Study On The Preparation And Catalytic Properties Of Novel Ni-based Catalysts Towards Steam-CO₂ Dual Reforming Of Methane

Steam-CO2 dual reforming of methane (SCRM) reaction utilizes two main greenhouse gas CH4 and CO2 to produce syngas, which is in favor of relieving the global warming in the environgment aspect. What’s more, clean synthesized fuel can be poduced in large scale by combining SCRM with Ficher-Tropsch synthesis, which might alleviate the global energy crisis.The catalysts towards methane refoming reaction consist of noble and non-noble transition metals catalysts. Generally, noble metals have been found to exhibit highly activity and stability towards methane reforming reaction. However, the main drawbacks that restrict large scale application of noble metals catalysts are limited resources and high costs. In this aspect, nickel based catalysts are technically and economically viable for the reforming reaction. Generally, Ni-based catalysts which are cheap and abundant, but with comparable catalytic activity to noble metals have been employed as promising catalysts for reforming of methane. However, carbon deposition and sintering of Ni are the fatal drawbacks of the Ni-based catalysts for reforming of methane. New strategies should be studied to improve the catalytic activity and stablitity for Ni-based catalysts towards methane reforming reaction, which is of great importance in alleviating the global energy crisis and energy diversification.In this thesis, the effect of the preparation temperature of silica-alumina composite oxides derived from natural halloysite (SA-H) support, the effect of mineralizer of ZrO2 support, and the effect of preparation method of the Mo2C modified Ni/ZrO2 catalysts on catalytic perfomance of supported Ni catalysts for steam-CO2 dual reforming of methane were studied. Various characterizations including CO-Chemisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), N2 adsorption-desorption (BET), and thermogravimetric analysis (TGA) were conducted to reveal the relationship between catalysts nature and catalytic performance. The obtained results are listed as follows:1. The effect of calcination temperature of silica-alumina composite oxides (SA-H) supports derived from natural halloysite on catalytic performance of supported Ni catalysts towards steam-CO2 dual reforming of methane (SCRM) were investigated. The supported Ni catalyst on the halloysite derived silica-alumina nanorod (Ni/SANR-H) prepared by calcination at 1000℃ exhibited higher catalytic activity ascribing to higher Ni dispersity. The robust Ni/SANR-H catalyst exhibited unexpectedly catalytic stability for SCRM reaction with much higher coke and Ni-sintering resistance attributing to the enhanced interaction between Ni and support.2. The effect of the type and amount of mineralizer of ZrO2 supports on the morphology and texture of supports and catalytic performance of Ni/ZrO2 catalysts for SCRM reaction was studied. Ni/ZrO2(SAc0.5) catalyst with appropriate amount of sodium acetate as mineralizer of ZrO2 support exhibited smaller Ni crystallite size, which resulted in the enhancement of Ni-support interaction. Then high catalytic activity and highly coke and sintering resistant Ni-based catalyst was obtained.3. Novel Mo2C-Ni/ZrO2(Glu) catalyst was synthesized by utilizing glucose as promoter in loading and carbon precursor of Mo2C. Mo2C-Ni/ZrO2(Glu) catalyst exhibits unexpected superior catalytic stability for SCRM reaction with much higher coke and sintering resistance compared with traditional Mo2C-Ni/ZrO2(Glu) catalyst prepared using CH4 as carbon precursor of Mo2C. The novel Mo2C-Ni/ZrO2(Glu) catalyst can be a promising candidate for SCRM reaction.