Catalytic Oxidation Of Styrene Research Articles

Stability in catalytic oxidation of styrene over Co3O4/Al2O3

The application of metal oxides in catalytic oxidation of organic pollutants has gained high interest due to their high efficiency and eco-friendly character. In this study, styrene was catalytically oxidized by coating Co and Ni oxides on Al2O3, SiO2, and Al2SiO5 support materials. Combination of 30 wt% Co oxide and Al2O3 presented the best styrene catalytic oxidation with detection of Co3O4 structure. The impact of different operating conditions on 30 wt% Co3O4/Al2O3 was also investigated. Higher initial concentration of styrene reduced the active site number and led to lower conversion. Likewise, decline of catalytic performance was also seen in the presence of higher space velocity and the absence of O2 in the system. In the deactivation test, deposited carbon was found through tests of catalyst characteristic. Moreover, the Langmuir-Hinshelwood and Mars van Krevelen kinetics modeling well fitted the data to describe the reaction kinetics of the study.

Synthesis, Spectroscopic, Thermal, and Catalytic Properties of Eight New Complexes of Metal(II) Formates or Propionates with Imidazole; Relationship between the Carbon Chain Length and Catalytic Activity.

In one of our previously published articles, we reported the synthesis, spectroscopic, thermal, and catalytic properties of four new M(II) acetate (where M = Co, Ni, Cu, Zn) complexes with imidazole. Presented compounds exhibited activity in the reaction on catalytic oxidation of styrene. In this study we have synthesized and investigated properties of analogous compounds, however using formates or propionates of mentioned metal cations instead of acetates. Such an approach allowed us to draw valuable conclusions concerning the relationship between the carbon chain length and catalytic activity, which is an important factor for catalyst modeling. Synthesized compounds have been thoroughly investigated using appropriate analytic techniques: AAS (Atomic Absorption Spectrometry), FTIR (Fourier-Transform Infrared Spectroscopy), and TGA (Thermogravimetric Analysis). Catalytic properties have been studied under the same previous conditions, using GC-FID (GC-chromatograph equipped with FID detector).

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

Catalytic oxidation of styrene and its reaction mechanism consideration over bimetal modified phosphotungstates

Cobalt and nickel modified phospotungstates (CoNiPW) were fabricated via the reaction of H3PW12O40•6•5H2O (PW) with Co(NO3)2•6H2O and NiCl•6H2O, followed by calcination; and then characterized by various physicochemical techniques, such as XRD, FT-IR, UV–vis, SEM, TEM and XPS to determine the surface morphology, structure and composition. The as-prepared CoNiPW was used as a catalyst for solvent-free oxidation of styrene with molecular oxygen oxidant. It exhibited efficient in achieving higher conversion of styrene and high selectivity to benzaldehyde. A detail study on influence of key reaction parameters, as well as catalytic role of various constituents in CoNiPW on the reactivity and selectivity was conducted to identify active sites. The reaction mechanism via benzyl alcohol intermediate was proposed by in situ adsorption of styrene on the catalyst surface and the product intermediate produced in the oxidation reaction. The recovery and reusability of the catalyst was also evaluated.

One-pot synthesis of bimetal MOFs as highly efficient catalysts for selective oxidation of styrene

A series of novel bimetallic organic framework materials (Cux-Coy-MOF) have been successfully prepared by a simple one-pot synthetic method, and their characters were evaluated via means of various techniques. The tested data showed a series of Cux-Coy-MOFs displayed good crystallinity and the doping of Co in original Cu-based framework would not change the morphology of the MOF catalysts. The catalytic activity of prepared materials was tested in the catalytic oxidation of styrene in the presence of TBHP. The effects of reaction time, reaction temperature and other reaction conditions on catalytic performance were systematically studied. The results revealed that the introduction of Co can improve the selectivity to form epoxides and reduce the yield of benzaldehyde without affecting the conversion rate of catalytic oxidation reaction of styrene. Excitingly, the Cu0.25-Co0.75-MOF showed better catalytic performance than Cu-MOF and Co-MOF under the optimal reaction conditions, the conversion rate of styrene reached 97.81%, and styrene oxide selectivity reached 83.04%, which indicated a significant synergistic effect of the Cu/Co bimetallic MOF. Furthermore, the Cu0.25-Co0.75-MOF catalyst exhibited good reusability that could be reused at least four times without significant inactivation. A series of novel bimetallic organic framework materials (Cux-Coy-MOF) have been successfully prepared via a simple one-pot synthetic method, and they exhibited high activity and selectivity as catalyst towards for oxidation of styrene.

