The CO‐catalyzed conversion of H₂S to H₂ + sulfur part 2. The thermal decomposition of COS

Abstract

Research and Technology Branch, Alberta Energy, Edmonton, AB T5K 2G6, CanadaThe pyrolysis of COS has been studied over the temperature range 300 to 750°C using a variety of catalysts. The observed product distribution confirmed that two parallel reaction paths: 2 COS -+ 2 CO + S, (2) and 2 COS -+ CO, + CS, (4) are involved in the decomposition. The decomposition yield increased with rising temperature, accompanied with a shift in selectivity. At temperatures lower than -700°C the disproportionation reaction 4 was predominant, whereas at temperatures higher than 70O0C, reaction 2 was favoured. In the high-temperature region (700 to 750°C) it was possible to achieve full suppression of reaction 4 with added CS,. The pyrolysis of COS was also studied in a reactor packed with quartz chips without catalysts at high temperatures. Between 800 and 9OO"C, up to 99% conversion (with respect to the thermodynamic limit) could be achieved, with the almost complete absence of the disproportionation reaction 4. The results point to the commercial potential in the two-step reaction sequence: 2 H,S + 2 CO t) 2 COS + 2 H, 2 H,S t) 2 H, + S, 2 cos tf 2 co + s, for the economic conversion of hydrogen sulfide to hydrogen and sulfur.On a etudie la pyrolyse du COS dans une gamme de temperatures de 200 a 750°C a I'aide de divers catalyseurs. La distribution de produits observee confirme que deux chemins de reaction parallbles interviennent dans la decomposition, soit 2 COS + 2 CO + S, (2) et 2 COS + CO, + CS, (4). Le rendement de decomposition augmente avec la hausse de la temperature et est accompagne d'un changement de selectivite. A des temperatures inferieures a -700"C, la reaction de dismutation 4 I'emporte, tandis qu'a des temperatures superieures a 700"C, la reaction 2 est favorisee. Dans la region des temperatures superieures a 700"C, la reaction 2 est favorisee. Dans la region des temperatures elevees (700 a 750"C), il a ete possible d'eliminer totalement la reaction 4 par ajout de CS,. La pyrolyse de COS a egalement ete etudiee dans un reacteur garni d'eclats de quartz sans catalyseur a des temperatures elevees. Entre 800 et 900"C, jusqu'a 99% de la conversion (en tenant compte de la limite thennodynamique) a pu itre realisee, avec I'absence presque complete de la reaction de dismutation 4. Les resultats montrent le potentiel economique de la sequence de reaction a deux etapes : 2 H,S + 2 CO c+ 2 COS + 2 H, 2 cos t) 2 co + s, 2 H,S t) 2 H, + s, he hydrogen content of hydrogen sulfide is close to 6% T and if hydrogen sulfide could be converted directly to its elements, sulfur and hydrogen, the hydrogen thereby produced would be industrially significant. In the current, universallyapplied Claus process, only the sulfur is recovered while the hydrogen in the hydrogen sulfide is burnt to water, and essentially wasted. Extensive research has been directed in the recent past to develop alternative technologies for the economic conversion hydrogen sulfide to sulfur and hydrogen. One of such alternative technologies, would be the two-...

A review on hydrogen production from hydrogen sulphide by chemical and photochemical methods

“…Despite reaction ( 46) is considered as the main obstacle limiting or even preventing this scheme from having a real application, this process was revamped and optimized by Cimini et al (1997), who proposed a strategy for the elimination of unwanted by-products reducing the process yield. Faraji et al (1999) observed that an accurate choice of temperature can minimize the side reaction (46) which is damped at T>973 K with a favorable selectivity towards reaction (45). Finally, the main issue came from the studies of Gibson and Wachs (2006), who obtained a satisfactory regeneration of CO by catalytic oxidation:…”

Simultaneous recovery of carbon and sulfur resources from reduction of CO 2 with H 2 S using catalysts

“…Certainly, other routes cannot be excluded, for example, via Eqs. (9) and (10), which may also be very important [6,[14][15][16][17][18][19][20][21].…”

“…But they didn't advance the explanation [19,21]. In order to find out the truth behind the similarity or the divergence of catalytic performance during the reactions between CO 2 and H 2 S, the characterizations on the physico-chemical properties of the catalysts were implemented in the present study.…”

“…Ten products including H 2 , H 2 O, CH 4 , C, CO, COS, CS 2 , S 2 , S 8 and SO 2 all in gas state excepting C (solid) are supposed to present in consideration of the potential of the reactions involved with CO 2 and H 2 S individually or mutually [6,[14][15][16][17][18][19][20][21]. The equilibrium mole yield of every product and the conversions of CO 2 and H 2 S in a Gibbs equilibrium reactor under isothermal and isotonic condition have been calculated according to the principle of Gibbs free energy minimization using Aspen Plus simulation software for chemical engineering processes.…”

Highly Selective Room Temperature Monoreduction of Dinitro‐arenes by Hydrogen Sulfide under Liquid–Liquid Biphasic Catalysis

“…The Claus process is facing the danger of extinction because of many reasons such as (i) underutilization of valuable hydrogen source, (ii) requirement of highly precise air rate control, (iii) the presence of trace sulfur compounds in the spent air, etc. Several reports can be found in the literature for the production of hydrogen and sulfur from H 2 S gas, through thermal , photochemical , electrochemical , and thermochemical processes . Syngas (H 2 , CO), which has been reported to be produced by pyrolysis of acid gases (H 2 S, CO 2 ), can be used as fuel for gas engines .…”