Method of sweetening hydrocarbon gas from hydrogen sulfide

Abstract

A two or particularly three-phase process, and corresponding apparatus, desulfurizes sour hydrocarbon gas, e.g., natural gas, generally better than known, using a fixed-bed, two-phase processes in terms of the amount of H.sub.2S scavenged and the breakthrough time of H.sub.2S. The three-phase process is effective in scavenging H.sub.2S at ambient temperature and pressure, using a copper salt catalyst impregnated on alumina or other generally inert support, which is regenerable.

Claims

1. A method of reducing an initial H.sub.2S content in a gas mixture, the method comprising: passing the gas mixture, comprising H.sub.2S and a hydrocarbon, through an aqueous suspension of a solid catalyst comprising a copper salt impregnated on an α-Al.sub.2O.sub.3 support; and separating a second gas from the gas mixture passed through the aqueous suspension comprising at least 90 wt. % of liquid water, the second gas having an at least 95% reduced H.sub.2S content relative to the gas mixture, wherein the solid catalyst comprises at least 95 wt. % copper, based upon a total active metal content in the solid catalyst, wherein at least 90 mol % of the copper in the copper salt is copper (II), wherein the copper salt is selected from the group consisting of Cu(NO.sub.3).sub.2, CuCl.sub.2, Cu(CO.sub.3), Cu(HCO.sub.3).sub.2, Cu(SO.sub.4), and mixtures thereof, wherein the solid catalyst comprises less than 1 wt. % CuO and less than 1 wt. % Fe, based upon the total active metal content in the solid catalyst, wherein the support comprises at least 90 wt. % alumina, based on a total weight of the support, wherein the catalyst comprises the copper salt in an amount of from 15 to 18 wt. %, based on a total weight of the solid catalyst, and wherein the solid catalyst comprises no activated carbon.

2. The method of claim 1, wherein at least 99 mol % of the copper in the copper salt is copper (II).

3. The method of claim 1, wherein the gas mixture further comprises CO.sub.2.

4. The method of claim 1, wherein the hydrocarbon comprises methane, ethane, ethylene, propylene, propane, butane, butene, butadiene, and/or isobutylene.

5. The method of claim 1, wherein the hydrocarbon comprises methane.

6. The method of claim 1, wherein the gas mixture is natural gas.

7. The method of claim 1, wherein the aqueous suspension comprises at least 95 wt. % water, based on total liquids in the aqueous suspension.

8. The method of claim 1, wherein the aqueous suspension has a temperature in a range of from 5 to 45° C.

9. The method of claim 1, conducted under ambient conditions.

10. The method of claim 1, wherein the gas mixture is syn gas.

11. The method of claim 1, wherein the solid catalyst comprises at least 99 wt. % copper, based upon a total active metal content in the solid catalyst.

12. The method of claim 11, Wherein the gas mixture is natural gas.

13. A method of reducing an initial H.sub.2S content in a gas mixture, the method comprising: passing the gas mixture, comprising H.sub.2S and a hydrocarbon, through an aqueous suspension of a solid catalyst comprising a copper salt impregnated on a support; and separating a second gas from the gas mixture passed through the aqueous suspension comprising at least 90 wt. % of liquid water, the second gas having an at least 95% reduced H.sub.2S content relative to the gas mixture, wherein the solid catalyst comprises at least 95 wt. % copper, based upon a total active metal content in the solid catalyst, wherein at least 90 mol % of the copper in the copper salt is copper (II), wherein the copper salt comprises CuCl.sub.2 and/or Cu(NO.sub.3).sub.2 and optionally further at least one selected from the group consisting of Cu(CO.sub.3), Cu(HCO.sub.3).sub.2, and Cu(SO.sub.4), wherein the solid catalyst comprises less than 1 wt. % CuO and less than 1 wt. % Fe, based upon the total active metal content in the solid catalyst, wherein the support comprises at least 90 wt. % alumina, based on a total weight of the support, wherein the catalyst comprises the copper salt in an amount of from 15 to 18 wt. %, based on a total weight of the solid catalyst, and wherein the solid catalyst comprises no activated carbon.

