The invention relates to a method of preparing a calcium boron phosphate catalyst, comprising the steps of reacting calcium salts with phosphoric acid salts in aqueous ammonia, separating the resulting precipitate from the reaction mixture thus obtained, suitably shaping said precipitate, drying it, and heat treating at an elevated temperature in the presence of steam or steam with an inert gas, mixed with at least one of the components selected from the group consisting of boric acid and, a mixture of boric and phosphoric acids, the molar ratio of boric to phosphoric acids being between 1.0:1 and 10:1.The reaction of calcium salts with phosphoric acid salts in aqueous ammonia is effected with the starting reactants taken in the molar ratio of 1.5:1 if no phosphoric acid treatment is used, or with the starting reactants in a molar ratio of between 1.5:1 to 5.0:1 if the reaction mixture is treated with a phosphoric acid solution to pH of from 5.0 to 7.0.