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Greener synthesis of dimethyl carbonate from carbon dioxide and methanol using a tunable ionic liquid catalyst

  • Atul A. Pawar , Avinash A. Chaugule and Hern Kim EMAIL logo
Published/Copyright: December 31, 2019
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Open Chemistry
From the journal Open Chemistry Volume 17 Issue 1

Abstract

Several types of ionic liquids (ILs) performance towards dimethyl carbonate (DMC) synthesis using cheap reactant (methanol) and waste CO2 which is abundantly available in the environment are discussed. We synthesized ILs with cheap raw materials such as ethylene glycol. The main aim of this study is to synthesize efficient catalysts for the production of profitable fuel additives. ILs show high thermal stability, less viscosity, and low vapor pressure. In addition, some ILs have high CO2 absorption capacity due to moderate acid-base properties. These ILs reversibly capture more CO2 which is more efficient towards mass transport of methanol at optimum reaction conditions which enhance the DMC yield. This catalytic system is easily reusable for several reactions without decreased performance under the same reaction conditions. These reaction conditions had an effect on the synthesis of DMC. Temperature, pressure, IL loading, and IL/DMAP ratio were fine tuned. We propose a mechanism which the reaction may follow. The synthesized ILs required moderate reaction conditions and reduce waste gases (CO2) from the environments as they have high CO2 absorption capacity compared to the metal oxide catalyst. Therefore, this catalytic system helps and gives new direction to synthesize new catalyst for other application.

Graphical Abstract

Keywords: CO2; ILs; dehydrating agent; reaction mechanism

1 Introduction

Carbon is one of the most abundant elements on earth and it is the key element in fuels and polymers. It is important for industry and transport, and thus the economy [1]. In recent decades, the conversion of carbon dioxide (CO2) into useful chemicals has attracted much attention because it is non-toxic and comes from a renewable source [2].

One of the most efficient ways to use CO2 as a raw material is in the synthesis of linear carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC). Most researchers who have conducted experiments on CO2 utilization have investigated hydrogenation of CO2, cycloaddition of CO2 and epoxides, and reduction of CO2 under photochemical or electrochemical conditions [3]. Traditionally, DMC is synthesized by phosgenation, the drawbacks of this process include the use of highly toxic and corrosive phosgene gas and the formation of large amounts of inorganic salts [4]. The four known processes used for DMC synthesis are: (i) oxidative carbonylation, (ii) a two-step process including carbon monoxide (CO) and nitric oxide (NO), (iii) transesterification of ethylene carbonate (EC) and propylene carbonate (PC) with methanol (MeOH), and (iv) direct synthesis of DMC from CO2 and MeOH. The first two processes use toxic gases such as CO and NO which are harmful to nature. The transesterification of EC and PC with MeOH produces DMC and a useful byproduct (ethylene glycol). There are limitations to this route: harsh reaction conditions, expensive precursor, and there is no utilization of CO2. The direct synthesis of DMC from CO2 and MeOH is a superior route from the viewpoint of green chemistry because of the relatively cheap raw material (MeOH) and water (H2O) is the main byproduct [5].

With this in mind we pursued the direct synthesis of DMC from CO2 and MeOH. Different types of catalysts have been reported in DMC synthesis such as: organotin [6], copper-based catalysts [7], homogeneous and heterogeneous catalysts [8,9], organometallic complexes [10], phosphines [11], organic bases [12], metal oxides [13, 14, 15], acid-base bifunctional systems [2], zeolite-smectite catalysts [12], and supported organic base catalysts [16]. However, many of these catalytic systems require extreme reaction conditions and produce low yields. Low catalyst stability and/or reactivity and low methanol conversions are also common due to the inertness of CO2 and deactivation of the catalyst. DMC on the other hand has low toxicity, is non-corrosive, and is biodegradable [17]. DMC can be used as a precursor for polycarbonate synthesis, in the polyurethane manufacturing industry, as an electrolyte in lithium-ion batteries, as an alkylating and carbonylating agent, and as polar aprotic solvent [18, 19, 20]. According to the literature several types of ionic liquids (ILs) have been used for the synthesis of DMC instead of metal oxide catalysts as ILs possess high CO2 absorption capacity at moderate reaction conditions, they are ionic compounds (organic salt) and are liquids below 100°C or even at room temperature. ILs can be used in different organic synthesis reactions due to their chemical and thermal stability, negligible vapor pressure, recyclability, high solubility in polar and non-polar solvents [21], non-flammability, mechanical and electrochemical backbone, and high electrical conductivity. Moreover, ILs are useful in electrochemical applications, extraction reactions, gas separations, carbohydrate dissolution, polymer chemistry, as anti-microbial and anti-electrostatic agents, in activation and stabilization of biomolecules, and nanoscience technology [22,23,32,24, 25, 26, 27, 28, 29, 30, 31]. The main drawbacks of DMC production are the formation of significant amounts of H2O in the reaction mixture and low DMC yield. There are two practical solutions to these issues: an equilibrium shift towards products by increasing the CO2 pressure and developing adequate dehydrating agents or synthesized active catalysts. According to this literature review more novel active materials need to be developed which are easy to prepare and are low cost. Binary and ternary catalysts are used in the DMC synthesis which are more toxic to the environment due to their degradation and therefore there is a need to develop a single component catalytic system for DMC synthesis.

Various kinds of imidazolium-based monocationic and dicationic ILs are reported for DMC synthesis. Their main limitations are low yield, low CO2 solubility, toxicity and their expensive precursors. Thus, in this study we focused on improving the precursor and the DMC yield. The ILs were synthesized using cheap, easily available, biodegradable materials (ethylene glycol). The cation selected was vinyl-imidazole because of availability, moderate acidic properties, and easy polymerization capability. The anion was Bis (trifluoromethane) sulfonimide [NTf2]-, as it has high CO2 absorption capacity, it reacts with CO2 forming [NTf2----CO2], a new anionic intermediate which is more basic than the original anion. The interaction between [NTf2]- and MeOH is much greater than with the bulky and charge- delocalized anions BF4 and PF6 [33,34]. The cationic and anionic parts form a synergistic link and capture more CO2 [35]. The synthesized ILs are considerably reactive in DMC synthesis. We tested the CO2 solubility in reaction mixture with and without ILs and concluded that ILs can dissolve more CO2 in the reaction mixture. [36].

The dehydrating agent, 4-dimethyl amino pyridine (4-DMAP), is effective in absorbing H2O from the reaction mixture. There are various amine containing moieties similar to DMAP such as 4-(pyrrolidin-1-yl) pyridine (4-PYP) and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) (pKa 13.5). The disadvantage of using these different bases is that they form a large amount of polycarbonate (byproduct of DMC). Therefore the yield of dimethyl carbonate (DMC) decreases due to high basicity [37]. In the case of 4-DMAP, which is less basic (pKa 9.6) than the aforementioned different bases, 4-DMAP is planar and an ideal Lewis base [38]. Chiral DMAP was recently employed for a number of enantioselective organic reactions due to its steric bulk, electron donating nature, and ability to attract moisture [39]. Herein, we report new di-cationic ILs for the synthesis of DMC which have the ability to adsorb large amounts of CO2 and thus results in better yield and higher selectivity as compared to the metal oxide and monocationic ILs catalytic systems.

The single component catalytic system reveals a remarkable performance and good thermal strength and therefore we were able to easily synthesize DMC at adequate reaction conditions. Moreover, the ILs need an easy synthesis method, no addition of metal oxide complexes and at ordinary reaction conditions the yield of DMC was higher. Therefore, here we report the three classes of Lewis acidic ILs for the synthesis of DMC. To the best of our knowledge, there is no report available based on the EG[Vim]2[NTf2]2 ILs.

2 Experimental section

2.1 Materials

1-Vinyl imidazole, Mesyl chloride (MsCl), acetonitrile (CH3CN), dichloroethane (DCE), dichloromethane (DCM), methanol (MeOH), bis(trifluoromethanesulfonyl) imide lithium salt, potassium hexafluorophosphate, 2-cyanopyridine, 4-dimethyl aminopyridine (DMAP), 1,8-diazabicyclo [2.2.2] undec-7-ene (DBU), triethylamine, ethylene glycol, potassium bromide (KBr), sodium dicyanamide, sodium sulphate, and carbon dioxide gas (99.999%) were purchased from Alfa Aesar. All chemicals were purchased at 99% purity and used as received without further purification.

2.2 Characterization and measurements

The synthesized ILs were characterized by a different spectroscopic techniques such as 1H NMR, 13C NMR, and FT-IR analysis. NMR spectra were recorded in DMSO-d6 on 400 MHz and 100 MHz spectrometers using TMS as an internal standard. The FT-IR spectra of samples were recorded using a Varian 2000 (scimitar series) spectrophotometer. A spectrum was recorded from 4000 to 500 cm−1 maintaining a resolution of 4 cm−1 with 32 scans in transmittance mode. Thermogravimetric analysis (TGA, model SCINCO, N-1000) was used for thermal study of ILs from 25 to 600°C, with a heating rate of 10°C/min under inert gas (N2) (50 mL/min). The crystallization temperature of ILs was studied using differential scanning calorimetry (DSC) Mettler DSC 822 instrument in a sealed platinum pan with 10°C/min heating and cooling rate, under N2 gas (50 mL/min). The viscosity of ILs was calculated using Brookfield model DV-II+ programmable viscometer connected with water jacket and temperature measuring device.

2.3 Synthesis of new ILs

2.3.1 Preparation of ethylene glycol dimesylate (EG[OMs]2) precursor

In brief, in a round bottom flask containing 1.0 mmol of ethylene glycol and 2.1 mmol of tri-ethylamine was mixed with 20 mL dichloromethane (DCM) with vigorous stirring. The reaction mixture was then cooled to 0°C for 30 minutes in an ice bath. Mesyl chloride was added dropwise with constant stirring over a period of 15-20 minutes under an inert gas atmosphere. The reaction mixture was then warmed to 30°C for 12 hours. The reaction progress was monitored by thin layer chromatography (TLC) using mobile phase ethyl acetate: hexane (70:30) ratio. After 12 hours the reaction was quenched with H2O followed by extraction using 50:50 H2O and DCM, the synthesized ionic liquids were dried with inorganic salt (sodium sulphate). The organic layer was concentrated under reduced pressure. The resulting product, ethylene glycol dimesylate (EG[OMs]2), was isolated as a white crystalline solid then dried under vacuum at 30 °C for 24 hours (Yield 89.4%) (Scheme 1). 1H NMR (400 MHz, DMSO-d6): ∂ 2.97 (6H, s), 4.34 (4H, t). FT-IR (500-4000 cm−1): 793 cm−1 (S-O), 1166-1326 cm−1 (S=O), 2945 cm−1 (C-H). 13C NMR (100 MHz): 37.37, 67.40.

