Synthesis Of Dimethyl Carbonate Research Articles

One-step DMC synthesis from CO2 under catalysis of ionic liquids prepared with 1,2-propylene glycol

Three quaternary ammonium ionic liquids with strong nucleophilicity and distinctive structures were synthesized with high yield and purity based on the 1,2-propylene glycol anion (CH3CH2OHCH2O-) derived from transesterification products. Dimethyl carbonate (DMC) was in turn produced via a one-step reaction among propylene oxide (PO), CO2, and methanol (MeOH) by using the synthesized ionic liquids. The involved two-stage catalytic reaction of PO-CO2 cycloaddition and PC-MeOH transesterification was implemented without catalyst separation. Under mild conditions, the PO conversion reached 99.0%, with a PC yield of 99.0%, and a TON value of 119.5. Following the cycloaddition, MeOH was immediately introduced to achieve a PC conversion of 71.2%, a selectivity to DMC above 99%, and a TON value of 57.4 for the transesterification reaction. The influences of temperature as well as time for cycloaddition and transesterification were investigated. Cycloaddition of CO2 with various epoxides was also examined and all showed good performance. By taking advantage of the decomposability of as-prepared ionic liquids and the recyclability of decomposition products, a new catalyst circulation process was designed to complete the full cycle without introduction of any impurities into the product system.

Hierarchical Catalysts Based on Cerium(IV) Oxide for Direct Synthesis of Dimethyl Carbonate

Hierarchical Catalysts Based on Cerium(IV) Oxide for Direct Synthesis of Dimethyl Carbonate

Zn‐Doped CeO2 Nanorods: a Highly Efficient Heterogeneous Catalyst for the Direct Synthesis of Dimethyl Carbonate from CO2 and Methanol

AbstractThe direct synthesis of dimethyl carbonate from methanol and CO2 is a green and sustainable processes. In this paper, a new type of Zn‐doped CeO2 nanorods catalyst was successfully prepared by a facile hydrothermal process, and characterized by a combination of techniques including XRD, Raman, HRTEM, SEM, N2‐sorption, CO2‐TPD, NH3‐TPD, XPS. The catalyst was employed as a catalyst for the synthesis of dimethyl carbonate from methanol and CO2. Catalytic results revealed that the Ce1Zn0.1Oδ nanorods catalyst demonstrated superior catalytic activity, affording a high DMC yield of 24.2 mmolDMC/gcat, which compared favorably to other previously reported catalysts. According to the XPS and CO2‐TPD measurements, in comparison with the pure CeO2 nanorods, the surface oxygen vacancies and weak basic sites can be systemically enriched by introducing optimal amount of Zn dopants into CeO2 to improve the catalytic activity for the reaction. This work establishes an efficient catalyst for the direct synthesis of dimethyl carbonate from CO2 and methanol.

Carbon template synthesis of CeO2 catalyst for direct conversion of methanol and carbon dioxide to dimethyl carbonate

Dimethyl carbonate (DMC) is an interesting, value added chemical and a high energy additive to fuels. In this study, several CeO2 catalysts were successfully synthesized through carbon template method using two renewable sources of activated carbon. The structure of catalysts was fully resolved by XRD, SEM, N2-adsorption, NH3-TPD, CO2-TPD and XPS. CeO2 catalysts prepared using coconut shell activated carbon (CAC) template exhibit better surface morphology and improved catalytic performance compared to walnut shell activated carbon (WAC)-supported catalysts. We demonstrated a correlation between the efficiency of DMC synthesis and the abundance of moderately acidic and moderately basic active sites on the catalyst. It was found that the presence of oxygen vacancies (Vo) facilitates carbonyl bond cleavage of CO2. The best-performing catalyst was 4% CeO2/CAC owing to the richest Vo and the optimum acid/base properties. Moreover, a plausible catalytic mechanism of DMC formation was proposed, and includes the interaction between methoxy carbonate (CH3OCO2−) formed with the aid of Vo and moderately basic sites and methyl cation (CH3+) formed on the moderately acidic sites.

Dimethyl carbonate synthesis from CO2 and methanol over CeO2: elucidating the surface intermediates and oxygen vacancy-assisted reaction mechanism

Oxygen vacancy-assisted reaction mechanisms and key surface intermediates were uncovered by operando spectroscopic and DFT-based molecular dynamics simulations in direct dimethyl carbonate (DMC) synthesis from CO2 and methanol over CeO2 catalyst.

Homogeneous base catalyst with high activity and stability for synthesis of dimethyl carbonate by transesterification.

