Propylene Carbonate Selectivity Research Articles

Preparation of Schiff base metal catalyst and its catalytic synthesis of propylene carbonate from CO2

In recent years, research on the conversion of CO2 into fine chemical products has emerged as a prominent and dynamic area of study. In this study, four ligands were synthesized using salicylaldehyde, o-phenylenediamine, ethylenediamine, hexanediamine, and 2,6-diaminopyridine as precursors. Subsequently, these ligands were reacted with cobalt nitrate, zinc chloride, and aluminum chloride to synthesize 12 Schiff base metal complexes, which were employed as catalysts for the synthesis of propylene carbonate from CO2 and epichlorohydrin. The findings reveal that the SF-L/Co catalyst demonstrated superior performance, potentially attributed to the robust chelating capability of Co, leading to the provision of more acidic metal centers. Characterization of SF-L/Co was conducted utilizing scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques. Process conditions were optimized, resulting in the achievement of a 100% yield and selectivity of propylene carbonate under optimal reaction conditions, without the generation of any by-products. Furthermore, the catalyst exhibited remarkable reusability, demonstrating consistent catalytic activity over five successive cycles without a substantial decrease in performance.

Strategic design and facile synthesis of porous hyper-cross-linked phosphonium bromide microspheres for catalyzing CO2 conversion to cyclic carbonates

Heterogeneous ionic liquid (IL) catalysts with multiple active sites can be considered as the highly efficient catalyst for CO2 conversion to cyclic carbonates. It is extremely challenging to achieve the strategic design and precise control of multi-site polymeric ILs’ morphology and properties. In this work, we developed a novel and facile polymerization-ionization method employing flexible brominated monomers as raw materials (e.g. 4‑bromo-1-butene) to successfully synthesize porous hyper-cross-linked phosphonium bromide-microspheres (PBr-microspheres), in order to break through the drawbacks of multi-step preparation and difficulty in microsphere forming. Compared with conventional bromine spheres of the same size, the specific surface area of the new synthetic bromine sphere is 16 times, and the average pore size is one-eighth, with 3-times CO2 adsorption capacity, with rich microporous structure and exposed active sites, excellent CO2 adsorption capacity and thermal stability. PBr-microspheres can achieve synergistic effect of physical adsorption and chemical interaction for CO2, thus enhancing the catalytic performance in CO2 conversion process, affording propylene oxide conversion of 99.7 % and propylene carbonate selectivity of 99.9 %, while the catalytic activity did not decrease significantly after reusing 8 runs. This facile controllable synthesis of PBr-microspheres with excellent catalytic performance provides a new idea for heterogeneous ILs-catalyzed CO2 utilization.

Low-temperature activated porous carbon with functional groups derived from waste tea powder as a potential catalyst for CO2 fixation into cyclic carbonates

The globe is currently confronted with two main environmental problems: environmental solid waste and greenhouse gases. Thus, it is urgent to mitigate these issues and convert them into value-added products. In this context, this work demonstrated the mitigation of two global issues with a single approach. This work established a facile process for a hierarchical porous carbon from abundant bio-waste, such as waste tea powder, and employed it as a heterogeneous catalyst for CO2 fixation into cyclic carbonate. Derived porous carbon catalysts, WTC-1 (Waste tea carbon), WTC-2, AWTC-2-400 (Activated waste tea carbon), AWTC-2a-400, AWTC-2-600, and AWTC-2-800, were produced without the use of solvent by acid-free washing and KOH-free activation. These WTC catalysts were characterized by several standard techniques: XRD, FTIR, XPS, SEM, BET, and TPD. Among the low-temperature activated carbon catalysts, AWTC-2a-400 with potassium-based salt, KI exhibited excellent conversion of propylene oxide (98 %) and ≥99 % selectivity of propylene carbonate without solvent under mild conditions of 2.5 MPa, 120 °C, and 2 h. It was observed that the catalytic activity of the WTC catalyst was attributed to the presence of Lewis acidic and basic sites, CaO/CaCO3, MgO, –COOH/OH, and –NH, which are capable of activating the CO2 molecule. Further, the developed catalytic system (AWTC-2a-400/KI) demonstrated superior catalyst versatility for various epoxides under optimized conditions. Moreover, AWTC-2a-400 showed good stability and reusability. Importantly, all reactions were conducted on a gram scale, and the proposed catalyst was effective, which might be favorable for future industrial applications.