14. The method of claim 13, wherein the support is α-Al.sub.2O.sub.3.

15. A method of reducing an initial H.sub.2S content in a gas mixture, the method comprising: passing the gas mixture, comprising H.sub.2S and a hydrocarbon; through an aqueous suspension of a solid catalyst comprising a copper salt impregnated on a support, the aqueous suspension having a solid-liquid ratio, measured as solid catalyst mass per mass of liquid, is in a range of from 0.01 to 1.5; and separating a second gas from the gas mixture passed through the aqueous suspension comprising at least 90 wt. % of liquid water, the second gas having an at least 95% reduced H.sub.2S content relative to the gas mixture, wherein the solid catalyst comprises at least 95 wt. % copper, based upon a total active metal content in the solid catalyst, wherein at least 90 mol % of the copper in the copper salt is copper (II), wherein the copper salt is selected from the group consisting of Cu(NO.sub.3).sub.2, CuCl.sub.2, Cu(CO.sub.3), Cu(HCO.sub.3).sub.2, Cu(SO.sub.4), and mixtures thereof, wherein the solid catalyst comprises less than 1 wt. % CuO and less than 1 wt. % Fe, based upon the total active metal content in the solid catalyst, wherein the support comprises at least 90 wt. % alums, based on a total weight of the support; wherein the catalyst comprises the copper salt in an amount of from 15 to 18 wt. %, based on a total weight of the solid catalyst, and wherein the solid catalyst comprises no activated carbon.

16. The method of claim 15, wherein the support is α-Al.sub.2O.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

(2) FIG. 1 shows a design of a process apparatus used for scavenging H.sub.2S from natural gas stream within the scope of the invention;

(3) FIG. 2 shows the BET hysteresis curve for a Cu—Al.sub.2O.sub.3 catalyst useful according to the invention, which catalyst may be prepared by a wet incipient method using a copper salt;

(4) FIG. 3 shows a scanning electron microscopy (SEM) image of a Cu—Al.sub.2O.sub.3 catalyst within the scope of the invention;

(5) FIG. 4 shows a transmission electron microscopy (TEM) image of a Cu—Al.sub.2O.sub.3 catalyst within the scope of the invention; and

(6) FIG. 5 shows the x-ray diffraction pattern of a Cu—Al.sub.2O.sub.3 catalyst within the scope of the invention;

(7) FIG. 6 shows a comparison between the H.sub.2S breakthrough curves obtained using the three-phase (gas-liquid-solid) and the two-phase processes (gas-solid) with a Cu—Al.sub.2O.sub.3 catalyst within the scope of the invention; and

(8) FIG. 7 shows the effect of flow-rate on H.sub.2S breakthrough curves at 50, 100, and 150 mL/min using a Cu—Al.sub.2O.sub.3 catalyst within the scope of the invention, with the feed natural gas containing 100 ppmv H.sub.2S going 50 mg copper catalyst utilized in 10 mL of water at room temperature and atmospheric pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Aspects of the invention provide methods of reducing an initial H.sub.2S content in a gas mixture, the methods comprising: passing the gas mixture, comprising H.sub.2S and a hydrocarbon, through an aqueous suspension of a solid catalyst comprising a copper salt impregnated on a support; and separating off a second gas with a reduced H.sub.2S content relative to the gas mixture, wherein the catalyst comprises more than 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % copper, based upon a total active metal content in the catalyst. “Active metal” means those metals that react with the H.sub.2S under the process conditions, preferably at no more than 100, 75, 50, 45, 40, 35, 32.5, 30, 27.5, or 25° C., particularly under ambient conditions, i.e., STP.

