Gas-phase reduction of cyclic and acyclic α,β-unsaturated ketones by hydrogen transfer on MgO. Effect of the ketone structure

Ramos, Joaquim J. Moura; Dı́ez, V.K.; Ferretti, Cristián A.; Torresi, P.A.; Apesteguı́a, C.R.; Cosimo, J.I. Di

doi:10.1016/j.cattod.2011.02.034

Cited by 25 publications

(14 citation statements)

References 26 publications

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“…The selectivity of the MPV reaction to either C=O or C=C hydrogenation is controlled by the catalyst electronegativity, that is, acid–base character . This explains the increasing BAL and BOH formation as the B content increased.…”

Section: Resultsmentioning

confidence: 99%

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

et al. 2016

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Controlled incorporation of dopants into the structure of metal oxide catalysts can be used to fine‐tune their topological, chemical, and electronic properties. Conventional preparation methods (coprecipitation and impregnation) tend to produce materials with a limited extent of chemical interaction between metal oxide and dopant, small pore volume, and disconnected pore structure. Herein, we describe a combustion method to optimize both the porous structure of metal oxides and the chemical interaction with dopants. By exploiting the differences in melting points between metal oxide (MgO) and dopant (B), it is possible to create hierarchical mixed oxides with tailored chemical structure. As a model reaction, we employed the aldol condensation of acetaldehyde to crotyl alcohol, a key intermediate step in the conversion of bioethanol to 1,3‐butadiene, to show the unique characteristics of these materials. The B–Mg mixed oxide prepared by combustion exhibits an order of magnitude higher productivity of C4 products than conventional MgO and B–MgO. We anticipate that our approach could be extended to the development of other dual oxides with open structure for unrestricted diffusion and enhanced chemical interaction of acid and basic metal oxides.

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Section: Resultsmentioning

confidence: 99%

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

et al. 2016

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“…Under inert conditions, or in absence of any active metal for the molecular hydrogen activation, once the acetaldehyde reacts producing crotonaldehyde, the 1-butanol is obtained upon two subsequent hydrogenations: terminal C=O bonds hydrogenation through the Meerwein-Ponndorf-Verley (MPV) reduction (crotonaldehyde and butanal), and hydrogenation of the unsaturated intermediates (crotonaldehyde and crotyl alcohol) by surface-mediated hydrogen transfer reaction 3 [6,9]. Under these conditions, ethanol molecules are the hydrogen source for the former hydrogenation [18], being the hydrogen released in the dehydrogenation step [15,18,19]. HPA and mixed oxides are not very active for these reactions, so the global process is still far to be optimized.…”

Section: Introductionmentioning

confidence: 99%

Tuning the selectivities of Mg-Al mixed oxides for ethanol upgrading reactions through the presence of transition metals

Quesada

Faba

Dı́az

et al. 2018

Applied Catalysis A: General

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The effect of the presence of reduced Co and Ni (chosen as representative metals because of their good activity for dehydrogenation reactions) on the catalytic performance of basic mixed oxide (Mg-Al) for ethanol condensation is studied in this work. This effect has been studied both in absence and in presence of hydrogen, and considering the different steps of this complex reaction. Globally, best results were obtained with Co/Mg-Al, under reducing atmosphere, at mild temperature (below 600 K). At these conditons, 1-butanol production rates up to eight times higher than the obtained with Mg-Al under inert atmosphere. Co has a marked activity in the dehydrogenation step, that prevails over its less relevant activity in aldolization and hydrogenation reactions. This result indicates the relevant role of this first reaction step. DRIFT spectroscopy analyses were carried out to support the experimental results and to identify the role of hydrogen and metals on the oligomerization and permanent adsorption processes, which can produce the deactivation of the catalyst.

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“…Concerning the acidity, most of the original acid sites are blocked by copper nanoparticles, being this effect more notable for the strongest ones. The concentration of these acid sites is much lower for the Cu/Mg−Al, hence the amount of Lewis acid and acid‐basic pair sites, which promote the MPV reduction, is significantly higher for the Mg‐Al leading to higher ability of this material (or physical mixture) in performing this reaction. These sort of active sites are also related to non‐desired dehydrations (obtaining ethylene and 1,3‐butadiene).…”

Section: Resultsmentioning

confidence: 99%

Copper‐Basic Sites Synergic Effect on the Ethanol Dehydrogenation and Condensation Reactions

et al. 2018

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Bioethanol upgrading through condensation is of key interest in the development of sustainable processes, shifting from fossil to renewable carbon. Here, a new strategy is proposed, which combines in one catalyst an appropriate distribution of acid/ basic sites of a mixed oxide with the presence of an active dehydrogenation phase (Cu nanoparticles). Experiments, performed in a fixed bed reactor, reveal a very positive effect of Cu in the performance of MgÀAl catalyst, with 1-butanol productiv-ity 12 times higher at 523 K under inert conditions. The improvement is even more notable in presence of H 2 , almost 30 times higher, under same conditions. The presence of Cu on the surface increases the formation of acetaldehyde, limiting the extent of dehydration side-reactions. In addition, hydrogen enhances the C4 hydrogenation, preventing oligomerizations and inhibiting decarbonylation steps that are directly related to the catalytic deactivation by poisoning.[a] J.

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Gas-phase reduction of cyclic and acyclic α,β-unsaturated ketones by hydrogen transfer on MgO. Effect of the ketone structure

Cited by 25 publications

References 26 publications

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

Tuning the selectivities of Mg-Al mixed oxides for ethanol upgrading reactions through the presence of transition metals

Copper‐Basic Sites Synergic Effect on the Ethanol Dehydrogenation and Condensation Reactions

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