【摘要】 利用等体积浸渍法制备了氧化铝负载钌基氨合成催化剂 .考察了氢氧化铝的焙烧温度 ,催化剂的还原温度 ,助剂K、Ba和Sm的添加 ,以及用MgO和BaO改性氧化铝载体等对催化剂活性的影响 .通过XRD ,N2 物理吸附和CO2 化学吸附等方法表征了载体的物相结构、比表面积和表面碱性 .研究结果表明 ,氧化铝表面碱性随着氢氧化铝焙烧温度的升高而增大是催化剂活性升高的主要原因 ,载体比表面积的降低对催化剂活性的影响相对较小 .助剂K、Ba和Sm的加入显著地提高了催化剂的活性 ,同时助剂Ba和Sm还减弱了强吸附氢对氮吸附的抑制作用 ,明显提高了催化剂的高压活性 .用MgO改性氧化铝载体降低了其比表面积 ,但是显著地提高了载体的表面碱性和催化剂的活性 .BaO改性的氧化铝载体的比表面积、表面碱性及其负载的钌基催化剂的活性随着BaO含量的增加先升高后降低 ,当BaO摩尔含量为 7.7%时 ,催化剂活性最高更多还原

【Abstract】 The ruthenium catalyst supported on alumina was prepared by the method of incipient wetness impregnation. Ammonia synthesis over the catalyst was performed under the conditions of 0～10 MPa, 425 or 475 ℃, and space velocity of 20?000 h -1 with synthesis gas of N 2 H 2 (1∶3). X ray diffraction, nitrogen physical adsorption, and CO 2 chemisorption were employed to characterize the phase, specific surface area, and surface basicity of alumina. With the increase of Al(OH) 3 calcination temperature from 600 to 900 ℃, the surface basicity of alumina increased from 0 51 to 0 75 mmol/g, the specific surface area of alumina decreased from 223 to 140 m 2/g. The calcination temperature of 800 ℃ gave the highest activity of Ba Ru K/Al 2O 3 (39 38 mmol/(g·h) at 5 MPa and 475 ℃). The presence of promoters K, Ba, and Sm increased significantly the activity of Ru/Al 2O 3, furthermore, promoters Ba, and Sm weakened the strong adsorption of hydrogen on the Ru sites, which increased greatly the activity of Ru/Al 2O 3 at high pressures. The surface basicity of alumina modified with MgO increased from 0 68 to 1 01 mmol/g, the specific surface area of alumina decreased from 168 to 72 m 2/g, and the activity of Ba Ru/Al 2O 3 MgO increased from 17 52 to 65 76 mmol/(g·h) (at 5 MPa and 475 ℃) when the mole content of MgO in alumina increased from 0 to 75%. While the surface basicity, specific surface area of alumina modified with BaO, and the activity of Ru K/Al 2O 3 BaO first increased and then decreased with the increase of the mole content of BaO in alumina from 0 to 33 3%. When the mole content of BaO was equal to 7 7%, the highest activity (34 47 mmol/(g·h) at 5 MPa and 475 ℃) was obtained. If the mole content of BaO in alumina further increased, the specific surface area of alumina, and the activity of Ru K/Al 2O 3 BaO would decrease dramatically because the Al 2O 3 BaO mixture oxide was present in the phase of BaAl 2O 3.更多还原