Abstract: Process for preparing one or more complexing agents selected from methylglycinediacetic acid, glutamic acid diacetic acid and salts thereof Process for preparing one or more complexing agents selected from methylglycinediacetic acid, glutamic acid diacetic acid and salts thereof by catalytic dehydrogenation of N,N-bis(2-hydroxyethyl)alanine and/or N,N-bis(2-hydroxyethyl)glutamic acid and/or salts thereof in the presence of alkali metal hydroxide, where a catalyst comprising copper and zirconium dioxide is used, the activation of which is a reduction, wherein the precursor of the catalyst in question has a degree of crystallization K, defined as K = I K · 100 I K + I A , in the range from 0 to 50%.