Vapor phase reduction of cyclohexanone to cyclohexanol on CexZr1-xO2 solid solutions
01 Jan 2003-Reaction Kinetics and Catalysis Letters (Kluwer Academic Publishers)-Vol. 78, Iss: 1, pp 151-159
TL;DR: In this article, a possible mechanism of hydride transfer has been proposed with cerium ions as promoters, which showed better catalytic activity compared to pure ZrO2 and the selectivity to cyclohexanol is 98%.
Abstract: Reduction of cyclohexanone to cyclohexanol using propane-2-ol as hydrogen donor has been carried out in vapor phase on CexZr1-xO2 solid solutions synthesized by ombustion synthesized at 302°C. The solid solutions around 0.4 mol% cerium content show better catalytic activity compared to pure ZrO2 and the selectivity to cyclohexanol is 98%. A moderate acid-base and good redox properties of CexZr1-xO2 solid solutions are seen to be responsible for the catalytic activity. A possible mechanism of hydride transfer has been proposed with cerium ions as promoters.
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TL;DR: In this article, the effect of rare earth oxide on the catalytic activity of ZnO was investigated, and it was found that adding ceria into zinc oxide was found to increase the catalyst activity for hydrogen transfer reaction.
Abstract: Ce-Zn-O mixed oxides were prepared by amorphous citrate process and decomposition of the corresponding acetate precursors. The resulting materials were characterised by TGA, XRD, UV-Vis-DRS, EPR, SEM and surface area measure- ments. XRD and DRS results indicated fine dispersion of the ceria component in the ZnO matrix. EPR results clearly indicate the presence of oxygen vacancy and defect centres in the composite oxide. Addition of CeO2 to ZnO produced mixed oxides of high surface area compared to the pure ZnO. Hydrogen transfer reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity of ZnO. Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction . The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity.
10 citations
TL;DR: In this paper, the use of Ti/ceramic TiO2 cathode as an effective cathode material for the reduction of two ketones (cyclohexanone and benzalacetone) is highlighted.
Abstract: The use of Ti/ceramic TiO2 cathode as an effective cathode material for the reduction of two ketones—cyclohexanone and benzalacetone (BA) are highlighted. Galvanostatic reduction of these ketones gave exclusively cyclohexanol and benzyl acetone (4-phenyl 2-butanone) as the corresponding hydrogenated products, as characterized from their boiling points and nmr spectra. Higher product yields were observed as compared to the reduction of the ketones at conventional cathode materials like lead under identical experimental conditions. Best conditions for the formation of products have been identified based on current density, temperature and acid strength. Cyclic voltammetry indicates a mechanism involving heterogeneous redox catalysis involving the surface fixed redox groups Ti4+/Ti3+. The reaction can be conveniently scaled up.
6 citations
Dissertation•
01 Jan 2012
TL;DR: In this article, a series of MoO3-ZrO2 nanocomposite oxides with MoO 3 content in the range of 2-50 mol% were prepared by coprecipitation, impregnation and combustion synthesis methods.
