Conversion Of Styrene Research Articles

Spectroscopy and catalytic activity study of gold supported on barium titanate nanotubes for styrene epoxidation

Gold (0.5–5wt.%) supported on barium titanate nanotubes (Au/BaTNT) were prepared, characterized and for the first time, investigated as catalysts for selective oxidation of styrene with oxygen (O2 or H2+O2) and peroxides (H2O2 or TBHP). Conversion of styrene enhanced when H2 was co-added to O2 in the reactions. Au/BaTNT activated O2 and H2 and produced H2O2in situ for use in oxidations. Peroxides were found better oxidants than O2. At optimized conditions, styrene oxide selectivity of 80.1wt.% at styrene conversion of 60.5wt.% was achieved over Au(1wt.%)/BaTNT using TBHP. Au particles (5.0–7.4nm) were dispersed and decorated on the walls of BaTNT. They exhibited superior performance to the known Au catalysts in styrene oxidation. Reactive oxygen species formed during oxidation reactions were followed with in situ spectral characterizations (diffuse reflectance UV–vis and FT-Raman). Au/BaTNT was reusable in four recycles with little loss in catalytic activity.

3D Macro-Mesoporous TiO2-Graphene Oxide (GO) Composite with Enhanced Catalytic Performance in the Epoxidation of Styrene and its Derivatives

It has been widely accepted that graphene oxide shows promising potential on facilitating electron transfer which can enhance catalytic properties. In this work, a 3D ordered macro-mesoporous titania composites with graphene oxide (TiO2-GO) were synthesized through a confinement self-assembly method and applied to the epoxidation reactions of styrene and its derivatives. XRD, BET, SEM, TEM and XPS were used to characterize the hierarchically ordered composites. The incorporation of GO in the TiO2-GO composite made the catalyst structure rather stable and dramatically improved the catalytic activity compared with pure mesoporous TiO2, the conversion of styrene in epoxidation raised from 53.68 % to 93.34 % as the TiO2 combined with GO. Based on the experimental results, the mechanism was proposed to study the π-π interaction between GO and styrene, which was further confirmed by Photoluminescence (PL) analysis, polarization and cyclic voltammetry curves. In short, combining GO with metallic oxide materials will enhance the catalytic performance in epoxidation reactions and such designed strategy can extend to other catalytic reactions.

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.

Synthesis of Ag-loaded 4A-zeolite composite catalyst via supercritical CO2 fluid for styrene epoxidation

In this paper, the silver nanoparticles (Ag NPs) were uniformly distributed to the 4A-zeolite via supercritical carbon dioxide (scCO2), and polyvinylpyrrolidone (PVP) was used as the capping agents. The transmission electron microscopy (TEM) detection of composite catalyst displayed that the Ag NPs had a narrow size distribution (3–6 nm). Catalytic property evaluation resulting showed the excellent catalytic activity of the Ag NPs/4A-zeolite samples. The high conversion of styrene and the superior selectivity of styrene oxide (SO) were shown to us when tert-butyl hydroperoxide (TBHP) was used as the oxidant in short reaction time. Solvents effects played a important role in the reaction, and acetonitrile was the optimal solvent for the styrene epoxidation via the investigation of solvents.

Atomic level tuning of the catalytic properties: Doping effects of 25-atom bimetallic nanoclusters on styrene oxidation

Atomically precise bimetallic MxAu25-x(SR)18 (MCu and Ag, R=CH2CH2Ph) nanoclusters are investigated as oxide-supported catalysts for the catalytic oxidation of styrene. Their catalytic properties are compared with the case of homogold Au25(SR)18 nanocluster. The oxide-supported MxAu25-x(SR)18 catalysts give rise to 42–82% conversion of styrene at 70°C using (diacetoxyiodo)benzene (PhI(OAc)2) as the oxidant. The Ag and Cu dopants are found to modulate both the activity (i.e., conversion of styrene) and the selectivity to styrene epoxide or benzaldehyde (major products). The AgxAu25-x(SR)18 clusters exhibit higher activity and benzaldehyde selectivity than the homogold cluster, while the CuxAu25-x(SR)18 clusters primarily enhance the selectivity to benzaldehyde without significantly changing the activity. The results provide insights into the factors that influence the catalytic activity and selectivity in styrene oxidation.

