Catalyst for preparing butadiene through catalytic conversion of ethanol as well as preparation and application of catalyst

The invention provides a catalyst for preparing butadiene from ethanol as well as preparation and application of the catalyst. The catalyst comprises a dealumination Beta molecular sieve carrier, an Nb active component and a second metal active component, wherein the Nb active component and the second metal active component are loaded on the carrier; the second metal is selected from one or two of Zn, Cu, Co, Ag and Ni; nb exists on the Beta molecular sieve in the form of isolated Nb (V) of framework coordination. The catalyst has high ethanol conversion rate and butadiene selectivity, the dealuminated Beta molecular sieve is large in specific surface area and has defect sites, dispersion and anchoring of metal active components are facilitated, the active component Nb exists in the form of isolated Nb (V) coordinated with a framework on a Beta carrier and presents Lewis acidity, and the Beta molecular sieve has good catalytic activity. An acetaldehyde aldol condensation active center is provided for the cata