Search

Porous polymer beads with grafted poly(tertiary amine) were prepared by grafting triethylenetetramine to porous crosslinked poly(methyl acrylate) beads via ester amidation reaction, followed by Eschweiler–Clarke methylation reaction using formaldehyde and formic acid to converting the primary and secondary amine groups to tertiary amines in the beads. The tertiary amine groups in the beads were protonated with hydrochloric acid, hydrobromic acid or hydriodic acid, and the protonated tertiary amine group-containing beads showed high catalytic activity and high selectivity for the formation of propylene carbonate through cycloaddition of propylene oxide with CO2, while free tertiary amine group-containing beads exhibited almost no catalytic activity. The recyclability of the catalyst was studied, and slight loss of the activity was observed after five runs. [ABSTRACT FROM AUTHOR]

With the advantages of low raw material cost and 100% atom utilization, the synthesis of high value-added chemical product cyclic carbonates by the cycloaddition of CO2 to epoxides has become one of the most prospective approaches to achieve the industrial utilization of CO2. In the reported catalytic systems, the complexity of the catalyst synthesis process, high cost, separation difficulties, and low CO2 capture limit the catalytic efficiency and its large-scale application. In this paper, Ag nanoparticles loaded on polyethyleneimine (PEI)-modified UiO-66-NH2 (Ag/PEI@UiO-66-NH2) are successfully synthesized by in situ immersion reduction. The Ag nanoparticles and the amino groups on the surfaces of PEI@UiO-66-NH2 contribute to the adsorption of CO2 and polarization of C–O bonds in epoxides, thereby boosting the conversion capability for the CO2 cycloaddition reaction. At the amount of propylene oxide of 0.25 mol and the catalyst dosage of 1% of the substrate, the yield and selectivity of propylene carbonate are up to 99%. In addition, the stability and recyclability of Ag/PEI@UiO-66-NH2 catalyst are attained. The Ag/PEI@UiO-66-NH2 catalyst also demonstrates a wide range of activity and distinctive selectivity toward cyclo-carbonates in the cycloaddition of CO2 to epoxides. This work provides a guide to designing a highly efficient catalyst for in situ capture and high-value utilization of CO2 in industrial applications. [ABSTRACT FROM AUTHOR]

We introduce expanded perlite as a new, inexpensive, multi-catalytic active site and effective catalyst for the synthesis of cyclic carbonate under perfectly mild, low pressure of CO2 and solvent-free conditions. Expanded perlite efficiently catalyzes the CO2 fixation and achieves high conversion of the main products. The catalyst and products were analyzed using FTIR, X-ray diffraction, XRF, BET, Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and NMR. The catalyst demonstrated impressive output in the synthesis of various cyclic carbonates from epoxides. Epichlorohydrin had the best result and highest performance, transforming 97% of the cyclic carbonate in 4.5 h. This procedure has several advantages including mild reaction conditions, high yields, easy workup, short reaction time, reusability of the catalyst, and non-toxic catalyst. [ABSTRACT FROM AUTHOR]

The selective fixation of CO2 and epoxides into cyclic carbonates offers an atom-economical approach towards promising utilization of anthropogenic CO2 gas. This work demonstrates the development of recyclable organic–inorganic hybrid TBAI@CuO catalyst containing quaternary ammonium (TBAI) salt as active organic groups and CuO flowers as the inorganic component. Initially, CuO flowers was synthesized using a simple oxidation-precipitation method followed by immobilization of TBAI groups using impregnation method. The impregnated TBAI groups functioned as the active basic centers, whereas CuO flowers with effective surface area provided heterogeneity, Lewis acidic sites, facilitated better dispersion and strong interaction of TBAI. Resultantly, hybrid TBAI@CuO catalyst consisted of dual-active sites which played a decisive role in manipulating catalytic activity without requirement of a co-catalyst. With styrene oxide and CO2 as model substrates, the present catalyst system delivered 95% conversion and 97% selectivity towards styrene carbonate under solvent-free and milder reaction conditions when compared to other single metal oxide catalysts. The homogeneously dispersed TBAI groups in strong interaction with CuO flowers provided simultaneous access to both Lewis acidic as well as basic sites and hence resulted in superior catalytic activity. Meanwhile, hybrid TBAI@CuO catalyst showed catalytic adequacy for various terminal and internal epoxides. This catalytic system also presented good reusability without prominent loss in activity and no leaching of active TBAI groups. Based on characterization results, a plausible reaction mechanism was predicted to support the cycloaddition reaction with hybrid TBAI@CuO catalyst. It was proposed that inorganic Lewis acidic CuO activated the epoxide whereas the immobilized TBAI groups activated the inert CO2 molecule and stabilized the epoxide after ring opening. Therefore, the CuO flowers acting in concert with the immobilized TBAI groups showed exceptional acid–base cooperativity and provided high selectivity towards cyclic carbonates. The hybrid TBAI@CuO catalyst in this effort bridges the gap between homogeneous and heterogeneous catalysis for sustainable transformation of CO2 and epoxides to cyclic carbonates under solvent-free and comparatively mild reaction conditions [ABSTRACT FROM AUTHOR]

