Abstract: The present invention relates to a process for the preparation of free-flowing particles comprising or consisting of an N-guanylamino acid, wherein the process comprises the steps of a) providing an N-guanylamino acid comprising solution or suspension b) shifting the pH of the solution or suspension provided in step a) to a pH lower than the pKa value of the N-guanylamino acid, and c) shifting the pH of the solution or suspension obtained in step b) to a pH larger than the pKa value of the N-guanylamino acid and lower than the pKb value of the N-guanylamino acid, wherein the step c) further comprises the precipitation or crystallization of the particles comprising or consisting of the N-guanylamino acid, wherein the pH in each of the steps b) and c) is measured by means of a pH electrode.

Abstract: Process for the delignification and bleaching of pulp, comprising a first bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture; subsequent to the first bleaching stage, a second bleaching stage with hydrogen peroxide in an alkaline aqueous mixture; and, subsequent to the second bleaching stage, a third bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture.

Abstract: Process for delignifying and bleaching pulp Process for the delignification and bleaching of pulp, comprising a first bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture; subsequent to the first bleaching stage, a second bleaching stage with hydrogen peroxide in an alkaline aqueous mixture; and, subsequent to the second bleaching stage, a third bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture.

Abstract: In a delignification of pulp with hydrogen peroxide catalyzed by molybdate, molybdate can be recovered by contacting the molybdate-containing aqueous solution at a pH in the range from 2 to 7 with a carrier material comprising a sheet silicate been ion-exchanged with a quaternary ammonium salt and subsequent flotation without a surfactant having to be added for flotation.

Abstract: An improved process for bleaching pulps is disclosed in which the unbleached pulp is subject to flotation before bleaching and, if necessary, the circulating water is also purified of interfering compounds by flotation.