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Synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by talc and other phyllosilicates.

ABSTRACT: Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO₂ with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10-35 bars and temperatures of 100-150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbonates, in the presence or absence of a solvent. The selectivity of the catalytic system could be improved with heat pre-treatment of the phyllosilicates albeit this resulted in slightly lower epoxide conversion. The results obtained using the heat treated phyllosilicates strongly support the hydrogen bond assisted mechanism for the cycloaddition of epoxides and CO₂. The cycloaddition reaction could also be carried out in the absence of TBAB, although lower cyclic carbonate yields were observed. The phyllosilicate part of the catalyst system is heterogeneous, easy to separate after completion of reactions and reusable a number of runs without loss of activity.

SUBMITTER: Nakibuule F

PROVIDER: S-EPMC7576757 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by talc and other phyllosilicates.

Nakibuule Fiona F Nyanzi Steven Allan SA Oshchapovsky Igor I Wendt Ola F OF Tebandeke Emmanuel E

BMC chemistry 20201020 1

Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO<sub>2</sub> with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10-35 bars and temperatures of 100-150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbo ...[more]

PMID: 33094290

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Project description:Functionalized aluminosilicate materials were studied as catalysts for the conversion of different cyclic carbonates to the corresponding epoxides by the addition of CO2. Aluminum was incorporated in the mesostructured SBA-15 silica network. Thereafter, functionalization with imidazolium chloride or magnesium oxide was performed on the Al_SBA-15 supports. The isomorphic substitution of Si with Al and the resulting acidity of the supports were investigated via 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and NH3 adsorption microcalorimetry. The Al content and the amount of MgO were quantified via inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. The anchoring of the imidazolium salt was assessed by 29Si and 13C MAS NMR spectroscopy and quantified by combustion chemical analysis. Textural and structural properties of supports and catalysts were studied by N2 physisorption and X-ray diffraction (XRD). The functionalized systems were then tested as catalysts for the conversion of CO2 and epoxides to cyclic carbonates in a batch reactor at 100 or 125 °C, with an initial CO2 pressure (at room temperature) of 25 bar. Whereas the activity of the MgO/xAl_SBA-15 systems was moderate for the conversion of glycidol to the corresponding cyclic carbonate, the Al_SBA-15-supported imidazolium chloride catalysts gave excellent results over different epoxides (conversion of glycidol, epichlorohydrin, and styrene oxide up to 89%, 78%, and 18%, respectively). Reusability tests were also performed. Even when some deactivation from one run to the other was observed, a comparison with the literature showed the Al-containing imidazolium systems to be promising catalysts. The fully heterogeneous nature of the present catalysts, where the inorganic support on which the imidazolium species are immobilized also contains the Lewis acid sites, gives them a further advantage with respect to most of the catalytic systems reported in the literature so far.

Dataset Information

Synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by talc and other phyllosilicates.

Publications

Synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by talc and other phyllosilicates.

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