500-22-1Relevant articles and documents
V2O5/TiO2 Catalysts for the Vapor-Phase Oxidation of β-Picoline: Influence of the TiO2-Carrier
Heinz,Hoelderich,Krill,Boeck,Huthmacher
, p. 1 - 10 (2000)
The heterogeneously catalyzed vapor-phase oxidation of β-picoline to nicotinic acid over a series of V2O5/TiO2 was investigated. Characterizations of the catalysts were carried out using X-ray diffraction, temperature-programmed desorption, and N2-adsorption. It was found that the use of an anatase type of TiO2-carrier with a higher BET surface area enhances the activity of the V/Ti-oxide catalyst enormously. TiO2-materials with different BET surface areas (between 10 and 270 m2/g) were used. Since these different materials originate from different processes, namely, the chloride and the sulfate process, the influence of the sulfate content was investigated. Additionally, the use of different TiO2 crystalline structures (anatase vs rutile) was evaluated, and a sulfate-free TiO2-material was modified with sulfate and cerium oxide during vanadia impregnation. The results of these experiments verified that the sulfate content itself did not have a strong influence on the catalyst activity. XRD-characterization of the catalysts demonstrated that only the TiO2 and the V2O5 phase could be detected. This corresponds with other investigations in the literature and strengthens the assumption that there is a synergetic effect of a V2O5 layer supported by TiO2 as a catalyst carrier. Therefore the increase of the interface between these two crystalline phases is the determining factor to improve the catalyst's activity.
Selective photocatalytic oxidation of 3-pyridinemethanol on platinized acid/base modified TiO2
?etinkaya, S?d?ka,Augugliaro, Vincenzo,Garlisi, Corrado,Lewin, Erik,Palmisano, Giovanni,Sá, Jacinto,Yurdakal, Sedat
, p. 4549 - 4559 (2021)
TiO2catalysts, modified with acidic or alkaline solutions and then platinized, were used for the partial photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3under environmentally friendly conditions. The reaction took place in water under UVA light and air oxygen. Catalysts were characterized by TEM, photoluminescence, DRIFT-IR, Raman, DRS, XPS, and photocurrent measurements. The photocatalytic activity results show that Pt loading of untreated samples leads to a significant activity improvement (hence product yield) as much as acid and alkaline treatments do. Moreover, the alkaline treated TiO2samples exhibit a further increase in activity after loading with Pt. Pt acts as an electron scavenger promoting electron transfer from the TiO2conduction band, consequently boosting the photogenerated pair numbers available for the reactive process. Photocurrent measurements show that the TiO2photocatalysts' active sites increase significantly after platinization and alkaline/acid treatment. The treated and/or Pt loaded catalysts showed good thermal stability (at least up to 400 °C).
Degradation of quinoline by wet oxidation - Kinetic aspects and reaction mechanisms
Thomsen, Anne Belinda
, p. 136 - 146 (1998)
The high temperature, high pressure wet oxidation reaction of quinoline has been studied as a function of initial concentration, pH and temperature. At neutral to acidic pH, it is effective in the oxidation of quinoline at 240°C and above, whereas under alkaline conditions the reaction is markedly slowed down. The results indicate that the reaction is an auto-catalysed, free radical chain reaction transforming 99% of quinoline to other substances. Of the quinoline, 30-50% was oxidised to CO2 and H2O depending on the initial concentration. Wet oxidation of deuterium-labelled quinoline was used as a method for verifying and quantifying the reaction products. Fifteen reaction products were identified and quantitatively determined, accounting for 70% of the carbon present after treatment. Nicotinic acid was a main product, accounting for up to 35% of the parent substance. The formation of succinic acid is suggested to be a result of a coupling reaction of the acetic acid radical. A reaction mechanism is suggested for the degradation of quinoline; it involves hydroxyl radicals and the possible interaction with autoclave walls is discussed. The high temperature, high pressure wet oxidation reaction of quinoline has been studied as a function of initial concentration, pH and temperature. At neutral to acidic pH, it is effective in the oxidation of quinoline at 240°C and above, whereas under alkaline conditions the reaction is markedly slowed down. The results indicate that the reaction is an auto-catalysed, free radical chain reaction transforming 99% of quinoline to other substances. Of the quinoline, 30-50% was oxidised to CO2 and H2O depending on the initial concentration. Wet oxidation of deuterium-labelled quinoline was used as a method for verifying and quantifying the reaction products. Fifteen reaction products were identified and quantitatively determined, accounting for 70% of the carbon present after treatment. Nicotinic acid was a main product, accounting for up to 35% of the parent substance. The formation of succinic acid is suggested to be a result of a coupling reaction of the acetic acid radical. A reaction mechanism is suggested for the degradation of quinoline; it involves hydroxyl radicals and the possible interaction with autoclave walls is discussed.
Mild reductive deoximation with TiCl4/NaI reagent system
Balicki,Kaczmarek
, p. 1777 - 1782 (1991)
The application of the TiCl4/NaI reagent system in the reductive cleavage of oximes under mild conditions is reported.
3-picoline oxidation over monoclinic orthovanadate Cr0.5Al0.5VO4 catalysts
Zhaoxia, Song,Kadowaki, Eriko,Shishido, Tetsuya,Wang, Ye,Takehira, Katsuomi
, p. 754 - 755 (2001)
Monoclinic orthovanadate CrVO4-I was found to be active for the vapor phase oxidation of 3-picoline to nicotinic acid and was further activated by the solid solution formation with Al at the Cr site.
