Styrene Carbonate Research Articles

Selective CO2 Fixation to Styrene Oxide by Ta-Substitution of Lindqvist-Type [(Ta,Nb)6O19]8− Clusters

Metal oxide clusters composed of group 5 metal ions, such as Nb and Ta, exhibit catalytic activities for CO2 fixation to styrene oxide (SO) due to the highly negative natural bonding charge of the terminal O atoms that could work as CO2 activation sites. In this study, tetrabutylammonium (TBA) salts of [TaxNb6−xO19]8− (TBA-TaxNb6−x, x = 0–6) were prepared and Ta-substitution effect on the catalytic properties of TBA-TaxNb6−x for CO2 fixation to SO was investigated. We found that TBA-Ta1Nb5 shows the highest styrene carbonate (SC) selectivity (95%) among TBA-TaxNb6−x, although the SO conversion monotonously increases with the incremental Ta substitution amount. The CO2 fixation to SO under various conditions and in situ X-ray absorption fine structure measurements reveal that CO2 is activated on both terminal O sites coordinated to the Ta (terminal OTa) and Nb (terminal ONb) sites, whereas the activation of SO proceeds on the terminal OTa and/or bridge O sites that are connected to Ta. Density functional theory (DFT) calculations reveal that the terminal OTa of TBA-Ta1Nb5 preferentially adsorbs CO2 compared with other ONb base sites. We conclude that the selective CO2 activation at terminal OTa of TBA-Ta1Nb5 without SO activation is a crucial factor for high SC selectivity in the CO2 fixation to SO.

Acidic pyridinium ionic liquid: an efficient bifunctional organocatalyst to synthesis carbonate from atmospheric CO2 and epoxide.

Ionic liquids (ILs) are used as non-toxic, biodegradable, non-volatile, and relatively low-cost catalysts to synthesize 5-membered cyclic organic carbonates (COCs) from carbon dioxide (CO2) and different types of oxiranes in great conversion and selectivity. Single-component IL containing pyridinium salt moieties as quaternary amine, the carboxylic functional group as a H-bond donor, and bromine as a nucleophile and significant leaving group was synthesized by a simple method. The simultaneous selection and use of all mentioned factors in IL caused the epoxides converted into their corresponding carbonates under mild conditions, under 1 atm carbon dioxide (CO2) pressure (CO2 balloon), co-catalyst/ metal/ and solvent-free during 2.5 h. The synthetic catalyst converted styrene oxide (SO) to styrene carbonate (SC) with 100% conversion and selectivity. Moreover, the catalyst could be recycled more than four times before losing its remarkable catalytic activity. Finally, an inferential mechanism was suggested according to the experimental results.

Revisiting the Mukaiyama-type epoxidation for the conversion of styrene into styrene carbonate in the presence of O2 and CO2

Alkene epoxidation using the Mukaiyama process involving O2 and a sacrificial aldehyde, as the first step of the global alkene oxidative carboxylation, does not necessarily require a metal catalyst.

A CO2-philic ferrocene-based porous organic polymer for solar-driven CO2 conversion from flue gas

A ferrocene based polymer (Fc-POP) is designed for solar-driven CO2 cycloaddition from flue gas, resulting in high CO2-philic (adsorption capacity, 5.38 wt%, 0.15 bar) and outstanding styrene carbonate productivity (93%, 15 vol% CO2).

Piezoresistive Fibers with Large Working Factors for Strain Sensing Applications.

Piezoresistive fibers with large working factors remain of great interest for strain sensing applications involving large strains, yet difficult to achieve. Here, we produced strain-sensitive fibers with large working factors by dip-coating nanocomposite piezoresistive inks on surface-modified polyether block amide (PEBA) fibers. Surface modification of neat PEBA fibers was carried out with polydopamine (PDA) while nanocomposite conductive inks consisted of styrene-ethylene-butylene-styrene (SEBS) elastomer and carbon black (CB). As such, the deposition of piezoresistive coatings was enabled through nonconventional hydrogen-bonding interactions. The resultant fibers demonstrated well-defined piezoresistive linear relationships, which increased with CB filler loading in SEBS. In addition, gauge factors decreased with increasing CB mass fractions from ∼15 to ∼7. Furthermore, we used the fatigue theory to predict the endurance limit (Ce) of our fibers toward resistance signal stability. Such a piezoresistive performance allowed us to explore the application of our fibers as strain sensors for monitoring the movement of finger joints.