In the synthesis of dimethyl carbonate (DMC) by transesterification, CH3ONa has been commonly applied as a homogeneous catalyst due to its high catalytic activity, but its stability is unsatisfactory. Here, by studying the influence of ionic liquid base strength on transesterification, we prepared an organic base catalyst, potassium imidazole (KIm), with high catalytic activity and stability, which solved the problem of catalyst deactivation in transesterification. The results showed that when KIm was used in the synthesis of DMC from propylene carbonate (PC) and methanol (MeOH), the chemical equilibrium could be reached within 3 minutes and the yield of DMC reached 73.03%, indicating that KIm performed better in transesterification than the majority of previously reported catalysts. In addition, the activity of the catalyst had hardly decreased after ten cycles of reaction, which can well meet the requirements of industrial production.

Efficient and stable catalysts for the synthesis of dimethyl carbonate by carbonylation of methyl nitrite applying the starch-coated activated carbon as a support

For the synthesis of dimethyl carbonate (DMC) by carbonylation of methyl nitrite (MN), the lack of efficient and stable catalysts is a crucial factor limiting the application of this technology.

Surface species in direct liquid phase synthesis of dimethyl carbonate from methanol and CO2: an MCR-ALS augmented ATR-IR study.

The reaction mechanism of dimethyl carbonate (DMC) production over ZrO2 from CO2 and CH3OH is well-known, but the level of understanding has not improved in the last decade. Most commonly, the reaction mechanism has been explored in the gas phase, whilst DMC production occurs in the liquid phase. To overcome this contradiction, we exploited in situ ATR-IR spectroscopy to study DMC formation over ZrO2 in the liquid phase. A multiple curve resolution-alternate least square (MCR-ALS) approach was applied to spectra collected during the CO2/CH3OH interaction with the catalyst surface, leading to the identification of five pure components with their respective concentration profiles. CO2 and CH3OH activation to carbonates and methoxide species was found to strongly depend on the reaction temperature. Low temperature prevents methanol dissociation leaving a catalyst covered with stable carbonates, whilst higher temperature decreases the stability of the carbonates and enhances the formation of methoxides. A reaction path involving the methoxide/carbonate interaction at the surface was observed at low temperature (≤50 °C). We propose that a different reaction path, independent of carbonate formation and involving the direct CO2/methoxide interplay, occurs at 70 °C.

Microscopic mechanism study and process optimization of dimethyl carbonate production coupled biomass chemical looping gasification system

Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources. At the same time, dimethyl carbonate can replace phosgene as an environment-friendly organic material for the synthesis of polycarbonate. In this paper, a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization. Firstly, reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range. Secondly, steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature, steam to biomass ratio, and oxygen carrier to biomass ratio on the syngas yield and compositions. In addition, the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters. Then, two synthesis stages are simulated and optimized with the following results obtained: the optimal temperature and pressure of methanol synthesis stage are 150 °C and 4 MPa; the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140 °C and 0.3 MPa. Finally, the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11% purity of dimethyl carbonate. Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.

Cerium doped Zr-based metal-organic framework as catalyst for direct synthesis of dimethyl carbonate from CO2 and methanol

The disadvantage of Ce/Zr metal oxide as catalyst for direct synthesis dimethyl carbonate (DMC) from CO2 and methanol is low DMC formation rate because of its low specific surface area and active sites. In this work, it can be improved by highly uniform dispersion cerium doped Zr-based metal-organic frameworks (UiO-66 MOFs), which were synthesized via a modified hydrothermal method. The as-prepared catalysts have been extensively characterized using XRD, BET, FT-IR, SEM, TEM, TGA, NH3-TPD, CO2-TPD, XPS techniques. Experimental evaluation results indicated that the highly uniform dispersed Ce-doped UiO-66 MOFs exhibited markedly improved catalytic performance than traditional Ce/Zr metal oxide catalyst. The highest yield of DMC catalyzed by Ce-UiO-66–2 was 0.295% (reaction time was 12 h; reaction temperature was 140 °C; reaction pressure was 11 MPa). Then, it was found that doping of Ce atoms into the zirconium lattice to produce UiO-66 MOFs could effectively increase the number of acidic and medium basic sites than UiO-66 (none Ce), thus could greatly enhance the catalytic performance. Moreover, using 2-cyanopyridine as dehydrating agent, the DMC yield could be further raised greatly. Last, based on reported literature and our results, a possible reaction mechanism over Ce-UiO-66-X was proposed.

Atom-Economical Synthesis of Dimethyl Carbonate from CO2 : Engineering Reactive Frustrated Lewis Pairs on Ceria with Vacancy Clusters.

