Abstract: A catalyst for reducing the nitrous oxide content in gas, which operates at relatively low temperatures, the activity of which is relatively insensitive to the presence of water vapor and which is highly resistant to hydrothermal degradation, is prepared from ferrierite exchanged with iron. Application to the treatment of gases with a low N2O content, such as gases resulting from plants for the manufacture of nitric acid, and of gases with a high N2O content, which are emitted during oxidations of organic compounds by nitric acid.

Abstract: The invention concerns a method for purifying flue gases before they are released into the atmosphere of their nitrogen oxides N2O and NOx by reaction with ammonia by causing them to circulate at temperatures between 200 and 600° C. on a catalyst based on beta-zeolite loaded with iron. The invention is particularly useful for treating tail gases from factories producing nitric acid.

Abstract: A catalyst for reducing the nitrous oxide content in gas, which operates at relatively low temperatures, the activity of which is relatively insensitive to the presence of water vapor and which is highly resistant to hydrothermal degradation, is prepared from ferrierite exchanged with iron. Application to the treatment of gases with a low N2O content, such as gases resulting from plants for the manufacture of nitric acid, and of gases with a high N2O content, which are emitted during oxidations of organic compounds by nitric acid.

Abstract: The invention concerns a method for purifying flue gases before they are released into the atmosphere of their nitrogen oxides N2O and NOx by reaction with ammonia by causing them to circulate at temperatures between 200 and 600° C. on a catalyst based on beta-zeolite loaded with iron. The invention is particularly useful for treating tail gases from factories producing nitric acid.

Abstract: Zeolites partially exchanged with copper, in particular faujasites, in which the copper does not largely occupy the small cages (for example the sodalite cages of the faujasites), are used as non-nitrogen-protoxide-generating SCR catalysts. Particular attention is drawn to certain mixed rare-earth/copper zeolites. The selectivity of the reduction of NOx to N2 is correlated with the TPR diagram of the catalysts.

Abstract: The sludge filtration device comprises: a filter (1) placed over an approximately horizontal box (4), this filter (1) constituting, in its filtration position, the bottom of a filter chamber (8) of essentially vertical axis; a piston (10) suitable for closing the filter chamber in the top part; means (3, 11) for causing relative movement between the box (4) provided with the filter (1) and the piston (10) so that a liquid filtrate flows downwards through the filter (1) and so that a cake of solid matter remains on the filter (1) at the end of the operation; and a scraper device (31) provided for removing this cake. The piston is made in the form of a filter piston (10) so that a liquid effluent passes through the filter piston (10) as the volume of the filter chamber (8) is being decreased, and a suction pumping means (P) is provided for removing the effluent above the filter piston (10).

Abstract: The method relates to the production of phospho-nitrogenous products soluble in neutral ammonium citrate and wherein free urea does not remain in significant amount in such products. Most of the free urea is involved in a ureic combination of calcium sulphate. Tricalcic phosphate is reacted with a reactant obtained by mixing sulfuric acid and urea. The process is particularly useful for the manufacture of fertilizers.