25067-06-5Relevant articles and documents
Hierarchically micro-/mesoporous Pt/KL for alkane aromatization: Synergistic combination of high catalytic activity and suppressed hydrogenolysis
Lee, Kyungho,Choi, Minkee
, p. 66 - 75 (2016)
Pt/KL is a highly active and selective monofunctional catalyst for aromatization of n-alkanes due to its 1-dimensionally connected cage-like micropores. The unique micropore structure of the KL zeolite, however, can also inhibit the diffusion of bulky aromatic products out of the catalyst, which can cause unwanted side reactions that can decrease the aromatic yields. In this work, we investigated the effect of secondary mesoporosity, which can substantially facilitate molecular diffusion in Pt/KL during C6-C8 alkane aromatizations. The results showed that the hierarchically micro-/mesoporous Pt/KL synthesized with a subsequent dealumination/desilication method exhibited enhanced aromatic yields, compared with a conventional Pt/KL. In particular, in C7 and C8 aromatizations, the hierarchical Pt/KL showed substantially less formation of dealkylated aromatic products than the Pt/KL due to suppressed secondary hydrogenolysis. Pt supported on a solely mesoporous γ-Al2O3 also showed significantly suppressed secondary hydrogenolysis (dealkylation), which indicates that fast diffusion of alkylated aromatics out of the catalyst structure is important for suppressing the secondary hydrogenolysis. However, the solely mesoporous Pt/γ-Al2O3 showed markedly lower aromatization activities than the KL-supported catalysts, which indicates that Pt located inside the zeolite micropores is crucial for obtaining high catalytic activity due to the preorganization of n-alkanes in the micropores. The present results showed that the hierarchical Pt/KL provides the synergistically combined benefits of the Pt/KL and the mesoporous Pt catalyst, namely high aromatization activity and suppressed secondary hydrogenolysis, respectively.
Mechanism of Coenzyme-B12-dependent Molecular Rearrangements. Evidence for a Radical-like Process in a Model Reaction for Methylmalonyl-CoA Mutase
Scott, A. Ian,Hansen, John B.,Chung, Sung-Kee
, p. 388 - 389 (1980)
Mechanistic probes of a model system for the coenzyme-B12-dependent methylmalonyl-CoA mutase reaction have suggested (i) that the C-Co bond in the alkylcobalamin intermediate is capable of both carbanionic and homolytic cleavage, and (ii) that the skeletal rearrangement most probably takes place at the radical stage.
Ethylene trimerization with a half-sandwich titanium complex bearing a pendant thienyl group
Huang, Jiling,Wu, Tianzhi,Qian, Yanlong
, p. 2816 - 2817 (2003)
A half-sandwich titanium complex with a pendant thienyl group, activated by methylalumoxane (MAO), can trimerize ethylene to 1-hexene with considerable activity and high selectivity; the coodination of the sulfur atom to the titanium center is proposed to be responsible for the selective trimerization of ethylene.
Photooxidation of n-octanal in air: Experimental and theoretical study
Tadic, Jovan M.,Xu, Lai,Houk,Moortgat, Geert K.
, p. 1614 - 1620 (2011)
Dilute mixtures of n-octanal in synthetic air (up to 100 ppm) were photolyzed with fluorescent UV lamps (275-380 nm) at 298 K. The main photooxidation products were 1-hexene, CO, vinyl alcohol, and acetaldehyde. The photolysis rates and the absolute quantum yields were found to be slightly dependent on the total pressure. At 100 Torr,φ100 ± 0.41(0.06, whereas at 700 Torr the total quantum yield was φ700 ± 0.32 ( 0.02. Two decomposition channels were identified: the radical channel C 7H15CHO → C7H15 + HCO and the molecular channel C7H15CHO → C6H 12 + CH2dCHOH, having absolute quantum yields of 0.022 and 0.108 at 700 Torr. The product CH2dCHOH tautomerizes to acetaldehyde. Carbon balance data lower than unities suggest the existence of unidentified decomposition channel(s) which substantially contributes to the photolysis. On the basis of experimental and theoretical evidence, n-octanal photolysis predominantly proceeds to form Norrish type II products as the major ones.
