2765. ------. [REITLINGER, O.] Structure of Contact Masses. United States Patent 2,488,560, Nov. 22, 1949; appl. filed Nov. 25, 1946, Serial No. 712,047; 38 claims (Cl. 252-472). Chem. Abs., vol. 44, 1950, p. 1628.

Adhesive property of the catalyst support is increased by a pretreatment in which it is impregnated with hydrophilic material or an intermediate layer of catalytic material is precipitated upon the support. The impregnating ground layer and the surface layer may consist of ferric oxide or one or both layers may be another metal oxide. The catalytic material adheres more firmly and more uniformly than when impregnation alone is used. The efficiency of the catalyst is controlled by the size of the particles of catalytic powder, by the thickness of the outer layer formed by this powder, and by the size of the grains of carrier material. Example: Pumice, 20- to 60- mesh, stood in ferric chloride solution for 24 hr. It is separated and dried at 180° C. The grains are filled into a tube through which gaseous ammonia is passed slowly for 1 hr. Then the grains are brought into concentrated ammonia and left for 24 hr. The aqueous ammonia is decanted and the grains washed until red litmus remains red and the H₂O suspended ferric hydroxide precipitate has been removed. The grains are dried at 200° C. and filled into a reactor tube and subjected, at 490° C. for 2 hr., to action of a gas stream 10 parts air and 4 parts by volume of HCI, space velocity 3.25 per min. After cooling, the impregnated grains are shaken with ferric oxide in ratio 60 parts grains and 40 parts ferric oxide, 95% 325-mesh. The powder is gradually added to the grains in a humid atmosphere. The grains absorb some H₂O and hold the ferric oxide firmly upon their surface. 145.5 gm. of catalyst contained 58% impregnated pumice grains, 39% ferric oxide in powder form and 3% H₂O. 5 United States patents cited.