Styrene Oxide Research Articles

Cholinium Pyridinolate Ionic Pair-Catalyzed Fixation of CO2 into Cyclic Carbonates.

A halide-free ionic pair organocatalyst was proposed for the cycloaddition of CO2 into epoxide reactions. Cholinium pyridinolate ionic pairs with three different substitution positions were designed. Under conditions of temperature of 120 °C, pressure of 1 MPa CO2, and catalyst loading of 5 mol %, the optimal catalyst cholinium 4-pyridinolate ([Ch]+[4-OP]-) was employed. After a reaction time of 12 h, styrene oxide was successfully converted into the corresponding cyclic carbonate, and its selectivity was improved to 90%. A series of terminal epoxides were converted into cyclic carbonates within 12 h, with yields ranging from 80 to 99%. The proposed mechanism was verified by 1H NMR and 13C NMR titrations. Cholinium cations act as a hydrogen bond donor to activate epoxides, and pyridinolate anions combine with carbon dioxide to form intermediate carbonate anions that attack epoxides as nucleophiles and lead to ring opening. In summary, a halide-free ionic pair organocatalyst was designed and the catalytic mechanism in the cycloaddition of CO2 into epoxides reactions was proposed.

Heterogeneously Catalyzed Partial Oxidation of Styrene on a Silver Surface

AbstractThe epoxidation of olefins on Ag/O systems is a significant industrial‐scale process within heterogeneous catalysis. However, the details of the surface reaction remain controversial, and it has been highly challenging to reconcile the findings from cataltyic studies under reaction conditions with the highly detailed static studies under carefully controlled ultra‐high vacuum (UHV) conditions. In this study, we combine molecular beam surface scattering and ion imaging techniques to explore the partial oxidation of styrene. This experimental approach enhances the sensitivity to the extent that we can directly observe the partial oxidation product, styrene oxide, under UHV conditions. We note that partial oxidation exclusively occurs at high oxygen coverages, which we attribute to the reaction of styrene with electrophilic oxygen formed specifically at elevated coverages.

Secondary Organic Aerosol Formation from the OH Oxidation of Phenol, Catechol, Styrene, Furfural, and Methyl Furfural

Secondary Organic Aerosol Formation from the OH Oxidation of Phenol, Catechol, Styrene, Furfural, and Methyl Furfural

Synthesis of zinc doped nickel cobaltite nanoparticles through homogeneous precipitation method for catalytic oxidation of styrene

The present study reports homogeneous precipitation method for the preparation of Zn2+ substituted Ni-Co LDH precursors and their subsequent conversion to Ni1−xZnxCo2O4 nanoparticles (NPs) via calcination. Different analytical techniques were used for characterization of the precursors and the Ni1−xZnxCo2O4 NPs. After characterization, catalytic activity of the Ni1−xZnxCo2O4 NPs was investigated towards oxidation of styrene. The effect of reaction time and amount of catalyst on the oxidation of styrene was also investigated. The Ni1−xZnxCo2O4 NPs exhibit better performance as catalyst for the styrene oxidation compared to undoped NiCo2O4 NPs.

Selective oxidation of styrene to benzaldehyde over mesoporous silica-based silver

An efficient catalyst with silver encapsulated into mesoporous silica (Ag/MS) was prepared via a hydrothermal method. The characterization was done with FT IR, XRD, SEM, BET, and EDX, and the well-organized structure of Ag/MS catalyst has been approved. It is found as an efficient catalyst for the selective oxidation of styrene to benzaldehyde employing hydrogen peroxide as a green and economic oxidant. The effect of various reaction conditions including reaction time, reaction temperature, different kinds of solvents were studied on the catalytic performance. In the optimized reaction conditions, the conversion of benzaldehyde was achieved 72% to 93%.

