Catalyst

1 . A catalyst comprising molybdenum, antimony, bismuth and iron,

wherein an atom ratio of the antimony to the molybdenum on a surface of the catalyst is greater than an atom ratio of the antimony to the molybdenum in an entire catalyst,

a ratio B/A is 1.2 to 10.0, in which A is an atom ratio of the antimony to the molybdenum calculated by Inductively Coupled Plasma (ICP) emission spectroscopy, and B is a peak area ratio of the antimony to the molybdenum calculated by X-ray photoelectron spectroscopy, and

the catalyst comprises Formula (1):

Mo a Bi b Fe c Sb d M e X f Y g Si h O i   (1)

wherein, in Formula (1),

Mo, Bi, Fe, Sb, Si and O represent molybdenum, bismuth, iron, antimony, silicon and oxygen, respectively,

M represents at least one selected from the group consisting of cobalt and nickel,

X represents at least one element selected from the group consisting of zinc, chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, thallium, tungsten, phosphorus, boron, sulfur, selenium, tellurium, cerium and titanium,

Y represents at least one element selected from the group consisting of cesium, lithium, sodium, potassium, rubidium and thallium,

a, b, c, d, e, f, g, h and i represent an atomic ratio,

a=12, b=0.01 to 3.00, c=0.01 to 5.00, d=0.01 to 5.00, e=0.00 to 12.00, f=0.00 to 8.00, g=0.001 to 2.00, h=0.00 to 20.00, and

i represents an oxygen atom ratio required to satisfy a valence of each component.

2 . The catalyst according to claim 1 , wherein A is 0.04 or more and 0.20 or less.

3 . The catalyst according to claim 1 , wherein B is 0.05 or more and 0.50 or less.

4 . A method of producing an unsaturated aldehyde and/or an unsaturated carboxylic acid, comprising:

performing a gas phase oxidation reaction of an organic compound as a raw material in presence of the catalyst according to claim 1 ,

wherein the organic compound comprises at least one selected from the group consisting of propylene, isobutylene, t-butyl alcohol, and methyl-t-butyl ether.

5 . A method of producing a catalyst containing molybdenum and antimony, comprising:

mixing a molybdenum compound, an antimony compound, and a dispersant to produce a mixture; and

calcinating the mixture to produce the catalyst;

wherein, in the mixing, the dispersant is added before the antimony compound is dissolved,

an atom ratio of the antimony to the molybdenum on a surface of the catalyst is greater than an atom ratio of the antimony to the molybdenum in an entire catalyst

a ratio B/A is 1.2 to 10.0, in which A is an atom ratio of the antimony to the molybdenum calculated by Inductively Coupled Plasma (ICP) emission spectroscopy, and B is a peak area ratio of the antimony to the molybdenum calculated by X-ray photoelectron spectroscopy, and

the catalyst comprises Formula (1):

Mo a Bi b Fe c Sb d M e X f Y g Si h O i   (1)

wherein, in Formula (1),

Mo, Bi, Fe, Sb, Si and O represent molybdenum, bismuth, iron, antimony, silicon and oxygen, respectively,

M represents at least one selected from the group consisting of cobalt and nickel,

X represents at least one element selected from the group consisting of zinc, chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, thallium, tungsten, phosphorus, boron, sulfur, selenium, tellurium, cerium and titanium,

Y represents at least one element selected from the group consisting of cesium, lithium, sodium, potassium, rubidium and thallium,

a, b, c, d, e, f, g, h and i represent an atomic ratio,

a=12, b=0.01 to 3.00, c=0.01 to 5.00, d=0.01 to 5.00, e=0.00 to 12.00, f=0.00 to 8.00, g=0.001 to 2.00, h=0.00 to 20.00, and

i represents an oxygen atom ratio required to satisfy a valence of each component.

6 . The method according to claim 5 , wherein the dispersant comprises a hydrazine compound.

7 . The method according to claim 5 , wherein the antimony compound has a particle size of 0.21 μm or more and 7.90 μm or less.

8 . The catalyst according to claim 1 , wherein the ratio B/A is 1.2 or more and 8.0 or less.

9 . The catalyst according to claim 1 , wherein the ratio B/A is 1.5 or more and 6.0 or less.

10 . The catalyst according to claim 1 , wherein the ratio B/A is 1.8 or more and 4.0 or less.

11 . The catalyst according to claim 1 , wherein the ratio B/A is 2.0 or more and 3.5 or less.

12 . The catalyst according to claim 1 , wherein A is 0.06 or more and 0.16 or less.

13 . The catalyst according to claim 1 , wherein A is 0.08 or more and 0.12 or less.

14 . The catalyst according to claim 1 , wherein B is 0.13 or more and 0.40 or less.

15 . The catalyst according to claim 1 , wherein B is 0.15 or more and 0.35 or less.