Efficiency in CO2-utilization strategies: The case of styrene carbonate synthesis in microdroplets conditions

The styrene oxide to styrene carbonate conversion performed in CO2 atmosphere, herein selected as a case study, was implemented in microdroplets (aerosol) reactions at the preparative scale (3.5 mmol of the starting material) and mild conditions (1 atm CO2 pressure), within a custom-made ultrasonic nebulization reactor. Upon optimization of the promoter stoichiometry (1 eq of 4.3 TEG/KI ratio) and methanol (MeOH) dilution (7.5 mL of 2.5 v/v MeOH/TEG), performances under mass transfer-limited conditions of this novel methodological paradigm have been compared at 25 °C and 50 °C with those implemented as: a) no-stirred, b) stirred, and c) sonicated bulk reactions. Complete selectivity and an apparent acceleration factor (AAF) of 1.9 was registered at both temperature for microdroplets reactions in respect with the sonicated counterparts, these latter performing better than the other bulk reactions. These significative efficiency improvements, candidate aerosol reactions as a preferred process intensification approach in the realm of effective CO2-utilization strategies and, in general, in the development and exploitation of gas-liquid two-phase reactions.

CO2 Cycloaddition to Styrene Oxide Catalysed by ZnBr2 Impregnated Rice Husk Ash Silica: Structural and Kinetics Studies

AbstractA series of ZnBr2 impregnated on rice husk ash silica catalysts were synthesised via the wet impregnation method for the CO2 cycloaddition to styrene oxide reaction. The X‐ray diffraction (XRD) analysis indicates that the impregnation resulted in the deterioration of the silica's pore channels. Catalyst with 0.5 w/w% of Zn (0.5 wt %ZnBr2‐SiO2) was highly active in the CO2 cycloaddition to styrene oxide. The conversion of styrene oxide (StO) was 89.1 %, with the styrene carbonate (SC) selectivity of 92.1 % under the optimum conditions (130 °C, 60 bar, 3 h and solventless). Additionally, the universality of 0.5 wt %ZnBr2‐SiO2 was also studied with other epoxides, and it shows good to excellent activity. The catalytic performance of the 0.5 wt %ZnBr2‐SiO2 remains constant after being reused three consecutive times. The activation energy of the reaction was determined to be 89.06 kJ/mol.

Hydroxyl-Imidazolium Ionic Liquid-Functionalized MIL-101(Cr): A Bifunctional and Highly Efficient Catalyst for the Conversion of CO2 to Styrene Carbonate.

Considerable attention has been focused on the development of catalysts for the coupling reaction of carbon dioxide (CO2) and epoxides due to the distinct advantages and importance of this reaction. To develop high-performance and easy-to-recycle catalyst is still a hot topic, especially for candidates with excellent activity under moderate conditions. A new heterogeneous catalyst, MIL-101-ImEtOH, is reported by post-synthesis modification, in which 2-(1-imidazol-1-yl) ethanol (Im-EtOH) is immobilized on MIL-101(Cr). In the absence of solvent and co-catalyst, MIL-101-ImEtOH exhibits high activity for the cycloaddition of CO2 and styrene oxide. A 95.6% yield is achieved under 0.5 MPa CO2 pressure and 90 °C by utilization of 50 mg of catalyst for 3 h. Moreover, MIL-101-ImEtOH is easily separated from the catalytic system by simple filtration. To elucidate the influence of hydroxyl group and porous structure on catalysis, other two supported ionic liquids, MIL-101-EtIm and PS-ImEtOH, are prepared and used to catalyze the title reaction under the same conditions. The contribution of each active component is determined by density functional theory along with noncovalent interaction analysis.