Polyoxometalates can be tuned for specific catalytic property by substituting transition metal ions. We report the synthesis of hybrid materials of Cu2+, Co2+ and Ni2+ substituted phosphotungstates and poly(diallyldimethylammonium) chloride polymer (PDDA) for CO2 fixation. The in situ generated transition metal substituted polyoxometalates (TMS-POMs) are analyzed by FTIR, powder XRD, 31P NMR and SEM techniques. The hybrid TMS-POM materials are found to be good catalysts for converting epoxides to cyclic carbonates. Among these, PDDA-PWCo is the most efficient catalyst for cycloaddition of CO2 under solvent-free conditions at room temperature in shortest reaction time. Only 0.2 mol% of PDDA-PWCo is enough to deliver 100% conversion and selectivity to cyclic carbonates. This catalytic approach is employed for conversion of other cyclic, acyclic, and aromatic epoxides without using column purifications. Overall, the method of obtaining cyclic carbonates under green conditions using TMS-POMs-PDDA hybrid materials appears suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Chloromethylation of cross-linked styrene-divinylbenzene beads with subsequent quaternization with amines was carried out. The resulting anion exchangers were tested as catalysts for the addition of CO2 to oxiranes and as sorbents for the separation of Zr, Nb, Hf, Ta, and Th salts from nitric acid solutions. The anion exchanger can be used in six catalytic cycles for the reaction of CO2 addition to oxiranes, which led to cyclic carbonates in quantitative yields. [ABSTRACT FROM AUTHOR]

The fixation of CO2 into valuable chemicals under mild conditions is of great importance. Here, we reported an efficient and mild method for the cycloaddition of CO2 to cyclic carbonates. Iodized salt of DBU was used as hydrogen-bonding acceptor, 4-methoxyphenol was employed as hydrogen-bonding donor, and deep eutectic solvent was synthesized and characterized by NMR, FI-IR and thermogravimetric analysis. Optimization of the reaction conditions catalyzed by the deep eutectic solvent was performed, a series of epoxides have been converted to the corresponding products with excellent yields under the optimized conditions. The reaction kinetics for the synthesis of cyclic carbonates was investigated, in addition, excellent recovery performance of the catalyst was obtained after recycling for 5 times. Comparing with the literature reported, the method was much milder and efficient simultaneously. This work provides a promising way to the fixation of CO2. [ABSTRACT FROM AUTHOR]

The conversion of atmospheric carbon dioxide (CO2) gas mixtures and epoxides to cyclic carbonates is an environmentally beneficial execution strategy, which is a useful platform chemical. However, this reaction is overly dependent on harsh reaction conditions including temperature and/or CO2 pressure in the traditional conversion process. We report a series of facilely prepared functionalized ionic liquids (ILs) for the one-pot synthesis of styrene carbonate (SC) from pure/diluted CO2 with styrene oxide (SO). Which achieved a yield up to 99% under atmospheric CO2 conditions. In addition, with the assistance of a small amount of catalyst, the product yield remained at 99% under diluted CO2 conditions. This result demonstrates that functionalized ILs could effectively catalyze the cycloaddition reaction of low-pressure CO2 without any co-catalysts such as metals, organic solvents, and active additives. The density functional theory (DFT) calculations combined with experimental results revealed that the highest catalytic ability of Cat.2 was ascribed to the synergic catalysis between positive charge delocalized cations and Br− anions to efficiently activate the substrates. Furthermore, the best ILs catalyst can be reused five times without significant reduction in catalytic activity, which shows its great potential for chemical conversion of atmospheric CO2. [ABSTRACT FROM AUTHOR]

