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

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

  • 摘要: 通过在ZrO2中掺杂TiO2,并在350-500 ℃下焙烧,制备了系列TiO2-ZrO2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Brønsted酸性位。焙烧温度≤400 ℃的TiO2-ZrO2复合氧化物形成Ti-O-Zr键,呈无定形态;焙烧温度>400 ℃的TiO2-ZrO2复合氧化物呈单斜相和四方相ZrO2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ZrO2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。

     

    Abstract: 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.

     

/

返回文章
返回