Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Halogenous component
Patent
1997-02-25
1999-03-30
Nguyen, Ngoc-Yen
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Halogenous component
95132, B01D 5334
Patent
active
058884653
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to German Application No. P 44 33 246.7 filed Sep. 19, 1994, and International Application No. PCT/EP95/03497 filed Sep. 6, 1995, published as WO96/09245 Mar. 28, 1996.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Most of the known processes for removing hydrogen halides from gas mixtures are based on the use of solutions or suspensions of chemicals which bind the hydrogen halides by the absorption principle. In this case, principally solutions and suspensions of alkali metal compounds or alkaline earth metal compounds such as oxides, hydroxides or carbonates are used.
In many absorption processes used industrially, contact of generally hot gases with a liquid absorbent leads to a marked decrease in the gas temperature. Because of the highly corrosive character of many water-containing gas mixtures if the dew point is undershot and the difficult removal of cold gases via a stack, the gas mixture must often be reheated after the absorption, which markedly impairs the energy balance of the process.
In addition, many alkali metal compounds and alkaline earth metal compounds, in particular sodium hydroxide and potassium hydroxide, are extremely aggressive substances, so that safety precautions must be taken in the operation and maintenance of the apparatus for treating the gas mixtures.
Adsorption processes do not have these disadvantages since the temperature is not decreased and thus the dew point is not undershot, for which reason reheating the gas mixture after removal of the hydrogen halides is not necessary. Furthermore, aqueous systems which contain aggressive substances are bypassed in adsorption processes.
2. Description of the Related Art
U.S. Pat. No. 3,278,266 describes the adsorption of hydrogen halide from vapour mixtures of organic compounds. The adsorbent comprises an oxidic compound of the second main group of the Periodic Table of the Elements which is applied to a support and may be regenerated by desorption.
Surprisingly, it has now been found that such an adsorbent offers the possibility of selectively adsorbing hydrogen halide from a sulfur-dioxide-containing gas and thus of separating hydrogen halide from sulfur dioxide.
OBJECT OF THE INVENTION
The object of the invention is to selectively separate hydrogen halides from sulfur-dioxide-containing gases, thus, separating hydrogen halide from sulfur dioxide at a constant temperature by using an adsorption process according to the present invention.
SUMMARY OF THE INVENTION
The invention thus relates to the use of an adsorbent made of a porous ceramic support material which is impregnated with an alkaline earth metal salt solution, in which, after evaporation of the solvent, the alkaline earth metal salt is pyrolysed at 200.degree. to 800.degree. C. to give alkaline earth metal oxide .x H.sub.2 O, where x is a number from 0 to 1, for the selective separation of hydrogen halides from sulfur-dioxide-containing gases.
DETAILED DESCRIPTION OF THE INVENTION
The invention is described in detail below, in particular in its preferred embodiments.
A solution of alkaline earth metal salt is introduced into the pores of the ceramic support material. The ceramic support material can be produced on a basis of SiO.sub.2 or, in particular, Al.sub.2 O.sub.3, or else using aluminum silicates, zeolytes or other ceramic starting materials. The alkaline earth metal salts which serve are salts, individually or in a mixture, which form an activated oxide on heating to 200.degree. to 800.degree. C. Magnesium salt solutions are preferably used, e.g. magnesium carbonate, magnesium chloride, magnesium nitrate or, in particular, magnesium acetate. The supports are dried, then the alkaline earth metal salt is converted into an activated alkaline earth metal oxide at the temperature necessary for pyrolysis in the pores. A pyrolysis temperature as low as possible is desirable, since this increases the adsorption activity of the adsorbent produced.
The invention now offers the po
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Luft Gerhard
Merten Heinrich
Rappold Ulrich
Schick Wolfgang
Schmid Jorg
Hoechst Aktiengesellschaft
Nguyen Ngoc-Yen
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