Cooperative multifunctional nanocarbon as efficient electro-catalysts for CO2 fixation to value-added cyclic carbonates under mild conditions

A novel electrochemical route for efficient cycloaddition of CO2 and styrene oxide (SO) forming the value-added product of styrene carbonate (SC) was proposed in this manuscript using non-metallic nanocarbon material as the catalyst electrode. The synthesized hollow nanospheres (HNSs) nanocarbon materials exhibited unique advantages of porous structure with thin carbon layer, which effectively facilitated the mass and charge transfer process and promoted the electrochemical reaction kinetics. In addition, correlation between the detailed structure analysis and the catalytic activity evaluation results show that the cooperation of nitrogen and oxygen functionalities on nanocarbon played a vital role in enhancing the catalytic activity of the carbon materials. The optimized HNSs catalyst exhibited high SO conversion of 66.9% and SC selectivity of 99.8% under the chronoamperometry at −0.5 mA for 6 hs, showing great potential in practical applications. The structure-function relations reported here may shed light on the rational design of the nanocarbon catalyst electrode and related reaction system for electrochemical synthesis of SC.

Alumina-Based Bifunctional Catalyst for Efficient CO2 Fixation into Epoxides at Atmospheric Pressure.

The quest toward sustainability and decarbonization demands the development of methods for efficient carbon dioxide capture and utilization. The nonreductive CO2 fixation into epoxides to prepare cyclic carbonates has gained attention in recent years. In this work, we report the development of guanidine hydrochloride-functionalized γ alumina (γ-Al2O3), prepared using green solvents, as an efficient bifunctional catalyst for CO2 fixation. The resulting guanidine-grafted γ-Al2O3 (Al-Gh) proved to be an excellent catalyst to prepare cyclic carbonates from epoxides and CO2 with high selectivity. The nitrogen-rich Al-Gh shows increased CO2 adsorption capacity compared to that of γ-Al2O3. The as-prepared catalyst was able to carry out CO2 fixation at 85 °C under atmospheric pressure in the absence of solvents and external additives (e.g., TBAI or KI). The material showed negligible loss of catalytic activity even after five cycles of catalysis. The catalyst successfully converted many epoxides into their respective cyclic carbonates under the optimized conditions. The gram-scale synthesis of commercially important styrene carbonates from styrene oxide and CO2 using Al-Gh was also achieved. Density functional theory (DFT) calculations revealed the role of alumina in activating the epoxide. This activation facilitated the chloride ion to open the ring to react with CO2. The DFT studies also validated the role of alumina in stabilizing the electron-rich intermediates during the course of the reaction.

Synthesis of Cyclic Carbonates Catalyzed by CaI2–Et3N and Studies on Their Biocatalytic Kinetic Resolution

Herein, we report a simple catalytic system consisting of CaI2 in combination with Et3N as a ligand for the efficient cycloaddition of CO2 to a variety of epoxides. Terminal (bio-based) carbonates were obtained under mild conditions (23 °C, 1 bar CO2 pressure) in excellent yields up to 97%. Under elevated temperature (70 °C) and higher CO2 pressure (10 bar), even challenging internal epoxides were converted, leading to the desired carbonates in yields up to 90%. 1H NMR experiments indicated the in situ coordination of the amine to the Lewis acidic calcium center as well as the activation of the epoxide. Furthermore, the enzymatic kinetic resolution of seven cyclic carbonates using readily available pig liver esterase was investigated. Styrene carbonate proved to be the most suitable substrate for the kinetic resolution, leading to (R)-styrene carbonate in 99% ee.

Ammonium zincates as suitable catalyst for the room temperature cycloaddition of CO2 to epoxides

We have recently shown that simple ammonium ferrates are competent catalyst for the cycloaddition reaction of CO2 to epoxides under moderate reaction conditions (T = 100°C, P(CO2) = 0.8 MPa). We report here that ammonium zincates of general formulae [TBA]2 [ZnX4] (TBA = tetrabutylammonium), simply obtained by treating an ethanolic solution of an appropriate zinc(II) salt with two equivalents of tetrabutylammonium halides, outperform ammonium ferrates in the synthesis of cyclic carbonates under milder reaction conditions (room temperature and atmospheric CO2 pressure). Using [TBA]2[ZnBr4] complex as homogeneous catalyst at 100°C and P(CO2) = 0.8 MPa a 52% conversion of styrene oxide with complete selectivity in styrene carbonate in just 15 min was observed, corresponding to a Turnover frequency (TOF) of 416 h−1. The same catalyst proved to be very active even at room temperature and atmospheric or very moderate CO2 pressures (0.2 MPa), with a quite broad range of substrates, especially in the case of terminal epoxides, with high selectivity towards cyclic carbonate products. The difference in reactivity of terminal and internal epoxides could be exploited using 4-vinylcyclohexene dioxide, where the endocyclic epoxide remained untouched when reacted at room temperature and the formation of the di-carbonate product was observed only at harsher conditions. A multigram scale conversion of propylene oxide was achieved (46 mmol) and the catalyst also proved to be recyclable (3 cycles) by distillation of the product and subsequent addition of fresh reagent, maintaining high conversion values and complete selectivity for propylene carbonate. This simple zinc-based catalytic system, which outperform the recently reported iron-based one by working at much milder conditions, could represent a valuable prospect in both laboratory and industrial scale, combining an inherent cheapness and synthetic easiness that should be deeply considered when the goal is to give value to a waste product as CO2.

