Catalyst for preparing methacrolein, preparation method and application of catalyst

The invention discloses a catalyst for preparing methacrolein. General formulas of active oxide components of the catalyst are expressed as [MoaBibX cOx]I,[X dX eX fX gOy]II and [Mo'hX<6.iOz]III; in the formulae, Mo and Mo' refer to molybdenum; Bi refers to bismuth; X1 refers to vanadium and/or tungsten; X2 refers to at least one of elements in the VIII group; X3 refers to at least one of sodium, potassium, rubidium and caesium; X4 refers to at least one of copper, antimony, manganese, zinc, magnesium, tin, lead, niobium, boron, phosphorus and chromium; X5 refers to at least one of rare earth elements comprising lanthanum, cerium, samarium, ytterbium and neodymium; X6 refers to at least one of silicon, aluminum, zirconium and titanium; according to atom ratios, a is equal to 8-12, b is equal to 0.1-3, c is equal to 0.01-1, d is equal to 0.1-4, e is equal to 0.01-3, f is equal to 0.01-2, g is equal to 0.01-3, h is equal to 1-3, and i is equal to 2-10; x, y and z are determined by atom ratios and valence states of the elements except the oxygen. The invention also provides a preparation method of the catalyst and application of the catalyst in preparation of methacrolein through C4 unsaturated alkene or unsaturated alcohol.