Dearomatization of Motor Fuels by Alkylation Over Zeolite Catalysts

A study was carried out on gasoline dearomatization in the presence of zeolites and subsequent ractionation of the alkylate to give dearomatized gasoline and an aromatic hydrocarbon concentrate. Catalyst acid sites were shown to play a part in the alkylation reactions. In the case of a feedstock with 1:1 aromatic hydrocarbon:styrene weight ratio, the aromatic hydrocarbon content in the gasoline was reduced from 22.58 to 6.51% upon complete styrene conversion. As a result, the gasoline component was environmentally friendly and phenylarylethane products suitable for use as dielectric liquids were obtained.

Improvement of the polyoxometalate's performance in the asymmetric oxidation of styrene via combined with chiral ionic liquid

The efficiency and enantioselectivity of polyoxometalate (POM) in the oxidation of styrene with H2O2 could be improved via simply combined the POM with the chiral ionic liquids (CILs), which consist of the quaternized alkyl bromide salts (with lengths of C-8, C-12, and C-16) derived from natural chiral S-nicotine. The hybrids showed synergistic advantages between POM and CILs, achieving a complete conversion of styrene after 1h of mild reaction and a relatively high selectivity for R-(−)-1-phenylethane-1, 2-diol with 72% yield and 96% ee. Further fluorescence analysis illustrated that CILs might serve for the enantiomeric recognition of R- than S-enantiomers.

Activity of Molybdate-Intercalated Layered Double Hydroxides in the Oxidation of Styrene with Air

Molybdate anions were intercalated into the interlayer spacings of (Mg, Al) like-hydrotalcite compounds as interlayer compensating anions. The synthesized samples have been characterized by XRD, FT-IR, Raman, EDS, UV–vis, BET, and XPS. The solids possess lamellar structure and uniform platelet particles. There is mainly Mo(VI) present in both tetrahedral and octahedral configuration in the samples. All the synthesized catalysts have been tested for the liquid oxidation of styrene at mild conditions. Under reported conditions, styrene conversion varies with the total amount of molybdate ions. Benzaldehyde and styrene oxide were two major components in the product mixture. The selectivity to styrene oxide was found to be associated with the nature of oxidants and the amount of tetrahedrally-coordinated Mo species in layered double hydroxides while that to benzaldehyde is related to the overall amount of MoO4 − anions in the sample. Product distribution obtained on Mg–Al–Molybdate like hydrotalcite catalysts in the liquid oxidation of styrene with air.

Applications of Multiphasic Microreactors for Biocatalytic Reactions

During the past decade, there was rapid progress in integrating microfluidic reactors and biocatalytic reactions for various applications. The combination of miniaturized technologies and microfluidics allowed coupling of scale- and time-dependent phenomena for bioprocess intensification. However, coupling microreactors and biocatalysis is highly complex, requiring an integrated approach addressing biocatalyst features, reaction kinetics, mass transfer, and reactor engineering, as outlined in this review. Dimensionless numbers are discussed, which help identify rate limiting steps and offer opportunities to enhance the overall reaction performance in solid–liquid biocatalytic reactions. This integrated concept is realized in a case study based on the biocatalytic conversion of styrene to (S)-styrene oxide using catalytic biofilms to demonstrate the pivotal role of this integrated approach for evolving the optimal (micro)-reactor configuration and design.

Catalytic evaluation of dendrimer and reverse microemulsion template Pd and Pt nanoparticles for the selective oxidation of styrene using TBHP

Here, we employed colloidal Pd and Pt nanoparticles synthesized by dendrimer templates as well as reverse microemulsions in the selective oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant. We investigate their catalytic behavior and the feasibility as oxidation catalysts. High selectivity to styrene oxide, was achieved in the oxidation of styrene. The catalytic activities in terms of styrene conversion decreased in the order of dendrimer-templated Pd nanoparticles>thiol-capped Pd nanoparticles by reverse microemulsions>dendrimer-templated Pt nanoparticles>thiol-capped Pt nanoparticles by reverse microemulsions. This indicated that Pd-based catalysts were more efficient to catalyze the styrene oxidation reaction as compared to Pt-based catalysts. Furthermore, the dendrimer template synthetic method produced catalysts with higher activity as compared to those prepared by the reverse microemulsion template. The catalytic activities and selectivity profiles in various reaction conditions such as solvent type, styrene to TBHP ratio, type of catalysts, catalyst dosing, and temperature are discussed. The changes of average nanoparticle size after the reactions and the recyclability of Pd and Pt catalysts are examined. Overall results indicated that although higher catalytic activities were obtained with the use of dendrimer-templated nanoparticles, better recyclability as well as selectivity to styrene oxide was achieved with the use of thiol-capped Pd nanoparticles synthesized by reverse microemulsions.

