Abstract

An efficient catalyst for the reaction of ethanol–acetaldehyde into 1,3-butadiene (EATB) is prepared through the grafting of zirconia into a zeolite Beta lattice. The grafting is achieved through the dealumination of a zeolite framework by acid treatment followed by zirconia impregnation, leading to the substitution of aluminum in the zeolite framework by zirconia. The catalyst with zirconia grafted into the zeolite framework promotes desirable catalyst properties like high zirconium dispersion, stability, and the close proximity of Lewis acid, Bronsted acid, and medium basic sites. The phase, the coordination of zirconia, the location of the active center and the cooperative synergism were elucidated through various characterization techniques, including X-ray diffraction, Raman spectroscopy, N2 adsorption, UV–vis spectroscopy, XPS, 29Si MAS NMR, NH3-TPD, Py-IR, CO-IR and CO2-TPD. The catalytic results show that a suitable phase and content of zirconia were needed to improve the ethanol–acetaldehyde conversion, butadiene selectivity and catalyst stability. Among the catalysts, m+t-ZrOx-Beta-H2O-9020 (m = monoclinic, t = tetragonal ZrO2 phase) achieved the best butadiene selectivity of 82–73% at the conversion of 100–66%, run over 200 h. The results allow us to propose a Lewis acid–medium basic pairing for the Si–O–Zr–O–Si group, where the adjacent Si-OH is the active center for reactions.

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