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本文对4,4-二甲基二氧六环-1,3裂解制异戊二烯的P_2O_5/SiO_2催化剂,用XRD,IR,DTA-DTG及NH_3吸附等方法,研究了其活性相的形成条件、结晶度以及它们对裂解反应的影响。结果证明配酸比为0.6的P_2O_5/SiO_2中的晶相Si_3(PO_4)_4是活性相,P_2O_5/SiO_2在>700℃,10小时的条件下,能充分形成这种结构,热稳定性良好。水分子使P_2O_5/SiO_2表面产生的B酸点和L酸点,在反应中发挥协同作用。
In this paper, the P_2O_5 / SiO_2 catalysts for pyrolysis of isoprene with 4,4-dimethyl-dioxane-1,3 are studied by means of XRD, IR, DTA-DTG and NH 3 adsorption. Conditions, crystallinity and their effect on the cleavage reaction. The results show that the crystalline phase Si_3 (PO_4) _4 in P_2O_5 / SiO_2 with acid ratio of 0.6 is the active phase and P_2O_5 / SiO_2 can form this structure under the condition of> 700 ℃ and 10h. The thermal stability is good. The water molecules make the B acid sites and the L acid sites generated on the surface of P 2 O 5 / SiO 2, which play a synergistic role in the reaction.