Meerwein Ponndorf Verley Reaction Research Articles

Preparation of ZrO2/Na-β and ZrO2/H-β catalysts and their catalytic performance for the Meerwein–Ponndorf–Verley reaction of cyclohexanone and isopropanol

ZrO2/Na-β and ZrO2/H-β catalysts are prepared by the reflux impregnation method and are applied to the Meerwein–Ponndorf–Verley reduction of cyclohexanone and isopropanol. The catalysts are characterized by X-ray diffraction, scanning electron microscopy-energy dispersive spectrum, temperature-programmed desorption of ammonia, N2 isothermal adsorption and desorption, and inductively coupled plasma mass spectrometry. The products are identified by gas chromatography‒mass spectrometry and analyzed by gas chromatography. The experimental results showed that ZrO2/H-β exhibits higher catalytic activity for the above Meerwein–Ponndorf–Verley reduction because ZrO2/H-β has both Zr4+ and Al3+ ion acid centers, which provide the moderately strong acid needed for the reaction. Under optimized conditions, ZrO2/H-β(6) is used as the catalyst, and the conversion rate of cyclohexanone was 92.0% as determined by the area-normalized calculation based on cyclohexanone. The catalyst can be regenerated by programmed heating calcination. The conversion rate of cyclohexanone decreased to 79.4% after five recycling cycles, and its service life needs further study to be improved.

Solvent-Assisted Ketone Reduction by a Homogeneous Mn Catalyst.

The choice of a solvent and the reaction conditions often defines the overall behavior of a homogeneous catalytic system by affecting the preferred reaction mechanism and thus the activity and selectivity of the catalytic process. Here, we explore the role of solvation in the mechanism of ketone reduction using a model representative of a bifunctional Mn-diamine catalyst through density functional theory calculations in a microsolvated environment by considering explicit solvent and fully solvated ab initio molecular dynamics simulations for the key elementary steps. Our computational analysis reveals the possibility of a Meerwein–Ponndorf–Verley (MPV) type mechanism in this system, which does not involve the participation of the N–H moiety and the formation of a transition-metal hydride species in ketone conversion. This path was not previously considered for Mn-based metal–ligand cooperative transfer hydrogenation homogeneous catalysis. The MPV mechanism is strongly facilitated by the solvent molecules present in the reaction environment and can potentially contribute to the catalytic performance of other related catalyst systems. Calculations indicate that, despite proceeding effectively in the second coordination sphere of the transition-metal center, the MPV reaction path retains the enantioselectivity preference induced by the presence of the small chiral N,N′-dimethyl-1,2-cyclohexanediamine ligand within the catalytic Mn(I) complex.

Amberlyst-15 supported zirconium sulfonate as an efficient catalyst for Meerwein-Ponndorf-Verley reductions.

The Meerwein-Ponndorf-Verley (MPV) reaction is an important chemoselective route for carbonyl group hydrogenation, and thus designing new and effective catalysts for this transformation remains important and challenging. In this work, a new sulfonate coordinated Zr(IV) catalyst was prepared by the coordination of Zr(IV) onto the sulfonate groups of Amberlyst-15, which can effectively catalyze the MPV reaction and quantitatively convert carbonyl compounds to the corresponding alcohols with high reactivity and stability. Detailed mechanistic investigations reveal that the catalytic performance of Zr-AIER can be attributed to the synergetic effect between Zr4+ and the sulfonate group, and the porous structure with high surface area.

Recyclable Zr/Hf-Containing Acid-Base Bifunctional Catalysts for Hydrogen Transfer Upgrading of Biofuranics: A Review.

