Dimethyl Carbonate Selectivity Research Articles

Chemical Conversion of CO2: Evaluation of Different Ionic Liquids as Catalysts in Dimethyl Carbonate Synthesis

Dimethyl carbonate (DMC) synthesis from methanol and CO2was investigated using ionic liquids (ILs) as catalysts. ILs based on 1-alkyl-3-methyl imidazolium and N-alkylpyridine cations and [Cl−], [BF4−], [PF6−], [Tf2N−] anions were used in this study. Selectivity in DMC increased in the anion order: [Tf2N−] < [PF6−] < [Cl−] < [BF4−], following the same behavior for both cations. Methanol conversion was similar for all tested ILs. The best result for DMC selectivity (83%) was obtained when [emim][BF4] was used as catalyst. After 5 recycling tests, a loss of 8.5% in the catalyst activity was observed for [bmim][BF4].

Synthesis and characterization of H3PW12O40/Ce0.1Ti0.9O2 for dimethyl carbonate formation via Methanol carbonation

Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 catalysts were synthesized with a sol–gel method to form dimethyl carbonate (DMC) at reaction temperatures T = 110, 170, and 220 °C and volumetric flow-rate ratios CO2/N2 = 1/4, 1/7, and 1/9. The zeolite-like properties of H3PW12O40/Ce0.1Ti0.9O2 with an organized Keggin heteropolyacid structure were demonstrated from X-ray diffraction patterns and Fourier transform infrared spectra. 31P nuclear magnetic resonance spectra indicated that the Keggin heteropolyacid structure was formed through the addition of heteropoly acid (H3PW12O40). The bond lengths between titanium (Ti(IV)) and its adjacent atoms in the first shell (TiO) of Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 were 1.90 and 1.86 Å, respectively, confirmed with EXAFS spectra. At 170 °C and CO2/N2 = 1/7, the optimal methanol conversion (5.5%), DMC selectivity (91.4%), and DMC yield (5.0%) of H3PW12O40/Ce0.1Ti0.9O2 were greater than those of Ce0.1Ti0.9O2. Linear regressions of the pseudo-first-order model indicated that the largest rate constant (4.16 × 10−3 min−1), turnover number (TON = 29.07), and turnover frequency (TOF = 4.85 × 10−2 min−1) of DMC formation were obtained with H3PW12O40/Ce0.1Ti0.9O2 at 170 °C and CO2/N2 = 1/7. A reaction mechanism induced by oxygen vacancies over the surfaces of Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 is proposed to describe the formation of DMC.

Synthesis of dimethyl carbonate from methanol and CO2 over Fe–Zr mixed oxides

A series of Fe–Zr mixed oxides with different Fe content were prepared and used for direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. The best catalytic performance was achieved over the Fe0.7Zr0.3Oy catalyst, with DMC yield of 0.44 mmol·gcat−1 and DMC selectivity of 100% under the reaction conditions of 110°C and 12MPa. Characterization results of N2 physisorption, XRD, XPS, TPR and NH3/CO2-TPD indicated that the Fe–Zr mixed oxides with coexistence structure of hexagonal Fe2O3 and cubic Fe2O3 favored the formation of moderately acidic and basic sites, which then improved the activation of CO2 and methanol. The DMC yield was shown to be linearly related to the amount of moderately acidic and basic sites.

Ceria 촉매상에서 탈수가 DMC 합성에 미치는 영향

In this study, ceriabased catalysts were prepared for dimethyl carbonate (DMC) synthesis and reaction conditions were evaluated for finding the optimal reaction route. In order to find optimal catalysts for DMC synthesis, calcination temperature and Cu(II) impregnation amount were evaluated. The oxidative carbonylation using methanol, carbon monoxide and oxygen and the direct synthesis using methanol and carbon dioxide were introduced for producing DMC. Following the law of Le Chatelier, the dehydration reaction was applied for enhancing the reactivity (methanol conversion) as removing water during the reaction. 2-cyanopyridine, as a chemical dehydration agent, was used. In the case of the oxidative carbonylation, methanol conversion rate increased from 15.1% to 38.7% and the DMC selectivity increased from 0% to 98.8%. In the case of the direct synthesis, methanol conversion rate increased from 1.0% to 77.8% and the DMC selectivity increased from 41.2% to 100.0%.

