Xn:Harmful;
827-52-1Relevant academic research and scientific papers
The use of inorganic Al-HMS as a support for NiMoW sulfide HDS catalysts
Alonso-Nú?ez, G.,Huirache-Acu?a, R.,Maya-Yescas, R.,Pawelec, B.,Rivera-Mu?oz, E. M.,Vázquez, P. J.,Zepeda, T. A.
, (2021)
Inorganic hexagonal mesoporous silica (HMS) and aluminum modified HMS materials (Al-HMS) were prepared and used as supports of transition metal sulfide hydrodesulfurization (HDS) catalysts based on nickel, molybdenum, and tungsten as active phase. The samples were characterized with XRD, HRTEM, TPD, N2 physisorption and UV–Vis. The catalytic activity of the trimetallic catalysts was performed in the HDS of dibenzothiophene (DBT). When Al was incorporated into the inorganic support, important changes and effects were observed on the physicochemical properties. On the other hand, the incorporation of Al into the HMS led to a decrease in the reaction rate (k) and a trend toward a direct path of desulfurization was observed for all materials.
Bulk hydrotreating MonW12-nS2 catalysts based on SiMonW12-n heteropolyacids prepared by alumina elimination method
Kokliukhin,Nikulshina,Mozhaev,Lancelot,Lamonier,Nuns,Blanchard,Bugaev,Nikulshin
, p. 26 - 37 (2021)
A series of unsupported mono- and bimetallic MonW12-nS2 catalysts were synthesized by alumina elimination from supported MonW12-nS2/Al2O3 samples using acid etching. Alumina supported catalysts have been in turn prepared by using monometallic H4SiMo12O40 and H4SiW12O40 heteropolyacids (HPAs), their mixture with Mo/W atomic ratio equal to 1/11 and 3/9, and mixed bimetallic H4SiMo1W11O40 and H4SiMo3W9O40 HPAs. All catalysts were characterized by N2 adsorption, temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), extended X-ray absorption fine structure (EXAFS) spectroscopy and powder X-ray diffraction (XRD) and their performance were evaluated in simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of naphthalene. The etching process led to a successful removal of all the support and of the partially sulfided species, with sulfidation degrees of both Mo and W above 90 % on the final bulk solids. The active phase also underwent a rearrangement, as higher average length and stacking were measured on the bulk catalysts than on the original supported ones. Mixed MoWS2 phase was evidenced in all solids, prepared from mixed HPAs (MonW12-nS2) or from the mixture of monometallic HPAs (RefMonW12-nS2), by EXAFS and ToF-SIMS, with however a larger quantity on the MoW solids. It seems that the mixed MoWS2 phase observed on the supported MoW catalysts is maintained through the etching process, while on RefMonW12-nS2 the mixed phase, observed in a much lesser extent in the corresponding supported catalyst, could result from the aggregation of the monometallic slabs. MonW12-nS2 catalysts were found more effective than the monometallic catalysts and than the corresponding RefMonW12-nS2, in both dibenzothiophene hydrodesulfurization and naphthalene hydrogenation, which was related to the presence of the mixed phase maintained through the etching of the support.
A feasible approach to the synthesis of nickel phosphide for hydrodesulfurization
Guan, Qingxin,Cheng, Xun,Li, Rongguan,Li, Wei
, p. 1 - 9 (2013)
In this paper, we propose a simple and feasible method for synthesizing bulk and supported nickel phosphides from oxide precursors. The new approach uses a low hydrogen flow speed and is not affected by the heating rate. The results indicate that Ni2P can be synthesized at 600 °C from its oxide precursors with a mole ratio of Ni/P = 2/1. The hydrodesulfurization activity results indicate that the direct-reduction method shows excellent performance in the synthesis of supported catalysts.
Comparative activity of Ni-W and Co-Mo sulfides using transition metal oxides as precursors in HDS reaction of DBT
Quintana-Melgoza, Juan Manuel,Alonso-Nunez, Gabriel,Homero-Galvan, Donald,Avalos-Borja, Miguel
, p. 1082 - 1088,7 (2012)
Unsupported catalysts based on nickel, cobalt, tungsten, and molybdenum were prepared by sulphurization of Ni, Co, W, and Mo oxides. All catalysts were tested in hydrodesulphurization of dibenzothiophene reaction. The best activity was attained with a sample based on W (5.64 × 1016 molecules/s m2). The best selectivity for biphenyl (70.14 %) was achieved with Ni17S18. Materials were characterized by X-ray diffraction and surface area measurements. Graphical Abstract: Reaction network for hydrodesulphurization (HDS) of dibenzotiophene (DBT) by direct desulphurization pathway (DDS) and hydrogenating pathway (HYD) to produce biphenyl (BP) and cyclohexyl-benzene (CHB). nH2 = hydrogen excess at 3.378 MPa, dihydrodibenzotiophene (DHDBT), tetrahydrodibenzothiophene (THDBT), hexahydrodibenzothiophene (HHDBT), hydrogen sulphide (H2S). Ni 17S18 as a yield of 12.03 % THDBT, 17.83 % CHB, and 70.14 % BP.[Figure not available: see fulltext.]