Nicotinamide onium halide bidentate hybrid H–bond donor organocatalyst for CO2 fixation

H-bond donor (HBD) and nucleophilic halide cooperating catalysis was well developed in cycloaddition of CO2 with epoxide (CCE) reactions where common strong HBD was prevalent. Here a type of onium halide organocatalyst featured weak C–H and N–H HBD was proposed, designed and evaluated in CCE reactions. Based on biobased nicotinamide, nicotinamidium halide catalyst was prepared by simple alkylation on pyridyl N and/or on amide NH. A mono-alkylated on pyridyl N, 1-octyl nicotinamidium iodide, was screened an optimal catalyst that achieved 96 % yield of carbonate under 1 mol% catalyst loading, 1 atm pressure of CO2, 80 °C, by 24 h. Terminal epoxides were converted successfully into their corresponding cyclic carbonates by 84–99 % yields with 99 % selectivity. Scale-up preparation of styrene carbonate with 100 g of styrene epoxide (by 88 % yield and 98 % selectivity), and preparation of bis(cyclic carbonate) of a commercial diglycidyl ether of bisphenol A (by 79 % yield and 98 % selectivity) showed practical utility. The H-bonding activation between C–H and N–H HBDs with epoxide was validated by 1H NMR titrations. Designed analog catalysts to 1-octyl nicotinamidium iodide with blocked C–H or blocked N–H revealed the bidentate HBDs worked synergistically. The observations of the beneficial outcome of weak pyridium α-C–H and amide N–H H-bond donors proposed a protocol for simple yet efficient biobased H-bond donor organocatalyst development for CCE reactions.

Solar-driven all-in-one MOFs-based catalyst for highly efficient CO2 conversion

CO2 fixation and conversion are desirable to solve the exceeding CO2 emission. Traditional CO2 cycloaddition needs strict conditions, co-catalyst and solvent, causing energy intensive and complex recycle process. In this work, an integrated ionic polymers (IPs) and phosphomolybdate (PMo12) co-modified CuTCPPCo MOF all-in-one composite catalyst (PBPCT*) is designed for solar driven, solvent-free and co-catalyst-free CO2 cycloaddition. The PMo12 clusters and IPs offer abundant active sites for reactants activation and ring opening. The activation energy significantly decreases from 66.36 kJ·mol-1 of CuTCPPCo MOF to 49.47 kJ·mol-1 of PBPCT*, and guarantees higher efficient with 99.2% yield of styrene carbonate at 353 K for 12 h. The TOF of 580.73 h-1 under light density of 0.8 W/cm2 superior to traditional heating with TOF of 473.0 h-1. This provides a new avenue to gather all the advantages in one catalyst, furnishing a promising approach for reducing CO2 emission and utilization.

Unlocking Molecular Secrets in a Monomer-Assembly-Promoted Zn-Metalated Catalytic Porous Organic Polymer for Light-Responsive CO2 Insertion.