The effect of structure of alkylammonium halides on the outcome of cycloaddition of carbon dioxide to oxiranes was studied. The conversion of epichlorohydrin to chloromethylethylene carbonate depends nonlinearly on the length of the hydrocarbon chain in the alkylammonium halide catalyst. Tetraethylammonium and benzyltriethylammonium were the most effective cations in the catalyst used. Acetone was the solvent of choice for this reaction under the studied conditions. [ABSTRACT FROM AUTHOR]

In this study, we report a successful strategy for the generation of palladium nanoparticles on porous P-doped carbon spheres with a high surface area. The synthesized Pd/P-CS was used in the CO2 fixation reaction with various epoxides under solvent-free conditions. The prepared Pd0/P-CS nanocatalyst was affirmed by different analysis, including TEM, FE-SEM, EDS, BET, FT-IR, XRD, and ICP-OES. The aforesaid nanocatalyst with a unique porous structure was an outstanding catalytic performance on different substrates toward produce of cyclic carbonates under solvent-free condition with high yields of final products. The catalytic activity of Pd0/P-Cs could be maintained efficiently after recycling up to five consecutive runs under the optimized reaction conditions. [ABSTRACT FROM AUTHOR]

One of the efficient approaches to achieving net-zero greenhouse gas emissions is the 100% atom-economical conversion of the greenhouse gas carbon dioxide (CO2) to cost-effective, less toxic cyclic carbonates that can act as green solvents and abundant C1 synthon in organic synthesis. In this work, we have synthesized an Indium Metal–Organic Framework (MOF), functionalized with triazole MIL-68(In)-NHTr (Tr = 1-methylene-1,2,4-triazole) as a bifunctional catalyst for the synthesis of cyclic carbonates from epoxides with high yield (96%) and selectivity (100%) under solvent-free ambient reaction conditions (CO2 pressure 1 bar, temperature 50 °C, and reaction time 6 h). The synergistic acid–base effect of Indium SBU and the triazole of MIL-68(In)-NHTr make this a better catalyst than the conventional MIL-68(In)-NH2. This new catalyst was non-leachable and was reusable for six consecutive catalytic cycles without appreciable loss in the catalytic efficiency and crystallinity of the MOF framework. [ABSTRACT FROM AUTHOR]

Carbon dioxide is a cheap, easily available, and practically inexhaustible source of synthetic carbon (C1-synthon). Among various transformations of CO2, the synthesis of cyclic carbonates from epoxides and cyclic carbamates from aziridines can be referred to as priority areas in the development of contemporary chemical synthesis and catalysis. Cyclic carbonates found wide application in modern industry (electrolytes, solvents, reagents, polymers) and their use and production will be constantly increased. The development of effective catalytic processes that would allow the synthesis of carbonates under mild conditions (atmospheric pressure of CO2 or lower, temperature 25°C) and low loads of durable and affordable catalysts is at the forefront of research. In the present review we analyze the existing directions of research on the catalytic systems based earth-abundant metals Al3+, Fe2+(3+), and Zn2+ for the synthesis of cyclic carbonates from epoxides and cyclic carbamates from aziridines. [ABSTRACT FROM AUTHOR]

