Preparation Of SBA-15 Supported Catalysts And Direct Catalytic Synthesis Of Dimethyl Carbonate From CO 2 And CH 3

Dimethyl carbonate(DMC) is a kind of excellent chemical products, which has been widely applied in our life. Carbon dioxide has serious harm on the human survival environment. Consequently, a large number of scientific research workers pay attention to exploring the carbon dioxide recycle technology. It is a synthetic route of great application prospect to synthesize directly DMC from CO2and CH3OH. The route not only can produce high value-added chemicals, but also employ effectively carbon dioxide. Therefore, the catalysts in direct synthesis of dimethyl carbonate carried on in-depth study.First of all, The Cu-Ni/SBA-15catalysts were prepared by incipient wetness impregnation. And the samples were characterized by nitrogen physisorption, X-ray diffraction (XRD), H2temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM). It is significant to explore the influence of different Cu-Ni loadings on the specific surface area, pore volume and the dispersion of active components. The prepared catalysts were applied to direct synthesis of DMC from CO2and CH3OH. We obtain the best technological conditions by optimizing reaction temperature, reaction pressure, mass of methanol and other conditions.The reasults indicate physical and chemical properties of the catalysts with different Cu-Ni loadings have a big difference. With the increase of Cu-Ni loading, the dispersion of active components will be severely affected. When Cu-Ni loading amount was20%, the results of TEM investigations indicated that active components of the catalysts will produce agglomeration, which can result in decreasing catalytic activity. When the metal loading amount was15%, CH3OH conversion is the highest.Through XRD, TEM characterizations of15%Cu-Ni/SBA-15catalyst, we analyze their structural changes before and after reaction. The mesoporous structure of the catalyst was damaged after reaction.In addition, we explore the impact on the structure properties and catalytic activity of Cu-Ni/SBA-15after doping Ceo.5Zro.5O2. XRD spectrum showed the intensity of Cu-Ni typical diffraction peaks decreased significantly after loading Ceo.5Zro.5O2. It can indicate that Ceo.5Zro.5O2is in favor of the dispersion of supported Cu-Ni metal particles.The activity of two catalysts was evaluated. The results show that the catalytic activity of Cu-Ni/SBA-15enhanced significantly after adding Ceo.5Zro.5O2. At this moment, the methanol conversion rate reached6.63%, the DMC selectivity yield was87.6%. The results show that Ceo.5Zro.5O2can increase the dispersion of Cu-Ni metal particles to promote the synthesis of DMC. And we speculated reaction mechanisms in the presence of Cu-Ni/Ce0.5Zr0.5O2/SBA-15to understand deeply direct synthesis DMC from CO2and CH3OH.Last but not the least, SBA-15was treated with ethylene glycol (EG) before the impregnation of metal precursors. And Cu-Ni/Ce0.5Zr0.5CVSBA-15-EG was prepared by two sequential steps. We study the influence on the structure properties and catalytic effects of the catalyst. The results of TEM investigations show that Cu-Ni metal particles dispersed evenly in the channel of SBA-15. And we prepared nano-sized Cu-Ni metal particles.The catalytic activity of diffferent catalysts was evaluated. Compared with Cu-Ni/Ceo.5Zro.502/SBA-15, the methanol conversion rate reached7.76%for the catalyst of the pretreated SBA-15by EG. The results show that Cu-Ni metal particles possess better dispersibility and smaller size. Consequently, its catalytic effect enhance significantly.