Gas phase beckmann rearrangement of cyclohexanone oxime over zirconia-supported boria catalyst
Gas phase beckmann rearrangement of cyclohexanone oxime over zirconia-supported boria catalyst
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DOI：
10.1016/s0926-860x(99)00255-0
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发表时间：
1999-11
影响因子：
5.5
通讯作者：
Bo-Qing Xu;Shi Cheng;Shanglei Jiang;Qiming Zhu
中科院分区：
文献类型：
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作者：
Bo-Qing Xu;Shi Cheng;Shanglei Jiang;Qiming Zhu
以B2O3/ZrO2为催化剂，在250~350℃下研究了环己酮肟的气相贝克曼重排反应。结果表明，B2O3/ZrO2 在 300-320°C 下对 ε-己内酰胺的合成具有高活性和选择性。在 300°C 下，以 10% B2O3 为基础，将 B2O3/ZrO2 催化剂的活性和选择性与负载在 Al2O3、TiO2、SiO2、MgO 和 HZSM-5 (Si/Al=25) 上的其他氧化硼催化剂进行了比较。在此氧化硼负载水平下，B2O3/ZrO2 对内酰胺合成产生最佳催化作用。氧化硼的负载水平影响B2O3/ZrO2催化剂的行为：增加氧化硼负载量(≤20%)会导致内酰胺选择性增加，但内酰胺产率随着肟转化率的变化而变化，在氧化硼负载量为10%时显示出最大值。 B2O3/ZrO2 催化剂的酸度和氧化硼分散结构分别通过 NH3-TPD 和红外光谱测量。结果表明，内酰胺产率与负责 200-400°C 氨解吸的中间强酸位点的数量相关。 B2O3/ZrO2 催化剂的最佳氧化硼负载量（10%）对应于载体上的两层氧化硼。第一层氧化硼以四面体BO4为结构单元，直接与支撑面相互作用；硼砂的其他层由三角形的 BO3 单元构成。
Gas phase Beckmann rearrangement of cyclohexanone oxime is studied with B2O3/ZrO2as the catalyst at 250–350°C. It is shown that B2O3/ZrO2is highly active and selective for the synthesis of ε-caprolactam at 300–320°C. Activity and selectivity of the B2O3/ZrO2catalyst are compared with other boria catalysts supported on Al2O3, TiO2, SiO2, MgO, and HZSM-5 (Si/Al=25) on an 10% B2O3basis at 300°C. At this boria load level, B2O3/ZrO2produces the best catalysis for the lactam synthesis. The load level of boria affects the behavior of B2O3/ZrO2catalyst: increasing the boria load (≤20%) results in an increase of the lactam selectivity, but the lactam yield follows variation of the oxime conversion which shows a maximum at 10% boria load. Acidity and boria dispersion structure of the B2O3/ZrO2catalysts are measured, respectively, by NH3-TPD and IR spectroscopy. It is shown that the lactam yield is correlated with the number of intermediate strong acid sites that are responsible for ammonia desorption at 200–400°C. The optimum boria load (10%) of the B2O3/ZrO2catalyst corresponds to two overlayers of boria on the support. The first layer of boria interacts directly with the support surface with tetrahedral BO4as the structure unit; the other layers of boria are constructed by trigonal BO3units.