Liquid-phase Hydrogenation Of Acetophenone Research Articles

Mixed thioalkyl-azoimine (SNN′)/α-diimine–ruthenium complexes: synthesis, characterization, DFT calculations, crystal structure and application as pre-catalysts for hydrogenation of acetophenone

Eight ruthenium complexes having thioalkyl-azoimine (SNN) ligands of two general types have been synthesized: (a) [Ru(L)(bipy)Cl](PF6) where {bipy = bipyridine, L = (2-SR)C6H4N=NC(COCH3)=NC6H4X, R = Ph (X = H, L1, 1; X = CH3, L2, 2; X = F, L3, 3); R = Me, (X = H, L4, 4)} and (b) [Ru(L1)(N–N)Cl](PF6) {N–N = 4,4-dimethyl-2,2′-bipyridine (dmbipy) (5), (1,10-phenanthroline) phen (6), 3,4,7,8-tetramethyl-1,10-phenanthroline (tetrmphen) (7), 5-5-chloro-1,10-phenanthroline (Clphen) (8). The crystal structures for 1 and 6 as well as for L2 are reported; the crystal structures of 1 and 6 show that L1 is bound to the ruthenium center as κ3[S,N,N′]. The complexes have been characterized by IR, UV/Vis and NMR spectroscopy as well as electrochemical (CV) techniques. The effect of groups X, the substituent R and N–N bidentate ligands on the electronic properties of the resulting mononuclear ruthenium complexes was investigated. The catalytic activity of these complexes was tested in the liquid-phase hydrogenation of acetophenone.

Ruthenium complexes of pyridine oxime and azoimine ligands: Syntheses, crystallography, electrochemical and catalytic properties

Five mononuclear ruthenium complexes of the type trans-[RuCl2(Azo)(Py-C(R)N = OH)] (C1–C5) {Azo = C6H5N = NC(COCH3) = NC6H4X, R = CH3, X = H (C1), Br (C2), CH3 (C3), F (C4); R = H, X = CH3 (C5)} have been synthesised and characterized by spectroscopic (IR, UV-Vis, and NMR) and electrochemical (cyclic voltammetry) techniques. In addition, C2 complex has been further characterized by single crystal X-ray diffraction. The complexes (C1-C3) were also tested with respect to their catalytic activity in the liquid-phase hydrogenation of acetophenone. The electronic absorption spectrum of C2 in acetonitrile has been modelled by time-dependent density functional theory.

Hydrogenation of Acetophenone on Pd/Silica–Alumina Catalysts with Tunable Acidity: Mechanistic Insight by In Situ ATR-IR Spectroscopy

Understanding the cooperative action of metal and acid sites of bifunctional catalysts is essential for developing more efficient catalysts for greener chemical processes. We used in situ ATR-IR spectroscopy in tandem with modulation excitation spectroscopy (MES) and phase-sensitive detection (PSD) to examine the functioning of Pd/silica–alumina (Pd/SA) catalysts with different acidity of the support in the liquid-phase hydrogenation of acetophenone (AP). The spectroscopic studies revealed that AP was adsorbed on the Pd surface in η1 (O) configuration and initially hydrogenated to 1-phenylethanol (PE) on the metallic Pd sites. On the Pd surface, PE was less strongly adsorbed than AP. PE was preferentially adsorbed on the acidic silica–alumina support via the C–OH group and subsequently dehydrated to styrene on the acidic sites. Hydrogen originating from dissociative adsorption on Pd sites is proposed to hydrogenate part of the formed styrene to ethylbenzene (EB). The intermediate styrene had a short lifet...

Catalytically active gauze-supported skeletal nickel prepared from Ni–Zn alloys electrodeposited from an acetamide–dimethyl sulfone eutectic mixture

Nickel–zinc alloys were electrodeposited on copper gauze from an acetamide–dimethyl sulfone eutectic mixture containing nickel chloride and zinc chloride. The as-deposited nickel–zinc alloys have compact microstructures with very small crystallites (approximately 3nm) and smooth surfaces. The nickel content could be varied between 20 and 90wt.% by controlling the temperature of the electrolyte. After alkaline leaching, a gauze-supported zinc based Raney nickel catalyst was obtained. The catalyst was benchmarked against commercial aluminum based Raney nickel in liquid phase hydrogenation of acetophenone. The gauze-supported zinc based skeletal nickel was more active and selective as compared to the commercial aluminum based Raney nickel. In addition, the gauze-supported zinc based Raney nickel catalyst could be reused without any hydrogen pretreatment. The activity of the reused catalyst decreased by 20%, but it retained its excellent selectivity.

