The efficient synthesis of diethyl carbonate via coupling reaction from propylene oxide, CO2 and ethanol over binary PVEImBr/MgO catalyst

Observed kinetics for the production of diethyl carbonate from CO2 and ethanol catalyzed by CuNi nanoparticles supported on activated carbon

Monometallic and bimetallic Cu:Ni catalysts with different Cu:Ni molar ratios (3:1, 2:1, 1:1, 1:2, 1:3) were synthesized by wetness impregnation on activated carbon and characterized by TPR (temperature programmed reduction), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy). The synthesized catalysts were evaluated in the gas phase production of diethyl carbonate from ethanol and carbon dioxide. The largest catalytic activity was obtained over the bimetallic catalyst with a Cu:Ni molar ratio of 3:1. Its improved activity was attributed to the formation of a Cu-Ni alloy on the surface of the catalyst, evidenced by XPS and in agreement with a previous assignment based on Vegard law and TPR analysis. During the reaction rate experiments, it observed the presence of a maximum of the reaction rate as a function of temperature, a tendency also reported for other carbon dioxide-alcohol reactions. It showed that the reaction rate-temperature data can be adjusted with a reversible rate equation. The initial rate as a function of reactant partial pressure data was satisfactorily adjusted using the forward power law rate equation and it was found that the reaction rate is first order in CO2 and second order in ethanol.

Product Yield Increasing More Than 20 Times Achieved by Reducing Water Poisoning for Direct Diethyl Carbonate Synthesis

Diethyl carbonate (DEC) synthesis from CO2 and ethanol is a typical green chemical route for sustainable development and cleaner production. However, the bottleneck problem of a low DEC yield is still not solved at present. The DEC yield still maintains 0.5-5.0% unless expensive third additives are added. Compared to the cheap price of DEC, the third additives are generally more expensive. It is not advisible to use expensive chemicals to prepare cheap chemicals. In this work, the (ZrO2)1.0/(Fe2O3)1.0 catalyst was prepared by a novel template-precipitation method and the DEC yield of the DEC direct synthetic reaction only from CO2 and ethanol without third additives obtained 1.95%. After a series of supported catalysts were prepared, the DEC yield reached up to 46.1% for the (ZrO2)1.0/(Fe2O3)1.0@3A-CaO-CaC2 catalyst. This carrier can also be applied to other catalyst systems. CO2-TPD, NH3-TPD, and XRD were measured to analyze the microstructure and catalytic mechanism. Active center site theory was proposed to explain the intrinsic mechanism of catalyst activity. This new discovery of the mechanism and the DEC yield removed obstacles for the application of this reaction.

Facile one pot synthesis of 2-substituted benzimidazole derivatives under mild conditions by using engineered MgO@DFNS as heterogeneous catalyst

Benzimidazole derivatives are considered as important heterocyclic motifs that show a wide range of pharmaceutical applications. In view of their wide-ranging bioactivities, it is imperative to direct research on the sustainable catalytic synthesis of benzimidazole. Therefore, herein, we report a novel approach for the synthesis of benzimidazole and its derivatives with engineered MgO supported on dendritic fibrous nano silica (MgO@DFNS) as a sustainable heterogeneous catalyst. The catalyst MgO@DFNS was thoroughly characterized to understand its physio-chemical properties using XRD, FE-SEM, XPS, FT-IR, zeta potential, HR-TEM, TGA, TPR and TPD. The obtained results suggested that the catalyst MgO@DFNS prepared well and have the desired characteristics in it. After the successful characterisation of the prepared catalyst MgO@DFNS, it was applied in the synthesis of benzimidazole derivatives via condensation of o-phenylenediamine, and various aromatic and aliphatic aldehydes under ambient temperature. The catalyst produced a clean reaction profile with excellent yields in a shorter time under the umbrella of green chemistry. The effect of reaction parameters such as the effect of time, catalyst dosage, loading of MgO, effect of solvents and effect of different homo and heterogeneous catalyst were also tested. Furthermore, to understand the scope of the catalyst different substituted diamines and substituted aldehydes were reacted and obtained desired products in good to efficient yield. In addition, a recyclability study was also conducted and it was observed that the catalyst could be recycled for up to six cycles without noticeable changes in the morphology and activity. We believe that the present methodology gave several advantages such as an eco-friendly method, easy work-up, good selectivity, high yields and quick recovery of catalyst. MgO@DFNS is highly stable for several cycles without significant loss of its activity, which possibly demonstrates its applicability at the industrial scale.

Efficient synthesis of epoxybutane from butanediol via a two-step process

A novel approach for the synthesis of epoxybutane via decarboxylation of butenyl carbonate derived from butanediol was developed for the first time. For the carbonylation of butanediol with dimethyl carbonate, NaAlO₂ has exhibited excellent catalytic activity under mild reaction conditions. The yield of butenyl carbonate reached as high as 96.2%. NaAlO₂ provides suitable acid-base active sites to promote the transesterification reaction of butanediol and dimethyl carbonate. For the following step of decarboxylation of butenyl carbonate, ionic liquid 1-butyl-3-methylimidazolium bromide could effectively catalyze the decarboxylation process both in batch or continuous processes. Moreover, the catalytic mechanism for the crucial step of decarboxylation of butenyl carbonate over 1-butyl-3-methylimidazolium bromide was explored using DFT calculations. The results showed that the electrostatic and hydrogen-bond effects of 1-butyl-3-methylimidazolium bromide played a crucial role for the generation of epoxybutane. Briefly, the Br anion of the ionic liquid attacks the methylene of the ring and the H of the ionic liquid cation attacks the carbonyl oxygen, which facilitated the five-ring opening and subsequent decarboxylation to form BO. This study not only provided a new and green synthetic route for producing epoxybutane, but also contributed to the effective utilization of butanediol, which is inevitably produced as by-product in the process of coal to ethylene glycol, suggesting a promising application in the clean manufacture of epoxybutane with inexpensive cost.

Propylene Oxide Polymerization in the Presence of Layered Double Hydroxides

Propylene oxide polymerization in the presence of layered double hydroxides with different concentration of basic sites on their surface has been studied. It is shown that the polymerization can be catalyzed by both basic and acidic sites. On the basis of kinetic experiments the mechanisms of reaction undergoing were proposed.

Heterostructural design of I-deficient BiOI for photocatalytic decoloration and catalytic CO2 conversion

I⁻ vacancies in BiOI play a major role in governing the photocatalysis and catalysis.

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.