Selective Oxidation Of Toluene Research Articles

Solvent-Free Selective Oxidation of Toluene with O2 Catalyzed by Metal Cation Modified LDHs and Mixed Oxides

A series of metal cation modified layered-double hydroxides (LDHs) and mixed oxides were prepared and used to be the selective oxidation of toluene with O2. The results revealed that the modified LDHs exhibited much higher catalytic performance than their parent LDH and the modified mixed oxides. Moreover, the metal cations were also found to play important roles in the catalytic performance and stabilities of modified catalysts. Under the optimal reaction conditions, the highest toluene conversion reached 8.7% with 97.5% of the selectivity to benzyldehyde; moreover, the catalytic performance remained after nine catalytic runs. In addition, the reaction probably involved a free-radical mechanism.

Mesoporous carbon-supported cobalt catalyst for selective oxidation of toluene and degradation of water contaminants

Mesoporous carbon-supported cobalt (Co-MC) catalysts are widely applied as electrode materials for batteries. Conversely, the development of Co-MC as bifunctional catalysts for application in organic catalytic reactions and degradation of water contaminants is slower. Herein, the catalyst displayed high activity in the selective oxidation of toluene to benzaldehyde under mild conditions, attaining a high selectivity of 92.3%. Factors influencing the catalytic reaction performance were also investigated. Additionally, Co-MC displayed remarkable catalytic activity in degrading dyes relative to the pure metal counterpart. Moreover, the catalyst exhibited excellent reusability, as determined by the cyclic catalytic experiments. The paper demonstrates the potential of Co-MC as a bifunctional catalyst for both toluene selective oxidation and water contaminant degradation.

A New Method for Immobilization of NDHPI on SBA-15 Carrier Used as Catalyst for Selective Oxidation of Toluene

Mesoporous molecular sieve SBA-15 immobilized N,N-dihydroxypyromellitimide (NDHPI) was prepared by a new method, which was realized through the coupling NDHPI with pre-grafted glycidoxypropyl chains of glycidoxypropyl-SBA-15. SBA-15 immobilized N-hydroxyphthalimide (NHPI) by impregnation method was also prepared for comparison. The two catalysts were characterized by Fourier transform infrared spectroscopy, N2 adsorption–desorption technique, thermogravimetric analyses, X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. Then the catalysts and N,N-bis(salicylidene) ethylenediiminocobalt (Cosalen) complex were used into oxidation of toluene with molecular oxygen. The more active and reusable catalyst was the immobilized one coupled by NDHPI with glycidoxypropyl-SBA-15, which improved the total selectivity of benzaldehyde and benzyl alcohol to 46.0 % with the conversion of toluene 14.8 % at 90 °C for 7 h. Mesoporous molecular sieve SBA-15 immobilized N,N-dihydroxypyromellitimide (NDHPI) was prepared by a new method, which was realized through the coupling NDHPI with pre-grafted glycidoxypropyl chains of glycidoxypropyl-SBA-15. SBA-15 immobilized NHPI by impregnation method was also prepared for comparison. Their structure was characterized and their catalytic performance combined with Cosalen complex in the molecule oxidation of toluene were compared. Their reusability performance was also discussed.

Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde.

A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

Solvent-free selective oxidation of toluene by oxygen over MnOx/SBA-15 catalysts: Relationship between catalytic behavior and surface structure

MnOx/SBA-15 catalysts with different manganese content were studied for the selective oxidation of toluene by oxygen under solvent-free conditions. The catalyst with a manganese content of 6wt% shows high catalytic efficiency and benzoic acid selectivity, whereas the selectivity to benzaldehyde increases remarkably upon increasing manganese content to 17wt%. Several techniques such as N2-physisorption, X-ray diffraction, diffuse reflectance spectra, X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy were used to characterize the catalysts. Toluene adsorption investigations over catalysts reveal that the 6wt% MnOx/SBA-15 catalyst has better adsorption capacity. The structure-performance correlation suggests that the well-isolated manganese species with tetrahedral coordination and greater numbers of adsorption sites account for the efficient oxidation of toluene to benzoic acid, whereas the MnOx clusters are less active and depress further oxidation to benzaldehyde and benzoic acid formation. Additionally, reaction temperature, time, catalyst mass, pressure and catalyst reusability were investigated over 6wt% MnOx/SBA-15. A calculated turnover frequency of 532h−1 was obtained in 1h at 180°C. Rate-retarding effects of inhibitors and oxidation took place even without catalyst at 300°C, respectively, indicate a radical chain mechanism.

