Epoxidation Of Styrene Research Articles

Sulfate-modified iron oxide catalyzed epoxidation of styrene with CO2 activated hydrogen peroxide in water

A practical sulfate-modified iron oxide catalytic system promoting the epoxidation of styrene using hydrogen peroxide as the oxidant in a solvent-free environment was developed. The key reactive oxygen species 1O2 was trapped and detected.

A novel Ag-loaded 4 Å zeolite as an efficient catalyst for epoxidation of styrene.

In this study, a novel Ag-loaded 4 Å zeolite was synthesized through the combined action of strong ultrasound and a high-voltage electrostatic field (the Z-Ag-UE) and its catalytic activity was evaluated in the epoxidation of styrene. The prepared catalysts were characterized using XRD, SEM, XPS, BET, TG, ICP-OES. The results showed that the silver evenly dispersed inside the octahedral 4 Å zeolite structure rather than being attached to the surface of the material like in the impregnation method, and this Ag-loaded 4 Å zeolite had a high surface area, uniform particle size distribution, and excellent high temperature thermal stability. The catalytic performance of the Ag-loaded 4 Å zeolite was investigated by varying the reaction conditions such as the amount of catalyst, temperature, and reaction time. Under optimized conditions, the Ag-loaded 4 Å zeolite showed high selectivity and conversion for the epoxidation of styrene, achieving a conversion rate of up to 98% and a selectivity of 94%. In particular, the catalyst had excellent recyclability and was reused more than fifteen times with the catalytic performance remaining unchanged. This method of loading metal prepared under external field conditions provides a new method and idea for future research in related fields.

Trimetallic MOF1@MOF2 heterostructure derived Co–NC@CuM–C for enhanced photothermal catalysis in styrene epoxidation

A trimetallic BMZIF@HKUST-1 heterostructure was successfully synthesized by directed epitaxial growth. Co–NC@CuOPd–C exhibited high SO yield (92.9%) for styrene epoxidation.

Mesoporous metal-organic framework NH2-MIL-101(Cr) as an efficient photocatalyst for the epoxidation of styrene.

Oxidation of styrene is a key reaction in the synthesis of pharmaceuticals and fine chemicals, and therefore oxidizing styrene with selective, efficient, and recyclable heterogeneous catalysts is significant from an environmental and economic standpoint. In this study, we report the transition Cr-based metal-organic framework [NH2-MIL-101(Cr)] as a heterogeneous photocatalyst, which efficiently promotes styrene epoxidation using H2O2 as a green oxidant, achieving high conversion efficiency (98%) and excellent selectivity (82%) under ambient conditions. Radical detection and quenching experiments reveal that the superoxide radical anion (O2˙-) acts as an active oxygen species, selectively promoting the oxidation of styrene to its oxidized form. This work provides insight into the development of a sustainable and cost-effective method for producing styrene oxide.

Development of a Ru–porphyrin-based supramolecular framework catalyst for styrene epoxidation

A new microporous supramolecular-framework catalyst containing Ru(ii)–porphyrin and pyrenylphenyl moieties is synthesised and structurally characterised. The framework catalyst efficiently promotes the epoxidation reactions of styrene derivatives.

Ultra‐low Mn(salen) supported on lignin and selective epoxidation of olefins

AbstractPrecise design of highly efficient, low metal load and eco‐friendly catalysts is the key to sustainable catalysis and green chemistry. In this work, we develop an ultra‐low loading of Mn(salen) complexes covalent grafted with lignin and applied in the selective epoxidation of olefins using O2 as an oxidant. Lignin not only provides the Mn(salen) graft sites but also promotes substrate enrichment via the π‐stacking interaction between substrate and supports. In particular, high turnover frequencies (TOF) of 1833 h−1 can be obtained for styrene epoxidation under mild conditions, which can be superior to most reported Mn(salen) supported catalysts. Compared with cellulose, the lignin‐based catalysts exhibit a higher selectivity toward styrene oxide during the epoxidation of styrene under mild conditions. Controlled experiments indicate that the synergistic effect between phenolic hydroxyl groups and the Mn(salen) complex can improve the conversion rate and selectivity during the selective epoxidation of styrene. This work designs a series of lignin‐based catalysts with ultra‐low Mn(salen) loading, which broadens the utilization of lignin and gives enlightenment for the rational design of lignin‐based catalysts.