Scheme 1 Synthesis of EG-di (1-vinyl imidazolium dimesylate RTILs.
Scheme 1

Synthesis of EG-di (1-vinyl imidazolium dimesylate RTILs.

2.3.2 Synthesis of ethylene glycol (EG)-di (1-vinyl imidazolium) dimesylate IL EG[Vim]2[OMs]2

1.0 mmol dimesylate precursor and 2.1 mmol 1-vinyl-imidazole were added to a round-bottom flask containing 20 mL acetonitrile. The reaction mixture was refluxed under inert gas atmosphere at 80°C for 72 hours and then was slowly cooled to room temperature. The solvent was removed under vacuum followed by ethyl acetate washing to remove unreacted starting material and the product was dried under vacuum at 30°C for 12 hours. The obtained product is EG-di (1-vinyl imidazolium) di-mesylate IL in Quasi-solid (solid-liquid mixture) form (Yield 90.4%) (Scheme 1). 1H NMR (400 MHz, DMSO-d6): ∂ 2.32 (6H, s), 4.75 (4H, s), 5.39-5.41 (2H, d), 5.91 5.95 (2H, d), 7.26-7.32 (2H, m), 7.80 (2H, s), 8.20 (2H, s), 9.50 (2H, s). FT-IR (500-4000 cm−1): 1162-1343 cm−1 (S=O), 1454 cm−1 (-CH2 bend), 1564 cm−1 (N-H), 1645 cm−1 (C=N), 3001 cm−1 (Ar-H), 3104 cm−1 (=CH2 stretch vibration). 13C NMR (100 MHz): 40.23, 49.95, 109.33, 119.68, 123.81, 129.37, 136.79.

2.3.3 Synthesis of ethylene glycol (EG)-di (1-vinyl imidazolium) bis (difluoromethanesulfonyl) imide IL EG[Vim]2[NTf2]2

To a round-bottom flask 0.17 mol glycol-di (1-vinyl-imidazolium) di-mesylate, 0.34 mol bis (trifluoromethanesulfonyl) imide lithium salt was added to 20 mL acetone. The reaction mixture was stirred at room temperature for 72 hours under N2 gas, after which it was washed with acetone to remove any unreacted salt. The resulting Quasi-solid product was dried under vacuum at 60°C for 6 hours (Yield 89.2%) (Scheme 2). 1H NMR (400 MHz, DMSO-d6): ∂ 4.70 (4H, s), 5.40-5.42 (2H, d), 5.88-5.92 (2H, d), 7.25-7.31 (2H, m), 7.73 (2H, s), 8.15 (2H, s), 9.36 (2H, s). FT-IR (500-4000 cm−1): 1132-1340 cm−1 (S=O), 1457 cm−1 (-CH2 bend), 1561 cm−1 (N-H), 1664 cm−1 (C=N), 3101 cm−1 (Ar-H), 3149 cm−1 (=CH2 stretch vibration). 13C NMR (100 MHz): 39.85, 49.13, 109.29, 119.65, 123.75, 129.26, 136.61.

Scheme 2 Synthesis of several anions containing RTILs.
Scheme 2

Synthesis of several anions containing RTILs.

2.3.4 Synthesis of ethylene glycol (EG) -di (1-vinyl imidazolium) hexafluorophosphate IL EG[Vim]2[PF6]2

Quasi-solid (Yield 87.1%) (Scheme 2). 1H NMR (400 MHz, DMSO-d6): ∂ 4.69 (4H, s), 5.41-5.43 (2H, d), 5.88-5.91 (2H, d), 7.26-7.28 (2H, m), 7.72 (2H, s), 8.16 (2H, s), 9.32 (2H, s). FT-IR (500-4000 cm−1): 1184-1369 cm−1 (S=O), 1439 cm−1 (-CH2 bend), 1561 cm−1 (N-H), 1657 cm−1 (C=N), 3030 cm−1 (Ar-H), 3164 cm−1 (=CH2 stretch vibration). 13C NMR (100 MHz): 39.89, 49.12, 109.42, 119.67, 123.74, 129.29, 136.60.

2.3.5 Synthesis of ethylene glycol EG -di (1-vinyl imidazolium) dicyanamide IL EG[Vim]2[N(CN)2]2

Quasi-solid (Yield 92.6%) (Scheme 2). 1H NMR (400 MHz, DMSO-d6): ∂ 4.69 (4H, s), 5.41-5.43 (2H, d), 5.89-5.92 (2H, d), 7.25-7.32 (2H, m), 7.73 (2H, s), 8.18 (2H, s), 9.33 (2H, s). FT-IR (500-4000 cm−1): 1170-1310 cm−1 (S=O), 1450 cm−1 (-CH2 bend), 1550 cm−1 (N-H), 1649 cm−1 (C=N), 2196-2240 cm−1, (C N) 3079 cm−1 (Ar-H), 3149 cm−1 (=CH2 stretch vibration). 13C NMR (100 MHz): 39.93, 49.13, 109.43, 119.68, 123.78, 129.32, 136.63.

2.4 Linear carbonate production

2.4.1 DMC production from CO2 and MeOH

Dimethyl carbonate (DMC) production from methanol (MeOH) and carbon dioxide (CO2) (Scheme 3) was performed in a batch reactor connected to a stainless steel (SS) reaction vessel (100 mL) with a heating coil and mechanical stirrer. The reaction vessel contained 20 g (625 mmol) of MeOH, EG[Vim]2[NTf2]2 IL 1.28 mmol, DMAP 4.10 mmol under 6.5 MPa CO2 pressure and at 130°C. The reaction mixture was constantly stirred at 850 rpm for 6 hours after which it was cooled in an ice cold water and slowly depressurized to remove the unreacted CO2. The IL/DMAP was separated under reduced pressure. The liquid phase of product (DMC) was analyzed by gas chromatography (GC-17A, SHIMADZU) using capillary column (STABILWAX, 30 m length, 0.53 mm ID, 1 mm film thickness) and a flame ionization detector (FID). Furthermore, the product was identified using FT-IR (supporting information Figure 3).

Scheme 3 Synthesis of DMC in the presence of vinyl-imidazolium RTILs.
Scheme 3

Synthesis of DMC in the presence of vinyl-imidazolium RTILs.

Figure 1 Thermogravimetric (TGA) analysis of synthesized di-cationic RTILs.
Figure 1

Thermogravimetric (TGA) analysis of synthesized di-cationic RTILs.

Figure 2 Differential scanning calorimetry (DSC) analysis of synthesized di-cationic RTILs.
Figure 2

Differential scanning calorimetry (DSC) analysis of synthesized di-cationic RTILs.

Figure 3 Viscosity of synthesized di-cationic RTILs at different temperatures.
Figure 3

Viscosity of synthesized di-cationic RTILs at different temperatures.

Ethical approval: The conducted research is not related to either human or animal use.

3 Results and discussion

3.1 Thermal properties of ILs

The thermal degradation pattern of the ILs was examined by thermal gravimetric analysis (TGA) and the crystallization temperature was studied by differential scanning calorimetry (DSC) under N2 gas from 25 to 600°C at a heating rate of 10°C/min. A slower heating rate results in a more accurate thermal degradation pattern [40,41] and in TGA if the heating rate is higher than 10 °C/min the decomposition temperature will not be accurate [42]. The decomposition pattern depends on a number of factors such as the viscosity of ILs, heat capacity, the nature of the cation and anion, IL geometry, and total molar mass of the ILs [43]. The thermal pattern of room temperature ionic liquids (RTILs) is shown in Figure 1 and demonstrates that the synthesized ILs are stable up to 300°C. Thermogram of EG[Vim]2[OMs]2 IL shows weight degradation from 70 to 170°C which is attributed to the hydrophilic nature of ILs. When the temperature is increase above 170°C the decomposition of the imidazole compounds occurs. The EG[Vim]2[PF6]2 IL is stable up to 230°C due to its hydrophobicity, intramolecular interactions, high molecular mass, more density, and high viscosity. Similarly, for EG[Vim]2[N(CN)2]2 IL thermal degradation starts at a low temperature because, polymerization of the dicyanamide anion takes place [44]. The thermal degradation of EG[Vim]2[NTf2]2 IL shows 10% weight loss at 70°C due to the decomposition of mesylate anions. A 90% weight loss was evident between 250 and 350°C as a result of the decomposition of the vinyl-imidazole cation. The [NTf2]- anion containing RTILs have a wider liquid range and higher thermal stability than other anionic compounds [45]. The geometrical dicationic ILs are thermally stable above 300°C unlike most traditional monocationic ILs [46]. Figure 2 illustrates the DSC curve of dicationic ILs from -25 to 200°C. The EG[Vim]2[NTf2]2 IL is in a quasi-solid state at room temperature with the glass transition temperature observed at 100°C and the crystallization temperature observed at 125°C. Further heating did not result in the observation of further changes because of the stable nature of IL and the presence of the [NTf2]- anion which conveys high thermal stability. The [NTf2]- anion is water repellent (insoluble in water). Therefore, ILs absorb minimal amounts of water from the atmosphere and therefore the ionic liquids is insoluble in water. Therefore, the interaction between cation and anion is less. This is the main reason for the high thermal stability of ionic liquids at higher temperature. Therefore, according to the DSC results the ionic liquids is in Quasi-solid state [47].