The massive burning of a large amount of fossil energy has caused a lot of serious environmental issues (e.g., air pollution and climate change), urging people to efficiently explore and valorize sustainable alternatives. Biomass is being deemed as the only organic carbon-containing renewable resource for the production of net-zero carbon emission fuels and fine chemicals. Regarding this, the selective transformation of high-oxygen biomass feedstocks by catalytic transfer hydrogenation (CTH) is a very promising strategy to realize the carbon cycle. Among them, the important Meerwein-Ponndorf-Verley (MPV) reaction is believed to be capable of replacing the traditional hydrogenation strategy which generally requires high-pressure H2 and precious metals, aiming to upgrade biomass into downstream biochemical products and fuels. Employing bifunctional heterogeneous catalysts with both acidic and basic sites is needed to catalyze the MPV reaction, which is the key point for domino/cascade reaction in one pot that can eliminate the relevant complicated separation/purification step. Zirconium (Zr) and hafnium (Hf), belonging to transition metals, rich in reserves, can demonstrate similar catalytic efficiency for MPV reaction as that of precious metals. This review introduced the application of recyclable heterogeneous non-noble Zr/Hf-containing catalysts with acid-base bifunctionality for CTH reaction using the safe liquid hydrogen donor. The corresponding catalysts were classified into different types including Zr/Hf-containing metal oxides, supported materials, zeolites, metal-organic frameworks, metal-organic hybrids, and their respective pros and cons were compared and discussed comprehensively. Emphasis was placed on evaluating the bifunctionality of catalytic material and the key role of the active site corresponding to the structure of the catalyst in the MPV reaction. Finally, a concise summary and prospect were also provided centering on the development and suggestion of Zr/Hf-containing acid-base bifunctional catalysts for CTH.

A novel and efficient N-doping carbon supported cobalt catalyst derived from the fermentation broth solid waste for the hydrogenation of ketones via Meerwein–Ponndorf–Verley reaction

Most of the non-noble metal catalysts used for the Meerwein–Ponndorf–Verley (MPV) reaction of carbonyl compounds rely on the additional alkaline additives during preparation to achieve high efficiency. To solve this problem, in this work, we prepared a novel N-doped carbon supported cobalt catalyst (Co@CN), in which the carriers were derived from the nitrogen-rich organic waste, i.e., oxytetracycline fermentation residue (OFR, obtained from oxytetracycline refining workshop). No additional nitrogen sources were used during preparation. The results showed that inherent nitrogen in OFR could provide N-containing basic sites, and formed Co-N structures via coordinating with cobalt. The Co-N sites together with the coexisting Co(0) cooperated to catalyze the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) by MPV reaction. Co(0) dominated the activation of H in isopropanol, while Co-N dominated the formation of the six-membered ring transition state.

Uranyl(VI) Triflate as Catalyst for the Meerwein-Ponndorf-Verley Reaction.

Catalytic transformation of oxygenated compounds is challenging in f-element chemistry due to the high oxophilicity of the f-block metals. We report here the first Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl substrates with uranium-based catalysts, in particular from a series of uranyl(VI) compounds where [UO2(OTf)2] (1) displays the greatest efficiency (OTf = trifluoromethanesulfonate). [UO2(OTf)2] reduces a series of aromatic and aliphatic aldehydes and ketones into their corresponding alcohols with moderate to excellent yields, using iPrOH as a solvent and a reductant. The reaction proceeds under mild conditions (80 °C) with an optimized catalytic charge of 2.3 mol % and KOiPr as a cocatalyst. The reduction of aldehydes (1-10 h) is faster than that of ketones (>15 h). NMR investigations clearly evidence the formation of hemiacetal intermediates with aldehydes, while they are not formed with ketones.

Disproportionation of aliphatic and aromatic aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions

Disproportionation of aliphatic and aromatic aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions

Mechanistic Insights into the Meerwein–Ponndorf–Verley Reaction and Relative Side Reactions over MgO in the Process of Ethanol to 1,3-Butadiene: A DFT Study

In this work, we performed density functional theory calculations to explore reaction pathways of ethanol to 1,3-butadiene on the surfaces of MgO(100) and MgO(110). The overall activation barrier a...

