The present invention relates to a process for preparing acrylic acid comprising (i) providing a stream comprising a formaldehyde source and acetic acid and (ii) contacting this stream with an aldol condensation catalyst comprising a zeolitic material, wherein the framework structure of the zeolitic material in (ii) includes Si and O, and has a molar Al:Si ratio of 0:1 to 0.001:1, and wherein the framework structure of the zeolitic material in (ii), in addition to Si and any Al, comprises one or more elements selected from the group consisting of tetravalent elements Y other than Si and trivalent elements X other than Al.