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The activity and stability of supported metal catalysts, which exhibit high efficiency and activity, are significantly influenced by the interactions between the metal and the support, that is, metal-support interactions (MSIs). Here, we report an investigation of the MSIs between supported rhenium (Re) and oxide supports such as TiO

We have constructed and analyzed an updated dataset consisting of 4759 experimental datapoints for the oxidative coupling of methane (OCM) reaction based on literature data reported before 2020 (similar to 2019) using machine learning (ML) methods. Several ML methods, including random forest regression (RFR), extra trees regression (ETR), and gradient boosting regression with XGBoost (XGB), were used in conjunction with our proposed approach, in which elemental features are used as input representations rather than inputting the catalyst compositions directly. A recent research trend, namely, the extensive exploration of Mn/Na2WO4/SiO2 catalyst systems in recent years due to their high activity and durability, was clearly reflected in the dataset analysis. An ML model for the prediction of the reaction outcome (C-2 yield) was success- fully developed, and feature importance scores and SHapley Additive exPlanations (SHAP) values were calculated based on ETR and XGB, respectively, to identify the input variables with the greatest influence on the catalyst performance and observe how these important variables affect the C-2, yield in the OCM. The discovery and optimization of catalytic processes using ML as a "surrogate" model were explored, and promising catalytic system candidates for the OCM reaction were identified. Notably, the developed ML model predicted catalysts containing elements that do not appear in the OCM dataset. This clearly demonstrates desirably high potential of our ML model to enable extrapolative predictions for ML-aided future catalysis research.

Catalytic methylation of aromatic hydrocarbons using CO2 and H2 as a methylating agent was conducted over a combination of TiO2-supported Re (Re(1)/TiO2; Re = 1 wt %) and H-β (SiO2/Al2O3 = 40) in a...

A Re catalyst supported on TiO2 (Re/TiO2) promoted the reverse water-gas shift (RWGS) reaction, exhibiting high selectivity toward CO. Operando X-ray absorption near edge structure (XANES) measurements revealed that the redox of Re species was responsible for promotion of the reaction. The Re/TiO2 catalyst also possessed remarkable durability and maintained >99.9% CO selectivity for more than 1000 h.

The reverse water-gas shift (RWGS) reaction is a promising catalytic route for reducing CO2 emissions because its product, CO, is a key intermediate in various industrialized catalytic processes that produce fuels and chemicals. We describe herein a MoOx/TiO2-supported Pt catalyst (Pt(3)/MoOx(15)/TiO2; Pt loading = 3 wt%, MoO3 loading = 15 wt%) that promotes the RWGS reaction at low temperature (200–300 °C) with high activity and selectivity. The catalytic performance for both CO2 conversion and selectivity of Pt(3)/MoOx(15)/TiO2 is better than those of Pt catalysts on other supports and other metal catalysts supported on MoOx(15)/TiO2, as well as Cu– and Fe–Cr-based industrial catalysts. Moreover, results of operando X-ray absorption spectroscopy studies show that the reaction takes place via the reverse Mars–van Krevelen mechanism where H2 acts as a reducing agent to create oxygen vacancies on the supported Mo oxide species that are filled by CO2 as an oxidizing agent.

Hydrolysis of amides to carboxylic acids is an industrially important reaction but is challenging due to the difficulty of cleaving the resonance stabilized amidic C–N bond. Twenty-three heterogeneous and homogenous catalysts were examined in the hydrolysis of acetamide. Results showed that Nb2O5 was the most effective heterogeneous catalyst with the greatest yield of acetic acid. A series of Nb2O5 catalysts calcined at various temperatures were characterized and tested in the hydrolysis of acetamide to determine the effects of crystal phase and surface properties of Nb2O5 on catalytic performance. The high catalytic performance observed was attributed mainly to the facile activation of the carbonyl bond by Lewis acid sites that function even in the presence of basic inhibitors (NH3 and H2O). The catalytic studies showed the synthetic advantages of the present method, such as simple operation, catalyst recyclability, additive free, solvent free, and wide substrate scope (>40 examples; up to 95% isolated yield).

