624-64-6Relevant articles and documents
Hydrocarbon reactions on MoS2 revisited, II: Catalytic properties in alkene hydrogenation, cis-trans isomerization, and H2/D2 exchange
Polyakov, Mykola,Poisot, Martha,Bensch, Wolfgang,Muhler, Martin,Gruenert, Wolfgang
, p. 137 - 144 (2008)
MoS2 prepared by thermal decomposition of ammonium tetrathiomolybdate in inert gas at temperatures up to 773 K was activated by treatments involving thermoevacuation at 723 K and/or reduction at 573 K. The effect of different activations on the activity in ethylene hydrogenation, cis-trans isomerization of 2-butene, and H2/D2 isotope exchange (all measured at temperatures around 473 K) was compared, taking into account the extent of Mo exposition as measured by oxygen chemisorption. It was found that activation had a widely varying impact on the test reactions, indicating that these proceed on sites with different numbers of vacancies. Hydrogenation activity was boosted by two orders of magnitude when reduction of the catalyst at 573 K was followed by thermoevacuation at 723 K, whereas this change was moderate with H2/D2 exchange and negative with cis-trans isomerization. For the latter reaction, mere thermoevacuation was a suitable activation, and the impact of subsequent catalyst reduction was negative, whereas appreciable activity in the former reactions was obtained only when thermoevacuation was combined with a subsequent reduction. The data suggest that all three reactions proceeded on different sites, probably 3 vacancies per Mo for olefin hydrogenation, 2 vacancies per Mo for H2/D2 exchange, and 1 vacancy per Mo for cis-trans isomerization, with the latter two reactions involving adjacent {single bond}SH groups. Sites with greater Mo exposure than stated may be suitable for H2/D2 exchange but not for cis-trans isomerization. With increasing severity of the activation treatments, sites with a small number of vacancies appeared to combine and migrate toward the rims or to escape into the bulk. Therefore, very high hydrogenation activity may be seen on surfaces with an oxygen chemisorption capacity far from the maximum value occurring after less drastic treatments. Our findings imply that a combination of chemisorption studies with test reactions may be a valuable tool for surface characterization of sulfide catalysts.
Stereoselectivity in the Metathesis Reaction of But-2-ene on a β-Titanium Oxide-supported Molybdenum Oyxide
Tanaka, Katsumi,Tanaka, Ken-ichi,Miyahara, Koshiro
, p. 666 - 667 (1980)
With MoOx/β-TiO2 as catalyst the stereoselective formation of cis- and trans-but-2-ene is observed in the metathesis of equimolar mixtures of cis-- and -but-2-ene, and trans-- and --but-2-ene, respectively; the yields of cis- and trans-but-2-ene from reactions of the corresponding pent-2-ene isomers are in good agreement, but metathesis of propene selectively yields trans-but-2-ene.
The Photocatalytic Isomerization of 2-Butenes on ZrO2 Catalyst with Low Coordinated Surface Sites
Moon, Sang-Chul,Hieida, Takeshi,Yamashita, Hiromi,Anpo, Masakazu
, p. 447 - 448 (1995)
The photocatalyzed isomerization of cis-2-butene has been investigated on active ZrO2 catalysts which exhibited a typical photoluminescence associated with low coordinated surface sites.A geometrical isomerization reaction occurred predominantly and with high efficiency under UV-irradiation of the ZrO2 catalyst in the presence of cis-2-butene.A good parallel between the photoluminescence intensity and the rate of photocatalytic activity clearly indicated that the low coordinated surface sites play a significant role in the photocatalytic isomerization of cis-2-butene on the active ZrO2 catalysts.
The Isomerization of cis-2-Butene over SO2-adsorbing Mg(OH)2 and MgO
Otsuka, Kiyoshi,Tanaka, Kimiaki,Morikawa, Akira
, p. 310 - 314 (1980)
The reaction of butenes caused by the surface compounds formed from SO2 on Mg(OH)2 or MgO has been studied.It has been shown that the cis-trans isomerizatin of 2-butene is selectively induced by the sulfur compounds.This specific isomerization has been explained by the previously proposed mechanism that the reaction is accompanied by the copolymerization of 2-butene and SO2.The infrared spectroscopic study on the sulfur compounds formed on Mg(OH)2 or on MgO has demonstrated the presence of SO32-, SO42-, or sulfinato complexes.The formation of these surface species may cause strong electrostatic field on the surface, resulting in the polarization of reactant molecules, which is necessary for the initiation of the copolymerization or of the cis-trans isomerization.It has been shown, however, that the presence of weakly adsorbed SO2 is essential for determining the catalytic activities of the solids in the SO2-induced isomerization.
Sulfide catalysis without coordinatively unsaturated sites: Hydrogenation, cis-trans isomerization, and H2/D2 scrambling over MoS2 and WS2
Drescher, Thomas,Niefind, Felix,Bensch, Wolfgang,Gruenert, Wolfgang
, p. 18896 - 18899 (2012)
Simple test reactions as ethene hydrogenation, 2-butene cis-trans isomerization and H2/D2 scrambling were shown to be catalyzed by MoS2 and WS2 in surface states which did not chemisorb oxygen and were, according to XPS analysis, saturated by sulfide species. This is a clear experimental disproof of classical concepts that require coordinative unsaturation for catalytic reactions to occur on such surfaces. It supports new concepts developed on model catalysts and by theoretical calculations so far, which have been in need of confirmation from real catalysis.