In silico modeling of human malignant tumors’ reprogramming

NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY catalysts by a high temperature anhydrous interaction between the support and copper (II) acetylacetonate Cu(acac)2. The catalysts were used for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction of H2, X-ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4+ exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4+ exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4+ exchange degree of NaNH4Y, the content of surface bound Cu+ active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu+ content reached its maximum when the NH4+ exchange degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/(g·h) space time yield of DMC, 6.9% conversion of methanol, 68.5% selectivity of DMC.

Nickel sulfate and Interleukine-12 cytokine family: Shedding light on Interleukine-27

NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY catalysts by a high temperature anhydrous interaction between the support and copper (II) acetylacetonate Cu(acac)2. The catalysts were used for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction of H2, X-ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4+ exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4+ exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4+ exchange degree of NaNH4Y, the content of surface bound Cu+ active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu+ content reached its maximum when the NH4+ exchange degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/(g·h) space time yield of DMC, 6.9% conversion of methanol, 68.5% selectivity of DMC.

Effect of NH4+ exchange on CuY catalyst for oxidative carbonylation of methanol

NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY catalysts by a high temperature anhydrous interaction between the support and copper (II) acetylacetonate Cu(acac)2. The catalysts were used for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, temperature programmed reduction of H2, X-ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4+ exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4+ exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4+ exchange degree of NaNH4Y, the content of surface bound Cu+ active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu+ content reached its maximum when the NH4+ exchange degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/(g·h) space time yield of DMC, 6.9% conversion of methanol, 68.5% selectivity of DMC.

Chitosan grafted polymer matrix/ZnCl2/1,8-diazabicycloundec-7-ene catalytic system for efficient catalytic fixation of CO2 into valuable fuel additives

The chitosan grafted polymer matrix/ZnCl2/1,8-diazabicycloundec-7-ene (DBU) novel catalytic system was developed. It was found out that the microwave assisted technique was efficient for chitosan grafting compared to conventional chemical method. The morphology, thermal stability, functional groups, crystalline nature of grafted polymer matrix were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray diffraction (WAXRD) techniques, respectively. SEM images revealed that the surface of chitosan became rough and cross-linked after grafting with amine derivatives. The prepared sorbent showed good CO2 absorption capacity i.e. ∼0.35mmol/g-catalyst, due to the presence of amines and hydroxyl CO2 philic functional groups which shows an obvious positive effect on its CO2 capture capacity. These properties enable this sorbent to be a promising catalyst for dimethyl carbonate (DMC) synthesis from methanol and CO2. DBU was used as a super base for methanol activation by abstracting acidic proton and ZnCl2 for the activation of CO2. Remarkably, the excellent methanol conversion up to ∼23% and ∼99% DMC selectivity were achieved by Ch-g-PEI/ZnCl2/DBU catalysts system at ambient reaction conditions. Catalytic synthesis of organic carbonates is of significant interest both conceptually and practically because this can produce compounds from CO2. This synthesis can provide mild alternative approaches to the direct conversion of CO2 to organic carbonates, an important fuel and building block for organic synthesis.

Novel fabrication of copper oxides on AC and its enhanced catalytic performance on oxidative carbonylation of methanol

Copper oxides (CuOx) nanoparticles dispersed on activated carbon (AC) were prepared by using vapor-phase methanol as the reducing agent. The CuOx/AC as prepared exhibited an enhanced catalytic activity in oxidative carbonylation of methanol to dimethyl carbonate (DMC). The catalytic performance was significantly influenced by reduction conditions including temperature and time. With the similar selectivity of DMC, the space time yield (STY) under optimal reduction conditions reached up to 408mgg−1h−1, which is superior to conventional methods such as thermolysis and solvothermal reduction. Based on the characterization results of XRD, TEM and XPS, the good copper dispersion and high Cu+ content obtained by vapor-phase methanol reduction were mainly responsible for the high catalytic activity.

