Zr-doped Magadiite Porous Clay Heterostructures Catalysts:Synthesis And Catalytic Property

The aromatic kentones was used mainly as a valuable perfumery intermediate as well as a precursor for antioxidants commonly employed in medicine, pesticides, plastics, liquid crystal, resin, and rubber. The Friedel-Crafts acylation reaction is of great importance in fine chemical industry to produce functionalized aromatic kentones. However, it is noted that various Lewis acids or Bronsted acids were often used in stoichiometric or excess amounts to obtain satisfactory reaction rates and yields in homogeneous catalysis system. Thus large quantities of metal salt waste formed, and the generation of industrialization process unavoidably result in serious reactor corrosion and environmental pollution. Therefore, developing the recycling easily, environmental friendly, reusable heterocatalyst is highly desired in the synthesis of aromatic ketones. In this thesis, we prepared a series of Zr-doped porous magadiite heterostructures (PMH-xZr) catalysts and their WO3modified catalysts by using co-surfactant two-dimensional interlayer in-situ hydrolysis polycondensation method upon magadiite material. The obtained catalysts have been systematically studied by combinational characterization techniques and evaluated in the benzoylation of anisole with benzoyl chloride. The thesis focuses on:(1) Novel Zr-doped porous magadiite heterostructure (PMH-xZr, x=Zr/Si molar ratio2) are prepared using2-D intragallery cosurfactant (CTMABr and n-octylamine) directing hydrolysis and condensation polymerization of inorganic precursors (TEOS and Zr n-propoxide) upon a synthetic magadiite layered material. The obtained PMH-xZr materials possess high specific surface area (400-568m2/g), high thermal stability, and supermicroporous (0.92nm) to mesopores (1.97nm) distribution ascribed to the existence of interlayer Zr-doped silica molecular sieve-like clusters. The PMH-xZr catalysts show greatly enhanced Lewis and newly generated Bronsted (Zr-OH-Si) acidity compared to pure PMH and the PMH-0.1Zr exhibits the maximum acidity.(2) Most PMH-xZr materials except PMH-0.0125Zr show obviously higher selectivity to the main product4-methoxybenzophenone (4-MBP) than conventional homogeneous AlCl3catalyst with identical conversion in benzoylation of anisole with benzoyl chloride. Specially, PMH-0.1Zr presents the highest benzoylation activity (100%benzoyl chloride conv.,91%4-MBP sel.) at140℃owing to its highest Lewis and total acidity, and can be reused by no further chemical treatment for at least six runs with retained conversion and slightly increased selectivity probably due to the formation of Si—O—Zr...Cl species on the the catalyst.We tentatively illustrate the essential structure of the surface acid sites and the structure-activity relation for the PMH-xZr catalysts.(3) WO3-modified PMH-xZr catalysts (xWO3-PMH-0.1Zr) was prepared by impregnation step with ammonium metatungstate as W source on selected PMH-0.1Zr. The interactions between tungsten species and PMH-0.1Zr strongly related to the activation temperature and WO3loadings. With enhancing activation temperature (400-800℃) and WO3loadings (5-25wt.%), the BET surface areas of the catalysts were gradually reduced but still retain high values (140-220m2/g) and supermicropores (0.60-1.27nm) to mesopores (2.14nm) distribution. Importantly, xWO3-PMH-xZr materials have a clearly enhanced acidity mainly from L sites despite of obviously reduced B sites.15wt%-PMH-0.1Zr exhibits the highest acidity probably associated with the formation of (WO)x/ZrO2nanoparticles (XRD and Raman data) resulting from its higher activation temperature and higher WO3loading.(4) The xWO3-PMH-0.1Zr catalysts have obviously higher catalytic activity in benzoylation of anisole than PMH-0.1Zr. With increasing WO3loading, the conversation is increased to98.5%and the selectivity of4-MBP to94%for15wt%WO3-PMH-xZr, in line with its highest total acidity. With further increasing WO3loading to25wt%, the activity is contrarily reduced probably due to the serious agglomeration of (WO)x/ZrO2particles on the catalyst surface and thus obvious decrease in exposure of acid sites.(5) Based on the structure analyses and the reaction evaluation results, we tentatively illustrate the essential structure of the surface acid sites and the structure-activity relation for the PMH-xZr catalysts.