(10) The copper salt may comprise at least 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, 99.9, 99.99, 99.999, or 99.9999% copper (II). The copper salt may comprise or be selected from the group consisting of, for example, Cu(NO.sub.3).sub.2, CuF.sub.2, CuCl.sub.2, CuBr.sub.2, CuCO.sub.3, Cu(HCO.sub.3).sub.2, CuSO.sub.4, CuSiF.sub.6, CuSeO.sub.3, CuSeO.sub.4, Cu(ClO.sub.4).sub.2, Cu(ClO.sub.3).sub.2, Cu(IO.sub.3).sub.2, Cu(HCO.sub.2).sub.2, Cu(BF.sub.4).sub.2, Cu(O.sub.2CCH.sub.3).sub.2, [C.sub.6H.sub.11(CH.sub.2).sub.3CO.sub.2].sub.2Cu, Cu.sub.2P.sub.2O.sub.7, C.sub.26H.sub.34O.sub.6Cu, Cu(O.sub.2C[CHOH].sub.nCH.sub.2OH) where n is 2, 3, or 4, [Cu(NH.sub.3).sub.4]SO.sub.4, or a mixture of two or more of any of these. The copper salt may preferably comprise Cu(NO.sub.3).sub.2, CuCl.sub.2, Cu(CO.sub.3), Cu(HCO.sub.3).sub.2, and/or Cu(SO.sub.4), esp. Cu(NO.sub.3).sub.2, CuCl.sub.2, and/or Cu(SO.sub.4). The copper salt should generally have some solubility in water or a solvent system, in order to be impregnated into the support.

(11) The support may comprise alumina, graphite, graphene, activated carbon, aluminosilicate, or a mixture of two or more of any of these. The support may comprise at least 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, 99.9, 99.99, 99.999, or 99.9999 wt. % alumina, based on a total weight of the support, though α-Al.sub.2O.sub.3 or γ-Al.sub.2O.sub.3 have shown particular utility. The support may be a mixture of alumina types.

(12) The catalyst may comprise the copper salt in an amount of from 10 to 20, 12.5 to 19, 15 to 18.5, 16, 17, or 18 wt. %, based on a total weight of the solid catalyst.

(13) The reduced H.sub.2S content may respectively be no more than 25 (or 5) wt. % of the initial H.sub.2S content within 220 (or 250) minutes of contact with the aqueous suspension at a temperature in a range of from 15 to 40° C. and a pressure of 0.9 to 1.2 bar. The reduction of H.sub.2S for exemplary two or three-phase arrangements can be seen in FIG. 6, which shows that passing gases over a solid bed more rapidly begins take up, but the three-phase system ultimately more rapidly removes the H.sub.2S. H.sub.2S removal may be at least 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. %, relative to the initial H.sub.2S content, within 325, 315, 310, 305, 300, 290, 275, 265, 250, 245, 240, 235, 230, 225, 220, 215, 210, or 200 minutes of exposure to the three-phase system under ambient conditions. These rates can be increased by a factor of 1.1, 1.2, 1.25, 1.33, 1.4, 1.45, 1.5, 1.6, 1.67, 1.75, 1.85, 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 5, 6, 7.5, or even 10, by increasing the reaction temperature from 25 to 35, 50, 75, 100, 125, 150, 175, 200, 250, 300, 400, 500, 600, 750, or 900° C.

(14) The gas mixture may further comprise CO.sub.2, and the CO.sub.2 may be present in 2, 5, 10, 15, 20, 25, 30, 40, 50, 60, 65, 75, 85, 100, 150, 200, 250-fold the amount, or more, of the H.sub.2S based on moles. The gas mixture may further contain N.sub.2, CO, Ar, H.sub.2, He, NH.sub.3, O.sub.2, and/or O.sub.3, but may exclude any or all of these.

(15) The hydrocarbon may comprise methane, ethane, ethylene, propylene, propane, butane, butene, butadiene, and/or isobutylene. The gas mixture may be syn gas. The hydrocarbon may further or alternatively include dimethyl ether, ethyl methyl ether, neopentane. The hydrocarbon may comprise at least 25, 33, 45, 50, 60, 65, 70 75, 80, 85, 90, 92.5, 95, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % methane, ethane, ethylene, propylene, propane, butane, butene, butadiene, and/or isobutylene, based on the total hydrocarbons. The gas mixture may be natural gas. The hydrocarbon may contain ethane and ethylene, or propane and propylene

(16) The aqueous suspension may comprise at least 75, 80, 85, 90, 92.5, 95, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % water, based on total liquids in the aqueous suspension, but may, in addition or in place of water, contain ethylene glycol, methanol, ethanol, propanol, isopropanol, n-butanol, ethyl acetate, pet ether, pentane, hexane(s), decalin, THF, dioxane, toluene, xylene(s), and/or o-dichlorobenzene.

