Synthesis, characterization, and application of zirconia and sulfated zirconia derived from single source precursors.

摘要

Scope and method of study. The objective of this research was the development of new methods for the synthesis of zirconium oxide and sulfated zirconium oxide based on the preparation and utilization of novel single-source precursors based on zirconium carboxylate and zirconium sulfonate complexes. A variety of carboxylate and sulfonate compounds were treated with zirconium salts to yield new precursors. The oxide products obtained form the thermal pyrolysis of the precursors were analyzed and characterized using several techniques such as powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Additionally, supported sulfated zirconia was successfully obtained by dispersion of the oxide over a high surface area porous silica support known as MCM-41. The ability of the produced sulfated zirconias to catalyze two different industrial reactions was addressed. The first was the alkylation reaction of benzene utilizing ethers such as dibenzyl ether, n-butyl ether, and benzyl methyl ether as alkylating agents. The second reaction was the self aldol condensation reaction of several ketones such as acetone, methyl isopropyl ketone, cyclopentanone and acetophenone.; Findings and conclusions. Oxides obtained from different zirconium carboxylate and sulfonate precursors showed distinctive properties such as surface morphology, surface area, phase composition and crystallite size. This reflected the strong dependency of the final oxide's properties on the precursor complexes. The supported samples were successfully synthesized with high dispersion of the sulfated zirconia on the surface of the MCM-41 while maintaining high surface area and without causing a serious blockage or damage of the support pore structure. The supported samples assisted in the improvement of the thermal stability of the tetragonal phase and the sulfate groups on the surface. Acidic catalysts prepared by these methods showed a higher acid strength than concentrated sulfuric acid. The sulfated zirconias showed a remarkable catalytic activity and selectivity towards the alkylation of aromatics and self ketone aldol condensation reactions.