Anthropogenic carbon dioxide (CO2) emission is soaring day by day due to fossil fuel combustion to fulfill the daily energy requirements of our society. The CO2 concentration should be stabilized to evade the deadly consequences of it, as climate change is one of the major consequences of greenhouse gas emission. Chemical fixation of CO2 to other value-added chemicals requires high energy due to its stability at the highest oxidation state, creating a tremendous challenge to the scientific community to fix CO2 and prevent global warming caused by it. In this work, we have introduced a novel monomer-assembly-directed strategy to design va isible-light-responsive conjugated Zn-metalated porous organic polymer (Zn@MA-POP) with a dynamic covalent acyl hydrazone linkage, via a one-pot condensation between the self-assembled monomer 1,3,5-benzenetricarbohydrazide (TPH) and a Zn complex (Zn@COM). We have successfully explored as-synthesized Zn@MA-POP as a potential photocatalyst in visible-light-driven CO2 photofixation with styrene epoxide (SE) to styrene carbonate (SC). Nearly 90% desired product (SC) selectivity has been achieved with our Zn@MA-POP, which is significantly better than that for the conventional Zn@TiO2 (∼29%) and Zn@gC3N4 (∼26%) photocatalytic systems. The excellent light-harvesting nature with longer lifetime minimizes the radiative recombination rate of photoexcited electrons as a result of extended π-conjugation in Zn@MA-POP and increased CO2 uptake, eventually boosting the photocatalytic activity. Local structural results from a first-shell EXAFS analysis reveals the existence of a Zn(N2O4) core structure in Zn@MA-POP, which plays a pivotal role in activating the epoxide ring as well as capturing the CO2 molecules. An in-depth study of the POP-CO2 interaction via a density functional theory (DFT) analysis reveals two feasible interactions, Zn@MA-POP-CO2-A and Zn@MA-POP-CO2-B, of which the latter has a lower relative energy of 0.90 kcal/mol in comparison to the former. A density of states (DOS) calculation demonstrates the lowering of the LUMO energy (EL) of Zn@MA-POP by 0.35 and 0.42 eV, respectively, for the two feasible interactions, in comparison to Zn@COM. Moreover, the potential energy profile also unveils the spontaneous and exergonic photoconversion pathways for the SE to SC conversion. Our contribution is expected to spur further interest in the precise design of visible-light-active conjugated porous organic polymers for CO2 photofixation to value-added chemicals.

Photo-induced photo-thermal synergy effect leading to efficient CO2 cycloaddition with epoxide over a Fe-based metal organic framework

It is crucial to design and synthesize a catalyst that can catalyze the production of cyclic carbonates from CO2 and epoxide under mild conditions. Herein, we successfully synthesized a two-dimensional metal organic framework FeTPyP, which displays an outstanding capability to catalyze the CO2 cycloaddition reaction under light irradiation with a yield of styrene carbonate as high as 106.13 mmol/(g h). Characterizations suggests that the major reason is due to (1) the synergistic effect between photocatalysis and thermocatalysis and (2) ultraviolet light can promote the ring-opening reaction of styrene oxide. This work provides an alternative approach to further design efficient heterogeneous catalysts for photo-induced CO2 cycloaddition reaction via coupling thermocatalysis and photocatalysis.

Electrochemically Assisted Cycloaddition of Carbon Dioxide to Styrene Oxide on Copper/Carbon Hybrid Electrodes: Active Species and Reaction Mechanism.

A novel electrochemically assisted cycloaddition process is proposed, in which highly efficient coupling of CO2 with styrene oxide (SO) can be achieved to form styrene carbonate (SC) as a high-value-added product. A series of Cu catalysts with different morphologies and chemical states were fabricated on carbon paper (CP) by using in-situ electrodeposition, and the sample with nano-dendrimer structure was found to exhibit a relatively high activity of 74.8 % SC yield with 92.7 % SO conversion under gentle reaction conditions, thus showing its potential for practical applications. The relatively high electrochemically active surface area and charge transfer ability of dendrimer-like Cu benefited the electrochemical reaction. In particular, the Cu2+ species that were formed in situ during the reaction played a vital role in enhancing the activity and selectivity of the proposed Cu/CP hybrid catalyst. Cu2+ atoms served as active sites that can not only electrochemically activate CO2 but also facilitate the ring opening of SO. Mechanistic analysis suggested that the reaction followed electrochemical and liquid-phase heterogeneous paths, which provide a new green and sustainable route for efficient utilization of CO2 resources for fine chemical electrosynthesis.

