超声频率对活性炭结构及钌/活性炭氨合成催化剂催化活性的影响

Effect of Ultrasonic Frequency on Structure of Activated Carbon and Activity of Ru/AC Catalyst for Ammonia Synthesis

采用超声波处理活性炭,运用场发射扫描电镜、N2物理吸附和程序升温脱附-质谱等表征手段,考察了超声处理对活性炭的表面形貌、孔结构以及表面基团的影响.以不同超声频率处理后的活性炭为载体,以钡和钾为助剂制备了一系列钌基氨合成催化剂,并考察了其性能.结果表明,随着超声频率的提高,活性炭的杂质含量明显降低,中孔比表面积增加,表面不稳定基团的数量减少.当采用功率100W,频率39·0kHz的超声探头处理30min时,活性炭表面的杂质含量较低,中孔比表面积适中,以其为载体制备的钌基氨合成催化剂的活性较高,在GHSV=10000h-1,10·0MPa和425℃的反应条件下,反应速率达到101·0mmol/(g·h).

The effect of ultrasonic frequency on the structure, surface texture, and surface groups of activated carbon （AC） was investigated by field-emission scanning electron microscopy, N2 adsorption, and temperatureprogrammed desorption. The results showed that increasing the ultrasonic frequency could effectively remove the impurities in AC, enhance the mesopore surface area, and decrease the amount of decomposable surface groups on AC. Furthermore, the ultrasonic treatment made the surface and holes of AC clean. Under the treatment of ultrasound with a power of 100 W and a frequency of 39.0 kHz for 30 min, the ash content in AC was lower, and the mesopore surface area was moderate. The catalytic activity of a series of barium-potassium-promoted Ru/AC catalysts for ammonia synthesis was evaluated under the conditions of GHSV = 10 000 h^-1, 10.0 MPa, and 425℃. The results showed that the rate of the catalytic reaction was increased from 90.1 to 101.0 mmol/ （g·h） with the increase of ultrasonic frequency from 19.7 to 39.0 kHz.