Activity In Oxidation Of Styrene Research Articles

Influence of iron doping in mesoporous ceria on the physicochemical properties and catalytic activity in styrene oxidation

A series of nanosized Fe-Ce binary oxides (2, 5, 10, 20, and 30 wt% Fe) and pure oxides of Fe and Ce were prepared by the template-assisted coprecipitation method and evaluated for styrene oxidation. The synthesised binary oxides were investigated by Powder X-ray diffraction(PXRD), N2-physisorption, X-ray fluorescence (XRF), Field emission scanning electron microscopy (FE-SEM), Highresolutiontransmission electron microscopy (HR-TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Ultraviolet–Visiblediffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopies (XPS), and Hydrogen-temperature programmed reduction (H2-TPR). In particular, the influence of quantity of doped iron on the structure, phase composition, surface morphology, reducibility, and the catalytic performance of ceria is deeply investigated. All the synthesized Fe-doped ceria catalysts exhibited the formation of solid solutions, but a little α-Fe2O3 segregated on the surface of ceria at 20 and 30 wt% Fe doped ceria. Among all Fe-Ce binary oxides, the 10 wt% Fe-doped ceria catalyst demonstrated superior efficiency due to its optimal Fe content which achieved the high surface area, lattice oxygens, reducibility, and low crystallinity, as confirmed by BET (Brunauer-Emmett-Teller) measurements, XPS, H2-TPR and powder XRD analysis, respectively. To optimize the reaction conditions, effect of several experimental variables, such as reaction temperature, duration, catalyst quantity, styrene/tert-Butyl hydroperoxide (TBHP) mole ratio, and solvent polarity were investigated. Furthermore, the catalyst stability and consistent activity were confirmed by testing six reusability cycles.

Synergistic Ti-Fe Oxides on Fishbone-Derived Carbon Sulfonate: Enhanced Styrene Oxidation Catalysis

Fishbone-derived carbon sulfonate, modified through incipient wetness impregnation with titanium tetraisopropoxide and iron nitrate salts, displays catalytic activity in the oxidation of styrene with hydrogen peroxide (H2O2) as an oxidant. This was done to develop a cost-effective, non-toxic, and environmentally friendly bimetallic oxide catalyst, incorporating titanium and iron oxides on mesoporous-derived carbon fishbone to enhance styrene conversion and benzaldehyde selectivity in styrene oxidation using aqueous H2O2. The catalyst, featuring a combination of titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate, demonstrates higher catalytic activity than single oxide catalysts, such as titanium or iron oxides alone. Factors influencing the catalyst's performance are investigated by using FTIR, XRD, XRF, SEM, and BET surface area. The results reveal that the presence of both titanium and iron oxides on the surface of the fishbone-derived carbon sulfonate and the catalyst's surface area creates a synergistic effect, the primary factors affecting its catalytic activity in styrene oxidation using H2O2 as an oxidant.

CuI/AgI‐containing coordination compounds as advanced catalysts for selective oxidation of styrene to benzaldehyde

AbstractFour coordination compounds, [Cu(Hmthd)2Cl]n (1), [Cu3(mthd)2Br]n (2), [Ag(mthd)]n (3), and [Ag2(mthd)I]n (4) (Hmthd = 2‐mercapto‐5‐methyl‐1,3,4‐thiadiazole), were synthesized and characterized by inductively coupled plasma (ICP) elemental analyses, powder X‐ray diffraction (PXRD), and Fourier transform infrared (FT‐IR) spectroscopies. These resulting coordination compounds can act as efficient catalysts for the oxidation of olefins with tert‐butyl hydroperoxide (TBHP) as oxidant. Wherein, compound 2 performed extremely enhanced catalytic activity for oxidation of styrene at 80°C. Moreover, the addition of an appropriate amount of acid can promote the protonation of ligands and activate the two Ag‐containing catalysts to improve their catalytic efficiencies. Experimental results indicate that catalyst 2 has a low activation energy and excellent recycle catalytic property. Radical trap experiments were performed to verify that free radicals participate in the oxidation of styrene.

