592-43-8Relevant articles and documents
Strength of solid acids and acids in solution. Enhancement of acidity of centers on solid surfaces by anion stabilizing solvents and its consequence for catalysis
Fǎrca?iu, Dan,Ghenciu, Anca,Marino, Gaye,Rose, Kenneth D.
, p. 11826 - 11831 (1997)
A comparison of acidity of two solids, a poly(styrenesulfonic acid) (Amberlyst 15) and a perfluoroinated ion exchange polymer (Nafion-H, PFIEP) with the structurally related liquid acids methanesulfonic, sulfuric, and trifluoromethanesulfonic acid (TFMSA), was conducted with mesityl oxide as probe base (determination of the Δδ1 parameter) and for the fluorinated materials also with hexamethylbenzene as the probe base. It was found that Nafion-H is similar in strength to 85% sulfuric acid, whereas Ambelyst 15 is much weaker than 80% methanesulfonic acid or 60% sulfuric acid. Thus, the solids are much weaker acids than their liquid structural analogs. This seems to be a general property, because the rigidity of the solids prevents the acid groups/sites from cooperating in the transfer of a hydron, an essential feature in the manifestation of superacidity. The postulation of superacidity for a number of solid acids appears to have no basis in fact. On the other hand, the acidity of the groups/sites on the surface can be increased by the interaction with a nonbasic solvent, capable of forming strong hydrogen bonds with the anion of the site (anion-stabilizing solvent). The anion-stabilizing solvent generates a new liquid phase around the acid site; for appropriate structures of the solid acid and solvent this phase can be superacidic. The acidity-enhancing effect of the anion-stabilizing solvent was found to have an important effect in boosting the catalytic activity of the solid for carbocationic reactions. A comparison of acidity of two solids, a poly(styrenesulfonic acid) (Amberlyst 15) and a perfluoroinated ion exchange polymer (Nafion-H, PFIEP) with the structurally related liquid acids methanesulfonic, sulfuric, and trifluromethanesulfonic acid (TFMSA), was conducted with mesityl oxide as probe base (determination of the Δδ1 parameter) and for the fluorinated materials also with hexamethylbenzene as the probe base. It was found that Nafion-H is similar in strength to 85% sulfuric acid, whereas Amberlyst 15 is much weaker than 80% methanesulfonic acid or 60% sulfuric aicd. Thus, the solids are much weaker acids than their liquid structural analogs. This seems to be a general property, because the rigidity of the solids prevents the acid groups/sites from cooperating in the transfer of a hydron, an essential feature in the manifestation of superacidity. The postulation of superacidity for a number of solid acids appears to have no basis in fact. On the other hand, the acidity of the groups/sites on the surface can be increased by the interaction with a nonbasic solvent, capable of forming strong hydrogen bonds with the anion of the site (anion-stabilizing solvent). The anion-stabilizing solvent generates a new liquid phase around the acid site; for appropriate structures of the solid acid and solvent this phase can be superacidic. The acidity-enhancing effect of the anion-stabilizing solvent was found to have an important effect in boosting the catalytic activity of the solid for carbocationic reactions.
Isomerization of olefins in a two-phase system by homogeneous water-soluble nickel complexes
Bricout, Herve,Mortreux, Andre,Monflier, Eric
, p. 469 - 471 (1998)
The first example of nickel catalyzed isomerization of olefins in a two-phase system is reported. Provided that the water-soluble ligand is properly tailored and that the Broensted acid is suitably selected, the catalytic system appears relatively stable and high catalytic activity can be reached.
1-hexene oligomerization by fluorinated tin dioxide
Yurkova,Lermontov,Malkova,Baranchikov,Ivanov
, p. 479 - 481 (2014)
Fluorinated tin dioxide has been shown to exhibit catalytic activity for 1-hexene oligomerization. The physicochemical and functional properties of nanocrystalline fluorinated SnO2 have been studied.