3.1.1 The viscosity and miscibility of ILs

Viscosity is an important parameter in the study of the nature of ILs. The highly viscous nature of ILs directly affects the mass transfer of the reaction and vice versa [48]. Figure 3 shows the viscosity of ILs from room temperature to 65°C. ILs were completely dried under high vacuum for up to 3 hours below this temperature. The viscosity of ILs varies according to temperature. Initially, at 25 °C, the viscosity of all ILs was observed at 605,910, 470, and 420 cP for [OMs]-, [PF6]-, [N(CN)2]-, and [NTf2]- anions respectively. Of all ILs, the viscosities of [PF6]- and [OMs]- anions with the vinyl-imidazole cation were higher than for other anions with the same cation. The reasons for this are the strong electrostatic force between cation and anion. Increasing the temperature further resulted in a decrease in the viscosity of the ILs. At higher temperatures all ILs melt and their viscosity decreased due to the decreased interaction between cation and anion.

From the above results it was concluded that, the synthesized ILs with [PF6]-, and [OMs]- anions have higher viscosity than ILs with other anions due to intra and intermolecular hydrogen bonding and van der Waals forces. The [OMs]- anion is completely miscible with water (polar) and completely insoluble in benzene (non-polar) due to the weak interaction between solvents and [OMs]- anion. In the case of [NTf2]- and [PF6]- anions they are miscible with benzene and immiscible with water.

3.1.2 Determination of acidity for di-cationic ILs

In dimethyl carbonate (DMC) synthesis acidic sites activate the methanol and basic sites activate the carbon dioxide (CO2), thus catalytic activity mainly depends on the Lewis acidic-basic nature of the catalyst [49]. The Lewis acidity-basicity of ILs is measured by Fourier transform- infrared (FT-IR) and UV-visible spectroscopy [50] using pyridine as an intermediate molecule. Figure 4 shows the shift of the position of the pyridine mixed EG[Vim]2[NTf2]2 ILs bands from 1434 to 1439 cm−1 and 1573 to 1580 cm−1, clearly demonstrating that the IL is a Lewis acid which forms pyridinium ions [PyH]+ [51]. Hence, highly fluorinated anion salts have low basicity, and the imidazolium cation has lower basicity than the phosphonium cation with the same anions [42].

Figure 4 FT-IR spectra of (A) Pure pyridine, (B) EG[Vim]2[NTf2]2 + pyridine (2:5 ratio), (C) EG[Vim]2[NTf2]2
Figure 4

FT-IR spectra of (A) Pure pyridine, (B) EG[Vim]2[NTf2]2 + pyridine (2:5 ratio), (C) EG[Vim]2[NTf2]2

3.2 Catalytic performance of ILs

The catalytic performance of ILs was analyzed for DMC synthesis from CO2 and MeOH. There are several types of drying agents (moisture sensitive agents) reported for organic carbonate synthesis such as 4-dimethyl aminopyridine (DMAP), 1,4-diazabicyclo [2.2.2] octane (DABCO), 1,8-diazabicyclo [2.2.2] undec-7-ene (DBU), 1,5,7-triaza- bicyclo [4.4.0]dec-5-ene (TBD), and hexamethylene tetramine (HMTA). Their efficacy is probably due to their Lewis basicity and ability to attract moisture [52]. In this study DMC was formed from CO2 and MeOH using an IL/DMAP catalyst. No product yield was detected without the catalyst (Table 1, entry 1). When DMAP was used without ILs, no reaction occurred (Table 1, entry 2) due to the lack of an active site to adsorb CO2. Employing EG[Vim]2[PF6]2 IL as a catalyst without DMAP yielded DMC (Table 1, entry 3). A plausible reason for this is that the [PF6]- anion binds more strongly with the cation. Using different ILs such as EG[Vim]2[N(CN2)]2 and EG[Vim]2[OMs]2 resulted in increased DMC yield. The CO2 solubility depends on various factors such as mole fraction, viscosity, dipole moment, polarizability, quadrupole moments, Lewis acidity-basicity, and nonspecific dispersion forces between the CO2 and IL [53,54]. EG[Vim]2[NTf2]2 IL resulted in the highest DMC yield due to the anion’s ability to capture CO2. The main byproduct is water so a low amount of water would indicate that the DMC formation should be higher. Therefore, formation of water during the reaction had an effect on the DMC yield.

Table 1

Catalytic performance of ILs on dimethyl carbonate production.

EntryCatalystYield of DMC (mmol)b Selectivity of DMC (%)
1Without ionic liquid--
2Only DMAP--
3EG[Vim]2[PF6]232.516.7
4EG[Vim]2[N(CN)2]245.525.5
5EG[Vim]2[NTf2]253.737.8
6EG[Vim]2[PF6]2/DMAP32.620.3
7EG[Vim]2[N(CN)2]2/DMAP35.935.1
8EG[Vim]2[NTf2]2/DMAP41.991.8

  1. Reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa at 130 °C, 6 h,

    bon the basis of GC analysis.

To overcome this problem, we used a moisture sensitive agent, 4-dimethyl amino pyridine (DMAP) which acts as a water trapping agent and a Lewis base in the synthesis of ILs. The binary EG[Vim]2[NTf2]2/DMAP catalytic system gives a higher yield of DMC than remaining ILs within a 6 hour reaction time because the combination of DMAP and IL provides the moderately Lewis acidic and basic sites required for DMC synthesis. They reversibly capture more CO2 and shift the equilibrium towards products [55]. EG[Vim]2[NTf2]2/DMAP displays the highest activity with the greater DMC yield (Table 1, entry 8) than the other prepared IL/DMAP catalytic systems (Table 1, entry 6-7). This is mostly likely due to EG[Vim]2[NTf2]2- ILs having a higher solubility of CO2. Moreover, organic base (DMAP) provides synergistic combination of cation and anion therefore it has an enormous potential to enhance the reaction in the forward direction. This reaction of CO2 and MeOH with IL/DMAP catalytic system can easily capture and convert CO2 into a valuable product. Increasing the concentration of CO2 in the reaction mixture with MeOH resulted in CO2 changing from gas to liquid phase and methanol changing from liquid to gas at equilibrium. The liquid phase of CO2 is much more reactive than the gas phase and the conversion to product is much higher [48]. Therefore, EG[Vim]2[NTf2]2/DMAP catalytic system was deliberated for further studies.

3.2.1 Effect of reaction temperature, pressure, and time on DMC production

The effect of temperature was studied on the basis of yield and selectivity of DMC. The reaction was carried out in a stainless-steel autoclave containing 20 g of MeOH (625 mmol), 1.28 mmol of IL, 4.1 mmol of DMAP under 6.5 MPa CO2 pressure for 6 hours. For comparison, the DMC synthesis was initially carried out at room temperature resulting in negligible DMC yield. Increasing the temperature to 70°C resulted in a gradual increase in yield to 13 mmol of DMC. Further temperature increases increased the DMC yield steadily. The highest yield was obtained at 130 °C when the IL, MeOH, and CO2 were in single liquid phase. A further increase in temperature resulted in a gradual decrease in yield. This might be due to the formation of the byproduct dimethoxymethane (DMM) and subsequently degradation of DMC [56] as shown in Figure 6.

Figure 5 Elemental analysis of synthesized RTILs.
Figure 5

Elemental analysis of synthesized RTILs.

Figure 6 Effect of temperature on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.
Figure 6

Effect of temperature on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.

Table 2

Literature survey of ILs on dimethyl carbonate production.

EntryCatalytic systemTime (h)Temp (°C)Pressure (MPa)Yield of DMC (mmol)Refs.
1EG[Vim]2[NTf2]2/DMAP61306.541.9Present work
2[EmimOH][NTf2]+DBU41406.521.1[58]
3[K+{PEG}Br]-/K2CO361507.226.0[59]
4K2CO3+EmimBr/CH3I5807.318.9[60]
5Choline hydroxide91508.044.5[61]

Optimal CO2 pressure results in high conversion and selectivity. Without CO2 pressure the DMC yield is low because of stable nature of CO2 caused by the great bond strength between carbon and oxygen. The high pressure must be necessary for CO2 activation. An increase in reaction pressure increased the yield and selectivity. DMC yield and selectivity were greatest at 6.5 MPa. From these results it is apparent that the CO2 pressure is directly proportional to the MeOH conversion, as shown in Figure 7.

Figure 7 Effect of pressure on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.
Figure 7

Effect of pressure on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.

According to our results 6 hours was the optimal reaction time at which the highest DMC yield of 41.9 mmol was obtained. Longer reaction times resulted in a decrease in DMC yield probably due to hydrolysis [57] as shown in Figure 8.

Figure 8 Effect of time on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.
Figure 8

Effect of time on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.

3.2.2 Effect of different moisture sensitive agents and IL loading on DMC production

The DMC yield was increased from 22.2 to 41.9 mmol at constant loading of ILs (1.28 mmol) when different moisture sensitive agents were used. Initially when 1,8-diazabicyclo[2.2.2]undec-7-ene (DBU) was used the DMC yield was negligible. In the case of 2-cyanopyridine the DMC yield was higher as this agent provides more basic sites which can easily trap the H2O molecules. The disadvantage of using 2-cyanopyridine is that it forms 2-picoliamide upon reaction with H2O and is not stable at elevated temperatures resulting in low DMC yield. On the other hand, 4-dimethyl aminopyridine (DMAP) possesses an amino group and is mildly basic allowing it to trap water molecules resulting in a high DMC yield.

In Figure 9 we studied the ILs loading. Firstly, the reaction was performed without IL resulting in no DMC formation. When 0.5 g of IL was used, the selectivity and yield increased gradually. Based on this result we increased the amount of IL to 1 g resulting in a higher yield and selectivity. The higher concentration of IL in the reaction mixture provides more active sites and higher surface area on which CO2 can be captured. Upon increased amount of ILs to 1.5 g the DMC yield and selectivity were decreased drastically because of the higher loading probably lower down the acidic or electrophilic sites of the ILs, therefore, decrease the DMC yield.

Figure 9 Effect of EG[Vim]2[NTf2]2 loading on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL:1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.
Figure 9

Effect of EG[Vim]2[NTf2]2 loading on yield and selectivity of DMC production under reaction conditions: MeOH: 625 mmol, IL:1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.

3.3 Proposed reaction mechanism

The synthesized ILs are active towards organic carbonate (DMC) synthesis. The reaction mechanism we proposed based on the reaction progression is shown in Scheme 4. In the first step, the DMAP abstracts the acidic hydrogen of vinyl-imidazole cation and then nucleophilic attack of the vinyl-imidazole ring anion on the carbonyl carbon of CO2 takes place, resulting to form anionic carbamate intermediate. The electron rich nucleophilic oxygen species of the carbamate group attacks the hydrogen atom of the MeOH, leading to the formation of methoxide anion. The methoxide anion attacks the electrophilic carbon atom of the CO2 followed by removal of water. Subsequently, another methoxide anion attacks the carbonyl group of the CO2 and finally DMC is formed and at the same time the ILs regeneration take place.