Nanosheet-like Ni-based metasilicate towards the regulated catalytic activity in styrene oxidation via introducing heteroatom metal

Multiple catalytic active centers tactically generated on the 2-dimentional catalytic carrier could afford certain promoting function thanks to their existed special synergy. Herein, Ni-based nanosheet-like metasilicate catalytic materials were developed as heterogeneous catalysts towards styrene oxidation for the first time. Concurrently, the special heteroatom cobalt or magnesium-incorporated Ni-based nanosheet-like metasilicate were developed together via the proposed synthesis tactics. The resulted sheet-like nanomaterials were meticulously characterized and identified through valid techniques. The introduction of heteroatom metal elements of cobalt or magnesium incorporated in the Ni-based nanosheet-like metasilicate was proven to trigger the regulated catalytic effect including positive and negative aspects towards styrene oxidation, and their function was identified and understood based on the reaction exploration results, in which the present cobalt significantly give rise to the promotive catalytic conversion activity and selectivity towards styreneoxide(conversion 96.8%, selectivity 78.4%), while the magnesium oppositely induced the restraining catalytic capacity(conversion 72%, selectivity 51.3%) on the Ni-based metasilicate compared with pure one. The obtained heterogeneous Ni-based metasilicate retain durable catalytic activity during five recycling for styrene oxidation and inherit the regulated catalytic performance in the substrate expansion.

Modification of Coal Char-loaded TiO2 by Sulfonation and Alkylsilylation to Enhance Catalytic Activity in Styrene Oxidation with Hydrogen Peroxide as Oxidant

The modified coal char from low-rank coal by sulfonation, titanium impregnation and followed by alkyl silylation possesses high catalytic activity in styrene oxidation. The surface of coal char was undergone several steps as such: modification using concentrated sulfuric acid in the sulfonation process, impregnation of 500 mmol titanium(IV) isopropoxide and followed by alkyl silylation of n-octadecyltriclorosilane (OTS). The catalysts were characterized by X-ray diffraction (XRD), IR spectroscopy, nitrogen adsorption, and hydrophobicity. The catalytic activity of the catalysts has been examined in the liquid phase styrene oxidation by using aqueous hydrogen peroxide as oxidant. The catalytic study showed the alkyl silylation could enhance the catalytic activity of Ti-SO3H/CC-600(2.0). High catalytic activity and reusability of the o-Ti-SO3H/CC-600(2.0) were related to the modification of local environment of titanium active sites and the enhancement the hydrophobicity of catalyst particle by alkyl silylation.

Titanium Containing Aluminophosphate Molecular Sieve for Oxidation of Styrene

Microporous aluminophosphate (AlPO-5) and titanium aluminophosphate (TAPO-5) molecular sieves, which are zeolite-like materials have been synthesized by direct hydrothermal method using two different templates; triethylamine (TEA) as organic base and tetraethylammonium hydroxide (TEAOH) as alkali base. XRD patterns confirmed that the TAPO-5 catalysts are identical with AFI structure but the crystallinity of the catalysts had decreased after the incorporation of titanium into the framework. Besides that, characterization of TAPO-5 catalysts using DRUV-Vis confirmed the coordination of titanium species and this evidenced also supported by the result 27Al MAS NMR. Catalytic performance of the TAPO-5 catalysts was tested in the oxidation of styrene to produce benzaldehyde and phenylacetaldehyde in the presence of hydrogen peroxide as oxidant. TAPO-5 catalysts showed higher activity in styrene oxidation compared to AlPO-5. Keywords: zeolite; aluminophosphate; titanium; organic template; styrene

Synthesis of cobalt-containing mesoporous catalysts using the ultrasonic-assisted “pH-adjusting” method: Importance of cobalt species in styrene oxidation

