Catalyst mass for heterogeneous catalysis

A catalyst mass for the heterogeneous contact catalyst of reactions, especially the flameless combustion of hydrocarbons, which consists essentially of an iron-free silico-alumina fiber support with proportions of silica and alumina respectively between 40% and 60% by weight and substantially free from impurities, and an iron-free catalyzer consisting essentially of at least one element in elemental form and at least one oxide of an element selected from the groups III, VI, VIIIb, VIIIc and the rare-earth elements of the Periodic Table, the weight ratio of the element, in elemental form, to the support being substantially 0.001 to 0.02 and the weight ratio of the oxide to the support being substantially 0.01 to 0.2, said support having a density between 0.04 and 0.1, a specific surface between 0.5 and 1 m.sup.2 /g, and a thermal stability sufficient to preclude modification of the surface and texture upon prolonged exposure to temperatures up to 900.degree. C.