1,721,030 research outputs found
Cu/SiO2 and Cu/SiO2-TiO2 catalysts: identification of the active sites for the oxidative coupling of 2,6-dimethylphenol
No full textPalladium-gold catalysts for H2O2 direct synthesis at room temperature and atmospheric pressure
Full text linkPt/ZnO system: IR study of the vibrational and electronic effects induced by heating in CO atmosphere
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A spectroscopic study of anatase properties. 4. The adsorption of carbon dioxide
No full textCO2 chemisorption at ambient temp. on a via-chloride anatase prepn. was investigated by microgravimetry and IR spectroscopy. Besides a CO2 species linearly held at surface acidic sites, different types of carbonate-like species were formed, revealing the existence of surface basic sites. The nature of surface carbonates varied on varying the sample activation temp. The overall chemisorbed amt. was quite small, indicating that very little surface basicity can be evidenced by a soft acid like CO2. The activity of surface oxygens depends strongly on the hydration degree, as well as on the preadsorption of polar mols., indicating that anatase surface basicity is influenced by the overall polarity of the surface layer
The effect of potassium addition on the surface chemical structure and activity of supported iron. I- FTIR study of CO and NO adsorption on Fe-K/ ZrO2
No full textIR study of low-temperature adsorption. Part I. CO on Aerosil: an interpretation of the hydrated silica spectrum
No full textOn the regeneration of gold nanoparticles for the selective oxidation of furfural
Full text linkInnovative transformations of furfural are highly desired: among these, the synthesis of alkyl furoates can open very interesting perspectives for the use of xyloses, because they can be used
either as solvent or extracting agents in many different industrial plants if produced in larger amounts and at low price.
Currently we are studying the oxidative esterification of furfural on Au/ZrO2 samples without the addition of NaCH3O, a base that would make the process less green and more expensive. The goal of the work herein presented is to investigate the stability and the
reusability of our best Au/ZrO2 samples.
Catalysts were prepared by deposition-precipitation (dp) on calcined support. The oxidative esterification of furfural with oxygen and methanol, without NaCH3O addition, was investigated at 120°C and 12 bar. After the first catalytic run the sample was filtered off, washed with methanol, dried and used again, obtaining very low selectivity in the subsequent runs. As the reason for catalysts deactivation we have excluded gold leaching in the discharged samples. In order to
investigate catalyst poisoning, by TPO analyses we have verified on exhausted catalysts the presence of an organic residue. According to TPO profiles, we have decided to heat the catalyst until 450°C in oxygen atmosphere, in order to eliminate organic poisons. The deactivation in this case is reversible and by thermal calcination at a proper temperature it is possible to restore almost
fully the initial selectivity. In fact, by pulse-flow CO chemisorptions [1] we have found for the regenerated samples a molCO/molAu ratio comparable to the value of the fresh samples, meaning the
absence of gold sintering during the catalytic reaction.
FTIR spectroscopy demonstrated that the organic residue can be removed starting from 350°C in
O2. At the same time, CO adsorption reveals that the Au phase is quite stable, even after repeated thermal treatments in O2 at increasing temperature up to 6 hours
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