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Solid-state species deposited on L'vov platforms during ETAAS of vanadium solutions were studied by X-ray photoelectron spectroscopy. The presence of vanadium carbide (VC) during ashing and atomization stages was confirmed.

The catalytic performance during the 1-butyne hydrogenation using two reduced Al2O3-supported Pd-based catalysts was carried out in a total recirculation system with an external fixed-bed reactor. The lab-prepared egg-shell NiPd/CeO2-Al2O3 catalyst (NiPdCe) with Pd loading = 0.5 wt%, Ni/Pd atomic ratio = 1 and CeO2 loading = 3 wt% was synthesized and characterized, and it was compared with an egg-shell Al2O3-supported Pd based commercial catalyst (PdCC). The reduced catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The textural characteristics and ammonia temperature-programmed desorption profiles of the fresh (unreduced) catalysts were also obtained. Both catalysts show high 1-butyne conversion and selectivity to 1-butene, but the catalysts also present important differences between hydroisomerizing and hydrogenating capabilities. NiPdCe catalyst shows higher capability for hydroisomerization reactions, while the PdCC catalyst exhibits higher hydrogenating capability. The observed catalytic performances can be interesting for some industrial processes and can provide a guideline for the development of a Pd-based catalyst with specific catalytic properties.

Ti modified MCM-41-supported NiMo and CoMo catalysts and their respective Ti free reference catalysts were prepared, characterized, and tested for the hydrodesulfurization reactions. The samples were synthesized by well-known procedures, such as liquid crystal templating and successive impregnation method for the supports and catalysts, respectively. Ti precursor was directly incorporated into the micellar solution before adding the silica precursor at different molar Si/Ti ratios (x = 75 and 50). Fourier transform infrared spectroscopy, solid-state 29Si-nuclear magnetic resonance, small- and wide-angle X-ray diffraction, and nitrogen physisorption were used as characterization techniques. Four sulfided catalysts were also characterized by high-resolution transmission electron microscopy. The catalysts showed important increases in the reaction rates during both thiophene and dibenzothiophene hydrodesulfurization when the support was structurally modified with Ti-atoms. The samples supported on Ti-MCM-41(75) presented a higher activity than those supported on Ti-MCM-41(50), and they were superior to their respective Si-MCM-41-supported NiMoS and CoMoS catalysts, even NiMoTiM75 and CoMoTiM75 catalysts presented better performance compared to the conventional NiMo/Al2O3 and CoMo/Al2O3 catalysts in the DBT hydrodesulfurization. Ti incorporation also enhanced the selectivities to the hydrogenated products, which could be beneficial to destabilize refractory S-containing molecules.

A mesoporous titania material with a single X-ray diffraction signal at small-angle and anatase TiO2 walls was prepared by a sol–gel method using hexadecylamine as a templating agent and titanium isopropoxide as a titanium precursor. The mesoporous solid was used to prepare a novel layered titanium phosphate by Soxhlet extraction reflux with phosphoric acid. The obtained α-TiP material showed a typical wide-angle X-ray diffraction pattern with a monoclinic structure, N2 adsorption–desorption isotherms Type II, and large crystals of rectangular lamellae, confirming its layered nature by transmission electron microscopy. The elimination by adsorption of Hg2+ ions from aqueous samples was studied using Langmuir, Freundlich and Temkin models, calculating its different parameters. The adsorption of Hg2+ ions could be performed via active P-OH groups (observed by Fourier Transform Infrared results) in the lamellar structure showing excellent properties that make the layered material possible excellent adsorbent to remove heavy metals ions contaminants from potable water.

Changes in the oxidation state and chemical environment of vanadium in poisoned and regenerated hydrotreatment (HDT) catalyst were followed by electron paramagnetic resonance (EPR). Oxovanadyltetraphenil porphyrin was used as model poison molecule on synthesized CoMo/Al2O3 HDT-UCV-1 catalyst. Unconventional methodologies of carbiding and nitriding were applied to the deactivated catalyst aiming at recovering its catalytic properties. The results showed that the vanadium incorporation method affected the metallic species on the catalyst surface, particularly the V-support interaction. This work represents an important contribution about the understanding of new phases formed in the spent catalysts after reactivation by means of nitriding and carbiding processes, which are expected to improve the catalytic HDT response.

Novel controlled hydrophilic nonporous carbon-based sorbents from petroleum coke were obtained by using a hydrothermal oxidation treatment of shot coke with different H2O2 concentrations. The ability of resulting carbon materials for the selective adsorption of cationic dyes from aqueous solution directed by surface recognition is highlighted for the first time. This approach provides an eco-friendly, low-cost alternative for the preparation of sorbents with unprecedented properties to achieve remarkable selective adsorption independent of the presence of intrinsic porosity. A further advantage of these sorbents is their efficient regeneration capability and reusability without appreciable changes in their adsorption capacity. Results reveal that the dye adsorption capacity is significantly enhanced on multivalent hydrophilic surfaces in comparison to the pristine surface. In addition, a deep insight is offered into the explanation of selective adsorption processes on hydrophilic coke in the function of s...

Alumina-supported Ni-promoted W oxides, carbides and nitrides were presulfided and employed for reducing pollutants and increasing the quality of an extra-heavy crude oil during catalytic upgrading reactions. These materials were prepared by temperature programmed reaction using reactive gases and varying the (Ni/(Ni + W)) atomic ratio from 0.00 to 1.00. Catalysts were characterized by XRD, SEM, HRTEM and N2 physisorption. In order to study the effect of the atomic ratio in the conversion of the model molecule thiophene, room pressure HDS tests were used. The catalysts with best performances during thiophene HDS were tested in the upgrading of a Venezuelan extra-heavy crude oil characterized by having high asphaltenes, S and N contents, affecting competitiveness in the global market. These results were compared with a commercial NiMo catalyst. API gravity of crude oil, CHNS elemental analysis, 13C- and 1H NMR of crude oil and asphaltenic fraction, in addition to flocculation threshold of asphaltenes, were studied in order to verify variations in physicochemical properties of oil due to catalytic upgrading and to seek evidence of pollutants reduction and improvement of quality during this process. NiW catalysts with atomic ratio (Ni/(Ni + W) = 0.50 showed remarkable performance during thiophene HDS and heavy oil hydrotreatment, improving API gravity and reducing S content, modifying chemical nature of crude oil and asphaltenes, as it was revealed by results of elemental analysis, H/C ratio, flocculation threshold, Caro/Cali and Haro/Hali ratios. However, no significant variations were found in N contents of crudes and asphaltenes revealing poor HDN performance, apparently due to Na traces from the W precursor remaining in the final NiW catalysts.

Aromatic hydrocarbons constitute a significant fraction of fossil-derived transportation fuels. They are also used as additives to suppress autoignition and to increase fuel energy density. However, they produce harmful polycyclic aromatic hydrocarbons (PAHs) and soot during combustion. In this work, the effects of methyl group(s) and the flow rate of aromatic fuels (benzene, toluene, and m-xylene) on the concentration of volatile PAHs bound to soot formed in diffusion flames are studied. Soxhlet extraction using dichloromethane as the solvent is used to extract PAHs from soot particles collected from the flames of aromatic fuels. The extracts are analyzed using a gas chromatograph coupled to a mass spectrometer. Among the sixteen priority PAHs, fifteen of them are detected on soot particles along with benzo(e)pyrene and other organic compounds such as oxygenated compounds and mono-aromatic hydrocarbons. The PAHs containing two to three aromatic rings were found to be in higher concentrations than those with four or more rings. The total amount of PAHs collected at different fuel flow rates from the three aromatic fuels increased marginally in the following order: benzene

