PROCESS FOR HETEROGENEOUSLY CATALYZED GAS PHASE PARTIAL OXIDATION OF (METH)ACROLEIN TO (METH)ACRYLIC ACID

A process for preparing (meth)acrylic acid by heterogeneously catalyzed gas phase partial oxidation of (meth)acrolein over a multimetal oxide composition which comprises the elements Mo, V and W and is obtained by a hydrothermal preparation route, and the multimetal oxide composition obtainable by this preparation route. 1. A process , comprising heterogeneously catalyzing a partial oxidation of (meth)acrolein to (meth)acrylic acid in the gas phase over a catalytically active multimetal oxide composition of formula (I):{'br': None, 'sub': 12', 'a', 'b', 'c', 'd', 'c', 'f', 'g', 'n, 'sup': 1', '2', '3', '4', '5', '6, 'MoVXXXXXXO\u2003\u2003(I),'}wherein:{'sup': '1', 'Xrepresents W, Nb, Ta, Cr, Ce, or a mixture thereof;'}{'sup': '2', 'Xrepresents Cu, Ni, Co, Fe, Mn, Zn, or a mixture thereof;'}{'sup': '3', 'Xrepresents Sb, Te, Bi, or a mixture thereof;'}{'sup': '4', 'Xrepresents H, one or more alkali metals, or a mixture thereof;'}{'sup': '5', 'Xrepresents one or more alkaline earth metals;'}{'sup': '6', 'Xrepresents Si, Al, Ti, Zr, or a mixture thereof;'}a represents 1 to 6;b represents 0.2 to 8;c represents 0 to 18;d represents 0 to 40;e represents 0 to 4;f represents 0 to 4;g represents 0 to 40;n represents a number determined by the valency and frequency of the elements in the formula (I) other than oxygen;{'sup': '1', 'at least 50 mol % of a total molar amount of elements Xpresent in the multimetal oxide composition of formula (I) is the element W; and'}the multimetal oxide composition of formula (I) is prepared by hydrothermally treating a mixture of sources of elemental constituents in the presence of water in a pressure vessel, such that a newly forming solid is removed as a precursor composition which is converted to the catalytically active multimetal oxide composition of formula (I) by thermal treatment.2. The process according to claim 1 , wherein the catalytically active multimetal oxide composition satisfies formula (II):{'br': None, 'sub': 12', 'a', 'b', ...