Multiphase Catalytic Hydrogenation of p-Chloroacetophenone and Acetophenone. A Kinetic Study of the Reaction Selectivity toward the Reduction of Different Functional Groups

doi:10.1006/jcat.2000.3054

Journal of Catalysis

Volume 196, Issue 2, 10 December 2000, Pages 330-338

https://doi.org/10.1006/jcat.2000.3054 Get rights and content

Abstract

A multiphase catalytic system consisting of hydrocarbon solvent and aqueous phase, phase-transfer (PT) agent (Aliquat 336), and supported Pt or Pd catalyst, bubbled with hydrogen at atmospheric pressure, affords the rapid and efficient hydrodechlorination and the selective reduction of the functional groups of p-chloroacetophenone and acetophenone at 50°C and in moderate reaction times. The reaction gives quantitative yields of reduction products with variable selectivity, which can be controlled by varying some simple reaction conditions. Herein both halogen removal and carbonyl group or phenyl ring reductions are discussed. The composition of the aqueous phase, the nature of supported catalysts, the effect of various inorganic anions, and other reaction conditions have been studied kinetically to estimate the mechanistic aspects of the reaction selectivity. Emphasis is placed on the development of a novel synthetic tool, which allows control over the selectivity in the reduction of the carbonyl group and the phenyl ring. A number of kinetic models and the corresponding integral rate expressions were used, coupled with the “simultaneous nonlinear least-squares fitting” method, to estimate the rate constants for the formation of each particular reaction component. The kinetic monitoring allowed the accurate analysis of the reaction selectivity. Some mechanistic conclusions were drawn for the reaction under study that suggest that “softer” reduction conditions are attained in the presence of a PT agent and the aqueous phase.

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Cited by (35)