Electroenzymatic cascade reaction on a biohybrid boosts the chiral epoxidation reaction

The chiral epoxidation of styrene and its derivatives is an important transformation that has attracted considerable scientific interest in the chemical industry. Herein, we integrate enzymatic catalysis and electrocatalysis to propose a new route for the chiral epoxidation of styrene and its derivatives. Chloroperoxidase (CPO) functionalized with 1-ethyl-3-methylimidazolium bromide (ILEMB) was loaded onto cobalt nitrogen-doped carbon nanotubes (CoN@CNT) to form a biohybrid (CPO-ILEMB/CoN@CNT). H2O2 species were generated in situ through a two-electron oxygen reduction reaction (2e–ORR) at CoN@CNT to initiate the following enzymatic epoxidation of styrene by CPO. CoN@CNT had high electroactivity for the ORR to produce H2O2 at a more positive potential, prohibiting the conversion of FeIII to FeII in the heme of CPO to maintain enzymatic activity. Meanwhile, CoN@CNT could serve as an ideal carrier for the immobilization of CPO-ILEMB. Hence, the coimmobilization of CPO-ILEMB and CoN@CNT could facilitate the diffusion of intermediate H2O2, which achieved 17 times higher efficiency than the equivalent amounts of free CPO-ILEMB in bulk solution for styrene epoxidation. Notably, an enhancement (∼45%) of chiral selectivity for the epoxidation of styrene was achieved.

The Rate of Absorption by the Styrene Epoxide–P-Toluene Sulfonic Acid Double System Depending on the Structure of the Aliphatic Tail of the Alcohol Solvent

Oxygen oxidation of the styrene epoxide (SE)–p-toluene sulfonic acid (TSA) double system (DS)in solutions of three primary alcohols, 1-octanol (OCT), n-butanol (BUT), and ethanol (ET), is studied. Thecorresponding concentration expressions of oxidation rates are as follows: VOCT = k [SE]0 [TSA]1, VBUT = k[SE]0 [TSA]0.63, and VET = k [SE]0 [TSA]0.7 at [SE] [TSA]. The proximity of the oxidation activation energiesin three alcohols contrasts with the difference in the oxidation rates: the oxidation rate in ET is threetimes the rate in n-butanol and thirty times the oxidation rate in 1-octanol.

The Rate of the Oxygen Absorption by the Styrene Epoxide–p-Toluene Sulfonic Acid Double System Depending on the Structure of the Aliphatic Tail of the Alcohol Solvent

The Rate of the Oxygen Absorption by the Styrene Epoxide–p-Toluene Sulfonic Acid Double System Depending on the Structure of the Aliphatic Tail of the Alcohol Solvent

A comparative investigation: evaluating the epoxidation of styrene with binuclear molybdenum(VI) complexes under conventional heating and microwave-assisted conditions

Two bis-[cis-MoO2]2+ core bearing complexes, designated as [{MoVIO2}2(L1)(H2O)2] (1) and [{MoVIO2}2(L2)(H2O)2] (2), were created by reacting MoO2(acac)2 with dihydrazone ligands, namely H4L1(i) and H4L2(ii) (generated from a 2:1 ratio of hydrazide of terephthalate and salicylaldehyde or o-vanillin) in a 2:1 ratio in a methanolic solution. These complexes were extensively characterized using several spectroscopic techniques. The shape of the complex [{MoVIO2}2(L1)(H2O)2] (1) was confirmed by SC-XRD, revealing an octahedral geometry. Moreover, the crystallographic analysis of complex (1) elucidates the substitution of a single facet of the water molecule with DMF, accompanied by the inclusion of an additional DMF molecule within the crystal lattice. These synthesized compounds were evaluated as potential catalysts for the epoxidation of styrene in the existence of oxidant (H2O2). The oxidation reactions were conducted using both conventional and microwave-assisted methods, and the obtained data were compared in terms of activity and selectivity.

