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KR-20260065814-A - Method for processing tail gas streams

KR20260065814AKR 20260065814 AKR20260065814 AKR 20260065814AKR-20260065814-A

Abstract

A method for treating a tail gas stream containing one or more sulfur compounds and/or carbon monoxide under hydrolysis conditions in the presence of water and hydrogen in a reactor system comprising one or more reactors, wherein the method is carried out in the presence of a catalyst system comprising a first catalyst composition and a second catalyst composition, wherein the first catalyst composition and the second catalyst composition each comprise a combination of a cobalt compound and/or a nickel compound with a molybdenum compound and an inorganic oxide selected from alumina and/or titania, wherein the first catalyst composition has higher activity for the removal of carbon monoxide from the tail gas stream and/or higher activity for the removal of carbonyl sulfide (COS) and/or carbon disulfide ( CS₂ ) compared to the second catalyst composition under the same conditions, and wherein the first catalyst composition and the second catalyst composition are arranged such that at least a portion of the first catalyst composition is located upstream of the second catalyst composition in the reactor system.

Inventors

  • 크루거, 칼 마빈
  • 위벨트, 요하네스
  • 허프마스터, 마이클 아서

Assignees

  • 쉘 인터내셔날 리써취 마트샤피지 비.브이.

Dates

Publication Date
20260511
Application Date
20240827
Priority Date
20230907

Claims (20)

