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- Regali, Francesco, 1971-, et al.
(författare)
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Effect of metal loading on activity, selectivity and deactivation behavior of Pd/silica-alumina catalysts in the hydroconversion of n-hexadecane
- 2014
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 223, s. 87-96
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Tidskriftsartikel (refereegranskat)abstract
- Bifunctional catalysts consisting of palladium on amorphous silica-alumina with different metal loadings (0 wt% to 1.2 wt%) were compared in the hydrocracking/hydroisomerization of n-hexadecane. The reaction conditions were: pressure = 30 bar; temperature = 310 degrees C; hydrogen-to-hexadecane feed molar ratio = 10. Metal loading was found to have a remarkable influence on the initial deactivation rate, which could be related to the formation of carbonaceous deposits. The dependence of activity on the metal-acid site ratio was the typical one for bifunctional hydrocracking where, after reaching a threshold value, the catalytic activity does not appreciably increase with increasing metal loading. On the Pd-containing catalysts, the methane space-time-yield showed a strong dependence on conversion, but no clear relationship with metal surface area, indicating that the formation of methane might not proceed by purely metal-catalyzed hydrogenolysis.
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- Regali, Francesco, 1971-, et al.
(författare)
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Hydroconversion of n-hexadecane on Pt/silica-alumina catalysts : Effect of metal loading and support acidity on bifunctional and hydrogenolytic activity
- 2014
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Ingår i: Applied Catalysis A. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 469, s. 328-339
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Tidskriftsartikel (refereegranskat)abstract
- Bifunctional catalysts based on platinum and amorphous silica-alumina were studied in the hydroconversion of n-hexadecane. The influence of platinum loading and support acidity on activity and selectivity were assessed. The contribution of hydrogenolysis reactions on top of bifunctional hydrocracking was shown to depend not only on metal loading, but also on the effect of support acidity on the intrinsic activity of the platinum sites. The yield of cracking products, and their linear alkane fraction, increased with metal loading, while the isomerization yield was practically independent of the metal content. On a support of high Bronsted acidity, the rate of formation of methane was proportional to the platinum surface area, indicating that dernethylation occurred by metal-cataly ed hydrogenolysis. On the other hand, the methane site-time yield was one order of magnitude lower on a catalyst with negligible Bronsted acidity. Pt-catalyzed hydrogenolysis was also investigated during selective poisoning of acid sites by cofeeding pyridine and comparing the effect of hydrogen partial pressure on reaction rates. In the presence of pyridine, total hydroconversion activity was reduced by one order of magnitude while rates to methane and linear cracking products remained relatively high. These observations indicate that acid sites do not intervene in the mechanism, but that support acidity affects the hydrogenolytic activity of platinum sites.
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- Suárez París, Rodrigo, et al.
(författare)
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Hydroconversion of paraffinic wax over platinum and palladium catalysts supported on silica–alumina
- 2016
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 275, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Two bifunctional catalysts consisting of platinum or palladium supported on amorphous silica–alumina were prepared and tested in hydrocracking/hydroisomerization of paraffinic wax. The performance of both noble metals was studied at the following reaction conditions: P = 35 bar; T = 300–330 °C; H2/wax = 0.1 wt/wt; WHSV = 1–4 h−1. The platinum sample was more active in hydrocracking of C22+ compounds and more selective to middle distillates. On the other hand, the palladium-based catalyst resulted in a higher isomerization degree of the products and lower amounts of methane and ethane. The higher production of light compounds over platinum is attributed to a monofunctional hydrogenolysis mechanism, in addition to the classical bifunctional route. Characterization studies showed that both catalysts had comparable metal and acid site distributions. These observations would indicate that the different catalyst performance is due to the different nature of platinum and palladium as hydrogenation/dehydrogenation function.
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- Tamburro, Davide, et al.
(författare)
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Mass Spectrometry-based characterization of the vitreous phosphoproteome
- 2010
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Ingår i: Proteomics Clinical Applications. - : Wiley. - 1862-8346. ; 4:10-11, s. 839-846
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The vitreous gel is a highly hydrated extracellular matrix containing many proteins. These proteins are likely accumulated in the vitreous by local secretion, filtration from the blood, or diffusion from the surrounding tissues and vasculature, and may be altered in disease state. In the last several years, several reports of large-scale profiling of vitreous proteins have been published; however, there is little information on the characterization of the phosphoproteome of vitreous. Here, we sought to identify phosphopeptides and their phosphorylation sites from vitreous. Experimental design: We used titanium dioxide (TiO2) to enrich phosphopeptides from vitreous and identified them by LC-MS/MS. Results: We identified 85 unique phosphopeptides and the phosphorylation sites from 44 proteins. Conclusions and clinical relevance: We present a method for characterization of phosphoproteome from vitreous samples using current MS technologies and yielded an initial assessment of the phosphoprotein/peptide content of human vitreous, thus providing important biological information toward further understanding of the post-translational modifications of vitreous proteins and their functional significance in disease.
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