Regeneration of Aluminopalladium Catalyst for Hydrogenation Using Supercritical Fluid CO2-Extraction Process

An experimental setup was designed for studying the solubility of a catalyst-deactivating compound – polyisoprene – in pure supercritical carbon dioxide (SC-CO2) and in SC-CO2 with a co-solvent (3,5 wt % chloroform). In pure SC-CO2, the crossover-type variations in the solubility was observed in isotherms t = 70, 100 and 120 °C at the pressure region between 15 and 34 MPa, and the pressure of ca. 19 MPA determined in the top crossover point. Addition of chloroform to SC-CO2 was shown to result in an average 2 to 2,5 times increase in the solubility. The process of supercritical fluid CO2-extraction regeneration of the aluminopalladium catalyst LD-265 for hydrogenation was studied. Dimethylsulfoxide and ethanol were used as co-solvents for SC-CO2. The maximal efficiency of the regeneration was observed at the co-solvent concentration of 5,5–6,5 wt %, dimethylsulfoxide being more effective co-solvent than ethanol. With the catalysts subjected to the SC-CO2 regeneration, the resulting diene and bromine numbers, as well as conversions of styrene and methylcyclopentadiene, meet the standards on catalytic systems for selective hydrogenation of diene hydrocarbons to benzene-toluene-xylene fractions.

Catalytic Pseudomonas taiwanensis VLB120ΔC Biofilms Thrive in a Continuous Pure Styrene Generated by Multiphasic Segmented Flow in a Capillary Microreactor

This study investigated the survival and catalytic potential of a single species Pseudomonas taiwanensis VLB120ΔC biofilm for the conversion of styrene to (S)-styrene oxide in a multiphasic capillary microreactor containing the highly toxic substrate styrene as a pure phase. The catalytic biofilm was cultivated under high fluidic stress in a continuous three-phase segmented flow system comprising aqueous medium, air, and styrene. This concept required an adaptation period of 7 days, during which P. taiwanensis VLB120ΔC developed a biofilm exhibiting a remarkable cellular integrity with nearly 70% intact cells. In a three-phase segmented flow biofilm microreactor, an average specific styrene epoxidation rate of 10 g/Ltube/day was achieved continuously for a period of 20 days without any clogging problems. Overall, this note highlights the robustness of biofilms as a promising biocatalyst format for the conversion/synthesis of toxic organic chemicals and the applicability of multiphasic capillary microreactors for biofilm based catalysis.

New method to synthesize mesoporous titania by photodegradation of surfactant template

Mesoporous titania has been successfully synthesized by photodegradation removal of cetyltrimethylammonium bromide as the surfactant, after slow hydrolyzation of titanium(IV) isopropoxide. Fourier transform infrared spectra proved that photodegradation has successfully decreased the peak areas of the alkyl groups from the template. The nitrogen adsorption analysis showed that the pore size and the specific surface area of the mesoporous titania were 3.7 nm and 203 m2 g−1, respectively, proving the mesoporosity of the titania obtained with the existence of the interparticle mesoporosity which was confirmed by transmission electron microscopy. Based on X-ray diffraction results, the mesoporous titania obtained was in the form of crystalline anatase phase. Furthermore, results from the diffuse reflectance ultra violet-visible spectra showed that the composition of tetrahedral titanium(IV) was more than the octahedral titanium(IV). When the mesoporous titania obtained was used as a catalyst in the oxidation of styrene, an improvement in the conversion of styrene (38%) was observed when compared to those obtained using Degussa P25 TiO2 (14%) as the catalyst.

