Organic Inorganic Hybrid Catalyst Research Articles

Study on Catalytic Oxidatio Benzaldehyde to Benzoic Acid with Keggin Polyoxometalate [(CH<sub>2</sub>)<sub>5</sub>NH<sub>2</sub>]<sub>4</sub>SiW<sub>12</sub>O<sub>40</sub>

The organic–inorganic hybrid catalyst [(CH2)5NH2]4SiW12O40 was prepared by matrix acid and piperidine. The matrix acid was synthesized by sodium molybdate and sodium silicate, and the piperidine was organic ligand. The proposed composition and structure of the catalyst were evidenced by XPS, FT-IR, XRD, TG-DTA and elemental analysis. The results indicated that the heteropoly anions still reserved their Keggin structure in the compound. Its catalytic performance was evaluated in the oxidation of benzaldehyde to benzoic acid. Various reaction parameters were changed to attain the optimal conditions. The optimal reaction conditions were found to be: n(catalyst): n(benzaldehyde)=3.1×10-3:1; n(H2O2)： n(benzaldehyde)=4.5：1; reaction temperature was 80°C; reaction time was 4h. The yield of benzoic acid achieved above 85%.

Fe(III)-salim anchored MCM-41: synthesis, characterization and catalytic activity towards liquid phase cyclohexane oxidation

A novel organic–inorganic hybrid catalyst [MCM-41-FeIII(salim)] was synthesized by covalently anchoring FeIII(salim) complex into the pore channels of MCM-41. The material was synthesized by the co-condensation of tetraethyl orthosilicate (TEOS) and the precursor of salicylaldehyde modified with 3-aminopropyl triethoxysilane in the presence of cetyltrimethyl ammonium bromide (CTAB). The Fe(III)-salicylideneimine MCM-41 mesoporous silica was generated (in situ) by taking MCM-41-salimH (I) and FeCl3 in ethanol solution. The immobilization of the complex on the functionalized silica was confirmed by small angle X-ray diffraction (XRD), N2 adsorption–desorption, electron paramagnetic resonance (EPR), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance UV–vis spectroscopy. Solid state CP-MAS NMR spectroscopy of 29Si (29Si CP-MAS NMR) showed a highly condensed siloxane network. Catalytic activity of the supported catalyst was examined by the oxidation of cyclohexane. Cyclohexane was successfully oxidized in good conversion (68%) to cyclohexanone, as a major product with 72% selectivity using tert. butylhydroperoxide as oxidant and acetonitrile as solvent. The catalysts can be reused up to three cycles without losing much of its activity. Fe(III)-salicylideneimine immobilized MCM-41 hybrid mesoporous silica was prepared by covalent anchoring of schiffbase complex to MCM-41 host and used for liquid phase oxidation of cyclohexane.

Hydroxylation of Benzene to Phenol by Molecular Oxygen over an Organic–Inorganic Hybrid Catalyst: Schiff Base Manganese Complex Attached to Molybdovanadophosphoric Heteropolyacid

The organic–inorganic hybrid catalyst L-Mn-PMoV was prepared simply by combining a schiff base Mn complex (L-Mn, L: N,N′-disalicylidene-1, 6-hexanediamine) with the Keggin-structured molybdovanadophosphoric heteropolyacid (PMoV). The proposed composition and structure of the catalyst were evidenced by TG, elemental analysis, FT-IR, and UV–Vis characterizations. Its catalytic performance was evaluated in the direct hydroxylation of benzene to phenol by molecular oxygen with ascorbic acid as the reducing agent. Various reaction parameters were changed to attain the optimal conditions. The hybrid catalyst has a formula [{Mn(C20H22N2O2)(Cl)}2(H4PMo11VO40)], with the two terminal oxygen atoms in the PMoV Keggin structure coordinately linked to the two Mn(III) ions in two L-Mn units, respectively. It exhibits a remarkably enhanced yield to phenol compared to the pure PMoV due to the synergy effect between the Schiff-base manganese complex and PMoV.

