Using white carbon black and boric acid as the main raw materials, the B-β molecular sieve was synthesized by hydrothermal method. After the elution of boron with acid, the zinc-yttrium single rare earth element modification and the zinc-yttrium-erbium (neodymium) double rare earth element modification were carried out by the impregnation method to prepare a series of catalysts for the conversion of ethanol to butadiene. The surface structures of the catalysts were characterized and analyzed by SEM, TEM, XRD, N2 isothermal adsorption-desorption, TG-DTA and other methods. The results showed that the modification by dual rare earth elements had a synergistic effect, which improved the conversion rate of ethanol and the selectivity of butadiene. After the acid and alkali treatments of B-β molecular sieve precursor and the chemical modification with zinc and yttrium, sample (B-β-AT1-HCl-1Zn4Y) that loaded with 1% ZnO and 4% Y2O3 (mass fraction) exhibited the best catalytic activity. When the reaction was carried out with a space velocity of 6 h-1 at 400 ℃, the ethanol conversion rate of B-β-AT1-HCl-1Zn4Y reached 98.53% with the selectivity of butadiene being 55.58%. Further analysis demonstrated that the mesoporous structure can be introduced into the zeolite after alkali treatment, which increased the specific surface area of the catalysts, improved the diffusion performance of the carbon precursor in the zeolite pores, and enhanced the dispersion of zinc and yttrium species. The existence of these highly dispersed zinc and yttrium species as well as the mesoporous structures is a key factor for the high activity of the catalyst in one-step conversion of ethanol to butadiene.

ethanol; butadiene; B-β molecular sieve; rare earth elements