Liquid-phase hydrogenation of acetophenone over silica-supported Ni, Co and Cu catalysts: Influence of metal and solvent

In this work, we studied the influence of solvent and metal nature on the liquid-phase hydrogenation of acetophenone (AP) over Ni/SiO2, Co/SiO2 and Cu/SiO2. Catalysts were prepared by wetness impregnation method with metal loads of about 7–8wt%. Catalytic tests were performed in a batch reactor, at 363K and 10bar (H2), using 2-propanol (IPA), cyclohexane (CHX), toluene (TOL) and benzene (BEN) as solvents. Considering the three catalysts, the general pattern for the initial hydrogenation rate was: Ni/SiO2>Co/SiO2>Cu/SiO2, whereas the trend for selectivity to 1-phenylethanol (PHE) was just the opposite. AP can interact with nickel metal surface through both –C=O group and aromatic ring and thus the aromatic alcohol and saturated compounds were obtained. Instead, cobalt and copper metal surfaces interact preferentially with the –C=O group leading to selective hydrogenation of AP into PHE. In addition, an important interaction between –C–OH group of PHE and Co/SiO2 surface takes place, leading to rapid alcohol hydrogenolysis into ethylbenzene. The general activity pattern with the four solvents was: IPA>CHX≥TOL≥BEN. The magnitude of solvent influence on the catalytic performance strongly depended on the metal nature. The most significant solvent effect took place with Ni/SiO2, whereas the less noticeable influence was observed in the case of Cu/SiO2. From pseudo-homogenous kinetic modeling and temperature-programmed desorption, the following noteworthy observations arose: (1) IPA has a positive contribution by hydrogen transfer and/or AP activation by polarization; (2) the magnitude of the positive IPA influence on AP hydrogenation rate follows the trend: Ni/SiO2>Co/SiO2>Cu/SiO2; (3) CHX has a neutral contribution because of its weak adsorption on the metal phase and low interaction with reactant and products; (4) the effect of TOL and BEN is clearly negative for Ni/SiO2 due to blockage of active sites by strong adsorption of solvent on the metallic surface; (5) the effect due to strong adsorption of TOL and BEN is much less noticeable on Co/SiO2 and Cu/SiO2, as a consequence, the pattern for AP hydrogenation rates in BEN and TOL is Cu/SiO2>Co/SiO2>Ni/SiO2. Selectivity to PHE was less influenced by solvent nature. However, in the case of Ni/SiO2 and Co/SiO2, maximum PHE yields and selectivities increased with the solvent–metal interactions, mainly due to inhibition of the PHE hydrogenolysis. Cu/SiO2 was always 100% selective to PHE in all of the solvents. These results are clearly indicating that the magnitude of the solvent effect on catalytic performance strongly depends on the metal nature.

Hydrogenation of Acetophenone in the Presence of Ru Catalysts Supported on Amine Groups Functionalized Polymer

Liquid phase hydrogenation of acetophenone (ACT) is studied over ruthenium catalysts (1-4 wt% Ru) supported on gel-type methacrylate-styrene resin (FCN) functionalized with C=O, –NH, and –NH2 groups. Microscopic studies (SEM, STEM) show that the nature of Ru particles depends on the level of Ru doping. At low Ru content (1–2 wt%) ruthenium nano-clusters are formed, while at 4 wt% Ru, metal crystallites of few nanometers in size are observed. Catalytic reactions are performed at mild conditions (atmospheric pressure of hydrogen, 40 °C) in biphasic isooctane-water (IO/H2O) solvent system, and, for comparison, in a single component solvent (isooctane or ethanol). The use of biphasic IO/H2O solvent system results in a dramatic improvement of selectivity. The hydrogenation of C=O in acetophenone dominates over the hydrogenation of aromatic ring, yielding 1-phenylethanol with ca. 80% selectivity. Ru/FCN catalysts exhibit higher selectivity than the reference Ru/Al2O3. This is tentatively assigned to the steric effects induced by the polymer network on migrating reactant molecules. Advantageous influence of biphasic IO/H2O solvent system has been attributed to the solvation of phenyl ring of acetophenone by non-polar isooctane, which facilitates the interaction with the catalyst surface via carbonyl group and leads to the preferential reduction to 1-phnenylethanol. Liquid phase hydrogenation of acetophenone was studied over ruthenium catalysts (1–4 wt% Ru) supported on diamine group functionalized gel-type polymer (FCN).