Methods have been reported for the preparation of ω-functionalized alkyl maltoside and glycoside detergents via a simple and inexpensive synthetic route. The key step was stannic chloride-mediated glycosylation of long-chain alcohols or thiols with maltose octaacetate at 0 or –10°C, respectively, within a very short time (isolated yield 17–44%), which provided more than 98% β-selectivity.

We report herein that a commercially available CeO2 is an active and reusable catalyst for the C3-selective alkenylation of oxindole with aldehydes under solvent-free conditions. This catalytic method is generally applicable to different aromatic and aliphatic aldehydes, giving 3-alkyledene-oxindoles in high yields (87%–99%) and high stereoselectivities (79%–93% to E-isomers). This is the first example of the catalytic synthesis of 3-alkenyl-oxindoles from oxindole and various aliphatic aldehydes. The Lewis acid-base interaction between Lewis acid sites on CeO2 and benzaldehyde was studied by in situ IR. The structure-activity relationship study using CeO2 catalysts with different sizes suggests that defect-free CeO2 surface is the active site for this reaction.

The structure and performance of TiO2-supported Re (Re/TiO2) catalysts for selective hydrogenation of carboxylic acid derivatives have been investigated. Re/TiO2 promotes selective hydrogenation reactions of carboxylic acids and esters that form the corresponding alcohols, and of amides that generate the corresponding amines. These processes are not accompanied by reduction of aromatic moieties. A Re loading amount of 5 wt% and a catalyst pretreatment with H-2 at 500 degrees C were identified as being optimal to obtain the highest catalytic activity for the hydrogenation processes. The results of studies using various characterization methods, including X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM), indicate that the Re species responsible for the catalytic hydrogenation processes have sub-nanometer to a few nanometer sizes and average oxidation states higher than 0 and below +4. The presence of either a carboxylic acid and/or its corresponding alcohol is critical for preventing the Re/TiO2 catalyst from promoting production of dearomatized byproducts. Although Re/TiO2 is intrinsically capable of hydrogenating aromatic rings, carboxylic acids, alcohols, amides, and amines strongly adsorb on the Re species, which leads to suppression of this process. Moreover, the developed catalytic system was applied to selective hydrogenation of triglycerides that form the corresponding alcohols.

Transesterification of ethyl-10-undecenoate (derived from castor oil) with 1,4-cyclohexanedimethanol over a recyclable Cu-deposited V

Efficient conversion of CO2 into useful chemicals, exemplified by the development of methods for low-temperature hydrogenation of CO2 to form methanol (CH3OH), is a highly attractive research targe...

The direct catalytic esterification of amides that leads to the construction of C-O bonds through the cleavage of amide C-N bonds is a highly attractive strategy in organic synthesis. While aliphatic and aromatic alcohols can be readily used for the alcoholysis of activated and unactivated amides, the introduction of phenols is more challenging due to their lower nucleophilicity in the phenolysis of unactivated amides. Herein, we demonstrate that phenols can be used for the phenolysis of unactivated amides into the corresponding phenolic esters using a simple heterogenous catalytic system based on CeO2 under additive-free reaction conditions. The method tolerates a broad variety of functional groups (>50 examples) in the substrates. Results of kinetic studies afforded mechanistic insights into the principles governing this reaction, suggesting that the cooperative effects of the acid-base functions of catalysts would be of paramount importance for the efficient progression of the C-N bond breaking process, and consequently, CeO2 showed the best catalytic performance among the catalysts explored.

The use of triglycerides as an important class of biomass is an effective strategy to realize a more sustainable society. Herein, three heterogeneous catalytic methods are reported for the selective one-pot transformation of triglycerides into value-added chemicals: i) the reductive amination of triglycerides into fatty amines with aqueous NH3 under H2 promoted by ZrO2 -supported Pt clusters; ii) the amidation of triglycerides under gaseous NH3 catalyzed by high-silica H-beta (Hβ) zeolite at 180 °C; iii) the Hβ-promoted synthesis of nitriles from triglycerides and gaseous NH3 at 220 °C. These methods are widely applicable to the transformation of various triglycerides (C4 -C18 skeletons) into the corresponding amines, amides, and nitriles.