Structural basis of the Meinwald rearrangement catalysed by styrene oxide isomerase

Membrane-bound styrene oxide isomerase (SOI) catalyses the Meinwald rearrangement—a Lewis-acid-catalysed isomerization of an epoxide to a carbonyl compound—and has been used in single and cascade reactions. However, the structural information that explains its reaction mechanism has remained elusive. Here we determine cryo-electron microscopy (cryo-EM) structures of SOI bound to a single-domain antibody with and without the competitive inhibitor benzylamine, and elucidate the catalytic mechanism using electron paramagnetic resonance spectroscopy, functional assays, biophysical methods and docking experiments. We find ferric haem b bound at the subunit interface of the trimeric enzyme through H58, where Fe(III) acts as the Lewis acid by binding to the epoxide oxygen. Y103 and N64 and a hydrophobic pocket binding the oxygen of the epoxide and the aryl group, respectively, position substrates in a manner that explains the high regio-selectivity and stereo-specificity of SOI. Our findings can support extending the range of epoxide substrates and be used to potentially repurpose SOI for the catalysis of new-to-nature Fe-based chemical reactions.

Co(II)-N4 Catalysts for the Coupling of CO2 with Epoxides into Cyclic Carbonates: Catalytic Activity, Computational and Kinetic Studies.

In this study, we synthesized and characterized a series of cobalt(II) complexes bearing linear tetradentate N4 ligands. These Co(II)-N4 complexes proved to be efficient catalysts for the cycloaddition reaction between carbon dioxide and epoxides even at room temperature and 1 bar pressure of carbon dioxide without the need for solvents or cocatalysts. Furthermore, when combined with (triphenylphosphoranylidene)ammonium chloride (PPNCl) as a cocatalyst, the Co-N4 catalysts exhibited an impressive turnover frequency of up to 41,000 h-1 for coupling of epichlorohydrin/CO2. These Co(II)-N4 catalysts were found to have excellent stability and reusability, retaining their catalytic activity after they were recycled seven times. Density functional theory (DFT) calculations provided a comprehensive mechanism for the cycloaddition reaction, indicating that the rate-determining step is the epoxide ring opening, in both the presence and absence of PPNCl. Further kinetic studies allow us to determine the activation parameters (ΔH‡, ΔS‡, and ΔG‡ at 25 °C) of the coupling reaction using the Eyring equation. The Gibbs free activation energy obtained from the kinetic studies was in close agreement with that of the DFT calculations. The substituent effect on the cycloaddition reaction of CO2 with various substituted styrene oxides was also examined for the first time.

Sequential Paired Electrochemical Transformation of Styrene Oxide via Anodic Meinwald Rearrangement and Cathodic Nitro­methylation in an Electrochemical Flow Reactor with Catalytic Electrical Input

AbstractPaired electrosynthesis, which utilize both anodic and cathodic events in electrolysis, enables attractive transformations with higher current efficiency than conventional electrosynthesis. The electrochemical flow technique has been widely employed to ensure stable reaction conditions and mitigate issues stemming from mass transfer. In this study, the electrochemical Meinwald rearrangement of styrene oxides was investigated, yielding aldehydes as intermediates, followed by the nitromethylation of aldehydes to produce β-nitro alcohols. These reactions were achieved with catalytic electrical input, enabling the conversion of various styrene oxides into the corresponding β-nitro alcohols.

Single‐Atom Titanium on Mesoporous Nitrogen, Oxygen‐Doped Carbon for Efficient Photo‐thermal Catalytic CO2 Cycloaddition by a Radical Mechanism

AbstractDeveloping efficient and earth‐abundant catalysts for CO2 fixation to high value‐added chemicals is meaningful but challenging. Styrene carbonate has great market value, but the cycloaddition of CO2 to styrene oxide is difficult due to the high steric hindrance and weak electron‐withdrawing ability of the phenyl group. To utilize clean energy (such as optical energy) directly and effectively for CO2 value‐added process, we introduce earth‐abundant Ti single‐atom into the mesoporous nitrogen, oxygen‐doped carbon nanosheets (Ti−CNO) by a two‐step method. The Ti−CNO exhibits excellent photothermal catalytic activities and stability for cycloaddition of CO2 and styrene oxide to styrene carbonate. Under light irradiation and ambient pressure, an optimal Ti−CNO produces styrene carbonate with a yield of 98.3 %, much higher than CN (27.1 %). In addition, it shows remarkable stability during 10 consecutive cycles. Its enhanced catalytic performance stems from the enhanced photothermal effect and improved Lewis acidic/basic sites exposed by the abundant mesopores. The experiments and theoretical simulations demonstrate the styrene oxide⋅+ and CO2⋅− radicals generated at the Lewis acidic (Tiδ+) and basic sites of Ti−CNO under light irradiation, respectively. This work furnishes a strategy for synthesizing advanced single‐atom catalysts for photo‐thermal synergistic CO2 fixation to high value products via a cycloaddition pathway.