Se hace una revisión sobre el estado del arte de la catálisis involucrada en la reacción de hidrogenación selectiva de 1,3-butadieno en cortes ricos en 1-buteno con catalizadores basados en Pd/Al2O3. Se presentan algunos aspectos relevantes de esta tecnología, como: conceptos básicos de hidrogenación, hidrogenación parcial e hidrogenación selectiva, su importancia en la industria petrolera venezolana, las condiciones termodinámicas de reacción, la evolución de los catalizadores hasta la actualidad, y las tendencias en este campo de investigación. De igual manera, se resumen los avances en los mecanismos de reacción y las características estructurales y funcionales de los nuevos catalizadores para el mejoramiento y optimización de este proceso., A review is presented about the state of the art of the catalysis involved in selective hydrogenation reaction of 1,3-butadiene in 1-butene-rich cuts with Pd/Al2O3-based catalysts. Some relevant aspects of this technology are presented, such as: basic concepts of hydrogenation, partial hydrogenation and selective hydrogenation, its importance for the Venezuelan oil industry, thermodynamics conditions of this reaction, evolution of catalysts up to present, and trends in this field of research. Similarly, it is summarized the advances on reaction mechanisms and structural and functional characteristics of new catalysts, for the improvement and optimization of this process., {"references":["1. P.N. Rylander. \"Hydrogenation methods\", Academic Press Inc., Florida, 1985. 2. R.L. Augustine. \"Heterogeneous catalysis in organic synthesis\", Marcel Dekker, New York, 1995. 3. M. Consonni, R. Touroude, D.Yu. Murzin. Chem. Eng. Technol. 21 (1998) 605. 4. J.C. Guardado, M.E. Osuna-Sánchez, G.A. García, A. Cabrera-Hernández, \"Química orgánica: nomenclatura, reacciones y aplicaciones\", Dirección General de Escuela Preparatoria, Sinaloa, 2006. 5. I. Horiuti, M. Polanyi. Trans. Faraday Soc. 30 (1934) 1164. 6. A. Farkas, L. Farkas. J. Am. Chem. Soc. 60 (1938) 22. 7. G.H. Twigg, E.K. Rideal. Proc. Roy. Soc. A 171 (1939) 55. 8. G.H. Twigg. Disc. Faraday Soc. 8 (1950) 152. 9. M. Calvin. J. Am. Chem. Soc. 61 (1939) 2230. 10. J.A. Osborn, F.H. Jardine, J.F. Young, G. Wilkinson. J. Chem. Soc. A (1966) 1711. 11.\tG. Wilkinson. \"The long search for stable transition metal alkyls\", recuperado de http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1973/wilkinson-lecture.pdf el 17/08/2012. 12. P. Sabatier, J.B. Senderens. Comptes Rendus 128 (1899) 1173. 13. P. Sabatier, J.B. Senderens. Ann. Chim. Phys. 4 (1905) 319. 14. P. Sabatier, J.B. Senderens. Ann. Chim. Phys. 4 (1905) 433. 15.\tP. Sabatier. \"The method of direct hydrogenation by catalysis\", recuperado de http://nobelprize.org/nobel_prizes/chemistry/laureates/1912/sabatier-lecture.html el 31/10/2009. 16. E.F. Meyer, R.L. Burwell, Jr. J. Am. Chem. Soc. 85 (1963) 2881. 17. G.C. Bond, J.J. Phillipson, P.B. Wells, J.M. Winterbottom. Trans. Faraday Soc. 60 (1964) 1847. 18. G.C. Bond, P.B. Wells. Adv. Catal. 15 (1965) 91. 19. G.C. Bond, G. Webb, P.B. Wells, J.M. Winterbottom. J. Chem. Soc. (1965) 3218. 20. P.B. Wells, A.J. Bates. J. Chem. Soc. A (1968) 3064. 21. J.J. Phillipson, P.B. Wells, G.R. Wilson. J. Chem. Soc. A (1969) 1351. 22. A.J. Bates, Z.K. Leszczyński, J.J. Phillipson, P.B. Wells, G.R. Wilson. J. Chem. Soc. A (1970) 2435. 23.\tB. Didillon, J. Cosyns, C. Cameron, D. Uzio, P. Sarrazin, J.B. Boitiaux. Stud. Surf. Sci. Catal. 111 (1997) 447. 24. M.L Derrien. Stud. Surf. Sci. Catal. 27 (1986) 613. 25. S. Hub, L. Hilaire, R. Touroude. Appl. Catal. 36 (1988) 307. 26. J.G. Speight. \"The chemistry and technology of petroleum\", Marcel Dekker Inc., New York, 1999. 27.\tJ. Mengual-Cuquerellac. \"Craqueo térmico y catalítico, con y sin vapor de agua, de alcanos sobre zeolitas: cinética, desactivación y estabilización del catalizador\", Tesis Doctoral en Ingeniería Química, Universitat de València, España, 2010. 28. T.T.P. Cheung, M.M. Johnson. US Patent 5,866,735 (1999). 29. F.O. Rice, K.F. Herzfeld. J. Am. Chem. Soc. 56 (1934) 284. 30. S.W. Benson, W.B. DeMore. Ann. Rev. Phys. Chem. 16 (1965) 397. 31. M.A. Muñecas-Vidal. Ing. Quim. 413 (2004) 77. 32. R.A. Dawe. \"Modern petroleum technology\", John Wiley & Sons, New York, 2000. 33. F.C. Whitmore. Ind. Eng. Chem. 26 (1934) 94. 34. R.C. Hansford. Ind. Eng. Chem. 39 (1947) 839. 35. C.L. Thomas. Ind. Eng. Chem. 41 (1949) 2564. 36. K.A. Cumming, B.W. Wojciechowski. Catal. Rev.-Sci. Eng. 38 (1996) 101. 37. A. Corma, A.V. Orchillés. Microp. Mesop. Mater. 35-36 (2000) 21. 38. J. Planelles, J. Sánchez-Marín, F. Tomás, A. Corma. J. Mol. Catal. 32 (1985) 365. 39. J. Abbot, J.D. Head. J. Catal. 125 (1990) 187. 40. A. Corma, J. Planelles, F. Tomás. J. Catal. 94 (1985) 445. 41. C.J.A. Mota, P.M. Esteves, A. Ramirez-Solis, R. Hernández-Lamoneda. J. Am. Chem. Soc. 119 (1997) 5193. 42. S.E Tung, E.J. McIninch. J. Catal. 10 (1968) 166. 43. A. Borodzinski, A. Corma, B.W. Wojciechowski. Can. J. Chem. Eng. 58 (1980) 219. 44.\tA. Brait, A. Koopmans, H. Weinstabe, A. Ecker, K. Seshan, J.A. Lercher. Ind. Eng. Chem. Res. 37 (1998) 873. 45. B.S. Greensfelder, H.H. Voge, G.M. Good. Ind. Eng. Chem. 41 (1949) 2573. 46. W.F. Pansing. J. Phys. Chem. 69 (1965) 392. 47. O.A. Reutov, T.N. Shatkina. Tetrahedron 18 (1962) 237. 48. D.M. Brouwer, H. Hogeveen. Prog. Phys. Org. Chem. 9 (1972) 179. 49. P.A. Jacobs, J.A. Martens. Stud. Surf. Sci. Catal. 58 (1991) 445. 50. P.B. Venuto, L.A. Hamilton, P.S. Landis. J. Catal. 5 (1966) 484. 51. A.P. Bolton. J. Catal. 22 (1971) 9. 52. B.W. Wojciechowski, A. Corma. \"Catalytic cracking catalyst, chemistry and kinetics\", Marcel Dekker Inc., New York, 1986. 53. A. Corma, J.B. Montón, A.V. Orchillés. Appl. Catal. 23 (1986) 255. 54. P.V. Shertukde, G. Marcelin, G.A. Sill, W.K. Hall. J. Catal. 36 (1992) 446. 55.\tPEQUIVEN, \"Petroquímica de Venezuela, S.A.\" Recuperado el 20/08/2012 de http://www.pequiven.com/pqv/index.php 56. C. Clementi, G. Oriani, F. Ancillotti, G. Pecci. Hydrocarbon Processing 59 (1979) 109. 57. E.E. Barberii. \"El pozo ilustrado\", Fondo Editorial del Centro Internacional de Educación y Desarrollo, Caracas, 1998. 58.\tG.C. Bond. \"Metal-catalysed reactions of hydrocarbons\", Springer Science and Business Media Inc., New York, 2005. 59. T. Ouchaib, J. Massardier, A. Renouprez. J. Catal. 119 (1989) 517. 60. J.P. Boitiaux, J. Cosyns, E. Robert. Appl. Catal. 35 (1987) 193. 61. M.G. Riley. \"The selective hydrogenation of 1,3-butadiene in the presence of n-butenes over supported palladium catalysts\", PhD Thesis, Rice University, United Stated, 1989. 62. J.A. Alves, S.P. Bressa, O.M. Martínez, G.F. Barreto. Chem. Eng. J. 99 (2004) 45. 63. M.L. Derrien, C. Bronner, J. Cosyns, G. Leger. Hydrocarbon Processing 58 (1979) 175. 64. P.B. Wells. \"Selectivity in metal-catalysed hydrogenation\" in Surface Chemistry and Catalysis: A.F. Carley, P.R. Davis, G.J. Hutchings, M.S. Spencer (Editores), Kluwer Academic/Plenum Publishers, New York, 2002. 65. R.B. Moyes, P.B. Wells, J. Grant, N.Y. Salman. Appl. Catal. A: Gen. 229 (2002) 251. 66. Á. Molnár, A. Sárkány, M. Varga. J. Mol. Catal. A : Chem. 173 (2001) 185. 67. S.P. Bressa, J.A. Alves, N.J. Mariani, O.M. Martínez, G.F. Barreto. Chem. Eng. J. 92 (2003) 41. 68. M. George, R.B. Moyes, D. Ramarac, P.B. Wells. J. Catal. 52 (1978) 486. 69. J. Anderson, S.H. McAllister, E.L. Derr, W.H. Peterson. Ind. Eng. Chem. 40 (1948) 2295. 70. E.J. Hoffman, E.W. Lewis, E.F. Wadley. Pet. Ref. 36 (1957) 179. 71. J.P. Boitiaux, J. Cosyns, M. Derrien, G. Léger. Hydrocarbon Processing 64 (1985) 51. 72. G.C. Bond. \"Catalysis by metals\", Academic Press, Inc., New York, 1962. 73. M.L. Derrien, J.W. Andrews, P. Bonnifay, J. Leonard. Chem. Eng. Prog. 70 (1974) 74. 74. A.E. Eleazar, R.N. Heck, M.P. Witt. Hydrocarbon Processing 58 (1979) 112. 75. B.K. Furlong, J.W. Hightower, T.Y.L. Chan, A. Sárkány, L. Guczi. Appl. Catal. A: Gen. 117 (1994) 41. 76. A. Sárkány, Z. Zsoldos, Gy. Stefler, J.W. Hightower, L. Guczi. J. Catal. 157 (1995) 179. 77. R. Ohnishi, H. Suzuki, M. Ichikawa. Catal. Lett. 33 (1995) 341. 78. H. Miura. Catal. Today 28 (1996) 215. 79. E.M. Crabb, R. Marshall. Appl. Catal. A : Gen. 217 (2001) 41. 80. H. Miura, M. Terasaka, K. Oki, T. Matsuda. Stud. Surf. Sci. Catal. 75 (1993) 2379. 81. A. Sárkány. Appl. Catal. A : Gen. 165 (1997) 87. 82. A. Sárkány. Stud. Surf. Sci. Catal. 111 (1997) 111. 83.\tT. Redjala, H. Remita, G. Apostolescu, M. Mostafavi, C. Thomazeau, D. Uzio. Oil Gas Sci. Techn. 61 (2006) 789. 84. A. Hugon, L. Delannoy, J.M. Krafft, C. Louis. J. Phys. Chem. C 114 (2010) 10823. 85. S.H. Choi, J.S. Lee. J. Catal. 193 (2000) 176. 86. S. Verdier, B. Didillon, S. Morin, J.C. Jumas, J. Oliver-Fourcade, D. Uzio. J. Catal. 218 (2003) 280. 87. S. Verdier, B. Didillon, S. Morin, D. Uzio. J. Catal., 218 (2003) 288. 88.\tK. Pattamakomsan, E. Ehret, F. Morfin, P. Gélin, Y. Jugnet, S. Prakash, J.C. Bertolini, J. Panpranot, F.J.C.S. Aires. Catal. Today 164 (2011) 28. 89. J. Goetz, M.A. Volpe, C.E. Gigola, R. Touroude. J. Catal. 199 (2001) 338. 90. K. Pattamakomsan, K. Suriye, S. Dokjampa, N. Mongkolsiri, P. Praserthdam, J. Panpranot. Catal. Commun. 11 (2010) 311. 91. J. Goetz, M.A. Volpe, A.M. Sica, C.E. Gigola, R. Touroude. J. Catal. 167 (1997) 314. 92. J. Goetz, M.A. Volpe, R. Touroude. J. Catal. 164 (1996) 369. 93. R. Galiasso-Tailleur, J. Hernandez, A. Rojas. Fuel 87 (2008) 3694. 94. R. Galiasso-Tailleur, J. Ravigli-Nascar. App. Catal. A: Gen. 439-440 (2012) 125."]}

Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Cu/SAPO-11, NO–Cu/SAPO-11, NH3–Cu/SAPO-11 and NO + NH3–Cu/SAPO-11 to investigate the reaction pathway of the selective catalytic reduction of nitrogen oxides by ammonia in the presence of Cu/SAPO-11. NH2NO is formed, and then is decomposed into N2 and H2O over Cu/SAPO-11 for the catalytic reduction of NO in two steps. The adsorption energy ΔEads of NO, NH3 on Cu/SAPO-11 and the change of energy of the reduction reaction are presented. The energy profile of the formation of NH2NO–Cu/SAPO-H key intermediate is shown. Some relevant charges and bond indexes were calculated. On adsorbing NH3 or NO on Cu/SAPO-11 there is charge transfer to the aggregates. Vibrational frequencies of adsorbed NH3, NO and of NH2NO–Cu/SAPO-11cluster are reported. The importance of adsorbing NH3 previously to the reduction of NO is emphasized.

Adsorptions of molybdenum species and interactions on a model pyrolytic graphite platform (PGP) sites were calculated employing quantum methods (density functional theory (DFT) and parametric method number 6 (PM6)). The aim of this work is to propose, at the molecular level, the structure of different chemisorbed species on the PGP surface used in the electrothermal atomic absorption spectroscopy (ETAAS) process for a Mo analyte. The carbon surface was modeled by a seven-ring polycyclic aromatic system (coronene). Molybdenum species (Mo, Mo 2 , MoO, MoO 2, MoO 3 , and MoO 4 ) adsorbed on a coronene surface were studied on different adsorption sites. Calculations of these species showed that chemisorption strengths are stronger on dehydrogenated and decarbonized edge sites than on sites located in the flat central region of the model graphite. It was confirmed that Mo-oxygenated species interactions are very strong at the edge sites and therefore the reduction of these species must occur before the atomization (evaporation of Mo species) takes place, in agreement with experimental results. Comparisons between experimental XPS spectra for ETAAS process (drying, ashing, and atomization) and calculated adsorption energies of Mo species allow an interpretation of which species are present on the PGP at each stage. The presence of very strong bonded molybdenum carbide species on decarbonized sites may explain the memory effects. Experimentally observed migration of Mo oxide species to the edges of the PGP is also corroborated by their small chemisorption energies on central sites of the PGP model.

The effect of Nb as a support modifier on the NiMo6/Al2O3–Nb2O5(x) (x = 0, 1, 4, and 8 wt% Nb) catalysts was studied. The supports were prepared by one-pot coprecipitation from soluble precursors. The XRF analysis of the catalysts showed that the contents of Mo and Ni increased slightly with the presence of Nb. Micropore area and pore volume augmented importantly with Nb content, resulting in pore diameters between 5.3 and 9.3 nm. XPS analysis showed that the presence of Nb decreases the active metal–support interaction, improving the Mo and Ni sulfidation degree. The Raman spectra of sulfided catalysts suggested an increase in the number of layers of MoS2 in the presence of Nb. Generally, the thiophene HDS activity at normal pressure of sulfided NiMo6/Al2O3–Nb2O5(8) was greater than that of the sulfided catalysts with x = 0, 1, and 4 wt% Nb, which can be attributed to the Nb promotion that would have an effect on the type of active site (Bronsted or Lewis acidic sites), since the number of sites by CO chemisorption for sulfided NiMo6/Al2O3–Nb2O5(x) did not show correlation with the catalytic activity. The high-pressure HDS activity of dibenzothiophene was also greater in the presence of Nb, and the hydrogenation route was preferred for the Nb-promoted solid, while the unpromoted one showed a larger yield of direct desulfurization products.

Aromatic hydrocarbons in liquid transportation fuels help in suppressing auto-ignition and knocking tendency in engines, but are toxic and can generate polycyclic aromatic hydrocarbons (PAHs) and soot during combustion that are harmful for human health and the environment. Benzene, toluene, and xylenes are present in noticeable quantities in liquid fuels. This paper reports the sooting propensity of benzene and m-xylene, and the role of substituted aliphatic chains on soot emissions at different fuel flow rates along with their effects on soot characteristics. Soot particles collected from the aromatic diffusion flames at different fuel flow rates are characterized using high resolution transmission electron microscopy and X-ray diffraction to examine their nanostructural changes, and using, electron energy loss spectroscopy, Raman spectroscopy, and elemental analysis to determine their chemical properties. With increasing fuel flow rates in benzene and m-xylene flames, the size of the primary particles in soot increased, but that of PAHs reduced. The chemical changes introduced by increasing fuel flow rates in both the diffusion flames were the reduction in the concentrations of oxygen and hydrogen content. Though aliphatics are less sooting than aromatics, the presence of methyl groups on the aromatic ring in m-xylene not only increased the soot production rate, but also led to soot particles with less hydrogen content than those from benzene flames. Soot modeling studies are conducted to study the sooting behaviors of benzene an m-xylene fuels. The results from benzene and m-xylene flames suggest that increasing the rate of fuel consumption (which happens while increasing engine load) can significantly affect the physicochemical properties of soot from the same fuel.

