摘要
制备了不同B2 O3 含量 (0～ 2 0 % )的B2 O3/TiO2 ZrO2 固体酸催化剂 ,用XRD ,FT IR ,N2 吸附及NH3 TPD等方法测定了其结构、比表面积、孔分布和表面酸性 .结果表明 ,当B2 O3 含量较低 (≤ 5 % )时 ,催化剂呈无定形态 ,样品中的B2 O3 主要以BO4 结构存在 .当B2 O3 含量较高 (≥ 8% )时 ,催化剂中的TiO2 ZrO2 以ZrTiO4 晶相存在 ,分散于TiO2 ZrO2 表面的B2 O3 主要以玻璃体形式和BO3 结构存在 .随着B2 O3 含量的增加 ,催化剂的比表面积减小 ,孔径增大 .30 0℃下的环己酮肟气相Beck mann重排反应结果表明 ,随着B2 O3 含量的增加 ,己内酰胺的选择性逐渐增大 ,而己内酰胺的收率在B2 O3 含量为 12 %时达到最大值 .讨论了B2 O3/TiO2 ZrO2
A series of B 2O 3/TiO 2 ZrO 2 solid acid catalysts with B 2O 3 loadings of 0～20% were prepared. The catalyst structure, BET surface area, pore size distribution, and acidity were characterized by XRD, FT IR, N 2 adsorption, and NH 3 TPD. The results revealed that when the boria loading ≤5%, the catalysts remained amorphous after calcination at 600 ℃ and the boron atoms in the catalysts was present mainly in tetrahedral BO 4 units. When the B 2O 3 loading ≥8%, TiO 2 ZrO 2 in the catalysts existed in ZrTiO 4 phase and B 2O 3 existed mainly as vitreous glass, which was constructed mainly by trigonal BO 3 units. As the B 2O 3 loading increased, the surface area of the catalysts decreased and the pore size became larger. The catalytic properties of the B 2O 3/TiO 2 ZrO 2 catalysts for Beckmann rearrangement of cyclohexanone oxime to ε caprolactam were investigated at 300 ℃. It was found that the caprolactam selectivity increased with increasing B 2O 3 loading, but the caprolactam yield showed a maximum at 12% boria loading. It is proposed that the caprolactam selectivity of the B 2O 3/TiO 2 ZrO 2 catalyst is closely correlated with its acid strength distribution and pore size.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2002年第1期9-14,共6页