Catalytic styrene combustion over Pt/ZSM-5 Catalysts: Elucidating the deactivation mechanism induced by surface acid sites

Catalytic oxidation plays a pivotal role in styrene elimination, yet the development of highly active and robust catalysts remains a challenge. This work aims to elucidate the mechanisms underlying styrene oxidation and catalyst deactivation over the Pt@ZSM-5 catalyst. The Pt@ZSM-5 catalyst with low Si/Al ratio and high surface acidity leads to generation of small Pt particle, the initial activity of the catalyst varies in a volcanic curve with the size of Pt particles. Notably, the Pt@ZSM-5–40 catalyst with Pt particle size of 3.3 nm exhibits the highest reaction rate of 1.6 µmol gPt−1 s−1 at 100 °C. However, the Pt@ZSM-5 catalysts undergo significant deactivation at their T80 (the temperature styrene conversion of 80 %). Through comprehensive characterizations and detailed mechanistic studies, it has been observed that intermediates from styrene oxidation accumulate heavily on the catalyst, especially for the Pt@ZSM-5 catalyst with high acidity. Improving the reaction temperature could inhibit the deactivation which is dependent on the surface acidity of Pt@ZSM-5 catalyst. For instance, the Pt@ZSM-5–800 and Pt@ZSM-5–1200 catalysts remains high activity when reaction is operated at T99+30, whereas a substantially higher reaction temperature (T99+80) is required for both Pt@ZSM-5–18 and Pt@ZSM-5–40 catalysts to counteract deactivation. Our primary results provide insights to develop effective and robust catalyst for styrene oxidation.

Boosting the Faradaic Efficiency of Br--Mediated Photoelectrochemical Epoxidation by Local Acidity on α-Fe2O3.

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value-added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br-/HOBr-mediated method is developed to achieve a near-quantitative selectivity and ≈100% FE of styrene oxide on α-Fe2O3, in which low concentration of Br- as mediator and locally generated acidic micro-environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH-dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications.

Deciphering styrene oxide tolerance mechanisms in Gluconobacter oxydans mutant strain

Chemical production wastewater contains large amounts of organic solvents (OSs), which pose a significant threat to the environment. In this study, a 10 g·L−1 styrene oxide tolerant strain with broad-spectrum OSs tolerance was obtained via adaptive laboratory evolution. The mechanisms underlying the high OS tolerance of tolerant strain were investigated by integrating physiological, multi-omics, and genetic engineering analyses. Physiological changes are one of the main factors responsible for the high OS tolerance in mutant strains. Moreover, the P-type ATPase GOX_RS04415 and the LysR family transcriptional regulator GOX_RS04700 were also verified as critical genes for styrene oxide tolerance. The tolerance mechanisms of OSs can be used in biocatalytic chassis cell factories to synthesize compounds and degrade environmental pollutants. This study provides new insights into the mechanisms underlying the toxicological response to OS stress and offers potential targets for enhancing the solvent tolerance of G. oxydans.