Iron(II) bipyridine complexes for the cross-coupling reaction of bromocyclohexane with phenylmagnesium bromide
Matsubara, Yutaka,Yamaguchi, Takamichi,Hashimoto, Toru,Yamaguchi, Yoshitaka
, p. 198 - 202 (2017)
Three known iron(II) complexes bearing a bipyridine ligand, [FeCl2(bpy)2] (1), [FeCl2(bpy)]2 (2) and [FeCl2(dmbpy)] (3) (bpy?=?2,2′-bipyridine and dmbpy?=?6,6′-dimethyl-2,2′-bipyridine) were employed for the cross-coupling reaction of bromocyclohexane (4) with phenylmagnesium bromide (5). These complexes catalyzed the cross-coupling reaction. Among the three catalysts, complex 2 acted as an effective catalyst to afford the cross-coupled product phenylcyclohexane (6) in 92% yield. The X-ray crystal structure analyses of 2 and 3 were demonstrated.
Enhancement of biphenyl hydrogenation over gold catalysts supported on Fe-, Ce- and Ti-modified mesoporous silica (HMS)
Castano, Pedro,Zepeda,Pawelec,Makkee, Michiel,Fierro
, p. 30 - 39 (2009)
Mesoporous metallosilicates (HMS-M; M = Ce, Fe, Ti) were used as supports for the preparation of Au catalysts, and were tested in the liquid-phase hydrogenation of biphenyl at 5 MPa and 488 K. Irrespective of the support, uniformly dispersed Au nanoparticles in range 3.2-6.5 nm were obtained. The highest turn over frequency (TOF), expressed per surface Au atom, was achieved on the Au/HMS-Fe, furthermore this catalyst gave the highest selectivity to the most saturated compound (bicyclohexyl with the highest cetane number) by means of enhancing the second aromatic-ring hydrogenation. From the catalyst activity-structure correlation, the highest activity of the Au/HMS-Fe catalyst is linked with: (i) the higher ratio of positively charged metallic gold Auδ+/Si (XPS), and (ii) the higher stability of Au nanoparticles (HRTEM). A linear correlation between the activity (per gram of metal) of the catalysts and their ratio Auδ+/Si is observed; however, Au/HMS-Ce catalyst displays a different behaviour in terms of activity per gram of metal exposed caused by the fact that ceria is not incorporated in the framework.
Visible-light-induced photocatalytic benzene/cyclohexane cross-coupling utilizing a ligand-to-metal charge transfer benzene complex adsorbed on titanium oxides
Yamamoto,Ohara,Yoshida
, p. 2046 - 2050 (2018)
The cross-coupling reaction of benzene and cyclohexane molecules proceeded selectively over Pd-modified titanium dioxide photocatalysts under visible light. A ligand-to-metal charge-transfer (LMCT) complex of benzene adsorbed on titanium oxide was proposed as the key species for the selective formation of the cross-coupling product.
Hydrodesulfurization of Dibenzothiophene Catalyzed by Silica-Alumina Supported Anionic Molybdenum Carbonyl Complexes
Ishihara, Atsushi,Shirouchi, Kenji,Kabe, Toshiaki
, p. 589 - 592 (1993)
In hydrodesulfurization (HDS) of dibenzothiophene (DBT), the catalysts prepared from silica-alumina supported molybdenum compounds showed higher yields of biphenyl, cyclohexylbenzene and bicyclohexyl than conventional sulfided molibdena-alumina. Specifically, the catalysts derived from silica-alumina supported anionic molybdenum carbonyls gave the highest yields among silica-alumina supported ones.
The selectivity of sulfided NiW/Al2O3 catalyst in the hydrodesulfurization of dibenzothiophene
Nagai
, p. 3052 - 3054 (1989)
The hydrodesulfurization of petroleum residue is widely practiced and the need for a similar technology for coal-derived liquids is well recongnized. The selectivity of a sulfided NiW/Al2O3 catalyst for hydrodesulfurization has been studied at 300°C and 10.1 MPa total pressure. The presence of oxygen and sulfur compounds depressed the desulfurization of dibenzothiophene, but not the hydrogenation. The addition of large amounts of acridine improved the catalytic activity significantly for the desulfurization of dibenzothiophene to biphenyl while preventing hydrogenation.
On the oxidation state of iron in iron-mediated C-C couplings
Hedstr?m, Anna,Lindstedt, Erik,Norrby, Per-Ola
, p. 51 - 55 (2013)
The nature of the active catalyst in iron-catalyzed C-C couplings has been under debate. In here, we study the couplings with aryl Grignard reagents, and clearly show that the active catalyst is an Fe(I) species. The Grignard alone can reduce the pre-catalyst to the Fe(I) state, and no further, as shown by quantification of product formation. Addition of the electrophile results in complete cross-coupling, validating the nature of the active catalyst. A computational study reveals that the active iron catalyst has a spin state of S = 3/2, high spin for Fe(I) but intermediate spin for Fe(III) complexes, even though the Fe(III) precatalyst salts have a high spin state (S = 5/2). The spin change occurs after the first transmetallation, when the strong ligand field of the aryl group raises the energy of one d-orbital, inducing an electron pairing event. All steps in the formation of an active cross-coupling catalyst are facile and strongly exergonic.