The removal of traces of highly unsaturated compounds, such as 1,3-butadiene, from olefin feedstocks via selective hydrogenation is of particular importance because the oligomerization of these impurities produces deactivation and an increased pressure drop across the catalytic beds used in the polymerization processes. The present work focuses on the selective hydrogenation of 1,3-butadiene in the presence of 1-butene using (xCeO2-)Al2O3-supported NiPd catalysts (x = 0, 1, 2, and 3 wt% CeO2) in both liquid and gas conditions. The samples were characterized by XRD, N2 physisorption, Zeta potential, H2-TPR, NH3-TPD, HRTEM and STEM-HAADF. Modifying the catalysts with CeO2 resulted in an increase of 1,3-butadiene conversion, an enhancement of 1-butene selectivity and a decrease of butane production under liquid phase conditions. In contrast, in the gas phase both the Ce-modified and unmodified catalysts behaved similarly: while the fresh catalysts showed similar reactivity to that found in liquid phase conditions, the reacted and thermally pretreated catalysts showed increased reactivity, leading to full hydrogenation up to butane. The improvements observed under liquid phase conditions may be related to modification of the acid strength with increasing CeO2 loading, which would increase the adsorption of 1,3-butadiene and diminish the further hydrogenation of 1-butene. Optimal activity and selectivity were observed for the catalyst with an Ni/Pd atomic ratio of 1, and loadings of 0.5 wt% Pd and 3.0 wt% CeO2.

En este trabajo se estudió el efecto de la carburación con CH4(20%Vol.)/H2 de heteropolioxometalatos tipos Anderson (NH4)4[NiMo6-xWxO24H6]•5H2O con relaciones atómicas 1:6:0 y 1:3:3 sobre la hidrodesulfuración de tiofeno. Los sólidos carburados se caracterizaron por DRX, propiedades texturales (ABET, Vp y Dp), FT-IR y análisis elemental (CHNO-S). DRX mostró señales de β-Mo2C, NiC, β-W2C y β-WC. Los materiales carburados presentaron isotermas de adsorción tipo IV y lazos de histéresis H2 y H3, con áreas específicas entre 3 y 6 m2/g y tamaño de poros entre 9 y 14 nm. El análisis FT-IR de los carburos solo presentaron las señales de Mo-O2 y O-H. El catalizador trimetálico fue más activo en hidrodesulfuración (HDS) de tiofeno que el bimetálico: NiMo3W3-C (30%) > NiMo6-C (23%), mientras la selectividad estuvo dirigida hacia la formación de 1,3 butadieno para NiMo3W3-C y, 1-buteno y cis-buteno para NiMo6-C. In this work-was studied the effect of the carburization with CH4(20%Vol.)/H2 of (NH4)4[NiMo6-xWxO-24H6]•5H2O Anderson type polyoxometalates with (AR) atomic ratio = 1:6:0 and 1:3:3 on the thiophene hydrodesulfurization reaction. The carburized solids were characterized by XRD, textural properties (ABET, Vp y Dp), FT-IR and (CHNO-S) elemental analysis. XRD showed signals of β-Mo2C, NiC, β-W2C and β-WC. Carburized materials presented type IV isotherms and hysteresis loop H2 and H3, the specific surface area was between 3 and 6 m2/g, and pore size between 9 and 14 nm. The FT-IR analysis of carbides showed signals of Mo-O2 and O-H. The catalytic activity of trimetallic catalyst was higher than that of bimetallic catalyst: NiMo3W3-C (30%) > NiMo6-C (23%), while the selectivity was directed toward the formation of 1,3 butadiene by NiMo3W3-C and 1-butene and cis-butene by NiMo6-C.

The γ-Al 2 O 3 -supported Anderson-type complexes (NH 4 ) 4 [NiMo 6 − x W x O 24 H 6 ]·5H 2 O (x = 0, 3 or 6) were carburized with CH 4 /H 2 (1:4) mixture (denoted by NiMo 6 − x W x -C/Al). These solid compounds have been tested in a continuous flow, fixed bed reactor for thiophene hydrodesulfurization and polychlorinated biphenyls hydrodechlorination, and in (semi-) batch reactor for dibenzothiophene selective oxidation. The specific surface area and pore volume of NiMo 6 -C/Al were greater than those of NiW 6 -C/Al and NiMo 3 W 3 -C/Al. XRD results evidenced a bulk structure typical of Mo 2 C, W 2 C, WC and NiC. FT-IR verified the absence of bands corresponding to metal oxides. Generally, the catalytic activity toward a given reaction product of NiMo 6 -C/Al was greater than those of NiW 6 -C/Al and NiMo 3 W 3 -C/Al due either to its better textural properties or to a more complete transformation of the metal phases into active ones.

Different aluminium structured substrates (monoliths of 350 and 1100 cpsi; foams of 10, 20 and 40 ppi) have been loaded with NiPd/(CeO 2 -Al 2 O 3 ) catalyst by washcoating. To improve the adherence between catalyst particles and metallic surface, aluminium substrates were previously anodized to produce a rough (cracked) surface. Catalytic layers of different thickness have been deposited onto aluminium substrates. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the selective hydrogenation of 1,3-butadiene in presence of 1-butene under liquid-phase conditions. The effects of some design parameters over the catalytic performance were studied: catalyst loading (125, 250 or 500 mg), geometry of the structured substrate (monoliths or foams), and porosity (cpsi or ppi). The catalytic results show that foams present better activity than the monoliths. This can be related to better mass and heat transfer in the case of foams. In addition, the catalytic coating thickness influence directly the reaction selectivity; thicker layers produce undesired products (BA and isomers) due to diffusion limitations. However, it seems that the mass transfer of reactants to the surface of the catalyst layer plays a major role than the diffusion of reactants inside the catalyst layer.

X-ray photoelectron spectroscopy (XPS) was employed as the analytical tool for the identification of the solid state species formed during the atomization of molybdenum on a pyrolytic graphite surface used for electrothermal atomization in atomic absorption spectroscopy (ETAAS). As XPS is capable of probing the amounts of materials employed in actual ETAAS measurements, it was anticipated that it would allow obtaining more realistic results than those reported in previous works by means of techniques such as X-ray diffraction, which requires thousand-fold amounts of the analyte. The results obtained by XPS showed a distribution pattern of the oxidation states of Mo on the graphite surface as a function of the temperatures reached at each stage of the ETAAS procedure, which was correlated with the possible species formed during the drying, ashing and atomization steps. In light of the present results, a previously proposed atomization mechanism for Mo was revisited, which allowed to disprove the alleged presence of phases such as Mo 4 O 11 at the ashing stage and of metallic Mo as a stable, intermediate phase during the Mo 2 C low temperature carbide formation at 1200–1900 °C. It is concluded that the XPS technique allows gaining an insight into the atomization mechanism of the analyte.

Aromatic hydrocarbons are commonly found in fossil-derived transportation fuels, and their combustion in engines produce most of the observed soot particles. Toluene is an important component of gasoline (about 6 wt%), diesel (1–2 wt%), and jet fuels (1–2 wt%), and forms a part of their surrogates. This paper reports the nanostructures and chemical constituents of soot, formed in toluene diffusion flames at different fuel flow rates. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) are employed to study the physical properties of soot, while Fourier transform infrared spectroscopy (FTIR), electron energy loss spectroscopy (EELS), and elemental analysis are used to investigate its chemical properties. With increasing fuel flow rate, HRTEM and XRD analyses showed that the lateral size of aromatic layers in soot reduced, while the FTIR analysis revealed that the concentration of aliphatic and oxygenated groups decreased, and that of aromatic group increased. The elemental analysis showed that soot from lower fuel flow rates had more hydrogen and oxygen content than those from higher flow rates. The experimental observations indicate that both physical and chemical characteristics of soot derived from toluene flame are dependent on the fuel flow rate used for its production.