Solvent and substituent effects in hydrogenation of aromatic ketones over Ru/polymer catalyst under very mild conditions
2019, Molecular Catalysis
Citation Excerpt :
On the other hand an electron withdrawing group, like –Cl– (entry 6), slows down the process and after the same period of time only 29% conversion is observed. It should also be mentioned that for 4′-chloroacetophenone no products indicating hydrodechlorination process could be detected [2]. The observed trends may be assigned to changes in the polarization of CO group, which increases upon action of an electron donating substituent, or decreases in the presence of an electron withdrawing group.
The paper reports on the solvent and the substituent effects in hydrogenation of aromatic ketones (acetophenone and its derivatives) in the presence of Ru catalyst supported on functionalized gel-type methacrylate-styrene resin under very mild conditions (1 bar H₂, 40 °C). The investigated solvents included methanol, 2-propanol, tetrahydrofuran, toluene, isooctane, and cyclohexane, with and without addition of water. The best catalytic activity was obtained in biphasic solvent system consisting of isooctane/water (1:1). In methanol and 2-propanol the beneficial role of water was observed. The effects are discussed in terms of solvent protic/aprotic and polar/apolar properties. The impact of substituents depended on their electron-donating/withdrawing character, and on the position on the aromatic ring of acetophenone. The presence of electron donating substituents tended to increase the reaction rate, and the electron withdrawing group slowed down the process. Steric effect was observed for methylacetophenone isomers with CH₃ group at ortho, meta and para positions.
Hydrodechlorination of para chloroacetophenone with water-repellent platinum catalysts in a water/ethanol mixed solvent
2013, Applied Catalysis B: Environmental
Citation Excerpt :
The water-gas-shift method [9,10], and The common chemical method using a hydrogen and catalyst (that is, the HDC reaction) [11–45]. In these methods, a heterogeneous catalyst is typically used for the HDC reactions, where typical catalysts include: fly ash [11], Fe–Ni [12], Raney-Ni [13–17], Ni/C [18], Cu/C [18], Ru–Pd/TiO2 [19], Ru/C [20], Rh/Al2O3 [1,21], Rh/C [1,21,22], Pd/zeolite-Y [23,30], Pd/Al2O3 [1,21,22,24–30], Pd/C [1,3,14–16,18,20–22,24,26,31–39], Rh–Pd/C [2], Pd/PS–PEG [4,5], Pd/TiO2 [39], Pd/membrane polymer [40,41], Pd/Fe3O4 [43], Pt–Al/pillared clays [44], Pt/Al2O3 [21], and Pt/C [14,29,45].
To identify an effective catalyst for hydrodechlorination (HDC) reaction in an aqueous solvent, three types of modified Pt/SiO₂ catalysts were prepared using the water-repellent organosilane reagents of butyldimethylchlorosilane (BDMS), dimethyloctylchlorosilane (DMOS), and dimethyloctadecylchlorosilane (DMODS). The catalysts were characterized and their HDC activity toward para-chloroacetophenone (CLAP) was examined in an aqueous solvent.
The BET specific surface area, mesopore volume, platinum surface area, and high oxidation species of platinum surface of Pt/SiO₂-DMODS slightly decreased after the modification. Elemental analysis showed that 0.272 groups/nm² of the DMODS substituent were tethered on the catalyst surface.
Notably, in a water (35 mL)/ethanol (5 mL) mixed solvent under 1 MPa of hydrogen at 373 K for 60 min, the HDC reaction over the modified catalysts readily took place. From the difference in the extent of HDC product yields for the reactions, it was clear that the HDC activity of the catalysts decreased in the order Pt/SiO₂-DMODS ≈ Pt/SiO₂-DMOS > Pt/SiO₂-BDMS >> Pt/SiO₂. Furthermore, the turnover frequency (TOF) of Pt/SiO₂-DMODS (10.7 min⁻¹) was found to be more than fifty times that of Pt/SiO₂ (0.2 min⁻¹). These results indicate that the catalytic activity was significantly improved by the surface modification of the Pt/SiO₂ catalyst with the water-repellent organosilane reagents.
The high HDC activity of the modified catalysts is believed to result from the formation of a hydrophobic space on the catalytic support surface by the water-repellent organosilyl substituents. Therefore, more reactants in the aqueous solvent can interact with this space, leading to a significant increase in the number of collisions between the reactants on the active site.
The effects of the solvent composition and reaction temperature on the HDC activity of Pt/SiO₂-DMODS were also examined.
Dechlorination of γ-hexachlorocyclohexane by zero-valent metallic iron
2009, Journal of Hazardous Materials
This study investigated the rates and pathways of γ-hexachlorocyclohexane (γ-HCH) dechlorination by granular zero-valent iron under different pH, iron dosage and temperature conditions. It was found that γ-HCH was rapidly reduced to benzene and chlorobenzene (CB) with benzene as the major product and that the dechlorination likely follows three steps of dichloroelimination to benzene, or two steps of dichloroeliminations and one step of dehydrohalogenation to CB. The calculated pseudo-first-order rate of γ-HCH degradation was 0.0125 min⁻¹ at pH 6.73, 25 °C and 10 g L⁻¹ iron dosage, corresponding to 55.5 min of half-life. It was also found that the rate of γ-HCH dechlorination increases as a function of reaction temperature and zero-valent iron dosage and decreases as a function of solution pH. The calculated activation energy is 33.5 kJ mol⁻¹ at pH 6.73, which is much lower than that of dehydrohalogenation facilitated by hydroxyl under basic conditions. The study suggested that zero-valent iron could be used to effectively and efficiently transform γ-HCH.
Enantioselective hydrogenation of 1-phenyl-1,2-propanedione, ethyl pyruvate and acetophenone on Ir/SiO<inf>2</inf> catalysts. Effect of iridium loading
