B_2O_3/SiO_2-钛铌酸催化剂上环己酮肟气相Beckmann重排

以氨丙基三乙氧基硅烷(APS)为硅源,采用分步离子交换法制备了SiO2柱层状钛铌酸(SiO2-HTiNbO5);以SiO2-HTiNbO5为载体,用浸渍法制备了B2O3/SiO2-HTiNbO5催化剂,并用X射衍射光谱和傅里叶变换红外光谱对催化剂结构进行了表征;考察了催化剂在环己酮肟气相Beckmann重排生成己内酰胺反应中的性能。实验结果表明,当B2O3负载量(质量分数)小于2.00%时,B2O3高度分散于SiO2-HTiNbO5的表面,主要以BO4结构形式存在;当B2O3负载量大于7.32%时,B2O3呈现非晶态,BO3结构形式在数量上占优势;当B2O3负载量为7.32%时,BO4和BO3在数量上相当。B2O3/SiO2-HTiNbO5催化剂的活性和选择性明显地优于SiO2-HTiNbO5,当B2O3负载量为7.32%时,环己酮肟转化率维持在97.0%以上的时间达400min以上,己内酰胺选择性大于98.0%。在环己酮肟重排生成己内酰胺的过程中,BO3和BO4两种结构形式的硼氧物种具有协同促进作用。

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime over B2O3/SiO2-Pillared HTiNbO5

SiO2-pillared titanic-niobic acid(SiO2-HTiNbO5)was synthesized by ionexchange with aminopropyl triethoxysilane(APS)as silicon source.By impregnating SiO2-HTiNbO5 in H3BO3 solution,a series of supported boric oxide catalysts(B2O3/SiO2-HTiNbO5)with different B2O3 loadings were prepared.The catalysts were characterized by means of XRD and FTIR.The highly dispersed BO4 species were on the surface of catalyst with B2O3 loading less than 2.00%(mass fraction).Non-crystalline boric oxide particles,mainly BO3 species,were found on the catalyst when B2O3 loading was higher than 7.32%.The vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam was carried out on SiO2-HTiNbO5 and B2O3/SiO2-HTiNbO5 catalysts.B2O3/SiO2-HTiNbO5 is much more active and selective for the rearrangement than SiO2-HTiNbO5.B2O3/SiO2-HTiNbO5 with 7.32% B2O3 shows excellent catalytic activity.Cyclohexanone oxime conversion and ε-caprolactam selectivity keep more than 97.0% and 98.0% respectively after reaction for 400min.BO3 and BO4 have synergetic effect for vapor-phase Beckmann rearrangement.