(17) The aqueous suspension may have a temperature in a range of from 5 to 45, 10 to 40, 15 to 35, 20 to 30, or 22.5 to 27.5° C. Inventive methods may be conducted under ambient conditions, e.g., having such temperatures or pressures of no more than 1.5, 1.4, 1.3, 1.2, 1.1, 1.075, 1.05, 1.04, 1.03, 1.025, 1.02, or 1.015 bar.

(18) Aspects of the invention may provide (heterogeneous) desulfurization catalysts, comprising: a support comprising Al.sub.2O.sub.3 in an amount of at least 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. %, based upon total support weight, the support being inert to desulfurization at ambient conditions; copper (II) ions upon and impregnated within the support in an amount of at least 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, 99.9, 99.99, or 99.999 wt. %, based upon total catalytically active metals in the catalyst at the ambient conditions, and a liquid comprising at least 50, 60, 70, 75, 80, 85, 90, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % H.sub.2O, based upon total solvent weight. In addition or in place of water, the liquid may contain ethylene glycol, methanol, ethanol, propanol, isopropanol, n-butanol, ethyl acetate, pet ether, pentane, hexane(s), decalin, THF, dioxane, toluene, xylene(s), and/or o-dichlorobenzene. That is, as above, the “aqueous” suspension may contain a minority fraction of, or even no, water. The support may contain alternate materials, as above, but generally need not use doped or ion-exchanged alumina (such as those modified with Ce) or zeolites, and may use unmodified (commercially available) materials.

(19) Any of the following features, like those above, may be explicitly combined in any permutation in catalysts within the scope of the invention. Inventive catalysts need not, but may largely exclude aldehydes, i.e., comprise no more than 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.5, 0.1, 0.001, or 0.0001 wt. % or no more than trace detectable amounts of aldehyde(s). Likewise or separately, the catalysts may comprise no more than 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.5, 0.1, 0.001, or 0.0001 wt. % or no more than trace detectable amounts of carboxylate(s). Likewise or separately, the catalysts may comprise no more than 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.5, 0.1, 0.001, or 0.0001 wt. % or no more than trace detectable amounts of amine(s), esp. tertiary amine(s), and/or amino acid(s).

(20) Aside from copper (ions) amongst the active catalyst metals, inventive catalysts need not, but may contain fewer than 50, 33, 25, 20, 15, 10, 7.5, 5, 2.5, 2, 1, or 0.1 wt. %, relative to total active metals, of Zn, Co, W, Ca, Cd, Sn, Mn, Li, Mg, Se, Sr, Fe, Pt, Rh, Ni, Pd, Ru, V, and/or Ir. Inventive catalysts need not, but may contain fewer than 50, 33, 25, 20, 15, 10, 7.5, 5, 2.5, 2, 1, or 0.1 wt. %, relative to total active metals, of any other metals besides copper. Inventive catalysts may avoid, i.e., contain no Claus catalyst (TiO.sub.2 and/or Al.sub.2O.sub.3), or may contain no more than 10, 5, 2.5, 1, 0.5, 0.1, 0.001 wt. %, relative to total solid catalyst weight, of Claus catalyst(s). Inventive catalysts may contain fewer than 10, 5, 2.5, 1, 0.5, 0.1, 0.001 wt. % metal oxides, and/or less than 7.5, 5, 2.5, 1, or 0.5 wt. % CuO, relative to total solid catalyst weight. The supports may contain less than 10, 5, 2.5, 1, 0.5, 0.1, 0.001 wt. % CeO.sub.2 and/or any forms of cerium in support, relative to total support weight. Inventive catalysts may contain no more than 33, 30, 27.5, 25, 22.5, 21, or 20 wt. % active metal in the catalyst, relative to a total weight of metal and support.

