Catalysts For Oxidation Of Styrene Research Articles

Preparation and characterization of nano MnO-CaLs as a green catalyst for oxidation of styrene.

Hydrophilic nano MnO is shown to have significant stability in aqueous media for oxidation of styrene. Different catalysts have been used to synthesis styrene oxide, but MnO-CaL is considered the efficient and selective catalyst to produce styrene oxide. In general, this paper reported especial strategy for synthesis of novel nano MnO that stabilized with oleic acid in chloroform and changing nature of its stabilizer by exchanging oleic acid with lignosulfunate and displays its catalytic activity towards selective oxidation of styrene. The catalyst has shown good selectivity in oxidation of styrene by changing temperature. Finding the optimal conditions for reaction and determining the best time and temperature for achieving the ideal product and reducing the side products are among the issues discussed in this article. MnO-CaLs leads to selective oxidation of styrene to styrene epoxide at low temperature. By increasing the temperatures, benzaldehyde and partially 2-phenyl acetaldehyde are also produced as by-products. Furthermore, the nano catalyst could be recycled several times without any clear changing in activity, which makes nano catalyst economic and environmentally friendly.

Catalytic oxidation of styrene by dinuclear Mn(III) coordination compound with asymmetric tridentate half-Salen type NNO-donor ligand

A new methoxo bridged dinuclear Mn(III) coordination compound, [Mn2(µ-OMe)2(L)2(MeOH)2]Cl2∙2MeOH (1), with tridentate N2O-donor half-Salen ligand was synthesized by the reaction of MnCl2·4H2O and (Z)-3-((2-aminocyclohexyl)amino)-1-phenylbut-2-en-1-one (HL) in methanol and characterized by spectroscopic methods and elemental analysis. The structure of compound 1 was also determined by single crystal X-ray diffraction studies which indicated it is a dinuclear Mn(III) coordination compound. Two Mn(III) are connected together by two methoxo bridges and have distorted octahedral geometry. The coordination compound is ionic and two chloride anions appear as the counter anions which are involved in strong hydrogen bond interactions. The catalytic activity of compound 1 was investigated in oxidation of styrene in the presence of hydrogen peroxide as a green oxidant. The effects of influencing parameters like molar ratio of the reagents, temperature and the presence of different solvents were investigated. The results of catalytic studies indicated the selectivity and activity of this catalytic system considerably depend on the reaction condition. Temperature and molar ratio of oxidant to substrate have high influence on both conversion and selectivity of the oxidation products. The best selectivity toward styrene epoxide was obtained at 40 °C and the best TOF was 66.4 h−1. The results indicate half-salen Mn(III) coordination compound can act as selective and efficient catalyst for oxidation of styrene under mild condition

Synthesis of a 2,4-DcCoPc/MIL-101(Fe) composite and catalytic oxidation of styrene to benzaldehyde

A new type of 2,4-DcCoPc/MIL-101(Fe) composite was synthesized by modifying MIL-101(Fe) with 2,4-dichlorophenoxy phthalocyanine cobalt (2,4-DcCoPc). X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), N2 physisorption measurements, scanning electron microscopy (SEM), transmittance scanning electron microscopy (TEM) and thermogravimetry analysis (TGA) characterize and analyze the composite material. Due to the excellent catalytic properties of MIL-101(Fe) and 2,4-DcCoPc, 2,4-DcCoPc/MIL-101(Fe) was used to catalyze the oxidation of styrene to benzaldehyde. Significantly, at the molar ratio of 0.24:1, 2,4-DcCoPc/MIL-101(Fe) achieved optimal catalytic performance with conversion rate of styrene at 88% and selectivity for benzaldehyde of 91%. Compared with 2,4-DcCoPc or MIL-101(Fe) alone, the catalytic performance was improved. The composite material can be used as a catalyst for oxidation of styrene to benzaldehyde.