Direct synthesis of dimethyl carbonate from CO2 and methanol over CeO2 catalysts of different morphologies

The direct synthesis of dimethyl carbonate (DMC) from carbon dioxide (CO2) and methanol is an attractive approach towards conversion of the greenhouse gas - CO2 into value-added chemicals and fuels. Ceria (CeO2) catalyzes this reaction. But the conversion efficiency of CeO2 is enhanced when the byproduct water in the reaction medium is separated by employing trapping agents like 2-cyanopyridine (2-CP). In this work, the influence of morphology of CeO2 on the direct synthesis of DMC in presence of 2-CP is reported. CeO2 catalysts of cube, rod, spindle and irregular morphology (Ce - C, Ce - R, Ce - S and Ce - N, respectively) were prepared, characterized and studied as catalysts in the said reaction conducted in a batch mode. Among all, Ce - S shows superior catalytic performance with nearly 100 mol% of DMC selectivity. Catalytic activity correlates with the concentration of acid and base sites of medium strength as well as defect sites. Ce - S has an optimum number of these active sites and thereby shows superior catalytic performance.

Dimethyl Carbonate Synthesis from Propylene Carbonate with Methanol Using Cu–Zn–Al Catalyst

In the present study, Cu-Zn-Al (CZA) hydrotalcite catalysts prepared by the coprecipitation method and calcined at 300, 500 and 800 °C (named as CZA300, CZA500 and CZA800) were used for the synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate (PC) in a batch reactor. The physicochemical characteristics of the catalysts were analyzed by various methods such as X-ray diffraction (XRD), liquid nitrogen adsorption–desorption textural analysis, energy dispersive atomic spectra (EDAX), scanning electron microscope (SEM), Fourier transformation infrared (FTIR), and NH3- and CO2-temperature-programmed desorption (TPD). The average pore diameter of CZA300, CZA500, and CZA800 catalysts was found to be 55.6, 52.5, and 49.3 Å, respectively. Pore volume distribution analysis revealed that the CZA300 and CZA500 have bimodal pore distribution with pores centered at 36 ± 1 Å and 131 ± 2 Å. CZA300 catalyst has the highest amount of basic sites in weak and strong regions whereas CZA500 catalyst has the highest amount of basic sites in the moderate region. Overall, an increase in the calcination temperature decreased the quantity of basic and acidic sites. CZA catalyst calcined at 300 °C (CZA300), was found to possess the highest basicity, and was found to be most effective during transesterification of PC to form DMC. CZA300 catalyst was further used to study the effect of catalyst dose, reaction time, methanol/PC molar ratio, reaction temperature, and reusability of the catalyst on PC conversion, turn over frequency (TOF), and DMC selectivity. PC conversion of 70% and DMC selectivity of 94% were observed at the optimum operating condition of reaction time = 4 h, methanol/PC molar ratio = 10, catalyst dose = 3 wt % of PC, and temperature = 160 °C.

Polyethylene Glycol Enfolded KBr Assisted Base Catalyzed Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide

Polyethylene glycol enfolded potassium bromide, that is, [K+{PEG}Br–] promoted the synthesis of DMC from the reaction of methanol and carbon dioxide (CO2) using alkali metal based catalyst. The experimental results demonstrated that [K+{PEG}Br–] acted as a promoter and provided up to 12.8% yield with 98% selectivity of dimethyl carbonate (DMC). After completion of the reaction, the reaction products were isolated by distillation and the resulting PEG layer containing potassium bromide (KBr) and potassium carbonate (K2CO3) was efficiently reused for next six runs without significant loss in DMC yield. After the six run, the yield of DMC was found to be 12.1%. In the absence of [K+{PEG}Br–], the reaction between methanol and CO2 using K2CO3 base catalyst provided only 1–2% yield of DMC.

Continuous DMC Synthesis from CO2 and Methanol over a CeO2 Catalyst in a Fixed Bed Reactor in the Presence of a Dehydrating Agent

Methanol and carbon dioxide are continuously and efficiently converted to dimethyl carbonate (DMC) over a CeO2 catalyst using 2-cyanopyridine as a recyclable dehydrating agent in a fixed bed reactor. The process was operated over a wide range of pressure (1–300 bar) by feeding CO2 and the stoichiometric amount of methanol and 2-cyanopyridine mixture into the reactor. The study shows a successful demonstration of direct DMC synthesis mediated by a dehydrating agent with outstanding methanol conversion (>95%) and dimethyl carbonate selectivity (>99%) under optimized conditions. Remarkably higher reaction rates were achieved compared to those in batch operation.

