The present invention provides methods for monomer production, for example, acrylic acid, wherein the methods comprise oxidizing one or more reactant gases, for example, propylene, in a fixed bed reactor, preferably, two fixed bed reactors, in the presence of oxygen and a mixed metal oxide catalyst to form an oxidized gaseous mixture and, at any point in the oxidizing, feeding or flowing the one or more reactant gases or the oxidized gaseous mixture through an inert macroporous material that has a pore volume of from 0.2 cm3/g to 2.0 cm3/g, a surface area of from 0.01 to 0.6 m2/g, and wherein from 30 to 98 wt. % of the total pore volume in the inert macroporous material has a pore diameter of at least 100 μm.