经Al掺杂改性的介孔CaZr_4(PO_4)_6的酸催化活性

Catalytic activity of acidic mesoporous CaZr_4(PO_4)_6 modified by doping Aluminum

对溶胶-凝胶法合成的NZP族介孔CaZr4(PO4)6进行Al掺杂改性,获得了一系列含Al的新型酸性催化剂样品Al-CaZr4(PO4)6。利用X射线衍射、X射线荧光、N2吸附-脱附和NH3的程序升温脱附等技术,表征了样品的物相、Al掺杂量、孔结构和表面酸性;以α-蒎烯的异构化为模型反应表征了样品的酸催化活性。结果表明:经适量Al掺杂改性后的CaZr4(PO4)6仍保持了均匀分布的介孔结构特征,与未经掺杂的CaZr4(PO4)6相比,表面酸性有明显提高。当掺杂的Al与CZP中Zr的物质的量的比分别为0.15和0.20时,获得的催化剂样品Al-CaZr4(PO4)6-0.15和Al-CaZr4(PO4)6-0.20在150℃下对α-蒎烯异构化反应的转化率可以达到40%～47%,而未经掺杂改性的介孔CaZr4(PO4)6在相同反应条件下对α-蒎烯异构化反应的转化率仅为3%,因此,Al掺杂改性可以显著提高介孔CaZr4(PO4)6的酸催化活性。

A new type of acidic catalyst Al-CaZr4 （PO4 ）6 is obtained by doping Aluminum in mesoporous CaZr4 （PO~） 6 belonging to NZP family synthesized via sol-gel method. The phase, doping amount of A1, pore structure and surface acidity of the samples are characterized by X-ray diffraction （XRD） , X-ray fluorescence （XRF）, N2 adsorption and NH3 temperature programmed desorption （ NH3-TPD） , respectively. The catalytic activity and selectivity of the synthesized acidic catalysts are investigated by using α-pinene isomerization as the probe reaction. The results show that mesoporous characteristics of the Al-doped CaZr4 （ PO4 ） 6 are remained. When compared with the non-doped samples, the surface acidity of Al-containing CaZr4 （ PO4 ） 6 is obviously improved. When α-pinene isomerization is catalyzed by Al- CaZr4（PO4）6--0.15 and Al-CaZr4（PO4）6-0.20 at 150℃ for 4 hours with 0.15 and 0. 20 of the mole ratio of Al to Zr, respectively,the conversion of α-pinene can reach 40% -47%. However,the conversion of α-pinene catalyzed by non doped samples is only 3 % under the same condition. Therefore, the catalytic activity of mesoporous CaZr4 （ PO4 ） 6 can be greatly improved by doping Al.