Readily-fabricated supported MgO catalysts for efficient and green synthesis of diethyl carbonate from ethyl carbamate and ethanol

Developing cost-effective, high-efficiency and heterogeneous catalysts is of prime importance for the green synthesis of diethyl carbonate (DEC) from ethyl carbamate (EC) and ethanol. Herein, a series of MgO/γ-Al2O3 catalysts were readily fabricated by an impregnation method for DEC synthesis from EC and ethanol. The activities of the as-prepared MgO/γ-Al2O3 catalysts as well as the individual MgO or γ-Al2O3 were first tested in the batch reactor. Among the investigated samples, the MgO/γ-Al2O3 with a MgO loading of 10 wt% (denoted as 10% MgO/γ-Al2O3) exhibited the largest amount of stronger basic sites, and the highest activities with EC conversion of 41.8% and DEC yield of 30.4%, respectively. Furthermore, the DEC yield was greatly boosted to 52.1% with a high DEC selectivity of 93.8% over the 10% MgO/γ-Al2O3 catalyst under the optimized reaction conditions in the fixed bed reactor, outperforming most of the reported catalysts.

Effect of Preparation Method on the Catalytic Property of Calcined Ca-Al Hydrotalcite for the Synthesis of Ethyl Methyl Carbonate

Calcined Ca-Al hydrotalcites were prepared by a clean method (CaAl-1) and coprecipitation (CaAl-2), respectively. Effects of preparation methods on the structure and catalytic property of calcined Ca-Al hydrotalcites were investigated. The samples were characterized by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG), CO2-programmed temperature desorption method (CO2-TPD), low-temperature N2 adsorption-desorption, and the Hammett indicator method. Compared with CaAl-2, CaAl-1 had a higher specific surface area and surface alkali density, which makes it have relatively higher catalytic activity for transesterification synthesis of ethyl methyl carbonate (EMC). Also, a 50.6% yield of EMC was obtained in the presence of 1.5% CaAl-1 at 100 °C in 1 h. Moreover, the catalytic activity of CaAl-1 showed no remarkable change after five runs.

Solvent-Free Synthesis of Jasminaldehyde in a Fixed-Bed Flow Reactor over Mg-Al Mixed Oxide

In spite of the rapid developments in synthesis methodologies in different fields, the traditional methods are still used for the synthesis of organic compounds, and regardless of the type of chemistry, these reactions are typically performed in standardized glassware. The high-throughput chemical synthesis of organic compounds such as fragrant molecules, with more economic benefits, is of interest to investigate and develop a process that is more economical and industrially favorable. In this research, the catalytic activity of Mg-Al catalyst derived from hydrotalcite-like precursors with the Mg/Al molar ratio of 3 was investigated for the solvent-free synthesis of jasminaldehyde via aldol condensation of benzaldehyde and heptanal. The reaction was carried out in a fixed-bed flow reactor, at 1 MPa, and at different temperatures. Both Brønsted and Lewis (O2− anions) base sites, and Lewis acid sites exist on the surface of the Mg-Al catalyst, which can improve the catalytic performance. Increasing the reaction temperature from 100 °C to 140 °C enhanced both heptanal conversion and selectivity to jasminaldehyde. After 78 h of reaction at 140 °C, the selectivity to jasminaldehyde reached 41% at the heptanal conversion 36%. Self-condensation of heptanal also resulted in the formation of 2-n-pentyl-2-n-nonenal. The presence of weak Lewis acid sites creates a positive charge on the carbonyl group of benzaldehyde, and makes it more prone to attack by the carbanion of heptanal. Heptanal, is an aliphatic aldehyde, with higher activity than benzaldehyde. Therefore, the possibility of activated heptanal reacting with other heptanal molecules is higher than its reaction with the positively charged benzaldehyde molecule, especially at a low molar ratio of benzaldehyde to heptanal.

Environment-friendly synthesis of diethyl carbonate via ethyl carbamate alcoholysis over cerium oxide catalyst

A series of cerium oxide catalysts were prepared by simply calcination of nitrate cerium, and used for clean synthesis of diethyl carbonate (DEC) by ethyl carbamate (EC) alcoholysis. 51% conversion and 82% selectivity were obtained with catalyst CeO₂-600. Almost the same activity as the fresh sample could be regained if the used catalyst was recalcined at 600 °C. XPS, XRD, CO₂-TPD and BET study suggested that high surface area and the presence of abundant basic sites are important to achieve a higher catalytic performance.

Direct synthesis of diethyl carbonate from ethanol and carbon dioxide over ceria catalysts

Direct synthesis of diethyl carbonate (DEC) from ethanol and CO₂was investigated over “neat” and metal incorporated ceria catalysts. An optimal dependence (“volcanic plot”) of the catalytic activity on the acidity/basicity molar ratio was observed.

Iron-Catalyzed Reaction of Urea with Alcohols and Amines: A Safe Alternative for the Synthesis of Primary Carbamates

A general study of the iron-catalyzed reaction of urea with nucleophiles is here presented. The carbamoylation of alcohols allows for the synthesis of N-unsubstituted (primary) carbamates, including present drugs (Felbamate and Meprobamate), without the necessity to apply phosgene and related derivatives. Using amines as nucleophiles gave rise to the respective mono- and disubstituted ureas via selective transamidation reaction. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and readily available urea using a simple Lewis-acidic iron(II) catalyst.

Diethyl carbonate: critical review of synthesis routes, catalysts used and engineering aspects

Diethyl carbonate (DEC) is a well-known linear organic carbonate that has wide applications.

Converting urea into high value-added 2-oxazolidinones under solvent-free conditions

Solvent-free synthesis of 2-oxazolidinones from urea and epoxides over Zn-modified mesoporous Mg–Al nano-oxides.

Efficient synthesis of diphenyl carbonate from dibutyl carbonate and phenol using square-shaped Zn–Ti–O nanoplates as solid acid catalysts

Efficient synthesis of diphenyl carbonate from dibutyl carbonate and phenol using square-shaped Zn–Ti–O nanoplates as solid acid catalyst.

Separation of dibutyl carbonate/butyl carbamate close-boiling mixture using imidazolium-based ionic liquids

The separation of dibutyl carbonate (DBC) from butyl carbamate (BC) using ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl).