Preparation Of Ni-Based ZrO₂-SiO₂ Mixed Oxides Aerogel Catalyst And Performance In Maletic Anhydride Selective Hydrogenation

Aerogels are extremely porous, low-density materials, and they have higher chemical stability. Now, aerogels are intituled "the new catalyst materials which own most developing potential in 21st century". ZrO₂-SiO₂ mixed oxides have some special characters, so more and more researchers are paying attention to them. In this dissertation, using zirconyl nitrate as starting material, ZrO₂-SiO₂ mixed oxides aerogel was prepared by Sol-gel method coupling supercritical drying. Ni/ZrO₂-SiO₂ catalyst was prepared by impregnating ZrO₂-SiO₂ mixed oxides aerogel with Ni(NO₃)₂.6H₂O. In a 100ml high-pressure autoclave, the catalyst activity in hydrogenation of MA was investigated. The primary work and results of the dissertation are summarized below:1. Using TEOS and zirconyl nitate as starting material, ZrO₂-SiO₂ mixed oxides aerogel was prepared by Sol-gel method and SCFD method. And the characterization of ZrO₂-SiO₂ mixed oxides aerogels was investigated. The results showed that the ZrO₂-SiO₂ mixed oxides aerogel had higher surfaceareas;The dispersion of ZrO2 in ZrO2-SiO2 mixed oxides aerogel is high and there is Zr-O-Si linkage in ZrO2-SiO2 mixed oxides aerogels.2. Ni/ZrO2-SiO2 catalyst was prepared by impregnating ZrO2-SiO2 mixed oxides aerogel with Ni(NO3)2-6H2O. The catalytic activity of Ni/ZrO2-SiO2 on MA hydrogenation was investigated and the results showed that the selectivity to GBL was much higher on Ni/Zr-SiO2 than that on Ni-Zr/SiO2 and Ni/SiO2 catalysts.3. The properties of Ni/ZrO2-SiO2 catalyst were characterized by TEM, TPR and XRD and the results showed that the adding of ZrC>2 improved the dispersion of NiO on support and also enhanced the interaction strength between NiO and support.4. Effects of after-treatment on Ni/ZrC>2-SiO2 was investigated and the process condition was optimized and the results showed that with the calcination temperature (the temperature varied from 400 °C to 600 °C) increasing, the selectivity to y-butyrolactone on the Ni/ZrO2-SiO2 catalyst increased;while with the reduction temperature (the temperature varied from 400 °C to 580°C) increasing, the selectivity to y-butyrolactone decreased;Increasing reaction temperature, prolonging reaction time or enhancing reaction pressure all can improve the selectivity to y-butyrolactone. Under optimized conditions, the selectivity to y-butyrolactone can reach 87.8% on the Ni/ZrO2-SiO2 catalyst when the nickel content is 40%, and the optimized reaction condition is 180°C, 6.0MPa, 8h.