Search results for "Heterogeneous catalysis"
showing 10 items of 233 documents
Efficient Conversion of Carbon Dioxide by Imidazolium-Based Cross-Linked Nanostructures Containing Polyhedral Oligomeric Silsesquioxane (POSS) Buildi…
2019
Polyhedral oligomeric silsesquioxanes (POSS) have been employed as molecular building blocks for the synthesis of imidazolium cross-linked networks, to be used as heterogeneous catalysts for the conversion of carbon dioxide into cyclic carbonates. Two hybrid materials with different nucleophilic species (bromide and iodide) have been prepared and characterized by means of elemental analysis, 13C and 29Si solid-state NMR spectroscopy, thermogravimetric analysis and IR spectroscopy. The solids were tested as the sole catalyst under metal- and solvent-free reaction conditions showing full selectivity toward the formation of cyclic carbonates. High turnover number (TON) and productivity values,…
Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis
2020
Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission ele…
Green Oxidation of Alcohols to Carbonyl Compounds by Heterogeneous Photocatalysis
2010
Photocatalytic degradation of acid blue 80 in aqueous solutions containing TiO2 suspensions.
2001
The photocatalytic degradation of the anthraquinonic dye Acid Blue 80 in aqueous solutions containing TiO2 dispersions has been investigated. The process has been monitored by following either the disappearance of the dye (via HPLC) and the formation of its end-products (via IC, GC, and TOC analysis). Although a relatively fast decolorization of the solutions has been observed, the mineralization is slower, and the presence of residual organic compounds was evidenced even after long term irradiation, confirming the relevant stability of anthraquinone derivatives. The identification of various unstable intermedi ates formed after low irradiation times was performed by HPLC-MS, allowing us to…
Titania Photocatalysts for Selective Oxidations in Water
2011
Heterogeneous photocatalysis by polycrystalline semiconductor oxides is an unconventional technology that has been mainly applied for the degradation of organic and inorganic pollutants in both the vapor and liquid phase. The application of photocatalysis in synthetic routes has also been researched in recent years, demonstrating its viability as an alternative route in organic chemistry. This work illustrates the main findings in the application of heterogeneous photocatalysis to the oxidation of organic compounds dissolved in water, free of any organic co-solvent. Two main aspects of the oxidative process have been studied: the first one is the partial oxidation of various mono-substitute…
2017
A hybrid bioinspired material with manganese(II) complexes grafted on the surface of a mesostructured porous silica is investigated. The Mn sites mimic the manganese-dependent dioxygenase (MndD), which is an enzyme that catalyses the oxidation of catechol derivatives. The metal complexes were introduced in the silica using a dinuclear complex [Mn2L2(Cl)2(μ-Cl)2] as a precursor with a clickable ligand N,N′-bis[(pyridin-2-yl)methyl]prop-2-yn-1-amine (L). Azide moieties covalently grafted on MCM-41 type mesoporous silica were utilised to anchor the manganese complex through Huisgen cycloaddition using CuBr(PPh3)3 as a catalyst. A second functional group – trimethylsilyl or pyridine—was grafted…
A new efficient, highly dispersed, Pd nanoparticulate silica supported catalyst synthesized from an organometallic precursor. Study of the homogeneou…
2018
[EN] A new Pd(0) catalyst supported on silica UVM-7 has been synthesized from the organometallic [Pd-2(mu-(C6H4) Pp(2))(2)(CH3CN)(4)](BF4)(2) precursor, characterized by the high dispersion, activity, and small size of the palladium nanoclusters fixed on the silica surface. The catalyst was tested for the Suzuki-Miyaura (SM) reaction of different 4-substitutedphenyl halides with phenylboronic acid. The kinetic study concurs with most of the catalytic action was carried out by Pd species originated by the partial solubilization of Pd immobilized on mesoporous silica. The Schmidt's analysis of differential selectivity (SADS) in several competitive SM reactions, together the STEM-HAADF and HRT…
Multilayered supported ionic liquids as catalysts for chemical fixation of carbon dioxide
2011
Multilayered, covalently supported ionic liquid phase (mlc-SILP) materials were synthesized by using a new approach based on the grafting of bis-vinylimidazolium salts on different types of silica or polymeric supports. The obtained materials were characterized and tested as catalysts in the reaction of supercritical carbon dioxide with various epoxides to produce cyclic carbonates. The material prepared by supporting a bromide bis-imidazolium salt on the ordered mesoporous silica SBA-15 was identified as the most active catalyst for the synthesis of cyclic carbonates and displayed improved productivity compared with known supported ionic liquid catalysts. The catalyst retained its high act…
Structural, energetic and kinetic database of catalytic reactions: Benzyl alcohol to benzaldehyde oxidation on MnOx clusters
2021
Abstract Data here reported are connected with the research article “Benzyl Alcohol to Benzaldehyde Oxidation on MnO x Clusters: Unraveling Atomistic Features” Gueci et al. [1] . This work described and discussed structural and energetic results, calculated by Density Functional Theory (DFT). In order to get kinetic information, DFT results were refined by an original approach, which will be shortly described in the following article. The crossed analysis of experimental and computational energetic and kinetic data allowed to (i) reconstruct the complicated lattice that connects the primary and secondary mechanisms of the reaction and (ii) identify alternative process pathways capable of by…
Magnesium chloride modified with organoaluminium compounds as a support of the zirconocene catalyst for ethylene polymerisation
2004
Abstract This work describes the influence of the modification of the MgCl2(THF)2 and MgCl2 magnesium supports with the AlEt2Cl, MAO, AlEt3, AlMe3, and AlEt2Cl alkylaluminium compounds on heterogenisation of the bis(cyclopentadienyl) zirconium(IV) dichloride Cp2ZrCl2 catalyst. It was found that only the MgCl2(THF)2 support modified with AlEt2Cl gave the heterogeneous catalyst. On the contrary, application of a magnesium carrier modified by AlEt3, AlMe3, and MAO compounds only results in a homogeneous zirconocene catalyst.