  1. A method for treating a tail gas stream comprising one or more sulfur compounds and/or carbon monoxide under hydrolysis conditions in the presence of water and hydrogen in a reactor system comprising one or more reactors, The above method is performed in the presence of a catalyst system comprising a first catalyst composition and a second catalyst composition, and The first catalyst composition and the second catalyst composition each comprise a cobalt compound and/or a nickel compound in combination with a molybdenum compound and an inorganic oxide selected from alumina and/or titania, and the first catalyst composition has higher activity for the removal of carbon monoxide from the tail gas stream and/or higher activity for the removal of carbonyl sulfide (COS) and/or higher activity for the removal of carbon disulfide ( CS₂ ) compared to the second catalyst composition under the same conditions, A method in which a first catalyst composition and a second catalyst composition are arranged such that at least a portion of the first catalyst composition is located upstream of the second catalyst composition in a reactor system.
  2. A method according to claim 1, wherein the catalyst system comprises a first catalyst composition and a second catalyst composition.
  3. A method according to claim 1 or 2, wherein the entire first catalyst composition is located upstream of the second catalyst composition in a reactor system.
  4. A method according to any one of claims 1 to 3, wherein the first catalyst composition has an individual active level X1 for the removal of carbon monoxide, an individual active level Y1 for the removal of carbonyl sulfide (COS), and an individual active level Z1 for the removal of carbon disulfide ( CS2 ) when operated under a given series of operating conditions, and the second catalyst composition has an individual active level X2 for the removal of carbon monoxide, an individual active level Y2 for the removal of carbonyl sulfide, and an individual active level Z2 for the removal of carbon disulfide under the same series of operating conditions, wherein X1 > X2 and/or Y1 > Y2 and/or Z1 > Z2.
  5. A method according to any one of claims 1 to 4, wherein the first catalyst composition and the second catalyst composition exist as a stacked catalyst layer arrangement in the same reactor within the reactor system.
  6. A method according to any one of claims 1 to 5, wherein the first catalyst composition and the second catalyst composition are present in a sequential arrangement in a catalyst layer in a separate reactor within a reactor system.
  7. A method according to any one of claims 1 to 6, wherein the catalyst volume ratio of the first catalyst composition to the second catalyst composition in the catalyst system is in the range of 5:95 to 95:5.
  8. A method according to any one of claims 1 to 7, wherein the first composition and the second composition comprise, based on the total weight of the metal as an oxide regardless of the actual form of the metal and the catalyst composition, an amount of cobalt compound and/or nickel compound of at least 0.5 weight%, preferably in the range of 0.5 to 8 weight%, and an amount of molybdenum compound of at least 3 weight%, preferably in the range of 3 to 22 weight%.
  9. A method according to any one of claims 1 to 8, wherein the first catalyst composition contains at least 2.0 weight%, preferably at least 2.7 weight%, of cobalt and/or nickel and at least 7.4 weight% of molybdenum based on the total weight of the metal as an oxide and the catalyst composition, regardless of the actual form of the metal.
  10. A method according to any one of claims 1 to 9, wherein the second catalyst composition contains an amount of cobalt and/or nickel in the range of 1 to 3.75 weight% and an amount of molybdenum in the range of 3 to 9.5 weight% based on the total weight of the metal as an oxide and the catalyst composition, regardless of the actual form of the metal.
  11. A method according to any one of claims 1 to 10, wherein the inorganic oxide is preferably present in each of the first catalyst composition and the second catalyst composition in an amount ranging from 60 to 95 weight percent based on the total weight of the catalyst composition.
  12. A method according to any one of claims 1 to 11, wherein the first catalyst composition comprises a cobalt compound in combination with a molybdenum compound and an inorganic oxide selected from alumina and/or titania, and the second catalyst composition comprises a cobalt compound in combination with a molybdenum compound and an inorganic oxide selected from alumina and/or titania.
  13. In any one of paragraphs 1 through 12, A method comprising a first catalyst composition comprising a combination of a cobalt compound with a molybdenum compound and an inorganic oxide selected from alumina and/or titania, wherein the first catalyst composition is prepared by a method comprising the steps of co-mulling components including cobalt and molybdenum metals and alumina and/or titania precursors, and drying and calcining the co-mulled mixture.
  14. A method according to claim 13, wherein the first catalyst composition contains at least 2.0 weight%, preferably at least 2.7 weight%, of cobalt and at least 7.4 weight% of molybdenum, each weight% being based on the total weight of the metal as an oxide and the catalyst composition, regardless of the actual form of the metal.
  15. A method according to any one of claims 1 to 14, wherein the first catalyst composition comprises a cobalt compound in combination with a molybdenum compound and an inorganic oxide selected from alumina and/or titania, and the first catalyst composition comprises both molybdenum and cobalt metals in a so-called underbedded form and both molybdenum and cobalt as overlaid metals.
  16. A method according to claim 15, wherein the first catalyst composition comprises a calcined co-mixed mixture of an inorganic oxide selected from alumina and/or titania, a first molybdenum compound, and a first cobalt compound, and the calcined co-mixed mixture is impregnated with a second molybdenum compound and a second cobalt compound to provide underbed molybdenum, underbed cobalt, overlay molybdenum, and overlay cobalt.
  17. A method according to claim 15 or 16, wherein the first catalyst composition has a molybdenum ratio of the underbed molybdenum content to the total molybdenum content in the range of 1:5 to 4:5 and a cobalt ratio of the underbed cobalt content to the total cobalt content in the range of 1:5 to 4:5.
  18. A method according to any one of claims 15 to 17, wherein the first catalyst composition has a total metal weight % ratio of total molybdenum content to total cobalt content in the range of 1.5:1 to 8:1.
  19. A method according to claim 13 or 14, wherein the first catalyst composition comprises a formed aggregate of a co-mixed mixture comprising pseudoboehmite, a cobalt compound, and a molybdenum compound, and said formed aggregate is calcined to provide said catalyst composition comprising gamma-alumina.
  20. A method according to claim 19, wherein the first catalyst composition has a dual-mode pore structure in which a first major portion of the total pore volume is present in pores having a diameter in the range of 50 Å to 150 Å and a minor portion of the total pore volume is present in pores having a diameter in the range of 1,000 Å to 10,000 Å, optionally, less than 6% of the total pore volume of the catalyst may be contained within pores having a pore diameter greater than 10,000 Å, and the pore diameter is determined by the surface area through mercury porosimetry at a contact angle of 140 degrees.

