Studies On Preparation And Benzoylation Activity Of Zirconium-Modified Porous Magadiite Heterostructure

Silicic magadiite is a good candidate for clay-derived heterostructures due to excellent cation exchangeable capacity, resistance to acid and hydrothermal stability. However, pure clay-derived heterostructures materials have a neutral SiO2 framework limiting their applications to selective adsorption, separation and acid catalysis. In the present work, the modifications of surface acidity were performed by incorporation of zirconium into the silica framework and by incorporation of sulfated zirconia upon exfoliation of the layered magadiite. Moreover, benzoylation performance of anisole upon catalysts is thoroughly investigated and the co-relation between structure and activity is deeply studied. The main results and highlights of the thesis are as follows:(1) Novel zirconium-doped porous magadiite heterostructures Si/Zr-xMag (x=Si/Zr molar ratio, x=80,40,20,10 and 5) are fabricated by two-dimensional intragallery cosurfactant-directing in situ hydrolysis-condensation-polymerization method of TEOS and Zr(OPr")4 from synthetic Na-magadiite. The HRTEM and 29Si MAS NMR results indicate that the obtained Si/Zr-xMag materials possess high surface area (603.3 m2/g) and high thermal stability (600℃) upon effective assembly of interlayer Zr-doped meso-structural silica and the layers of magadiite. The Si/Zr-xMag samples (x=80,40,20 and 10) show successful incorporation of Zr into the lattice of interlayer mesostructural silica framework leading to considerably generated Br(?)nsted sites Zr-O(H)-Si and obviously increased Lewis sites Zr-O-Si along with well-kept layered supermicro-mesostructure, while Si/Zr-5Mag shows delaminated layers.(2) The catalytic performance of Si/Zr-xMag in liquid-phase benzoylation of anisole (140℃) was studied. Si/Zr-lOMag exhibits the highest benzoylation activity and yield for para-methoxybenzophenone (94.1%) due to the strongest synergy between the high concentration of surface Br(?)nsted sites and supermicro-mesostructure. Si/Zr-10Mag can be reused by no further chemical treatment for at least five runs with a slightly reduced p-MBP yield (7.6%) implying a highly stable and efficient acid catalytic performance of Si/Zr-xMag heterostructures by an in situ 2D gallery-template methodology.(3) Novel delaminated porous sulfated zirconia-magadiite heterostructures xSZ-Mag (x=ZrO2/CTA-Mag mass ratio, x=0.5,1,2 and 4) were prepared following a sol-gel approach involving the hydrolysis-polycondensation of Zr(OPrn)4 in the presence of organoclays (CTA-Mag) and were modified by treatment with dilute sulfuric acid. It was found that ZrO2 nanoparticles are highly dispersed on the exfoliated magadiite layers of 0.5SZ-Mag. The 1SZ-Mag showed the lowest crystal size of tetragonal zirconia of 6.7 nm that increases to 9.2 nm for 4SZ-Mag. Noted that the surface acidity is increased with the amount of ZrO2 (x=0.5,1 and 2) and the 2SZ-Mag holds the most acidity (0.645 mmol/g).(4) The catalytic performance of xSZ-Mag in liquid-phase benzoylation of anisole at low temperature (80℃) was studied. 1SZ-Mag exhibits the highest activity and yield for para-methoxybenzophenone (84.2%) due to the homogeneously dispersed sulfated ZrO2 nanoparticles and the relatively high concentration of surface Br(?)nsted sites.