Patent ID: 7304179

Claim:
A method for producing methacrylic acid through gas-phase catalytic oxidation of methacrolein or a methacrolein-containing gas with molecular oxygen or a gas containing molecular oxygen by the use of a fixed-bed multitubular reactor comprising a plurality of reaction tubes each having a catalyst layer therein, wherein the above catalyst layer is divided in the direction of the tube axis of a reaction tube into two or more layers, to thereby provide a plurality of reaction zones, and the catalyst is caused to be present in the catalyst layer in such a way that a reaction load ratio CRc(i) per unit mass of the catalyst in each reaction zone defined by the following equations (1) to (3) becomes 0.8 to 1.0, CRc ⁡ ( i ) = Rc ⁡ ( i ) / RcMAX ( 1 ) Rc ⁡ ( i ) = [ ∑ j = 1 m - 1 ⁢ { Δ ⁢ ⁢ T i ⁡ ( j ) + Δ ⁢ ⁢ T i ⁡ ( j + 1 ) } · L i ⁡ ( j ) 2 ] / Wc ⁡ ( i ) ( 2 ) Δ ⁢ ⁢ T i ⁡ ( j ) = T i ⁡ ( j ) - TB ( 3 ) wherein Rc(i) is the reaction load of an i th layer (° C.·m/kg), Li(j) is a distance (m) from a j th measuring point in a i th catalyst layer to the j+1 th measuring point in the direction of the tube axis, Wc(i) is a packing amount (kg) of the catalyst in the i th layer, Ti(j) is a catalyst-layer temperature (° C.) of the j th measuring point in the i th catalyst layer, TB is a heat transfer medium temperature (° C.), RcMAX is a maximum value of Rc(i), n is the number of the reaction zones, and m is the number of the temperature measuring points in the i th catalyst layer; i is 1 to n; i and j are counted in turn from the inlet side of the reaction gas.