Nowadays, coatings need to fulfill a variety of requirements such as having excellent mechanical, chemical, and optical properties at low baking temperatures. On a large scale, polyisocyanates, amines or melamines are used as crosslinking agents in the coatings industry. In this work, a new self-crosslinking agent based on a hydroxy functional 6-membered carbonate with high ring tension and thus presumably lower baking temperature was synthesized and the behavior as self-crosslinking agent was compared to the crosslinking agent derived from the commercially available 5-membered glycerol carbonate. The hydroxy functional 6-membered carbonate monomer was synthesized enzymatically under mild reaction conditions from commercially available substances, linked to a hexamethylene diisocyanate trimer and self-polymerized afterward. NMR- and IR-spectroscopy and GC-MS analysis were found to be suitable techniques to characterize monomers and crosslinking agents. DSC measurements were performed to evaluate appropriate reaction parameters for the attachment reaction of the 6-membered cyclic carbonate to the polyisocyanate without ring opening. The progress of self-crosslinking has been followed by characteristic changes in IR spectra as well as time and temperature-dependent changes of storage and loss modulus while oscillating rheological crosslinking. Furthermore, glass transition temperatures of the resulting coating films are determined, and sol gel analysis was performed to estimate the degree of crosslinking. After application on steel, aluminum and glass plates application tests were performed. In addition to excellent mechanical and chemical properties, the coating film showed good adhesion to the surface and was colorless. Combining these properties with relatively low baking temperatures, 6-membered cyclic carbonate crosslinking agents could represent a new technology for the coatings industry. [ABSTRACT FROM AUTHOR]

In this study, a new and efficient solvent-less procedure was expanded to synthesize cyclic carbonate derivatives by chemical fixation of CO2 using Cu(II)/hydroxyl terminated triazine-based dendrimer (Cu(II)/TD) as a proficient heterogeneous nano-catalyst. The Cu(II)/TD nano-catalyst was characterized using TEM, TGA, FT-IR, SEM, EDS, and ICP techniques. The application of this new nano-catalyst provides the preparation of assorted cyclic carbonate derivatives in the attendance of 0.045 mol% of nano-catalyst and 0.3 MPa of CO2 pressure at 50 °C under solvent-less situations in outstanding yields. The Cu(II)/TD catalyst was able to be reprocessed and recovered many times without considerable failure of its performance. The findings strongly confirm that Cu(II)/TD can be considered as an environmentally friendly and retrievable catalyst for fixation of CO2 into the valuable products. [ABSTRACT FROM AUTHOR]

This work reports the synthesis of Zinc porphyrin-based porous (POP-ZnTPP) by a typical Yamamoto-Ullmann coupling reaction, which exhibited abundant tiny nanopores, excellent CO2 adsorption capacity, and CO2/N2 selectivity. The open pore environment of POP-ZnTPP facilitated the exposure of active sites, which intensified the catalytic activity in the cycloaddition reaction of epoxides (PO) with CO2 under mild conditions. As expected, POP-ZnTPP catalyst completely converted PO to cyclic carbonates (COCs) at ambient temperature (25 °C, 1.5 MPa). It is also worth noting that POP-ZnTPP could convert PO into COCs under the simulated flue gas (15% CO2 and 85% N2, v/v) atmosphere, which is very favorable for industrial applications of CO2. In addition, POP-ZnTPP catalyst as one of the most outstanding catalysts exhibited excellent broad substrate scope and remarkable reusability. This work has a certain guiding significance for developing an environmentally friendly COC production process. [ABSTRACT FROM AUTHOR]

The current production of organic cyclic carbonates involves the reaction of appropriate alcohols with toxic phosgene. But an alternative route for obtaining these valuable products is the cycloaddition reaction of CO2 with appropriative epoxides. The development of new catalytic systems for this reaction is a highly active field of research works. For this purpose, were developed many effective catalytic systems, such as organocatalysts, metal–organic frameworks, homogeneous metal-based catalysts, and ionic liquid catalysts. Among them, zinc-containing and ionic liquid catalysts are highly active systems, resulting in the increase in selectivity and the beneficial effect on the reaction rate under mild reaction conditions: reaction temperatures of below 100 °C at a low CO2 concentration and pressure at 0.1 MPa, if possible, without solvents and co-catalysts. This review article summarizes and discusses the results of research works over the last 10–15 years on the study of the homogeneous zinc-containing and ionic liquid catalysts for the cycloaddition reaction of CO2 with epoxides. We hope that it can be stimulated for further development in this area and will be useful for understanding the potential commercialization of these catalysts. [ABSTRACT FROM AUTHOR]

Ammonium derivatives of triethanolamine have been effectively used as catalysts for the addition of CO2 to epoxides. The iodine additive was found to exert a positive effect on the catalytic activity of these polyhydroxy-containing salts. [ABSTRACT FROM AUTHOR]