Hydrogenation of carbon dioxide (CO2) to methanol (MeOH) is an effective strategy for CO2 utilization. Because of a low equilibrium conversion of CO2 to MeOH at high temperature, development of eff...

We report herein the selective N-methylation of amines and nitroarenes with methanol under basic conditions using carbon-supported Pt nanoparticles (Pt/C) as a heterogeneous catalyst. This method is widely applicable to four types of N-methylation reactions: (1) N,N-dimethylation of aliphatic amines under N2, (2) N-monomethylation of aliphatic amines under 40 bar H2, (3) N-monomethylation of aromatic amines under N2, and (4) tandem synthesis of N-methyl anilines from nitroarenes and methanol under 2 bar H2. All these reactions under the same catalytic system showed high yields of the corresponding methylamines for a wide range of substrates, high turnover number (TON), and good catalyst reusability. Mechanistic studies suggested that the reaction proceeded via a borrowing hydrogen methodology. Kinetic results combined with density functional theory (DFT) calculations revealed that the high performance of Pt/C was ascribed to the moderate metal–hydrogen bond strength of Pt.

We investigated the hydration of hydrophobic epoxides and alkynes in water using 24 types of heterogeneous and homogeneous catalysts and found that Hbeta (Hβ) zeolite with a relatively high Si/Al ratio (Si/Al = 75), Hβ-75, is an effective catalyst. Hβ-75 showed wide substrate scope, good reusability, and applicability in gram-scale synthesis for both types of reactions. The effects of hydrophobicity, acidity, and the size of zeolite pores were also comprehensively studied through the hydration of hydrophilic and hydrophobic epoxides and alkynes with different molecular sizes using two types of zeolite (Hβ and HZSM5). The high yields obtained using the Hβ-75 catalyst in the hydration of hydrophobic epoxides and alkynes are attributed to the hydrophobic interaction between zeolite pores with the substrates, as well as the relatively large pore size.

A one-pot, acceptorless dehydrogenative method, using a carbon-supported Pt catalyst (Pt/C) along with KOtBu, has been developed for the synthesis of 2,4,6-trisubstituted pyrimidines from secondary and primary alcohols, and amidines. The reaction takes place efficiently using a wide range of substrate scopes (32 examples with isolated yields up to 92%). The Pt/C catalyst that promotes this process is reusable and has a higher turnover number (TON) than those employed in previously reported methods. The results of mechanistic studies suggest that the process takes place through a pathway that begins with Pt-catalyzed acceptorless dehydrogenation of the alcohol substrate, which is followed by sequential condensation, cyclization, and dehydrogenation. Measurements of the turnover frequency combined with the results of density functional theory calculations on different metal surfaces suggest that the adsorption energy of H on the Pt surface is optimal for the acceptorless dehydrogenation process, which cause...

Heterogeneous catalysis as a part of the biorefinery concept is the key technology to connect the divergence between the transformation of biomass-derived platform molecules with value-added compounds including chemicals, biofuels and its precursors, energy by means of aqueous-phase processing and environmentally benign processes. Recent advancement in the heterogeneous catalysis in biorefineries have encouraging outcomes that apparently highlight the broad benefits of biomass exploitation. As demonstrated by a series of transformation of various molecules including triglycerides, bio-oils, furan and its derivatives, ethanol, lactic acid, succinic acid, levulinic acid, sugars, polyols, etc., employing thermochemical and aqueous-phase processing methodologies that should encourage us to concentrate on the renewable economy-based concept of biorefinery under a green and efficient heterogeneous catalysis method.