From Core–Shell to Yolk–Shell: Improved Catalytic Performance toward CoFe2O4@ Hollow@ Mesoporous TiO2 toward Selective Oxidation of Styrene

Developing catalysts with structural characteristics, reusability, cost-effectiveness, environmental friendliness, and preferable catalytic performance is challenging for the selective oxidation of alkenes. In this article, we report the synthesis of magnetically separable CoFe2O4@ hollow@ mesoporous TiO2 with yolk–shell structure, which could be used as a selectivity variable and stable catalyst for the selective oxidation of styrene, yielding different oxidation products. With oxygen as the oxidant, epoxidation of styrene occurred, affording an epoxy group. With hydrogen peroxide as the oxidant, oxidative cleavage of double bonds in the styrene and further oxidation were conducted, affording a carboxylic acid group. Compared with pristine CoFe2O4, TiO2, and CoFe2O4/TiO2 core–shell structure, the CoFe2O4@ hollow@ mesoporous TiO2 with yolk–shell structure was found to be a more efficient catalyst for the oxidation of styrene. Meanwhile, the kinetic analysis and activation energies of different catalysts were investigated to illustrate the relationship between the performance and the structure of catalysts. Active radical scavenging experiments were conducted to figure out the dominant radicals in the oxidation reaction. The corresponding possible reaction mechanisms of the oxidation reaction were also proposed.

Functional hexanuclear Y(III) cluster-based MOFs supported Pd(II) single site catalysts for aerobic selective oxidation of styrene

Oxidation of styrene is one of the significant reactions in organic synthesis. In this work, a serious of PdCl2 moiety-decorated Y6-MOFs adopting post-synthetic strategy were fabricated as applicable single-site catalysts for oxidation of styrene. Specifically, the functional organic linker, H2bpydc (2,2′-bipyridine-5,5′-dicarboxylic acid), was first incorporated quantitatively into Y6 clusters-based MOF, [(CH3)2NH2]2[Y6(μ3-OH)8(bpdc)6] (bpdc = 4,4′-biphenyl dicarboxylic acid) via post-synthetic ligand exchange. Then post-synthetic Pd(II) metalation was performed to enhance the density of isolated single sites. The obtained Pd(II)-Y-bpydcx/bpdc1-x can be used as highly efficient heterogeneous single-site catalysts to promote selective oxidative cleavage of styrene to benzaldehyde using O2 as a oxidant under solvent-free and mild reaction conditions (1 atm and 80 °C). Importantly, when using Pd(II)-Y-bpydc0.8/bpdc0.2 (0.024 mmol Pd) as catalyst, the high conversion of styrene and the selectivity for benzaldehyde can reach 88.7 % and 82.2 %, respectively.

Tetra-substituted cobalt (II) phthalocyanine/multi-walled carbon nanotubes as new efficient catalyst for the selective oxidation of styrene using tert-butyl hydroperoxide

A novel tert-butyl hydroperoxide tetrasubstituted cobalt phthalocyanine (CoPc(OC10H14N)4) was synthesized by the classical phthalonitrile method. Subsequently, the cobalt phthalocyanine (CoPc) was immobilized on the multi-walled carbon nanotubes (MWCNTs) by ultrasonic impregnation method to obtain CoPc(OC10H14N)4/MWCNTs composites. The obtained composites were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) and diffuse reflectance spectra (DRS) techniques. Using tert-butyl hydroperoxide (TBHP) as an environmentally friendly oxidant, CoPc(OC10H14N)4/MWCNTs composites can be used as effective catalysts for the epoxidation of styrene. The effects of various variables, such as the mass ratio of CoPc(OC10H14N)4/MWCNTs, reaction time, temperature, molar ratio of substrate/oxidant and the amount of catalyst on the catalytic capability were evaluated. The conversion of styrene reached 97.15%, and the epoxidation product achieved the selectivity of 84.44% under the optimal reaction conditions.