(21) While not necessarily, inventive catalysts (or compositions comprising the desulfurization/de-H.sub.2S catalyst may comprise no nitrite, or may comprise no more than 40, 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total solid catalyst/composition weight, of nitrite. Copper nitrites may be selectively excluded. Likewise or separately, inventive catalysts/compositions may contain no more than 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total solid catalyst/composition weight, of oxidizing agents, e.g., peroxide(s), hydroperoxide(s), peracid(s), and/or ozone. Inventive catalysts/compositions may comprise no more than 40, 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total solid catalyst/composition weight, of amino acid, aspartate, carbonate, citrate, gluconate, sulfate, and/or yeast, or may entirely avoid any or all of these, for example, beyond inevitable traces. Inventive catalysts may comprise no chelates, e.g., amine and/or phosphorous-containing chelates, and/or monodentate and/or bidentate and/or tridentate chelates, or may comprise no more than 40, 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, 1, or 0.5 wt. %, relative to the total solid catalyst/composition weight, of any or all such chelates.

(22) Inventive reactions, reactors, treatment vessels, and/or reaction systems may not require stirring at all, or may be carried out with shearing no more than 20,000, 10,000, 5,000, 2,500, 1,000, 750, 500, 400, 300, 250, 200, 150, 125, 100, 75, 50, 25, or 10 Hz. Inventive reactions, reactors, treatment vessels, and/or reaction systems may employ baffles or static flow agitators/interrupters.

(23) Apparatuses for sweetening relevant gas mixtures may include: a first column and a second column, each being substantially vertical and parallel to each other, e.g., no more than 80, 85, 88, or 89° skew between their angular projections; an upper connector; and a lower connector. While not necessarily 90° from the ground (or a base), the vertical columns will generally be within 10, 5, 2, or 1° of orthogonality to the base, and are referred to as “vertical” for brevity herein. The connectors may connect the first and second vertical columns to create a loop, with an upper connector going from an upper portion of the first vertical column to an upper portion of second vertical column (generally lower in height than the interface at the first vertical column). The lower connector may go from a lower portion of the second vertical column to a lower portion of first vertical column (generally lower in height than the interface at the second vertical column). The upper connector may be inclined downward from the first to second vertical column, and/or the lower connector may be inclined upward from the first to second vertical column, e.g., making a trapezoidal elevational view, as seen in FIG. 1. The upper and/or lower connector may be angled, negatively or positively, within 45, 30, 22.5, 15, 7.5, 5, 3, or 1° of a parallel to the base of the apparatus, but may even be parallel to the base (orthogonal to the vertical column). The reactive length of the first vertical column(s) may have a ratio to that of the second vertical column(s) in a range of from 5 to 1:1, 4 to 1.1:1, 3 to 1.2:1, 2 to 1.25:1, or 1.75 to 1.3:1. That is, the first vertical column will generally have a greater reactive length than the second, though the first and second vertical column(s) may have the same physical length/height. Typically, only the first vertical column will use phase separators, such as fritted glass barriers, at least towards the bottom of the first vertical column, where a gas inlet may be located. The first and second vertical column(s) may have identical cross-sectional areas in flow direction, or the cross-sectional areas may be, for example, 1:1.05 to 3, 1:1.1 to 2.5, 1:1.25 to 2, which ratios may be modified based upon the relative count of first and second vertical column(s).

(24) Inventive apparatuses may include 1, 2, 3, 4, or 5 further connector(s) along the height of the vertical columns. The upper and lower connectors will generally be attached at no more than 25, 20, 15, 10, or 5% (length) from the first vertical column bottom and/or top, based on the entire length of the first vertical column. The upper and lower connectors will generally be attached at no less than 10, 15, 20, 25, 30, 35, or 40% (length) from the second vertical column bottom and/or top, based on the entire length of the second vertical column. The upper and lower connector(s) may have identical cross-sectional areas to each other and/or first vertical column(s) and/or second vertical column(s), in flow direction, or the upper to lower connector cross-sectional areas may be, for example, 1:0.5 to 2, 1:0.75 to 1.5, 1:0.9 to 1.25, with the first and/or second vertical column(s) generally having 1.1, 1.25, 1.5, 2, or 2.5-fold greater cross-sectional areas. A diameter of the vertical column(s) may be in a range of from 1 cm to 3 m, depending upon the application, e.g., at least 0.5, 0.75, 1, 1.5, 2, 3, 5, 10, 25, 50, or 100 cm, and/or up to 5, 4, 3, 2.5, 2, 1.5, 1.25, 1, 0.75 m.