Synthesis of hierarchical ZSM-5 hexagonal cubes and their catalytic activity in the solvent-free selective oxidation of toluene

In the present work, ZSM-5 with hexagonal cubic morphology was successfully synthesized by the hydrothermal method in the presence of tetrapropylammonium hydroxide and nonionic surfactant as mesopore template. The structural, textural, morphological and thermal properties of the as-synthesized zeolite samples were evaluated by XRD, XRF, FT-IR, N2 adsorption, HR-TEM, HR-SEM and TGA. The powder X-ray diffraction and FT-IR analysis confirms the formation of pure ZSM-5 zeolite without any impurities present. The surface area analysis showed that the mesoporous surface area was evidently increased without intensively destroying the microporosity in the surfactant-assisted zeolite. The catalytic performance of the ZSM-5 zeolites was evaluated in the liquid phase selective oxidation of toluene using tert-butyl hydroperoxide as an oxidant. The surfactant-assisted ZSM-5 shows a higher toluene conversion and benzaldehyde selectivity at optimum conditions.

Selective oxidation of toluene to benzaldehyde in liquid phase over CoAl oxides prepared from hydrotalcite-like precursors

CoAl oxides were prepared from the calcination of CoAl layered double hydroxides (LDHs, Co/Al = 2, 3 and 4) and applied to the selective oxidation of toluene to benzaldehyde using tert-butylhydroperoxide as the oxidant. These samples were characterized by XRD, SEM, BET, DR-UV–Vis, XPS, FTIR and CO2-TPD techniques to explain their catalytic properties. The influence of various reaction parameters, such as reaction temperature, reaction time, content of catalyst, substrate/oxidant mole ratio and nature of solvent on the activity and selectivity of aldehyde was evaluated. Co4Al oxide showed a maximum conversion of toluene of 8.2 % with 77.6 % selectivity towards benzaldehyde under the optimized conditions. The moderate basic sites on the CoAl oxides and the increased Co3O4 content may be responsible for the catalytic activity and selectivity. Repeated runs showed that the catalyst was stable for at least five cycles without obvious changes of catalytic activity and selectivity.

Ag–Cu–BTC prepared by postsynthetic exchange as effective catalyst for selective oxidation of toluene to benzaldehyde

A mixed-node MOF catalyst Ag–Cu–BTC was prepared by postsynthetic exchange (PSE) method. It is believed that PSE method can realize isomorphous replacement of Ag ion to framework Cu ion in Cu–BTC successfully. The catalytic performance of Ag–Cu–BTC was investigated via selective oxidation of toluene to benzaldehyde by molecular oxygen in the absence of solvent and initiator. This catalyst exhibits good catalytic performance: on the premise of keeping highly selective catalysis of Cu–BTC for toluene oxidizing to benzaldehyde, the introduction of Ag (Ag content is 2.76wt.%) can promote toluene conversion from 6.5% to 12.7%.

Preparation of silver–tungsten nanostructure materials for selective oxidation of toluene to benzaldehyde with hydrogen peroxide

We have developed a facile one-pot synthetic strategy to prepare Ag/WO3 nanostructure materials with different morphologies using a cationic surfactant, cetyltrimethylammonium bromide. These materials were employed as catalysts in the direct synthesis of toluene to benzaldehyde using H2O2. The morphology of the Ag/WO3 materials can be varied by changing the synthesis parameters. The size and shape of the Ag/WO3 nanostructure catalyst has direct influence on the toluene conversion and benzaldehyde selectivity. The effect of different reaction parameters like reaction temperature, H2O2 to toluene molar ratio, reaction time, and so forth have been studied in detail. The Ag/WO3 catalyst with ∼7 nm silver nanoparticles on the WO3 nanorod with a diameter ∼60 nm showed the best catalytic activity of 42% toluene conversion with 93% benzaldehyde selectivity. The catalyst did not show any leaching up to four reuses, showing the true heterogeneity of the catalyst.

