Chemistry of inorganic compounds – Sulfur or compound thereof – Elemental sulfur
Patent
1998-02-13
2000-02-15
Straub, Gary P.
Chemistry of inorganic compounds
Sulfur or compound thereof
Elemental sulfur
4235731, 423576, 502217, 502244, 502254, 502260, C01B 1700, C01B 1702, B01J 27053, B01J 2108
Patent
active
060249331
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the use of catalysts for the treatment of gases, in particular industrial gaseous effluents, containing sulphur compounds, in order to catalytically convert these compounds into readily removable products.
The invention more particularly relates to the use of catalysts for the direct oxidation of hydrogen sulphide into sulphur and/or into sulphates.
The desulphurization of gases containing low concentrations of hydrogen sulphide has undergone considerable expansion. This treatment is applied in various fields: originating from Claus units, also known as "tail gases", are increasingly subjected to an additional treatment, known as a tail gas treatment.
The residual compounds in these tail gases (sulphur vapour, sulphur dioxide, organosulphur compounds: CS.sub.2, COS, etc.) may be eliminated by hydrogenation to hydrogen sulphide, after which this hydrogen sulphide is converted into elemental sulphur and/or sulphates.
It may also be envisaged at the outlet of the final Claus reactor to use a deliberate shift of the H.sub.2 S/SO.sub.2 ratio and then to pass the effluent over a catalyst which allows the remaining SO.sub.2 to be converted into sulphur via the Claus reaction (2H.sub.2 S+SO.sub.2 .fwdarw.3/x S.sub.x +2H.sub.2 O). Next, a final step of direct oxidation of the H.sub.2 S into sulphur and/or sulphates completes the treatment. naturally having a low concentration of hydrogen sulphide are also treated. In certain cases, a desulphurization based on a Claus process proves to be difficult, if not impossible, and a process of direct conversion of the hydrogen sulphide into sulphur and/or sulphates is preferable.
The present invention relates to processes using the final reaction for the conversion of hydrogen sulphide into elemental sulphur and/or into sulphates in the presence of oxygen, and in particular at a temperature below the dew point of sulphur, i.e. below 200.degree. C. The advantage of working at such a temperature is, on the one hand, to be able to recover the sulphur in liquid or solid form in the porosity of the catalyst, and, on the other hand, to shift the thermodynamic equilibrium in the direction favourable to the reaction for the formation of sulphur.
However, the fault with this type of process is that, concomitantly with the formation of the elemental sulphur, sulphur dioxide is often produced in parallel and is not retained on the catalyst, leading to a loss of yield for the purification of the gases.
Thus, the catalysts of the prior art do not make it possible to ensure the best possible conversion of the H.sub.2 S with maximum selectivities with respect to sulphur and/or sulphates and a minimum selectivity with respect to SO.sub.2.
One aim of the present invention is to provide a catalyst which makes it possible, during the reaction for the direct oxidation of sulphur compounds at low temperature (T<200.degree. C.), to increase the conversion of H.sub.2 S while at the same time minimizing the conversion into SO.sub.2.
In particular, one aim of the present invention is to provide a catalyst which makes it possible to obtain, during the reaction defined above, a degree of conversion of H.sub.2 S close to 100% and a yield of SO.sub.2 close to 0%.
With this aim, the invention relates to a process for the direct oxidation of sulphur compounds into elemental sulphur and/or into sulphates at a temperature below 200.degree. C., in which a supported catalyst whose catalytically active phase comprises copper is used, the copper element being present in a content of at least 2% by weight relative to the catalyst and of at least 15% by weight relative to the sum of the active elements of the catalytically active phase.
Other details and advantages of the invention will emerge more clearly on reading the description which follows.
The invention thus relates to a process for the direct oxidation of sulphur compounds into elemental sulphur and/or into sulphates at a temperature below 200.degree. C., in which a supported catalyst whose catalytically active phase c
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Legendre Olivier
Nedez Christophe
Nguyen Cam N.
Rhone-Poulenc Chimie
Straub Gary P.
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