Defect engineering enables synergistic action of hierarchical porosity and multifunctionality for efficient catalysis of diverse reactions

The limitations of embedding suitable functional groups as Brønsted and Lewis pairs in metal–organic materials hinder their application especially to promote catalysis reactions. Due to the generation abundance of unsaturated inorganic nodes upon partial ligand decarboxylation, Quasi-MOFs (Q-MOFs) are considered as a potential candidate for the installation of amino acids. Here for the first time, we demonstrated that Q-HKUST-1 possessing a Lewis acid site could be transformed into an excellent multifunctional chiral MOF (Q-HKUST-Cys), via post-synthetic modification by L-Cysteine. Applying this approach, we can fabricate a pore environment spatially decorated with multiple functional groups. The post-modified MOF has been characterized by a variety of techniques including PXRD, N2 sorption, 1HNMR, FT-IR, CD, and SEM/EDS mapping. Q-HKUST-Cys features unique properties, such as mesoporosity, high Lewis acid sites including Cu2+, Lewis base sites (NH2 group), Bronsted acid sites (COOH group), open channels, and optical activity. So, this chiral MOF exhibits excellent catalytic performance in various asymmetric reactions under mild conditions. The Q-HKUST-Cys is highly enantioselective heterogeneous and recyclable catalyst, in ring-opening of epoxide and nitroaldol reaction with up to 99 % ee, as well as 100 % and 90 % conversion, respectively. Besides, in the cycloaddition of CO2 to styrene-epoxide (STO), and production of the corresponding cyclic carbonate, this catalyst showed high performance (90 % conversion, 89 % ee) under mild conditions, at the atmospheric pressure of CO2 and in the solvent-free situation. The simultaneous presence of these properties makes Q-HKUST-Cys an attractive catalyst for the eco-friendly synthesis of fine chemicals through CC and CO bond formation. As a result, in this study, we showed that anchoring defective MOFs with multifunctional amino acids can be an effective approach for the utilization of synergistic effects in the promotion of many catalysis reactions.

Simple synthesis of hierarchical Co-Meso-UTL zeolite for efficient epoxidation of styrene

Co-zeolites with hierarchical porous are significantly desirable for the liquid-phase selective epoxidation of styrene that required relatively open reaction spaces. A typical UTL germanosilicate with the absence of organic structure-directing agent molecules inside pore channels suffered from severe structural collapse after ultrasonic treatment under pure water medium, originating from the unstable germanium-rich double four ring subunits. The simple strategy cleaved the weak linkage Ge-O bands and caused the irregular location of silicon-rich cfi layers. Subsequently, Co activity centers was incorporated into the framework through reacting with the abundant silanol groups located in the hydroxyl nests at room temperature. The random arrangement of mono- or multi- cfi layers induced the stacking faults and generated a large amount of intracrystal mesopores after calcination. The resultant Co-Meso-UTL catalysts favored the molecules diffusion of large-sized styrene and target products, improving the accessibility of Co active sites and exhibiting excellent catalytic performance in the styrene epoxidation reaction with single hydrogen peroxide (H2O2) oxidant. Especially, high styrene oxide product selectivity was also obtained through controlling appropriate H2O2-added content as well as reaction time, which possessed a highest turnover frequency value of 403 h−1 among the reported catalysts.

Pyrolysis Free Out-of-Plane Co-Single Atomic Sites in Porous Organic Photopolymer Stimulates Solar-Powered CO2 Fixation.

Herein, a facile strategy is illustrated to develop pyrolysis-free out-of-plane coordinated single atomic sites-based M-POP via a one-pot Friedel Craft acylation route followed by a post-synthetic metalation. The optimized geometry of the Co@BiPy-POP clearly reveals the presence of out-of-plane Co-single atomic sites in the porous backbone. This novel photopolymer Co@BiPy-POP shows extensive π-conjugations followed by impressive light harvesting ability and is utilized for photochemical CO2 fixation to value-added chemicals. A remarkable conversion of styrene epoxide (STE) to styrene carbonate (STC) (≈98%) is obtained under optimized photocatalytic conditions in the existence of promoter tert-butyl ammonium bromide (TBAB). Synchrotron-based X-ray adsorption spectroscopy (XAS) analysis reveals the single atom coordination sites along with the metal (Co) oxidation number of +2.16 in the porous network. Moreover, in situ diffuse reflectance spectroscopy (DRIFTS) and electron paramagnetic resonance (EPR) investigations provide valuable information on the evolution of key reaction intermediates. Comprehensivecomputational analysis also helps to understand the overall mechanistic pathway along with the interaction between the photocatalyst and reactants. Overall, this study presents a new concept of fabricating porous photopolymers based on a pyrolysis-free out-of-plane-coordination strategy and further explores the role of single atomic sites in carrying out feasible CO2 fixation reactions.