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.

Solvent effect on the formation of active free radicals from H2O2 catalyzed by Cr-substituted PKU-1 aluminoborate: Spectroscopic investigation and reaction mechanism

The nature of a solvent plays an important role in selectively catalytic oxidations, influencing the catalytic activity and product selectivity. Most work attribute such roles to the polarity, acidity/basicity, or coordination ability of the solvent. Here, we systematically investigated the generated active free radicals in five different organic solvents during the catalytic oxidation of styrene by H2O2. Cr-doped PKU-1 aluminoborate was selected as the heterogeneous catalyst in this system. The solvent effect was comprehensively understood along this perspective. Hydroxyl radicals (OH) were preferred to be formed in CH3CN and responsible for the formation of carbonyl compounds, while superoxide ion radicals (O2−) were favored in DMF and beneficial to the epoxide production. The function of Cr3+ was correlated with the solvent effect and a tentative mechanism pathway was proposed accordingly.

Effect of graphitization degree of electrospinning carbon fiber on catalytic oxidation of styrene and electrochemical properties

Ag/carbon nanofibers and carbon nanofibers were prepared through electrospinning and high temperature carbonization. The catalyst was investigated through oxidation of styrene. The highest conversion of styrene respectively got to 98% and 70% when calcination temperature got to 1200 °C. CNFs (carbon nanofibers) have not only excellent catalytic performance but also relatively large accessible ion surface area to accommodate greater capacity and high graphitization degree to accelerate ion diffusion. CNFs exhibited excellent electrochemical performance for use as supercapacitors with high specific capacity of 271.1 F g−1 at current density of 0.5 A g−1, good rate capability and superior cycling stability over 3050 cycles.

Significant improvement of styrene oxidation over mononuclear/binuclear carboxyl metal phthalocyanine-attapulgite composites

Novel tetrasubstituted carboxyl metal phthalocyanine-ATP composites (CoTCPc-ATP) and hexa-substituted binuclear carboxyl metal phthalocyanine-ATP (biCoTCPc-ATP) catalysts were prepared by an ultrasonic impregnation method. The as-prepared samples are characterized by UV-Vis spectroscopy (UV-Vis), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The oxidation of styrene was examined by using tert-Butyl hydroperoxide (TBHP) as oxidant when CoTCPc-ATP/biCoTCPc-ATP composites are employed as catalysts. It was found that the biCoTCPc-ATP/composites exhibited more efficient catalysts comparing with CoTCPc-ATP in the styrene oxidation reaction. For the reason that the binuclear phthalocyanine had an enlarged π electron conjugated system, could provide more active sites and possessed the enhanced electronic reserve capacity compared with the mononuclear metal phthalocyanine contributing to the more prominent catalytic performance. Both composites can catalyze the oxidation of styrene to form styrene oxide as the main product along with benzaldehyde as the secondary product. Furthermore, the potential mechanism of the catalytic oxidation of styrene is also proposed.

Effect of Nano-TiO2 Immobilized on Activated Carbon, Zeolite Y and ZSM-5 on the Removal of Styrene Vapors from Polluted Air

TiO2 is a very well-known and well-researched material due to the stability of its chemical structure, biocompatibility, and its physical, optical and electrical properties. In this study, the synergistic effect of nano-TiO2 immobilized on activated carbon, zeolite Y and ZSM-5 on the removal of styrene vapors from polluted air was investigated. The prepared catalysts were characterized by SEM, BET and XRD analysis. The enhanced photocatalytic activity of AC, ZSM-5 and Y zeolite for the degradation of the styrene was attributed to the synergistic effect of TiO2. Photodegradation experiments were carried out at ambient temperature, different styrene concentrations (20, 100 and 300 ppm) and inflow of 0.5 l/min. The results indicate that adding TiO2 to the adsorbents increased the removal efficiency of styrene and among these catalysts; AC-TiO2 had a better performance. The high catalytic activity of AC-TiO2 should be attributed to the interaction between AC and TiO2, which provides the appropriate ability to adsorb reactants by AC and catalytic oxidation of styrene by TiO2. Better performances with this promising material – TiO2 deposited onto AC, ZSM-5 and Y zeolite – compared with bare TiO2 could be explained by the vicinity of photocatalytic and AC, ZSM-5 and Y zeolite adsorption sites. According to the results obtained from the adsorption capacity and the breakthrough and removal efficiency of catalysts, it can be concluded that coated adsorbents (AC, ZSM-5 and Y zeolite) with TiO2 can enhance the removal efficiency of styrene.