In the present study, we demonstrated the synthesis of copper oxychloride anionic benzotriazolium ionic liquid-modified periodic mesoporous organosilica PMO@ILCu2(OH)3Cl2(x) as efficient and green retrievable heterogeneous nanocatalysts for the synthesis of cyclic carbonates via cycloaddition of CO2 with epoxides. Compared to other nanocatalysts, a superior catalytic activity was observed with PMO@ILCu2(OH)3Cl2(1.0), giving excellent yields and selectivities under solvent- and cocatalyst-free conditions. We also found that the existence of intensification synergistic effects from the hydroxyl groups sites of periodic mesoporous organosilica and the active sites of the functionalized ionic liquid, resulting in the enhanced catalytic activity. The catalytic process displayed ease of recovery, excellent stability and recyclability for at least five runs without significant loss of its catalytic activity. The developed catalytic system is proven to be a powerful tool for the chemical fixation of CO2 with epoxides to produce the cyclic carbonates. [ABSTRACT FROM AUTHOR]

A cationic covalent organic polymer with bifunctional active site was synthesized, which was treated by N, N'-bis(5-bromomethylsalicylaldehyde)ethylenediamine (salen ligand) and tris(1H-imidazol-1-yl) triazine (TIT) in the presence of aluminum ethoxide. The bifunctional cationic covalent organic polymer was investigated by various characterization technologies including PXRD, FT-IR, XPS, TG, SEM, EDS, N2-adsorption and CO2-adsorption. In this polymer, aluminum acts as lewis acid site and bromine ion acts as nucleophile, cooperatively catalyzing the cycloaddition reaction of CO2 and epoxides. Due to its cooperative effect, a higher catalytic activity was found to exhibit 98.1% conversion of epichlorohydrin under optimized conditions (Initial pressure 1.0 MPa, 0.57 mol% catalyst of COP-Al, 90 °C, reaction time 18 h, in the absence of a co-catalyst). Notably, the heterogeneous catalyst still showed good activity and stability after five cycles. A salen-based cationic covalent organic polymers (COP-Al) was used as a bifunctional catalyst for the cycloaddition reaction of CO2 and epoxides with high activity under solvent-free and co-catalyst-free conditions. [ABSTRACT FROM AUTHOR]

A group of available catalysts based on polyethylenimine quaternized with p-xylylene dichloride followed by subsequent exchange of anions was developed. The influence of the nature of halide ions and electronic and steric factors of the substituents in epoxides on the reaction rate of carbon dioxide addition to epoxides was studied. The catalytic capabilities of the adduct of polyethylenimine with iodine were considered. [ABSTRACT FROM AUTHOR]

Sodium and potassium halides in combination with molecular iodine are efficient catalysts for the solvent-free addition of CO2 (10–56 atm) to epoxides giving organic carbonates. [ABSTRACT FROM AUTHOR]

The addition of the oxirane derivatives to CO2 was found to occur without Lewis acid involvement but requires the presence of the Lewis base. The reaction was carried out at atmospheric pressure by CO2 bubbling through the starting ether in the presence of a source of halide anion or trichloroacetate anion, which provides the formation of ethylenecarbonate derivatives in preparative amounts. The reactivity of halide anions in the addition of the studied oxirane derivatives to CO2 decreases in the order I− > Br− > Cl− > F− >> Cl3CCOO−. The quantum chemical calculations of the reaction of CO2 with epichlorohydrin show that the reaction consists of consecutive processes of nucleophilic addition and nucleophilic ipso-substitution, which explains the catalytic effect of the Lewis bases and the order of their activity. [ABSTRACT FROM AUTHOR]

Over many decades, global warming induced by the rising level of atmospheric carbon dioxide appeared to be the point of high concern. Energy demand in running the modern civilisation is mainly fulfilled by combustion of fossil fuels, which, in turn, produces carbon dioxide as a waste. In this respect, capture and fixation of CO2 waste into different value-added products like carbonates, can make the potential shift in the view of carbon dioxide emission. For coupling carbon dioxide and epoxide with formation of carbonates, different metal halides, ionic liquids, ternary alkyl ammonium or phosphonium salts as well as metal complexes are used as active catalysts. This paper presents an overview on Schiff bases and their metal complexes used as catalysts in fixation of CO2 and, hence, its removal from atmosphere within recent twenty years. [ABSTRACT FROM AUTHOR]

