A Study On Controllable Synthesis Of Novel Layered Zeolitic Precursors And Derivative For Catalysis And Gas Separation

Zeolites are a class of important microporous materials,have been widely used in petroleum refining,fine chemical industry and environmental protection.However,the presence of sole micropores inevitably hinders the practical application of conventional zeolites in processing bulky molecules due to severe mass transfer constrains.Therefore,synthesizing the oriented zeolite nanosheets or macroporous zeolites could break the mass transfer constrains and enhance the accessibility of active sites,improving the catalytic performance.In addition,zeolites with well-defined pore structure and excellent hydrothermal stability have been widely used in selective membrane separation and adsorption.However,in order to reduce the non-selective defects,the thickness of microporous membrane is mostly in micrometer scale,inevitably decreasing the gas permeance.Therefore,zeolite nanosheets have been considered as ultimate building blocks for preparing highly effective separation membranes benefiting from the short diffusion path,and precisely sized pores or interlayer galleries.In this thesis,by using the well-designed organic structure-directing agent（OSDA）,a novel 12-member ring aluminosilicate zeolite and a series of swollen layered zeolites with different frameworks have been hydrothermally synthesized.Based on the special swollen layered zeolite,a mild exfoliated strategy was developed to prepare high-aspect-ratio nanosheets.The nanosheet and hierarchically structured zeolites investigated systematically to explore possible applications as catalytic and gas separation materials.This thesis is mainly composed of following four parts.（1）Direct synthesis and exfoliation of swollen layered ferrierite for the reductive etherification of furfural.The ferrierite layered precursor with a swollen structure（denoted as ECNU-35P）was directly synthesized with a commercially available surfactant of decamethonium hydroxide as bifunctional organic structure-directing agent（OSDA）.ECNU-35P,with elastic long-chain surfactant intercalating the neighboring FER layers,had a much wider interlayer spacing（1.2 nm）than previously reported FER-type layered precursors of PLS-3（0.53 nm）and PREFER（0.66 nm）.The phase delamination of ECNU-35P was readily realized without additional swelling process in basic media that is destructive to zeolite frameworks.The non-corrosive delaminated derivative（DECNU-35）was composed of the FER nanosheets with 4 nm–thickness.With large external surface area(232 m² g^-1),abundant mesopores(0.67 cm³ g^-1)and moderate acidity,Pd/DECNU-35 served as highly active and robust catalysts in the reductive etherification of biomass furfural in ethanol,providing a high yield of 74%for the biofuel of furfuryl ethyl ether.（2）Swollen layered zeolite for assembly of two-dimensional separation membranes for hydrogen purification.Membrane separation is energy-saving and environmentally friendly method.Two-dimensional（2D）molecular-sieving membranes,featuring unique nanopores and less transport resistance,are potential to achieve highly permeable and selective mixture separation at low energy consumption.Herein,a novel swollen layered zeolite ECNU-28 with SZR topology is hydrothermal synthesized,which possesses eight-member ring（8-MR,3.0×4.8?）pores normal to the nanosheets.It is easily exfoliated to construct 2D membrane,which shows a high hydrogen selectivity up to 130 from natural gas（methane）and a high H₂ permeance of 4.26×10^-7 mol?m^-2?S^-1·Pa^-1,promising for hydrogen purification and greenhouse gas capture.（3）Mechanism for synthesizing the swollen layered zeolites.Theoretical calculation predicts the effects of OSDAs with different spatial configurations in the process of zeolite crystallization.Well-designed OSDAs have similar physicochemical characteristics with surfactants,which can self-assemble into layered micelle.The head groups direct the crystallization of the layer framework,and the long chain groups support the adjacent layer,forming the special swollen structure.By using well-designed OSDAs,a series of swollen layered zeolites(ECNU-28,ECNU-35,ECNU-39,Swollen FER-DC₈,Swollen FER-SC₈ and Swollen FER-SC₁₀)with different layer spacing have been hydrothermal synthesized,proving the strategy has a certain universality.（4）Design synthesis of a novel aluminosilicate zeolite ECNU-30 with intersecting12×10 MR pores.A novel large-pore aluminosilicate ECNU-30 innovated by the FER-type interlayer-expanded zeolite（IEZ）is hydrothermal synthesized by using a well-designed OSDA.The pyrrolidine-containing Bola-form template with an appropriate steric configuration for both filling the expanded pore structure and directing the crystallization of fer pentasil layers is predicted by theoretical calculations and further used in the hydrothermal synthesis of ECNU-30.The calcined ECNU-30 is analogous to the FER-type interlayer-expanded zeolite,exhibiting 12-MR and 10-MR pores along the[001]and[010]directions,respectively.As a solid-acid catalyst,ECNU-30nanosheets display excellent performance in the Friedel-Crafts acylation and benzene alkylation reactions.The yield of ethylbenzene and isopropylbenzene over ECNU-30are 29%and 19%,respectively,exceeding that of conventional industrial catalyst,benefiting from its open-pore structure（2D 12×10 MR）and large external surface area(232 m² g^-1).