Preparation and characterization of RuCl 3 – Diamine group functionalized polymer

Gel-type resin with diamine functional groups, FCN, was used as a matrix for immobilization of ruthenium complexes. By reacting of RuCl 3 with swollen matrix of FCN polymer a series of Ru/FCN composites with various Ru loading (1%, 2%, and 4%) was prepared. All the characterization techniques (FT-IR, XRD, SEM, EDS, STEM, XPS, and DSC) proved the participation of functional groups in the coordination of Ru(III). These complexes contained both Cl- and N-ligands in various proportions depending on ruthenium loading in polymer. Taking into account the chelating character of N-ligands a hypothetical structure of octahedral Ru(III) complex coordinated to FCN polymer was proposed. 2%Ru/FCN when reduced by NaBH 4 exhibited catalytic activity in liquid phase hydrogenation of acetophenone. Higher selectivity in the presence of FCN supported Ru as compared to 2%Ru/Al 2O 3 catalyst toward 1-phenylethanol was observed.

Liquid phase acetophenone hydrogenation on Ru/Cr/B catalysts supported on silica

The liquid phase hydrogenation of acetophenone was studied over a series of silica supported bimetallic catalysts with various Ru/Cr atomic ratios. The catalysts were prepared by reduction of the metal salts with NaBH 4 aqueous solutions and were characterised by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) (ESCA). The hydrogenation reaction was carried out in batch at a hydrogen pressure of 9 bar. The selectivity towards reduction of the carbonyl function increases with the increasing amount of Cr ions added.

Modeling and comparison of acetophenone hydrogenation in trickle-bed and slurry airlift reactors

The performance behavior of a trickle-bed and a slurry airlift reactor has been studied, in case of an exothermic complex multistep reaction. Liquid-phase hydrogenation of acetophenone over a Rh/C catalyst has been performed using both continuous reactors. Mathematical models have been developed and simulations compared with experimental data. Modeling the airlift reactor is easy because it has been operated under conditions where there are no significant mass transfer limitations. Conversely, the trickle-bed model incorporates wall heat transfer, external and internal mass transfer resistances coupled to Langmuir-Hinshel-wood-type kinetics, and shows that: (1) available correlations for gas-liquid transfer are not satisfactory, (2) partial wetting of the catalyst is most probably an important process, (3) internal diffusion limitations are important. Finally, the trickle-bed and airlift reactor performances have been rigourously compared in terms of productivities and yields, and the effect of various parameters discussed. Differences observed concerning the yields have been attributed to the influence of back mixing in airlift reactor and pore diffusional effects in the case of a trickle-bed. The choice of an optimal technology remains an open problem especially when exothermic and complex reactions are to be carried out.

Nickel supported on titania-silica: Preparation, characterisation and activity for liquid phase hydrogenation of acetophenone

TiO 2:SiO 2 supports were prepared by impregnation of SiO 2 with an n-hexane solution of titanium tetraethoxide and were used to prepare supported nickel (20% w/w) catalysts. The supports were characterised by X-ray fluorescence (XRF), BET surface area measurements, X-ray diffraction (XRD), UV-VIS diffuse reflectance spectroscopy, and transmission electron microscopy (TEM ). The supported nickel catalysts were further characterised by hydrogen chemisorption, XRD, TEM, temperature-programmed reduction (TPR), and degree of reduction measurements. The catalysts were tested for liquid-phase hydrogenation of acetophenone. The TiO 2 : SiO 2 supports were found to have good dispersion of TiO 2 at lower loading but showed agglomeration at higher loadings and existed exclusively as anatase phase. Ni/TiO 2:SiO 2 catalysts showed strong suppression in hydrogen chemisorption similar to a Ni/ TiO 2 catalyst indicating strong metal support interaction (SMSI). The catalysts showed good activity for liquid-phase hydrogenation of acetophenone, which was comparable to Ni/TiO 2 and greater than Ni/SiO 2. Ni/7.3%TiO 2:SiO 2 showed a maximum in both catalytic activity and in the suppression of hydrogen chemisorption.