Ionic liquids bonded in mesoporous HAP serve as efficient catalysts for CO2 fixation

In this study, hydroxyapatite (HAP) with abundant surface hydroxyl and large pores was used as the ionic liquid ([DMCA]X) immobilization carrier, where the surface hydroxyl groups of HAP were used as binding sites and the n-halogen-acids were used as bonding agents. The supported ionic liquid catalysts [DMCA]X-n-HAP were characterized by XRD, TEM, TG and FTIR, proving that the ionic liquids were successfully bonded onto the surface of HAP. The utilization of hydroxyl sites on the surface of HAP was as high as 90%. The above catalysts were used to catalyze the cycloaddition reaction of CO2 and propylene oxide (PO), and the yield and selectivity of propylene carbonate (PC) were up to 98.7% and 100%, respectively. The length effect of the bonding agents on the catalyst performance was also studied, and found that n-chlorine-butyric acid was the most suitable chemical for channel structure of HAP and spatial freedom of ionic liquid. In addition, the effects of halogen anion and hydroxyl hydrogen on the performance of the reaction were also studied. Importantly, autocatalysis was discovered in the reaction. Finally, the reaction intermediates and reaction mechanism of CO2 cycloaddition were investigated by in situ-DRIFTS, revealing that ring-open of PO is rate-determining step.

Carbon neutral via catalytic transformation of CO2 into cyclic carbonates by an imidazolium-based ionic zeolitic imidazolate frameworks

On the way toward a carbon–neutral future, anthropogenic chemical recycling of captured carbon dioxide (CO2) into value-added chemicals and reusable materials provides an attractive and promising pathway. A multifunctional zeolitic imidazolate framework (ZIF-9-ImBr) consisting of electrophilic cobalt ions, CO2-philic nitrogen-rich units and nucleophilic imidazolium-based ionic liquids (ILs) was synthesized by simple substitution reaction of amino-functionalized ZIF (ZIF-9-NH2) with 1-(4-bromobutyl)-3-methylimidazolium bromide ([BrBMIM]Br). The obtained ZIF-9-ImBr was employed as heterogeneous catalyst for the solvent-free synthesis of cyclic carbonates from CO2 and epoxides in the absence of any cocatalyst. A certain amount of micropores and abundant nitrogen atoms could facilitate CO2 enrichment and its activation, while the mesopores could enhance the mass transfer of reactant and product molecules. Moreover, the synergistic effect between Lewis-acid cobalt and Lewis-base bromine ions of ZIF-9-ImBr made it promising in the CO2 cycloaddition reaction. As expected, ZIF-9-ImBr displayed good catalytic performance of 93.8 % yield and 98.9 % selectivity of propylene carbonate at 120 °C and 2.0 MPa for 3.5 h. Additionally, the reactions proceeded with a broad substrate scope and high selectivity to give the corresponding cyclic carbonates in good to excellent yields (77.9–95.8 %). Even for the challenging internal epoxide, cyclohexene oxide, a satisfactory 71.4 % yield was obtained by extending the reaction time to 24 h. More importantly, ZIF-9-ImBr can be easily recycled and maintains its reactivity and selectivity after five successive cycles. This work highlights the potential of functional ZIF-based materials for targeting CO2 capture and conversion.

