Metal oxide catalyst, method for producing same, and apparatus for producing same

A metal oxide catalyst suitable to produce a conjugated diolefin by an oxidative dehydrogenation reaction between a monoolefin, having 4 or more carbon atoms, and molecular oxygen, the metal oxide catalyst comprising a bulk composition represented by the formula (1):

• Mo12BipFeqAaBbCcDdEeFfOx (1)
• wherein A is at least one type of element selected from the group consisting of Ni and Co, B is at least one type of element selected from among alkali metal elements, C is at least one type of element selected from the group consisting of Mg, Ca, Sr, Ba, Zn and Mn, D is at least one type of rare earth element, E is at least one type of element selected from the group consisting of Cr, In and Ga, F is at least one type of element selected from the group consisting of Si, Al, Ti and Zr, O is oxygen, p, q, a, b, c, d, e, f and x denote the number of atoms of Bi, Fe, A, B, C, D, E, F and oxygen, respectively, relative to 12 Mo atoms, and are such that 0.1≤p≤5, 0.5≤q≤8, 0≤a≤10, 0.02≤b≤2, 0≤c≤5, 0≤d≤5, 0≤e≤5 and 0≤f≤200, and x is the number of oxygen atoms required to satisfy valency requirement of other elements present,
• wherein a standard deviation of the bulk composition is 0.3 or less, the standard deviation defined by the following formula (2):
• Standard deviation={((S1−μ)2+(S2−μ)2+ . . . +(S100−μ)2)/100[number]}1/2 (2)
• wherein Sk (k is integer of from 1 to 100) is a value obtained by dividing a ratio (Bi/Mo)surf by a ratio (Bi/Mo)bulk,
• wherein the ratio (Bi/Mo)surf is a Bi molar concentration relative to a Mo molar concentration, determined by a SEM-EDX (Scanning Electron Microscopes-Energy Dispersive X-Ray Spectroscopy) compositional analysis, at a surface of the kth catalyst particle among 100 catalyst particles arbitrarily selected, a ratio (Bi/Mo)bulk is the ratio of the Bi molar concentration relative to the Mo molar concentration in the catalyst bulk, as determined by an ICP emission spectroscopic analysis, and μ is an average value of Sk of the 100 catalyst particles arbitrarily selected as defined as (S1+S2 . . . +S100)/100).