An easy-to-prepare recyclable catalyst of quaternary ammonium nature and based on commercially available and inexpensive macroporous polymeric sorbent Purolite A103 resin has been devised for the carbon dioxide addition to epoxides. The catalyst can be easily separated due to its 0.6–0.85 mm bead size and recycled at least seven times. The catalyst makes it possible to carry out the reaction under solvent-free conditions. It is insensitive to the steric and electronic effects of various epoxy substrates. [ABSTRACT FROM AUTHOR]

Onium salt, N1, N1, N1, N5, N5, N5-hexaethylpentane-1,5-diammonium dibromide, was used as a catalyst for the addition of CO2 to epoxides. An influence of insoluble supports on the rate of the process as well as possibility of recycling of the catalytic system are described. In addition, the effects of temperature and CO2 pressure on the yields of products are discussed. [ABSTRACT FROM AUTHOR]

On the basis of efficient and recyclable criteria for catalytic conversion of CO2 into cyclic carbonates, functionalized polymeric ionic liquids grafted onto the silica (PIL@SiO2) are explored by the polymeric method herein. Among all the prepared PIL@SiO2, the PIL@SiO2 loaded with a high mass fraction (50%) of PIL is the best in catalytic activity, achieving 91% PO conversion, nearly 50% saved than the non-grafted PIL. In addition, the PIL@SiO2 exhibits higher performance than PILs under identical reaction conditions. Subsequent studies concerning recyclability confirm that the as-prepared catalyst is stable after 5 times recycle without obvious loss in activity. This grafting and polymerization process provides an efficient and sustainable way of CO2 conversion in the long term. [ABSTRACT FROM AUTHOR]

A complex study of sodium and potassium halides as catalysts of the addition of CO2 to epoxides to yield organic carbonates was carried out. The activity of these metal iodides was investigated. The conditions allowing achievement of a quantitative conversion of epoxides into carbonates were found by varying the temperature, carbon dioxide pressure, and available co-solvents. [ABSTRACT FROM AUTHOR]

The catalytic systems based on metal porphyrin complexes used for promoting the reactions of olefin oxides with carbon dioxide were reviewed. The metal porphyrin complexes were shown to be effective catalysts for carboxylation of epoxides. The catalyzed reactions of oxiranes with carbon dioxide in the presence of homogeneous and heterogeneous metal porphyrin complexes, including the reactions with the use of various promoting additives, were considered. [ABSTRACT FROM AUTHOR]

Silica gel with the additives of tetraalkylammonium halides serves as an efficient catalyst for the solvent-free insertion of carbon dioxide into epoxides (10–56 atm of CO2, 105–100 °C), leading to cyclic carbonates with quantitative conversion. [ABSTRACT FROM AUTHOR]

Silica gel with the additives of tetraalkylammonium halides serves as an efficient catalyst for the solvent-free insertion of carbon dioxide into epoxides (10–56 atm of CO2, 105–100 °C), leading to cyclic carbonates with quantitative conversion. [ABSTRACT FROM AUTHOR]

In this study, the various ligands axially coordinated to two cobalt center bound to the N-oxime core in 12 new dicobaloxime/organodicobaloxime (1-12) complexes have been synthesized and characterized by NMR (H and C), UV-Visible, FT-IR, LC-MS, molar conductivity analysis, melting point, and magnetic susceptibility experiments with elemental analysis. These spectroscopic results indicate that the formation of new dicobaloxime/organodicobaloxime (1- 12) complexes. The (C=N-O H) peaks disappeared in the H-NMR spectrum of dicobaloxime/organodicobaloxime (1- 12) complexes, while new peaks were observed at range 20.18-18.33 ppm, indicating that the groups of ligands have been transformed to intramolecular H-bridge (O- H⋯O). The dicobaloxime (1- 6) species give a better cyclic voltammogram as compared to its organodicobaloxime derivatives (7- 12) due to cyclic voltammograms of the organodicobaloximes (7- 12) were poor. This is possibly due to the enhanced σ donation by R groups in the organocobaloximes which are substantially stabilized. The organodicobaloxime (10) showed much better catalytic activity compared to the other cobaoxime complexes. Graphical Abstract: The different dicobaloxime (1- 6) and organodicobaloximes (7- 12) have been synthesized for the first time. Their redox properties were investigated using cyclic voltammetric (CV) techniques in a DMSO solution. These dicobaloximes/organodicobaloximes have been used as homogeneous catalyst for synthesis of cyclic carbonates presence of DMAP as co-catalyst. [ABSTRACT FROM AUTHOR]