Description

Method for processing tail gas streams The present invention relates to a method for treating a tail gas stream comprising one or more sulfur compounds and/or carbon monoxide. In the well-known Claus process, an acidic gas containing a significant amount of hydrogen sulfide ( H₂S ) is combusted in a thermal stage to oxidize some of the H₂S to sulfur dioxide ( SO₂ ). This combustion is controlled to provide a process gas stream containing H₂S and SO₂ in an approximate molar ratio (2:1) of 2 moles of H₂S to 1 mole of SO₂. This process gas stream is passed through a catalytic stage that provides for the reaction of H₂S and SO₂ in the presence of an alumina catalyst according to the Claus reaction , producing elemental sulfur and water. The sulfur is then condensed from the Claus reaction gas to produce a Claustail gas stream. Claustail gas streams typically contain low concentrations of H₂S and other sulfur compounds, such as SO₂ , carbon disulfide ( CS₂ ), carbonyl sulfide (COS), methyl mercaptan ( CH₃SH ), and elemental sulfur ( S₆x ). For these tail gas streams to be combusted or otherwise disposed of, they must be further treated to remove most of the sulfur. This provides a treated gas stream having a sufficiently low sulfur content to be combusted or released into the atmosphere. One method of treating tail gas is to pass it through a reduction reactor. The reduction reactor catalytically reduces sulfur compounds (i.e., SO₂ , CS₂ , COS, and S) contained in the tail gas to H₂S , producing a treated gas stream with a reduced concentration of sulfur compounds. This treated gas stream can be further treated to remove H₂S , for example, by passing it through an absorption unit that removes H₂S . This is typically done by contacting the treated gas stream with an H₂S removal absorbent. Shell’s SCOT (Shell Claus Off-gas Treating Process) was developed to treat tail gas streams by a combination of catalytic hydrogenation and hydrolysis reactions. Accordingly, U.S. Patent No. 3554689 (Bloembergen et al.) describes the removal of carbonyl sulfides, i.e., COS, from a gas stream by catalytic hydrolysis to H₂S . This patent discloses a method for removing COS from combustion gases that also contain oxygen by first contacting the gas with an active hydrogenation catalyst for oxygen conversion, and then contacting the resulting substantially oxygen-free gas with a COS conversion catalyst for converting COS to H₂S . Subsequently, H₂S can be removed by absorption. The conversion of COS can occur at low temperatures below 150°C. The COS conversion catalyst comprises alumina having a specific surface area of more than 50 m² /g and may contain one or more Group VI and/or Group VIII metal oxides. Further embodiments of the COS conversion catalyst include having a predetermined amount of alkali metal phosphate present therein. One requirement of the method of U.S. Patent No. 3554689 is that the combustion gas must first undergo a catalytic oxygen removal step so that the gas treated to remove COS by catalytic hydrolysis is substantially oxygen-free. U.S. Patent No. 4668491 (Wimmer et al.) discloses a method and a catalyst for the selective catalytic hydrolysis of sulfur compounds COS and/or CS2 present in carbon monoxide-containing process gases. The hydrolysis catalyst disclosed in U.S. Patent No. 4668491 is an alkalized chromium oxide-aluminum oxide catalyst, comprising chromium oxide and an alkali metal compound supported on an alumina oxide carrier, wherein gamma alumina is a preferred form of aluminum oxide. The carbon monoxide content of the process gas is substantial and is passed over the hydrolysis catalyst at a temperature in the range of 100°C to 350°C. The alkalized chromium oxide-aluminum oxide catalyst is prepared by immersing an aluminum oxide carrier in a chromium salt solution, and then drying and calcining the impregnated carrier. Subsequently, the resulting chromium-impregnated and calcined support is immersed in a potassium salt and then dried. U.S. Patent No. 5132098 (Kvasnikoff et al.) discloses a method for catalytically converting elemental sulfur contained in sulfur compounds of SO₂ , CS₂ , COS, and Claus unit tail gas (residual gas) into H₂S by hydrogenation or hydrolysis. Such hydrogenation or hydrolysis treatment is carried out at a temperature in the range of 140°C to 550°C using a catalyst containing a compound of a metal selected from metals of Group Va, Group VIa, and Group VIII of the periodic table deposited on a silica or silica/alumina support. A more specific catalyst disclosed in U.S. Patent No. 5132098 is an impregnated bead comprising cobalt oxide and molybdenum oxide deposited on alumina to contain 1.75 wt% cobalt and 8 wt% molybdenum, expressed as the weight of the catalyst. U.S. Patent No. 6080379 (Nedez et al.) discloses an alumina catalyst used for treating sulfur-containing gases by performing a Claus reaction or by hydrolysis. The catalyst has optimized macropority, such that the