The development of heterogeneous catalysts for green chemical synthesis is currently a growing area in catalysis and sustainable chemistry. Especially the use of renewable carbon resources such as carbon dioxide (CO2 ) and biomass-derived compounds (e. g. carboxylic acids, esters, and amides) represent highly attractive research targets. As these substances reside in a high oxidation state, efficient reduction processes are required in order to convert these substrates into useful and value-added chemicals. Moreover, in the interest of mass production, these substrates should be reduced by molecular H2 and a heterogeneous catalyst. In this context, our group has developed advanced catalysts and established design guidelines for catalysts that promote the reductive transformations of carboxylic acid derivatives and CO2 . Our studies show that cooperative catalysis between Lewis-acidic sites on the catalyst support and supported metal nanoparticles are crucial for the success of these challenging hydrogenations. In this review, we summarize the results of our recent studies on the direct synthesis of value-added chemicals from CO2 and carboxylic acid derivatives using supported transition-metal catalysts, and we propose a design concept for heterogeneous catalysts that promote these processes.

The Nb2 O5 surface catalyzes the amidation of carboxylic acids with amines through Nb5+ Lewis acid activation of the C=O group. In this work, DFT calculations were applied to theoretically investigate the C=O bond activation of a model carboxylic acid (acetic acid) on θ-Al2 O3 (110), anatase TiO2 (101), and T-Nb2 O5 (100) surfaces. The adsorption sites, adsorption energies, reaction energy barriers, electronic properties, and vibrational frequency of acetic acid were examined in detail. It was found that the bond activation of the carbonyl group is most efficient on Nb2 O5 , although the adsorption energy is larger on Al2 O3 and TiO2 . The most efficient C=O bond activation on Nb2 O5 results in the lowest energy barrier of C-N bond formation during amidation. The Nb2 O5 surface also shows larger tolerance to methylamine and water molecules than Al2 O3 and TiO2 surfaces. These crucial factors contribute to the highest amidation catalytic reactivity on Nb2 O5 . Furthermore, the position of the mean density of states of the d-conduction band of the active metal site relative to the Fermi energy level correlates well with the efficiency in the C=O bond activation and, consequently, the catalytic activity for amidation. These results suggest that, unlike a classical understanding of strong acid sites of metal oxide surfaces, interaction of a carbonyl HOMO with an unoccupied metal d-orbital, or, in other words, covalent-like interaction between a carbonyl group and metal adsorption site, is relevant to the present system.

Alcoholysis of amides on the CeO 2 surface is investigated from density functional theory (DFT) computations, in situ FT-IR spectroscopy, and catalytic studies. The thermodynamically stable amide bonds are effectively activated by the CeO 2 catalyst under mild conditions in contrast to other metal oxide catalysts. DFT calculations demonstrated that acetamide adsorbed on the CeO 2 surface is attacked by lattice oxygen to give a tetrahedral intermediate in the rate-determining step of the most favorable pathway. This is consistent with the experimental finding that the activity of metal oxide catalysts increases with an increase of the base strength of the catalyst. The strong base sites of CeO 2 are the most important factor for the high reactivity. Interestingly, the nucleophilic attack of lattice oxygen is further assisted by the moderately strong Ce 4+ Lewis acid sites. Our computational results show that the high reactivity is ascribed to a catalytic interplay between the Lewis base and acid pair sites on the CeO 2 surface.

A versatile, selective, and recyclable heterogeneous catalytic method for the methylation of C–H bonds in alcohols, ketones, and indoles with methanol under oxidant-free conditions using a Pt-loaded carbon (Pt/C) catalyst in the presence of NaOH is reported. This catalytic system is effective for various methylation reactions: (1) the β-methylation of primary alcohols, including aryl, aliphatic, and heterocyclic alcohols, (2) the α-methylation of ketones, and (3) the selective C3-methylation of indoles. The reactions are driven by a borrowing-hydrogen mechanism. The reaction begins with the dehydrogenation of the alcohol(s) to afford aldehydes, which subsequently undergo a condensation reaction with the nucleophile (aldehyde, ketone, or indole), followed by hydrogenation of the condensation product by Pt–H species to yield the desired product. In all of the methylation reactions explored in this study, the Pt/C catalyst exhibits a significantly higher turnover number than other previously reported homogen...

