Abstract
β-cyclodextrin derivative intercalated MgAl-hydrotalcites (β-CD-Ca/LDH) was synthesized to convert glycerol into high value-added glycerol carbonate(GC) by transesterification of dimethyl carbonate (DMC) and glycerol in this paper. β-cyclodextrin-metal complexes and β-CD-Ca/LDH was characterized by XRD, FT-IR, SEM, XPS and nitrogen adsorption-desorption. The enrichment of organic reactants in the hydrophobic cavity of β-cyclodextrin improved the collision probability of reactants. The intercalation of β-cyclodextrin-calcium complex (β-CD-Ca) increased the pore size and basic strength of catalyst. The experiment results showed that the glycerol conversion was 93.7% and the GC yield was 91.8% catalyzed by β-CD-Ca/LDH when the molar ratio of DMC and glycerol was 3:1, the catalyst dosage was 4 wt.%, the reaction temperature was 75 °C and the reaction time was 100 min while the glycerol conversion was 49.4% and the GC yield was 48.6% catalyzed by MgAl-LDH under the same conditions.
Highlights
Catalyst for Transesterification of Cyclodextrin (CD) usually contains several D-glucopyranose units connected by α-glycosidic bonds as the degradation product of amylose [1,2]
The characteristic peak of β-cyclodextrin-calcium complex (β-CD-Ca) at 550 cm−1 can be ascribed to the stretching vibration of metal-OH(M-OH)
The characteristic peak of β-cyclodextrin can be observed in the spectrum of β-CD-Ca/LDH, which means that β-CD-Ca had been successfully inserted into the interlayer of MgAl hydrotalcites
Summary
Catalyst for Transesterification of Cyclodextrin (CD) usually contains several D-glucopyranose units connected by α-glycosidic bonds as the degradation product of amylose [1,2]. The outer side of truncated conical cyclodextrin is hydrophilic due to the ports with rich hydroxyl while the inner cavity is hydrophobic owing to the shielding effect of carbon chains [3] This special structure enables different organic compounds embedded in the inner cavity of cyclodextrin to exist in hydrophilic solvents, which is necessary for the formation of inclusion complexes and molecular assembly systems [4,5,6]. Szabados et al [19] synthesized different hydrotalcites using different metal ions and verified their catalytic activity in the transesterification of glycerol and dimethyl carbonate. Β-cyclodextrin metal complexes (β-CD-M) with alkaline centers were prepared and intercalated into MgAl-LDH in this thesis as heterogeneous catalyst for GC synthesis by transesterification between glycerol and dimethyl carbonate. The catalytic performance and reuse ability of β-CD-Ca/LDH in transesterification was investigated
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