Abstract: An improved hydroformylation process for preparing aldehydes by reacting olefins with synthesis gas (H.sub.2 and CO) under heating and pressure is disclosed. The hydroformylation is carried out in the presence of a platinum catalyst, and assistant composed of a halide of a metal of the group IVb of the Periodic Table and a reaction promotor composed of a specific bidentate ligand of the formula R.sub.2 X-Z-Y-Z-X-R'.sub.2. In this reaction, the platinum catalyst exerts a high activity, and an aldehyde mixture containing a linear isomer at a very high ratio of content is obtained as a product.

Abstract: In catalytic hydroformylation of an olefin with hydrogen and carbon monoxide, when a platinum-phosphine complex is used as a catalyst and a compound of tin and an element of the group VIB of the Periodic Table is used as a promotor, condensation of the formed aldehyde as a side reaction is controlled and the intended aldehyde can be obtained in a high yield.

Abstract: An improved hydroformylation process for preparing aldehydes by reacting olefins with synthesis gas (H.sub.2 and CO) under heating and pressure is disclosed. The hydroformylation is carried out in the presence of a platinum catalyst, and assitant composed of a halide of a metal of the group IVb of the Periodic Table and a reaction promotor composed of a specific bidentate ligand of the formula R.sub.2 X--Z--Y--Z--X--R'.sub.2. In this reaction, the platinum catalyst exerts a high activity, and an aldehyde mixture containing a linear isomer at a very high ratio of content is obtained as a product.