Heterogeneous catalysis for the one-pot synthesis of added-value chemicals is a growing area in green chemistry. Among various types of organic transformations that are accessible by this approach, acceptorless dehydrogenative coupling (ADC) reactions have been established as efficient processes that generate various classes of organic compounds via the formation of C–O, C–N, C–S, C–C, and CC bonds. In this review, we summarize recent developments on the one-pot synthesis of organic compounds that are driven by the dehydrogenation of alcohols promoted by supported transition-metal catalysts in the absence of hydrogen acceptors. A major feature of the design of such catalysts is the cooperation between the metal sites and the acid and/or base sites on the metal–oxide supports. Recent examples for the organometallic catalysis of ADC reactions of alcohols are presented and their efficiency is put into contrast with that of related reactions carried out using conventional supported transition-metal catalysts. Finally, aspects pertaining to the mechanism and catalyst design of these new ADC reactions are discussed in the context of directions for future developments in this area.

Among various supported metal nanoparticle catalysts, Pt-loaded carbon (Pt/C) catalysts, including a commercial one, showed the highest yield for selective dehydrogenation of glycerol to lactic acid under oxidant-free, solvent-free, and alkaline conditions. For the reaction with Pt/C, the effects of conditions (type of basic additives, the amount of water, atmosphere, reactor) on the catalytic activity and selectivity were studied. Combined with a reaction pathway in the literature and our result of control reactions, we proposed a strategy for decreasing the selectivity of byproducts. The optimized conditions gave a high turnover number of 69 000. To clarify the structural factors affecting the catalytic activity, we show the effect of electronic states of various transition metals on the activity as well as the effect of Pt particle size on the turnover frequency per surface Pt atom.

TiO2 -supported Re, Re/TiO2 , was found to promote selective hydrogenation of carboxylic acids having aromatic and aliphatic moieties to the corresponding alcohols. Re/TiO2 showed superior results compared to other transition-metal-loaded TiO2 and supported Re catalysts for selective hydrogenation of 3-phenylpropionic acid. 3-phenylpropanol was produced in 97 % yield under mild conditions (5 MPa H2 at 140 °C). Contrary to typical heterogeneous catalysts, Re/TiO2 does not lead to the formation of dearomatized byproducts. The catalyst is recyclable and shows a wide substrate scope in the synthesis of alcohols (22 examples; up to 97 % isolated yield).

The direct catalytic esterification of amides that leads to the construction of C-O bonds through the cleavage of amide C-N bonds is a highly attractive strategy in organic synthesis. While aliphatic and aromatic alcohols can be readily used for the alcoholysis of activated and unactivated amides, the introduction of phenols is more challenging due to their lower nucleophilicity in the phenolysis of unactivated amides. Herein, we demonstrate that phenols can be used for the phenolysis of unactivated amides into the corresponding phenolic esters using a simple heterogenous catalytic system based on CeO

Supported metal nanoparticle catalysts were studied for the hydrodeoxygenation of sulfoxides to sulfides under solvent-free and mild conditions (50–155 °C, 1 or 7 atm H2). The catalytic activity for the model reaction of diphenyl sulfoxide depended on the type of metals, support materials and co-loaded oxides of transition metals (V, Nb, Mo, W, Re). Pt and MoOx co-loaded TiO2 (Pt–MoOx/TiO2) showed the highest activity. Pt–MoOx/TiO2 was reusable after the reaction and was effective for the reduction of various sulfoxides and showed a higher turnover number (TON) than previously reported catalysts. Using Pt–MoOx/TiO2, benzylphenylsulfone was reduced by H2 to give phenylbenzyl sulfide via benzylphenyl sulfoxides, which represented the first example of catalytic conversion of a sulfone to a sulfide by H2. Characterization studies of Pt–MoOx/TiO2 show that the surface of TiO2 is covered by small (or thin layer) Mo oxide species with exposed Mo cations as Lewis acid sites, and 4–5 nm sized Pt metal nanoparticles are supported on the Mo oxide-covered TiO2.

