Stannous acetate → Tin(IV) acetate

Catalyst preparation was conducted as follows. That is, 1.5 g of commercial tin (II) acetate (a product of Kanto Chemical Company, Inc.) was dissolved in 150 ml of acetic acid with heating. The solution was cooled to room temperature to obtain a solution of tin acetate in acetic acid. 5 g of a commercial silicon dioxide powder having an average particle diameter of 25 μm (a product of Mizusawa Industrial Chemicals, Ltd.) was weighed in a 500-ml beaker, after which 200 ml of water was added to suspend the silicon dioxide powder therein. To the suspension being stirred were slowly added dropwise the above-prepared solution of tin acetate in acetic acid and 25 ml of an aqueous palladium nitrate solution containing 1 g/l of palladium, simultaneously. After the completion of the dropwise addition, the mixture was heated to 80° C. with stirring, to evaporate and remove the acetic acid and water in the mixture. The residue was dried to obtain a powder. The powder was calcined in an air stream at 500° C. for 1 hours and then reduced in a hydrogen stream at 250° C. for 1 hour to obtain a catalyst in which palladium and tin were supported in amounts of 0.5% by weight and 15% by weight, respectively, based on the weight of the silicon dioxide used.