Synthesis, Spectroscopic Characterization, Catalytic and Biological Activity of Oxidovanadium(V) Complexes with Chiral Tetradentate Schiff Bases

New oxidovanadium(V) complexes, VOL1–VOL10, with chiral tetradentate Schiff bases obtained by monocondensation reaction of salicylaldehyde derivatives with 1S,2S-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol. All complexes have been characterized using different spectroscopic methods, viz. IR, UV-Vis, circular dichroism, one- (1H, 51V) and two-dimensional (COSY, NOESY) NMR spectroscopy, and elemental analysis. Furthermore, the catalytic ability of all compounds in the epoxidation of styrene, cyclohexene, and its naturally occurring monoterpene derivatives, i.e., S(−)-limonene and (−)-α-pinene has also been studied, using two different oxidants, i.e., aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP). In addition, the biological properties of these chiral oxidovanadium(V) compounds, but also cis-dioxidomolybdenum(VI) complexes with the same chiral Schiff bases, were studied. Their cytotoxic and cytoprotective activity studies with the HT-22 hippocampal neuronal cells revealed a concentration-dependent effect in the range of 10–100 μM. Moreover, vanadium(V) complexes, in contrast to cis-dioxidomolybdenum(VI) compounds, demonstrated higher cytotoxicity and lack of cytoprotective ability against H2O2-induced cytotoxicity.

Ethanol-Coordinated Dioxidomolybdenum(VI) Complexes with Aroylhyrazone Ligands: Synthesis, Spectroscopic Characterization, Crystal structures and Catalytic Oxidation Property

Two new dioxidomolybdenum(VI) complexes, [MoO2L1(EtOH)] (1) and [MoO2L2(EtOH)] (2), derived from the aroylhydrazone ligands N’-(2-hydroxyl-3-methoxybenzylidene)-3-methylbenzohydrazide (H2L1) and 4-fluoro-N’-(2-hydroxylbenzylidene) benzohydrazide (H2L2), respectively, were prepared in ethanol under ambient temperature. Both complexes were characterized by elemental analysis, IR and UV-Vis spectroscopy, as well as single crystal X-ray determination. The Mo atoms in the complexes are in octahedral coordination. Crystal structures of the complexes are stabilized by hydrogen bonds. The catalytic property for epoxidation of styrene by both complexes was studied.

A new route for the fabrication of SBA-15 supported Co3O4 and its catalytic application in the epoxidation of styrene

Cobalt isonicotinate tetrahydrate has been explored as the molecular precursor for the fabrication of both the bare and SBA-15 supported Co3O4. This method appears to be effective in minimizing the formation of oxide particles outside the mesopore volumes of SBA-15. Microstructural properties of the synthesized materials have been investigated by the PXRD, SEM, TEM, H2-TPR, N2-Physisorption, and DR. UV–Visible and Raman spectroscopic techniques. The SBA-15 supported nanocomposite has shown excellent catalytic activity giving 95% conversion in the epoxidation of styrene using TBHP as the oxidant. Deposition of trace amount of gold significantly enhances the epoxide selectivity of the catalysts up to 85%. The catalysts have shown excellent reusability.

Heterogeneous Chiral Covalent Organic Framework for the Enantioselective Epoxidation of Styrenes and Chromenes.

Herein, we report the synthesis of two-dimensional chiral ZnII Salen covalent organic frameworks (COFs) (2) via rapid microwave-promoted condensation of C3-symmetric 1,3,5-tris[(5-tert-butyl-3-formyl-4-hydroxyphenyl)ethynyl]benzene 1 with (1R,2R)-1,2-diaminocyclohexane in excellent yields. The synthesized chiral ZnII Salen COF (2) showed a 454 m2 g-1 BET surface area with excellent crystallinity and thermal stability. Further, the post-synthetic metal exchange reaction was performed for chiral ZnII Salen COFs (2) with Mn(OAc)2·4H2O to synthesize chiral MnIII Salen COFs (3) and utilized as an effective heterogeneous catalyst for the enantioselective epoxidation of styrenes and chromenes to afford chiral epoxides up to 72% ee. Chiral MnIII Salen COF (3) could easily be separated by centrifugation and reused up to four recycles with an observable loss in activity without impairing enantioselectivity.