Direct synthesis of trimethylamine through N-methylation of NH3 or its surrogate (NH4HCO3) with both CO2 and H2 has been achieved by employing Pt and MoOx coloaded TiO2 (Pt-MoOx/TiO2). Pt-MoOx/TiO2 was found to be superior to other supported Pt and transition-metal-loaded MoOx/TiO2 catalysts for the trimethylamine synthesis process.

Transesterification of biomass-derived triglycerides with methanol (methanolysis of triglycerides) is a promising method for the industrial production of the biodiesel fuel, fatty acid methyl esters (FAMEs). Herein, we present a simple heterogeneous catalytic method for the selective transformation of triglycerides into FAMEs. For the methanolysis of trilaurin under reflux of methanol, a commercially available high-silica Hβ zeolite (Hβ-75, Si/Al = 75) showed a higher yield of methyl laurate than other zeolite catalysts, metal oxides, and conventional heterogeneous and homogeneous catalysts. Under the optimized conditions, the method was widely applicable to the transformation of various triglycerides (C4–C18 frames) into the corresponding FAMEs (yields of 87–93%). The catalyst was furthermore reusable. Quantitative relationships between acidity, hydrophobicity, and reaction rates versus Si/Al ratio of Hβ zeolite catalysts show that a low affinity to glycerol, which arises from the hydrophobicity of the high-silica zeolites, is an important factor for controlling the catalytic activity.

In this work, proton-exchanged *BEA zeolite with a high Si/Al ratio of 75 (Hβ-75), was demonstrated as an effective catalyst for the acetalization of glycerol with carbonyl compounds. This catalyst system was applicable to various substrates and reusable for at least 4 times with slight decrease in activity. The turnover frequency, based on acid site concentration, increased as a function of Hβ Si/Al ratio, indicating the importance of the zeolite hydrophobic surface properties. The origin of the high efficiency exhibited by Hβ-75 is quantitatively discussed based on kinetic studies, hydrophobicity, and acid site concentration.

The development of heterogeneous catalysts for green chemical synthesis is currently a growing area in catalysis and sustainable chemistry. Especially the use of renewable carbon resources such as carbon dioxide (CO

Pt/Al2O3 and Pt/TiO2 were effective catalysts for the synthesis of 2-substituted benzothiazoles and benzimidazoles from 2-aminothiophenol and 1,2-phenylenediamine with alcohols or aldehydes under acceptor-free and additive-free conditions.

Heterogeneous Pt catalysts (Pt/Nb2O5 and Pt/HBEA) show higher turnover number (TON) than previously reported catalysts for the synthesis of indole via acceptorless dehydrogenative cyclization of 2-(2-aminophenyl)ethanol.

Pt-loaded HBEA (H+-exchanged BEA zeolite) is found to be an effective and reusable heterogeneous catalyst for regioselective N-alkylation of indoles with primary aliphatic and benzylic alcohols under additive-free conditions driven by the borrowing-hydrogen methodology. Structural and mechanistic studies suggest a cooperative mechanism of the Pt0 site on Pt metal clusters and the Bronsted acid site of the zeolite, in which the Pt0 site is responsible for dehydrogenation/hydrogenation steps and the Bronsted acid site is responsible for the regioselective condensation of indoles with aldehydes to the enamine intermediate.

CeO2-supported Pt nanoparticle catalysts enabled the acceptorless dehydrogenative synthesis of 2-substituted quinazolines from 2-aminobenzylamine with aliphatic and benzyl primary alcohols or aldehydes with low catalyst loading, wide substrate scope and good catalyst reusability, demonstrating the first acceptor-free and additive-free catalytic system for this reaction.

Catalytic condensation of dicarboxylics acid and amines without excess amount of activating reagents is the most atom-efficient but unprecedented synthetic method of cyclic imides. Here we present the first general catalytic method, proceeding selectively and efficiently in the presence of a commercial Nb2 O5 as a reusable and base-tolerant heterogeneous Lewis acid catalyst. The method is effective for the direct synthesis of pharmaceutically or industrially important cyclic imides, such as phensuximide, N-hydroxyphthalimide (NHPI), and unsubstituted cyclic imides from dicarboxylic acid or anhydrides with amines, hydroxylamine, or ammonia.