Experimental and theoretical evidences of the influence of hydrogen bonding on the catalytic activity of a series of 2-hydroxy substituted quaternary ammonium salts in the styrene oxide/CO2 coupling reaction

Among industrial applications of CO2, the formation of cyclic carbonates from epoxides offers relevant chemical potentialities. Here, various N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium salts (HEA16X) associated with different counter-anions (X−) have been investigated as catalysts of the cycloaddition of carbon dioxide to styrene oxide. Most of these salts were characterized by reasonable catalytic activities in benzonitrile at 120°C and under 15bar of CO2 compared to choline chloride and cetyltrimethylammonium bromide. The influence of three parameters has been studied: (i) the polar head group, (ii) the anion (I−, Br−, Cl− for halogens and HCO3−, mesylate (Ms−), triflate (Tf−)) in the HEA16X series, as well as (iii) the chain length.The higher conversion and selectivity obtained with HEA16Br, compared to CTABr, pointed out the beneficial contribution of the hydroxylated polar head. The role of the compensation anion or more exactly of its nucleophilicity on the catalyst activity was also shown. However, unexpected results with HCO3−, affording styrene oxide conversions up to 95% (better than with HEA16Cl), were also obtained.DFT calculations supported the beneficial influence of the 2-hydroxyethyl substituent and the unexpected reactivity of the ammonium hydrogenocarbonate, HEA16HCO3. The reaction profiles allowed to draw some correlations (i) between styrene oxide conversion and the relative energy of the first intermediate and (ii) between the styrene carbonate selectivity and the energy of the first transition state. A new and original mechanism was also proposed for the reaction catalyzed by ammonium hydrogenocarbonate.

Immobilization of Cu(II) in KIT-6 supported Co3O4 and catalytic performance for epoxidation of styrene

KIT-6 is a cage type three dimensional cubic mesoporous silicate with Ia3d type structure, which shows scintillating promise in nanocasting, surface functionality, metal incorporation, and pharmaceutics. Nevertheless, little attention was paid to its application as support in heterogeneous catalysts. Cu-containing cobaltosic oxide spinel composite supported by mesoporous silica KIT-6 was synthesized via impregnation method and subsequent calcination under different temperatures. The prepared ordered materials were characterized by X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy, atomic adsorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results showed that Cu2+ was successfully embedded in spinel structure when calcined at 550°C, in contrast, the samples through thermal treatment at 250°C remained hybrid composition of CuO and Co3O4. Catalytic performance of mesoporous materials was evaluated for epoxidation of styrene in the presence of tert-butylhydroperoxide as oxidant. Among a range of prepared materials, a significant enhancement in styrene conversion and selectivity of styrene oxide was obtained for Cu-spinel catalysts, in comparison with hybrid oxide. A dramatic decrease in catalytic activities was found while KIT-6 support was removed, due to the partial destruction of ordered structure of Cu–Co oxide. Consequently, the catalytic behaviors were chiefly ascribed to copper species and their textural properties.

Synthesis, characterization, electrical and catalytic studies of some coordination compounds derived from unsymmetrical Schiff base ligand

New unsymmetrical tetradentate Schiff base ligand derived from 5-chloro-2-hydroxyacetophenone, 2-hydroxy-5-methyl-3-nitro acetophenone and carbohydrazide and its complexes with VO(IV), Cr(III), Mn(III), Fe(III), MoO2(VI), WO2(VI), Zr(IV) and UO2(VI) have been prepared. They were characterized by elemental analysis, IR and electronic spectra, magnetic susceptibility measurements and thermal analyses. The Schiff base ligand has also been characterised by 1H-NMR spectroscopy. The thermal behaviour of metal complexes shows that the hydrated complexes lose water molecules of hydration in the first and then is immediately followed by decomposition of ligand molecule in the subsequent steps. The IR spectra suggest that ligand acts as dibasic tetradentate nature and coordination takes place through azomethine nitrogen and phenolate oxygen. The crystalline nature of the VO(IV) complex was conformed through the powder XRD analysis. The catalytic activity of the VO(IV) and Mn(III) complexes have been tested in the epoxidation reaction of styrene and conversion of styrene were 11.14-24.35% and 9.64-23.42%, respectively. The solid state electrical conductivity of ligand and its complexes were measured, which could obeyed the relation s = s0 exp (Ea/KT) over the temperature range 313-413 K. KEY WORDS: Schiff base, Metal complexes, TGA, Electrical conductivity, XRD, Oxidation of styrene Bull. Chem. Soc. Ethiop. 2015, 29(3), 387-397. DOI: http://dx.doi.org/10.4314/bcse.v29i3.6