A Novel Metathesis Catalyst Consisting of Non-transition Elements. The Metathesis of Alkenes over Tetramethyltin/Dehydroxylated Alumina
Ahn, Ho-Geun,Yamamoto, Kei,Nakamura, Ryuichi,Niiyama, Hiroo
, p. 503 - 506 (1992)
Sn(CH3)4/Al2O3 prepared by the deposition of Sn(CH3)4 to alumina which was previously dehydroxylated by heating at 773-1223 K was found to be an active catalyst for the metathesis of alkenes.The catalytic activity greatly depended on the pretreatment temperature of the alumina and the amount of Sn(CH3)4 deposited.
PHOTOINDUCED METATHESIS REACTION OF C3H6 ON SUPPORTED MoO3 CATALYST
Anpo, Masakazu,Tanahashi, Ichiro,Kubokawa, Yutaka
, p. 2121 - 2128 (1982)
Ultraviolet irradiation of MoO3 supported on porous Vycor glass (PVG) in the presence of C3H4 has been found to induce the formation of approximately equimolar amounts of C2H4 and 2-C4H8 as well as a small amount of CH3CHO, suggesting that the metathesis reaction of C3H4 occurs.The dependence of the yields upon the excitation wavelenght is in good agreement with the excitation band of the phosphorescence of MoO3/PVG, wich arises from the charge-transfer transition .The quenching of the posphorescence of MoO3/PVG and the decrease in the yield of C3H4 metathesis on adding O2 and CO suggest that the photoinduced metathesis reaction is closely associated with the charge-transfer excited triplet state of MoO3/PVG.From these results, together with those of e.s.r. experiments reported previously, the mechanism of the photoinduced C3H4 metathesis, especially the primary process of metal-carbene formation, is discussed.
Photocatalyzed Isomerization of Butenes over Metal Sulfides. High Photocatalytic Activity and Its Origin
Kodama, Sukeya,Matsumoto, Atsushi,Kubokawa, Yutaka,Anpo, Masakazu
, p. 3765 - 3770 (1986)
Photocatalytic activity of CdS and ZnS for the cis-trans isomerization of 2-butene is much higher than that of TiO2 and ZnO, though the double bond shift isomerization to 1-butene hardly proceeds in contrast with the case of the oxides.The addition of O2 or NO molecules leads to the remarkable inhibition of photocatalyzed isomerization.From these results together with the ESR measurements before and after UV irradiation of the sulfide catalyst either in the presence or in the absence of butene, the following conclusions emerge: sulfur radicals such as Sn, which are produced by the hole trapping by lattice S2- ions and/or sulfur clusters existing in the catalyst inherently, play a significant role in the weakening of the C=C double bond of 2-butene via the interaction with the molecules; the stability of such sulfur radicals results in the much higher photocatalytic activity of CdS and ZnS catalysts as compared with that of metal oxide catalysts.
Tuning crystal phase of molybdenum carbide catalyst to induce the different selective hydrogenation performance
Ding, Ziluo,Hou, Ruijun,Sun, Kening,Xu, Yamei,Yang, Qiuchen
, (2021/12/04)
α-MoC, β-Mo2C, and MoC-Mo2C were synthesized and investigated in the selective hydrogenation of 1,3-butadiene to understand the effect of crystal phases. The catalysts were characterized by XRD, N2-physisorption, SEM, TEM, XPS and chemisorptions. The adsorption properties and electronic properties over MoC(001) and Mo2C(001) were investigated by DFT calculations. The catalysts were evaluated at low and high temperatures in a fixed-bed reactor. β-Mo2C exhibits high activity and low butenes selectivity, due to the high concentration of hydrogen at each active site as well as the stronger adsorption and higher capacity of alkene; MoC-Mo2C shows better stability due to synergetic effect. At high temperature, the reaction rate is more dependent on the PH2 than PC4H6. Increasing PH2 could promote the activity and reduce oligomers formation. β-Mo2C exhibits the best performance at high temperatures concerning its high activity and the inhibition of oligomerization. This work is valuable for the non-precious metal catalyst development.
Oxidative Addition of Aryl and Alkyl Halides to a Reduced Iron Pincer Complex
Rummelt, Stephan M.,Peterson, Paul O.,Zhong, Hongyu,Chirik, Paul J.
supporting information, p. 5928 - 5936 (2021/05/06)
The two-electron oxidative addition of aryl and alkyl halides to a reduced iron dinitrogen complex with a strong-field tridentate pincer ligand has been demonstrated. Addition of iodobenzene or bromobenzene to (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) resulted in rapid oxidative addition and formation of the diamagnetic, octahedral Fe(II) products (3,5-Me2MesCNC)Fe(Ph)(N2)(X), where X = I or Br. Competition experiments established the relative rate of oxidative addition of aryl halides as I > Br > Cl. A linear free energy of relative reaction rates of electronically differentiated aryl bromides (ρ = 1.5) was consistent with a concerted-type pathway. The oxidative addition of alkyl halides such as methyl-, isobutyl-, or neopentyl halides was also rapid at room temperature, but substrates with more accessible β-hydrogen positions (e.g., 1-bromobutane) underwent subsequent β-hydride elimination. Cyclization of an alkyl halide containing a radical clock and epimerization of neohexyl iodide-d2 upon oxidative addition to (3,5-Me2MesCNC)Fe(N2)2 are consistent with radical intermediates during C(sp3)-X bond cleavage. Importantly, while C(sp2)-X and C(sp3)-X oxidative addition produces net two-electron chemistry, the preferred pathway for obtaining the products is concerted and stepwise, respectively.