Long Chain Aliphatic Amine-Modified Heteropolyacid Catalysts for Hydroxylation of Benzene to Phenol with Molecular Oxygen

Organic-inorganic hybrid catalysts were prepared by combining laurylamine (or octadecylamine) and molybdovanadophosphoric acid, and their catalytic performance for the hydroxylation of benzene to phenol was evaluated using molecular oxygen as the oxidant in a pressured batch reactor. The laurylamine-modified heteropolyacid catalyst with a 4:1 molar ratio for the two moieties exhibited a much higher yield of phenol (11.5%) than that of the neat heteropolyacid H5PMo10V2O40 (3.9%). We discuss the promotional effect of the long chain aliphatic amines with regards to the interaction between the amine and the heteropolyacid framework, and we also discuss the “pseudo-liquid phase” behavior of the heteropolyacid.

Mesoporous SBA-15 materials modified with oxodiperoxo tungsten complexes as efficient catalysts for the epoxidation of olefins with hydrogen peroxide

A hybrid mesoporous SBA-15 material ( 2a) containing an oxodiperoxo tungsten complex of the type [WO(O 2) 2L] (L = pyrazolylpyridine) was synthesized by a post-grafting route. The organic–inorganic hybrid catalyst was characterized by means of XRD, N 2 adsorption–desorption and FT-IR. The catalytic property of 2a in the epoxidation of cyclooctene with H 2O 2 as the oxidant was investigated in comparison with other three kinds of hybrid tungsten containing SBA-15 materials bearing ethylenediamine, imidazole or 4,4′-bipyridine ligands. It was found that all oxodiperoxo tungsten catalysts were active at the reaction temperature of 55 °C with CH 3CN as solvent. However, only the catalyst with the pyrazolylpyridine ligand showed good recoverability and relatively high stability against leaching of active tungsten species. Moreover, this catalyst showed very high efficiency for H 2O 2 utilization, and its catalytic activity could be further improved by using solvent mixtures of CH 3CN and CH 3COOH.

ChemInform Abstract: Highly Active and Robust Organic—Inorganic Hybrid Catalyst for the Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Metal-doped epoxy resins: Easily accessible, durable, and highly versatile catalysts

Thermosetting epoxy resins, such as the triglycidyl derivative of 4-aminophenol, can be polymerized using molybdenum, palladium, or rhodium complexes as initiators. The resulting metal-doped materials proved to be efficient catalysts for epoxidation, carbon–carbon coupling, hydrogenation, and hydroformylation reactions. Propylene oxide yields of around 50% were obtained in the epoxidation of propylene with tert-butyl hydroperoxide as the oxidant, and biphenyl yields of ⩾98% were observed in the Suzuki coupling of iodobenzene with phenylboronic acid. Almost quantitative conversions were accomplished in the hydrogenation of ethyl crotonate, ethyl cinnamate, and croton aldehyde, whereas aldehyde yields of around 16% were obtained in the hydroformylation of 1-octene. Organic–inorganic hybrid catalysts can be obtained in a convenient one-step procedure by the addition of inorganic components to the liquid resins and subsequent polymerization. Different metal species can be combined in one thermoset matrix, affording multifunctional catalysts that can be us in various catalytic liquid-phase transformations. Quantification of metal traces in the reaction mixtures by metal enrichment and atomic spectroscopy demonstrated very low metal losses of the catalysts. The catalysts can be simply recovered by filtration and reused without reconditioning while maintaining stability, activity, and selectivity.

Performance of organic–inorganic hybrid catalysts based on Ia-3 d mesoporous silica

The cubic Ia-3 d mesoporous silica with ordered large pores was synthesized from tetraethoxysilane (TEOS) and a small amount of 3-mercaptopropyltorimetoxysilane (MPTS) as the silica sources under the acidic conditions by using triblock copolymer P123 (EO 20PO 70EO 20) as a surfactant. After removal of the surfactant by the solvent extraction method, mercaptopropyl (MP) group (–CH 2CH 2CH 2SH) remained inside pores with a slight loss. The pore diameter of this mesoporous silica was about 5 nm. After converting the MP group to sulfopropyl (SP) group (–CH 2CH 2CH 2SO 3H) by the oxidation with H 2O 2, the amount of organic group was significantly reduced. However, it was possible to introduce additional organic groups by post-synthetic grafting. It was also possible to graft both MP and SP groups at the same time, and cooperative effect was observed in the acid-catalyzed condensation reaction of phenol with acetone. More organics were immobilized to the multi-dimensional cubic Ia-3 d structure than the one-dimensional 2d-hexagonal structure. The catalyst having both SH and SO 3H groups showed much higher selectivity for bisphenol A than Amberlyst 15 and Nafion SAC-13, which could be explained by the SH group-assisted mechanism.