Efficient imidazolium ionic liquid as a tri-functional robust catalyst for chemical fixation of CO2 into cyclic carbonates

The recent increase in CO2 levels has had an extensive impact on the environment; hence an effective catalyst for chemical CO2 fixation into value-added products is demanded. This work demonstrates a simple approach towards the chemical fixation of CO2 to cyclic carbonates without solvent, metal and additives using one-pot synthesized tri-functional-imidazolium bromide ionic liquid. Herein, synthesized tri-functional-imidazolium-based ionic liquids, namely 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium bromide ([VIMEtOH][Br] (24 and 72 h)), 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium hydroxyl ([VIMEtOH][OH]) and poly 3-(2-hydroxyethyl)-1-vinyl-1H-imidazole-3-ium bromide (poly [VIMEtOH][Br]), were used for the comprehensive investigation of chemical fixation of CO2 into cyclic carbonates and their physiochemical properties. In case of [VIMEtOH][Br] ionic liquid, it displayed time-dependent synthesis dissolution in the reaction system. This study found that [VIMEtOH][Br]-72 ionic liquid is not dissolved in the reaction system. The effect on the catalytic efficiency of the presence of functional groups in ionic liquids such as N-vinyl (-CC–N), acidic proton of imidazolium (-C (2)-H) and hydroxyl (-OH) along with bromide anion and the reaction conditions are systematically investigated. For CO2 fixation, 99.6% conversion of propylene oxide with an excellent selectivity of propylene carbonate (≥99%) over [VIMEtOH][Br]-72 catalyst (at 120 °C, 2 MPa, 2 h) was observed without co-catalyst, metal and solvent. Also, it demonstrated an excellent wide substrates scope of epoxide and all reactions were performed on gram-scalable, which are potential prospects for industrial use.

Synergetic effect of ZnCo2O4/inorganic salt as a sustainable catalyst system for CO2 utilization

Currently, it is essential to consider the rapidly increasing emission of CO2 into the atmosphere, causing major environmental issues such as climate change and global warming. In this work, we have developed the binary catalyst system (ZnCo2O4/inorganic salt) for chemical fixation of CO2 with epoxides into cyclic carbonates without solvent, and all reactions were performed on a large scale using a 100 ml batch reactor. Two mesoporous catalysts of ZnCo2O4 with different architecture, such as flakes (ZnCo–F) and spheres (ZnCo–S) were synthesized and utilized as a heterogeneous catalyst for cycloaddition reaction. The bifunctional property of catalysts is mainly attributed to strong acidic and basic properties confirmed by TPD (NH3 & CO2) analysis. The ZnCo–F catalyst exhibited excellent conversion of propylene oxide (99.9%) with good corresponding selectivity of propylene carbonate (≥99%) in the presence of inorganic salt (KI) at 120 °C, 2 MPa, 3 h. In addition, ZnCo–F catalyst demonstrated good catalytic applicability towards the various substrates scope of the epoxide. Furthermore, the catalytic properties were examined by evaluating the reaction parameter such as catalyst loading, pressure, temperature and time. The proposed catalyst exhibited good reusability for cycloaddition reaction without significant change in its catalytic activity and proposed a possible reaction mechanism for chemical fixation of CO2 with epoxide into cyclic carbonate over ZnCo–F/KI.

Efficient Catalysts of Mixed Amino‐Functionalized Ionic Liquids and Zinc Halides for Cycloaddition of CO2to Propylene Oxide without Solvent

AbstractAmino‐functionalized halide ionic liquids, aminopropyl‐3‐butyl‐imidazolium ([Apbim]+) with different halogen anions, and their zinc halide mixing catalysts were prepared and used to catalyze the cycloaddition of CO2to propylene oxide (PO) without solvent. Under ideal conditions, the conversion of PO could reach 93.5 % with the catalysis of [Apbim]Cl. Under optimized conditions of catalyst dosage, reaction temperature, CO2pressure, and reaction time, with the catalysis of [Apbim]I, [Apbim]Cl/ZnBr2(3:1), and [Apbim]Br/ZnBr2(5:1), the conversion of PO and the selectivity of propylene carbonate (PC) both reach > 99 %. From the point of view of preparation process and industrial operation, [Apbim]Cl/ZnBr2is the most suitable catalyst. This catalyst is characterized by good reusability and catalytic activity, and the yield of PC is about 99 % at least for ten times repeated use.