Trimerization of ethylene to 1-hexene with titanium complexes bearing phenoxy-imine ligands with pendant donors combined with MAO
Suzuki, Yasuhiko,Kinoshita, Shinsuke,Shibahara, Atsushi,Ishii, Seiichi,Kawamura, Kazumori,Inoue, Yoshihisa,Fujita, Terunori
, p. 2394 - 2396 (2010)
New Ti complexes bearing phenoxy-imine ligands with pendant aryl-OMe donors have been developed for ethylene trimerization to produce 1-hexene. These Ti complexes combined with methylaluminoxane selectively trimerize ethylene to form 1-hexene with exceptionally high activity (e.g., 6.59 tons of 1-hexene/((g of Ti) h)).
Propylene dimerization in the presence of nickel hydride complexes formed in situ
Shmidt,Titova,Belykh,Gomboogiin
, p. 205 - 213 (2010)
We study the influence of nickel hydride complexes formed in situ by reaction nickel(0) complexes having phosphorus-containing ligands with Broensted acids in the presence of various modifiers on a catalyst turnover and selectivity in propylene dimerization. The activating action of boron trifluoride etherate is considered. Pleiades Publishing, Ltd., 2010.
Mechanistic studies of the free-radical fragmentation of monoalkyl diazenes
Myers, Andrew G.,Movassaghi, Mohammad,Zheng, Bin
, p. 6569 - 6572 (1997)
Mechanistic studies of the deoxygenation of primary alcohols by Mitsumobu displacement with o-nitrobenzenesulfonylhydrazine (NBSH) reveal that the monoalkyl diazene intermediates formed in this process are exceedingly good hydrogen-atom donors toward alkyl radicals, exceeding tri-n-butylin hydride in reactivity. Competition experiments are described wherein the radical intermediates are trapped by intra- and intermediate addition to carbon-carbon double bonds, to dioxygen, and to the free radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO).
Synthesis and optimization of ethylene trimerization using [Bis-(2-dodecylsulfanyl-ethyl)-amine]CrCl3 catalyst
Mohamadnia, Zahra,Ahmadi, Ebrahim,Haghighi, Mehdi Nekoomanesh,Salehi-Mobarakeh, Hamid
, p. 474 - 480 (2011)
The bis-(2-dodecylsulfanyl-ethyl)-amine (SNS) ligand was prepared in good yield and high purity using inexpensive reagents and reacted with CrCl 3(THF)3 at room temperature to give the corresponding SNS/CrCl3 catalyst in high yield. An ethylene trimerization reaction at 90 °C and 23 bar ethylene, using the SNS/CrCl3 complex activated by 700 equivalents of MAO, afforded 99.97% 1-C6. Only 0.10% PE was produced and the catalyst activity was 159283 g/g Cr/h.
The Effect of Aromatic Ethers on the Trimerisation of Ethylene using a Chromium Catalyst and Aryloxy Ligands
Morgan, David H.,Schwikkard, Sianne L.,Dixon, John T.,Nair, Jerald J.,Hunter, Roger
, p. 939 - 942 (2003)
A catalyst system consisting of a chromium source, a 2,6-disubstituted phenol and an aromatic ether solvent, on activation with triethylaluminium, is active and selective for the trimerisation of ethylene to form 1-hexene. The aromatic ether appears to play a role as both solvent and reagent and is pivotal in ensuring both the good activity of the system as well as selectivity to the desired product, 1-hexene.
Ethylene oligomerization on the chromium ethylhexanoate-triethylaluminum-2, 5-dimethylpyrrol catalytic system in the presence of carbon tetrachloride
Khasbiullin,Belov,Kharlampidi,Vil'Ms
, p. 442 - 447 (2011)
The kinetics of the selective ethylene oligomerization reaction on the chromium(III) ethylhex-anoate-Al(C2H5)3-2,5- dimethylpyrrol homogeneous catalytic system in the presence of CCl4 has been studied. The reaction rate order in ethylene, the activation energy, and the selectivity of reaction for 1-hexene have been determined. Pleiades Publishing, Ltd., 2011.
