US 4,374,819 A · Catalytic process for removing toxic gases from gas streams

Abstract

A multi-stage process for reducing the content of sulfur-containing gases--notably hydrogen sulfide, sulfur dioxide, carbonyl sulfide and carbon disulfide--in waste gas streams is provided. In the first stage, the gas stream is passed through a reaction zone at a temperature between about 150.degree. and 350.degree. C. in the presence of a pretreated novel catalyst of the formula xLn.sub.2 O.sub.3.yT.sub.2 O.sub.3 in which Ln is yttrium or a rare earth element and T is cobalt, iron or nickel, and each of x and y is independently a number from 0 to 3, said catalyst being substantially non-crystalline and having a surface area of from about 10 m.sup.2 /g to about 40 m.sup.2 /g. The preferred catalyst is one in which Ln is lanthanum, T is cobalt, and x and y range from 1 to 3, including non-integers. The first stage yields a product stream having a reduced content of sulfur-containing gases, including specifically, substantial reduction of carbonyl sulfide and virtual elimination of carbon disulfide. An intermediate stage is a Claus reaction, which may take place in one or more reaction zones, at temperatures less than about 130.degree. C., in the presence of known catalysts such as bauxite, alumina or cobalt molybdates. The final stage is the air oxidation of hydrogen sulfide at a temperature between about 150.degree. and 300.degree. C. in the presence of a catalyst usable in the first stage.

Claims24

Dependent claims

A multi-stage process for reducing the content of hydrogen sulfide, sulfur dioxide, carbonyl sulfide and disulfide in a gas stream which comprises

(a) passing said gas stream through a first reaction stage at a temperature between about 150.degree. and about 350.degree. C., said stage containing a pretreated catalyst of the formula
xLn.sub.2 O.sub.3.yT.sub.2 O.sub.3
in which Ln is yttrium or a rare earth element and T is selected from the group consisting of cobalt, iron and nickel and each of x and y independently is a number from 0 to 3, said catalyst being substantially non-crystalline and having a surface area of from about 10 m.sup.2 /g to about 40 m.sup.2 /g and having been prepared at a temperature no higher than 700.degree. C, to obtain elemental sulfur and a first product stream having reduced content of sulfur containing gases,
(b) passing the first product stream through one or more intermediate catalytic reaction stages in which the Claus reaction occurs, to obtain further elemental sulfur and a second product stream having further reduced content of sulfur containing gases, and
(c) passing the second product stream through a final reaction stage at a temperature between about 150.degree. and 300.degree. C., said final stage containing a catalyst usable in the first reaction stage, in the presence of air to obtain elemental sulfur and still further reduced content of the sulfur containing gases, which gases can be recyled to an earlier stage.

2 more elements

A multi-stage process for reducing the content of hydrogen sulfide, sulfur dioxide, carbonyl sulfide and carbon disulfide in a gas stream, which comprises

(a) passing said gas stream through a first reaction stage in which (i) at least a portion of the hydrogen sulfide reacts with at least a portion of the sulfur dioxide to form elemental sulfur and water, (ii) carbonyl sulfide reacts with sulfur dioxide to form elemental sulfur and carbon dioxide, (iii) carbonyl sulfide reacts with water to form hydrogen sulfide and carbon dioxide, (iv) carbon disulfide reacts with sulfur dioxide to form elemental sulfur and carbon dioxide and (v) carbonyl sulfide reacts with water to form hydrogen sulfide and carbon dioxide, at a temperature of between about 150.degree. and 350.degree. C. in the presence of a pretreated catalyst of the formula
xLn.sub.2 O.sub.3.yT.sub.2 O.sub.3
in which Ln is yttrium or a rare earth element, T is a transition element selected from the group consisting of cobalt, iron and nickel, and each of x and y independently is a number from 0 to 3, said catalyst being substantially non-crystalline and having a surface area of from about 10 m.sup.2 /g to about 40 m.sup.2 /g and having been prepared at a temperature no higher than 700.degree. C., the elemental sulfur formed and obtaining a first product stream comprising gases selected from the group consisting of hydrogen sulfide and sulfur dioxide and a possible minor amount of carbonyl sulfide,
(b) passing the product stream of said first stage through one or more intermediate reaction stages in which the hydrogen sulfide and sulfur dioxide catalytically react in the Claus reaction to form elemental sulfur and water, removing the elemental sulfur and obtaining a second product stream which may contain carbonyl sulfide and hydrogen sulfide,
(c) passing the product stream of the intermediate stage through a final reaction stage in which hydrogen sulfide and carbonyl sulfide are each reacted with oxygen to form elemental sulfur, sulfur dioxide and/or carbon dioxide at a temperature between about 150.degree. and 300.degree. C., in presence of a catalyst usable in the first stage, removing any elemental sulfur formed and recycling any sulfur dioxide formed to the first or second stage.

2 more elements

Dependencies are inferred from the claim text.

Catalytic process for removing toxic gases from gas streams

Life of this patent

Catalytic process for removing toxic gases from gas streams

Life of this patent

Abstract

Claims24