苯部分加氢制环己烯的非晶态Ru-M-B/ZrO_2催化剂的表征

Characterization of Amorphous Ru-M-B/ZrO_2 Catalysts for Partial Hydrogenation of Benzene to Cyclohexene

采用化学还原法 ,制备了高活性、高选择性非晶态 Ru- M- B/ Zr O2 催化剂 ,并将其用于催化苯部分加氢制环己烯 .在 140℃、 5 .0 MPa氢压下 ,苯转化 40 %时 ,环己烯选择性达到 85 %左右 ,环己烯最高收率达到5 2 .1% .用 XRD、SEM、BET比表面积测定等手段对催化剂进行表征 .XRD和 SEM测试表明 ,Ru- M- B/ Zr O2 属于非晶态 ,活性组分高度分散 .XRD结果证实 ,在加氢过程中 ,非晶分解 ,Ru晶化 ;温度愈高 ,Ru晶化愈快 ,催化剂的活性、选择性与 Ru微晶的粒径有关 ,Ru微晶粒径应控制在 5 nm左右 .BET比表面积测定表明 ,Zr O2 的负载提高了催化剂的比表面积 ,从而有利于活性组分的高度分散 ,并可阻止 Ru微晶的长大 .讨论了 B和 Zr O2

Amorphous Ru-M-B/ZrO-2 catalysts with high activity and selectivity for partial hydrogenation of benzene to cyclohexene were prepared by chemical reduction method. The selectivity to cyclohexene at 40% benzene conversion is about 85% and the highest yield of cyclohexene reaches to 52.1% at 140 ℃ and 5 MPa hydrogen pressure. The catalysts were characterized by XRD, SEM, BET techniques. XRD patterns and SEM pictures show that the catalysts are amorphous and Ru active component is highly dispersed on the support. It was confirmed by XRD that amorphous catalyst decomposes and ruthenium is crystallized during hydrogenation; crystallization speed up with the increase of temperature. It was found that Ru crystallite size has an effect on activity and selectivity, thus the size should be controlled around 5 nm. According to BET surface area measurement, the introduction of ZrO-2 can increase both the surface area of the catalyst and the dispersion of ruthenium, furthermore, it can prevent ruthenium crystallites from growing up. The promotion effects of boron and ZrO-2 on the selectivity to cyclohexene were also discussed.