Nickel nanoparticles loaded onto calcium silicate (Ni/CaSiO3) have been prepared by ion-exchange method followed by in situ H2-reduction of the calcined precursor. Ni/CaSiO3 was found to be effective for the catalytic direct synthesis of primary amines from alcohols and NH3 under relatively mild conditions. Various aliphatic alcohols are tolerated, and the turnover number (TON) was higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. Effects of the surface oxidation states and particle size of Ni on the catalytic activity were studied by infrared (IR) investigation of the states of adsorbed CO and transmission electron microscopy (TEM). It is clarified that the surface Ni0 sites on small (3 nm) sized Ni nanoparticles are the catalytically active species. Ni/CaSiO3 was also effective for the alkylation of anilines and aliphatic amines with various alcohols (benzyl and aliphatic alcohols) under additive free conditions; primary amines were converted into secondary amines and secondary amines into tertiary amines.

Supported platinum catalysts have been studied for the acceptor-free dehydrogenative coupling of primary alcohols to esters in the liquid phase under solvent-free conditions in N2 at 180 °C. The activity depends on the support material, and Pt-loaded SnO2 (Pt/SnO2) gives the highest activity. Pt/SnO2 shows higher activity than various transition metals (Ir, Re, Ru, Rh, Pd, Ag, Co, Ni, Cu) loaded on SnO2. The Pt/SnO2 catalyst (1 mol%) selectively converted various primary alcohols to their corresponding esters in moderate to high isolated yield (53–91%). This is the first example of reusable heterogeneous catalysts for the acceptor-free dehydrogenative coupling of primary alcohols to esters under additive-free and solvent-free conditions. Mechanistic and infrared (IR) studies are also shown to discuss the reaction pathway and a possible role of the SnO2 support as Lewis acid sites that activate carbonyl groups of adsorbed aldehyde intermediates.

Supported platinum catalysts have been studied for the reductive amination of levulinic acid (LA) by H2 to N-alkyl-5-methyl-2-pyrrolidones under solvent-free conditions. The activity depends on the type of metal (Pt, Re, Pd, Rh, Ru, Cu, Ni), support material, and coloaded oxides of transition metals (V, Cr, Mo, W, Re). In 24 kinds of catalyst tested, Pt and MoOX (molybdenum oxide) coloaded TiO2 (Pt-MoOX/TiO2) shows the highest activity. Pt-MoOX/TiO2 is effective for reductive amination of LA with wide varieties of amines under mild conditions (3 bar of H2, 100 °C, solvent-free) to give high isolated yield of pyrrolidinones and shows higher turnover number (TON) than previously reported catalysts for reductive amination of LA with an aliphatic amine. The catalyst can be separated from the reaction mixture by filtration, and the recovered catalyst can be reused. This is the first general and reusable heterogeneous catalytic system for the reductive amination of LA. On the basis of mechanistic studies, high ...

Pt and MoO(x) co-loaded TiO2 is found to be highly effective for direct methylation of aliphatic and aromatic secondary amines by CO2 and H2 under solvent-free conditions. This is the first additive-free and reusable heterogeneous catalytic system with acceptable turnover number.

Transition metal-loaded metal oxides are tested for C–C self-coupling of 2-octanol to a higher ketone at 140 °C. Among various catalysts, Pt/CeO2 shows the highest activity and shows good reusability. Pt/CeO2 is effective for the self-coupling of various aliphatic secondary alcohols and α-alkylation of methyl ketones with aliphatic secondary alcohols. A possible reaction mechanism is discussed.

Fe 3+ -exchanged montmorillonite is shown to be an effective and reusable heterogeneous catalyst for the transamidation of various amides and amines under solvent-free condition. The catalyst shows high yields and wide substrate scope.