A new concept of a solid catalyst with ionic liquid layer (SCILL) as a novel method to improve the selectivity of heterogeneous catalysts is presented. The sequential hydrogenation of cyclooctadiene (COD) to cyclooctene (COE) and cyclooctane on a commercial Ni catalyst coated with the ionic liquid [BMIM][n-C 8 H 17 OSO 3 ] was tested as first model system. Compared to the original catalyst, the coating of the internal surface with the ionic liquid (IL) strongly enhances the maximum intrinsic COE yield from 40 to 70 %. This effect is already achieved for a pore filling degree of only 10 % and cannot be explained by pore diffusion, as shown by experiments with different particle sizes and theoretical considerations. The IL layer is very robust and no leaching into the organic phase was detectable.
The gas-phase loading of [Zn(4)O(btb)(2)](8) (MOF-177; H(3)btb=1,3,5-benzenetribenzoic acid) with the volatile platinum precursor [Me(3)PtCp'] (Cp'=methylcyclopentadienyl) was confirmed by solid state (13)C magic angle spinning (MAS)-NMR spectroscopy. Subsequent reduction of the inclusion compound [Me(3)PtCp'](4)@MOF-177 by hydrogen at 100 bar and 100 degrees C for 24 h was carried out and gave rise to the formation of platinum nanoparticles in a size regime of 2-5 nm embedded in the unchanged MOF-177 host lattice as confirmed by transmission electron microscopy (TEM) micrographs and powder X-ray diffraction (PXRD). The room-temperature hydrogen adsorption of Pt@MOF-177 has been followed in a gravimetric fashion (magnetic suspension balance) and shows almost 2.5 wt % in the first cycle, but is decreased down to 0.5 wt % in consecutive cycles. The catalytic activity of Pt@MOF-177 towards the solvent- and base-free room temperature oxidation of alcohols in air has been tested and shows Pt@MOF-177 to be an efficient catalyst in the oxidation of alcohols.
The vapour pressure and the thermal stability of liquids are important material properties. For high boiling organic and ionic liquids (ILs), the determination of these properties is laborious and it is not easy to discriminate between evaporation and thermal decomposition. In this work, a simple but accurate method is presented to determine the parameters of decomposition and evaporation by thermogravimetrical analysis (TGA). The mass transfer coefficient was calculated based on a new correlation for the Sherwood number for cylindrical crucibles in overflow of a carrier gas. This correlation is valid for any diameter-to-height ratio and for any filling degree of the crucible and was derived from numerical simulations and proven by experiments with hexadecane, dodecane, and anthracene. The TGA analysis of two ILs was conducted. [EMIM][EtSO(4)] decomposes at ambient pressure without a measurable contribution of evaporation. To the contrary, [BMIM][NTf(2)] is relatively volatile. The vapour pressure of [BMIM][NTf(2)] and the kinetics of decomposition of both ILs were determined.
Ionic liquids (ILs) are widely discussed as alternative green solvents not only because of their unique chemical properties, but also because of their extremely low vapour pressure and -at least in some cases -relatively high thermal stability. Two complementary methods are analyzed and compared to determine both the rate constant of decomposition and the vapour pressure of four ILs: (1) thermogravimetrical analysis at ambient pressure (TG ap ) with an overflow of inert gases, and (2)
a Herein, we report a remarkable finding that biomass oxidation to formic acid (FA) in water-organic biphasic reaction systems is far more selective than the same reaction in a monophasic aqueous media.While literature claims that the yield of FA from carbohydrates and biomass is limited to less than 68%, even for simple substrates such as glucose or glycerol, we demonstrate in this study that FA yields of up to 85% can be obtained from glucose. Using our biphasic reaction protocol, even raw lignocellulosic biomass, such as beech wood, leads to FA yields of 61%. This is realized by applying polyoxometalate H 8 PV 5 Mo 7 O 40 as a homogeneous catalyst, oxygen as the oxidant and water as the solvent in the presence of a long-chain primary alcohol as an in-situ extracting agent. The new, liquid-liquid biphasic operation opens a highly effective way to produce pure FA, a liquid syngas equivalent, from wood in a robust, integrated, and low-temperature process.
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