Scheme 4 Proposed mechanism for DMC synthesis catalyzed by vinyl-imidazolium RTILs.
Scheme 4

Proposed mechanism for DMC synthesis catalyzed by vinyl-imidazolium RTILs.

3.4 Recyclability of catalyst

Reusability of a catalyst is important from an industrial point of view. The synthesized IL/DMAP catalytic system can be reused for the production of DMC as shown in Figure 10. For the second recycle reaction the IL was removed by vacuum distillation from the reaction mixture and further reused beneath the identical reaction conditions. The recycled IL can be reused under the same reaction conditions (130°C, 6.5 MPa CO2, and 6 hours) for five cycles with maintaining the same yield and selectivity of DMC. Furthermore, the ILs stability is confirmed by the TGA (Figure 11) shows good stability of the ILs with high yield of DMC and the FT-IR spectroscopy (Figure 12) which shows that the structure of ILs changes after fifth time reused. From these results we determine that the ILs catalyst is stable and effective for DMC synthesis.

Figure 10 Reusability of EG[Vim]2[NTf2]2/DMAP RTILs for synthesis of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.
Figure 10

Reusability of EG[Vim]2[NTf2]2/DMAP RTILs for synthesis of DMC production under reaction conditions: MeOH: 625 mmol, IL: 1.28 mmol, DMAP: 4.1 mmol, CO2 pressure, 6.5 MPa, 130°C, 6 h.

Figure 11 Comparison of the TGA results of the fresh and five times reused EG[Vim]2[NTf2]2/DMAP ILs.
Figure 11

Comparison of the TGA results of the fresh and five times reused EG[Vim]2[NTf2]2/DMAP ILs.

Figure 12 Comparison of the FT-IR spectra of fresh and the five times reused EG[Vim]2[NTf2]2/DMAP ILs.
Figure 12

Comparison of the FT-IR spectra of fresh and the five times reused EG[Vim]2[NTf2]2/DMAP ILs.

4 Conclusion

In summary, a chain of ILs with different anions and the same cation were synthesized for the production of DMC from CO2 and MeOH. The performance of the ILs was much better than that reported for dicationic ILs. This may be because the new system is a Lewis acid, an important parameter in DMC synthesis. Moreover, the DMAP absorbed more water from the reaction mixture improving the DMC yield. The ILs were synthesized using ethylene glycol. The EG[Vim]2[NTf2]2 IL/DMAP (1:3 ratio) catalytic system was the most efficient with 91.8% selectivity and 41.9 mmol DMC yield. The steric bulk and electronic properties of the Lewis base can play a dual role in determining the selectivity and activity of the catalyst [39]. The given catalyst could be easily recycled up to five runs. These environmentally friendly ILs can be used as substitutes for metal oxides and also minimize waste gases (CO2) from the environment, key factors from the green chemistry point of view.

Acknowledgment

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20194010201750).

  1. Conflict of interest: Authors declare no conflict of interest.

References

[1] He M., Sun Y., Han B., Green carbon science: Scientific basis for integrating carbon resource processing, utilization, and recycling, Angew. Chemie - Int. Ed., 2013, 52, 9620-9633, doi:10.1002/anie.201209384.10.1002/anie.201209384Search in Google Scholar PubMed

[2] Dai W.L., Luo S.L., Yin S.F., Au C.T., The direct transformation of carbon dioxide to organic carbonates over heterogeneous catalysts, Appl. Catal. A Gen., 2009, 366, 2-12, doi:10.1016/j.apcata.2009.06.045.10.1016/j.apcata.2009.06.045Search in Google Scholar

[3] Sakakura T., Choi J.C., Yasuda H., Transformation of carbon dioxide, Chem. Rev., 2007, 107, 2365-2387, doi:10.1021/cr068357u.10.1021/cr068357uSearch in Google Scholar PubMed

[4] Shi F., Deng Y., Sima T., Peng J., Gu Y., Qiao B., Synthesis of symmetric urea derivatives with carbon dioxide in ionic liquids, Angew. Chem., 2003, 115, 3379-3382, doi:10.1002/ange.200351098.10.1002/ange.200351098Search in Google Scholar

[5] Fang S., Fujimoto K., Direct synthesis of dimethyl carbonate from carbon dioxide and methanol catalyzed by base, Appl. Catal. A Gen., 1996, 142, 8-10, doi:10.1016/0926-860X(96)00081-6.10.1016/0926-860X(96)00081-6Search in Google Scholar

[6] Ballivet-Tkatchenko D., Chambrey S., Keiski R., Ligabue R., Plasseraud L., Richard P., Turunen H., Direct synthesis of dimethyl carbonate with supercritical carbon dioxide: characterization of a key organotin oxide intermediate, Catal. Today, 2006, 115, 80-87, doi:10.1016/j.cattod.2006.02.025.10.1016/j.cattod.2006.02.025Search in Google Scholar

[7] Merza G., Laszlo B., Oszko A., Potari G., Varga E., Erdohelyi A., The synthesis of dimethyl carbonate by the oxicarbonylation of methanol over Cu supported on carbon norit, Catal. Letters, 2015, 145, 881-892, doi:10.1007/s10562-014-1460-9.10.1007/s10562-014-1460-9Search in Google Scholar

[8] Honda M., Tamura M., Nakagawa Y., Tomishige K., Catalytic CO2 conversion to organic carbonates with alcohols in combination with dehydration system, Catal. Sci. Technol, 2014, 4, 2830-2845, doi:10.1039/c4cy00557k.10.1039/c4cy00557kSearch in Google Scholar

[9] Bandal H.A., Jadhav A.R., Kim H., Facile synthesis of bicontinuous Ni3Fe alloy for efficient electrocatalytic oxygen evolution reaction, J. Alloys Compound, 2017, 726, 875-884, doi:10.1016/j.jallcom.2017.07.290.10.1016/j.jallcom.2017.07.290Search in Google Scholar

[10] Darensbourg D.J., Fang C.C., Rodgers J.L., Catalytic coupling of carbon dioxide and 2,3-epoxy-1,2,3,4-tetrahydronaphthalene in the presence of a (Salen) Cr(III)Cl derivative, organometallics, 2004, 23, 924-927, doi:10.1021/om034278m.10.1021/om034278mSearch in Google Scholar

[11] Sun J., Wang L., Zhang S., Li Z., Zhang X., Dai W., Mori R., ZnCl2/phosphonium halide: an efficient Lewis acid/base catalyst for the synthesis of cyclic carbonate, J. Mol. Catal. A Chem, 2006, 256, 295-300, doi:10.1016/j.molcata.2006.05.004.10.1016/j.molcata.2006.05.004Search in Google Scholar

[12] Jiang J.L., Hua R., Efficient DMF-catalyzed coupling of epoxides with CO2 under solvent-free conditions to afford cyclic carbonates, Synth. Commun, 2006, 36, 3141-3148, doi:10.1080/00397910600908744.10.1080/00397910600908744Search in Google Scholar

[13] Bhanage B.M., Fujita S., Ikushima Y., Arai M., Synthesis of dimethyl carbonate and glycols from carbon dioxide, epoxides, and methanol using heterogeneous basic metal oxide catalysts with high activity and selectivity, Appl. Catal. A Gen, 2001, 219, 259-266, doi:10.1016/S0926-860X(01)00698-6.10.1016/S0926-860X(01)00698-6Search in Google Scholar

[14] Jadhav A.H., Chinnappan A., Hiremath V., Seo J.G., Synthesis and characterization of AlCl3 impregnated molybdenum oxide as heterogeneous nano-catalyst for the friedel-crafts acylation reaction in ambient condition, J. Nanosci. Nanotechnol, 2015, 15, 8243-8250, doi:10.1166/jnn.2015.11253.10.1166/jnn.2015.11253Search in Google Scholar PubMed

[15] Thorat G.M., Jadhav A.H., Jadhav H.S., Lee K., Seo J.G., Template-free synthesis and characterization of nickel oxide nanocrystal with high-energy facets in deep eutectic solvent, J. Nanosci. Nanotechnol, 2016, 16, 11009-11013, doi:10.1166/jnn.2016.13280.10.1166/jnn.2016.13280Search in Google Scholar

[16] Barbarini A., Maggi R., Mazzacani A., Mori G., Sartori G., Sartorio R., Cycloaddition of CO2 to epoxides over both homogeneous and silica-supported guanidine catalysts, Tetrahedron Lett, 2003, 44, 2931-2934, doi:10.1016/S0040-4039(03)00424-6.10.1016/S0040-4039(03)00424-6Search in Google Scholar

[17] Chaugule A.A., Tamboli A.H., Kim H., Efficient fixation and conversion of CO2 into dimethyl carbonate catalyzed by an imidazolium containing tri-cationic ionic liquid/super base system, RSC Adv, 2016, 6, 42279-42287, doi:10.1039/C6RA04084E.10.1039/C6RA04084ESearch in Google Scholar

[18] North M., Pasquale R., Young C., Synthesis of cyclic carbonates from epoxides and CO2 Green Chem, 2010, 12, 1514, doi:10.1039/c0gc00065e.10.1039/c0gc00065eSearch in Google Scholar

[19] North M., Pasquale R., Mechanism of cyclic carbonate synthesis from epoxides and CO2 Angew. Chemie, 2009, 121, 2990-2992, doi:10.1002/ange.200805451.10.1002/ange.200805451Search in Google Scholar

[20] Saptal V.B., Bhanage B.M., Bifunctional ionic liquids for the multitask fixation of carbon dioxide into valuable chemicals, Chem Cat Chem, 2016, 8, 244-250, doi:10.1002/cctc.201501044.10.1002/cctc.201501044Search in Google Scholar

[21] Wagh K. V., Bhanage B.M., Synthesis of 2-phenylnaphthalenes from styrene oxides using a recyclable Brønsted acidic [HNMP]+HSO4- ionic liquid, Green Chem, 2015, 17, 4446-4451, doi:10.1039/c5gc01170a.10.1039/c5gc01170aSearch in Google Scholar