Synthesis, characterization, and catalytic oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)

Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylenediamine (HyP-Eda) with oxidized chloromethylated polystyrene. Oxidized chloromethylated polystyrene (PS-CHO) was prepared by oxidation of chloromethylated polystyrene (PS) with sodium bicarbonate in DMSO. By reacting DMSO solution of [VO(acac)2] with polymer-anchored Schiff base ligands I, II, and III, vanadium(IV) complexes PS-[VIVO(Ae-Eol)] (1), PS-[VIVO(Hy-Eda)] (2), and PS-[VIVO(HyP-Eda)] (3) were prepared. Structure and bonding of I, II, and III as well as corresponding vanadium complexes 1, 2, and 3 were confirmed by FT-IR, UV–vis spectroscopy, SEM, EDX, AAS, TGA, EPR, etc. Polymer-anchored vanadium(IV) complexes 1, 2, and 3 show, efficient catalysis toward oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene in the presence of hydrogen peroxide. Optimized reaction conditions for the oxidation of these alkenes was achieved by changing various reaction parameters (like amount of catalyst, amount of oxidizing agent, volume of solvent, etc.). Polymer-grafted 1, 2, and 3 can be reused multiple times without depletion of their activity.

Effect of nanoparticle metal composition: mono- and bimetallic gold/copper dendrimer stabilized nanoparticles as solvent-free styrene oxidation catalysts

A range of mono- and bimetallic AumCun nanoparticles (NPs), with varying metal compositions, was prepared by using a third-generation diaminobutane poly(propylene imine) (G3 DAB-PPI) dendrimer, modified with alkyl chains, as a stabilizer. It was found that the length of the peripheral alkyl chain, (M1 (C15), M2 (C11), and M3 (C5)), had a direct influence on the average nanoparticle size obtained, confirming the importance of the nanoparticle stabilizer during synthesis. The Au NPs showed the highest degree of agglomeration and polydispersity, whereas the Cu NPs were the smallest and most monodisperse of the NPs. The bimetallic NPs sizes were found to vary between those of the monometallic NPs, depending on the metal composition. Interestingly, the bimetallic NPs were found to be the most stable, showing very little variation in size over time, even up to 9 months. The DSNs were evaluated in the catalytic oxidation of styrene, using either H2O2 or TBHP as oxidant. Here, we show that the bimetallic DSNs are indeed the superior catalysts when compared to their monometallic analogues, under the same reaction conditions, since a good compromise between stability and activity can be achieved where the Au provides catalytic activity and the Cu serves as a stabilizer. These AumCun bimetallic DSNs present a less expensive and more stable catalyst with negligible loss of activity, opening the door to green catalysis.

Effects of the crystallization time on the mesoporous structure, texture, morphology and styrene oxidation performances of V-MCM-41

The new V-MCM-41 molecular sieves with good ordered hexagonal mesoporous structure and crystallinity were synthesized through in-situ hydrothermal preparation method. The effects of the crystallization time were discussed. The synthesized samples were characterized by X-ray diffraction, N2 adsorption/desorption, Fourier transformed infrared and scanning electron microscopy. The different structures, textures, morphologies of V-MCM-41 obtained with different crystallization times were observed and analyzed on the basis of the characterized results. The results showed that the V-MCM-41 molecular sieve obtained at 110°C for 48h crystallization times was of good spherical morphology, ordered hexagonal structure, most uniform pore size distribution and high surface area compared with other samples. Meanwhile, the V-MCM-41 molecular sieve with the high skeleton Si condensation and the good crystallinity was obtained. The heteroatom could be incorporated into MCM-41 framework with increasing crystallization times, which was beneficial to improve the catalytic activity and selectivity of pure siliceous MCM-41. The V-MCM-41 showed the good catalytic selectivity in catalytic oxidation of styrene using hydrogen peroxide, and the selectivity of the benzaldehyde and phenylacetic acid reached 30.68% and 49.44%, respectively.