The syntheses of a series of polyoxoniobate-based compounds: Their characterizations and catalytic applications in styrene epoxidation

Four polyoxoniobate-based compounds, namely [Cu(en)2]4[Cu(en)2(H2O)][VNb12V4O44]·2.25H2O·3OH– (1), [Cu(en)2]4[Cu(en)2(H2O)]3[Cu(en)2(H2O)2]3{[SiNb12Sb2O40]2}·25H2O (2), [Cu(en)2]2[Cu(en)2(H2O)2]4[SiNb12V2O42]·7H2O (3), and [Cu(en)2]3{[Cu(en)2][H2V4Nb6O30]}·12H2O (4) have been successfully synthesized and characterized by using FT-IR, XRD, and single crystal X-ray diffraction analyses, etc. Out of the four compounds, compound 1 is based on a rare four V capped polyoxoniobate cluster [VNb12V4O44]7−, [Cu(en)2]2+, and [Cu(en)2(H2O)]2+ complexes, forming a 1-D chain structure with Cu complexes as bridges. Compound 2 contains a Keggin polyoxoniobate with double Sb caps, and forming a network structure based on Sb capped polyoxoniobates and copper complexes with two different large parallelogram channels. Compounds 3 and 4 have been reported previously by Wang et al[1] and Hu et al[2], respectively. In this work, we not only reported the syntheses, structures and characterizations of these compounds, but also we further investigated the catalytic properties of these four compounds for styrene epoxidation.

Dual-site cooperation mediated by synergy in Mg-Co bimetallic oxide for high-performance styrene epoxidation reaction

Styrene epoxidation under mild reaction conditions is an important reaction to produce styrene oxide. Herein a synergistic intermetallic catalysis between Mg and Co in MgCo2O4 is revealed to be a facile strategy to facilitate the epoxidation performance, with the roles of CoO and MgO sites in the OMgOCoO structure responsible for activity and selectivity, respectively. Both experimental studies and theoretical calculations verify that the introduction of Mg into the Co3O4 framework contributes to the construction of alkaline environment on the catalyst surface, realizing a remarkable enhancement of the selectivity towards styrene oxide by suppressing its further transformation in a base-free condition. As a result, this strategy breaks the trade-off between activity and selectivity, contributing to both enhanced styrene conversion and selectivity to styrene oxide. The dual-site cooperation strategy in bimetallic oxides composed by earth-abundant elements is expected to provide important guidance and impetus for moving academically appealing chemistry such as styrene epoxidation to an industrial reality.

Mechanisms of Sulfoxidation and Epoxidation Mediated by Iron(III)-Iodosylbenzene Adduct: Electron-Transfer vs. Oxygen-Transfer Mechanism.

The mechanisms of sulfoxidation and epoxidation mediated by previously synthesized and characterized iron(III)-iodosylbenzene adduct, FeIII(OIPh) were investigated using para-substituted thioanisole and styrene derivatives as model substrates. Based on detailed kinetic reaction experiments, including the linear free-energy relationships between the relative reaction rates (logkrel) and the σp (4R-PhSMe) with ρ = -0.65 (catalytic) and ρ = -1.13 (stoichiometric), we obtained strong evidence that the stoichiometric and catalytic oxidation of thioanisoles mediated by FeIII(OIPh) species involves direct oxygen transfer. The small negative slope -2.18 from log kobs versus Eox for 4R-PhSMe gives further clear evidence for the direct oxygen atom transfer mechanism. On the contrary, with the linear free-energy relationships between the relative reaction rates (logkrel) and total substituent effect (TE, 4R-PhCHCH2) parameters with slope = 0.33 (catalytic) and 2.02 (stoichiometric), the stoichiometric and catalytic epoxidation of styrenes takes place through a nonconcerted electron transfer (ET) mechanism, including the formation of the radicaloid benzylic radical intermediate in the rate-determining step. On the basis of mechanistic studies, we came to the conclusion that the title iron(III)-iodosylbenzene complex is able to oxygenate sulfides and alkenes before it is transformed into the oxo-iron form by cleavage of the O-I bond.