Solvent-free conversion of CO2 in carbonates through a sustainable macroporous catalyst

The novelty of this work consists of synthesizing and exploiting a heterogeneous catalyst containing ammonium chloride as part of the polymeric sponge sites for CO2 capture. To this aim, the polymerization of 2-acryloyl(oxyethyl)trimethylammonium chloride was performed in cryo-condition, in the presence of a crosslinking agent, obtaining a lightweight macroporous freestanding material. Its efficiency in converting aromatic and aliphatic epoxides to the corresponding carbonates was successfully proved by using proton Nuclear Magnetic Resonance (1H NMR). Remarkably, the conversion of styrene oxide (SO) to styrene carbonate (SC) reached a yield of 99 % after 24 h of reaction. The calculated yield versus the aliphatic cyclohexene oxide is 71 %. Similar results were obtained by substituting the resin counter anion with Br−, although the conversion kinetic was slower than the chloride. It is worth noticing that reactions took place in the mixture without adding the tetrabutylammonium bromide (TBAB), typically used as a co-catalyst to convert epoxides into carbonates. The recyclability of the as-prepared catalyst was evaluated for four reaction cycles, evidencing stable properties without significant depletion of CO2 capture efficiency. Most importantly, the post-cleaning of the catalytic sponge is not required to be reused. Finally, the green chemistry metrics applied to the process demonstrated that our approach significantly mitigates risks and reduces environmental impact, thus elevating the overall cleanliness of our proof of concept.

Mechanistic Insights into the Effects of Ureas and Monomers on the Ring-Opening Alternating Copolymerization of Epoxides and Anhydrides Catalyzed by Organic Base/Urea.

Aliphatic polyester is an important polyester material with good biocompatibility and degradability, which can be synthesized through ring-opening alternating copolymerization (ROAC) of epoxides and anhydrides. Herein, density functional theory (DFT) is used to explore the mechanism of ROAC of epoxides (propylene oxide (PO), styrene oxide (SO), epichlorohydrin (ECH), and cyclohexane oxide (CHO)) and phthalic anhydride (PA) catalyzed by bis(triphenylphosphine) ammonium chloride (PPNCl) and ureas. It was found that the ring-opening polymerization (ROP) of epoxides is the rate-controlling step, and the benzyl alcohol (BnOH) as the initiator has little effect on the polymerization activity, which was consistent with previous experimental results. Calculated comparisons of the ROAC activity of CHO/PA catalyzed by four different ureas indicate that as the Lewis acidity of the urea increased, the energy barriers of the copolymerization increased and the activity decreased. The main reason was that the strong hydrogen-bonding interactions stabilized the key intermediate of the rate-controlling step and inhibited subsequent monomer insertion. Based on this, a series of new ureas with higher catalytic activity were designed by introducing electron-donating substituents. In SO polymerization, increasing the Lewis acidity of urea can improve the SO regioselectivity. In addition, the monomer ECH with CH2Cl shows higher activity of ROAC than PO and SO, which could be ascribed to the fact that the strong electron-withdrawing Cl atom stabilizes the transition state in the rate-controlling step and reduces the reaction energy barrier.

Porous Coordination Polymer MOF-808 as an Effective Catalyst to Enhance Sustainable Chemical Processes.

The improvement of sustainable chemical processes plays a pivotal role in safe environmental and societal development, for example, by reducing the use of hazardous substances, preventing chemical waste, and improving the efficiency of chemical reactions to obtain added-value compounds. In this context, the porous coordination polymer MOF-808 (MOF, metal-organic framework) was prepared by a straightforward method in water, at room temperature, and was unequivocally characterized by powder X-ray diffraction, vibrational spectroscopy, thermogravimetric analysis, and scanning electron microscopy. MOF-808 material was applied for the first time as catalysts in ring-opening aminolysis reactions of epoxides. It demonstrated high activity and selectivity for reactions of styrene oxide and cyclohexene oxide with aniline, using a very low amount of an eco-sustainable solvent (0.5 mL of EtOH), at 70 °C. Moreover, MOF-808 demonstrated high stability in the catalytic reaction conditions applied, and a notable reuse capacity of up to 20 consecutive reaction cycles, without significant variation in its catalytic performance. In fact, this Zr-based porous coordination polymer prepared by environment-friendly conditions proved to be a novel efficient heterogeneous catalyst, promoting the ring-opening reaction of epoxides under more sustainable conditions, and using a very low amount of catalyst.