Vanadium catalysts supported on Al(Zr)-MCM-41-type materials were prepared by impregnation. Textural and structural properties, elemental composition and electronic structure were determined by N2 physisorption, small-angle XRD, SEM?EDX and UV?vis DRS, respectively. Al-containing materials showed mostly of Al framework and a small fraction of Al extra-framework species. Zr-containing materials presented almost exclusively small clusters of ZrxOy covering the MCM-41 matrix. Vanadium catalysts, showed the presence of isolated V5+ species and to a lesser extent polymeric chains likely as small crystallites of V2O5. The catalytic results revealed that VAlM30 catalyst, characterized by a Si/Al atomic ratio of 30, was the most active in thiophene hydrodesulfurization, which could be associated to better textural properties and high dispersion of the vanadium species. Fil: Escalante Contreras, Yelisbeth Carolina. Instituto Venezolano de Investigaciones Científicas; Venezuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; Argentina Fil: Méndez, Franklin J.. Instituto Venezolano de Investigaciones Científicas; Venezuela. Universidad Nacional Autónoma de México; México Fil: Díaz, Yraida. Instituto Venezolano de Investigaciones Científicas; Venezuela Fil: Inojosa, Marcel. Instituto Venezolano de Investigaciones Científicas; Venezuela Fil: Morgado, Myloa. Instituto Venezolano de Investigaciones Científicas; Venezuela Fil: Delgado, Miguel. Universidad de los Andes; Colombia Fil: Bastardo González, Ernesto. Universidad de Oriente; Venezuela Fil: Brito, Joaquín L.. Instituto Venezolano de Investigaciones Científicas; Venezuela

espanolEl presente estudio es un primer acercamiento para determinar la factibilidad en el uso del recubrimiento denominado “Electroless Nickel”, como una opcion para el reforzamiento anticorrosivo de piezas boronizadas, las cuales pueden presentar microgrietas durante su uso normal. Para este estudio, se evaluo si hay difusion del recubrimiento en el compuesto intermetalico. Se emplearon muestras industriales de tuberia de acero al carbono J55 boronizado segun proceso EndurAlloyMR (por Endurance Technologies Inc., Calgary, Canada). Las probetas fueron limpiadas y decapadas para luego ser recubiertas y tratadas termicamente. La caracterizacion morfologica se llevo a cabo por Microscopia Electronica de Barrido (MEB). La distribucion elemental en la zona de contacto entre el recubrimiento y el compuesto intermetalico se determino empleando la tecnica EDX – Mapping, y la zona de difusion se determino empleando la tecnica EDX – LineScan. Los resultados obtenidos en el analisis elemental, permitieron comprobar la existencia de una zona de difusion entre el recubrimiento y el compuesto intermetalico de aproximadamente 5 µm de espesor lo que se traduce en una excelente adherencia, aumentando la probabilidad de cubrir las microgrietas y preservando la proteccion anticorrosiva de piezas boronizadas. EnglishThe present study is a first approach to determine the feasibility of using the "Electroless Nickel" coating, as an option for the anticorrosive reinforcement of borided parts, which may present micro-cracks during normal use. For this study, it was evaluated if there is diffusion of the coating in the intermetallic compound. We used industrial samples of borided carbon steel J55 pipe according to EndurAlloyMR process (by Endurance Technologies Inc., Calgary, Canada). The test pieces were cleaned, pickled, coated and heat-treated. The morphological characterization was carried out by Scanning Electron Microscopy (SEM). The elemental distribution in the contact zone between the coating and the intermetallic compound was determined using the EDX - Mapping technique and the diffusion area was determined using the EDX - LineScan technique. The results obtained in the elemental analysis allowed verifying the existence of a diffusion zone between the coating and the intermetallic compound of approximately 5-μm thickness, which translates into an excellent adhesion, increasing the probability of covering the micro-cracks and preserving the anticorrosive protection of borided parts.

Dust acoustic wave propagation in weak magnetized homogeneous dusty plasmas has been extensively and successfully studied by different authors. Here, it is analyzed the behavior of electrostatic drift waves of very low frequency, appearing as due to the motion of plasma particles across the static magnetic field and the inhomogeneity introduced by the distribution of the particles in the dusty plasma generating the well-known diamagnetic effect. To study this situation, the kinetic Vlasov model in plasmas will be used. However, these models tend to behave unstably driven by the quasi-equilibrium of the diamagnetic current arising by the heavier species of dusty plasma particles. While other authors have used a standard state equation, such as the Van der Waals one, here, a more accurate model has been chosen as the equation of Ree and Hoover, a state equation that can be considered as a new form of the state equation. Together with the multipole approximation of the dispersion function, Z53 [P. Martin et al., J. Math. Phys. 21, 280–283 (1980)] allows a new derivation to obtain the simplest form of the dispersion relation in the form of a polynomial with complex coefficients. This mathematical approach was realized successfully and allowed straightforward calculus of the growth rate due to the drift unstable mode. This problem has been extensively analyzed in this work, including the non-ideal effect of dusty plasmas. These unstable modes are well discriminated and plotted as a function of the density of the grains in dusty plasma and their radius. Temperature gradients and charge fluctuation have been ignored.

The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends.

The catalytic performance of Al2O3-supported monometallic and bimetallic catalysts in selective hydrogenation of 1,3-butadiene in the presence of 1-butene under liquid phase conditions was studied. Bimetallic catalysts were prepared by the coimpregnation method with the required amounts of the precursors salts [Ni(NO3)2·6H2O and Pd(NH3)4Cl2·H2O] over pellet-form γ-Al2O3 with a constant content of Pd (0.5 wt%) and varying Ni/Pd atomic ratio (0.25, 0.5, 0.75, and 1) obtaining egg-shell profiles of the active components. The catalysts were characterized by X-ray diffraction, temperature-programmed techniques, such as reduction in hydrogen and desorption of ammonia, N2 physisorption, and transmission electron microscopy. The catalytic test showed that the 1,3-butadiene was selectively hydrogenated when bimetallic catalysts were used. The addition of Ni to the Pd-based catalysts suppressed n-butane formation and increased recovery of 1-butene at medium conversion. Therefore, it was observed an improved catalytic performance of the bimetallic catalysts being highest in the case of the 1NiPd/Al2O3.

Alumina supported (NH4)4[NiMo6-xWxO24H6]•5H2O Anderson type heteropolyoxometalates were synthesized by coprecipitation. These solids were used as precursors in the thiophene hydrodesulfurization catalytic at 400 °C. The catalytic precursors were characterized by textural properties (BET specific surface area and, total pore volume and pore diameter distribution), X-ray diffraction (XRD), IR spectroscopy (FTIR) and S analysis (CHON-S). The specific surface area was between 109 and 35 m2/g with total pore volume and pore diameter distribution of 0,11-0,34 cm3/g and 8,9-9,6 nm, respectively. XRD showed the presence of NiWO4, (NH4)4[NiMo6O24H6]•5H2O and WO3. FTIR analysis can be assigned to the characteristic vibrations of Anderson-type structure, due to stretching and bending of the functional groups present. The NiMo6-O/Al precursor was the most active in the HDS, it had a conversion of 72,75% and was even more active than the AERO commercial catalyst. The results of HDS revealed that the catalytic activity increases as follows: NiMo6-O/Al > AERO > NiMo3W3-O/Al > NiW6–O/Al. The catalytic selectivity of precursors and commercial catalyst (AERO) was directed towards the cis-butene. Se sintetizaron heteropolioxometalatos tipo Anderson (NH4)4[NiMo6-xWxO24H6]•5H2O soportados sobre γ-Al3O2, utilizando el método de coprecipitación. Estos solidos fueron utilizados como precursores en la reacción de hidrodesulfuración (HDS) de tiofeno a 400°C. Los precursores catalíticos se caracterizaron por propiedades texturales (área específica (B.E.T) y, distribución del diámetro y volumen de poros), difracción de rayos X (DRX), espectroscopía infrarroja (FT-IR) y análisis elemental (CHON-S). Las áreas específicas estuvieron dentro del intervalo de 109 y 35 m2/g con una distribución del diámetro y volumen de poros de 8,9-9,6 nm y 0,11-0,34 cm3/g, respectivamente. El análisis por DRX mostró la presencia de NiWO4, (NH4)4[NiMo6O24H6]•5H2O y WO3. Los análisis FT-IR determinaron la obtención de la estructura tipo Anderson, debido a las distintas flexiones y estiramientos de los grupos funcionales presentes. El precursor NiMo6-O/Al fue el más activo en la HDS, con un porcentaje de conversión de 72,75% e incluso fue más activo que el catalizador comercial AERO. Los resultados de HDS revelaron que la actividad catalítica en HDS se incrementa en el orden: NiMo6-O/Al > AERO > NiMo3W3-O/Al > NiW6–O/Al. La selectividad catalítica de precursores y el catalizador comercial (AERO) estuvo dirigida hacia cis-buteno.

Al2O3–Al sponges were manufactured by sintering and dissolution process with the aim of using these materials as structured catalytic reactors. For this purpose, several synthesis conditions were examined for the design of the cellular material, such as: particle size of NaCl, weight fraction of Al, compaction pressure, and sintering temperature or time. An alumina layers was grown on top of the aluminum surfaces during both: sintering and thermal treatment. The obtained results showed that the synthesized materials could be promising as structured reactors for endothermic or exothermic reactions.

A mixture of ferrites phases containing strontium ortho/hexagonal ferrites was synthesized using chitosan as template and heat treatments. The analysis by XRD, FTIR, SEM, TEM and HRTEM showed the coexistence of the perovskite-like SrFeO 2.9 and hexaferrite SrFe 12 O 19 phases. The ferrites consisted of hard agglomerates containing nanoparticles. The crystallites sizes range between 5 and 20 nm of different morphologies. A possible phase transition model is suggested.