Cerium oxide-based catalysts made by template-precipitation for the dimethyl carbonate synthesis from Carbon dioxide and methanol

This paper mainly describes a novel synthesis of three different ceria catalysts CeO2, CeO2–SiO2 and CeO2-4A via template-precipitation method. The prepared catalysts were fully characterized by means of temperature-programmed desorption (TPD), X-ray powder diffraction (XRD), BET surface area test, SEM and FTIR. The catalytic performance over these ceria catalysts were examined for the dimethyl carbonate (DMC) synthesis from CO2 and methanol. The results indicate that CeO2-4A exhibits the highest DMC yield, followed by CeO2–SiO2 and CeO2 catalysts. Under the reaction conditions at 0.6 MPa and 120 °C with space velocity of 300 h−1, the highest methanol conversion is 3.97% with DMC selectivity of 81.4%.

Synthesis of Dimethyl Carbonate over Activated Carbon Supported Cu Based Catalysts

The supported chloride-free copper based catalyst was prepared by deposition-precipitation method and used to catalyze the direct vapor-phase oxycarbonylation of methanol to dimethyl carbonate (DMC). The effect of reductive agent and copper salt precursor on catalyst structure and catalytic performance were investigated, the catalysts were characterized by XRD, H2-TPR techniques. Using Cu (CH3COO)2 as precursor, glucose as reductive agent, when loading amount was 17.1%, the Cu2O/AC catalyst shows the best performance for DMC synthesis. Under the condition of CO/MeOH/O2=5/11/1, SV=6625h-1, the average STY of DMC in 9 hrs running was 71.96mg/(g·h), and selectivity of DMC was 83.13%.

The direct synthesis of dimethyl carbonate by the oxicarbonylation of methanol over Cu supported on carbon nanotube

The activity of Cu/MWCNT and Cu–Ni/MWCNT catalysts was investigated in the synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol. The catalysts were prepared via conventional incipient wetness impregnation technique. The samples were characterized by X-ray photoelectron spectroscopy (XPS), and DRIFT. The reaction was carried out in a continuous flow system at atmospheric pressure at 393K. The main products were methyl formate (MF), DMC and CO2. The methanol conversion on Cu/MWCNT achieved a steady state value after 2h, but on Cu–Ni/MWCNT the conversion decreased continuously. The DMC selectivity was more than 30% and the yield was 1.2% on Cu/MWCNT. Based on the XPS data we can establish that copper reduced to its metallic form during reduction but oxidized in the reaction mixture, and is mostly in the Cu+ state, with some Cu2+ also present on the surface at the beginning of the reaction though its ratio decreased in time. We assume that the DMC formation rate depends on the surface concentration of oxidized Cu. Based upon the FTIR data adsorbed DMC is present on the surface of the Cu/MWCNT catalyst during the catalytic reaction but on Cu–Ni/MWCNT sample only methyl formate was detected in the gas phase.

Two-step synthesis of dimethyl carbonate from urea, ethylene glycol and methanol using acid–base bifunctional zinc-yttrium oxides

The binary zinc-yttrium oxides with different precursors were prepared by co-precipitation method and used in the catalytic synthesis of dimethyl carbonate (DMC) via a two-step process using urea, ethylene glycol and methanol as raw feed-stocks. The first step involves reaction of urea with ethylene glycol (EG) to form ethylene carbonate (EC), and 96% conversion of urea with 98% selectivity of EC was obtained. In the second step, namely transesterification of EC formed with methanol to give DMC and EG, the conversion of EC was up to 72% in 15min with a 99% selectivity of DMC, corresponding to a TOF of 864mmol/hgcat. XRD results showed that the catalyst with a zinc nitrate precursor has a remarkable interaction between zinc and yttrium oxides. TPD characterization indicated that in the catalyst with a zinc nitrate precursor there was a cooperative effect between weak acid and medium base sites on the surface of the catalyst, suggesting that the prepared catalysts are acid–base bifunctional. The synergistic effect between zinc and yttrium oxides, in combination with acidity of zinc oxide and basicity of yttrium oxide, may be responsible to the high catalytic activity and selectivity.