[22] Wang Y., Ye H., Zuo G., Luo J., Synthesis of a novel poly (ethylene glycol) grafted N,N-dimethylaminopyridine functionalized dicationic ionic liquid and its application in one-pot synthesis of 3,4-dihydropyrano[3,2-c]chromene derivatives in water, J. Mol. Liq, 2015, 212, 418-422, doi:10.1016/j.molliq.2015.09.030.10.1016/j.molliq.2015.09.030Search in Google Scholar

[23] Godajdar B.M., Mombeni S., Polyethylene glycol functionalized magnetic dicationic ionic liquids as a novel catalyst and their application in ring opening of epoxides in water, J. Chinese Chem. Soc, 2015, 62, 404-411, doi:10.1002/jccs.201400383.10.1002/jccs.201400383Search in Google Scholar

[24] Watile R.A., Bagal D.B., Patil Y.P., Bhanage B.M., Regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines using Br- Ph3 +PPEG 600P+Ph3Br- as an efficient, homogenous recyclable catalyst at ambient conditions, Tetrahedron Lett, 2011, 52, 6383-6387, doi:10.1016/j. tetlet.2011.09.056.10.1016/j.tetlet.2011.09.056Search in Google Scholar

[25] Godajdar B.M., Ansari B., Preparation of novel magnetic dicationic ionic liquid polymeric phase transfer catalyst and their application in nucleophilic substitution reactions of benzyl halides in water, J. Mol. Liq, 2015, 202, 34-39, doi:10.1016/j.molliq.2014.12.009.10.1016/j.molliq.2014.12.009Search in Google Scholar

[26] Patil Y.P., Tambade P.J., Jagtap S.R., Bhanage B.M., Synthesis of 2-oxazolidinones/2-imidazolidinones from CO2 different epoxides and amino alcohols/alkylene diamines using Br-Ph3+P-PEG600- P+Ph3Br-as homogenous recyclable catalyst, J. Mol. Catal. A Chem, 2008, 289, 14-21, doi:10.1016/j. molcata.2008.03.019.10.1016/j.molcata.2008.03.019Search in Google Scholar

[27] Cecchini M.M., Charnay C., De Angelis F., Lamaty F., Martinez J., Colacino E., Poly(ethylene glycol)-based ionic liquids: properties and uses as alternative solvents in organic synthesis and catalysis, Chem Sus Chem, 2014, 7, 45-65, doi:10.1002/ cssc.201300421.10.1002/cssc.201300421Search in Google Scholar PubMed

[28] Tang S., Baker G.A., Zhao H., Ether and alcohol-functionalized task-specific ionic liquids: attractive properties and applications, Chem. Soc. Rev, 2012, 41, 4030-4066, doi:10.1039/c2cs15362a.10.1039/c2cs15362aSearch in Google Scholar PubMed PubMed Central

[29] Vafaeezadeh M., Hashemi M.M., Polyethylene glycol (PEG) as a green solvent for carbon-carbon bond formation reactions, J. Mol. Liq, 2015, 20, 73-79, doi:10.1016/j.molliq.2015.03.003.10.1016/j.molliq.2015.03.003Search in Google Scholar

[30] Colacino E., Martinez J., Lamaty F., Patrikeeva L.S., Khemchyan L.L., Ananikov V.P., Beletskaya I.P., PEG as an alternative reaction medium in metal-mediated transformations, Coord. Chem. Rev, 2012, 256, 2893-2920, doi:10.1016/j.ccr.2012.05.027.10.1016/j.ccr.2012.05.027Search in Google Scholar

[31] Bandal H., Reddy K.K., Chaugule A., Kim H., Iron-based heterogeneous catalysts for oxygen evolution reaction; change in perspective from activity promoter to active catalyst, J. Power Sources, 2018, 395, 106-127, doi:10.1016/j.jpowsour.2018.05.047.10.1016/j.jpowsour.2018.05.047Search in Google Scholar

[32] Jadhav A.H., Lee K., Koo S., Seo J.G., Esterification of carboxylic acids with alkyl halides using imidazolium based dicationic ionic liquids containing bis-trifluoromethane sulfonimide anions at room temperature, RSC Adv, 2015, 5, 26197-26208, doi:10.1039/c5ra00802f.10.1039/c5ra00802fSearch in Google Scholar

[33] Izgorodina E.I., Hodgson J.L., Weis D.C., Pas S.J., MacFarlane D.R., Physical Absorption of CO2 in protic and aprotic ionic liquids:an interaction perspective, J. Phys. Chem. B, 2015, 119, 11748-11759, doi:10.1021/acs.jpcb.5b05115.10.1021/acs.jpcb.5b05115Search in Google Scholar PubMed

[34] Wang C., Mahurin S.M., Luo H., Baker G.A., Li H., Dai S., Reversible and robust CO2 capture by equimolar task-specific ionic liquid-superbase mixtures, Green Chem, 2010, 12, 870-874, doi:10.1039/b927514b.10.1039/b927514bSearch in Google Scholar

[35] Wang C., Luo H., Li H., Zhu X., Yu B., Dai S., Tuning the physicochemical properties of diverse phenolic ionic liquids for equimolar CO2 capture by the substituent on the anion, Chem. - A Eur. J, 2012, 18, 2153-2160, doi:10.1002/chem.201103092.10.1002/chem.201103092Search in Google Scholar PubMed

[36] Bustamante F., Orrego A.F., Villegas S., Villa A.L., Modeling of chemical equilibrium and gas phase behavior for the direct synthesis of dimethyl carbonate from CO2 and methanol, Ind. Eng. Chem. Res, 2012, 51, 8945-8956, doi:10.1021/ie300017r.10.1021/ie300017rSearch in Google Scholar

[37] Darensbourg D.J., Mackiewicz R.M., Role of the cocatalyst in the copolymerization of CO2 and cyclohexene oxide utilizing chromium salen complexes, J. Am. Chem. Soc, 2005, 127, 14026-14038, doi:10.1021/ja053544f.10.1021/ja053544fSearch in Google Scholar PubMed

[38] Jing H., Edulji S.K., Gibbs J.M., Stern C.L., Zhou H., Nguyen S.T., (Salen) tin complexes: syntheses, characterization, crystal structures, and catalytic activity in the formation of propylene carbonate from CO2 and propylene oxide, Inorg. Chem, 2004, 43, 4315-4327, doi:10.1021/ic034855z.10.1021/ic034855zSearch in Google Scholar PubMed

[39] Paddock R.L., Nguyen S.T., Chiral (salen) Co(III) catalyst for the synthesis of cyclic carbonates, Chem. Commun, 2004, 1, 1622-1623, doi:10.1039/B401543F.10.1039/B401543FSearch in Google Scholar

[40] Jadhav A.H., Thorat G.M., Lee K., Lim A.C., Kang H., Seo J.G., Effect of anion type of imidazolium based polymer supported ionic liquids on the solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today, 2016, 26, 56-67, doi:10.1016/j. cattod.2015.09.048.10.1016/j.cattod.2015.09.048Search in Google Scholar

[41] Jadhav A.H., Lim A.C., Thorat G.M., Jadhav H.S., Seo J.G., Green solvent ionic liquids: structural directing pioneers for microwave-assisted synthesis of controlled MgO nanostructures, RSC Adv, 2016, 6, 31675-31686, doi:10.1039/c6ra02980a.10.1039/c6ra02980aSearch in Google Scholar

[42] Hallett J.P., Welton T., Room-temperature ionic liquids: solvents for synthesis and catalysis. 2, Chem. Rev, 2011, 111, 3508-3576, doi:10.1021/cr1003248.10.1021/cr1003248Search in Google Scholar PubMed

[43] Baranyai K.J., Deacon G.B., MacFarlane D.R., Pringle J.M., Scott J.L., Thermal degradation of ionic liquids at elevated temperatures, Aust. J. Chem, 2004, 57, 145-147, doi:10.1071/CH03221.10.1071/CH03221Search in Google Scholar

[44] Chambreau S.D., Schenk A.C., Sheppard A.J., Yandek G.R., Vaghjiani G.L., Maciejewski J., Koh C.J., Golan A., Leone S.R., Thermal decomposition mechanisms of alkylimidazolium ionic liquids with cyano-functionalized anions, J. Phys. Chem. A, 2014, 118, 11119-11132, doi:10.1021/jp5095855.10.1021/jp5095855Search in Google Scholar PubMed

[45] Plechkova N. V., Seddon K.R., Applications of ionic liquids in the chemical industry, Chem. Soc. Rev, 2008, 37, 123-150, doi:10.1039/b006677j.10.1039/b006677jSearch in Google Scholar PubMed

[46] Zeng Z., Phillips B.S., Xiao J., Shreeve J.M., Polyfluoroalkyl , polyethylene glycol , 1,4-bismethylenebenzene , or dicationic ionic liquids : synthesis and properties as high temperature lubricants, Chem. Mater, 2008, 20, 2719-2726, doi: 10.1021/cm703693r.10.1021/cm703693rSearch in Google Scholar

[47] Chaugule A.A., Bandhal H.A., Tamboli A.H., Chung W.J., Kim H., Highly efficient synthesis of dimethyl carbonate from methanol and carbon dioxide using IL/DBU/SmOCl as a novel ternary catalytic system, Catal. Commun, 2016, 75, 87-91, doi:10.1016/j.catcom.2015.12.009.10.1016/j.catcom.2015.12.009Search in Google Scholar

[48] Muldoon M.J., Aki S.N.V.K., Anderson J.L., Dixon J.K., Brennecke J.F., Improving carbon dioxide solubility in ionic liquids, J. Phys. Chem. B, 2007, 111, 9001-9009, doi:10.1021/jp071897q.10.1021/jp071897qSearch in Google Scholar PubMed

[49] Tamboli A.H., Chaugule A.A., Kim H., Catalytic developments in the direct dimethyl carbonate synthesis from carbon dioxide and methanol, Chem. Eng. J, 2017, 323, 530-544, doi:10.1016/j. cej.2017.04.112.10.1016/j.cej.2017.04.112Search in Google Scholar

