摘要:
To analyze the effects of calcination on the catalytic performance of H-mordenite,H-mordenite (Si/Al =16) was calcined at 300°C,550°C and 700°C,and all the catalysts were characterized by using BET,XRD,NH3-TPD and Py-IR.The specific surface area,pore volume,the intensities of Lewis/Br(o)nsted acid and strong/weak acid of the samples were further investigated.The catalysts were used in the isomerization reaction of a-pineneat atmospheric pressure under nitrogen flow.The effects of specific surface area,pore volume,the intensities of Lewis/Br(o)nsted acid and strong/weak acid on the activity and product selectivity of the catalysts were analyzed by the conversion of α-pinene and selectivity to any product.The results showed that the samples could be activated by calcinations at 550°C.The Br(o)nsted acid and Lewis acid contents decreased significantly in the range of 300-700°C.The decrease of the former was higher than that of the latter.Meanwhile,the weak acid and strong acid contents of the zeolites also decreased with the rising calcinations temperature,but the strong acid content reduced faster than the weak acid content.The isomerization of α-pinene indicates it is favorable for the formation of camphene when the content of Lewis acid is higher than that of Br(o)nsted acid.When the reaction time of α-pinene isomerization with 700HM06 was 12 h,the conversion of α-pinene was 97.35%,and the selectivity of comphene and monocyclic products were 43.83% and 52.05%,respectively.Therefore the optimized calcination temperature is 700°C.%为研究焙烧对H-丝光沸石催化性能的影响,在300,550和700°C条件下焙烧H-丝光沸石(硅铝比为16),通过N2吸附-脱附仪(BET)、XRD、NH3-TPD、Py-IR对沸石进行表征,研究了焙烧后沸石的比表面积、孔结构、Lewis酸、Br(o)nsted酸及强、弱酸的变化情况.以焙烧沸石为催化剂进行催化α-蒎烯异构反应,通过α-蒎烯转化率、莰烯、单环萜烯的选择性,分析了沸石结构和Lewis酸、Br(o)nsted酸及强、弱酸的变化对反应活性及产物选择性的影响.结果表明:沸石在550°C得以活化,在300~ 700°C焙烧范围内,沸石中Lewis酸和Br(o)nsted酸量明显减少,Br(o)nsted酸量减少速度更快;同时沸石强、弱酸也随焙烧温度升高而减少,强酸减少速度高于弱酸.α-蒎烯异构试验结果表明,Lewis酸量大于Br(o)nsted酸量时更有利于α-蒎烯异构产物向莰烯转化,样品700HM06与α-蒎烯反应12h时,α-蒎烯转化率达到97.35%,莰烯选择性为43.83%,单环萜烯选择性为52.05%,较其他温度焙烧的催化剂具有更高的转化率和莰烯选择性,因此700°C是最佳的焙烧温度.