Preparation of Fly Ash-based Y-type Molecular Sieves and Their Performance for CO2 Hydrogenation
Y-type molecular sieves were prepared from fly ash and their CO2 hydrogenation activity was investigated.Chemical roasting method was adopted to activate fly ash,and Na2CO3 was used as the chemical activator to investigate the effects of roasting temperature,roasting time,and the mass ratio of fly ash to sodium carbonate on the activation of fly ash,and the experimental results showed that under the conditions of roasting temperature of 800 ℃,roasting time of 2 h,and the mass ratio of fly ash to Na2CO3 of 1.0∶0.8,the products of the roasting of fly ash were dominated by chalcopyrite.The Y-type molecular sieves were prepared by hydrothermal synthesis method using the washed products as raw materials,and the effects of HCl/SiO2 ratio,crystal seed addition,H2O/SiO2 ratio,hydrothermal temperature,and hydrothermal time on the crystallinity of the molecular sieves were investigated,and the Y-type molecular sieves prepared at the conditions of HCl/SiO2=2.7,crystal seed addition of 6％,H2O/SiO2=80,hydrothermal temperature of 100 ℃,and hydrothermal time of 12 h were found to have the highest crystallinity.The prepared Y-type molecular sieves were subjected to CO2 hydrogenation experiments,and the experimental results showed that the CO2 conversion rate reached 60％and the CH4 selectivity reached 44.9％under the conditions of reaction temperature of 600 ℃ and reaction pressure of 4.0 MPa.
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