[50] Wang T., Zheng D., Zhang J., Fan B., Ma Y., Ren T., Wang L., Zhang J., Protic pyrazolium ionic liquids: an efficient catalyst for conversion of CO2 in the absence of metal and solvent, ACS Sustain. Chem. Eng, 2018, 6, 2574-2582, doi:10.1021/ acssuschemeng.7b04051.10.1021/acssuschemeng.7b04051Search in Google Scholar

[51] Sharma N.K., Tickell M.D., Anderson J.L., Kaar J., Pino V., Wicker B.F., Armstrong D.W., Davis J.H., Russell A.J., Do ion tethered functional groups affect IL solvent properties? The case of sulfoxides and sulfones, Chem. Commun, 2006, 6, 646-648, doi:10.1039/b514832d.10.1039/b514832dSearch in Google Scholar PubMed

[52] Yang Z.Z., He L.N., Miao C.X., Chanfreau S., Lewis basic ionic liquids-catalyzed conversion of carbon dioxide to cyclic carbonates, Adv. Synth. Catal, 2010, 352, 2233-2240, doi:10.1002/adsc.201000239.10.1002/adsc.201000239Search in Google Scholar

[53] Pringle J.M., Baranyai K., Forsyth C.M., Deacon G.B., Scott J.L., MacFarlane D.R., Golding J., The effect of anion fluorination in ionic liquids - physical properties of a range of bis(methanesulfonyl)amide salts, New J. Chem, 2003, 27, 1504-1510, doi:10.1039/B304072K.10.1039/B304072KSearch in Google Scholar

[54] Sun J., Fujita S.I., Zhao F., Arai M., Synthesis of styrene carbonate from styrene oxide and carbon dioxide in the presence of zinc bromide and ionic liquid under mild conditions, Green Chem, 2004, 6, 613-616, doi:10.1039/b413229g.10.1039/b413229gSearch in Google Scholar

[55] Shen Y.M., Duan W.L., Shi M., Chemical fixation of carbon dioxide co-catalyzed by a combination of schiff bases or phenols and organic bases, European J. Org. Chem, 2004, 3080-3089, doi:10.1002/ejoc.200400083.10.1002/ejoc.200400083Search in Google Scholar

[56] Sun J., Lu B., Wang X., Li X., Zhao J., Cai Q., A functionalized basic ionic liquid for synthesis of dimethyl carbonate from methanol and CO2 Fuel Process. Technol, 2013, 115, 233-237, doi:10.1016/j.fuproc.2013.06.009.10.1016/j.fuproc.2013.06.009Search in Google Scholar

[57] Eta V., Maki-Arvela P., Leino A.R., Kordas K., Salmi T., Murzin D.Y., Mikkola J.P., Synthesis of dimethyl carbonate from methanol and carbon dioxide: Circumventing thermodynamic limitations, Ind. Eng. Chem. Res, 2010, 4, 9609-9617, doi:10.1021/ie1012147.10.1021/ie1012147Search in Google Scholar

[58] Chaugule A.A., Bandhal H.A., Tamboli A.H., Chung W.J., Kim H., Highly efficient synthesis of dimethyl carbonate from methanol and carbon dioxide using IL/DBU/SmOCl as a novel ternary catalytic system, Catal. Commun, 2016, 75, 87-91, doi:10.1016/j.catcom.2015.12.009.10.1016/j.catcom.2015.12.009Search in Google Scholar

[59] Chu G.H., Park J.B., Cheong M., Synthesis of dimethyl carbonate from carbon dioxide over polymer-supported iodide catalysts, Inorganica Chim. Acta, 2000, 307, 131-133, doi:10.1016/S0020-1693(00)00178-X.10.1016/S0020-1693(00)00178-XSearch in Google Scholar

[60] Kabra S.K., Turpeinen E., Keiski R.L., Yadav G.D., Direct synthesis of dimethyl carbonate from methanol and carbon dioxide: a thermodynamic and experimental study, J. Supercrit. Fluids, 2016, 117, 98-107, doi:10.1016/j.supflu.2016.05.039.10.1016/j.supflu.2016.05.039Search in Google Scholar

[61] Eta V., Maki-Arvela P., Salminen E., Salmi T., Murzin D.Y., Mikkola J.P., The effect of alkoxide ionic liquids on the synthesis of dimethyl carbonate from CO2 and methanol over ZrO2-MgO, Catal. Letters, 2011, 141, 1254-1261, doi:10.1007/s10562-011-0666-310.1007/s10562-011-0666-3Search in Google Scholar

Received: 2018-12-12
Accepted: 2019-09-10
Published Online: 2019-12-31

© 2019 Atul A. Pawar et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 Public License.

