Abstract: Propylene in admixture with molecular oxygen and steam is subjected to a two-step, vapor-phase, catalytic oxidation to convert into acrolein and then into acrylic acid. At least the first-step reaction is conducted in tubes of an apparatus of a shell-and-tube heat-exchanger type structure, and the reaction product of the first-step reaction is quenched before it is subjected to the second-step reaction. Reaction conditions in both the steps are specified.

Abstract: Acrolein and acrylic acid are produced by vapor-phase catalytic oxidation of propylene in a multi-tubular, fixed-bed reaction vessel with the use of a composite oxide catalyst represented by the formula Mo.sub.a Bi.sub.b Fe.sub.c A.sub.d B.sub.e C.sub.f D.sub.g Si.sub.h O.sub.x, wherein A, B, C, and D represent components selectable from respective groups of elements, and the subscripts a through h and x are specific numbers of atoms of respective elements and groups of elements. This catalyst is adapted and packed in each reaction tube in a manner such that its activity is controlled to increase from the inlet toward the outlet of the tube.

Abstract: In the production of acrylic acid by a two-stage, vapor-phase catalytic oxidation of propylene, a composite oxide catalyst expressed by the formula Mo.sub.a Bi.sub.b Ni.sub.c Co.sub.d Fe.sub.e Na.sub.f Mn.sub.g B.sub.h K.sub.i Si.sub.j O.sub.x is used in the first-stage reaction, which is carried out under specific reaction and operational conditions, and the second-stage reaction is carried under specific reaction and operational conditions while oxygen is supplied by a specific mode.

Abstract: In the production of a composite oxide catalyst containing at least Mo tegether with V and (or) Nb, the catalyst precursor is subjected to a thermal decomposition step in which: (1) the precursor is heated in a heat-exchanger type apparatus in which a first space accommodating the precursor and a second space through which a heating fluid flows are partitioned and separated from each other, the heating of the precursor being accomplished through the partitioning; (2) the thermal decomposition is carried out as an atmosphere gas of an oxygen concentration of 0.05 to 5 percent is caused to flow through the first space; and (3) the maximum temperature reached in the thermal decomposition is 300.degree. to 550.degree. C.

Abstract: An .alpha.,.beta.-unsaturated aliphatic carboxylic acid can be prepared in a high yield by catalytic vapor phase oxidation of the corresponding .alpha.,.beta.-unsaturated aldehyde in the presence of a catalyst represented by the following formula:Sb.sub.a Ni.sub.b Mo.sub.c V.sub.d W.sub.e Nb.sub.f Cu.sub.g O.sub.hwherein, a = 100, b = 15 - 150, c = 10 - 500, d = 5 - 150, e = 0 - 100, f = 0 - 100, g = 0 - 50 (g .noteq. 0 when f = 0), and h .ltoreq. 2950, respectively in atomic ratio. The catalyst has a long life time and gives a high yield even when it is contacted with a crude .alpha.,.beta.-unsaturated aldehyde gas supplied by a catalytic vapor phase oxidation of the corresponding unsaturated hydrocarbon.

Abstract: A process for the production of unsaturated acids by catalytic oxidation of the corresponding unsaturated aldehydes in the presence of molybdenum-vanadium-iron based catalysts at a temperature of from 200.degree. C to 400.degree. C.