Abstract: A series of MoO3-ZrO2 nanocomposite oxides with MoO3 content in the range of 2-50 mol% were prepared by coprecipitation, impregnation and combustion synthesis methods. The synthesized materials were characterized using different analytical techniques such as XRD, UV-Vis, SEM, TEM, Sorptometric and Raman techniques. The presence of MoO3 in the zirconia matrix found to selectively stabilize the tetragonal phase of zirconia. The crystallite size, surface area and the amount and strength of the acidic sites on the catalyst surface strongly depend on the molybdenum oxide content and the method of preparation. UV-Vis and Raman study of the composite oxide indicated the presence of isolated molybdate and polymolybdate clusters at low molybdna content whereas at higher loading presence of bulk type polymolybdates are observed on zirconia matrix. The effect of fuel nature and content of on the physicochemical characteristics of the MoO3-ZrO2 nanocomposite oxides was studied by taking three different fuel (urea, glycine and hexamethylenetetraamine) and F/O ratio in the range 0.5-1.5 in the combustion method. Nanocomposite oxides with better physicochemical properties are obtained using glycine as fuel. The catalytic activity of the coprecipitated samples was evaluated for the one pot synthesis of amidoalkylnaphthols and acetamidoketones. Similarly, the combustion synthesized samples were used as an efficient and environmentally benign catalyst for the synthesis of octahydroquinazolinones by multicomponent condensation reaction of dimedone, urea and arylaldehydes in aqueous media as well as under solvent free condition using microwave irradiation. Iron stabilized zirconia materials were prepared by coprecipitation method. Sulfate ions are grafted to the Fe2O3-ZrO2 surface by post sulfation method. The sulfate grafted Fe-Zr materials were characterized by XRD, UV-Vis, FTIR, SEM and TEM techniques. XRD study indicated the formation of a substitutional solid solution and selective stabilization of the tetragonal phase of zirconia. The presence of iron oxide in zirconia lattice improves the sulfate retention capacity of host zirconia. The catalytic application of SO42-/FeZr catalysts was studied for one pot synthesis of octahydroxanthene by condensation of dimedone and aryl aldehydes under solvent freecondition and microwave irradiation. The catalyst was found to be highly efficient for synthesis of structurally diverse octahydroxanthene giving good yield and purity of the products. Zr-pillared clay (Zr-P) was synthesized by insertion of zirconium oxyhydroxy clusters into clay interlayer and subsequent thermal activation. The Zr-P materials were treated with sulfuric acid to graft sulfate ions onto the zirconia nanopillars. The sulfate grafted Zr-pillared clay (SZr-P) was used as support for phosphomolybdic acid (PMA/SZr-P). The synthesized materials were characterized by XRD, IR, UV–Vis, SEM and sorptometric techniques. The expansion of the clay lattice as a result of pillaring was confirmed from X-ray diffraction study. The interlayer space was found to be retained in the PMA/SZr-P material. All pillared clay materials show Type-I sorption isotherm typical of microporous materials. The structural integrity of the phosphomolybdic acid in the clay matrix was ascertained from the IR and UV-Vis spectroscopy. The PMA/SZr-P material was used as an efficient catalyst for the one pot synthesis of -aminocarbonyl compounds by Mannich reaction in aqueous media. The multicomponent condensation of aryl aldehyde, amines and ketones using PMA/SZr-P material afforded a variety of -aminocarbonyl compounds in excellent yield and purity. Ceria based nanocomposite oxides, CeO2-CaO and CeO2-MgO, of different compositions were prepared by amorphous citrate process and citrate gel combustion process. These materials were characterized by using different analytical techniques such as XRD, TGA, UV-Vis-NIR, SEMand TEM. The XRD analysis of the CeO2-CaO oxide indicated the presence of a substitutional type solid solution for ceria rich composite oxides where as for the calcium oxide rich composite oxides, the presence of crystalline CaO was observed along with the solid solution phase. In case of CeO2-MgO material, a minor contraction in the lattice parameter was observed for the ceria component which has been ascribed to the formation of a small amount of nonequilibrium MgxCe1-x/2O2 solid solution. The catalytic activity of CeO2-CaO materials was evaluated for the aqueous phase synthesis of 2-amino-2-Chromenes in aqueous media. Similarly, CeO2-MgO nanocomposite oxides were used as heterogeneous catalyst for synthesis of β-nitro alcohols andarylidenemalononitriles. For the synthesis of both classes of compounds, the composite oxides showed excellent catalytic activity giving good yield and purity of products under ambient condition.
2 citations
References
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TL;DR: A statistical survey of industrial processes using solid acid-base catalysts is presented in this paper, where the number of processes such as alkylation, isomerization, amination, cracking, etherification, etc.
