781-17-9Relevant articles and documents
Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst
Stegner, Philipp,F?rber, Christian,Zenneck, Ulrich,Knüpfer, Christian,Eyselein, Jonathan,Wiesinger, Michael,Harder, Sjoerd
supporting information, p. 4252 - 4258 (2020/12/22)
Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non-conjugated) mono-, di- and tri-substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.
Quenched skeletal Ni as the effective catalyst for selective partial hydrogenation of polycyclic aromatic hydrocarbons
Liu, Chengyun,Rong, Zeming,Sun, Zhuohua,Wang, Yong,Du, Wenqiang,Wang, Yue,Lu, Lianhai
, p. 23984 - 23988 (2013/11/19)
Quenched skeletal Ni is an active and selective catalyst for selective partial hydrogenation of polycyclic aromatic hydrocarbons (PAHs). The molecular structure of PAHs significantly dominate the hydrogenation process and furthermore, the distribution of hydrogenated products.
Facile sonochemical synthesis of carbon nanotube-supported bimetallic Pt-Rh nanoparticles for room temperature hydrogenation of arenes
Pan, Horng-Bin,Wai, Chien M.
scheme or table, p. 1649 - 1660 (2011/10/08)
Bimetallic Pt-Rh nanoparticles can be deposited uniformly on surfaces of carboxylate functionalized multi-walled carbon nanotubes (MWNTs) using a simple one-step sonochemical method. The bimetallic nanoparticle catalyst exhibits a strong synergistic effect relative to the individual Pt or Rh metal nanoparticles for catalytic hydrogenation of polycyclic aromatic hydrocarbons (PAHs), neat benzene and alkylbenzenes. Complete ring saturation of PAHs can be achieved using the bimetallic Pt-Rh/MWNTs catalyst at room temperature. This one-step synthesis technique provides a simple and rapid way of making highly active and recyclable CNT-supported monometallic and bimetallic nanocatalysts for low temperature hydrogenation reactions.
Hydrogenation of pyrene using Pd catalysts supported on tungstated metal oxides
Lin, Qiang,Shimizu, Ken-Ichi,Satsuma, Atsushi
experimental part, p. 166 - 172 (2011/06/21)
A series of Pd catalyst supported on tungstated metal oxides (Pd/W-MOx) were prepared and applied for pyrene hydrogenation, and the role of acid sites of supports was investigated. Among Pd/W-MOx catalysts, Pd/W-TiO2 showed the highest activity which was comparable to those of Pd/BEA, Pd/Y and Pd/SiO2-Al2O3. As for the Pd catalysts supported on metal oxides without tungstate (Pd/MOx), the hydrogenation activity became higher with the increase in the acid amount of supports measured by calorimetric measurement of ammonia adsorption. The important role of acid sites on hydrogenation activity was demonstrated. On the other hand, the hydrogenation activity of Pd/W-MOx catalysts was not correlated to the acid amount of supports measured by ammonia adsorption. On-site generation of protonic acid on tungstated metal oxide supports was estimated from kinetic analysis of reduced W species in the presence of hydrogen by in situ UV-visible measurement. From a good correlation between the kinetic parameters of on-site protonic acid formation and the hydrogenation activity, the important role of protonic acid formation on tungstated metal oxide supports was clarified.
Pyrene-dihydrophenazine bis(radical cation) in a singlet ground state
Suzuki, Shuichi,Takeda, Takuma,Kuratsu, Masato,Kozaki, Masatoshi,Sato, Kazunobu,Shiomi, Daisuke,Takui, Takeji,Okada, Keiji
supporting information; experimental part, p. 2816 - 2818 (2009/11/30)
A new pyrene-dihydrophenazine dyad was prepared. Oxidation of the neutral species produced a bis(radical cation) species, which was characterized by the absorptions of their component radical cations In the visible region. A thermally accessible triplet state was observed In the ESR measurement In frozen n-PrCN. The energy gap between the singlet and triplet states was determined to be 2J/kB = -36 ± 3 K.