Ionic liquids with multiple active sites supported by SBA-15 for catalyzing conversion of CO2 into cyclic carbonates

Synthesis of cyclic carbonates via cycloaddition reaction by means of CO2 and epoxides has been thought as an effective method for relieving global warming together with resource shortage. In order to elevate the utilization ratio of ionic liquids and separate catalysts easily after reaction, multi-site ionic liquids were designed and then immobilized on SBA-15 for the conversion of CO2 into cyclic carbonates. By combining the advantages of multiple sites and mesoporous channel, in this work, a certain amount of ionic liquids with multiple active sites were firmly immobilized on modified SBA-15. Among all the immobilized ionic liquids, [IMCA]2Br2@SBA-15 presented the best catalytic activity. The result showed high yield (97.4 %) and almost 100 % selectivity of propylene carbonate, which was close to equivalent molar bulk ionic liquids. This superiority could be attributed to the sufficient dispersion of multiple active sites of ionic liquids after being immobilized, enabling efficient use of ionic liquids. Furthermore, the catalyst showed good recyclability after five cycles. By characterization and DFT calculation, the synergistically catalytic mechanism based on multiple sites was proposed.

Amino acids/superbases as eco-friendly catalyst system for the synthesis of cyclic carbonates under metal-free and halide-free conditions

ABSTRACTAn eco-friendly and efficient binary catalyst system of superbases and amino acids was developed for the synthesis of cyclic carbonates from epoxides and CO2 under metal-free and halide-free conditions. Among the various amino acids and superbases systems tested, the L-histidine/1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) system achieved the highest conversion of propylene oxide and selectivity of propylene carbonate. The effect of various reaction parameters was evaluated. A possible catalyst mechanism for L-histidine synergized with DBU in the ring opening of epoxide and DBU introduced CO2 activation. The process herein represents a green, simple, and cost-effective route for the chemical fixation of CO2 into cyclic carbonates.

Melem based multifunctional catalyst for chemical fixation of carbon dioxide into cyclic carbonate

In the present work, melem based catalysts with various functional groups were developed by the modification of melem oligomers and tested for the chemical fixation of CO2 into cyclic carbonates. The characterization of these catalysts, by means of SEM, BET, XRD, IR, TG and XPS, verified the functional groups are successfully incorporated into the melem oligomers structure. Activity test demonstrated that melem oligomers grafted with both hydroxyl and quaternary ammonium groups (MOSB) presented the best catalytic performance. A propylene oxide conversion of 97.4% and propylene carbonate selectivity of 97.8% were obtained under the optimal reaction conditions. The simultaneous existence of edge defects, hydroxyl groups and quaternary ammonium groups in the structure of the catalyst are responsible for the high performance of MOSB. These three groups synergistically catalyzed the chemical fixation of CO2 to proceed with high efficiency. Moreover, moderate yield could still be obtained after five cycles. A possible reaction mechanism was proposed for the cycloaddition of CO2 with epoxides to form cyclic carbonates.

Synthesis of Cyclic Carbonate Catalyzed by DBU Derived Basic Ionic Liquids

In this work, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), 1,5‐diazabicyclo[4.3.0]‐5‐nonene (DBN), and imidazole (MIM)‐derived bromide ionic liquids (ILs) were synthesized and used to catalyze the cycloaddition reactions of carbon dioxide (CO2) with several kinds of epoxides to form cyclic carbonates. The DBU derived bromide ionic liquid system was found to have the best catalytic activity among all the tested ILs. The influences of reaction conditions (including temperature, pressure and reaction time) on the reaction of CO2 to propylene oxide (PO) were studied to show the best conditions of 120 °C, 1 MPa, 2.5 h catalyzed by 2 mol% DBU‐derived bromide ionic liquid, with the conversion of PO and the selectivity of propylene carbonate (PC) reaching 99% and 99%, respectively. Under the optimum reaction conditions, the ionic liquid system could be reused at least five times without decrease in selectivity and conversion. NMR spectroscopy and DFT calculations were used to reveal the hydrogen‐bond interaction between ionic liquids and reagent, based on which the reaction mechanism was proposed.