Hexagonal mesoporous MCM-41-type molecular sieve has been functionalized with (3-mercaptopropyl)trimethoxysilane and used to heterogenize two large Co(II)- and Cu(II)-complexes containing a terpyridine-based Schiff base macrocyclic ligand. First, thiol groups were linked to the siliceous surface of the mesoporous host via grafting process. Some samples were characterized by FTIR, ICP-AES, SA-XRD, N2 physisorption, 13C-MAS-NMR, XPS and EPR. This set of characterization techniques confirmed a successful functionalization process, and also confirmed that the used experimental procedure allowed the heterogenization of Co(II)- and Cu(II)-complexes inside the pores of the functionalized host, retaining the mesoporous structure. The homo- and heterogeneous catalysts were active for cyclopentene oxidation. Co@MCM(F) sample was reported in this article as the best catalyst due to its higher activity and selectivity, as well as its low loss of catalytic activity after reuse.

Se variaron las condiciones de síntesis a fin de generar estructuras mixtas arcillo-carbonosas de molibdeno. Para ello, se modificó el contenido metálico y el tiempo de reducción/carburación en los diferentes ensayos. Los materiales obtenidos fueron caracterizados por Microscopía Electrónica de Barrido-EDX, Difracción de Rayos-X y fisisorción de nitrógeno. Las caracterizaciones realizadas mostraron que la fase predominante de molibdeno en los sistemas fue la carburada. Además, las condiciones de reacción más favorables para la preparación del material híbrido fueron con un tiempo de carburación/reducción de dos (2) horas y contenidos de Mo equivalentes a la capacidad de intercambio catiónico de la arcilla. Obteniendo así, materiales con interés catalítico en reacciones de hidrotratamiento., Synthesis conditions were varied in order to generate mixed clay-carbonaceous structures of molybdenum. For this, the metal content and the reduction/carburation time conditions were modified in the different experiments. The synthesized materials were characterized by Scanning Electron Microscopy-EDX, X-Ray Diffraction and N2 Physisorption. The characterizations carried out showed that carburized molybdenum phase was the predominant in the systems. In addition, the most favorable reaction conditions for the preparation of the hybrid material were with a carburetion/reduction time of two (2) hours and Mo contents equivalent to the cation exchange capacity of the clay. Therefore, obtaining materials with catalytic interest in hydrotreating reactions., {"references":["1. El-Nadjar W., Bonne M., Trela E., Rouleau L., Mino A., Hocine S., Payen E., Lancelot Ch., Lamonier C., Blanchard P., Courtois X., Can F., Duprez D., Royer S.; Microp. Mes. Mat. 158 (2012) 88–98. 2. Klissurski D., Petridis D., Abadzhieva N., Hadjiivanov K.; Appl. Clay Sci.10 (1996) 451. 3. Breysse M., Afanasiev P., Geantet Ch., Vrinat M.; Catal. Today 86 (2003) 5-16. 4. Dhandapani B., St. Clair T., Oyama S.T.; Appl. Catal. A: Gen. 168 (1998) 219-228. 5. Hynaux A., Sayag C., Suppan S., Trawczynski J., Lewandowski M., Szymanska-Kolasa A., DjégaMariadassou G.. Catal. Today 119 (2007) 19-22. 6. Gil A., Gandia L.M., Vicente M.A.. Catal. Rev-Sci and Eng. 42 (2000) 145-212. 7. Gonzalez-Jimenez F., Constant H., Iraldi R., Jaimes E., Rosa-Brussin M.; International Conference on the Application of the Mossbauer Effect 28 (1986) 927-930. 8. Ito T., Tsuchida Y.; Appl.Catal. 51 (1989) 213-222. 9. Kloprogge J.T., Duong L.V., Frost R.L.. Environ Geol. 47 (2005) 967-981. 10. Stucki, J. W. In Iron in Soils and Clay Minerals; Stucki, J. W., Goodman, B. A., Schwertmann, U., Eds.; D. Reidel: Dordrecht, Netherlands (1998) 625-675. 11. Li S., Kim W.B., Lee J.S., Chem. Mater. 10 (1998) 1853-1862. 12. Eswaramoorthi I., Sundaramurthy V., Das N., Dalai A.K., Adjaye J.; Appl. Catal. A: General 339 (2008) 187–195. 13. Figuereido J.L., Rivero F.R.; Catálise Heterogénea. Fundaçao Calouste Gulbenkian. Lisboa (1987) 77128."]}

Los compuestos orgánicos clorados, ya sean alifáticos o aromáticos, son sustancias ampliamente usadas como solventes, en síntesis de otros compuestos químicos, como pesticidas, odorantes, refrigerantes, entre otros. Igualmente representan una fuente importante de contaminación ambiental y un gran riesgo potencial a la salud por su aguda toxicidad y su bioacumulación. En los últimos años, la hidrodecloración catalítica se ha presentado como una técnica alternativa no destructiva y amigable al medio ambiente, convirtiéndose en una opción viable para la disposición final de los desechos químicos organoclorados. Dentro de los tipos de catalizadores estudiados para estas reacciones, están los fosfuros de metales de transición, en particular los fosfuros de níquel. De este tipo de catalizadores, se han reportado dos fases cristalinas que poseen actividad catalítica hacia las reacciones de hidrodecloración: Ni2P y Ni3P. La presente revisión engloba las técnicas de síntesis aplicadas para la obtención de catalizadores basados en fosfuros de níquel., Chlorinated organic compounds, whether aliphatic or aromatic, are substances widely used as solvents, in synthesis of other chemical compounds, such as pesticides, odorants, refrigerants, among others. They also represent an important source of environmental pollution and a great potential risk to health due to their acute toxicity and bioaccumulation. In recent years, catalytic hydrodechlorination has been presented as an alternative non-destructive and environmentally friendly technique, becoming a viable option for the final disposal of organochlorine chemical waste. Among the types of catalysts studied for this type of reactions are the transition metal phosphides, in particular the nickel phosphides. Of this type of catalysts, two crystalline phases have been reported that have catalytic activity towards the hydrodechlorination reactions: Ni2P and Ni3P. This review includes all techniques used in the synthesis of heterogeneous catalysts based on nickel phosphide., {"references":["1. R.T.Morrison, R.N.Boyd,\"Organic Chemistry\", 5ed. Englewood Cliffs, NJ: Prentice Hall, 1992. 2. B.G. Loganathan, K. Kannan,Ambio23 (1994) 187. 3. C. Bernes,\"Persistent organic pollutants: a Swedish view of an international problem\"Environmental Protection Agency, Monitor 16, Estocolmo, Suecia, 1998. 4. Convenio de Basilea. Tratado multilateral sobre el control de los movimientos transfronterizos de los desechos peligrosos y su eliminación, http://www.basel.int/, julio 2018. 5. Convenio de Estocolmo sobreContaminantes Orgánicos Persistentes (COP), Secretaría del Convenio de Estocolmo, Programa de las Naciones Unidas para el Medio Ambiente (PNUMA), http://www.wipo.int/edocs/lexdocs/treaties/es/unep-pop/trt_unep_pop_2.pdf, julio 2018. 6. C. Visvanathan. Resour. Conserv. Recycl. 16(1996) 201. 7. C.P. Huang, C. Dong, Z. Tang, Waste manage.13(1993) 361. 8. Y. Mitoma, T. Uda, N. Egashira, C. Simion, H. Tashiro, M. Tashiro, X. Fan,Environ. Sci. Technol. 38(2004) 1216. 9. O. Yilmaz, K. Ünlü, E. Cokca,J. Environ. Eng. 129(2003) 366. 10. H. Huang, L. Tang,Energy Conv. Manage.48(2007) 1331. 11. B. Padilla Vivas, F.V. Díez Sanz, Fernando Valeriano, S. Ordóñez García, Ingeniería del agua. 12(2005) 361. 12. A. Śrębowata, I. I. Kamińska, D. Giziński, D. Wideł, J. Oszczudłowski, Catal. Today, 251 (2015) 60. 13. A. Śrębowata, R. Baran, D. Lisovytskiy, I.I. Kamińska, S. Dzwigaj, Catal. Commun. 57 (2014) 107. 14. S. Zinovyev, P. Tundo, Appl. Catal. B-Environ. 75 (2007) 124. 15. W. Wua, J. Xua, R. Ohnishi, Appl. Catal. B-Environ. 60 (2005) 129. 16. S. Ordóñez, H. Sastre, F.V. Dı ́ez, Appl. Catal. B-Environ. 25 (2000) 49. 17. O. El-Sharnouby, H. K. Boparai, J. Herrera, D. M. O'Carroll, Chem. Eng. J. 342 (2018) 281. 18. A. Perosa, M. Selva, T. Maschmeyer, Chemosphere, 173 (2017) 535. 19. M. De La Rosa, P. Betancourt, A. Díaz, J. L. Brito, S. Pinto-Castilla, Reac. Kinet. Mech. Catal. 111 (2014) 277. 20. A. Śrębowata, W. Juszczyk, Z. Kaszkur, J. W. Sobczak, L. Kępiński, Z. Karpiński, Appl.Catal. A-Gen. 319 (2007) 181. 21. R. Del Toro, M. Minichini, J.L. Brito, P. Betancourt, Catal. Lett. 143 (2013) 1145. 22. L. Delannoy, J.-M. Giraudon, P. Granger, L. Leclercq, G. Leclercq, Appl. Catal. B-Environ. 37 (2002) 161. 23. H. Xu, S. Lu, L. Ren, Int. J. Hydrog. Energy, 42 (2017) 18383. 24. J.A. Cecilia, A. Infantes-Molina, E. Rodríguez-Castellón, J. Hazard. Mater. 296 (2015) 112. 25. T. Oyama, T. Gott, H. Zhao, Y.-K. Lee,Catal. Today 143 (2009) 94. 26. C.Stinner, Z.Tang, M.Haouas, T.Weber, R.PrinsJ.Catal. 208 (2002) 456. 27. J. Chen, S. Zhou, X. Liu, J.Zhang,Catal. Lett.122(2008) 167. 28. X. Liu, J. Chen, J. Zhang,Catal.Commun. 8 (2007) 1905. 29. X.Liu, J.Chen, J. Zhang,Ind. Eng.Chem. Res. 47 (2008) 5362. 30. L. Song, S. Zhang, Q. Wei, Catal.Commun. 12 (2011) 1157. 31. J.A. Cecilia, A. Infantes-Molina, E. Rodríguez-Castellón, A. Jiménez-López, J. Catal. 263 (2009) 4. 32. S. Sada, T. Shirasaki, K. Morikawa, J. Soc. Chem.Ind. 71 (1968)626. 33. J. Chen, D. Ci, R. Wang, J. Zhang, Appl.Surf.Sci 255 (2008) 3300. 34. J.A. Cecilia, I. Jiménez-Morales, A. Infantes-Molina, E. Rodríguez-Castellón, A. Jiménez-López, J. Mol.Catal. A-Chem. 368 (2013) 78. 35. J. Guan, Y. Wang, M. Qin, Y. Yang, X. Li, A. Wang, J. Solid St. Chem. 182 (2009) 1550. 36. A. Wang, M. Qin, J. Guan, L. Wang, H. Guo, X. Li, Y. Wang, R. Prins, Y. Hu, Angew. Chem. Int. Ed. 47 (2008) 6052. 37. J.A. Cecilia, A. Infantes-Molina, E. Rodríguez-Castellón, J. Hazard. Mater. 296 (2015) 112. 38. Q. Yang, J. Dai, K. Li, J. Chen,Chin. J. Catal. 34 (2013) 1201. 39. H.Xu, S.Lu, L. Ren, Int. J. Hydrog. En.42 (2017)18383."]}