Effect of trimethylaluminum on the formation of active sites of the catalytic system bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6- tetrafluoroanilinato]titanium(IV) dichloride - MAO and catalytic isomerization of hex-1-ene
Bravaya,Faingol'd,Babkina,Petrova,Makhaev,Gagieva,Tuskaev,Bulychev
, p. 1461 - 1468 (2011)
The transformations of bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6- tetrafluoroanilinato]-titanium(IV) dichloride (L2TiCl2) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe3) and MAO free of AlMe3 (the so called "dry" MAO) were used. The catalytic transformations of hex-1-ene involving the systems L2TiCl2 - MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under the action of AlMe3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe3 to form LAlMe2. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe 3 is suppressed. The titanium complex activated by "dry" MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts of TMA (commercial MAO), this reaction does not take place.
PH control of the structure, composition, and catalytic activity of sulfated zirconia
Ivanov, Vladimir K.,Baranchikov, Alexander Ye.,Kopitsa, Gennady P.,Lermontov, Sergey A.,Yurkova, Lyudmila L.,Gubanova, Nadezhda N.,Ivanova, Olga S.,Lermontov, Anatoly S.,Rumyantseva, Marina N.,Vasilyeva, Larisa P.,Sharp, Melissa,Pranzas, P. Klaus,Tretyakov, Yuri D.
, p. 496 - 505 (2013)
We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to ～2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to ～80 m 2/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions.
Switching the Reactivity of Palladium Diimines with “Ancillary” Ligand to Select between Olefin Polymerization, Branching Regulation, or Olefin Isomerization
Jones, Glen R.,Basbug Alhan, Hatice E.,Karas, Lucas J.,Wu, Judy I.,Harth, Eva
supporting information, p. 1635 - 1640 (2020/11/30)
Coordinating solvents are commonly employed as ancillary ligands to stabilize late transition metal complexes and are conventionally considered to have little effect on the reaction products. Our work identifies that the presence of ancillary ligand in Pd-diimine catalyzed polymerizations of α-olefins can drastically alter reactivity. The addition of different amounts of acetonitrile allows for switching between distinct reaction modes: isomerization–polymerization with high branching (0 equiv.), regular chain-walking polymerization (1 equiv.), and alkene isomerization with no polymerization (>20 equiv.). Optimization of the isomerization reaction mode led to a general set of conditions to switch a wide variety of diimine complexes into efficient alkene isomerization catalysts, with catalyst loading as low as 0.005 mol %.
Controlling the performance of a silver co-catalyst by a palladium core in TiO2-photocatalyzed alkyne semihydrogenation and H2 production
Fudo, Eri,Imai, Shota,Kojima, Yasumi,Kominami, Hiroshi,Tanaka, Atsuhiro
, (2021/08/24)
Titanium (IV) oxide (TiO2) having palladium (Pd) core-silver (Ag) shell nanoparticles (Pd@Ag/TiO2) was prepared by using a two-step (Pd first and then Ag) photodeposition method. The core-shell structure of the nanoparticles having various Ag contents (shell thicknesses) and the electron states of Pd and Ag were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd core and the Ag shell was evaluated by hydrogenation of 4-octyne in alcohol suspensions of a photocatalyst under argon and light irradiation. 4-Octyne was fully hydrogenated to 4-octane over Pd/TiO2, whereas 4-octyne was selectively hydrogenated to cis-4-octene over Pd(0.2)@Ag(0.5)/TiO2. Further increase in the Ag content resulted in a decrease in the conversion of 4-octyne. Pd-free Ag/TiO2 was inactive for hydrogenation of alkyne and induced coupling of active hydrogen species (H2 production). Photocatalytic reactions at various temperatures revealed that the change in selectivity (semihydrogenation or H2 production) can be explained by the difference in values of activation energy of the two reactions. An applicability test showed that the Pd@Ag/TiO2 photocatalyst can be used for hydrogenation of various alkynes to alkenes.
