焙烧温度对TiO2-ZrO2复合氧化物性质及其对十八醇脱水制十八烯反应性能的影响

通过在ZrO_2中掺杂TiO_2,并在350-500℃下焙烧,制备了系列TiO_2-ZrO_2复合氧化物催化剂,将其应用于十八醇脱水制十八烯反应。随焙烧温度的升高,催化剂表面的Lewis酸性位量逐渐增加,450℃焙烧的催化剂Lewis酸性位量最多,焙烧温度继续升高则Lewis酸性位量降低;催化剂中未发现Br?nsted酸性位。焙烧温度≤400℃的TiO_2-ZrO_2复合氧化物形成Ti-O-Zr键,呈无定形态;焙烧温度400℃的TiO_2-ZrO_2复合氧化物呈单斜相和四方相ZrO_2晶型。晶相结构和酸性位量综合影响催化剂的十八醇脱水性能,具有单斜相和四方相ZrO_2晶型的催化剂上酸性位活性很低,具有无定形相的催化剂上酸性位活性显著增加,400℃焙烧的催化剂1-十八烯收率最高。

Effect of calcination temperature on the properties of the mixed TiO2-ZrO2 oxides and their performance in the dehydration of octadecanol to octadecene

A series of mixed TiO₂-ZrO₂ oxide catalysts used for the dehydration of octadecanol to octadecene were prepared by doping TiO₂ in ZrO₂ and calcining at 350-500 ℃. With the increase of calcination temperature, the amount of Lewis acid sites on the catalyst surface gradually increases. The amount of Lewis acid sites on the catalyst calcined at 450 ℃ is the most, and when the calcination temperature is over 450 ℃, the amount of Lewis acid sites decreases. No Brønsted acid sites are found on the catalysts. The mixed TiO₂-ZrO₂ oxides calcined at temperature below 400 ℃ contain Ti-O-Zr bonds and amorphous structure. The mixed TiO₂-ZrO₂ oxides with calcination temperature above 400 ℃ show monoclinic and tetragonal phases of ZrO₂. The crystalline phase of the metal oxides and amount of the acid sites simultaneously affect the performance of the catalysts. The acid sites on the mixed TiO₂-ZrO₂ oxides with amorphous structure have much higher dehydration activity than those with monoclinic and tetragonal zirconia crystalline phases. The catalyst calcined at 400 ℃ has the highest yield of 1-octadecene.