Cobalt-containing SBA-15 and MCM-41 (Co-SBA-15 and Co-MCM-41) mesoporous catalysts were prepared via ultrasonic-assisted “pH-adjusting” technique in this study. Their physiochemical structures were comprehensively characterized and correlated with catalytic activity in oxidation of styrene. The nature of cobalt species depended on the type of mesoporous silica as well as pH values. The different catalytic performance between Co-SBA-15 and Co-MCM-41 catalysts originated from cobalt species. Cobalt species were homogenously incorporated into the siliceous framework of Co-SBA-15 in single-site Co(II) state, while Co3O4 particles were loaded on Co-MCM-41 catalysts. The styrene oxidation tests showed that the single-site Co(II) state was more beneficial to the catalytic oxidation of styrene. The higher styrene conversion and benzaldehyde selectivity over Co-SBA-15 catalysts were mainly attributed to single-site Co(II) state incorporated into the framework of SBA-15. The highest conversion of styrene (34.7%) with benzaldehyde selectivity of 88.2% was obtained over Co-SBA-15 catalyst prepared at pH of 7.5, at the mole ratio of 1:1 (styrene to H2O2) at 70°C.

Direct synthesis of hierarchically porous TS‐1 through a solvent‐evaporation route and its application as an oxidation catalyst

Synthesis of hierarchically porous zeolites has drawn intensive interest because of their improved catalytic performance. It is highly desirable to find ways to generate these materials in a low‐cost and scalable way for their commercial applications. A solvent evaporation route has been established to synthesize hierarchically porous titanosilicalite‐1 (TS‐1). In the protocol, hexadecyltrimethoxysilane was added to an ethanolic solution of titanium isopropoxide, tetraethyl orthosilicate and tetrapropylammonium hydroxide, i.e. the embryo solution of TS‐1. The solution was subjected to solvent evaporation‐induced self‐assembly to afford an ordered dry gel. Subsequent steam‐assisted crystallization converted the dry gel into a hierarchically porous TS‐1. X‐ray powder diffraction (XRD), UV–visible diffusive reflectance spectroscopy, N2 physisorption and electron microscopic characterizations have been employed to elucidate the structure. Ti is incorporated into the tetrahedral sites of the MFI structure and mesopores around 20 nm penetrating the crystalline framework are formed. Hexadecyltrimethoxysilane plays a key role in creating mesopores as well as increasing the crystal size. The hierarchically porous TS‐1 exhibits improved activity in styrene oxidation and phenol hydroxylation. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis and characterization of peripheral and non-peripheral substituted Co(II) phthalocyanines and their catalytic activity in styrene oxidation

The synthesis of symmetrical cobalt(II) phthalocyanine complexes containing 2,2,3,3-tetrafluoro-1-propanoxy and 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups obtained from 4-nitrophthalonitrile and 3-nitrophthalonitrile are described. The new compounds were characterized by IR, 1H-NMR, 13C-NMR, UV–vis and MS spectral. These cobalt(II) complexes 2 and 6 are employed as catalyst for the oxidation of styrene using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide (H2O2) as oxidants. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. It was also investigated solvent effect on styrene oxidation reaction.

Manganese complexes with triazenido ligands encapsulated in NaY zeolite as heterogeneous catalysts

Two different methods were described for the preparation of manganese complexes with triazenido derivative ligands encapsulated in NaY zeolite. The catalytic behaviour of the heterogeneous catalysts was evaluated for styrene and cyclohexanol oxidation reactions. Encapsulation was achieved by two methods: (i) ion-exchange from an ethanol solution containing both bis(p-tolyl)triazenido ligand and manganese ions, with the ligand: Mn 3:1molar ratio (Method A) and (ii) the flexible ligand method (Method B). The heterogeneous catalysts were characterized by FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and chemical analyses. The results show that both preparation methods lead to effective encapsulation of the Mn{bis(p-tolyl)triazenido} (1:1) complex in the NaY zeolite framework. The heterogeneous catalysts show activity in oxidation of styrene and cyclohexanol with tert-butyl hydroperoxide (tBuOOH) as an oxygen source. The catalysts are chemo-selective in cyclohexanol oxidation, whereas in styrene oxidation reaction leads to styrene oxide and benzaldehyde.