(25) The vertical columns and/or connectors generally contain a liquid or gas/liquid phase, such as water, an aqueous solution, an organic solution, or a split/emulsified organic-aqueous mixture, including the inventive catalyst suspended therein. Roughly 20 to 50 wt. % of the liquid/catalyst mixture may be contained in the first vertical column(s), with 20 to 40 wt. % in the second vertical column(s), and 20 to 30 wt. % in the connectors. The liquid/catalyst suspension, when spent, may collect in a bottom portion of the second vertical column(s), which may be below the bottom connector interface with the second vertical column and may constitute up to 2, 5, 10, 15, or 20% of the second vertical column's volume. The feed gas for sweetening may be led through a column of liquid/catalyst suspension occupying 20 to 99, 33 to 95, 50 to 90, 60 to 85, or 66 to 75% of the first vertical column's total volume. The liquid/catalyst suspension may gather in the upper connector, optionally behind a valve, and/or may flow through, generally downwards in the upper connector into the second vertical column, and again downwards in the lower connector to a lower portion of the first vertical column, to be driven upwards by the gas feed and/or one or more pumps.

(26) The spent catalyst/liquid may be held up with a valve and/or may be led off to a regeneration, e.g., as set forth in U.S. Pat. No. 8,002,971 or 8,071,146, each of which is incorporated in its entirety by reference herein. Plant layouts including inventive apparatuses may advantageously avoid, e.g., amine contactors and/or basic sweeteners, or may allow 5, 10, or 20 wt. % less base to be used in sweetening.

(27) Inventive apparatuses may include 1, 2, 3, 4, 5, or more of the vertical column(s), connector(s), gas inlet(s), gas outlet(s), catalyst inlet(s), and/or catalyst outlet(s), and the duplicated and/or multiple elements may be unified in any manner advantageous for the given application, e.g., 5 first vertical columns into 1 or 2 common upper connector(s) into, e.g., 4 or 3 second vertical column. The columns and connectors may have circular, square, and/or ovular cross-sections, and may include, e.g., annular portions inflecting radially inwardly and/or outwardly towards the cross-sectional center. A flux of the feed gas through the liquid/catalyst suspension may be in a range of from 0.1 to 25, 0.5 to 15, 1 to 10, 1.5 to 7.5, or 2 to 5 mL/s for a 1 cm cross-sectional diameter vertical column.

(28) Inventive methods may operate at pHs in the neutral range and/or above 4, though the efficiency of the H.sub.2S removal should be within 90% across the pH range of 2 to 13, 3 to 11, 4 to 10, 5 to 8, or 6 to 7.5. No particular considerations need to be taken regarding pH, and acceptable reaction pHs will generally be at the ambient/natural conditions of water available. Inventive methods may operate under 700, 500, 350, 200, 180, 90, or 40° C. The method may preferably be operated at the environmental conditions at the site of implementation, e.g., at or within 1000, 750, 500, 250, 200, 150, 100, 50, or 20 meters of a natural gas source, an oil source, a hydrocarbon platform, an LNG storage facility, an LNG transport tanker, a petrochemical plant, a refinery, a polymerization reactor, a cracker, a PSA, an MTG plant, and/or an MTO plant.