Variation of Desolvation Behavior in Two Isostructural Metal–Organic Frameworks Based on a Flexible, Racemic Bifunctional Organic Linker

A racemic mixture of the chiral ligand 4,4′‐(1,2‐dihydroxyethane‐1,2‐diyl)dibenzoic acid was used to prepare two isostructural metal–organic frameworks, CPO‐49‐Zn and CPO‐49‐Mn, which contain coordinated solvent molecules at the metal site. The compounds showed different behavior upon desolvation. The dissociation of the solvent molecule from the metal site leads to a single‐crystal‐to‐single‐crystal transformation. In CPO‐49‐Zn, a change of coordination geometry from trigonal bipyramidal to tetrahedral occurs at the zinc atom. In CPO‐49‐Mn, a rearrangement of coordination mode of a carboxylate group occurs instead, leading to a 4+1 coordination of the manganese cation in the form of a capped distorted tetrahedron. N2 gas adsorption confirms that both desolvated structures are permanently porous. The behavior of the compounds upon heating has also been studied using variable temperature powder X‐ray diffraction. The presence of a coordinated solvent molecule in the as‐synthesized structures indicates the possibility to access the metal cation with reactive substrates. Both materials were evaluated in the catalytic oxidation of styrene. CPO‐49‐Mn showed significantly higher conversion than the CPO‐49‐Zn material.

Tunable catalytic properties of multi-metal–organic frameworks for aerobic styrene oxidation

The Cu and Co mixed metal–organic frameworks (MOFs) MOF-74(Cu/Co) with different Cu/Co ratios were prepared via a facile one-pot synthesis method and then characterized by means of various techniques. Whatever the Cu/Co ratios in the synthesized MOFs were, both Cu2+ and Co2+ could be uniformly distributed in MOF-74. The synthesized MOF-74(Cu/Co) materials were used as catalysts in styrene oxidation with O2 under solvent-free and mild reaction conditions. The results show that the catalytic properties of MOF-74(Cu/Co) can be tuned by varying the Cu/Co ratio in MOF-74. MOF-74(Cu) has a rather low catalytic activity but an absolute selectivity for benzaldehyde while MOF-74(Co) possesses a relatively higher catalytic activity, leading to the formation of benzaldehyde, styrene epoxide, and phenylacetaldehyde as well as to polystyrene. It is surprising that the incorporation of Cu2+ in MOF-74(Co) can completely inhibit the polymerization of styrene while the incorporation of Co2+ in MOF-74(Cu) can significantly enhance the conversion of styrene to benzaldehyde, styrene epoxide, and phenylacetaldehyde. In addition, by increasing the Co2+ amount in MOF-74(Cu/Co), the conversion of styrene and the selectivity for styrene epoxide and phenylacetaldehyde are increased while the selectivity for benzaldehyde is decreased. Moreover, the catalytic properties of MOF-74(Cu/Co) were compared with those of the physical mixtures of MOF-74(Cu) and MOF-74(Co), demonstrating the synergetic effects of Co2+ and Cu2+ in MOF-74(Cu/Co) on the catalytic oxidation of styrene. The current work reveals a strategy to incorporate multiple metal cations into MOFs for enhancing a specific catalytic property or achieving a new catalytic property.

Catalytic oxidation of styrene over Cu-doped hydrotalcites

A set of Mg–Cu–Al hydrotalcite-like materials with different Mg/Cu/Al ratios were synthesized by the co-precipitation technique. The prepared samples were characterized by physical techniques of XRD, FT-IR, Raman, N2 physisorption, SEM, TEM, XPS, and UV prior to use as catalysts for the liquid oxidation of styrene. All synthesized samples possess a well crystallized hydrotalcite structure, medium surface, and uniform particles. Cu2+ ions at octahedral sites stably in the brucite-like sheets catalyze the epoxidation of styrene with tert-butyl hydrogen peroxide oxidant. The catalytic activity is related to the amount of copper content and oxidant behavior. The Cu-doped hydrotalcite catalysts show a rather good activity and high selectivity to styrene oxide (80–90%) at a high styrene conversion level.