Unusual activation during peroxidase reaction of a cytochrome c variant

► Mutations at N52, Y67 and M80 improve peroxidase activity of iso-1-cytochrome c variant (CYC-3). ► Apparently d -propionate participates in the activation of heme group. ► CYC-3 shows Cpd 0 in reaction with peroxide as detected by EPR. Cytochrome c has been extensively used as model of peroxidase reaction. The peroxidase activity and stability of a triple mutant CYC-3 (N52I, Y67F and M80A) were studied and compared to those of wild type protein (Wt-16). The CYC-3variant showed ten-fold increased activity in styrene oxidation. An intermediary specie that resembles to Cpd 0 (Fe III OOH) of peroxidases was detected through EPR measurements during the reaction of CYC-3 with H 2 O 2 . Using molecular dynamics (MD) it was found that mutations in CYC-3 induce conformational changes in the M80 loop promoting the rotation of D ring propionate toward heme iron and the inclusion of transient water molecules that could explain the formation of Cpd 0 intermediate. The effects of these conformational changes on the activity increase are discussed.

Improvement of catalytic activity in styrene oxidation of carbon-coated titania by formation of porous carbon layer

Porous carbon layer has been formed by treating the carbon-coated titania (C@TiO2) with KOH solution. Carbon-coated titania (C@TiO2) was obtained by pyrolysis of polystyrene-coated titania (PS@TiO2), which was produced by in situ polymerization of styrene by using aqueous hydrogen peroxide. The presence of polystyrene and carbon on the surface of titania were confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques. Carbon content was about 2.2wt.% with thickness of carbon layer ca. 5nm. After treating with KOH solution, PC@TiO2 with the pore size of ca. 5nm, total pore volume of 0.05cm2g−1 and Brunauer–Emmett–Teller (BET) specific surface area of 46m2g−1 has been obtained. Catalytic activity results showed that PC@TiO2 gave a higher activity in styrene oxidation compared to bare TiO2, and C@TiO2. The highest catalytic activity was obtained by using PC@TiO2 that obtained after treating C@TiO2 with 1.0M KOH solution with benzaldehyde and phenylacetaldehyde as the main reaction products. At the higher concentration of KOH solution, the catalytic activity decreased when crystallinity of TiO2 decreased.

Optimization of reaction conditions in selective oxidation of styrene over fine crystallite spinel-type CaFe 2O 4 complex oxide catalyst

The CaFe 2O 4 spinel-type catalyst was synthesized by citrate gel method and well characterized by thermogravimetric analysis, atomic absorption spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The crystallization temperature of the spinel particle prepared by citrate gel method was 600 °C which was lower than that of ferrite prepared by other methods. CaFe 2O 4 catalysts prepared by citrate gel method show better activity for styrene oxidation in the presence of dilute H 2O 2 (30%) as an oxidizing agent. In this reaction the oxidative cleavage of carbon–carbon double bond of styrene takes place selectively with 38 ± 2 mol% conversion. The major product of the reaction is benzaldehyde up to 91 ± 2 mol% and minor product phenyl acetaldehyde up to 9 ± 2 mol%, respectively. The products obtained in the styrene oxidation reaction were analyzed by gas chromatography and mass spectroscopy. The influence of the catalyst, reaction time, temperature, amount of catalyst, styrene/H 2O 2 molar ratio and solvents on the conversion and product distribution were studied.

Direct incorporation of vanadium into three-dimensional KIT-6: 2. Reactivity test for styrene oxidation

The direct incorporation of vanadium into the three-dimensional (3-D) cubic Ia3d mesostructure designated as V-KIT-6 was prepared, and the material obtained therein showed a very high specific surface area of ~1,000 m 2 /g with tunable pore diameters in a narrow distribution of sizes, ~5.7 to 6.0 nm. The coordination and nature of the V sites in V-KIT-6 were characterized by 51 V-spin-echo NMR analysis. It shows that after calcination, the V 4+ species are totally oxidized to the V 5+ state with 4- and 6-coordinated V-O environments in a highly dispersed state with much less crystalline V2O5 formation. The calcined V-KIT-6 materials showed excellent catalytic activity in the direct oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant.

Absence of Subsurface Oxygen Effects in the Oxidation of Olefins on Au: Styrene Oxidation over Sputtered Au(111)

The influence of subsurface oxygen and surface roughness on the selectivity and activity for styrene oxidation was investigated on Au(111). Buried oxygen and a rough surface morphology was created ...

