Synthesis Of MCM-41Molecular Sieve Using Different Silica Source And Study Of Heat Transfer Performance Of MCM-41in A Fixed Bed

In this paper, MCM-41molecular sieve was prepared by hydrothermal synthesis under basic condition, CH3(CH2)i·(CH3)3NBr (CTAB) was selected as template agent, using Na2SiO3·9H2O and Si(OC2Hs)4(TEOS) as silica source. Optimal synthesis conditions for Na2SiO3·9H2O system were:Si/CTAB/H2O=1/0.3/100, pH=10.5, crystallizing time48h, crystallizing temperature120.0℃; Optimal synthesis conditions for TEOS were: Si/CTAB/H2O=1/0.3/100, pH=10.5, crystallizing time48h, crystallizing temperature130.0℃. Al-doped MCM-41was prepared using NaAlO2, demonstrated that the addition of heteroatoms can reduce the crystallinity of molecular sieve. The differences between synthesis processes of two kinds of silicon source were compared, found in such aspects as acid dosage and crystallizing temperature had apparent differences. The samples synthesized by different silica source were characterized by XRD, BET, TG and SEM, the results showed that both silica source can synthesize high crystallinity, high specific surface area molecular MCM-41sieve. However, the particle size of Na2SiO3·9H2O system is more smaller than TEOS system. The thermal stability and hydrothermal stability of MCM-41was tested, the results showed that samples at700.0℃lattice remains intact. When liquid water exist, the hydrothermal stability of MCM-41is poor, when gaseous water exist, the hydrothermal stability of MCM-41is.not so bad. Ni-MCM-41catalyst was prepared by impregnation method, and the catalytic performance for methanation reaction was tested in a fixed bed, the highest CO conversion rate was71.3%, CH4selectivity was79.2%. The radial and axis temperature distribution of fixed bed loaded MCM-41was measured. The two-dimensional pseudo-homogeneous-phase model was used to simulate the heat transfer behavior in the fixed bed. The finite difference method and the Levenberg-Marquardt method were used to solve the model parameters, including radial effective thermal conductivity (ker) and wall heat transfer coefficient (kw). The heat transfer parameters were correlated as a function of Reynolds number(Rep) and Pe number by origin software, the results showed that the heat transfer parameters were presented good linear relationship with Rep and Pe.