The chemical conversion of CO2 to long-chain chemicals is considered as a highly attractive method to produce value-added organics, while the underlying reaction mechanism remains unclear. By constructing surface vacancy-cluster-mediated solid frustrated Lewis pairs (FLPs), the 100 % atom-economical, efficient chemical conversion of CO2 to dimethyl carbonate (DMC) was realized. By taking CeO2 as a model system, we illustrate that FLP sites can efficiently accelerate the coupling and conversion of key intermediates. As demonstrated, CeO2 with rich FLP sites shows improved reaction activity and achieves a high yield of DMC up to 15.3 mmol g-1 . In addition, by means of synchrotron radiation in situ diffuse reflectance infrared Fourier-transform spectroscopy, combined with density functional theory calculations, the reaction mechanism on the FLP site was investigated systematically and in-depth, providing pioneering insights into the underlying pathway for CO2 chemical conversion to long-chain chemicals.

Atom‐Economical Synthesis of Dimethyl Carbonate from CO2: Engineering Reactive Frustrated Lewis Pairs on Ceria with Vacancy Clusters

AbstractThe chemical conversion of CO2to long‐chain chemicals is considered as a highly attractive method to produce value‐added organics, while the underlying reaction mechanism remains unclear. By constructing surface vacancy‐cluster‐mediated solid frustrated Lewis pairs (FLPs), the 100 % atom‐economical, efficient chemical conversion of CO2to dimethyl carbonate (DMC) was realized. By taking CeO2as a model system, we illustrate that FLP sites can efficiently accelerate the coupling and conversion of key intermediates. As demonstrated, CeO2with rich FLP sites shows improved reaction activity and achieves a high yield of DMC up to 15.3 mmol g−1. In addition, by means of synchrotron radiation in situ diffuse reflectance infrared Fourier‐transform spectroscopy, combined with density functional theory calculations, the reaction mechanism on the FLP site was investigated systematically and in‐depth, providing pioneering insights into the underlying pathway for CO2chemical conversion to long‐chain chemicals.

Integrated DFT and experimental study on Co3O4/CeO2 catalyst for direct synthesis of dimethyl carbonate from CO2

The oxygen deficient site on the catalyst has a strong impact on the activation of CO2 for the synthesis of dimethyl carbonate (DMC). The Co3O4/CeO2 catalyst exhibits multiple reduction behavior as cobalt metal species differ in the strength of their interaction with CeO2. This causes the surface reduction from Ce4+ to Ce3+ in solid solution Co-O-Ce. The dispersion of Co3O4 enhanced the formation of oxygen deficient site as revealed by XPS, CO2-chemisorption and TPR. The non-precious Co3O4/CeO2 nanorod was recognized as a potential catalyst for promoting Ce4+ to Ce3+ for CO2 activation and dimethyl carbonate synthesis (81.5% of yield). Energetics of oxygen vacancy formation of low index surfaces of CeO2 was determined with first-principles calculations based on DFT. Results disclosed the Ce4+ to Ce3+ formation energy of CeO2 due to Co substitution and corroborated the experimental results. Further, calculations provide the details of the effect of Co substitution on the electronic structure of reduced CeO2 surfaces. Estimated CO2 adsorption energy indicates (110) as the most active surface for activation of CO2.

Dimethyl Carbonate Synthesis via Transesterification of Propylene Carbonate Using a Titanium–Praseodymium-Based Catalyst

Dimethyl Carbonate Synthesis via Transesterification of Propylene Carbonate Using a Titanium–Praseodymium-Based Catalyst

An Intensified Green Process for the Coproduction of DMC and DMO by the Oxidative Carbonylation of Methanol

Dimethyl carbonate (DMC) is an eco-friendly and sustainable compound with widespread industrial applications. Various extensive routes have been exploited in the chemical industry to produce DMC. However, these routes have several environmental and energy drawbacks. In this study, a promising novel industrial scheme for the synthesis of DMC via the oxidative carbonylation of vaporized methanol with dimethyl oxalate (DMO) as a byproduct is investigated. A methanol conversion of 81.86% and a DMC selectivity of 83.47% were achieved using an isothermal fixed-bed reactor at 130 °C. The DMC is withdrawn at a purity of >99 mol% via pressure-swing azeotropic distillations. Heat integration was performed to optimize energy consumption, reducing the energy requirements by 28%. An economic evaluation was performed for estimating the profitability via cash-flow diagrams, predicting a payback period of 3.7 years. The proposed green process exhibits several benefits, including high profitability and being environmentally friendly. It also eliminates the use or production of hazardous materials, and it enhances safety characteristics.

