A method of making acrylic acid, metal or ammonium salts of acrylic acid, alkyl esters of acrylic acid, acrylic acid oligomers, or mixtures thereof comprising contacting the following compositions under conditions including a water partial pressure and a temperature: a gas mixture comprising: a) hydroxypropionic acid, metal or ammonium salts of lactic acid, alkyl esters of lactic acid, lactic acid oligomers, cyclic di-esters of lactic acid, lactic acid anhydride, 2-alkoxypropionic acids or their alkyl esters, 2-aryloxypropionic acids or their alkyl esters, 2-acyloxypropionic acids or their alkyl esters, metal or ammonium salts of 3-hydroxypropionic acid, alkyl esters of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-alkoxypropionic acids or their alkyl esters, 3-aryloxypropionic acids or their alkyl esters, 3-acyloxypropionic acids or their alkyl esters, or mixtures thereof; and b) water vapor; with a dehydration catalyst consisting essentially of one or more amorphous phosphate salts, one or more crystalline phosphate salts, and one or more non-phosphate salts and amorphous silica, wherein the amorphous phosphate salt is KH 2(1-x) PO (4-x), wherein the non-phosphate salt is BaSO 4, and the crystalline phosphate salt is Ba 2 P 2 O 7, wherein x is any real number equal to or greater than 0 and equal to or less than 1; wherein the water partial pressure during said contacting step in said gas mixture is equal to or greater than the water partial pressure at the triple point of said one or more amorphous phosphate salts; wherein said contacting step is performed at a temperature equal to or greater than the temperature at the triple point of said one or more amorphous phosphate salts; and whereby said acrylic acid, metal or ammonium salt of acrylic acids, alkyl esters of acrylic acid, acrylic acid oligomers, or mixtures thereof is produced as a result of said water vapor and said hydroxypropionic acid, metal or ammonium salts of lactic acid, alkyl esters of lactic acid, lactic acid oligomers, cyclic di-esters of lactic acid, lactic acid anhydride, 2-alkoxypropionic acids or their alkyl esters, 2-aryloxypropionic acids or their alkyl esters, 2-acyloxypropionic acids or their alkyl esters, metal or ammonium salts of 3-hydroxypropionic acid, alkyl esters of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-alkoxypropionic acids or their alkyl esters, 3-aryloxypropionic acids or their alkyl esters, 3-acyloxypropionic acids or their alkyl esters, or mixtures thereof being contacted with said dehydration catalyst. a gas mixture comprising: a) hydroxypropionic acid, metal or ammonium salts of lactic acid, alkyl esters of lactic acid, lactic acid oligomers, cyclic di-esters of lactic acid, lactic acid anhydride, 2-alkoxypropionic acids or their alkyl esters, 2-aryloxypropionic acids or their alkyl esters, 2-acyloxypropionic acids or their alkyl esters, metal or ammonium salts of 3-hydroxypropionic acid, alkyl esters of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-alkoxypropionic acids or their alkyl esters, 3-aryloxypropionic acids or their alkyl esters, 3-acyloxypropionic acids or their alkyl esters, or mixtures thereof; and b) water vapor; with a) hydroxypropionic acid, metal or ammonium salts of lactic acid, alkyl esters of lactic acid, lactic acid oligomers, cyclic di-esters of lactic acid, lactic acid anhydride, 2-alkoxypropionic acids or their alkyl esters, 2-aryloxypropionic acids or their alkyl esters, 2-acyloxypropionic acids or their alkyl esters, metal or ammonium salts of 3-hydroxypropionic acid, alkyl esters of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-alkoxypropionic acids or their alkyl esters, 3-aryloxypropionic acids or their alkyl esters, 3-acyloxypropionic acids or their alkyl esters, or mixtures thereof; and b) water vapor; with a dehydration catalyst consisting essentially of one or more amorphous phosphate salts, one or more crystalline phosphate salts, and one or more non-phosphate salts and amorphous silica, wherein the amorphous phosphate salt is KH 2(1-x) PO (4-x), wherein the non-phosphate salt is BaSO 4, and the crystalline phosphate salt is Ba 2 P 2 O 7, wherein x is any real number equal to or greater than 0 and equal to or less than 1; wherein the water partial pressure during said contacting step in said gas mixture is equal to or greater than the water partial pressure at the triple point of said one or more amorphous phosphate salts; wherein said contacting step is performed at a temperature equal to or greater than the temperature at the triple point of said one or more amorphous phosphate salts; and whereby said acrylic acid, metal or ammonium salt of acrylic acids, alkyl esters of acrylic acid, acrylic acid oligomers, or mixtures thereof is produced as a result of said water vapor and said hydroxypropionic acid, metal or ammonium salts of lactic acid, alkyl esters of lactic acid, lactic acid oligomers, cyclic di-esters of lactic acid, lactic acid anhydride, 2-alkoxypropionic acids or their alkyl esters, 2-aryloxypropionic acids or their alkyl esters, 2-acyloxypropionic acids or their alkyl esters, metal or ammonium salts of 3-hydroxypropionic acid, alkyl esters of 3-hydroxypropionic acid, 3-hydroxypropionic acid oligomers, 3-alkoxypropionic acids or their alkyl esters, 3-aryloxypropionic acids or their alkyl esters, 3-acyloxypropionic acids or their alkyl esters, or mixtures thereof being contacted with said dehydration catalyst.