2008, Catalysis Today
The effect of the metal particle size and the modifier concentration on the enantioselectivity (ee) and the conversion level in the hydrogenation of three different substrates: 1-phenyl-1,2-propanedione, ethyl pyruvate and acetophenone were studied over Ir/SiO₂ catalysts. The metal loading was varied from 1 to 5 wt%. The catalysts were characterized by H₂ chemisorption, TEM, XRD, TPR and XPS. The reactions were tested in a stainless steel batch reactor at 298 K and 40 bar, and all experiments were performed using cyclohexane as solvent and cinchonidine (CD) as chiral modifier.
The conversion and ee increase with the metal particle size and the number of surface ensembles and the catalytic results revealed that 5 wt% Ir/SiO₂ catalyst reaches higher conversion and enantiomeric excess (ee) in the three studied reactions. Additionally, the relationship between the activity and ee with CD concentration, exhibit a volcano type curve and the three studied reactions, indicative of the importance of competitive adsorption between the modifier and the substrate on the catalyst surface.
Enhanced enantioselectivity of chiral hydrogenation catalysts after immobilisation in thin films of ionic liquid
2008, Journal of Molecular Catalysis A: Chemical
Chiral organometallic complexes were immobilized in silica supported thin films of ionic liquid. The heterogenized catalysts were tested in the hydrogenation of acetophenone, which was chosen as test reaction for the enantioselective reduction of prochiral ketones. High enantioselectivities (up to 74% ee) were achieved in supported ionic liquids using a catalyst/substrate pair, which showed no enantioselectivity in methanol. This is attributed to the unique solvent properties of ionic liquids including the formation of solvent cages of ionic liquid molecules around the complexes. Within these cages, transition states are modified and chemical transformations follow alternative reaction pathways.
Synthesis and characterization of novel silica-supported Pd/Yb bimetallic catalysts: Application in gas-phase hydrodechlorination and hydrogenation
2006, Journal of Catalysis
Citation Excerpt :
Catalytic HDC is emerging as an alternative low-energy, nondestructive methodology that facilitates recovery/reuse of valuable chemical feedstock [7]. Heterogeneous catalytic HDC has now been reported for liquid-phase [8–25] and gas-phase [26–59] operations, involving aliphatic reactants [8,11,16,27–29,31–36,39,43–45] and aromatic reactants [3,9,10,12–15,17–26,28,30,37–42,46–59]. There have been some attempts at kinetic modeling [17–19,26,28,46–52], but most reports have recorded HDC activities/selectivities over a particular, often narrow, range of operating conditions.
The gas-phase hydrodechlorination (HDC) of chlorobenzene (CB), 1,2-dichlorobenzene (1,2-DCB), and 1,3-dichlorobenzene (1,3-DCB) was investigated over a 5% w/w Pd/SiO₂ and a series of SiO₂-supported Yb–Pd (5% w/w Pd and $Yb / Pd = 2 / 3 mol / mol$ ) catalysts. The Pd/SiO₂ catalyst was prepared by Pd(C₂H₃O₂)₂ impregnation, supported Yb synthesized by contacting SiO₂ with Yb powder in liquid NH₃ and the bimetallic catalysts prepared by two stepwise routes: Pd(C₂H₃O₂)₂ impregnation of Yb/SiO₂ (Pd–Yb/SiO₂-step) or Pd impregnation preceding Yb introduction (Yb–Pd/SiO₂-step) and a single-step simultaneous introduction of Pd and Yb from a {(DMF)₁₀Yb₂[Pd(CN)₄]₃}_∞ precursor (Yb/Pd/SiO₂-sim). Under identical reaction conditions, the following specific initial CB HDC rate sequence was established: Pd–Yb/SiO₂-step (0.21 mol_Cl h⁻¹ m⁻²) ≈ Pd/SiO₂ (0.24 mol_Cl h⁻¹ m⁻²) < Yb/Pd/SiO₂-sim (0.41 mol_Cl h⁻¹ m⁻²) ≈ Yb–Pd/SiO₂-step (0.46 mol_Cl h⁻¹ m⁻²); reaction over Yb/SiO₂ resulted in a negligible conversion. Yb acts as a CB HDC promoter through a surface synergism with Pd; the extent of this promotion depends on the nature of the catalyst precursor and the sequence of metal(s) introduction to the support. The promotional effect of Yb extends to DCB HDC, where Yb–Pd/SiO₂-step outperforms Yb/Pd/SiO₂-sim (with a specific HDC rate 25 times greater than that delivered by Pd/SiO₂) and to catalytic hydrogenation (benzene → cyclohexane). The prereaction and postreaction catalyst samples were characterized in terms of BET area, TPR, TEM-EDX, H₂ chemisorption/TPD, XRD, and XPS measurements. The role of Yb as a promoter is discussed in terms of electron donation and impact on Pd dispersion but is attributed to the action of YbH₂, which serves as an additional source of surface reactive hydrogen; Yb activation of the CCl bond(s) for hydrogenolytic attack is also considered. HDC activity decreased with time-on-stream, an effect that we link to deleterious HCl/catalyst interactions that modify surface composition, leading to a disruption in H₂ uptake/release; XPS and TEM-EDX were used to characterize the residual surface Cl post-HDC.

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¹: To whom correspondence should be addressed. Fax: +39 (041) 257 8620. E-mail: [email protected].

²: On leave from N.D. Zelinsky Institute of Organic Chemistry of Russian Academy of Sciences, Leninsky pr. 47, Moscow 117913, Russia.

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Regular ArticleMultiphase Catalytic Hydrogenation of p-Chloroacetophenone and Acetophenone. A Kinetic Study of the Reaction Selectivity toward the Reduction of Different Functional Groups

Abstract

J. Mol. Catal. A: Chemical

Appl. Catal: B

J. Catal.

J. Chem. Soc., Perkin Trans. 1

J. Org. Chem.

J. Org. Chem.

J. Org. Chem.

J. Org. Chem.

J. Org. Chem.

Chem. Lett.

Catal. Lett.

Regular Article
Multiphase Catalytic Hydrogenation of p-Chloroacetophenone and Acetophenone. A Kinetic Study of the Reaction Selectivity toward the Reduction of Different Functional Groups