The role of Ce doping on the activity of La2O2CO3 nanosheets catalysts in synthesis of dimethyl carbonate from propylene carbonate and methanol

Dimethyl carbonate (DMC) production from the transesterification reaction of propylene carbonate (PC) and methanol is an eco-friendly and economical process with propylene glycol (PG) as the high value-added co-product. We report herein the synthesis of Ce-doped La2O2CO3 nanosheets (La1Cex) with varying Ce contents through a solvothermol method. La1Ce0.15 catalyst exhibits superior catalytic performance in the production of DMC by the transesterification of methanol and PC. A remarkable improvement in PC conversion (> 85%) and DMC selectivity (> 98%) can be attributed to an increase in surface O2− base sites caused by increased oxygen interstitials and vacancies through Ce doping.

Highly efficient super activated carbon supported ultra-low loading copper catalyst for the oxidative carbonylation of methanol to dimethyl carbonate

A series of copper catalysts with loading less than 1.0 wt% supported on super activated carbon (SAC, 2403 m2·g−1) as well as commercial activated carbon (AC, 1297 m2·g−1) were produced by the wet-impregnation process and applied in methanol oxidative carbonylation to generate dimethyl carbonate (DMC). The 0.5Cu/SAC catalyst showed highly dispersed Cu nanoparticles (NPs, ∼2.2 nm) and exhibited a turnover frequency (44.6 h−1) about four times higher than that of 0.5Cu/AC. The characterization results indicate that the large specific surface area of SAC greatly promoted the dispersion of Cu NPs. In addition, the abundant oxygen-containing groups on SAC enhanced interaction between Cu NPs and carbon support, which maintained the concentration of active Cu0 sites and facilitated high stability of Cu/SAC catalysts during the reaction. This research provided a novel strategy for fabricating low loading Cu-based catalysts with commercial prospects for the DMC synthesis.

Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC

This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO2) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. CeO2 nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH4) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm2). The ultrasonically assisted surface modification of the CeO2 nanospindles in NaBH4 led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce3+ and oxygen vacancies. The surface modified CeO2 nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·gcat−1 with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO2 surface, and it can further be applied for other chemical activities.

Synthesis of highly effective [Emim]IM applied in one-step CO2 conversion to dimethyl carbonate

Ionic liquid 1-ethyl-3-methylimidazolium ([Emim]IM) with high thermal stability and strong basicity was successfully synthesized. Using [Emim]IM as catalyst, dimethyl carbonate (DMC) was directly synthesized from epoxy propane (PO), CO2, and methanol under mild reaction conditions. A continuous two-stage DMC synthesis process was developed. The cycloaddition of CO2 and PO was first conducted to produce propylene carbonate (PC), and then methanol was introduced into the system to synthesize DMC. During the cycloaddition process, 97.40% PO conversion and 97.40% PC yield were achieved with TON of 99.49. In the subsequent transesterification stage, DMC yield attained 83.63% with selectivity higher than 99% and TON of 70.15. [Emim]IM was reused for seven times without obvious deactivation, exhibiting good stability. The effects of reaction temperature, reaction time, the initial pressure of CO2, and catalyst weight on cycloaddition and transesterification reactions were systematically investigated. The kinetic study showed that the activation energies (Ea) of cycloaddition and transesterification reactions were 28.02 and 38.53 KJ·mol−1, respectively, much lower than those of catalysts reported in the literatures. In addition, [Emim]IM displayed superior catalytic activity for the cycloaddition of CO2 with various epoxy compounds.

New Strategies on Green Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol over Oxide Composites.

Dimethyl carbonate is a generally used chemical substance which is environmentally sustainable in nature and used in a range of industrial applications as intermediate. Although various methods, including methanol phosgenation, transesterification and oxidative carbonylation of methanol, have been developed for large-scale industrial production of DMC, they are expensive, unsafe and use noxious raw materials. Green production of DMC from CO2 and methanol is the most appropriate and eco-friendly method. Numerous catalysts were studied and tested in this regard. The issues of low yield and difficulty in tests have not been resolved fundamentally, which is caused by the inherent problems of the synthetic pathway and limitations imposed by thermodynamics. Electron-assisted activation of CO2 and membrane reactors which can separate products in real-time giving a maximum yield of DMC are also being used in the quest to find more effective production method. In this review paper, we deeply addressed green production methods of DMC using Zr/Ce/Cu-based nanocomposites as catalysts. Moreover, the relationship between the structure and activity of catalysts, catalytic mechanisms, molecular activation and active sites identification of catalysts are also discussed.