关键词: 歧化, 丙烯, 2-丁烯, 催化剂

Abstract:

Tungsten substituted mesoporous molecular sieves W-SBA-15 catalysts with different Si/W ratios were directly synthesized under hydrothermal conditions by using Na₂WO₄ as tungsten precursor and tetraethyl orthosilicate(TEOS) as silica precursor.The prepared W-SBA-15 catalysts were characterized by means of XRD, HRTEM, UV-Vis DRS, NH₃-TPD and H₂-TPR.The characterization data indicated that amorphous tetrahedral and octahedral tungsten species were mainly incorporated into the framework of SBA-15 (Si/W mole ratio of 44), and further increase of the amounts of tungsten species led to the appearance of WO₃ in the channels of W-SBA-15 (Si/W mole ratio of 30 and 20).The metathesis catalytic performance of W-SBA-15 catalysts was better than that of the conventional WO₃/SiO₂ catalysts prepared by impregnation.Under the conditions of 300℃, 3.0 MPa and 6.4 h^-1, butene conversion was more than 50% with the propylene selectivity exceeding 96% during the 24 h continuous operation, using W-SBA-15 as the catalyst.The W-SBA-15 with the Si/W mole ratio of 44 exhibited the best dispersion of tungsten species inside the SBA-15 and the best catalytic performance of olefin metathesis among the W-SBA-15 catalysts.

Key words: 歧化, 丙烯, 2-丁烯, 催化剂