetyl-2-(3-oxo-butyl)-cyclopentanone (2.14 and 2.09 ppm, CDCl3), 2-acetyl-2-(3-oxo-butyl)-cyclohexanone (2.08 ppm, CDCl3, only one CH3-signal used because the other overlapped with that of 1,3-dione reagent), 2-oxo-1-(3-oxo-butyl)-cyclopentanecarboxylic acid methyl ester (2.11 and 3.68 ppm) and dimethyl phthalate (3.83 ppm in DMSO-d 6 and 3.88 ppm in CDCl3 ).


Footnotes and Endnotes

1 []F. Seel, Angew. Chem. 76 (1964) 532–534.



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