Fine-tune simultaneous dearomatization, desulfurization and denitrogenation of liquid fuels with CO2-derived cyclic carbonates

In this work, eight CO2-derived cyclic carbonates, namely ethylene carbonate (Eth-C), propylene carbonate (Pro-C), butylene carbonate (But-C), hexylene carbonate (Hex-C), cyclohexene carbonate (Cyc-C), styrene carbonate (Sty-C), glycerol carbonate (Gly-C) and (Chloromethyl)ethylene carbonate (Chl-C) were evaluated as solvents to mitigate residual aromatic content in liquid fuels by envisioning an efficient liquid–liquid extraction process, using benzene, thiophene and pyrrole as benchmark compounds for dearomatization, desulfurization and denitrogenation processes. After evaluating at molecular scale by COSMO-RS method (activity coefficients and excess enthalpies of aromatic-cyclic carbonate mixtures), predictions of phase equilibria of ternary systems involving n-heptane are carried out by COSMO-based/Aspen methodology for evaluating the extractive properties of studied cyclic carbonates. Then, computational findings are experimentally validated for the representative Pro-C case through multicomponent liquid–liquid equilibria. Finally, the complete separation process was simulated by COSMO-based/Aspen methodology to evaluate solvent losses in extraction and distillation units, energy consumption, and aromatic purity for process specifications aimed at enhancing gasoline purity and recovery. Main results suggest that Pro-C provides promising process performance at a very competitive solvent to feed (S/F) ratio and specific energy consumption, positioning cyclic carbonates for studied separation.

Performance of catalytic cycloaddition of CO2 to styrene oxide in three-phase co-current (micro)fixed-bed and monolith reactors

Synthesis of cyclic carbonates via catalytic cycloaddition of CO2 to epoxides represents one of the most promising green routes for CO2 utilization. The present work investigates, from a multiphase reactor engineering perspective, the design of three-phase catalytic reactors for cycloaddition of CO2 to styrene oxide in the presence of non-deactivating silica-supported pyrrolidinopyridinium iodide catalyst via an exhaustive modeling framework containing a series of isothermal unsteady-state two-dimensional models. A comparative analysis is made for fixed-bed reactors/microreactors and three-phase monolith reactors. The results show a remarkable performance of fixed-bed microreactor which significantly outperforms both fixed-bed and monolith reactors and hold great promise for efficient implementation of CO2 cycloaddition process under relatively mild reaction conditions. At equal liquid space velocity, upflow monolithic reactor outperforms downflow/upflow fixed-bed reactors due to reduced resistance to external and internal diffusion in catalyst pore network, but it would require a higher reactor volume for the same amount of catalyst. A confinement-induced amplification of concentration of CO2 adsorbed on the surface of catalyst generates an enhanced performance of styrene carbonate synthesis process due to increased sorption of CO2. Fixed-bed microreactor generates the smallest confinement-induced performance improvement, possibly because catalytic process is controlled by the considerable improvement in mass transfer.

Cobalt(III) Complexes as Bifunctional Hydrogen‐Bond Donor Catalysts Featuring Halide Anions for Cyclic Carbonate Synthesis at Ambient Temperature and Pressure: A Mechanistic Insight

AbstractThe metal‐templated hydrogen bond donors (HBD) are prospective catalytic systems for the activation of organic molecules in chemical reactions. Here we report the application of the chiral cationic Co(III) complexes based on commercially available (S,S)‐1,2‐diaminocyclohexane and (R,R)‐1,2‐diphenylethylendiamine and salicylaldehydes with an iodide counter‐anion as bifunctional one‐component hydrogen bond donor/nucleophilic catalysts for the conversion of carbon dioxide with epoxides into valuable cyclic carbonates under solvent‐ and co‐catalyst free conditions. We demonstrated that (R,R)‐1,2‐diphenylethylendiamine based complex Λ(R,R)‐2 is superior to (S,S)‐1,2‐diaminocyclohexane based Δ(S,S)‐1 a catalyzing the reaction at ambient conditions (RT and 1 bar CO2). The TON and TOF values of 850 and 35 h−1, respectively, were achieved at low catalyst loading (0.1 mol %) at 10 bars of CO2 and 100 °C. Furthermore, the Co(III) complexes catalyzed the reaction with diluted air/CO2 mixture (15 vol % of CO2) producing the desired styrene carbonate in up to 75% yield. A plausible catalytic cycle consistent with all experimental observations was proposed based on DFT calculations. The DFT calculations elucidated the difference in the ring opening step in cases of propylene oxide and styrene oxide. In addition, the kinetic resolution of terminal epoxides was observed with selectivity factor (s) of up to 1.6 in case of the complex Λ(R,R)‐2.