Pyridine-containing anion-based ionic liquids (PA-ILs) with two kinds of interaction sites to bind CO, e.g., [P][2-OP], were found to be highly efficient for catalysing the cycloaddition reactions of atmospheric CO with epoxides at room temperature under metal- and halogen-free conditions, producing a series of cyclic carbonates in high yields. It was demonstrated that the cooperative interaction from two interaction sites in the anions of PA-ILs activated CO, while the cation activated the epoxides substrates via coordination to the central P unit, thus resulting in the high activity of the IL catalysts. [ABSTRACT FROM AUTHOR]

An effective direct method for preparing of cyclic carbonates from CO and olefins in the presence of tert-butyl hydroperoxide as an oxidant was provided. The first stage, the epoxidation of olefins, was carried out using MoO(acac) as a catalyst (1h, 100 °C), and the second stage, the cycloaddition of CO to the resulting epoxide, was proceeded in the presence of immobilized tributylmethylammonium chloride on a polystyrene cross-linked with divinylbenzene, and an aqueous solution of ZnBr (100 °C, 0.9 MPa of CO, 4 h). The proposed method allowed to obtain cyclic carbonates with high yields (50-77%) under mild conditions. Moreover, the immobilized catalyst could be reused at least five times without significant loss of its catalytic activity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A review of catalytic systems based on ionic liquids used for promoting reactions between olefin oxides and carbon dioxide is presented. It is shown that ionic liquids based on imidazoles, pyridines, quaternary ammonium salts, and other compounds exhibit high activity in these processes and can serve as alternatives to conventional catalysts of cyclocarboxylation of olefin oxides under certain conditions. Specific features of the reactions between oxiranes and carbon dioxide in the presence of ionic liquids are considered, including reactions with the use of promoting additions based on metal salts. Mechanisms of the catalytic action of ionic liquids in syntheses of cyclocarbonates are described. Other works are critically analyzed to develop new lines in the catalysis of cyclocarboxylations of olefin oxides with ionic liquids. [ABSTRACT FROM AUTHOR]

The ring-opening polymerizations (ROP) of five-, six-, and seven-membered ring cyclic substrates, as well as the transesterification of acyclic esters, with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst precursor in the presence of methanol as an initiator were investigated using density functional theory calculations at the B3LYP/6-311G(d) level of theory. The calculated energy barriers for the ROP are in the range from 12.5 to 21.5 kcal/mol. By analyzing the energy profiles, the overall polymerization process can be classified into exergonic for trimethylene carbonate, tetramethylene carbonate, caprolactone and 1,4-dioxane-2,5-dione, almost athermic for valerolactone, energetically unfavorable for 1,4-dioxanone, and thermodynamically forbidden for ethylene carbonate and gamma-butyrolactone. The study of the kinetics of ROP of cyclic substrates and transesterification of acyclic esters using the TBD-benzyl alcohol catalyst demonstrated that the experimentally determined rate constants for the reactions of cyclic substrates are qualitatively correlated with the calculated activation barriers. It was also experimentally found that TBD efficiently catalyzes the irreversible cyclization to give ethylene carbonate and gamma-butyrolactone, the catalyst productivity being 2-3 orders of magnitude higher than that of conventional basic catalysts. The obtained results confirm that the donor-acceptor mechanism is common for different ester-type substrates. [ABSTRACT FROM AUTHOR]

The catalytic applicability of ionic liquids immobilized on various support materials such as silica, polystyrene and biopolymers in the cycloaddition of carbon dioxide with epoxides is reviewed in this work. Comparisons of the catalytic efficiency of these various catalysts have been done from the aspect of turnover number and reusability. The studies revealed that ionic liquids or support materials possessing hydrogen bonding capable groups exhibited enhanced catalytic activity towards cyclic carbonate synthesis. Moreover, the increased quest towards environmentally benign materials has renewed the search for biocompatible materials as support for ionic liquids. [ABSTRACT FROM AUTHOR]