Synthesis of cyclic carbonates from CO2 and propylene oxide (PO) with deep eutectic solvents (DESs) based on amino acids (AAs) and dicarboxylic acids

A novel synthesis of cyclic carbonates from CO2 and PO with DESs, based on AAs and dicarboxylic acids, was developed. The eutectic mixture of L-proline (L-Pro)/propanedioic acid (PA) system exhibited high activity and selectivity for cycloaddition of carbon dioxide to PO among the prepared DESs. The influencing parameters (reaction temperature, CO2 pressure and time) on yield and selectivity of propylene carbonate (PC) was investigated and optimized. The PC yield of the L-Pro/PA system can reach as high as 98% under optimal conditions. Furthermore, the L-Pro/PA system was readily recovered and reused over 9 times without noticeable decrease in yield and selectivity of PC. The synergistic effect of bromide anion, the AAs and the dicarboxylic acids is perhaps the main reason for the high catalytic activity. In addition, the lengths of carbon chain of dicarboxylic acids play a complicated role in the cycloaddition of CO2 to PO with DESs based AAs and dicarboxylic acids, which may be related hydrogen bond strength.

Thiourea-Based Bifunctional Ionic Liquids as Highly Efficient Catalysts for the Cycloaddition of CO2 to Epoxides

A series of thiourea-based ionic liquids (TBILs) were developed as efficient catalysts for the synthesis of cyclic carbonates by the cycloaddition of CO2 with epoxides under metal-, cocatalyst- and solvent-free conditions. Different substituted groups including electron donating and withdrawing groups were introduced onto the para-position of the aromatic ring in cation of TBILs. The effect of the catalyst structures on the reaction activity was systematically investigated. Among the ionic liquids, TBIL3 with substituted OCH3 group showed the best performance with 99% propylene oxide conversion as well as 99% propylene carbonate selectivity under mild conditions (1.5 MPa, 130 °C and 3 h) without any co-solvent. It was demonstrated that two secondary amine groups of the thiourea unit could dually activate the epoxides and CO2 and have a synergetic effect with the halide anion.

Catalytic Synthesis of Propylene Carbonate from CO2 and Propylene Oxide on Fixed Bed

An efficient catalytic system is developed for propylene carbonate synthesis from carbon dioxide and propylene oxide on fixed bed reactor. The active component screening results make sure that the efficient catalyst is composed of methyl imidazole onium salt, zinc bromide and phenol formaldehyde resin. The prepared catalyst proves 72 h long running with 96 % yield and 98 % selectivity of propylene carbonate. The novel extruded catalyst for PC synthesis used in fixed bed is developed. PR, MimCl and ZnBr2 have the catalytic synergy for the reaction. The catalyst composition is optimized.

Microwave assisted process intensification of lipase catalyzed transesterification of 1,2 propanediol with dimethyl carbonate for the green synthesis of propylene carbonate: Novelties of kinetics and mechanism of consecutive reactions

Green chemistry inherently hinges on process intensification through catalysis and waste minimization. The synergism of enzyme catalysis with microwave irradiation was studied systematically in this work for a consecutive reaction about which no literature report exists. Transesterification reaction of renewable starting materials (1,2 propanediol and dimethyl carbonate) was studied as a new strategy for environmentally benign route of cyclic carbonate synthesis in non aqueous media. A variety of supported enzymes were considered including Lipozyme RM IM, Lipozyme TL IM, Amano and Candida antarctica (Novozyme 435) among which Novozym 435 was the best. Both reactions occur under the influence of enzyme and also are enhanced by microwave irradiation. Thus, the example reported here serves as the first of its kind. The studies cover influence of different process parameters on reaction rate and selectivity of propylene carbonate and include agitation speed, solvent, loading of catalyst, reactant concentration (mole ratio) and temperature. A novel kinetic model was developed by finding forward and backward reaction rate constants for each step of the reaction. Microwave irradiation not only increases reaction rate but also improves the thermal stability of enzyme. Maximum conversion of 93% was obtained in 6h using 250mg of enzyme loading with 1 and 3mmol of 1,2 propanediol and dimethyl carbonate in 15mL solution made up with 1,4-dioxane as solvent at 70°C as compared to 54.4% conversion under conventional heating, thus proving the synergism between microwave irradiation and lipase. The enzyme is reusable and the results are novel.

