1013-08-7Relevant articles and documents
Mesoporous zeolite-supported metal sulfide catalysts with high activities in the deep hydrogenation of phenanthrene
Fu, Wenqian,Zhang, Lei,Wu, Dongfang,Xiang, Mei,Zhuo, Qian,Huang, Kai,Tao, Zhongdong,Tang, Tiandi
, p. 423 - 433 (2015)
Developing highly active hydrogenation catalysts for deep aromatics saturation is of great importance in the production of ultraclean diesel fuel at a low cost. Toward this goal, we synthesized a mesoporous zeolite ZSM-5 (MZSM-5) that was cost-effective and available on a large scale, and used it as a support for the preparation of highly efficient metal sulfide catalysts (NiMoS/MZSM-5 and CoMoS/MZSM-5) for the deep hydrogenation of phenanthrene. The intrinsic activity of the NiMoS/MZSM-5 catalyst (7.4 × 10-4 mol kg-1 s-1) was much higher than that of the alumina-supported NiMo catalyst (NiMoS/γ-Al2O3, 4.8 × 10-4 mol kg-1 s-1), and the selectivity of the deep hydrogenation products over NiMoS/MZSM-5 (20.9%) was higher than for NiMoS/γ-Al2O3 (15.2%). Compared with γ-Al2O3, the relatively weak metal-support interaction could facilitate the formation of polymolybdates on MZSM-5. After sulfidation, the more multistacked MoS2 active phases were formed on the MZSM-5, enhancing the hydrogenation activity of the NiMoS/MZSM-5 catalyst.
Improving the selectivity in hydrocracking of phenanthrene over mesoporous Al-SBA-15 based Fe-W catalysts by enhancing mesoporosity and acidity
Restrepo-Garcia, Jonatan R.,Baldovino-Medrano, Víctor G.,Giraldo, Sonia A.
, p. 98 - 109 (2016)
Catalysts for heavy oil hydrocracking require an enhanced mesoporosity (higher pore diameters) and a moderate acidic function (mild acidity) to treat the bulky molecules present in this kind of feedstock and to yield middle distillates (MD). In this work, we have synthesized five different kinds of mesoporous silica based on SBA-15 by modifying some of the variables of their synthesis with the aim at enhancing mesoporosity. NH4F and 1,3,5-trimethylbenzene (TMB) were used to modify the mesostructured arrangement in SBA-15. TMB modified SBA-15 materials exhibited the highest textural properties (2.16 cm3 g-1 and 17 nm) in comparison to NH4F modified silica (1.90 cm3 g-1 and 10.8 nm) and pristine SBA-15 silica (1.03 cm3 g-1 and 12 nm). The acidity of the SBA-15 based materials was modified by a post-synthesis "grafting procedure" to Si/Al molar ratios of 10, 25, and 40. SBA-15 based materials modified with both Al and TMB were used as supports for Fe-W sulfides. These catalysts were tested in the hydrocracking of phenanthrene. In general, all of the catalysts supported on Al-SBA-15 based materials were selective to the ring opening reaction of phenanthrene in contrast to the results obtained over a commercial Ni-Mo/γ catalyst. Such trend was associated to the presence of Br?nsted acid sites on the surface of the Al modified supports as shown 27 Al MAS NMR analysis.
Acid-Catalyzed Skeletal Rearrangements in Arenes: Aryl versus Alkyl Ring Pirouettes in Anthracene and Phenanthrene
Skraba-Joiner, Sarah L.,Brulet, Jeffrey W.,Song, Min K.,Johnson, Richard P.
, p. 13076 - 13083 (2017)
In 1 M triflic acid/dichloroethane, anthracene is protonated at C9, and the resulting 9-anthracenium ion is easily observed by NMR at ambient temperature. When heated as a dilute solution in triflic acid/dichloroethane, anthracene undergoes conversion to phenanthrene as the major volatile product. Minor dihydro and tetrahydro products are also observed. MALDI analysis supports the simultaneous formation of oligomers, which represent 10-60% of the product. Phenanthrene is nearly inert to the same superacid conditions. DFT and CCSD(T)//DFT computational models were constructed for isomerization and automerization mechanisms. These reactions are believed to occur by cationic ring pirouettes which pass through spirocyclic intermediates. The direct aryl pirouette mechanism for anthracene has a predicted DFT barrier of 33.6 kcal/mol; this is too high to be consistent with experiment. The ensemble of experimental and computational models supports a multistep isomerization process, which proceeds by reduction to 1,2,3,4-tetrahydroanthracene, acid-catalyzed isomerization to 1,2,3,4-tetrahydrophenanthrene with a predicted DFT barrier of 19.7 kcal/mol, and then reoxidation to phenanthrene. By contrast, DFT computations support a direct pirouette mechanism for automerization of outer ring carbons in phenanthrene, a reaction demonstrated previously by Balaban through isotopic labeling.
Understanding Ni Promotion of MoS2/γ-Al2O3 and its Implications for the Hydrogenation of Phenanthrene
Schachtl, Eva,Zhong, Lei,Kondratieva, Elena,Hein, Jennifer,Gutiérrez, Oliver Y.,Jentys, Andreas,Lercher, Johannes A.
, p. 4118 - 4130 (2015)
The chemical composition and structure of NiMo sulfides supported on γ-Al2O3 and its properties for hydrogenation of polyaromatic compounds is explored. The presence of Ni favors the formation of disperse octahedrally coordinated Mo in the oxide precursors and facilitates its reduction during sulfidation. This decreases the particle size of MoS2 (measured by transmission electron microscopy) and increases the concentration of active sites up to a Ni/(Mo+Ni) atomic ratio of 0.33. At higher Ni loadings, the size of the MoS2 did not decrease further, although the concentration of adsorption sites and accessible Ni atoms decreased. This is attributed to the formation of NiSx clusters at the edges of MoS2. Nickel also interacts with the support, forming separated NiSx clusters, and is partially incorporated into the γ-Al2O3, forming a Ni-spinel. The hydrogenation of phenanthrene follows two pathways; by adding one or two H2 molecules, 9,10-dihydrophenanthrene or 1,2,3,4-tetrahydrophenanthrene are formed as primary products. Only symmetric hydrogenation, leading to 9,10-dihydrophenanthrene, was observed on unpromoted MoS2/γ-Al2O3. In contrast, symmetric and deep hydrogenation (leading to 9,10-dihydrophenanthrene and 1,2,3,4-tetrahydrophenanthrene, respectively) occur with similar selectivity on Ni-promoted MoS2/γ-Al2O3. The rates of both pathways increase linearly with the concentration of Ni atoms in the catalyst. The higher rates for symmetric hydrogenation are attributed to increasing concentrations of reactive species at the surface, and deep hydrogenation is concluded to be catalyzed by Ni at the edge of MoS2 slabs. Well, everybody knows that Ni is the word: In promoted MoS2/γ-Al2O3, Ni substitutes Mo at the perimeter of the MoS2 slabs, forming particles of Ni sulfides with varying sizes at the edges of MoS2 or on the support. The proportions of these species depend on the Ni content. Ni-substituted sites perform faster and deeper hydrogenation of phenanthrene than non-promoted sites.
Reductive hydrogenation of polycyclic aromatic hydrocarbons catalyzed by metalloporphyrins
Nelkenbaum, Elza,Dror, Ishai,Berkowitz, Brian
, p. 210 - 217 (2007)
The hydrogenation of polycyclic aromatic hydrocarbons (PAHs) (naphthalene, anthracene, and phenanthrene) catalyzed by metalloporphyrins based on cobalt, nickel or iron was studied in aqueous solutions at room temperature and ambient pressure. Nickel porphyrin (P1) activated by nanosized zero-valent iron (nano-ZVI) and cobalt porphyrins (P2) and (P4) activated by titanium(III) citrate as the electron donor were demonstrated to be promising catalysts for the reductive hydrogenation of PAHs. In particular, partially saturated di-, tetra-, and octahydrogenated products were obtained for anthracene or phenanthrene using a nickel porphyrin activated by nano-ZVI, while naphthalene was transformed to tetralin. Systems containing cobalt porphyrins activated by titanium(III) citrate exhibited a high selectivity and activity toward hydrogenation of anthracene, producing 9,10-dihydroanthracene. However, no formation of hydrogenated hydrocarbons was observed from naphthalene or phenanthrene using cobalt porphyrins.
Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
, p. 9102 - 9112 (2020)
Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
On the multifaceted roles of NiSx in hydrodearomatization reactions catalyzed by unsupported Ni-promoted MoS2
Ji, Yinjie,Lercher, Johannes A.,Shi, Hui,Vogelgsang, Ferdinand
, p. 212 - 223 (2020)
A series of unsupported Ni-Mo sulfide catalysts with varying Ni contents (0.13–0.72 molNi molNi+Mo-1) was post-synthetically treated with concentrated HCl to remove large crystallites of accessible NiSx. These sulfide particles inevitably form and grow at Ni concentrations required for the synthesis, but generally have very low activities. In all cases, Ni concentrations were greatly reduced by the HCl treatment. While this ‘leaching’ strategy successfully improved the reaction rates of high Ni-content (>0.4 molNi molmetal-1) catalysts for the hydrogenation of phenanthrene, modest to drastic decreases in catalytic rates (×0.1–0.8) were registered for catalysts with lower Ni concentrations. For the lowest Ni-loaded catalyst (0.05 molNi molmetal-1), HCl treatment caused a dramatic loss of specific surface area and catalytic activity by more than a factor of 6 and shifted the selectivity pattern to that of pure MoS2. These observations allow us to conclude that Ni atoms incorporated at the slab edges are inherently susceptible to HCl attack. NiSx, however, are the preferential sites at which HCl induces dissolution. Experiments with inter-particle mixtures and segregated beds of NiSx and MoS2 demonstrate that NiSx not only activates H2, but also acts as a reservoir to dynamically incorporate Ni in the MoS2 slabs at reaction conditions. These beneficial effects are reduced, as nickel sulfide particles become excessively abundant as typical for high Ni-content catalysts, for which edge substitution by Ni is near or at its maximum. The areal activity and concentration of chemisorbed nitric oxide (NO) are well correlated for the leached catalysts, with the exception of the lowest Ni-containing catalyst that has a low degree of Ni edge substitution (20% of total edge atoms) and predominantly unpromoted sites. This linear correlation shows that the Ni-promoted sites are more than five-fold as active as the unpromoted sites.
Mechanochemistry of some hydrocarbons
Field, Leslie D.,Sternhell, Sever,Wilton, Howard V.
, p. 4051 - 4062 (1997)
Aromatic hydrocarbons (biphenyl, naphthalene, anthracene and phenanthrene) were subjected to ball milling (SPEX 8000) with approximately ten-fold weight of inorganic materials (alumina or silica). After about 24 h ail of the hydrocarbons were converted largely to carbon (graphite), but at intermediate stages disproportionation products (tetralin, phenylcyclohexane, bicyclohexyl, 9,10-dihydroanthracene, 1,2,3,4-tetrahydroanthracene, 1,2,3,4,4a,9,9a,10-octahydroanthracene, 1,2,3,4,5,6,7,8-actahydroanthracene, 9,10-dihydrophenanthrene, 1,2,3,4-tetrahydrophenanthrene, 1,2,3,4,4a,9,9a,10-octahydrophenanthrene, 1,2,3,4,5,6,7,8-octahydrophenanthrene) were also obtained in significant yields.
Interaction between Aromatics and Zinc Chloride. III. The Dissociation of Triphenylmethane and 9,10-Dihydroanthracene into Ions.
Morita, Mikio,Hirosawa, Kunio,Sato, Toshio,Ouchi, Koji
, p. 540 - 544 (1981)
Triphenylmethane and 9,10-dihydroanthracene were found to produce colored complexes placed in contact with molten zinc chloride or with solid zinc chloride pulverized or supported on porous Vycor glass.The triphenylmethane complex gave the same electronic absorption spectrum as that of the triphenylmethyl cation generated by contact with silica-alumina and BF3 on silica.The 9,10-dihydroanthracene complex exhibited the same electronic absorption band as that of the 9-anthracenium ion produced by the reaction of anthracene with concd H2SO4.The reaction of the triphenylmethane complex with deuterium gas provided HD gas and (C6H5)3CD.Similarly, the 9,10-dihydroanthracene complex and deuterium gas produced HD gas and 9,10-dihydroanthracene-9-d.Furthemore, their colored complexes on the supported zinc chloride gave a very weak IR absorption band at about 1720 cm-1, which is interpreted as corresponding to the formation of a Zn-H bond.These observations led us to conclude that triphenylmethane and 9,10-dihydroanthracene dissociate into ions upon contact with zinc chloride: (C6H5)3CH+nZnCl2 (C6H5)3C+(ZnCl2)n-H + nZnCl2 =
Active Sites on Nickel-Promoted Transition-Metal Sulfides That Catalyze Hydrogenation of Aromatic Compounds
Luo, Wanqiu,Shi, Hui,Schachtl, Eva,Gutiérrez, Oliver Y.,Lercher, Johannes A.
, p. 14555 - 14559 (2018)
Hydrogenation on Mo and W sulfides occurs at the edges of the sulfide slabs. The rate of hydrogen addition is directly proportional to the concentration of sulfhydryl (SH) groups at the slab edge and the metal atom attached to it. Sulfhydryl groups vicinal to edge-incorporated Ni hydrogenate with much higher rates than SH close to Mo and W. Each subset of SH groups, however, exhibits nearly identical intrinsic activity and selectivity, independent of the sulfide composition. The higher activity of Ni-WS2 compared to Ni-MoS2 stems from a higher concentration of SH groups on the former sulfide associated with a higher tendency of its surface vacancies to react with H2.
