Nanoparticles of tungsten as low-cost monometallic catalyst for selective hydrogenation of 3-hexyne

Low-cost tungsten monometallic catalysts containing variable amounts of metal (4.5, 7.1 and 8.5%W) were prepared by impregnating alumina with ammonium metatungstate as an inexpensive precursor. The catalysts were characterized using ICP, XPS, XRD, TPR and hydrogen chemisorption. These techniques revealed mainly WO3-Al2O3 (W6+) species on the surface. The effects of the content of W nanoparticles and reaction temperature on activity and selectivity for the partial hydrogenation of 3-hexyne, a non-terminal alkyne, were assessed under moderate conditions of temperature and pressure. The monometallic catalysts prepared were found to be active and stereoselective for the production of (Z )-3-hexene, had the following order: 7.1WN/A > 8.5 WN/A ≥ 4.5 WN/A. Additionally, the performance of the synthesized xWN/A catalysts exhibited high sensitivity to temperature variation. In all cases, the maximum 3-hexyne total conversion and selectivity was achieved at 323 K. The performance of the catalysts was considered to be a consequence of two phenomena: a) the electronic effects, related to the high charge of W (+6), causing an intensive dipole moment in the hydrogen molecule (van der Waals forces) and leading to heterolytic bond rupture; the H+ and H- species generated approach a 3-hexyne adsorbate molecule and cause heterolytic rupture of the C≡C bond into C- = C+; and b) steric effects related to the high concentration of WO3 on 8.5WN/A that block the Al2O3 support. Catalyst deactivation was detected, starting at about 50 min of reaction time. Electrodeficient W6+ species are responsible for the formation of green oil at the surface level, blocking pores and active sites of the catalyst, particularly at low reaction temperatures (293 and 303 K). The resulting best catalyst, 7.1WN/A, has low fabrication cost and high selectivity for (Z )-3-hexene (94%) at 323 K. This selectivity is comparable to that of the classical and more expensive industrial Lindlar catalyst (5 wt% Pd). The alumina supported tungsten catalysts are low-cost potential replacements for the Lindlar industrial catalyst. These catalysts could also be used for preparing bimetallic W-Pd catalysts for selective hydrogenation of terminal and non-terminal alkynes.

Ancient Rome, Italy (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Pianta delle vestigia di Roma, secondo le osservazioni di Antonio de Romanis, ach. e socio dell' accad. di archeol. e di Antonio Nibby profess. di archeologia nell Vniv. di Roma e Socio della Stessa Accademia dallo stesso corretta ed amliata seconodo le vltime scoperte. data in lvce da Venanzio Monaldini Libraio L Anno MDCCCXXVI; Gio Acquaroni dis. e inc. It was published by presso Veanzio Monaldini ... con approvazione e privilegio Pontificio in 1826. Scale [ca. 1:8,769]. Covers area including portion of the modern city of Rome and Vatican City. The image inside the map neatline is georeferenced to the surface of the earth and fit to the "European Datum 1950 UTM Zone 33N" coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features of Ancient Rome such as roads, drainage, selected buildings, city walls, gates, and fortifications, arches, and sepulchres. Relief is shown by hachures. Includes index, notes, and insets showing floor plans of selected historical sites.This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.

Appunti sul Belgio musicale /

At head of title: All'onorevole Consiglio Direttivo della Reale Accademia di Santa Cecilia in Roma.

Dell' origine e de' progressi dell' Instituto delle scienze di Bologna : e di tutte le accademie ad esso unite, con la descrizione delle più notabili cose, che ad uso del mondo letterario nello stesso Instituto si conservano : operetta in grazia degli eruditi /

Signatures: A-G⁸ H⁴.

La bibliografia Virgiliana : (1912-1913) /

Excerpt from "Atti e memorie", Nuova serie, v. 7, 1914.

Indice generale dei lavori pubblicati dal MDCCXXXVII al MDCCCCIII.

Mode of access: Internet.

Commemorazione di Rodolfo Renier e di Francesco Novati.

At head of title: Reale Accademia delle scienze di Torino (Anno 1919-1920)

Notizie degli scavi di antichità.

Latest issue consulted: Ser. 9, v. 11/12 (2000/2001)

L'opera politico-militare di Andrea Provana di Leynì nello Stato sabaudo dal 1553 al 1559 : memoria del dott. Arturo Segre.

Bibliographical foot-notes.

The art of the Venice Academy, containing a brief history of the building and of its collection of paintings, as well as descriptions and criticisms of many of the principal pictures and their artists,

Bibliography: p. 347-351.

Catalogo delle R.R. Gallerie di Venezia.

Includes index.

Anatomy improv'd and illustrated with regard to the uses thereof in designing : not only laid down from an examen of the bones and muscles of the human body, but also demonstrated and exemplified from the most celebrated antique statues in Rome : exhibited in a great number of copper plates, with all the figures in various views : intended originally for ye use of the Royal French Academy of Painting and Sculpture /

Re-engraved by Michael van der Gucht and others after the original edition published at Rome in 1691.

Bullettino senese di storia patria.

Inventario generale del R. Archivio di stato in Siena. Parte seconda. Consiglio generale. 1915. 128 p. (Issued and bound with v. 21).

Rendiconti.

Series 5-6, 8- issued as Atti della Accademia nazionale dei Lincei; series 7, as Atti della Reale Accademia d'Italia.

Il Libro dei funerali degli antichi egiziani.

The three hieroglyphic texts with transliteration and Italian translation.