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  29. Chemical pretreatments of Trapa bispinosa's peel (TBP) biosorbent to enhance adsorption capacity for Pb(ll)
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  32. Photodynamic Therapy Enhanced the Antitumor Effects of Berberine on HeLa Cells
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  37. Effects of Blue and Red Light On Growth And Nitrate Metabolism In Pakchoi
  38. miRNA-199a-5p functions as a tumor suppressor in prolactinomas
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  41. Preparation and spectroscopic studies of Fe(II), Ru(II), Pd(II) and Zn(II) complexes of Schiff base containing terephthalaldehyde and their transfer hydrogenation and Suzuki-Miyaura coupling reaction
  42. Complex formation in a liquid-liquid extraction-chromogenic system for vanadium(IV)
  43. Synthesis, characterization (IR, 1H, 13C & 31P NMR), fungicidal, herbicidal and molecular docking evaluation of steroid phosphorus compounds
  44. Analysis and Biological Evaluation of Arisaema Amuremse Maxim Essential Oil
  45. A preliminary assessment of potential ecological risk and soil contamination by heavy metals around a cement factory, western Saudi Arabia
  46. Anti- inflammatory effect of Prunus tomentosa Thunb total flavones in LPS-induced RAW264.7 cells
  47. Collaborative Influence of Elevated CO2 Concentration and High Temperature on Potato Biomass Accumulation and Characteristics
  48. Methods of extraction, physicochemical properties of alginates and their applications in biomedical field – a review
  49. Characteristics of liposomes derived from egg yolk
  50. Preparation of ternary ZnO/Ag/cellulose and its enhanced photocatalytic degradation property on phenol and benzene in VOCs
  51. Influence of Human Serum Albumin Glycation on the Binding Affinities for Natural Flavonoids
  52. Synthesis and antioxidant activity of 2-methylthio-pyrido[3,2-e][1,2,4] triazolo[1,5-a]pyrimidines
  53. Comparative study on the antioxidant activities of ten common flower teas from China
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  56. Phytochemical analysis, Antioxidant and Antiprotoscolices potential of ethanol extracts of selected plants species against Echinococcus granulosus: In-vitro study
  57. Silver nanoparticles enhanced fluorescence for sensitive determination of fluoroquinolones in water solutions
  58. Simultaneous Quantification of the New Psychoactive Substances 3-FMC, 3-FPM, 4-CEC, and 4-BMC in Human Blood using GC-MS
  59. Biodiesel Production by Lipids From Indonesian strain of Microalgae Chlorella vulgaris
  60. Miscibility studies of polystyrene/polyvinyl chloride blend in presence of organoclay
  61. Antibacterial Activities of Transition Metal complexes of Mesocyclic Amidine 1,4-diazacycloheptane (DACH)
  62. Novel 1,8-Naphthyridine Derivatives: Design, Synthesis and in vitro screening of their cytotoxic activity against MCF7 cell line
  63. Investigation of Stress Corrosion Cracking Behaviour of Mg-Al-Zn Alloys in Different pH Environments by SSRT Method
  64. Various Combinations of Flame Retardants for Poly (vinyl chloride)
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  67. Optimizing Suitable Conditions for the Removal of Ammonium Nitrogen by a Microbe Isolated from Chicken Manure
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  69. The anti-corrosion behaviour of Satureja montana L. extract on iron in NaCl solution
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  71. A comparative study of the crystal structures of 2-(4-(2-(4-(3-chlorophenyl)pipera -zinyl)ethyl) benzyl)isoindoline-1,3-dione by synchrotron radiation X-ray powder diffraction and single-crystal X-ray diffraction
  72. Conceptual DFT as a Novel Chemoinformatics Tool for Studying the Chemical Reactivity Properties of the Amatoxin Family of Fungal Peptides
  73. Occurrence of Aflatoxin M1 in Milk-based Mithae samples from Pakistan
  74. Kinetics of Iron Removal From Ti-Extraction Blast Furnace Slag by Chlorination Calcination
  75. Increasing the activity of DNAzyme based on the telomeric sequence: 2’-OMe-RNA and LNA modifications
  76. Exploring the optoelectronic properties of a chromene-appended pyrimidone derivative for photovoltaic applications
  77. Effect of He Qi San on DNA Methylation in Type 2 Diabetes Mellitus Patients with Phlegm-blood Stasis Syndrome
  78. Cyclodextrin potentiometric sensors based on selective recognition sites for procainamide: Comparative and theoretical study
  79. Greener synthesis of dimethyl carbonate from carbon dioxide and methanol using a tunable ionic liquid catalyst
  80. Nonisothermal Cold Crystallization Kinetics of Poly(lactic acid)/Bacterial Poly(hydroxyoctanoate) (PHO)/Talc
  81. Enhanced adsorption of sulfonamide antibiotics in water by modified biochar derived from bagasse
  82. Study on the Mechanism of Shugan Xiaozhi Fang on Cells with Non-alcoholic Fatty Liver Disease
  83. Comparative Effects of Salt and Alkali Stress on Antioxidant System in Cotton (Gossypium Hirsutum L.) Leaves
  84. Optimization of chromatographic systems for analysis of selected psychotropic drugs and their metabolites in serum and saliva by HPLC in order to monitor therapeutic drugs
  85. Electrocatalytic Properties of Ni-Doped BaFe12O19 for Oxygen Evolution in Alkaline Solution
  86. Study on the removal of high contents of ammonium from piggery wastewater by clinoptilolite and the corresponding mechanisms
  87. Phytochemistry and toxicological assessment of Bryonia dioica roots used in north-African alternative medicine
  88. The essential oil composition of selected Hemerocallis cultivars and their biological activity
  89. Mechanical Properties of Carbon Fiber Reinforced Nanocrystalline Nickel Composite Electroforming Deposit
  90. Anti-c-myc efficacy block EGFL7 induced prolactinoma tumorigenesis
  91. Topical Issue on Applications of Mathematics in Chemistry
  92. Zagreb Connection Number Index of Nanotubes and Regular Hexagonal Lattice
  93. The Sanskruti index of trees and unicyclic graphs
  94. Valency-based molecular descriptors of Bakelite network BNmn
  95. Computing Topological Indices for Para-Line Graphs of Anthracene
  96. Zagreb Polynomials and redefined Zagreb indices of Dendrimers and Polyomino Chains
  97. Topological Descriptor of 2-Dimensional Silicon Carbons and Their Applications
  98. Topological invariants for the line graphs of some classes of graphs
  99. Words for maximal Subgroups of Fi24‘
  100. Generators of Maximal Subgroups of Harada-Norton and some Linear Groups
  101. Special Issue on POKOCHA 2018
  102. Influence of Production Parameters on the Content of Polyphenolic Compounds in Extruded Porridge Enriched with Chokeberry Fruit (Aronia melanocarpa (Michx.) Elliott)
  103. Effects of Supercritical Carbon Dioxide Extraction (SC-CO2) on the content of tiliroside in the extracts from Tilia L. flowers
  104. Impact of xanthan gum addition on phenolic acids composition and selected properties of new gluten-free maize-field bean pasta
  105. Impact of storage temperature and time on Moldavian dragonhead oil – spectroscopic and chemometric analysis
  106. The effect of selected substances on the stability of standard solutions in voltammetric analysis of ascorbic acid in fruit juices
  107. Determination of the content of Pb, Cd, Cu, Zn in dairy products from various regions of Poland
  108. Special Issue on IC3PE 2018 Conference
  109. The Photocatalytic Activity of Zns-TiO2 on a Carbon Fiber Prepared by Chemical Bath Deposition
  110. N-octyl chitosan derivatives as amphiphilic carrier agents for herbicide formulations
  111. Kinetics and Mechanistic Study of Hydrolysis of Adenosine Monophosphate Disodium Salt (AMPNa2) in Acidic and Alkaline Media
  112. Antimalarial Activity of Andrographis Paniculata Ness‘s N-hexane Extract and Its Major Compounds
  113. Special Issue on ABB2018 Conference
  114. Special Issue on ICCESEN 2017
  115. Theoretical Diagnostics of Second and Third-order Hyperpolarizabilities of Several Acid Derivatives
  116. Determination of Gamma Rays Efficiency Against Rhizoctonia solani in Potatoes
  117. Studies On Compatibilization Of Recycled Polyethylene/Thermoplastic Starch Blends By Using Different Compatibilizer
  118. Liquid−Liquid Extraction of Linalool from Methyl Eugenol with 1-Ethyl-3-methylimidazolium Hydrogen Sulfate [EMIM][HSO4] Ionic Liquid
  119. Synthesis of Graphene Oxide Through Ultrasonic Assisted Electrochemical Exfoliation
  120. Special Issue on ISCMP 2018
  121. Synthesis and antiproliferative evaluation of some 1,4-naphthoquinone derivatives against human cervical cancer cells
  122. The influence of the grafted aryl groups on the solvation properties of the graphyne and graphdiyne - a MD study
  123. Electrochemical modification of platinum and glassy carbon surfaces with pyridine layers and their use as complexing agents for copper (II) ions
  124. Effect of Electrospinning Process on Total Antioxidant Activity of Electrospun Nanofibers Containing Grape Seed Extract
  125. Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C
  126. Topical Issue on Agriculture
  127. The effect of Cladophora glomerata exudates on the amino acid composition of Cladophora fracta and Rhizoclonium sp.
  128. Influence of the Static Magnetic Field and Algal Extract on the Germination of Soybean Seeds
  129. The use of UV-induced fluorescence for the assessment of homogeneity of granular mixtures
  130. The use of microorganisms as bio-fertilizers in the cultivation of white lupine
  131. Lyophilized apples on flax oil and ethyl esters of flax oil - stability and antioxidant evaluation
  132. Production of phosphorus biofertilizer based on the renewable materials in large laboratory scale
  133. Human health risk assessment of potential toxic elements in paddy soil and rice (Oryza sativa) from Ugbawka fields, Enugu, Nigeria
  134. Recovery of phosphates(V) from wastewaters of different chemical composition
  135. Special Issue on the 4th Green Chemistry 2018
  136. Dead zone for hydrogenation of propylene reaction carried out on commercial catalyst pellets
  137. Improved thermally stable oligoetherols from 6-aminouracil, ethylene carbonate and boric acid
  138. The role of a chemical loop in removal of hazardous contaminants from coke oven wastewater during its treatment
  139. Combating paraben pollution in surface waters with a variety of photocatalyzed systems: Looking for the most efficient technology
  140. Special Issue on Chemistry Today for Tomorrow 2019
  141. Applying Discriminant and Cluster Analyses to Separate Allergenic from Non-allergenic Proteins
  142. Chemometric Expertise Of Clinical Monitoring Data Of Prolactinoma Patients
  143. Chemomertic Risk Assessment of Soil Pollution
  144. New composite sorbent for speciation analysis of soluble chromium in textiles
  145. Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green
  146. Photophysical and antibacterial activity of light-activated quaternary eosin Y
  147. Spectral properties and biological activity of La(III) and Nd(III) Monensinates
  148. Special Issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  149. Soil organic carbon mineralization in relation to microbial dynamics in subtropical red soils dominated by differently sized aggregates
  150. A potential reusable fluorescent aptasensor based on magnetic nanoparticles for ochratoxin A analysis
  151. Special Issue on 13th JCC 2018
  152. Fluorescence study of 5-nitroisatin Schiff base immobilized on SBA-15 for sensing Fe3+
  153. Thermal and Morphology Properties of Cellulose Nanofiber from TEMPO-oxidized Lower part of Empty Fruit Bunches (LEFB)
  154. Encapsulation of Vitamin C in Sesame Liposomes: Computational and Experimental Studies
  155. A comparative study of the utilization of synthetic foaming agent and aluminum powder as pore-forming agents in lightweight geopolymer synthesis
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  157. Review of large-pore mesostructured cellular foam (MCF) silica and its applications
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  160. Production of Biodiesel from Nyamplung (Calophyllum inophyllum L.) using Microwave with CaO Catalyst from Eggshell Waste: Optimization of Transesterification Process Parameters
  161. The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents
  162. Composite Material Consisting of HKUST-1 and Indonesian Activated Natural Zeolite and its Application in CO2 Capture
  163. Topical Issue on Environmental Chemistry
  164. Ionic liquids modified cobalt/ZSM-5 as a highly efficient catalyst for enhancing the selectivity towards KA oil in the aerobic oxidation of cyclohexane
  165. Application of Thermal Resistant Gemini Surfactants in Highly Thixotropic Water-in-oil Drilling Fluid System
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  167. The Chemical Softening Effect and Mechanism of Low Rank Coal Soaked in Alkaline Solution
  168. The Influence Of NO/O2 On The NOx Storage Properties Over A Pt-Ba-Ce/γ-Al2O3 Catalyst
  169. Special Issue on the International conference CosCI 2018
  170. Design of SiO2/TiO2 that Synergistically Increases The Hydrophobicity of Methyltrimethoxysilane Coated Glass
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  173. Special Issue on Applied Biochemistry and Biotechnology 2019
  174. Adsorption of copper ions on Magnolia officinalis residues after solid-phase fermentation with Phanerochaete chrysosporium
  175. Erratum
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https://doi.org/10.1515/chem-2019-0137
Keywords for this article
CO2; ILs; dehydrating agent; reaction mechanism
Creative Commons
BY 4.0

