Design Of Hybrid Catalysts Based On Sulfated Zirconia And Their Application For Biodiesel Production

More recently, much research is focused on exploring and investigating environmentally benign as well as commercially visible catalyst systems. As a solid superacid, sulfated zirconia possess potential economic and green benefits for a wide variety of reactions. However, current sulfated zirconia system is not a popular choice for commercial applications because of the poor porosity of sulfated zirconia, the strong adsorption of hydrophilic molecular and significant deactivation during the process of liquid-solid phase reactions. Therefore, a series of mesoporous sulfated zirconia based hybrid catalysts functionalized by alkyl-bridged organosilica moieties with tunable different structural orderings and pore geometries were fabricated. Their acid catalytic performances towards biodiesel production from pure triglyceride as well as low-cost virgin plant oil were investigated.1. A series of mesoporous sulfated zirconia materials functionalized by alkyl-bridged organosilica moieties, SO₄^2-/ZrO₂-SiO₂（Et） with various S/Si or Zr/Si molar ratios, were developed by one-step co-condensation technique combined with hydrothermal treatment with the aid of triblock copolymer surfactant. The structure, morphology, porosity, and acid properties of the materials were well characterized by spectroscopy methods, solid-state NMR measurements, X-ray diffraction analysis, transmission electron microscopy, and nitrogen physisorption measurement. Additionally, acid-base titration and the Hammett methods combined with spectroscopy technique were employed to evaluate the acid property of the hybrid catalysts. The hydrophobicity of sulfated zirconia can be controlled with the assistant of ethane bissilylated organosilicate agent. The catalytic performance of the resulting multifunctionalized organic-inorganic hybrid materials was evaluated by the transesterification of tripalmitin with methanol for biodiesel production in the presence of 20 wt% myristic acid under the mild conditions; and the influences of the factors including functional component loadings and molar ratios of oil to methanol on the yields of fatty acid monoalkyl esters were studied. Additionally, the excellent catalytic activity was discussed in detail. Finally, deactivation and significant loss of activity for the catalyst were not observed through three consecutive transesterification cycles.2. A series of mesostructured SO₄^2-/ZrO₂–SiO₂（R） materials were developed by using one-step co-condensation technique in the presence of triblock copolymer surfactant （P123）. By tuning the starting precursors （alkyl bissilylated organosilicate agents and metal oxide matrix）, the materials exhibited ordered two-dimensional （2D） hexagonal p6mm (SO₄^2-/ZrO₂–SiO₂（Ph）) and three-dimensional （3D） interconnected (SO₄^2-/MwOv–SiO₂（Et） （MwOv = ZrO₂/Ta2O5/Nb2O5/TiO₂）, and SO₄^2-/ZrO₂-SiO₂ pore geometries, respectively. The structure, morphology, porosity, and compositional properties of the materials were well characterized by FT-IR, XPS, TEM, and nitrogen physisorption measurement. It is concluded that the acidic sites are owing to the Zr-O-S bond deriving from the surface hydroxyl group of ZrO₂ linked with sulphate group; meanwhile, the alkyl-bridged organosilica moieties are present as bridging components directly incorporated into the ZrO₂ framework through Zr-O-Si-Et-Si-O linkages. Based on the above proposal, the Br-nsted acid strength and structural stability of the hybrid material can be significantly increased. The catalytic performance of the resulting multifunctionalized organic-inorganic hybrid materials was evaluated by the transesterification of Eruca sativa Gars. oil with methanol for biodiesel production under the mild conditions. Combining the compositional and structural results with catalytic data, the catalytic mechanism as well as the influences of the factors on the yields of fatty acid monoalkyl esters is studied. Special attention was paid to investigate deactivation and significant loss of activity for the catalyst through three consecutive transesterification cycles.3. A series of mesostructured SO₄^2-/ZrO₂–SiO₂（R） materials with two-dimensional hexagonal p6mm, three-dimensional cubic Im3m, and three-dimensional interconnected pore geometries were obtained selectively by turning preparation conditions （like type of alkyl bissilylated organosilicate agents, type of triblock copolymer surfactant and using co-solvent） through a single step nonionic-surfactant-templating strategy combined with hydrothermal treatment technique. The mesostructure, morphology, porosity and acid property of the hybrid materials were well-characterized. The catalytic performance of the resulting multifunctionalized organic-inorganic hybrid materials was evaluated by the transesterification of the transesterification of Eruca sativa Gars. oil with methanol for biodiesel production under the mild conditions; and the influences of the factors including the structural orderings, pore geometries, and the functional component loadings on the yields of fatty acid monoalkyl esters were studied. The synergy effect between the structural ordering, pore geometries, porosity, acidity, and the hydrophobic character could make the hybrid materials exhibiting the excellent catalytic performances. Remarkably high catalytic activity and stability were observed.