The synthesis of cyclic carbonates or dimethyl carbonate (DMC) using CO as a building block is a very interesting topic. In this work, we found that the metalorganic framework-5 (MOF-5)/KI was an active and a selective catalytic system for the synthesis of cyclic carbonates from CO and epoxides, and MOF-5/KI/KCO was efficient for the preparation of DMC from CO, propylene, and methanol by a sequential route. The impacts of temperature, pressure, and reaction time length on the reactions were investigated, and the mechanism of the reactions is proposed on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

Synthesis of various cyclic carbonates with yield up to 100% and turn over frequency (TOF) of 351 h−1 using CO2 and epoxides and a cobalt (III) complex of tetraamidomacrocyclic ligand is described. The catalyst was characterized by single crystal X-ray crystallography. A study of reaction conditions indicates that 2 MPa pressure of CO2 without any co-solvent is sufficient to achieve the desired product. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The coupling reaction of carbon dioxide with epoxides was investigated using naturally occurring α-amino acids as the catalyst in supercritical carbon dioxide and it was found that L-histidine is the most active catalyst. In the presence of 0.8 mol% of L-histidine at 130 °C under 8 MPa of CO2, the reaction of carbon dioxide with epoxides proceeded smoothly, affording corresponding cyclic carbonates in good to excellent yields. [ABSTRACT FROM AUTHOR]

Supported liquid phase catalysts (SLPC) were prepared from high surface area porous silica, polyethylene glycol (PEG), alkali metal halides and used for the synthesis of cyclic carbonates from carbon dioxide and epoxides. These catalysts was found to be highly active and selective for the synthesis of cyclic carbonates. The catalytic activity strongly depends on the nature of the supported alkali metal halide. The amount of alkali metal salt incorporated in the catalyst is one of the most important factor governing the catalytic performance. Effect of various reaction parameters such as pressure, temperature, catalyst loading, surface area of support was also studied in detail. [ABSTRACT FROM AUTHOR]

Metal phthalocyanine complexes (MPc; M = Cu2+, Co2+, Ni2+ and Al3+) encapsulated in zeolite-Y exhibit high catalytic activity for the cycloaddition of CO2 to epichlorohydrin and propylene oxide yielding the corresponding cyclic carbonates. The catalysts could be separated easily from the reaction mixture and reused with little loss in activity. These environmentally benign catalysts are also more efficient than either the “neat” complexes or those obtained by supporting them on solids like silica. [ABSTRACT FROM AUTHOR]

The sequestration of atmospheric CO2 into value-added products is of great interest from economic and environmental perspectives. The tetra-shelled Cr1.3Fe0.7O3 hollow sphere as a heterogeneous catalyst was synthesized by a simple hydrothermal method followed by calcination at 600 °C. The synthesized tetra-shelled hollow spheres were characterized by several effective tools. The catalytic performance was studied for the cycloaddition reaction of CO2 with epoxides under solvent-free conditions. The reaction time, reaction temperature, CO2 pressure, and the catalyst amount were systematically studied. Under the best-experimented condition ( 0.02 g of the catalyst, 80 °C, 6 h, and 4 bar CO2 pressure), the catalyst demonstrated a broad substrate scope and functional group tolerance. Besides, the catalyst showed high recycling efficiency for five consecutive reaction cycles with no significant decline in activity. [ABSTRACT FROM AUTHOR]

Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO2 with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10–35 bars and temperatures of 100–150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbonates, in the presence or absence of a solvent. The selectivity of the catalytic system could be improved with heat pre-treatment of the phyllosilicates albeit this resulted in slightly lower epoxide conversion. The results obtained using the heat treated phyllosilicates strongly support the hydrogen bond assisted mechanism for the cycloaddition of epoxides and CO2. The cycloaddition reaction could also be carried out in the absence of TBAB, although lower cyclic carbonate yields were observed. The phyllosilicate part of the catalyst system is heterogeneous, easy to separate after completion of reactions and reusable a number of runs without loss of activity. [ABSTRACT FROM AUTHOR]