Glycerol Carbonate Synthesis by Hierarchically Structured Catalysts: Catalytic Activity and Characterization

Abstract

The surge in biodiesel production in recent years has resulted in enhanced research interest in the conversion of glycerol to other valuable chemicals such as glycerol carbonate (GLC). In the present study, the catalytic transesterification of glycerol with dimethyl carbonate (DMC) for the production of GLC was studied with calcium–lanthanum mixed-oxide catalysts at different Ca/La molar ratios. These catalysts were synthesized using an exo- and endotemplating method. The physicochemical characteristics of the catalysts were determined using powder X-ray diffraction (XRD), N2 sorption, scanning electron microscopy (SEM), and temperature-programmed desorption (TPD) of CO2 and NH3. The transesterification of glycerol was found to be highly dependent on the basicity of the catalysts. The catalyst with a Ca/La molar ratio of 3 (3CaLa) showed the highest glycerol conversion and GLC yield. Optimization of the reaction parameters and reusability of the catalyst were studied with the 3CaLa catalyst in terms of glycerol conversion, GLC yield, and turnover frequency (TOF). At the optimum operating conditions, namely, a reaction time of 90 min, a DMC/glycerol molar ratio of 5, a catalyst mass of 0.217 g, and a temperature of 90 °C, the glycerol conversion and GLC yield were found to be 94% and 74%, respectively, with a reaction rate of ∼0.14 mol L–1 h–1 (with respect to glycerol).

Hydrotalcites Promoted by NaAlO2 as Strongly Basic Catalysts with Record Activity in Glycerol Carbonate Synthesis

“…As reported recently, pure NaAlO 2 showed much higher activity, almost reaching equilibrium (≈93 %) after 20 min with 58 % conversion reached after only 5 min of reaction. In the transesterification of DMC with glycerol, the main function of the solid catalyst is to support the abstraction of H + from glycerol on the basic sites so as to form the glycerol anion . The higher the catalyst basicity, the more negative the charge of the glyceroxide anion (C 3 H 7 O 3 − ), and consequently, the lower the activation energy of the reaction.…”

“…The higher the catalyst basicity, the more negative the charge of the glyceroxide anion (C 3 H 7 O 3 − ), and consequently, the lower the activation energy of the reaction. Hence, the concentration of surface basic sites and strength is known to play an important role in this catalytic reaction …”

“…Similarly, the catalytic reaction of glycerol with alkyl carbonates is a pertinent approach for glycerol carbonate synthesis. In particular, dimethyl carbonate (DMC) is a nontoxic, biodegradable reactant that can be produced through relatively green routes, and its transesterification with glycerol is thermodynamically favored …”

Carbonylation of glycerol with urea to glycerol carbonate over supported Zn catalysts

“…Use of EC leads to formation of ethylene glycol that involves tedious work-up procedure. Although DMC was exploited for transesterification with glycerol using basic catalysts like K 2 CO 3 , CaO and Ca/La mixed oxide but the recyclability of these catalysts was not established [20,21]. Compared to the above-mentioned routes for GC, carbonylation of glycerol with urea proves to be greener, cheaper and atom economic for the synthesis of GC.…”

Experimental and modelling approach to the catalytic coproduction of glycerol carbonate and ethylene glycol as a means to valorise glycerol

“…: + 34 913944164; fax: + 34 913944179. bonates, for they present the advantages of (i) being an indirect manner of CO 2 fixation and (ii) allowing the use of milder operating conditions [8] . Operation with dimethyl carbonate (DMC) at atmospheric pressure from 60 to 75 °C has been described with quantitative yield to product [9][10][11][12][13][14][15][16][17][18] . Likewise, synthesis with diethyl carbonate has been performed with positive results, though the reaction conditions were more severe: large molar excesses of diethyl carbonate to Gly have been used (17:1 to 21:1) and use of temperatures of 130 °C have been described using different types of hydrotalcites as catalysts [19,20] .…”