1-, 2-, and 4-ethynylpyrenes in the structure of twisted intercalating nucleic acids: Structure, thermal stability, and fluorescence relationship
Filichev, Vyacheslav V.,Astakhova, Irina V.,Malakhov, Andrei D.,Korshun, Vladimir A.,Pedersen, Erik B.
experimental part, p. 9968 - 9980 (2009/10/14)
A postsynthetic, on-column Sonogashira reaction was applied on DNA molecules modified by 2- or 4-io-dophenylmethylglycerol in the middle of the sequence, to give the corresponding ortho- and para-twisted intercalating nucleic acids (TINA) with 1-, 2-, and 4-ethynylpyrene residues. The convenient synthesis of 2- and 4-ethynylpyrenes started from the hydrogenolysis of pyrene that has had the sulfur removed and separation of 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene, which were later converted to the final compounds by successive Friedel-Crafts acetylation, aromatization by 2,3-dichloro-5,6- dicyano-1,4-benzoquinone, and a Vilsmeier-Haack-Arnold transformation followed by a Bodendorf fragmentation. Significant alterations in thermal stability of parallel triplexes and antiparallel duplexes were observed upon changing the attachment of ethynylpyrenes from para to ortho in homopyrimidine TINAs. Thus, for para-TINAs the bulge insertion of an intercalator led to high thermal stability of Hoogsteen-type parallel triplexes and duplexes, whereas Watson-Crick-type duplexes were destabilized. In the case of ortho-TINA, both Hoogsteen and Watson-Crick-type complexeswere stabilized. Alterations in the thermal stability were highly influenced by the ethynylpyrene isomers used. This also led to TINAs with different changes in fluorescence spectra depending on the secondary structures formed. Stokes shift of approximately 100nm was detected for pyren-2-ylethynylphenyl derivatives, whereas values for 1- and 4-ethynylpyrenylphenyl conjugates were 10 and 40 nm, respectively. In contrast with paraTINAs, insertion of two ortho-TINAs opposite each other in the duplex as a pseudo-pair resulted in formation of an excimer band at 505 nm for both 1- and 4-ethynylpyrene analogues, which was also accompanied with higher thermal stability.
Good sulfur tolerance of a mesoporous Beta zeolite-supported palladium catalyst in the deep hydrogenation of aromatics
Tang, Tiandi,Yin, Chengyang,Wang, Lifeng,Ji, Yanyan,Xiao, Feng-Shou
scheme or table, p. 125 - 133 (2009/02/08)
The activities of a Pd catalyst supported on mesoporous Beta zeolite (Beta-H) were evaluated for the hydrogenation of naphthalene and pyrene in the absence and presence of 200-ppm sulfur and for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). Compared with Pd/Al-MCM-41, the Pd/Beta-H catalyst exhibited better sulfur tolerance for hydrogenation of naphthalene and pyrene and higher activity for HDS of 4,6-DMDBT. The ratio of the hydrogenation of the second ring naphthalene in the absence and presence of 200-ppm sulfur for Pd/Beta-H was larger than that for Pd/Al-MCM-41 (0.47 vs 0.19). The desulfurization effect of Pd/Beta-H was greater than that of Pd/Al-MCM-41 (51 vs 35%). The difference in sulfur tolerance and HDS ability of the 2 catalysts is attributed to the difference in support acidity. Beta-H exhibited more acidic sites and a higher percentage of strong acidic sites than Al-MCM-41 (552 μmol/g and 43% vs 291 μmol/g and 18%).
Characterization of polycyclic aromatic hydrocarbon particulate and gaseous emissions from polystyrene combustion
Durlak, Susan K.,Biswas, Pratim,Shi, Jichun,Bernhard, Mary Jo
, p. 2301 - 2307 (2007/10/03)
The partitioning of polycyclic aromatic hydrocarbons (PAHs) between the particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres (100-300 μm) at different combustion temperatures (800- 1200 °C) to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments (differential mobility particle sizer and/or optical particle counter) to determine the particle size distribution. For chemical composition analyses, the particles were either collected on Teflon filters or split into eight size fractions using a cascade impactor with filter media substrates, while the gaseous products were collected on XAD-2 adsorbent. Gas chromatography/mass spectroscopy (GC/MS) was used to identify and quantify the specific PAH species, their partitioning between the gas and particulate phases, and their distribution as a function of emission particle size. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes. The experimental results have been analyzed to elucidate the formation mechanisms of PAHs and particles during polystyrene combustion. The implications of these results are also discussed with respect to the control of PAH emissions from municipal waste-to-energy incineration systems. The partitioning of polycyclic aromatic hydrocarbons (PAHs) between particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments to determine the particle size distribution. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes.
Partial Hydrogenation of Polycyclic Aromatic Hydrocarbons by Electroreduction in Protic Solvents
Anowski,Voss
, p. 337 - 344 (2007/10/03)
Polycyclic aromatic hydrocarbons (PAH) such as anthracene (1), phenanthrene (5), acenaphthylene (15), pyrene (17), chrysene (22), and fluoranthene (28) are selectively hydrogenated upon electroreduction at a lead cathode in ethanolic solution. The degree of hydrogenation and the structure of the products depend on the reaction conditions, in particular on the applied reduction potential.
