Search results for "Catalysis"
showing 10 items of 5944 documents
Polymers of Limonene Oxide and Carbon Dioxide: Polycarbonates of the Solar Economy
2018
Limonene epoxide (1,2 limonene oxide) readily reacts with carbon dioxide in a ring opening copolymerization reaction with insertion of CO2 and formation of polycarbonates of exceptional chemical and physical properties. Both poly(limonene carbonate) and poly(limonene dicarbonate) can be synthesized using low cost Zn or Al homogeneous catalysts. This study addresses selected relevant questions concerning the technical and economic feasibility of limonene and carbon dioxide polymers en route to the bioeconomy.
Catalytic effect of Ca and K on CO2 gasification of spruce wood char
2015
Abstract Gasification is one route to produce chemicals and liquid fuels from biomass. The gasification of the char is catalyzed by alkali and alkaline earth metals in the biomass. In this work the catalytic effect of calcium (Ca) and potassium (K) on CO2 gasification of spruce wood was studied using a thermo gravimetric analyzer (TGA). The ash-forming elements were first removed from the wood using an acid leaching method. Then, various concentrations of K and Ca were absorbed to the wood by ion-exchange to carboxylic and phenolic groups, impregnation of K2CO3 or physically mixing of CaC2O4. The prepared spruce samples were placed in a mesh holder and gasified in the TGA at 850 °C in 100% …
Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics
2013
Abstract The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO 2 ) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spin resonance (ESR) spin trapping (ST) techniques with the subsequent identification of free radicals by simulation based fitting (SBF) technique. The radical reaction mechanism, where hydroxyl radical was a primary product of O O bond rupture of PAA, was established taking into account radical reactions, occurring during sonolysis. The potential barriers and the reaction heat were deter…
A PERVAPORATION PHOTOCATALYTIC REACTOR FOR THE GREEN SYNTHESIS OF VANILLIN
2012
Abstract Pervaporation is the ideal membrane separation process to be coupled with photocatalysis for the green synthesis of vanillin from ferulic acid. In fact the operative conditions of the two processes are absolutely congruent and the integration is straightforward even operating with separate equipments. The utilization of a highly selective membrane allows the continuous recovery of vanillin by pervaporation from the reacting solution, so that its oxidative degradation is largely avoided and the yield is substantially enhanced. The effects of the main parameters are analyzed resorting to a mathematical model, which is validated by a comparison with the experimental data. In particula…
Size-activity relationship of iridium particles supported on silica for the total oxidation of volatile organic compounds (VOCs)
2019
12 Figures, 2 Tables.-- Datos suplementarios disponibles en línea en la página web del editor.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Photodegradation of Toluene, m-Xylene, and n-Butyl Acetate and Their Mixtures over TiO2 Catalyst on Glass Fibers
2012
The abatement of typical paint solvent compounds as individuals and in mixtures was carried out in an annular TiO2 supported reactor, for concentrations up to 900 mg C m–3. Two different fiberglass supports were compared, and the catalyst supported over a fiber mat showed better performance, with a lower pressure drop (>35% of reduction) and a slightly higher removal efficiency (about 2%) than that supported over glass wool. For every target compound in the whole range of relative humidity studied (4–75%), the photocatalytic activity increased with the air water content. The removal of the compounds in the binary and ternary mixtures was depressed, even >90% for toluene, compared with indiv…
Heterometallic Titanium-Organic Frameworks as Dual Metal Catalysts for Synergistic Non-Buffered Hydrolysis of Nerve Agent Simulants
2020
Heterometallic metal-organic frameworks (MOFs) can offer important advantages over their homometallic counterparts to enable targeted modification of their adsorption, structural response, electronic structure, or chemical reactivity. However, controlling metal distribution in these solids still remains a challenge. The family of mesoporous titanium-organic frameworks, MUV-101(M), displays heterometallic TiM2 nodes assembled from direct reaction of Ti(IV) and M(II) salts. We use the degradation of nerve agent simulants to demonstrate that only TiFe2 nodes are capable of catalytic degradation in non-buffered conditions. By using an integrative experimental-computational approach, we rational…
Hydroformylation of 1-Octene in Supercritical Carbon Dioxide: Can Alkylation of Arylphosphines with tertButyl Groups Lead to Soluble and Active Catal…
2008
Abstract The possibility of increasing the solubility and activity of rhodium catalysts in the hydroformylation of 1-octene in supercritical carbon dioxide (scCO2) by attachment of tertbutyl (tBu) groups to the triarylphosphine ligand was investigated. The solubility of the parent and monoalkylated ligands in a mixture of gaseous components (CO2/CO/H2) was evaluated by visual observation in a view cell. In the case of triphenylphosphine, introduction of one tertbutyl group does not seem to affect the solubility of the phosphine. When the behaviour of (diphenyl)biphenylphosphine and (para-tertbutyldiphenyl)biphenylphosphine was compared a clear solubilising effect of the tBu group was observ…
Catalytic Dehydration of Fructose to 5-Hydroxymethylfurfural in Aqueous Medium over Nb2O5-Based Catalysts
2021
The catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water was performed in the presence of pristine Nb2O5 and composites containing Nb and Ti, Ce or Zr oxides. In all experiments, fructose was converted to HMF using water as the solvent. The catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, N2 physical adsorption, infrared and Raman spectroscopy and temperature-programmed desorption of NH3. Experimental parameters such as fructose initial concentration, volume of the reacting suspension, operation temperature, reaction time and amount of catalyst were tuned in order to optimize the catalytic reaction process. The highest selectivit…
π-Extended Pyrene-Fused Double [7]Carbohelicene as a Chiral Polycyclic Aromatic Hydrocarbon
2019
A π-extended double [7]carbohelicene 2 with fused pyrene units was synthesized, revealing considerable intra- and intermolecular π–π interactions as confirmed with X-ray crystallography. As compared to the previous double [7]carbohelicene 1, the π-extended homologue 2 demonstrated considerably red-shifted absorption with an onset at 645 nm (1: 550 nm) corresponding to a smaller optical gap of 1.90 eV (1: 2.25 eV). A broad near-infrared emission from 600 to 900 nm with a large Stokes shift of ∼100 nm (2.3 × 103 cm–1) was recorded for 2, implying formation of an intramolecular excimer upon excitation, which was corroborated with femtosecond transient absorption spectroscopy. Moreover, 2 revea…