Catalytic and Epoxy Reaction of Styrene

Styrene had been oxidized by using phosphor-tungstic acid as the catalyst, urea peroxide as an oxidant, and methanol as the solvent. The experimental results showed that phosphor-tungstic acid had higher catalytic activity; the conversion of styrene and the yield of epoxy benzethane and the selectivity of epoxy benzethane arrived at 93.2, 81.2, and 87.2%, respectively. The effects of the reaction condition on the epoxidation reaction were checked. When the ratio of urea peroxide, styrene, and phosphor-tungstic acid was 511.8:255.9:1, the yield of epoxy benzethane reached maximum value. The effect of stannic tetrachloride was examined. The experimental results indicated that the selectivity of epoxy benzethane was increased by adding stannic tetrachloride.

Cu(II), Co(II), Fe(III) or VO(II) Schiff base complexes immobilized onto CMK-3 for styrene epoxidation

Schiff base complexes containing transition metals (Cu, Co, Fe or V) were successfully immobilized onto amino-functionalized CMK-3 via a stepwise procedure as heterogeneous catalysts for styrene epoxidation. The materials were characterized by means of XRD, N2 adsorption/desorption, TEM, SEM, FT-IR, Raman, XPS, TG. and ICP-AES. The results of XRD, N2 adsorption–desorption and TEM revealed that the structure of CMK-3 was well preserved, while the results of FT-IR, TG, Raman, XPS and ICP-AES suggested that the Cu(II), Co(II), Fe(III) or VO(II) Schiff base complexes have been successfully incorporated onto amino-modified CMK-3. Catalytic results showed that high conversion of styrene (94.1%) and selectivity to styrene oxide (73.9%) can be achieved over the heterogeneous Co (II) catalyst with air as the oxidant and isobutyraldehyde as co-reductant. In addition, the functionalized CMK-3 catalyst was quite stable and could be recycled at least three times.

Oxovanadium(IV), copper(II) or cobalt(II) acetylacetone complexes immobilized on amino‐functionalized CMK‐3 for the aerobic epoxidation of styrene

Oxovanadium(IV), copper(II) and cobalt(II) acetylacetone complexes have been grafted onto amino‐modified CMK‐3‐O (VO‐NH2‐CMK‐3, Cu‐NH2‐CMK‐3 and Co‐NH2‐CMK‐3,respectively) and the materials thus prepared were used as heterogeneous catalysts for the aerobic oxidation of styrene. X‐ray diffraction, nitrogen adsorption–desorption and transmission electron microscopy measurements confirmed the structural integrity of the mesoporous hosts, and spectroscopic characterization techniques (Fourier transform infrared, X‐ray photoelectron, Raman) and thermogravimetry confirmed the ligands and the successful anchoring of the acetylacetone complexes to the modified mesoporous support. VO‐NH2‐CMK‐3 displayed a relatively good catalytic performance with 94.6% of styrene conversion using air as oxidant, while Cu‐NH2‐CMK‐3 gave 99.6% of styrene conversion using tert‐butyl hydroperoxide as oxidant. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of the halogen ligand in [Mn(salen)X] complexes on the catalytic styrene epoxidation in scCO2

[Mn(salen) X] (X=Cl, Br and I) complexes were synthesized with yields ranging 47–56%. The H2-salen ligand and complexes were characterized by elemental analysis, 1H- and 13C NMR, UV/Vis and FTIR spectroscopies. The obtained complexes were tested as active species in the catalytic styrene epoxidation in supercritical carbon dioxide under pretty mild pressure (8.0MPa) as solvent using either iodosylbenzene or hydrogen peroxide as oxidizing agents. Both, conversion of styrene and yield of styrene epoxide were favored as the electronegativity of the halogen ligand in the complex raised. Benzaldehyde, phenyl methyl ketone, benzoic acid, and 1-phenyl-1,2-ethanediol were other by-products detected by GC/MS together with the targeted styrene epoxide throughout the catalytic experiments. Second stage treatment in the single-pot reaction under 140°C and 1.0MPa did not yield the corresponding styrene carbonate, probably because an opposite trend takes place in every one of the two stages of reaction regarding the catalytic activity of the [Mn(salen)X] complex respect to the electronegativity of the halogen ligand.