Monomethylated Tröger's-base-containing polyimidazolinium salt as an efficient catalyst for cycloaddition of CO2 to epoxides

In this work, the model reaction of benzaldehyde and ammonium chloride has been studied by detailed product analysis and characterization. Subsequently, amarine and iso-amarine hydrochlorides (1, 2), dimethylated amarine and iso-amarine ionic salts (3, 4), together with monomethylated Tröger's-base ionic salt (6) have been separately synthesized and characterized. In addition, their catalytic performance towards the cycloaddition of CO2 to epichlorohydrin is compared under identical conditions. It is observed that their catalytic activity follows the order of 3 ≈ 4 >6 > 1 ≈ 2. Inspired by the highly catalytic activity of 3, 4 and 6, a novel monomethylated Tröger's-base-containing polyimidazolinium salt (namely PMDD-IL) has been synthesized by one-pot reaction of Tröger's-base-containing dialdehyde monomer (MDD) with ammonium chloride followed by treatment with excess iodomethane in the presence of sodium hydride. The as-synthesized PMDD-IL network exhibits highly catalytic activity towards the cycloaddition of CO2 to epoxides, providing nearly quantitative selectivity (99%) and conversion (99%) over a wide substrate scope of epoxides at atmospheric CO2 pressure (epichlorohydrin, 100 °C/10 h; epibromohydrin, 100 °C/12 h; glycidyl phenyl ether, 100 °C/24 h; styrene oxide, 100 °C/24 h; and 2-butyloxirane, 100 °C/24 h). The excellent catalytic activity of PMDD-IL network can be ascribed to the high nucleophilicity of iodine anion along with the strong interactions between PMDD-IL network and CO2 molecules.

A Multivariate 2D Metal-Organic Framework with Open Metal Sites for Catalytic CO2 Cycloaddition and Cyanosilylation Reactions.

This work reports the synthesis of a dual functional 2D framework, {[Zn2(4-tpom)2(oxdz)2]·4H2O}n (1), at room temperature, where a bent dicarboxylate, oxdz2- (4,4'-(1,3,4-oxadiazole-2,5-diyl)dibenzoate), and a neutral flexible N-donor linker, 4-tpom (tetrakis(4-pyridyloxymethylene)methane), are utilized. Its single-crystal X-ray analysis indicated a 2-fold interpenetrated 2D framework having tetracoordinated Zn(II) centers and dangling pyridyl groups. Its further characterization was carried out with elemental microanalysis, FTIR spectroscopy, TG analysis, and powder X-ray diffraction. The tetracoordinated Zn(II) centers as active Lewis acidic sites and the N atoms of 4-tpom as Lewis basic sites in 1 are explored for its functioning as a heterogeneous catalyst in two important reactions, (i) cycloaddition of CO2 with various epoxides and (ii) cyanosilylation reaction under solvent-free conditions. We could successfully show the cycloaddition of styrene oxide with CO2 (99% conversion) under balloon pressure with low catalyst (0.2-0.3 mol %) and cocatalyst (0.5-0.75 mol %) loadings, which is otherwise difficult to achieve. It was observed that all the substrates (aromatic and aliphatic), irrespective of their sizes, showed conversion percentage >99%. In the cyanosilylation reaction, a conversion of 96% was obtained with 1.5 mol % of 1 at room temperature for 12 h. This framework emerged as an excellent recyclable catalyst for both the reactions.

Solvent Free, Selective Oxidation of Styrene Catalyzed by Cobalt Acylpyrazolone Supported onto Neutral Alumina: Synthesis and Spectral Characterization

AbstractThe present work describes the synthesis of the Cobalt acylpyrazolone complex supported over neutral alumina and its use as a heterogeneous catalyst for selective oxidation of styrene. The catalyst mentioned here was characterized by various physicochemical techniques such as FT‐IR, TGA, CV, SCXRD, PXRD and BET. This heterogeneous catalyst has successfully been used to oxidize styrene to benzaldehyde in a solvent‐free condition with good conversion (87 %) and high selectivity (90 %) using H2O2 and TBHP as oxidants. The effects of the reaction parameters (catalyst concentration, reaction duration, and temperature) have also been investigated. The existing complex was discovered to be recyclable and sustainable with no change in conversion or selectivity for benzaldehyde. FT‐IR spectra of the regenerated catalyst indicated that the catalyst was undegraded and stable after the reaction. The novel feature of the current work reported in this paper is the selective oxidation of styrene without the need for solvents under mild conditions. Single Crystal Analysis.

