MgAl-PdCl_4水滑石的合成与表征  

Preparation and characterization of MgAl-PdCl_4 hydrotalcite

作　　者：申延明[1] 王蕾[2] 李悦[3] 吴静[1] 张振祥[3] 刘长厚[1] 

机构地区：[1]大连理工大学化工学院,辽宁大连116012 [2]吉林工业职业技术学院,吉林吉林132013 [3]沈阳化工学院化学工程学院,辽宁沈阳110142

出　　处：《燃料化学学报》2007年第6期711-715,共5页Journal of Fuel Chemistry and Technology

基　　金：辽宁省教育厅科技基金(B类;2005330)。

摘　　要：以MgAl-NO3水滑石为前驱体,用离子交换法将PdCl42-作为客体插入水滑石的层间,通过XRD、IR、DTA、比表面积等表征制备的水滑石,探讨了Pd含量、插层时间、Mg/Al摩尔比以及焙烧温度对制备水滑石结构的影响。结果表明,插层产物中PdCl42-与NO3-共存于层间,PdCl42-的引入,减小了水滑石的层间距,PdCl42-引入量越多,层间距减少的越多。Mg/Al摩尔比在2～4均可以形成MgAl-PdCl4-HLTcs,但是其值增大时,水滑石的层间距逐渐降低。插层交换时间延长有利于PdCl42-插入层间,但从制备水滑石的角度看,晶化时间8h,即可得到结晶良好的水滑石化合物。DTA分析结果显示,在较高的PdCl42-引入量,或较高的Mg/Al摩尔比时层间PdCl42-失去Cl-转化成PdO的温度在370℃左右,层间NO3-的脱除温度在410℃附近;在低的PdCl42-引入量,或低的Mg/Al摩尔比两个脱除过程一起进行,在500℃左右完成。随着层间PdCl42-的分解及NO3-的脱除,400℃时MgO-Al2O3-PdO物相开始形成,600℃时基本形成完全,比表面积也达到最大,进一步提高焙烧温度至800℃,由于金属氧化物的晶粒变大及出现少量的MgAl2O4尖晶石物相,其比表面积有所下降。Intercalation of PdCl42- in MgAl-NO3 hydrotalcite was carried out by coprecipitation. The as-prepared MgAl-PdCl4 hydrotalcite was characterized by XRD, IR, DTA and nitrogen sorption. The effects of palladium concentration in the intercalation solution, intercalation time, Mg/Al mol ratio and calcination temperature on the structure of as-prepared hydrotalcite were investigated. The results illustrated that PdCl42- and NO3- coexist between layers and the intercalation of PdCl42- may reduce the interlayer spacing. Longer intercalation time is beneficial to the intercalation of PdCl42- and 8 h is enough to forming MgAl-NO3-HLTcs with good crystalline. MgAl-NO3-HLTcs can be formed at Mg/Al=2-4; the interlayer spacing decreases with the increase of the Mg/Al mol ratio. At high Pd content or high Mg/Al mol ratio, the decomposition temperatures for PdCl42- (to PdO) and NO3- is about 370°C and 410°C, respectively; however, at low Pd content or low Mg/Al mol ratio, the decompositions of PdCl42- and NO3- change from a continuous process to a discrete one. The destruction of hydrotalcite structure to MgO-Al2O3-PdO phase starts at 400°C and is nearly completed at 600°C. The surface area of hydrotalcite increases with the calcination temperature at first, reaches a maximum at 600°C, and then decreases when further increase of the calcination temperature due to the aggregation of particles and formation of spinel MgAl2O4.

关 键 词：水滑石 PdCl42-配离子 插层 热分解 

分 类 号：O611.4[理学—无机化学]