Catalysts featuring
2, 5, and 10 wt % silver supported on alumina
were prepared by the deposition precipitation method and activated
under hydrogen. All catalysts were characterized by Brunauer–Emmett–Teller
(BET) measurements, inductively coupled plasma-optical emission spectrometry
(ICP-OES), backscattered electron scanning electron microscopy (BSE-SEM),
high-resolution transmission electron microscopy (HR-TEM), hydrogen-temperature-programmed
reduction (H2-TPR), H2-chemisorption, thermogravimetric
analysis (TGA), infrared (IR) spectroscopy, X-ray diffraction (XRD),
Raman spectroscopy, and isopropylamine (IPA) TPD and evaluated in
a continuous plug flow fixed-bed reactor. Metal nanoparticles with
average sizes of 4.5, 11.5, and 21.1 nm were identified by HR-TEM
for the 2, 5, and 10 wt % Ag/Al2O3 catalysts,
respectively. A conversion of 99% was observed for 1-octyne over particles
between 10 and 15 nm in size, with stable operation up to 24 h (decreasing
thereafter) at a temperature of 140 °C and a pressure of 30 bar
in the competitive hydrogenation reaction. No conversion of 1-octene
was noted in competitive reactions (mixed 1-octyne and 1-octene feed)
but rather a gain of 1-octene throughout the 72 h time-on-stream.
The performance of all catalysts was influenced by both the metal
and support, where the latter impacted the overall acidity of the
catalysts, thus affecting their long-term stability.
Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine‐based ligands: pyCH2N(R)CH2py {R = propyl, tert‐butyl, cyclohexyl and phenyl; py = pyridine} with the [(η6‐C6H6)Ru(μ‐Cl)Cl]2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH2N(R)CH2py}C6H6](PF6)2 (R = C3H7 (1), C (CH3)3 (2), C6H11 (3) and the bidentate Ru (II) complex [Ru{pyCH2N(R)}C6H6]PF6 (R = C6H5 (4)) are reported. It was found that complexes 1, 2, 3 and 4 crystallised as mono‐metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n‐octane using t‐BuOOH and H2O2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t‐BuOOH as oxidant, however, superior yields (23–32%) were achieved using H2O2 over all systems. The selectivity was predominantly towards alcohols (particularly 2‐octanol) over all complexes using t‐BuOOH and H2O2 after reduction of the formed alkylhydroperoxides in solution by PPh3. High TONs of up to 2400 were achieved over the Ru/H2O2 systems.
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