Isatin Derived Mixed Ligand Metal Complexes as Antimicrobial, Antioxidant Agents and Catalyst for Oxidation of Styrene

A novel series of mixed ligand transition metal complexes of Cu(II), Zn(II), Ni(II) and Co(II) have been synthesized from the Schiff base ligand, 3-(naphthalen-1-ylimino)indolin-2-one (achieved by the condensation of isatin and naphthylamine) and 1, 10-phenonthroline. The structural features were corroborated by means of elemental analyses, molar conductance, IR, UV-Vis, 1H NMR and mass spectral studies. The data displays that these complexes have the composition of [MLX] type where X = 1, 10-phenonthroline. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion. The IR spectral data of the ligand exhibits the presence of iminic group and its complexes manifest that the imine group of the Schiff base coordinate with the metal ion and decreased value of carbonyl group indicates which coordinate to the metal. The proton NMR spectrum of the ligand shows the presence of imine group. The mass spectral data also confirms the metal complexes as [MLX] type. Molar conductance values of the complexes have been found in the range of 5–14 ohm−1cm2mol−1, suggesting the non-electrolytic nature of the complexes. The antimicrobial study reveals that copper and cobalt complexes are better antimicrobial agents than the standard drug streptomycin and Nystatin. The copper and cobalt complexes exhibit remarkable antioxidant potential than the other complexes. The catalytic oxidation of styrene by H2O2 was carried out in acetonitrile in the presence of mixed ligand metal complex as catalyst. The result of the catalytic study reveals that the zinc complex effectively catalyses the oxidation of styrene.

In situ Deposition of ‘Naked’ Gold Nanoparticles Supported on Silica Spheres as Recyclable Catalysts in Styrene Epoxidation

The rational designs of particle size, morphology and surface states of the Au nanoparticles(AuNPs) are crucial for Au nanocatalyst. We herein report a method to synthesize the silica microspheres supported AuNPs(ca. 1 nm) and their application in controlling the reaction conversion and selectivity in styrene epoxidation. Surfactant-free AuNPs deposited on silica microspheres were in situ fabricated with aid of the Ag nanoparticles (AgNPs) as sacrificial template by galvanic replacement reaction, leading to AuNPs/SiO2 catalyst directly without any post-treatment to expose crystal facets. A high conversion of 46.7% and selectivity of 91.7% to styrene oxide was achieved with H2O2 as oxidant in ethanol. The solid catalyst could be reused at least 10 reaction cycles without significant decrease in activity and selectivity. This study not only supplies an active, recoverable catalyst for styrene oxidation with green oxidant and solvent, but also demonstrates that the silica microspheres functionalized with thiol groups have a superior ability in stabilizing noble metal nanoparticles even without any surfactant.

Investigating the catalytic activity of a novel phase‐boundary catalyst in oxidation of styrene

AbstractInhibiting the environment pollutions motivated the development of green catalytic systems. The present research proposed a novel model of phase‐boundary catalyst by using octadecyltrichlorosilane/polypyrrole/reduced graphene oxide/cotton (OTS/PPy/RGO/CT) for the oxidation of styrene by aqueous hydrogen peroxide. The catalytic activities were examined in both stirring and static conditions. The effect of electric current was also studied in static condition. The structural properties of the fabricated catalysts were characterized by X‐ray diffractometer, Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, and thermal analysis. Moreover, the influence of PPy and RGO on electrical current of textile was also examined by using four‐point probe technique. The catalytic activity of OTS/RGO/CT showed that the RGO could act as the catalytic active site in the oxidation of styrene with aqueous hydrogen peroxide, as indicated by the 21% enhancement in the conversion of styrene when the RGO amount was increased (12 times) in OTS/RGO/CT in stirring condition. Finally, it could be stated that RGO‐loaded cotton textile was a promising heterogonous catalyst for the oxidation reaction, specifically for the oxidation of styrene with aqueous hydrogen peroxide.

Amorphous TiO2–SiO2 composites as selective heterogeneous catalysts for the oxidation of styrene to 1, 2-epoxyethylbenzene

A series of amorphous TiO2–SiO2 composite oxides with different TiO2 contents were prepared by a one-step co-precipitation process as catalysts for selective oxidation of styrene to 1, 2-epoxyethylbenzene with aqueous hydrogen peroxide in acetonitrile. The amorphous TiO2–SiO2 composites are found to be much more catalytically active than the one with partially crystallized TiO2. The TiO2–SiO2 composite with 40 wt% TiO2 (TSCO-3) presents the best catalytic performance. Under the optimal reaction conditions, the styrene conversion can reach 61.0% with a high selectivity of 95.4% to 1, 2-epoxyethylbenzene upon 1 h reaction. Moreover, the TSCO-3 catalyst exhibits a good cycling stability. The excellent catalytic performance can be attributed to the numerous exposed active centers and the fast release of the product from the active centers.

