Preparation of copper-based catalysts by ultrasonic co-impregnation to catalyze the hydrogenation of sec-butyl acetate

Abstract

Four different impregnation methods, namely ultrasonic co-impregnation, ultrasonic stepwise impregnation, co-impregnation and stepwise impregnation, were used to prepare Cu/B/Ca/Al₂O₃ catalyst. The effects of ultrasonic-assisted impregnation on the physicochemical properties, morphology and hydrogenation performance of sec-butyl acetate were investigated, and the difference between ultrasonic co-impregnation and ultrasonic stepwise impregnation was further explored. The catalysts were characterized by inductively coupled plasma atomic emission spectrometry, X-ray diffraction, scanning electron microscopy, Transmission electron microscope and N₂ physical adsorption-desorption. The results indicate that ultrasonic-assisted treatment can reduce the agglomeration of copper particles, and that the active components are uniformly dispersed on the surface of the catalyst, expanding the specific surface area and, thus, increasing the conversion of sec-butyl acetate from 79.6% to 99.8%, and the selectivity of sec-butanol from 63.5% to 70.2%. In addition, the reaction pressure is reduced from 8 MPa to 5 MPa compared to the conventional impregnation.Ultrasonic co-impregnation is more advantageous than ultrasonic stepwise impregnation, since it can shorten the catalyst preparation cycle, avoid loss of B₂O₃ and CaO components during the secondary impregnation, expand the effective contact area between Ca and Cu species, increase the electron transfer rate from Ca to Cu, avoid the increase of Cu⁺/Cu and finally ensure the hydrogenation activity of the catalyst. The catalyst has the highest reactivity at an ultrasonic power of 80 W and within the duration of 0.75h. However, continued increase in ultrasonic power and time leads to catalyst deactivation. A long term test for catalyst stability which lasted for 200h had been run at 226 °C, 5 MPa H₂, space velocity = 0.5h⁻¹.

Graphical Abstract

Keywords:

• Ultrasonic co-impregnation
• catalyst preparation
• copper-based catalyst
• sec-butyl acetate
• hydrogenation

Additional information

Funding

Authors from Hebei University of Technology acknowledgement the support of the Key Research and Development Program of Hebei (Grand No. 18273609D).