Method for synthesizing hydrocyanic acid from formamide-catalyst

The invention relates to a method for producing hydrocyanic acid by the thermolysis of gaseous formamide in a reactor in the presence of a catalyst, wherein a) the catalyst (i) is an aluminum oxide catalyst, containing - 90 to 100 wt%, preferably 99 to 100 wt%, of aluminum oxide as component A, - 0 to 10 wt%, preferably 0 to 1 wt%, of silicon dioxide as component B, and - 0 to at most 0.1 wt% of iron or compounds containing iron as component C, wherein the total sum of components A, B, and C is 100 wt%, and (ii) has a BET surface area, measured as per DIN ISO 9277 : 2003-05, of 1 m2/g, and (iii) is tempered at temperatures of 1400 DEG C for 1 to 30 h, preferably >= 1500 DEG C for 1 to 30 h, especially preferably at 1500 DEG C to 1800 DEG C for 2 to 10 h, and b) the reactor has an inner surface that is inert with respect to the thermolysis of formamide; and use of the catalyst in a method for producing hydrocyanic acid by the thermolysis of gaseous formamide in a reactor that has an inner surface that is inert with respect to the thermolysis of formamide.