Abstract: A statistical survey of industrial processes using solid acid–base catalysts is presented. The number of processes such as alkylation, isomerization, amination, cracking, etherification, etc., and the catalysts such as zeolites, oxides, complex oxides, phosphates, ion-exchange resins, clays, etc., are 127 and 180, respectively. The classification of the types of catalysts into solid acid, solid base, and solid acid–base bifunctional catalysts gives the numbers as 103, 10 and 14, respectively. Some significant examples are described more in detail. On the basis of the survey, the future trend of solid acid–base catalysis and the fundamental research promising for industrial success are discussed.
972 citations
TL;DR: In contrast to these extensive studies of heterogeneous acidic catalysts, fewer efforts have been given to the study of heterogenous basic catalysts as mentioned in this paper. But these studies have been continuous and progressed steadily, and they have never been reviewed in the chemical Reviews before.
Abstract: Heterogeneous acid catalysis attracted much attention primarily because heterogeneous acidic catalysts act as catalysts in petroleum refinery and are known as a main catalyst in the cracking process which is the largest process among the industrial chemical processes. In contrast to these extensive studies of heterogeneous acidic catalysts, fewer efforts have been given to the study of heterogeneous basic catalysts. The types of heterogeneous basic catalysts are listed in Table 1. Except for non-oxide catalysts, the basic sites are believed to be surface O atoms. The studies of heterogeneous catalysis have been continuous and progressed steadily. They have never been reviewed in the chemical Reviews before. It is more useful and informative to describe the studies of heterogeneous basic catalysis performed for a long period. In the present article, therefore, the cited papers are not restricted to those published recently, but include those published for the last 25 years. The paper first describes the generation of basic sites before describing methods used in the characterization of basic surfaces. These are indicator methods, temperature programmed desorption (TPD) of CO{sub 2}, UV absorption and luminescence spectroscopies, TPD of H{sub 2}, XPS, IR of CO{sub 2}, IR of pyrrole, and oxygen exchange betweenmore » CO{sub 2} and the surface. The paper then discusses studies on the catalysis by heterogeneous basic catalysts. Some of these reactions are dehydration, dehydrogenation, hydrogenation, amination, alkylation, ring transformation, and reactions of organosilanes. Catalysts discussed are single component metal oxides, zeolites, non-oxide types, and superbasic catalysts. 141 refs.« less
913 citations
TL;DR: In this paper, the importance of acid-base bifunctional catalysis by ZrO2 and its mixed oxides is emphasized, and industrial applications of Zr O2 catalysts are demonstrated.
Abstract: Examples of acid-base bifunctional catalysis by ZrO2 and its mixed oxides are summarized. The hydrogenation of olefins, carbon monoxide and aromatic carboxylic acids over ZrO2 are also examples of acid-base bifunctional catalysis which occur by heterolytic splitting of a hydrogen molecule (H2) into a proton (H+) and a hydride ion (H−) on the acid-base pair sites. Industrial applications of ZrO2 catalysts are demonstrated, the importance of acid-base bifunctional catalysis by ZrO2 and its mixed oxides being emphasized.
287 citations
TL;DR: In this paper, the authors investigated the preparation of high surface area, three-way catalysts (TWC)-like, ceria-zirconia mixed oxide and showed that under basic conditions cationic surfactants effectively incorporate into hydrous oxides of cerium and zirconium.
Abstract: The study investigates the preparation of high surface area, three-way catalysts (TWC)-like, ceria–zirconia mixed oxide. It is shown that under basic conditions cationic surfactants effectively incorporate into hydrous oxides of cerium and zirconium. The presence of cerium inhibits the action of alkyl-trimethyl-ammonium salts as true templating agents and there is no formation of a regular pore structure. The elimination of surfactants upon calcination gives rise to the formation of high surface area, fluorite-structured CeO2–ZrO2 solid solution characterized by a fairly good compositional homogeneity. Surface areas in excess of 230 m2/g were obtained after calcination at 723 K, which drop to ca. 40 m2/g following treatment at 1173 K.
212 citations
203 citations