Liquid-Phase Catalytic Oxidation of Styrene by a Fiber-Supported Copper(II) Complex with High Catalytic Performance

A new type of polymer-supported catalyst, [PS-(PBIM)2Cu (II)], was synthesized by loading 2-(2’-pyridyl) benzimidazole on chloromethylated propylene-styrene graft copolymer fiber and subsequent treatment with Cu (OAc)2 in methanol. The prepared catalyst was used in the oxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant. The important reaction conditions, such as the reaction temperature, the ratio of oxidant/styrene, and the recycle times were examined. The experimental results show that the catalyst reveals relatively high catalytic performance with 84% conversion for styrene. The suitable conditions are as follows: n (styrene):n (TBHP)=1:3, the reaction temperature of 80 °C and the reaction time of 8 h. In addition, the catalyst used repeatedly for 3 times can still possess high catalytic activity.

Solvent effects on the catalytic activity of manganese(III) corroles

Four Mn ( III ) corroles that differ in their electronic environments based on meso-substitution by pentafluorophenyl and phenyl groups were synthesized and characterized by spectroscopic techniques. Utilization of these Mn ( III ) corroles for styrene oxidation using iodosylbenzene (PhIO) as oxygen source in toluene, dichloromethane (DCM), DMF, DMAc, THF and DMSO revealed a remarkable effect of solvent on the catalytic activity. Furthermore, the transformation of Mn ( III ) corroles into their corresponding Mn ( V )-oxo corroles, and subsequent treatment with styrene also indicated that more electron-deficient Mn ( V )-oxo corroles exhibit higher reactivity in toluene and DCM, while less electron-deficient Mn ( V )-oxo corroles exhibit higher reactivity in DMF and DMAc. A significant difference in the observed rates of reaction suggest that the catalytic oxidation of styrene by manganese corroles may proceed through different pathways, and is strongly solvent-dependent.

Dual investigation of lanthanide complexes with cinnamate and phenylacetate ligands: Study of the cytotoxic properties and the catalytic oxidation of styrene

Eleven lanthanide compounds [Y(cinn)3] (1), [La(cinn)3] (2), [La(4-OMecinn)3]·2H2O (3), [La(4-Clcinn)3]·2H2O (4), [La(4-OMephac)3]·4H2O (5), [La(4-Clphac)3]·3H2O (6), [Ce(cinn)3] (7), [Nd(cinn)3] (8), [Sm(cinn)3]·H2O (9), [Yb(cinn)3] (10) and [Sm(4-OMephac)3]·H2O (11) containing carboxylato ligands (cinn=cinnamate; 4-OMecinn=4-methoxicinnamate; Clcinn=4-chlorocinnamate; 4-OMephac=4-methoxyphenylacetate; 4-Clphac=4-chlorophenylacetate) have been synthesized and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, thermal analysis and X-ray diffraction powder patterns. In addition, compound 11 was characterized by single crystal X-ray diffraction studies. The cytotoxic activity of these complexes has been tested against three different human tumour cell lines HL60 (human promyelocytic leukemia), K562 (human erythromyeloblastoid leukemia) and MCF7 (breast cancer), observing a very modest cytotoxic activity for all tested compounds. In addition, toxicity tests to macrophages and erythrocytes have also been carried out, observing that none of the compounds is toxic against these immunocompetent cells. Finally, all the synthesized compounds have been tested as catalysts for styrene oxidation observing conversions higher than 50% after 19h of reaction as well as a relatively high selectivity to two main products benzaldehyde (BzA) and 1-phenylethane-1,2-diol (PhED). Complex 7 presents the higher conversion (99.56%) with a relatively high selectivity towards PhED of 72.07%.

Sheet Polymeric Iron (III) Porphyrin Complexes Catalytic Oxidation of Styrene with Molecular Oxygen

The sheet polymrtic iron (III) porphyrin complex [PFe (III)TPP] was prepared and charactrtized by FT-IR, TG-DTA and DTG, SEM and XPS. It was applied to catalytic oxidation of styrene with molecular oxygen and exhibited excellent catalytic activity. The results showed that the conversion reached to 50.5% in mild concitions, the major products of benzaldhyde (65.2% at 90°C) were obtained, and the catalyst could be efficiently reused five times.