Green Production of Glycerol Ketals with a Clay-Based Heterogeneous Acid Catalyst

Abstract

Glycerol remains a bottleneck for the biodiesel industry as well as an opportunity from the biorefinery perspective, having a notable reactivity as a platform chemical. In particular, glycerol ketals can be envisaged as oxygenates for fuel formulation. In this study, we have focused on the green synthesis of glycerol ketals by reacting glycerol with acyclic (acetone, butanone) and cyclic (cyclohexanone) ketones in the presence of an acid activated clay Tunisian AC in homogeneous systems under quasi-solventless conditions. These reactions were followed by on-line Fourier Transform Infrared Spectroscopy (FTIR) (namely, ReactIR 10). Firstly, the contacting time was selected studying the activity, stability and chemical characteristics of a set of catalysts. The 1-h activated clay AC was further characterized by X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electronic Microscopy with Energy Dispersive Spectroscopy (SEM/EDS). Finally, the effect of the main operational variables (catalyst concentration, reagents molar ratio, time and temperature) were checked and we reflected on adequate second-order kinetic models with partial first-order deactivation.

Valorization of natural clay as an ecological catalyst in the regioselective synthesis of some heterocyclic compounds based on 1,2,3-triazoles

“…After 36 hours of reaction, we add 2mL of CH2Cl2 to facilitate the removal of the catalyst by filtration. After evaporation of CH2Cl2 under vacuum, the obtained triazole was analyzed by 1 HNMR to evaluate the formation percentages of (1,4) and (1,5) isomers [16,17] (Scheme 3).…”

“…The coupling of alkynes (1a-4a) with azides (1b-2b) in the presence of catalysts (JS, JES, JSP, JESP, JSP-Cu, and JSEP-Cu) at room temperature without solvents and excitements gave two isomers (1,4) and (1,5)-disubstituted-1,2,3-triazoles (Scheme 3). The yields of isomers (1,4) and (1,5) were evaluated by 1 HNMR conversion; results of 1 HNMR conversion were given in Tables (3 & 4).…”

“…The mineral elements (SiO2, Al2O3, Fe2O3, MgO, CaO, SO3, P2O5, K2O, and Na) that constituents of washed clays (Table 2) do not affect the coupling reaction between terminal alkynes and azides. The outcome was 0% for the two isomers (1,4) and (1,5). The coupling reaction between alkynes (1a-4a) and azides (1b-2b) using adsorbed CuI by purified clays (Cu-pillared clay) was regioselective for 1,4-disubstituted-1,2,3-triazole, the yields of (1,4) isomer were approximately 100% (Table 3, Entries: 6, 7, 13, 27 and 28 & Table 4, Entries: 6, 7, 21, 27 and 28).…”

“…They used synthetic catalysts with copper (II) for coupling phenylacetylene and benzyl azide (yield ≤ 93%). The yields of (1,4) and (1,5) isomers obtained from application catalysts (JS, JES, JSP, and JESP) in the coupling alkynes (1a-4a) and azides (1b-2b) were similar to the reaction realized without catalyst, the maximum yield obtained for the isomer (1,4) was in the order of 93.6% with (JES) catalyst (Table 4, Entry: 10) and it is in the order of 44.4% for (1,5) isomer with (JS) catalyst (Table 3, Entry: 16).…”

“…Dioxolanes are heterocyclic acetal compounds with a cycle containing five atoms; two are oxygen. Several types of research report the synthesis of dioxolanes using activated clays as catalysts [3][4][5][6][7][8]. In contrast, triazoles are heterocyclic compounds with three nitrogen atoms placed in 1,2,3 or 1,2,4 positions of the cycle.…”