| abstract |
A catalyst is herein disclosed, which comprises a mixture of a composition (1) represented by the following general formula (1): n n (Mo).sub.a (Bi).sub.b (Fe).sub.c (X).sub.d (Z).sub.f (O).sub.g (1) n n (wherein X represents one or both of Ni and Co, Z represents at least one element selected from the group consisting of W, Be, Mg, S, Ca, Sr, Ba, Te, Se, Ce, Ge, Mn, Zn, Cr, Ag, Sb, Pb, As, B, P, Nb, Cu, Cd, Sn, Al, Zr and Ti, a, b, c, d, f and g each represents an atomic ratio of each corresponding element and if a is assumed to be 12, b ranges from 0.1 to 10, c ranges from 0 to 20, d ranges from 0 to 20 and f ranges from 0 to 4 and g is a number of oxygen atom required for satisfying the valency requirement of the foregoing elements) and a composition (2) represented by the following general formula (2): n n (A).sub.m (Mo).sub.n (O).sub.p (2) n n (wherein A represents at least one element selected from K, Rb and Cs and m, n and p each represents an atomic ratio and if m is assumed to be 2, n ranges from 1 to 9 and p is 3n+1). The catalyst has improved activity, selectivity to methacrolein and stability and accordingly, methacrolein can be prepared, in good yield, by a gas-phase catalytic oxidation reaction of isobutylene or tertiary butanol with molecular oxygen through the use of the foregoing catalyst. |