Synthesis of the oleylamine coated mesoporous Fe3O4 nanospheres and their application towards the efficient chemical fixation of carbon dioxide

The present work reports the successful coating of Fe3O4 nanospheres with oleylamine utilizing a single-step solvothermal technique and its application to carbon dioxide's capture and chemical fixation. The existence of the pure cubic spinel phase of Fe3O4 was established by X-ray diffraction. Fourier transform infrared spectroscopy revealed vibrations corresponding to the oleylamine structure, affirming the coating of oleylamine on Fe3O4 nanospheres. X-ray photoelectron spectroscopy further confirmed the presence of oleylamine on the Fe3O4 surface, along with the constituent elements Fe and O. The nanospheres exhibited a spherical shape with an average diameter of ∼17 nm, shown by morphological investigations. Magnetic properties exhibited a Verwey transition at ∼114 K and a saturation magnetization of ∼60 emu/g. The surface area measurements revealed a pore volume of 0.0717 ccg−1 and surface area of 30.558 m2g-1. The existence of oleylamine on the surface of Fe3O4 nanospheres facilitated the capture of CO2 through chemisorption due to the amine group's high selectivity and the nanospheres' large surface area. In the presence of styrene oxide and tetra-n-hexyl ammonium bromide (THAB), the oleylamine-coated Fe3O4 nanospheres successfully converted CO2 to styrene carbonate. The magnetic core and high thermal stability of the material make it suitable for recyclability for the fixation of CO2 into products with added value. This work presents a promising approach for CO2 capture and utilization using Fe3O4 nanospheres coated with oleylamine, with potential applications in carbon capture and utilization technologies.

Efficient Selective Catalytic Fixation of CO2 into Epoxide to Form Cyclic Carbonates Using Sodium Aluminate Engineered Gamma Alumina Catalyst

The anthropogenic carbon dioxide (CO2) fixation and various engineering strategies are gaining very significant attention because of the expansion of the net‐zero carbon environment in the atmosphere. Herein, we designed a sodium aluminate@γ‐alumina (NaAlO2@γ‐Al2O3) catalyst by a simple and facile precipitation and impregnation tactics. A series of different weight percentage NaAlO2@γ‐Al2O3 materials were successfully synthesized and well characterized by using advanced analytical and spectroscopic techniques such as TGA, XRD, FE‐SEM, TEM/HR‐TEM, FT‐IR, Raman, TPD, and XPS analysis. The NaAlO2@γ‐Al2O3 catalyst was employed as a competent catalyst for the CO2 fixation under atmospheric pressure reaction conditions. The catalytic activity results evidently revealed that the cycloaddition reaction successfully achieved 94% styrene oxide conversion and 93% selectivity, along with an 87% yield of the styrene carbonate at 120 °C for 6 h. Furthermore, we comprehensively examined the effect of different reaction parameters such as the effect of sodium aluminate amount, co‐catalyst amount, temperature, and time for CO2 fixation reaction. Additionally, different terminal and internal epoxides were tested under optimized reaction conditions and achieved moderate to excellent yield of the desired cyclic carbonate products. Interestingly, a plausible reaction mechanism was proposed for the styrene carbonate synthesis using NaAlO2@γ‐Al2O3 catalyst surface with the support of characterization and experimental results. Remarkably, the NaAlO2@γ‐Al2O3 catalyst could be easily recoverable and successfully recyclable up to six consecutive cycles without declining its initial catalytic activity along with stable structural and physicochemical properties.