Multiwall carbon nanotubes (MWCNTs) were synthesized using p-xylene and FeMo/MgO catalysts prepared by two methods (co-impregnation and sol–gel). Carbon nanotubes with uniform diameters were obtained by catalytic chemical vapor deposition at 900 °C using FeMo/MgO catalyst prepared by sol–gel method. The sol–gel method resulted in a higher yield than the co-impregnation method; this was attributed to the better dispersion of the metallic nanoparticles due to the sponge-like structure. Additionally, MWCNTs with lower metals content were obtained after three steps of purification.

A new approach has been tested for the preparation of metal/Mo2C catalysts using mixed-metal oxide molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu3(MoO4)2(OH)2, α-NiMoO4 and CoMoO4·nH2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu2+, Ni2+ and Co2+ cations inside each molybdate. The synthesized Cu/Mo2C, Ni/Mo2C and Co/Mo2C catalysts were highly active for the hydrogenation of CO2. The metal/Mo2C systems exhibited large variations in the selectivity towards methanol, methane and CnH2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo2C displayed a high selectivity for CO and methanol production. Ni/Mo2C and Co/Mo2C were the most active catalysts for the activation and full decomposition of CO2, showing high selectivity for the production of methane (Ni case) and CnH2n+2 (n > 2) hydrocarbons (Co case).

Se emplearon nanopartículas de aluminofosfatos amorfos entre 23 a 30 nm de diámetro para la adsorción de iones plomo (Pb2+) en soluciones acuosas. Los materiales fueron sintetizados mediante biosíntesis utilizando como plantillas biológicas las células de levadura Saccharomyces cerevisiae. Los estudios de adsorción se llevaron a cabo empleando el método batch, utilizando 100 mg del sólido nanométrico y 200 µg L-1 de iones plomo. La determinación cuantitativa de Pb+2 fue realizada mediante espectrometría de absorción atómica con atomización electrotérmica (EAA-HG). Los valores obtenidos para el porcentaje de remoción (% EF), capacidad de adsorción qe (µg g-1 ) y coeficiente de remoción Kd (mL g -1 ) fueron de 40; 90 y 800 en promedio, respectivamente. Los resultados obtenidos demostraron las potencialidades que presentan estos materiales para la adsorción de iones Pb2+, siendo excelentes candidatos para la remediación de aguas contaminadas.

Graphical abstract, This study reports the synthesis of porous nano alumina employing carboxylato-alumoxanes [Al(O)x(OH)y(O2CR)z]n as precursors for controlling the pore size, pore size distribution and porosity of the alumina, using a new process ecofriendly. The carboxylato-alumoxanes was prepared by the reaction of boehmite with carboxylic acids. The boehmite was obtained by the hydrolysis of aluminum alkoxide in an aqueous solution. The colophony extract is employed as a source of carboxylic acids. The materials were characterized, using XRD, TGA, N2 physical adsorption, SEM, TEM, NMR and FTIR. A mechanism was proposed for the formation of the synthesized structures. TEM measurements confirmed particle size ranged from 5 to 8 nm.

Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálculo, B3LYP (DFT) para el nivel alto y UFF (Mecánica Molecular) para el nivel bajo. Se calcularon los agregados pequeños para analizar las geometrías de Au2-3 y Cu2-3 soportados sobre SAPO-11. Igualmente CO-Au2-3/SAPO-11 y COCu2-3/SAPO-11 obtenidos por interacción con CO y su oxidación, fueron calculados. Se reporta el cambio de energía ∆Eads de los agregados metálicos con la adsorción de CO, las distancias de enlaces C-O, M-CO y las frecuencias vibracionales calculadas de C=O. Las estructuras más estables de Au2-3 y Cu2-3/SAPO-11 son similares, excepto que el Au3 exhibe una geometría triangular escaleno y Cu3 una geometría triangular isósceles. Los valores de CO ΔEads revelan que la adsorción de CO es más estable en Au2-3/SAPO-11 que en Cu2-3/SAPO11. Se obtiene la oxidación de todos los CO-clúster pero la oxidación es completa sólo en el caso de Cu2 lográndose especies oxidadas intermedias en los fragmentos Au2, Au3 y Cu3., Quantum chemistry calculations were carried out using the ONIOM2 methodology at two levels of calculation, B3LYP (DFT) for the high level and UFF (MM) for the low level. The small aggregates were calculated to analyze the geometries of Au2-3 and Cu2-3 supported on SAPO-11, as well as the CO-Au2-3/SAPO-11 and COCu2-3/SAPO-11 obtained by their interaction with CO and its oxidation were calculated. The energy change ∆Eads of the metal clusters with CO adsorption, C-O and M-CO bond distances and calculated C=O stretching frequencies are reported. The most stable structures of the aggregates of Au2-3 and Cu2-3/SAPO-11 are similar, except that Au3 exhibits scalene triangle geometry and Cu3 shows isosceles triangle geometry. The CO ΔEads values reveal that the CO adsorption is more stable in Au2-3/SAPO-11 than in Cu2-3/SAPO-11. The oxidation of all CO-clusters is obtained, however the oxidation is complete only in the Cu2 case and oxidized intermediate species are achieved in the Au2, Au3 and Cu3 moieties., {"references":["1. M. Haruta, T. Kobayashi, H. Sano, N. Yamada. Chem. Lett. 2 (1987) 405-408. 2. G.C. Bond, D.T. Thompson. Cat. Rev.‐Sci. Eng. 41 (1999) 319-388. 3. M. Haruta. Cat.Today 36 (1997) 153-166. 4. Z. Qu, L. Giurgiu, E. Roduner. Chem. Comm. (2006) 2507-2509. 5. Y. Dong, M. Springborg. Eur. Phys. J. 43 (2007) 15-18. 6. B. Griffe, A. Sierraalta, J.L. Brito. Int. J. Quantum Chem.110 (2010) 2573-2582. 7. B. Griffe, J.L. Brito, A. Sierraalta. J. Mol. Cat. A: Chem. 315 (2010) 28–34. 8. B. Griffe, J.L. Brito, A. Sierraalta. Comp. Theor. Chem. 1042 (2014) 69–83. 9. K. Mathisien, M. Stockenhuber, D.G. Nicholson. Phys. Chem. Chem. Phys. 11(2009) 5476-5488. 10. D.L. Hoang, T.T.H. Dang, J. Engeldinger, M. Schneider, J. Radnik, M. Richter, A. Martin. J. Solid St. Chem. 184 (2011) 1915-1923. 11. J. Xue, X. Wang, G. Qi, J. Wang, M. Shen, W. Li. J. Cat. 297 (2013) 56-64. 12. K. Frolich, R. Bulanek, E. Frydova. Microp. Mesop. Mat. 186 (2014) 37-45. 13. O. Bludsky, P. Nachtigall, P. Cicmanec, P. Knotek, R. Bulanek. Cat. Today 100 (2005) 385-389. 14. K. Gora-Marek, A.E. Palomares, A. Glanowska, K. Sadowska, J. Datka. Microp. Mesop. Mat. 162 (2012) 175-180. 15. D. Sengupta, W.F. Schneider, K.C. Hass, J.B. Adams. Cat. Lett. 61 (1999) 179-186. 16. B. Griffe, A. Sierraalta, J.L. Brito. J. Comp. Met. Sci. Eng. 12 (2012) 391-396. 17. B. Griffe, A. Sierraalta. Ciencia 22 (Número Especial) (2014) 45 - 51. 18. B. Griffe, J. A. Brito, A. Sierraalta. J. Comp. Met. Sci. Eng. 14 (2014) 45-52. 19. B. Griffe, A. Sierraalta, J.L. Brito. XXIV Congreso Iberoamericano de Catálisis CICAT (2014) No 176. 20. B. Griffe, J.L. Brito, A. Sierraalta. V Congreso de Físico-Química Teórica y Computacional, V CFQTC 2014. 21. B. Griffe, J.L. Brito, A. Sierraalta. J. Comp. Met. Sci. Eng. 17 (2017) 89-96. 22. Gaussian 03, Revisión B.04, Gaussian Inc., Pittsburg, PA (2003). 23. A. Pestryakov, I. Tuzovskaya, E. Smolentseva, N. Bogdanchikova, F.C. Jentoft, A. Knop-Gericke. Int. J. Mod. Phys. B19 (2005) 2321-2326. 24. A. Sierraalta, R. Añez, L. Diaz, R. Gomperts. J. Phys. Chem. A 114 (2010) 6870-6878. 25. National Institute of Standards and Technology www.nist.gov NIST Chemistry Web Book. 26. K. Okumura, K. Yoshino, K. Kato, M. Niwa. J. Phys. Chem. B 109 (2005) 12380-12386."]}

The Au3-5 clusters supported on silico-aluminophospates (SAPO-11) were studied using quantum chemistry calculations, by means of the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au3/SAPO-11, Au4/SAPO-11, Au5/SAPO-11, CO–Au3/SAPO-11, CO–Au4/SAPO-11 and CO–Au5/SAPO-11 aggregates to analyze the geometries of small clusters of Au3, Au4 and Au5 on SAPO-11 support. Au3 cluster presents a triangle structure in Au3/SAPO-11. Au4 cluster shows a “Y shaped” structure in Au4/SAPO-11. Au4 as a rhombus structure is also studied but it is a less stable structure. Au5 cluster displays a “pentagon shaped” structure as the most stable. The CO interaction with Au3, Au4 and Au5/SAPO-11 is studied; this CO adsorption is different from that reported in the literature. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔEads on them and the change of energy of the oxidation reaction are presented. Some relevant charges and bond indexes were calculated. On supporting all Au3-5 there is a charge transfer from the Au cluster to the binding O atoms. On CO adsorption in all Au3-5 clusters there is a charge transfer from the cluster to the CO.

Ni–Mo carbides supported on activated carbon were synthesized by carbothermal hydrogen reduction and the effect of the sulfidability on the thiophene hydrodesulfurization catalytic activity was studied. The X-ray diffraction patterns of Ni–Mo carbides showed the presence of β-Mo 2 C and NiC when the atomic ratio AR = Ni/(Ni + Mo) was between 0.25 and 0.75, while for AR = 1, it only was detected metallic Ni. The X-ray photoelectron spectroscopy results showed the distribution of different surface species in the passivated catalysts: Mo δ + (0 ≤ δ ≤ 2), Mo 4 + , Mo 6 + , Ni δ + and Ni 2 + . After sulfiding the carbides were modified in their surface and catalytic activity.

Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au_{5}/SAPO-11, Au_{6}/SAPO-11, CO-Au_{5}/SAPO-11 and CO-Au_{6}/SAPO-11 aggregates to analyze the geometries of small clusters of Au_{5} and Au_{6} on SAPO-11 support. Au_{5} cluster presents a pentagonal structure in Au_{5}/SAPO-11. Au_{6} aggregate shows a "multi triangular" structure as from a trapezoidal "W shaped" Au_{5} in Au_{6}/SAPO-11. Au_{5} is also obtained as an "X shaped" structure. Similarly another Au_{6} aggregate configuration is obtained also multi triangular but as from X shape Au_{5} cluster. The CO interaction with Au_{5} and Au_{6}/SAPO-11 is studied. The formation energy ΔE_{F} of the aggregates, the CO adsorption energy ΔE_{ads} on them and CO frequency are presented.

The effect of the pre-adsorption of sulfur on the hexagonal-Mo_{2}C-001 surface in the hydrodechlorination HDC reaction of chlorobenzene was studied using density functional theory DFT calculations. The results related with the coordination modes and the adsorption energies of the aromatic molecule suggest that the main effect of the sulfur incorporation into the surface is to lead towards a weaker chlorobenzene adsorption that will benefit the continuity of the catalytic cycle and therefore to avoid the carbonization and chlorination of the catalyst. The study of the HDC mechanism was also performed and two different reaction paths were considered. The calculated energy barriers indicate that both mechanisms may occur at the normal reaction temperature 350°C. These latter approaches involve new roles of the superficial sulfur as atomic or radical hydrogen scavenger for the S-Hformation and as a precursor of the σ chlorobenzene coordination, necessary for effective hydrogenation in the proposed mechanisms.

The effect of the cobalt addition on the H2S inhibition and subsequently on the polychlorinated biphenyl (PCB) hydrodechlorination (HDC) activity over Mo-based catalysts was investigated. The HDC activity over a Mo catalyst containing cobalt was much higher than that over the same Mo catalyst without cobalt. On the other hand, the HDC activity of the Co–Mo catalyst was more inhibited by H2S than that of the Mo catalyst at 300 °C. Thus, kinetic parameters were calculated using a Langmuir–Hinshelwood model to determine the reaction pathway of the H2S inhibition over Mo and Co–Mo catalysts. We found that the heats of adsorption of PCB (Aroclor® 1242) and H2S on the Co–Mo catalyst was higher than on the Mo catalyst, indicating that the sulfur-containing species adsorb more strongly on the catalyst containing cobalt. The results suggested that while the Co–Mo catalyst was more inhibited by H2S, the Mo–S bonds were more stable on this catalyst than on the solely Mo catalyst. This Mo–S bond was responsible for the stabilization of the active phase, which allowed creation of a greater amount of sulfur atoms potentially labile. Thus, that explained the better HDC activity over the Co–Mo catalyst than over the Mo catalyst, despite a greater H2S inhibition on the former.

Pechini sol–gel method has been employed for the preparation of nanocrystalline La0.8Sr0.2FeO3 perovskite. The synthesis procedure was optimized by varying the calcination temperature. The results revealed the decomposition of the resin precursor and confirmed the formation of the perovskite phase starting at 600 °C with spherical morphology (

Unsupported Mo carbide and Mo nitride catalysts have been synthesized by temperature programmed synthesis, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction and desorption and N2 physisorption. These solid compounds have been tested for the hydrodechlorination (HDCl) of polychlorinated biphenyls (PCBs) at 1 bar in a fixed bed reactor. The Mo carbides and the corresponding Mo nitride phases showed a catalytic activity higher than a conventional HDS catalyst consisting of alumina-supported NiMo sulfides (~35 %). Aroclor 1260 HDCl conversion results were related to spilt-over hydrogen species that were proposed to favor the hydrogenolysis of C–Cl bond on refractory phases. The original PCBs broad distribution changed almost completely to non-chlorinated biphenyl on the carbide and nitride catalysts.