Alkylsilylated Gold Loaded Magnesium Oxide Aerogel Catalyst in the Oxidation of Styrene

Aerogel-prepared magnesium oxide (A-MgO) was modified by attachment of gold particles. Subsequent modification of its surface with alkylsilylation of n-octadecyltrichlorosilane and chlorotrimethylsilane exhibits a high catalytic activity for oxidation of styrene with tert-butyl hydroperoxide in liquid phase. Catalytic results show that the introduction of gold on the surface of A-MgO gives a higher catalytic activity in styrene oxidation compared to titanium dioxide. The effect of surface modification of A-MgO was studied with XRD, UV-Vis DR, FTIR and nitrogen adsorption analysis.

Study on Mn(III)‐Salen and Catalysis for Styrene Oxidation

In this paper, three Mn(III)‐Salen complexes are synthesized and their catalytic activity for styrene oxidation were studied. Four Shifft‐basa are prepared by condensation of salicylaldehyde or its derivatives with diamine, then chelated with Mn and formed into Mn(III)‐Salen complexes. Their chemical structures are characterized by IR, UV, etc. Furthermore, the catalytic activities of the Salen compounds for styrene oxidation with oxygen are primarily explored. The experiments show that among them, Mn(III)‐Salen‐2 is the most excellent catalyst for styrene oxidation with high conversion of styrene (77.1%) and selectivity of benzaldehyde (90.4%).

On the location of different titanium sites in Ti–OMS-2 and their catalytic role in oxidation of styrene

Abstract Octahedral manganese oxide molecular sieves (OMS-2) modified by impregnation of TiO 2 exhibit a higher catalytic activity for oxidation of styrene with tert -butylhydroperoxide in comparison to titanium-incorporated OMS-2, where the styrene conversions were ca. 70% and 45–50%, respectively. The framework of titanium species has no effect on the enhancement of catalytic activity, while the non-framework of titanium species induces a synergetic effect that enhances the oxidation of styrene with tert -butylhydroperoxide.

Role of Manganese Oxide Octahedral Molecular Sieves in Styrene Epoxidation

Manganese oxide octahedral molecular sieves having 2 x 2 tunnel structure (OMS-2) and synthesized by different methods were used for studying styrene oxidation with tert-butyl hydroperoxide (TBHP) as the oxidant. The catalytic activity of the as-synthesized OMS-2 materials was investigated. The physical and chemical properties of the OMS-2 materials are related to their activity in styrene oxidation. This particular study emphasizes the acid-base properties and the porous nature of these materials, and their role in styrene oxidation. Results of styrene oxidation reveal that acidity coupled with high porosity play a crucial role in these catalytic reactions. A desired acidity coupled with pore volume found in OMS-2 synthesized by reflux methods (OMS-2(R)) and high-temperature methods (OMS-2(HT)) produces materials with higher styrene conversion and styrene oxide selectivity when compared with OMS-2 synthesized by solvent free (OMS-2(S)), microwave (OMS-2(MW)), or hydrothermal methods (OMS-2(HY)). Transition metal doped OMS-2 catalysts show better selectivity of styrene oxide when compared to their undoped catalysts.

Bimetallic Ru-(Cr, Ni, or Cu) and La-(Co or Mn) incorporated MCM-41 molecular sieves as catalysts for oxidation of aromatic hydrocarbons

Bimetallic Ru-(Co, Nr, Cu) and La-(Co or Mn) modified-MCM-41 molecular sieves are prepared by direct synthesis using surfactant templating process and evaluated in liquid phase selective oxidation of styrene and benzene with hydrogen peroxide. The fresh and used bimetallic molecular sieves were characterized by various techniques such as X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and infra-red (IR) spectroscopy. These materials have a typical MCM-41 structure. It is very interesting to note that bimetallic Ru or La-based MCM-41 catalysts have a very high conversion in hydroxylation of benzene to phenol, but a lower activity in oxidation of styrene to benzaldehyde, being contrary to the catalytic behavior of monometallic modified MCM-41 catalysts. It is shown that the activity and selectivity of bimetallic Ru, La-MCM-41 catalysts and the efficiency of H2O2 depend on the presence of the second metal, temperature and conditions of the reactions. The reaction mechanism is proposed on the basis of the observation of different reaction products.