镁-铝水滑石及其衍生复合氧化物的合成

用共沉淀法制备Mg Al水滑石。利用XRD、BET等手段 ,考察了共沉淀剂、pH值、原料的滴加速度、搅拌速度、晶化温度、晶化时间、焙烧温度等合成条件对合成物相、结晶度及其衍生复合氧化物的比表面、孔径的影响。实验结果表明 ,共沉淀剂种类不影响水滑石的晶体形成 ;单一晶相水滑石形成的pH值范围为 8.5～ 9.0 ;镁与铝摩尔比 (nMg∶nAl)、晶化温度及晶化时间对水滑石的结晶度有影响 ,水热晶化法晶化时间短 ,且所得晶型好、晶粒大 ;原料的滴加速度、搅拌速度、焙烧温度对所得Mg Al O复合氧化物的比表面及孔径也有影响。由其衍生复合氧化物为载体制备的加氢脱硫催化剂的氢脱硫 (HDS)与氢氧化物 (HYD) ,随nMg∶nAl值及水滑石在载体中的质量分数的提高而降低 ,但HDS/HYD值降低 ,即对HDS的影响大于对HYD的影响。

Synthesis of magnesium-aluminum mixed oxide from hydrotalcite and its performances as catalytic support

Magnesium Aluminum hydrotalcite compounds were synthesized using the co precipitation method. The physical properties of prepared hydrotalcite and the magnesium aluminum oxygen mixed oxide obtained from hydrotalcite were analyzed by means of XRD, TG DTA, BET techniques. The effects of synthesis conditions, pH value, co precipitation agents, feed rate of reactants, stirring rate, crystal temperature and time, calcination temperature and magnesium aluminum ratio on crystal phase, crystal degree, special area and average pore size of hydrotalcite and magnesium aluminum oxygen mixed oxides were investigated. The experiment results showed that the co precipitation agents had no effect on the structure of hydrotalcite. The optimum pH value for pure hydrotalcite crystal was in the range of 8.5 to 9.0. The magnesium aluminum ratio, ageing temperature and ageing time had some effects on the hydrotalcite crystal degree. The stirring rate, feed rate of reactants and calcination temperature affected the special area and pore size of magnesium aluminum oxygen mixed oxide obtained from magnesium aluminum hydrotalcite. The hydrodesulfurization (HDS) and hydroxide (HYD) of catalysts prepared when taking magnesium aluminum mixed oxide as support decreased along with the increase of magnesium aluminum ratio and the content of hydrotalcite in the support, and the hydrodesulfurization hydroxide ratio decreased. The increase of magnesium aluminum ratio had a greater effect on HDS than that on HYD.