Direct use of the solid waste from oxytetracycline fermentation broth to construct Hf-containing catalysts for Meerwein-Ponndorf-Verley reactions.

The oxytetracycline fermentation broth residue (OFR) is an abundant solid waste in the fermentation industry, which is hazardous but tricky to treat. The resource utilization of the waste OFR is still challenging. In this study, a novel route of using OFR was proposed that OFR was used as the organic ligands to construct a new hafnium based catalyst (Hf-OFR) for Meerwein–Ponndorf–Verley (MPV) reactions of biomass-derived platforms. The acidic groups in OFR were used to coordinate with Hf4+, and the carbon skeleton structures in OFR were used to form the spatial network structures of the Hf-OFR catalyst. The results showed that the synthesized Hf-OFR catalyst could catalyze the MPV reduction of various carbonyl compounds under relatively mild reaction conditions, with high conversions and yields. Besides, the Hf-OFR catalyst could be recycled at least 5 times with excellent stability in activity and structures. The prepared Hf-OFR catalyst possesses the advantages of high efficiency, a simple preparation process, and low cost in ligands. The proposed strategy of constructing catalysts using OFR may provide new routes for both valuable utilization of the OFR solid waste in the fermentation industry and the construction of efficient catalysts for biomass conversion.

Ultra-small UiO-66-NH2 nanoparticles immobilized on g-C3N4 nanosheets for enhanced catalytic activity

UiO-66-NH2, an important metal–organic framework, is usually synthesized by solvothermal method and the particle size is generally larger than 200 nm, which limits its catalytic applications in chemical reactions. It is very meaningful to produce UiO-66-NH2 nanoparticles with ultra-small size, but remains challenging. Herein, we synthesized UiO-66-NH2 nanoparticles in size of 8–15 nm that are immobilized on g-C3N4 nanosheets. Compared with the UiO-66-NH2 synthesized by the traditional solvothermal method (> 200 nm), the ultra-small UiO-66-NH2 nanoparticles immobilized on g-C3N4 have more unsaturated coordination positions and increased Lewis acidity. Owing to these combined advantages, the ultra-small UiO-66-NH2 nanoparticles exhibit greatly improved catalytic activity for Meerwein–Ponndorf–Verley reaction than larger UiO-66-NH2 particles.

A novel hafnium-graphite oxide catalyst for the Meerwein-Ponndorf-Verley reaction and the activation effect of the solvent.

Construction and application of novel hydrogenation catalysts is important for the conversion of carbonyl or aldehyde compounds into alcohols in the field of biomass utilization. In this work, a novel, efficient, and easily prepared hafnium–graphite oxide (Hf–GO) catalyst was constructed via the coordination between Hf4+ and the carboxylic groups in GO. The catalyst was applied into the hydrogenation of biomass derived carbonyl compounds via the Meerwein–Ponndorf–Verley (MPV) reaction. The catalyst gave high efficiency under mild conditions. An interesting phenomenon was found whereby the activity of the catalyst increased gradually in the initial stage during reaction. The solvent, isopropanol, was proved to have an activation effect on the catalyst, and the activation effect varied with different alcohols and temperatures. Further characterizations showed that isopropanol played the activation effect via replacing the residual solvent (DMF) in micro- and mesopores during the preparation process, which was hard to be completely removed by common drying process.

Monolithic microreactors of different structure as an effective tool for in flow MPV reaction

Silica monolithic microreactors of the same topology of the skeleton but different pore sizes were functionalized with zirconium isopropoxide (Zr/Si = 0.14), and they were studied in Meerwein-Ponndorf-Verley (MPV) reduction of cyclohexanone using n-butanol as a hydrogen donor. It was shown that the concentration of Lewis acid sites was proportional to the value of the specific surface area, and this directly translated into the higher reaction rate, larger TOF-value and productivity. The monolith with the largest surface area, 625 m2/g was characterized by the small flow-through pores (2 µm), and thus very high flow resistance. Catalytic studies confirmed the first order kinetics of MPV reduction, and that the overall/observed reaction rate depends on the rate of the intrinsic chemical reaction and internal diffusion. Moreover, the higher efficiency of zirconium functionalized mesoporous catalysts over homogeneous zirconium isopropoxide has been demonstrated in batch process.