Selective Oxidation of Toluene to Benzaldehyde Catalyzed by Co/Al Hydrotalcite-like Materials in Liquid Phase

Selective Oxidation of Toluene to Benzaldehyde Catalyzed by Co/Al Hydrotalcite-like Materials in Liquid Phase

Fly ash supported vanadia catalyst: An efficient catalyst for vapor phase partial oxidation of toluene in a micro-reactor

Synthesis of a highly active solid oxidative catalyst has been reported by loading of vanadium on mechanically activated fly ash through wet impregnation method. The catalytic activity of prepared catalyst was measured by gas phase, solvent free selective oxidation of toluene using molecular oxygen as oxidant in a vapor phase micro-reactor under normal atmospheric pressure. The effects of vanadium weight fractions (3, 8 and 15wt.%) and reaction temperature (453–553K) on catalytic activity were investigated. The prepared catalysts were characterized by XRF, BET surface area analyzer, XRD, FTIR, pyridine adsorbed FTIR, Diffuse reflectance UV–vis and SEM techniques. Monolayer vanadia species (monomeric and polymeric) are responsible for the catalytic activity and selectivity of benzaldehyde and benzoic acid. Therefore, an increase of the vanadium concentration in the catalysts above the monolayer coverage results in the decrease of conversion and selectivity in toluene oxidation due to the partial blockage of active monolayer species by crystalline V2O5 species. The specific surface area, surface roughness and activity of fly ash were increased by mechanical activation which is being used as an effective support comparable to other silica materials. Thus the overall process is a novel, efficient and promising pathway of cost effective heterogeneous oxidations.

Preparation of the CuCr2O4 spinel nanoparticles catalyst for selective oxidation of toluene to benzaldehyde

CuCr2O4 spinel nanoparticles with size between 30-60 nm were prepared by a hydrothermal synthesis method in the presence of a surfactant, cetyltrimethylammonium bromide.

Selective oxidation of toluene using Ag nanoparticles self-supported on Ag2V4O11 nanobelts

Ag nanoparticles self-supported on Ag2V4O11 nanobelts (Ag/Ag2V4O11 NBs) are synthesized using a sonochemical–hydrothermal method. Ag/Ag2V4O11 NBs are studied by characterization of powder X-ray diffraction, N2 adsorption, transmission electron microscopy, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performances of the as-prepared materials were carefully investigated in gas phase selective oxidation of toluene. Higher catalytic activity and better selectivity to benzaldehyde and benzoic acid are achieved by this belt-like Ag/Ag2V4O11 nanocomposite in gas phase oxidation of toluene in comparison with those of bulk V2O5 and Ag supported on V2O5 nanobelts (Ag/V2O5 NBs). The superior catalytic performance of Ag/Ag2V4O11 NBs was attributed to its unique redox property as well as the synergistic effect between Ag nanoparticles and Ag2V4O11.

전이금속을 함침한 γ-Al2O3촉매의 Toluene 분해

Alumina-supported catalysts containing different transition metals such as Cu, Cr, Mn, Zn, Co, W were investigated for their activity in the selective oxidation of toluene. Catalytic oxidation of toluene was investigated at atmospheric pressure in a fixed bed flow reactor system over transition metals with <TEX>$Al_2O_3$</TEX> catalyst. The result showed the order of catalytic activities for the complete oxidation of toluene was Mn > Cu> Cr> Co> W> Zn for 5wt.% transition <TEX>$metals/Al_2O_3$</TEX>. <TEX>$Mn/Al_2O_3$</TEX> catalysts containing different amount of Mn were characterized by X-ray diffraction spectroscopy for decision of loading amount of metal to alumina. 5 wt.%<TEX>$Mn/Al_2O_3$</TEX> catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of <TEX>$289^{\circ}C$</TEX>.