Ordered Mesoporous Carbon CMK-3 Immobilized with Ionic Liquids as Efficient Catalysts for the Synthesis of Cyclic Carbonates from CO2 and Epoxides

CMK-3-IL heterogeneous catalysts were synthesized using ordered mesoporous carbons CMK-3 as the support to immobilize imidazoles ionic liquids and applied to the synthesis of cyclic carbonate. The catalyst samples were characterized by X-ray powder diffraction( XRD),nitrogen adsorption-desorption,transmission electron microscopy( TEM),thermogravimetric analysis( TGA) and elemental analysis. The results show that the ionic liquids are grafted on the surface of the CMK-3 and the resultant hybrid materials retains mesoporous structure after immobilization. The nitrogen adsorption results indicate that pore volume,pore diameter and surface area of CMK-3-IL are slightly reduced. CMK-3-IL shows much higher catalytic activity. A 64% conversion of propylene oxide and a 99% selectivity of propylene carbonate can be achieved when the catalytic reaction is carried out at 120 ℃ under 2 MPa for 6 h.

ChemInform Abstract: Triethanolamine/KI: A Multifunctional Catalyst for CO2 Activation and Conversion with Epoxides into Cyclic Carbonates.

A catalytic system of triethanolamine/potassium iodide (KI) was proved to be efficient for the chemical fixation of CO2 with epoxide. It was found that triethanolamine with dual function could activate both CO2 and epoxides. Effects of parameters such as catalyst molar ratio and amount, reaction time, pressure, and temperature were studied systematically. As a result, 99% propylene oxide conversion as well as 99% propylene carbonate selectivity could be obtained under the optimal reaction condition. Furthermore, the catalyst was found to be applicable to a variety of terminal epoxides, providing the corresponding cyclic carbonates in good yields and selectivity. Moreover, the catalyst could be reused five times without loss of activity. This work presents an example of a cheap and efficient catalyst for the chemical fixation of CO2 to high-value chemicals, which could help to improve the catalytic efficiency and decrease cost of products for larger applications. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications (R) for the following free supplemental resource: Full experimental and spectral details.]

Triethanolamine/KI: A Multifunctional Catalyst for CO2 Activation and Conversion with Epoxides into Cyclic Carbonates

A catalytic system of triethanolamine/potassium iodide (KI) was proved to be efficient for the chemical fixation of CO2 with epoxide. It was found that triethanolamine with dual function could activate both CO2 and epoxides. Effects of parameters such as catalyst molar ratio and amount, reaction time, pressure, and temperature were studied systematically. As a result, 99% propylene oxide conversion as well as 99% propylene carbonate selectivity could be obtained under the optimal reaction condition. Furthermore, the catalyst was found to be applicable to a variety of terminal epoxides, providing the corresponding cyclic carbonates in good yields and selectivity. Moreover, the catalyst could be reused five times without loss of activity. This work presents an example of a cheap and efficient catalyst for the chemical fixation of CO2 to high-value chemicals, which could help to improve the catalytic efficiency and decrease cost of products for larger applications. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]

Tetramethylguanidine–silica nanoparticles as an efficient and reusable catalyst for the synthesis of cyclic propylene carbonate from carbon dioxide and propylene oxide

Tetramethylguanidine covalently bonded to silica was found to be an efficient and recyclable catalyst for the synthesis of propylene carbonate (PC) from propylene oxide (PO) and carbon dioxide. The catalyst was prepared, first by the coupling of 3-(chloropropyl)triethoxy silane with silica from rice husk ash (RHA), to form 3-chloropropyl silica (RHACCl). This was later grafted with tetramethylguanidine molecule to form a solid base catalyst (RHAPrTMG). The surface morphology analyzed by TEM, revealed the presence of spherical nanoparticles with an average size of 19.62nm. The 13C solid state NMR indicated the presence of 5 sets of carbon atoms in the structure. A conversion of 92% was achieved under the optimized reaction conditions (130°C, 5.0MPa, 8h), with a propylene carbonate selectivity of ca. 98%. The catalyst can be easily recovered by filtration and reused for at least four times without appreciable loss of its catalytic activity.