Synthesis and characterization of water-soluble arene-ruthenium complexes and their application in biphasic olefin oxidation

New water-soluble complexes [(η6-C6H6)RuCl(C5H4N-2-CH = N-R)]Cl (1) (with R = 4-hydroxymethylphenyl (a), 2,4-dichlorophenyl (b), 2-fluorophenyl (c), 3-carboxyphenyl (d)) have been synthesized by reacting [(η6-C6H6)Ru(μ-Cl)Cl]2 with the N,N′-bidentate ligands in a 1:2 ratio. Full characterization of all complexes was accomplished using 1H and 13C NMR, elemental analyses, UV-Vis spectroscopy, IR spectroscopy and single crystal X-ray crystallography for determination of the structure of 1d, as 1d·4H2O. The single crystal structure confirmed coordination of the ligand to the ruthenium(II) center leading to a structure commonly described as a pseudo-octahedral, three-legged piano stool. The geometry around the Ru(II) center is such that the arene ring occupies the apex of the stool while the N,N′-bidentate ligand and a chloride occupy the base of the stool. The synthesized Ru(II) complexes were tested as catalysts for oxidation of styrene using NaIO4 as a co-oxidant in a biphasic system. All complexes were active, giving good yields of benzaldehyde. Catalyst 1c was later investigated for olefin oxidation and gave high yields of the corresponding aldehydes as the major products in all cases.

Ag nanoparticles supported on UiO-66 for selective oxidation of styrene

By immobilizing Ag nanoparticles to UiO-66, a series of nanocatalysts (Ag/UiO-66) were synthesized and used as catalysts for oxidation of styrene. The catalytic efficiency could be optimized by altering Ag loadings of Ag/UiO-66, solvents, the molar ratios of styrene to tert-butyl hydroperoxide (TBHP) and reaction temperatures. Interestingly, the Ag loadings 1.86wt% of Ag/UiO-66 exhibited high conversion, selectivity and recyclability in the selective oxidation of styrene.

Synthesis of tetra-aminophthalocyanine/graphite composites by chemical grafting method for styrene oxidation

ABSTRACT1,8,15,22-Tetra-aminophthalocyanine/graphite (ZnTAPc/Gr) composites were prepared by chemical grafting method. The property of styrene oxidation in the presence of tert-butyl hydroperoxide (TBHP) as an oxidant was studied. The prepared catalysts were characterized by UV-Vis spectroscopy (UV-Vis), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The obtained ZnTAPc/Gr composites were employed as catalyst for styrene oxidation in presence of tert-butyl hydroperoxide (TBHP) as oxidant. The results showed that styrene was oxidized efficiently in the ZnTAPc/Gr-TBHP system. The enhancement of the catalytic activity of ZnTAPc/Gr composites was investigated in terms of different oxidation conditions. It was found that the optimum oxidation condition was 0.04 g catalyst, 10 h reaction time and reaction temperature of 100°C. Under this condition, the conversion and the selectivity of styrene oxide was up to 73% and 84%.

Efficient valorisation of palm shell powder to bio-sorbents for copper remediation from aqueous solutions

Alternative bio-sorbents, prepared from cost effective pre-treatment of biomass have been used to remediate toxic heavy metals. Palm shell powder (PSP) and acid treated palm shell powder (APSP) provide an attractive approach for the removal of Cu(II) from aqueous solutions and further use of the copper loaded adsorbents as catalysts. PSP was charred with sulfuric acid (H2SO4) to oxidize ligno-cellulosic groups present in PSP, resulted in acid treated palm shell powder (APSP). Structure property relationship was explored with the help of sophisticated spectroscopic tools (13C nuclear magnetic resonance (13C NMR), X-Ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy). Pretreatment lead to conversion of ligno-cellulosic content to more valuable and easily process-able polysaccharide content.APSP and PSP displayed a maximum adsorption capacity of 125 and 36mg/g respectively for copper. Copper adsorption was found to be more in APSP due to presence of COOH groups which rendered the surface more hydrophilic and amenable to enhanced Cu2+ sorption. Furthermore the adsorbents loaded with copper could be used as catalysts for oxidation of styrene. The developed adsorbents promise advantages such as low cost, high adsorption capacity, environmental friendliness as well as zero sludge.