Highly active and robust organic–inorganic hybrid catalyst for the synthesis of cyclic carbonates from carbon dioxide and epoxides

A high-throughput combinatorial strategy enabled us to find a highly active organic–inorganic hybrid catalyst for the production of cyclic carbonates from CO2 and epoxides. The best hybrid catalyst 1a was prepared by the coupling of 3-(triethoxysilyl)propyltriphenylphosphonium bromide and mesoporous silica, and the organic and inorganic moieties had a synergistic effect on catalytic activity. The pore size of silica was found to be important for catalysis; mesoporous silica with the mean pore size of 19 nm exhibited much better performance than silica with that of 6 nm. The solvent-free and metal-free reactions proceeded successfully under very mild conditions (1 MPa, 90 °C, 1 mol% loading of catalyst, 6 h), and the hybrid catalyst could be recycled ten times.

Organic–Inorganic Hybrid Catalysts Based on Ordered Porous Structures for Carbon–Carbon Bond Forming Reactions

Two types of organic–inorganic hybrid base catalysts are prepared. Organic-functionalized molecular sieves (OFMSs); in particular, “amine-immobilized porous silicates” are designed based on common idea to immobilize catalytic active sites on silicate surface. Silicate–organic composite materials (SOCMs), such as “ordered porous silicate–quaternary ammonium composite materials”, are the precursors of ordered porous silicates obtained during the synthesis. Both the OFMS and the SOCM are used as the catalysts for Knoevenagel condensation and Michael addition reactions. Among the OFMSs, there is clear tendency that the use of molecular sieve with larger pore volume and/or surface area gives the product in higher yield. Aminopropylsilyl (AP)-tethered mesoporous silicate such as AP-MCM-41 gives the Knoevenagel condensation product in high yield under mild conditions. No loss of activity is observed after repeated use for three times. The SOCMs are also active for the same reaction. The OFMSs are effective when the supports have large pore volume and/or surface area and the reaction is carried out in polar solvents ethanol and DMF. However, the activity of the OFMSs is considerably low in a non-polar solvent such as benzene. In contrast, the SOCMs are remarkably active in benzene. The organic cation–MCM-41 composite is more active than the composite of an organic cation and a microporous silicate such as zeolite beta and ZSM-12. In the SOCM catalysts, (SiO)3SiO−(+NR4) moieties located at the accessible sites are considered to play some important roles. The active species are absent in the liquid phase after the reaction. The recycle of the catalyst was possible without significant loss of activity when the substrates are enough reactive. The mechanism of the reaction over SOCM catalyst is discussed.

Hydrolysis of oligosaccharides from distillers grains using organic–inorganic hybrid mesoporous silica catalysts

The use of propylsulfonic acid-functionalized mesoporous silica as a catalyst for the hydrolysis of oligosaccharides released by hydrothermal pretreatment of distiller’s grains was examined in batch reactor studies. The effectiveness of the catalyst system for oligosaccharide hydrolysis was found to improve significantly with increased reaction temperature. This higher temperature operation allowed for more selective recovery of glucose, but was detrimental to arabinose recovery since significant degradation occurred. Xylose recovery efficiency improved with increasing temperature, but the higher temperature led to increased degradation. Using a model feed, solubilized proteins were found to deactivate the organic–inorganic hybrid catalyst, but a simple pretreatment with activated silica was found to alleviate the deactivation.

Organic–inorganic hybrid catalysts based on ordered porous structures for Michael reaction

Two types of organic–inorganic hybrid base catalysts are prepared for the Michael reaction. Organic-functionalized molecular sieves (OFMSs), particularly “amine-immobilized porous silicates”, are designed based on a common idea of immobilizing active catalytic sites on silicate surface. Silicate-organic composite materials (SOCMs), such as “ordered porous silicate-quaternary ammonium composite materials”, are the precursors of ordered porous silicates obtained during the synthesis. The OFMSs are effective when the supports have large pore volume and/or surface area and the reaction is carried out in polar solvents ethanol and DMF. However, the activity of the OFMSs is considerably low in a non-polar solvent such as benzene. In contrast, the SOCMs are remarkably active in benzene. The organic cation-MCM-41 composite is more active than the composite of an organic cation and a microporous silicate such as zeolite beta and ZSM-12. In the SOCM catalysts, (SiO) 3SiO −( +NR 4) moieties located at the accessible sites are considered to play some important roles. The active species are absent in the liquid phase after the reaction. The recycle of the catalyst was possible without significant loss of activity when the substrates are enough reactive.