MPV Reduction of Furfural to Furfuryl Alcohol on Mg, Zr, Ti, Zr–Ti, and Mg–Ti Solids: Influence of Acid–Base Properties

The Meerwein–Ponndorf–Verley (MPV) reaction is an environmentally-friendly process consisting of the reduction of a carbonyl compound through hydrogen transfer from a secondary alcohol. This work deals with MPV reduction of furfural to furfuryl alcohol on different ZrOx, MgOx, TiOx, and Mg–Ti, as well as Zr–Ti mixed systems. The solids were synthesized through the sol–gel process and subsequently calcined at 200 °C. Characterization was performed using a wide range of techniques: ICP-MS, N2 adsorption-desorption isotherms, EDX, TGA-DTA, XRD, XPS, TEM, TPD of pre-adsorbed pyridine (acidity) and CO2 (basicity), DRIFT of adsorbed pyridine, and methylbutynol (MBOH) test reaction. ZrOx showed the highest conversion and selectivity values, which was attributed to the existence of acid–base pair sites (as evidenced by the MBOH test reaction), whereas the introduction of titanium resulted in the drop of both conversion and selectivity probably due to the increase in Brönsted-type acidity. As for MgOx, it had a predominantly basic character that led to the production of the condensation product of one molecule of furfural and one molecule of acetone, and thus resulted in a lower selectivity to furfuryl alcohol. The TiOx solid was found to be mainly acidic and exhibited both Lewis and Brönsted acid sites. The presence of the latter could account for the lower selectivity to furfuryl alcohol. All in all, these results seemed to suggest that the MPV reaction is favored on Lewis acid sites and especially on acid–base pair sites. The process was accelerated under microwave irradiation.

Selective production of furfuryl alcohol from furfural by catalytic transfer hydrogenation over commercial aluminas

Three commercial aluminas (γ-Al2O3) have been evaluated as inexpensive catalysts in the Meerwein-Ponndorf-Verley (MPV) reaction to reduce furfural (FUR) to furfuryl alcohol (FOL), using isopropanol (i-Pr-OH), 2-butanol (2-bu-OH) and cyclohexanol (CH-OH) as sacrificing alcohol under mild conditions. All γ-Al2O3 have been characterized by XRD, 27Al NMR and FT-IR spectroscopies, NH3-TPD and XPS. The aluminas are active catalysts, giving rise to FOL as main product, with a yield higher than 90% after 6 h at 150 °C. The catalytic data also reveal that linear alcohols, such as isopropanol and 2-butanol, lead to higher FUR conversion values in comparison to cyclohexanol. However, the presence of H2O in the reaction medium has an adverse effect in FUR conversion by the transformation of active Lewis acid sites into Brönsted ones, which are inactive in the MPV reaction.

Ionic liquid accelerates the crystallization of Zr-based metal\u2013organic frameworks

The Zr-based metal–organic frameworks are generally prepared by solvothermal procedure. To overcome the slow kinetics of nucleation and crystallization of Zr-based metal–organic frameworks is of great interest and challenging. Here, we find that an ionic liquid as solvent can significantly accelerate the formation of Zr-based metal–organic frameworks at room temperature. For example, the reaction time is shortened to 0.5 h in 1-hexyl-3-methylimidazolium chloride for Zr-based metal–organic framework formation, while that in the conventional solvent N,N-dimethylformamide needs at least 120 h. The reaction mechanism was investigated in situ by 1H nuclear magnetic resonance, spectroscopy synchrotron small angle X-ray scattering and X-ray absorption fine structure. This rapid, low-energy, and facile route produces Zr-based metal–organic framework nanoparticles with small particle size, missing-linker defects and large surface area, which can be used as heterogeneous catalysts for Meerwein–Ponndorf–Verley reaction.