Titania-Loaded Coal Char as Catalyst in Oxidation of Styrene with Aqueous Hydrogen Peroxide

Abstract Titania-loaded coal char catalyst was successfully prepared. The preparation steps involved pyrolysis of low rank coal at different temperatures and durations, sulfonation, impregnation of titanium(IV) isopropoxide, and then heating at 110 °C. It is found that the coal chars’ surfaces were rough after sulfonation and impregnation, while large pore volume, high surface area and carbon composition were observed at low pyrolysis temperature for short duration. These properties contributed to high selectivity towards benzaldehyde (> 90 %) at 600 °C (0.5–2 h)) in styrene oxidation using aqueous hydrogen peroxide as the oxidant.

Synthesis and Catalytic Performance of SBA-15 Supported Catalysts for Oxidation of Styrene

Synthesis and Catalytic Performance of SBA-15 Supported Catalysts for Oxidation of Styrene

Styrene Epoxidation Over Heterogeneous Manganese(III) Complexes

Abstract The manganes(III) complex functionalised with 2,3-dihydropyridazine has been encapsulated in the supercages of the NaY zeolite using two different procedures, flexible ligand and in situ complex. The parent zeolite and the encapsulated manganese(III) complexes were screened as catalysts for styrene oxidation by using t-BOOH as the oxygen source in acetonitrile. Under the optimized conditions, the catalysts exhibited moderate activity with high selectivity to benzaldehyde

Significant improvement of styrene oxidation over zinc phthalocyanine supported on multi-walled carbon nanotubes

A novel hybrid catalyst (ZnPc–MWCNTs) was facilely prepared by a ultrasonic impregnation method. The as-prepared hybrid materials were characterized by FT-IR spectra, X-ray diffraction (XRD), diffuse reflectance spectra (DRS), scanning electron microscope (SEM), Raman spectroscopy and transmission electron microscopy (TEM). This hybrid material was employed as catalyst for styrene oxidation in presence of hydrogen peroxide as oxidant. The results showed that styrene was oxidized efficiently in the ZnPc–MWCNTs/H2O2 system. The enhancement of the catalytic activity of ZnPc–MWCNTs hybrid materials was investigated in terms of different oxidation conditions. It was found that the optimum oxidation condition was 40mg catalyst, 8h reaction time and reaction temperature of 60°C. Under this condition, the conversion and the selectivity of styrene oxide was up to 94% and 90.6%, respectively. Moreover, the catalytic mechanism of styrene oxidation to benzaldehyde by the ZnPc–MWCNTs hybrid was also discussed.

Improvement of catalytic activity in selective oxidation of styrene with H2O2 over spinel Mg–Cu ferrite hollow spheres in water

Uniform spinel Mg–Cu ferrite hollow spheres were prepared using carbon spheres as templates. For comparison, solid Mg–Cu ferrite nanocrystals were also prepared by sol–gel auto-combustion, hydrothermal and coprecipitation methods. All the samples were characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray diffractometry (XRD), transmission electron microscopy (TEM) and N2 physisorption. The samples were found to be efficient catalysts for oxidation of styrene using hydrogen peroxide as oxidant. Especially, in the case of Mg0.5Cu0.5Fe2O4 hollow spheres, obvious improvement on catalytic activity was observed, and 21.2% of styrene conversion and 75.2% of selectivity for benzaldehyde were obtained at 80°C for 6h reaction in water. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in six consecutive runs.

Hollow iron oxide nanoshells are active and selective catalysts for the partial oxidation of styrene with molecular oxygen

Well defined hollow iron oxide nanoshells are active, selective and recyclable catalysts for the oxidation of styrene into benzaldehyde using difficult-to-activate molecular oxygen as the sole oxidant. Using no noble metals, unprecedented conversion of 90% was maintained while high selectivity of 73% was able to be achieved.