Zeolite-based organic–inorganic hybrid catalysts for phosgene-free and solvent-free synthesis of cyclic carbonates and carbamates at mild conditions utilizing CO 2

As-synthesized zeolite-beta exhibits high catalytic activity for the synthesis of cyclic carbonates and alkyl and aryl carbamates by a phosgene-free route, utilizing the greenhouse effect gas CO 2. The reaction occurs with high yields of the desired products at mild conditions and without using any solvent or cocatalyst. Cyclic carbonates are synthesized by cycloaddition reaction of CO 2 with oxiranes (epichlorohydrin, propene oxide, styrene oxide and n-butene oxide) at 393 K and 6.9 bar. Alkyl and aryl carbamates are synthesized by the reaction of the corresponding amines, CO 2 and n-butyl bromide at 353 K and 3.4 bar. The as-synthesized zeolite-beta containing the encapsulated quaternary ammonium ions is not only reusable in several recycling experiments, but also shows superior activity to that of the corresponding homogeneous, quaternary ammonium halide salt generally used in the commercial synthetic practice. The microporous silica (inorganic) acting in concert with the encapsulated organic component constitutes an efficient, recyclable catalyst for this reaction.

Proline and benzylpenicillin derivatives grafted into mesoporous MCM-41: Novel organic-inorganic hybrid catalysts for direct aldol reaction

New organic-inorganic hybrid catalysts were synthesized by covalent grafting of proline and benzylpenicillin derivatives into mesoporous MCM-41. These catalysts were extensively characterized using FT-IR,13C CP MAS solid stateNMR, XRD and TEM techniques. These were used as catalysts for direct, asymmetric aldol reaction between acetone and activated aromatic aldehydes. In the reaction of 4-nitro and 4-fluoro benzaldehyde, the aldol products were obtained in 36% and 59%ee respectively. The catalysts were reusable with neither significant drop in enantioselectivity nor loss of mesostructure. An attempt was made to substantiate the proposed ’enamine’ mechanism for direct aldol reaction by trapping the intermediate between proline-MCM-41 and acetone.

Design and Preparation of Organic—Inorganic Hybrid Catalysts

AbstractFor Abstract see ChemInform Abstract in Full Text.

Design and preparation of organic-inorganic hybrid catalysts.

Solid catalysts provide numerous opportunities for recovering and recycling catalysts from reaction environments. These features can lead to improved processing steps, better process economics, and environmentally friendly industrial manufacturing. Thus, the motivating factors for creating recoverable catalysts are large.

Organic–inorganic hybrid catalysts for acid- and base-catalyzed reactions

Stable heterogeneous catalysts with adjustable base strength have been prepared by grafting organic amine bases into the the pores of the inorganic mesoporous material, MCM-41, and to a porous styrene–divinylbenzene resin. The activities of these catalysts are compared for the formation of the monoglyceride from lauric acid and glycidol, and the Knoevenagel condensation of heptaldehyde with benzaldehyde to form α-n-amylcinnamaldehyde (jasminaldehyde). Also included in the comparison are catalysts prepared by incorporating K 2O, BaO and K 2O/La 2O 3 into MCM-41. The resin-based catalyst suffers from poor thermal and mechanical stability. The organic–inorganic hybrid material containing the strong hindered amine base, TBD (1,5,7-triazabicyclo[4,4,0]dec-5-ene), performs well for the monoglyceride reaction at 110°C, and the catalyst can be re-used for at least 11 cycles with little loss of activity. However, it deactivates if it is used in the coupling reaction with aldehydes. This is obviously caused by loss of the base at the higher reaction temperature of 170°C, and by poisoning of the strong basic sites with benzoic acid which is formed by oxidation or through the Cannizzaro disproportionation of benzaldehyde. The more weakly basic catalysts based on MCM-41 with K 2O/La 2O 3 can be used at a higher reaction temperature to compensate for their lower intrinsic activity, and their activity can be restored by calcination.