水热法改性氢氧化锆制备Pt-SO_4^(2-)/ZrO_2固体酸催化剂Ⅰ.水热温度的影响

Preparation of Pt-SO_4^(2-)/ZrO_2 Solid Acid Catalyst through Hydrothermal Modification of Zirconium HydroxideⅠ. Influence of Hydrothermal Temperature

通过水热法改性氢氧化锆制备了Pt SO2 -4 ZrO2 固体酸催化剂 ,并用低温氮吸附、X射线衍射、扫描电镜和差热分析等技术考察了氢氧化锆水热处理时的温度对Pt SO2 -4 ZrO2 固体酸物化性能及催化性能的影响 ,对水热改性的作用机理进行了讨论 .在连续微反 色谱装置上评价了催化剂对正戊烷异构化反应的催化活性 .用水热法对氢氧化锆粒子进行处理 ,可以使其形成较稳固的孔结构 .这种孔结构具有较高的热稳定性 ,可有效阻止焙烧过程中氧化锆粒子的烧结长大 .与室温老化制备的催化剂相比 ,由在 90～ 110℃下水热改性氢氧化锆所制备的催化剂的比表面积、硫含量和孔体积均有显著的提高 ,但催化剂的TOF下降 ;水热温度高于 13 0℃时 ,催化剂的TOF升高 .实验结果表明 ,由水热法得到的晶态水合氧化锆也可以制备SO2 -4 ZrO2

Pt-SO 2-_4/ZrO_2 solid acid catalyst was prepared from hydrothermally modified zirconium hydroxide. The physico-chemical properties of the hydrous zirconia and the catalyst were characterized by means of N_2-adsorption, XRD, SEM and DTA. The mechanism of the hydrothermal modification was also investigated in detail. The catalytic activity of the catalyst for isomerization of n-pentane was measured in a flow microreactor-chromatogram system. The influence of hydrothermal temperature on the reaction was studied. The zirconium hydroxide is converted into crystal hydrous zirconia at 130 ℃ and over. Under alkaline condition, the tetragonal and the monoclinic phases exist simultaneously. The crystal hydrous zirconia obtained by hydrothermal modification can also be used to prepare SO 2-_4/ZrO_2 solid acid. In comparison with normal preparation method, more stable pore structure of hydrous zirconia can be formed by hydrothermal modification. This stable structure can restrain sinter of zirconia particles when they are calcined. The surface area, pore volume and sulfur content of the catalyst prepared from Zr(OH)_4 hydrothermally modified at 90～110 ℃ increase remarkably, but the TOF on it decreases. If zirconium hydroxide is treated at 130～170 ℃, the TOF is enhanced.