Selective oxidation of toluene using surface-modified vanadium oxide nanobelts

Vanadium oxide nanobelts were synthesized using a sonochemical-hydrothermal method. Hexadecylphosphonic acid (HDPA) was introduced onto the surfaces of the nanobelts and bulk vanadium oxide to tune their catalytic properties; these properties were tested using gas-phase oxidation of toluene. The catalytic activity of the vanadium oxide nanobelts was higher than that of the bulk oxide as a result of the higher lattice oxygen activity of the nanobelts. Doping with HDPA, tuning the lattice oxygen activity, and blocking unselective sites led to both higher activity and selectivities for benzaldehyde and benzoic acid on nanobelt-like vanadium oxides, whereas led to lower activity but higher selectivities for benzaldehyde and benzoic acid on bulk vanadium oxides. Vanadium oxide nanobelts are more active, but less selective, in toluene oxidation than bulk vanadium oxide is. Significant modification of the selective oxidation of toluene on vanadium oxide nanobelts is achieved by doping with hexadecylphosphonic acid.

Solvent-free oxidation of toluene in an ionic liquid with H2O2 as oxidant

A series of 1-alkyl (or acetic acid)-3-methylimidazolium–metal chloride ionic liquids such as AmimBr Cl-,BF4-–MClx (A=ethyl, butyl, acetic acid and benzyl radicals; M=Fe, Cu, Sn, Mn, Ni, Co and Zn; x=2, 3 and 4) and Et3NHCl–FeCl3 were prepared by conventional method. These prepared ionic liquids were used as catalysts in selective oxidation of toluene with H2O2 as an oxidant. Their catalytic activities were compared in the absence of organic solvents. The ionic liquid bmimBr–FeCl3 showed higher catalytic activity with 10.2% conversion and 99% selectivity to benzaldehyde and benzyl alcohol. However, the catalyst was easily recovered and reused for three times without evident activity loss.

Polymer-Supported Iron(III) Catalyst for the Selective Oxidation of Toluene

Polymer-Supported Iron(III) Catalyst for the Selective Oxidation of Toluene

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalyst for selective oxidation of toluene to benzoic acid with H2O2

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalysts were developed for the selective oxidation of toluene to benzoic acid in the presence of H2O2. The influence of the DVB content on the capacity of immobilized Fe(III) and on the catalytic activities of the polymeric complexes was investigated. The extent of Fe(III) uptake by the copolymers varied slightly with the concentration of DVB. The catalytic activities generally increase with increasing degree of crosslinker from 2 to 10% and decrease further with increasing the DVB content. Under the optimal conditions (80°C, 6h), the catalyst containing 10% DVB was found to be highly efficient in conversion of toluene to benzoic acid with 90% conversion and 96% selectivity.

Selective oxidation of toluene over the new catalyst cobalt tetra (4-hydroxyl) phenylporphyrin supported on zinc oxide

Abstract Cobalt tetra(4-hydroxyl)phenylporphyrin/ZnO was prepared and used for the catalytic oxidation of toluene with O2. Its activity has been increased by 70% over that of the cobalt tetra(4-hydroxyl)phenylporphyrin and the effective reuse of the supported catalyst for toluene oxidation is seven times per 1 mg (1.35 × 10−6 mol) cobalt tetra(4-hydroxyl)phenylporphyrin, demonstrating the promotion by zinc oxide.

A Complexation Promoted Organic N‐Hydroxy Catalytic System for Selective Oxidation of Toluene

AbstractComplexation was innovatively utilized to design a novel catalytic system for the selective oxidation of toluene, which runs contrary to the traditional definition of organic metal complex catalysis. In the present system, an N‐heteroaromatic ring‐containing N‐hydroxy compound acts as the catalytically active component. Through an electron‐withdrawing effect produced by the occurring complexation with proper metal salts, which was characterized by real‐time in situ Fourier transform infrared spectra, the activity of the organic molecule could be remarkably improved. The combination of copper(II) chloride with 6‐hydroxy‐pyrrolo[3,4‐b]pyrazine‐5,7‐dione showed the best activity, and an inert hydrocarbon such as toluene could be efficiently transformed with 70.9% conversion and 93.5% selectivity to benzoic acid at 90 °C within 2 h.