Catalytic Properties of Hierarchical Zeolites ZrAl-BEA in the Synthesis of 4-Methoxybenzyl sec-Butyl Ether from Anisaldehyde

It was shown that increase of the size and charge of the hydrophilic part of the structure-directing agents leads to increase of the concentration of acid sites in aluminum–zirconium–silicate zeolites possessing hierarchical porosity. This improves their catalytic activity in the production of 4-methoxybenzyl sec-butyl ether from anisaldehyde and 2-butanol by the Meerwein–Ponndorf–Verley reaction.

Structure–reactivity relationship in isolated Zr sites present in Zr-zeolite and ZrO2 for the Meerwein–Ponndorf–Verley reaction

An adequate distribution of co-adsorbed reactants on the catalyst surface determines the activity of Zr-containing materials for the MPV reaction.

Direct use of humic acid mixtures to construct efficient Zr-containing catalysts for Meerwein–Ponndorf–Verley reactions

Humic acid (HA) mixtures from lignite could be directly used to construct Zr-HAs catalysts for MPV reaction of carboxyl compounds.

Impact of Support Oxide Acidity in Pt-Catalyzed HMF Hydrogenation in Alcoholic Medium

Silica and three mixed silica oxides (silica–alumina, silica–niobia, and silica–zirconia) with nominally 5 wt% of the added element (Al, Nb and Zr) were prepared and used as supports for dispersing monometallic Pt-nanoparticles. The presence of the second oxide component on the silica surface influenced some properties of the final samples, like surface area and acidity. The samples acidity was measured in a recirculation adsorption line with 2-phenylethylamine probe, by performing the titrations both in cyclohexane and in methanol to gather the intrinsic and effective acidity, respectively. The acid site density of silica–alumina was the highest compared with the other oxides; in general, an important decrease of acid sites density was determined in methanol. The order of the effective acidity in methanol was different from that determined in cyclohexane only for silica–zirconia and silica–niobia, confirming the peculiar acidity of Nb-oxide compounds in polar liquids: Colloidal spherical platinum nanoparticles were synthesized and then deposited (1 wt%) on the oxide supports. The obtained metallic nanophases were studied in the reduction of 5-hydroxymethylfurfural (HMF) to valuable chemicals such as dimethylfuran, dimethyltetrahydro-furan, 2-hexanol. In particular, this study focused on the impact of the acidity of the oxide supports on reaction selectivity when 2-butanol is used as solvent. When Pt is not present, Nb-doped silica is the most effective catalyst to di-hydroxymethyl furan diether (DHMFDE) derived from Meerwein–Ponndorf–Verley reaction, maintaining its Lewis character also in protic medium. In the presence of Pt, Nb-doped silica, however, presents the higher selectivity to hydrogenolysis products, 5-methyl furan (5-MF).

Zr-SBA-15 Lewis Acid Catalyst: Activity in Meerwein Ponndorf Verley Reduction

Zr-SBA-15 Lewis acid catalyst has demonstrated an outstanding catalytic activity in the reduction of several carbonyl compounds by means of Meerwein Ponndorf Verley (MPV) reaction, using several secondary alcohols, and showing a very high selectivity towards the desired products. Special focus was addressed in the catalytic activity of Zr-SBA-15 material in the production of furfuryl alcohol from furfural, which is an important reaction for the lignocellulosic biomass valorization. In this transformation, both the reaction temperature and the i-PrOH:Furfural molar ratio exert a positive influence on the rate of the MPV transformation, with the influence of the former being much higher. i-propyl-furfuryl ether, a by-product resulting from the etherification of the target product with the sacrificing alcohol, is also found together with the main product. The production of this side-product is highly influenced by the reaction temperature, so that low temperatures and high sacrificing alcohol to substrate molar ratios have to be applied to keep its production at low levels.