Articles in the same Issue

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  25. Aqueous Micro-hydration of Na+(H2O)n=1-7 Clusters: DFT Study
  26. A proposed image-based detection of methamidophos pesticide using peroxyoxalate chemiluminescence system
  27. Phytochemical screening and estrogenic activity of total glycosides of Cistanche deserticola
  28. Biological evaluation of a series of benzothiazole derivatives as mosquitocidal agents
  29. Chemical pretreatments of Trapa bispinosa's peel (TBP) biosorbent to enhance adsorption capacity for Pb(ll)
  30. Dynamic Changes in MMP1 and TIMP1 in the Antifibrotic Process of Dahuang Zhechong Pill in Rats with Liver Fibrosis
  31. The Optimization and Production of Ginkgolide B Lipid Microemulsion
  32. Photodynamic Therapy Enhanced the Antitumor Effects of Berberine on HeLa Cells
  33. Chiral and Achiral Enantiomeric Separation of (±)-Alprenolol
  34. Correlation of Water Fluoride with Body Fluids, Dental Fluorosis and FT4, FT3 –TSH Disruption among Children in an Endemic Fluorosis area in Pakistan
  35. A one-step incubation ELISA kit for rapid determination of dibutyl phthalate in water, beverage and liquor
  36. Free Radical Scavenging Activity of Essential Oil of Eugenia caryophylata from Amboina Island and Derivatives of Eugenol
  37. Effects of Blue and Red Light On Growth And Nitrate Metabolism In Pakchoi
  38. miRNA-199a-5p functions as a tumor suppressor in prolactinomas
  39. Solar photodegradation of carbamazepine from aqueous solutions using a compound parabolic concentrator equipped with a sun tracking system
  40. Influence of sub-inhibitory concentration of selected plant essential oils on the physical and biochemical properties of Pseudomonas orientalis
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  42. Complex formation in a liquid-liquid extraction-chromogenic system for vanadium(IV)
  43. Synthesis, characterization (IR, 1H, 13C & 31P NMR), fungicidal, herbicidal and molecular docking evaluation of steroid phosphorus compounds
  44. Analysis and Biological Evaluation of Arisaema Amuremse Maxim Essential Oil
  45. A preliminary assessment of potential ecological risk and soil contamination by heavy metals around a cement factory, western Saudi Arabia
  46. Anti- inflammatory effect of Prunus tomentosa Thunb total flavones in LPS-induced RAW264.7 cells
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  48. Methods of extraction, physicochemical properties of alginates and their applications in biomedical field – a review
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  53. Comparative study on the antioxidant activities of ten common flower teas from China
  54. Molecular Properties of Symmetrical Networks Using Topological Polynomials
  55. Synthesis of Co3O4 Nano Aggregates by Co-precipitation Method and its Catalytic and Fuel Additive Applications
  56. Phytochemical analysis, Antioxidant and Antiprotoscolices potential of ethanol extracts of selected plants species against Echinococcus granulosus: In-vitro study
  57. Silver nanoparticles enhanced fluorescence for sensitive determination of fluoroquinolones in water solutions
  58. Simultaneous Quantification of the New Psychoactive Substances 3-FMC, 3-FPM, 4-CEC, and 4-BMC in Human Blood using GC-MS
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  61. Antibacterial Activities of Transition Metal complexes of Mesocyclic Amidine 1,4-diazacycloheptane (DACH)
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  67. Optimizing Suitable Conditions for the Removal of Ammonium Nitrogen by a Microbe Isolated from Chicken Manure
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  74. Kinetics of Iron Removal From Ti-Extraction Blast Furnace Slag by Chlorination Calcination
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  78. Cyclodextrin potentiometric sensors based on selective recognition sites for procainamide: Comparative and theoretical study
  79. Greener synthesis of dimethyl carbonate from carbon dioxide and methanol using a tunable ionic liquid catalyst
  80. Nonisothermal Cold Crystallization Kinetics of Poly(lactic acid)/Bacterial Poly(hydroxyoctanoate) (PHO)/Talc
  81. Enhanced adsorption of sulfonamide antibiotics in water by modified biochar derived from bagasse
  82. Study on the Mechanism of Shugan Xiaozhi Fang on Cells with Non-alcoholic Fatty Liver Disease
  83. Comparative Effects of Salt and Alkali Stress on Antioxidant System in Cotton (Gossypium Hirsutum L.) Leaves
  84. Optimization of chromatographic systems for analysis of selected psychotropic drugs and their metabolites in serum and saliva by HPLC in order to monitor therapeutic drugs
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  86. Study on the removal of high contents of ammonium from piggery wastewater by clinoptilolite and the corresponding mechanisms
  87. Phytochemistry and toxicological assessment of Bryonia dioica roots used in north-African alternative medicine
  88. The essential oil composition of selected Hemerocallis cultivars and their biological activity
  89. Mechanical Properties of Carbon Fiber Reinforced Nanocrystalline Nickel Composite Electroforming Deposit
  90. Anti-c-myc efficacy block EGFL7 induced prolactinoma tumorigenesis
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  92. Zagreb Connection Number Index of Nanotubes and Regular Hexagonal Lattice
  93. The Sanskruti index of trees and unicyclic graphs
  94. Valency-based molecular descriptors of Bakelite network BNmn
  95. Computing Topological Indices for Para-Line Graphs of Anthracene
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  98. Topological invariants for the line graphs of some classes of graphs
  99. Words for maximal Subgroups of Fi24‘
  100. Generators of Maximal Subgroups of Harada-Norton and some Linear Groups
  101. Special Issue on POKOCHA 2018
  102. Influence of Production Parameters on the Content of Polyphenolic Compounds in Extruded Porridge Enriched with Chokeberry Fruit (Aronia melanocarpa (Michx.) Elliott)
  103. Effects of Supercritical Carbon Dioxide Extraction (SC-CO2) on the content of tiliroside in the extracts from Tilia L. flowers
  104. Impact of xanthan gum addition on phenolic acids composition and selected properties of new gluten-free maize-field bean pasta
  105. Impact of storage temperature and time on Moldavian dragonhead oil – spectroscopic and chemometric analysis
  106. The effect of selected substances on the stability of standard solutions in voltammetric analysis of ascorbic acid in fruit juices
  107. Determination of the content of Pb, Cd, Cu, Zn in dairy products from various regions of Poland
  108. Special Issue on IC3PE 2018 Conference
  109. The Photocatalytic Activity of Zns-TiO2 on a Carbon Fiber Prepared by Chemical Bath Deposition
  110. N-octyl chitosan derivatives as amphiphilic carrier agents for herbicide formulations
  111. Kinetics and Mechanistic Study of Hydrolysis of Adenosine Monophosphate Disodium Salt (AMPNa2) in Acidic and Alkaline Media
  112. Antimalarial Activity of Andrographis Paniculata Ness‘s N-hexane Extract and Its Major Compounds
  113. Special Issue on ABB2018 Conference
  114. Special Issue on ICCESEN 2017
  115. Theoretical Diagnostics of Second and Third-order Hyperpolarizabilities of Several Acid Derivatives
  116. Determination of Gamma Rays Efficiency Against Rhizoctonia solani in Potatoes
  117. Studies On Compatibilization Of Recycled Polyethylene/Thermoplastic Starch Blends By Using Different Compatibilizer
  118. Liquid−Liquid Extraction of Linalool from Methyl Eugenol with 1-Ethyl-3-methylimidazolium Hydrogen Sulfate [EMIM][HSO4] Ionic Liquid
  119. Synthesis of Graphene Oxide Through Ultrasonic Assisted Electrochemical Exfoliation
  120. Special Issue on ISCMP 2018
  121. Synthesis and antiproliferative evaluation of some 1,4-naphthoquinone derivatives against human cervical cancer cells
  122. The influence of the grafted aryl groups on the solvation properties of the graphyne and graphdiyne - a MD study
  123. Electrochemical modification of platinum and glassy carbon surfaces with pyridine layers and their use as complexing agents for copper (II) ions
  124. Effect of Electrospinning Process on Total Antioxidant Activity of Electrospun Nanofibers Containing Grape Seed Extract
  125. Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C
  126. Topical Issue on Agriculture
  127. The effect of Cladophora glomerata exudates on the amino acid composition of Cladophora fracta and Rhizoclonium sp.
  128. Influence of the Static Magnetic Field and Algal Extract on the Germination of Soybean Seeds
  129. The use of UV-induced fluorescence for the assessment of homogeneity of granular mixtures
  130. The use of microorganisms as bio-fertilizers in the cultivation of white lupine
  131. Lyophilized apples on flax oil and ethyl esters of flax oil - stability and antioxidant evaluation
  132. Production of phosphorus biofertilizer based on the renewable materials in large laboratory scale
  133. Human health risk assessment of potential toxic elements in paddy soil and rice (Oryza sativa) from Ugbawka fields, Enugu, Nigeria
  134. Recovery of phosphates(V) from wastewaters of different chemical composition
  135. Special Issue on the 4th Green Chemistry 2018
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  137. Improved thermally stable oligoetherols from 6-aminouracil, ethylene carbonate and boric acid
  138. The role of a chemical loop in removal of hazardous contaminants from coke oven wastewater during its treatment
  139. Combating paraben pollution in surface waters with a variety of photocatalyzed systems: Looking for the most efficient technology
  140. Special Issue on Chemistry Today for Tomorrow 2019
  141. Applying Discriminant and Cluster Analyses to Separate Allergenic from Non-allergenic Proteins
  142. Chemometric Expertise Of Clinical Monitoring Data Of Prolactinoma Patients
  143. Chemomertic Risk Assessment of Soil Pollution
  144. New composite sorbent for speciation analysis of soluble chromium in textiles
  145. Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green
  146. Photophysical and antibacterial activity of light-activated quaternary eosin Y
  147. Spectral properties and biological activity of La(III) and Nd(III) Monensinates
  148. Special Issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  149. Soil organic carbon mineralization in relation to microbial dynamics in subtropical red soils dominated by differently sized aggregates
  150. A potential reusable fluorescent aptasensor based on magnetic nanoparticles for ochratoxin A analysis
  151. Special Issue on 13th JCC 2018
  152. Fluorescence study of 5-nitroisatin Schiff base immobilized on SBA-15 for sensing Fe3+
  153. Thermal and Morphology Properties of Cellulose Nanofiber from TEMPO-oxidized Lower part of Empty Fruit Bunches (LEFB)
  154. Encapsulation of Vitamin C in Sesame Liposomes: Computational and Experimental Studies
  155. A comparative study of the utilization of synthetic foaming agent and aluminum powder as pore-forming agents in lightweight geopolymer synthesis
  156. Synthesis of high surface area mesoporous silica SBA-15 by adjusting hydrothermal treatment time and the amount of polyvinyl alcohol
  157. Review of large-pore mesostructured cellular foam (MCF) silica and its applications
  158. Ion Exchange of Benzoate in Ni-Al-Benzoate Layered Double Hydroxide by Amoxicillin
  159. Synthesis And Characterization Of CoMo/Mordenite Catalyst For Hydrotreatment Of Lignin Compound Models
  160. Production of Biodiesel from Nyamplung (Calophyllum inophyllum L.) using Microwave with CaO Catalyst from Eggshell Waste: Optimization of Transesterification Process Parameters
  161. The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents
  162. Composite Material Consisting of HKUST-1 and Indonesian Activated Natural Zeolite and its Application in CO2 Capture
  163. Topical Issue on Environmental Chemistry
  164. Ionic liquids modified cobalt/ZSM-5 as a highly efficient catalyst for enhancing the selectivity towards KA oil in the aerobic oxidation of cyclohexane
  165. Application of Thermal Resistant Gemini Surfactants in Highly Thixotropic Water-in-oil Drilling Fluid System
  166. Screening Study on Rheological Behavior and Phase Transition Point of Polymer-containing Fluids produced under the Oil Freezing Point Temperature
  167. The Chemical Softening Effect and Mechanism of Low Rank Coal Soaked in Alkaline Solution
  168. The Influence Of NO/O2 On The NOx Storage Properties Over A Pt-Ba-Ce/γ-Al2O3 Catalyst
  169. Special Issue on the International conference CosCI 2018
  170. Design of SiO2/TiO2 that Synergistically Increases The Hydrophobicity of Methyltrimethoxysilane Coated Glass
  171. Antidiabetes and Antioxidant agents from Clausena excavata root as medicinal plant of Myanmar
  172. Development of a Gold Immunochromatographic Assay Method Using Candida Biofilm Antigen as a Bioreceptor for Candidiasis in Rats
  173. Special Issue on Applied Biochemistry and Biotechnology 2019
  174. Adsorption of copper ions on Magnolia officinalis residues after solid-phase fermentation with Phanerochaete chrysosporium
  175. Erratum
  176. Erratum to: Sand Dune Characterization For Preparing Metallurgical Grade Silicon
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