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 Basic Properties of Na and Na2O Containing FAU Zeolites
Tác giả hoặc Nhóm tác giả: Ho Viet Thang, Miroslav Položij, Mar Llorca Torres, Petr Nachtigall
Nơi đăng: 46th Symposium on Catalysis, November 3-5, 2014 , Prague, Czech Republic; Số: 46;Từ->đến trang: 10;Năm: 2014
Lĩnh vực: Khoa học; Loại: Báo cáo; Thể loại: Quốc tế
TÓM TẮT
FAU zeolite is one of the most important zeolites used in ion exchange and catalysis. FAU is studied in this work as a potential catalyst of an aldol condensation, which is one of the key reaction for transform action of lignocellulosis into bio fuels. Aldol condensation can be catalysed by both acidic and basic species and acidic H-FAU was recently shown to be an active catalyst of the reaction1. Basic form of FAU zeolite has also shown interesting activity; however, the highest activity has been obtained with FAU containing sodium oxide clusters. The activity in basic catalysed reactions could be used as an objective probe to evaluate for basic properties of the materials. In this work the basicity has been studied theoretically by modelling the reaction mechanism of acetone and furfural condensation over Na-FAU and over-exchanged Na-FAU. The differences between basic properties of regular 3D zeolite and corresponding hierarchical FAU have been studied as well. Periodic model with the DFT-D3 method has been used to study the interaction of reactants with the zeolite and the cluster model with PBE exchange-correlation functional has been used for the reaction mechanism investigation. The reaction mechanism has been found to be ruled by the relative energies of deprotonated (enolate) and enol form of acetone in different materials. In the Na-FAU zeolite the reaction proceeds by a Lewis acid mechanism via the enol intermediate. In the Na2O-FAU zeolite the reaction proceeds via the deprotonated form of acetone by a typically basic catalysed mechanism. The hierarchical FAU zeolite was found to have lower basicity compared to normal 3D zeolite.
ABSTRACT
FAU zeolite is one of the most important zeolites used in ion exchange and catalysis. FAU is studied in this work as a potential catalyst of an aldol condensation, which is one of the key reaction for transform action of lignocellulosis into bio fuels. Aldol condensation can be catalysed by both acidic and basic species and acidic H-FAU was recently shown to be an active catalyst of the reaction1. Basic form of FAU zeolite has also shown interesting activity; however, the highest activity has been obtained with FAU containing sodium oxide clusters. The activity in basic catalysed reactions could be used as an objective probe to evaluate for basic properties of the materials. In this work the basicity has been studied theoretically by modelling the reaction mechanism of acetone and furfural condensation over Na-FAU and over-exchanged Na-FAU. The differences between basic properties of regular 3D zeolite and corresponding hierarchical FAU have been studied as well. Periodic model with the DFT-D3 method has been used to study the interaction of reactants with the zeolite and the cluster model with PBE exchange-correlation functional has been used for the reaction mechanism investigation. The reaction mechanism has been found to be ruled by the relative energies of deprotonated (enolate) and enol form of acetone in different materials. In the Na-FAU zeolite the reaction proceeds by a Lewis acid mechanism via the enol intermediate. In the Na2O-FAU zeolite the reaction proceeds via the deprotonated form of acetone by a typically basic catalysed mechanism. The hierarchical FAU zeolite was found to have lower basicity compared to normal 3D zeolite.
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