Highly efficient catalyst PdCl2–CuCl2–KOAc/AC@Al2O3 for gas-phase oxidative carbonylation of methanol to dimethyl carbonate: Preparation and reaction mechanism

The supported Wacker catalysts previously used for the synthesis of dimethyl carbonate (DMC) by gas-phase oxidative carbonylation of methanol have the drawbacks of low selectivity and poor catalytic stability. To solve these problems, PdCl2–CuCl2–KOAc/AC was treated by both Al2O3 and dilute hydrochloric acid to obtain PdCl2–CuCl2–KOAc/AC@Al2O3 in this work. The treatment brought about not only the higher activity but also the better stability and selectivity: 98% of DMC selectivity to methanol, 70% of DMC selectivity to CO, and space–time yield of DMC ranging from 600 to 700gL-cat−1h−1 for the runtime of 40h. PdCl2–CuCl2–KOAc/AC@Al2O3 was characterized and the results showed that it possessed enlarged specific surface area (BET), enriched active components on the surface (SEM), increased proportion of Cu+/Cu2+ and new Cu2O crystalline phase formed (XPS), as compared with PdCl2–CuCl2–KOAc/AC. The new formed Cu2O can be used not only as a catalyst for the synthesis of DMC but also as an inhibitor for the loss of Cl− by the reaction of Cu2O with Cl− to CuCl, resulting in the promotion of the catalytic stability. The characterization of the recovered catalyst further identified that the inhibition of KCl crystal formation and the increase in Cu+/Cu2+ proportion could improve the catalytic stability and selectivity. In addition, the higher ratio of Cu+/Cu2+ can reduce Pd2+ concentration and prohibited side-reaction of CO oxidation, so DMC selectivity to CO is increased. On the basis of activity evaluation and characterization, the catalytic reaction mechanism is proposed.

Highly efficient enzymatic preparation for dimethyl carbonate catalyzed by lipase from Penicillium expansum immobilized on CMC–PVA film

Herein we demonstrated a novel biocatalytic route for the synthesis of dimethyl carbonate (DMC) by the transesterification of ethylene carbonate with methanol. Immobilization of lipase from Penicillium expansum using environmentally benign and biodegradable film prepared using a blend of carboxymethyl cellulose and polyvinyl alcohol has significantly enhanced the catalytic activity. The biocatalyst revealed high catalytic performance under ambient pressure and low temperature. Even after 4 cycles, the catalysts still remained relatively active. • A novel biocatalytic route for the preparation of dimethyl carbonate is reported. • The catalytic activity enhanced significantly by the immobilization of lipase. • No other organic solvents were added in this efficient biocatalytic process. • Even after 4 cycles, the catalysts still remained relatively active. Herein, we demonstrated a environmental-friendly biocatalytic route for the synthesis of dimethyl carbonate (DMC), which is the first example to use enzyme in the process. Moreover, immobilization of Penicillium expansum lipase (PEL) using environmentally benign and biodegradable CMC–PVA polymer has significantly enhanced the catalytic activity thus making them an eligible biocatalyst for synthesis of DMC. The biocatalyst revealed high catalytic performance even under ambient pressure and low temperature (conversion of EC to 94%, yield of DMC to 93% and selectivity of DMC to 99%). The immobilized lipase was effectively recycled for four consecutive cycles providing good yields of the desired product. Accompanying with the intense requirement for the green chemicals and process, our work can provide a useful idea for “green and clean” of harmful chemical reaction.

Effects of Mo promoters on the Cu–Fe bimetal catalysts for the DMC formation from CO2 and methanol

Abstract The Mo-promoted Cu–Fe bimetal catalysts were prepared and used for the formation of dimethyl carbonate (DMC) from CO2 and methanol. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), laser Raman spectra (LRS), energy dispersive spectroscopy (EDS) and temperature programmed desorption (TPD) techniques. The experimental results demonstrated that the Mo promoters can decrease the reducibility and increase the dispersion of Cu–Fe clusters. The concentration balance of base–acid sites can be readily adjusted by changing the Mo content. The moderate concentration balance of acid and base sites was in favor of the DMC formation. Under optimal experimental conditions, the highest methanol conversion of 6.99% with a DMC selectivity of 87.7% can be obtained when 2.5 wt% of Mo was loaded.