Search results for " catalysts"

Photocatalytic and Catalytic Oxidation of 2-Propanol over Au/TiO2-CeO2 Catalysts

2016

Photocatalytic and catalytic oxidation of 2-propanol (representative VOC’s compound) were compared over mixed (Au)TiO2-CeO2-based catalysts. The role of support in Au catalyzed oxidation reaction under photo and dark conditions was studied. In the photocatalytic oxidation CeO2 had a negative effect on the performance towards the alcohol conversion of both TiO2-CeO2 and Au/TiO2-CeO2 catalysts, being Au/TiO2 the most active system. On the contrary mixed TiO2-CeO2 and Au/TiO2- CeO2 samples showed a higher catalytic oxidation efficiency for 2-propanol conversion compared to the single oxides.

Iminium Catalysis (n → π*)

2016

Enhanced NiO Dispersion on a High Surface Area Pillared Heterostructure Covered by Niobium Leads to Optimal Behaviour in the Oxidative Dehydrogenatio…

2020

[EN] A Nb-containing siliceous porous clay heterostructure (PCH) with Nb contents from 0 to 30 wt %) was prepared from a bentonite and used as support in the preparation of supported NiO catalysts with NiO loading from 15 to 80 wt %. Supports and NiO-containing catalysts were characterised by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The characterisation studies on Nb-containing supports showed the presence of well-anchored Nb(5+)species without the formation of Nb(2)O(5)crystals. High dispersion of nickel oxide with low crystallinity was observed for the Nb-containing PCH supports. In addition, when NiO is supported on these Nb-containi…

Hydrogenolysis of hydroxymatairesinol on Y derived catalysts: a computational study

2010

Hydrogenolysis of 7-hydroxymatairesinol (HMR) to matairesinol (MAT) occurs on palladium supported acidic catalysts. HMR has three stereochemical centres and naturally exists as a mixture of two diastereoisomers, namely RRR-HMR and SRR-HMR. The latter is significantly more reactive than the former, in the reaction above. In order to elucidate the hydrogenolysis mechanism, simple surface events involving HMR derivatives on aluminated faujasite (H-Y) fragments were simulated by quantum chemical calculations. The metallic function of a Pd/H-Y acidic catalyst was also mimicked by a minimal palladium cluster. Stereochemical evidences pointed already out that water β-elimination on the epimeric ce…

Carbons from second generation biomass as sustainable supports for catalytic systems

2018

In this study activated carbons were produced from the wood of three different wood species (pine, birch, spruce). The resulting activated carbons were characterized in bulk for ash content, carbon content (elemental analyses), specific surface area, and pore size distribution, and at the surface by measuring the autogenerated pH and studying their structure by XPS. All the samples presented high surface areas and appeared to be mesoporous materials (mesopores >80%). The carbons were then used as support for AuPt nanoparticles and tested in the liquid phase oxidation of glycerol (GLY) and in the hydrogenation of levulinic acid (LA), two important chemicals from cellulose-based biomass. The …

NiO diluted in high surface area TiO2 as efficient catalysts for the oxidative dehydrogenation of ethane

2017

[EN] Catalysts consisting of NiO diluted in high surface area TiO2 can be as efficient in the oxidative dehydrogenation of ethane as the most selective NiO-promoted catalysts reported previously in the literature. By selecting the titania matrix and the NiO loading, yields to ethylene over 40% have been obtained. In the present article, three different titanium oxides (TiO2) have been employed as supports or diluters of nickel oxide and have been tested in the oxidative dehydrogenation of ethane to ethylene. All TiO2 used present anatase as the main crystalline phase and different surface areas of 11,55 and 85 m(2) g(-1). It has been observed that by selecting an appropriate nickel loading …

Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts

2009

[EN] Alkali metal-doped MoVSbO catalysts have been prepared by impregnation of a MoVSbO-mixed oxide (prepared previously by a hydrothermal synthesis) and finally activated at 500 or 600 degrees C in N-2. The catalysts have been characterized and tested for the selective oxidation of propane and propylene. Alkali-doped catalysts improved in general the catalytic performance of MoVSbO, resulting more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free MoVSbO catalysts. However, the specific behaviour strongly depends on both the alkali metal added and/or the final activation temperature. At isoconversion conditions, catalysts activated at 600 degrees…

On thermal behaviour of DMC catalysts for ring opening polymerization of epoxides

2016

Abstract The thermoanalytical studies of two types of the double metal cyanide catalysts were carried out. The identity of the catalysts was characterized by an elemental analysis and FTIR. The thermoanalytical examinations performed with the use of TG-DSC, EGA-FTIR, EGA-MS shed new light on views of the bonding of the ligands in the DMC. The chemical justification of the processes responsible for the TG/DSC steps was proposed. Several organic ligand complexing states were found in both types of catalysts. The ligand-DMC bondings were decomposing stepwise in relatively low temperature ranges, which could suggest their negligible role at catalytic reaction being performed usually at higher t…

Electrosynthesis of Ce–Co Mixed Oxide Nanotubes with High Aspect Ratio and Tunable Composition

2008

Cerium oxide and cobalt oxides have attracted the interest of several researchers due to their potential application in several technological fields electrochromism, lithium batteries, catalysis, etc.. Ceria has been used as a promoter in the so-called “three-way catalyst” for the control of toxic emission from automobile exhaust. The promotion consists of the enhancement of the noble metal dispersion, as well as stabilization of the supporting medium toward thermal sintering. 1,2 A direct catalytic effect of CeO2 in chemical processes such as water–gas shift reaction or NOx decomposition has been also evidenced. 3,4

Recyclable Catalyst Reservoir: Oxidation of Alcohols Mediated by Noncovalently Supported Bis(imidazolium)-Tagged 2,2,6,6-Tetramethylpiperidine 1-Oxyl

2013

Bis(imidazolium)-tagged 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) catalysts were adsorbed on different supports such as silica gel, silica gel modified with highly cross-linked polymeric imidazolium networks, and highly cross-linked polymeric imidazolium networks entrapping magnetic particles. These systems provided a convenient tool for the oxidation of both primary and secondary alcohols working as recyclable reservoirs for the bis(imidazolium)-tagged TEMPO catalysts. By using EPR spectroscopy it was demonstrated that the catalyst was released as the corresponding oxoammonium salt in the solution during the recycling step, thus promoting the oxidative process in a homogeneous fashion. …