Method for producing (meth)acrolein and method for producing (meth)acrylic acid

A method for producing (meth) acrolein, the method comprising:

• oxidizing propylene or isobutylene by vapor-phase catalytic oxidation in a multitubular reactor comprising a plurality of reaction tubes, the reaction tubes each comprising (i) a reaction zone filled with a catalyst comprising molybdenum oxide and (ii) a cooling zone comprising an inert substance,
• wherein the catalyst has a spherical shape, a solid-cylindrical shape, a hollow-cylindrical shape, a star shape, and/or a ring shape,
• wherein a temperature of a heat medium that flows outside the cooling zone is lower than a temperature of a heat medium that flows outside the reaction zone, and
• wherein the inert substance has a major-axis length that is equal to or more than 1.7 times and equal to or less than 3.4 times a major-axis length of the catalyst, and
• wherein the substance has a thermal conductivity satisfying formula (1):
• K
• IS
• ≤
• K
• MO
• x
• ×
• 0.1
• ,
• (
• 1
• )
• wherein KIS is the thermal conductivity of the inert substance, and KMOx is the thermal conductivity of molybdenum oxide.