TiO2/graphene-like photocatalysts for selective oxidation of 3-pyridine-methanol to vitamin B3 under UV/solar simulated radiation in aqueous solution at room conditions: The effect of morphology on catalyst performances
Alfè, Michela,Spasiano, Danilo,Gargiulo, Valentina,Vitiello, Giuseppe,Capua, Roberto Di,Marotta, Raffaele
, p. 91 - 99 (2014)
Graphene-like layers, synthesized through a two-step oxidation/reduction wet treatment of a high surface carbon black, have been used to prepare composites with TiO2 nanoparticles by liquid phase deposition, followed by calcination at 200 °C. The photocatalytic activity of the TiO2/graphene-like composites has been tested for the selective conversion of 3-pyridine methanol to 3-pyridine carboxyaldehyde and nicotinic acid (vitamin B3), under de-aerated and UV/solar simulated conditions, in the presence of cupricions. Two different composite morphologies have been explored and a dependence of the photocatalytic activity has been assessed. An enhanced photocatalytic activity, with respect to the neat TiO2, has been observed and attributed to the broader variety of stable free-radical species generated, at a given photo-catalyst morphology, within the delocalized π-electron systems.
Micellar effects on kinetics and mechanism of Vilsmeier–Haack formylation and acetylation with Pyridines
Alyami, Bandar A.,Iqubal, S. M. Shakeel,Khan, Aejaz Abdullatif,Mohammed, Tasneem
, (2022/01/19)
An efficient preparation of Vilsmeier–Haack formylated and acetylated derivatives with pyridine and substituted pyridines has been developed by employing micelles as catalyst. Their kinetic study reveals a phenomenal rate enhancement in anionic SDS, cationic CTAB, and nonionic TX-100 micellar media. The Vilsmeier–Haack reaction follows second order kinetics. Piszkiewicz’s co-operativity model was used to interpret the results in micellar media. The observed activation parameters ΔH and ΔS values were calculated from Eyring’s plots. The main features of this study were easy process, mild reaction conditions and readily available reagents. Graphical abstract: [Figure not available: see fulltext.].
Partial photocatalytic oxidations of 3-pyridinemethanol and 3-picoline by TiO2 prepared in HCl, HNO3 and H2SO4 at different temperatures
?etinkaya, S?d?ka,Yurdakal, Sedat
, p. 237 - 247 (2020/12/13)
Home prepared TiO2 photocatalysts were prepared from TiCl4 precursor in the absence and presence of HCl (1?6 M), HNO3 (1 M) or H2SO4 (1 M) at room temperature (RT), 60 or 100 °C. The TiO2 catalysts were characterised by XRD, BET, SEM and TGA techniques. TiO2 catalyst could not form at low temperature (up to 60 °C) in the presence of H2SO4. Just rutile phase was obtained for all TiO2 samples prepared at RT and 60 °C in HCl or HNO3. At 100 °C mainly both brookite and rutile phases were obtained in the presence of HCl or HNO3, whilst mainly anatase phase appeared in the presence of H2SO4. Nanorod structured TiO2 was formed in the presence of 1 M HCl or HNO3 at RT and 60 °C. The prepared TiO2 catalysts were used for partial oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 in water under UVA irradiation. Moreover, photocatalytic oxidation of 3-picoline, precursor of 3-pyridinemethanol, was also performed, but much lower product selectivity values were obtained with respect to 3-pyridinemethanol oxidation. However, selective 3-picoline oxidation could be performed at pH 2 with low activity. Degussa P25 was used for comparison and almost all home prepared catalysts showed a higher selectivity, but they showed to be less active than Degussa P25. The high selectivity of the home prepared samples was not due to the type of TiO2 phase, but mainly to the hydrophilicity of the TiO2 surface which allowed desorption of valuable products instead of their over-oxidation.
A Magnetically Recyclable Palladium-Catalyzed Formylation of Aryl Iodides with Formic Acid as CO Source: A Practical Access to Aromatic Aldehydes
You, Shengyong,Zhang, Rongli,Cai, Mingzhong
, p. 1962 - 1970 (2021/01/25)
A magnetically recyclable palladium-catalyzed formylation of aryl iodides under CO gas-free conditions has been developed by using a bidentate phosphine ligand-modified magnetic nanoparticles-anchored- palladium(II) complex [2P-Fe 3O 4@SiO 2-Pd(OAc) 2] as catalyst, yielding a wide variety of aromatic aldehydes in moderate to excellent yields. Here, formic acid was employed as both the CO source and the hydrogen donor with iodine and PPh 3as the activators. This immobilized palladium catalyst can be obtained via a simple preparative procedure and can be facilely recovered simply by using an external magnetic field, and reused at least 9 times without any apparent loss of catalytic activity.
One-Pot Direct Oxidation of Primary Amines to Carboxylic Acids through Tandem ortho-Naphthoquinone-Catalyzed and TBHP-Promoted Oxidation Sequence
Kim, Hun Young,Oh, Kyungsoo,Si, Tengda
supporting information, p. 18150 - 18155 (2021/12/09)
Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper-containing amine oxidase (CuAO)-like o-NQ-catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)-like TBHP-mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP-mediated oxidation pathways of imines. The developed metal-free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application.
