Abstract: 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 temperature-programmed 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.

Key words: ultrasonic frequency, activated carbon, ruthenium, barium, potassium, supported catalyst, ammonia synthesis