(29) Aspects of the invention provide two or three-phase processes for scavenging H.sub.2S from hydrocarbon gas mixtures, i.e., a gas comprising a hydrocarbon and H.sub.2S, such as a sour natural gas stream, syn gas, cracking off-gases, exhausts, crude or at least partially purified methane, ethane, ethylene, propylene, propane, butane, butene, butadiene, and/or isobutylene gas(es). Gas phases may comprise H.sub.2S, CO.sub.2, and a hydrocarbon, e.g., methane. Liquid phases within the invention, when present, may comprise or consist essentially of water, i.e., at least 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, 99.9, 99.99, 99.999, or 99.9999 wt. % of a total weight of the liquid phase weight being water. Solid phases generally contain a copper catalyst impregnated on alumina, wherein the catalyst metal may comprise at least 75, 80, 85, 90, 92.5, 95, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % Cu relative to total metals, and/or the support may comprise alumina in amount of at least 75, 85, 90, 92.5, 95, or 97.5 wt. % of the support total weight. The gas(es) may be bubbled through a two-phase bed and/or into the three-phase column, contacting the dispersed solid phase, i.e., supported copper-based catalyst, in an air or at least partially inert atmosphere or within the bulk of liquid phase, e.g., water, an aqueous mixture/solution, an organic phase, etc.

(30) Concentrations of H.sub.2S in exit gas stream(s) may be monitored continuously, enabling the construction of H.sub.2S breakthrough curves and the calculation of the amount of H.sub.2S scavenged.

(31) The copper-based catalyst may be prepared by a wet incipient method, i.e., capillary impregnation or dry impregnation, typically comprising dissolving active metal precursor(s) in an aqueous or organic solution, adding the metal-containing solution to a catalyst support, optionally having the same pore volume (or within 50, 33, 25, 15, 10, or 5%) as the volume of the added solution, and allowing capillary action to draw the solution into the pores. In wet incipient methods excess solution (beyond the support pore volume) can cause the solution transport to change from a capillary action process to a slower diffusion process. Catalysts can then be dried and calcined to drive off the volatile components within the solution, depositing the metal on the catalyst surface. Maximum loading is generally limited by the solubility of the precursor in the solution. Concentration profiles of impregnated compound(s) depend on mass transfer within the pores during impregnation and drying.

(32) Inventive catalysts are generally selective towards the acid gas, i.e., H.sub.2S, and thus the presence of hydrocarbon gases in the gas feed generally will not affect the efficacy of inventive catalyst(s). Selectivities may be in a range of 1.5 to 100, 2 to 50, 3 to 25, based on relative kinetic reaction rate constants. Three-phase processes showed surprising superiority over two-phase (gas-solid) fixed-bed processes in terms of the amount of H.sub.2S scavenged and breakthrough time. Inventive two and three-phase processes are effective at ambient conditions, and the catalyst is typically regenerable.

(33) Aspects of the invention may provide (i) complete dissolution (or leaving less than 15, 10, 7.5, 5, 2.5, 2, 1, 0.1, 0.01, 0.001, or 0.0001 wt. %, based on the feed gas, or even no more than detectable limits) of H.sub.2S from a hydrocarbon gas stream, such as natural gas, into the solid-liquid system; (ii) the use of three phase sorbent/catalyst method and/or apparatus to scavenge H.sub.2S, i.e., gas/liquid/solid; (iii) use of copper impregnated on alumina as catalyst for reduction of H.sub.2S in aqueous solution; and/or (iv) synergetic effect(s) of adsorption-absorption of H.sub.2S on the rate of H.sub.2S reduction.

(34) Inventive methods may involve loading one or more copper salts, such as Cu(NO.sub.3).sub.2, CuF.sub.2, CuCl.sub.2, CuBr.sub.2, CuCO.sub.3, Cu(HCO.sub.3).sub.2, CuSO.sub.4, CuSiF.sub.6, CuSeO.sub.3, CuSeO.sub.4, Cu(ClO.sub.4).sub.2, Cu(ClO.sub.3).sub.2, Cu(IO.sub.3).sub.2, Cu(HCO.sub.2).sub.2, Cu(BF.sub.4).sub.2, Cu(O.sub.2CCH.sub.3).sub.2, [C.sub.6H.sub.11(CH.sub.2).sub.3CO.sub.2].sub.2Cu, Cu.sub.2P.sub.2O.sub.7, C.sub.26H.sub.34O.sub.6Cu, Cu(O.sub.2C[CHOH].sub.nCH.sub.2OH) where n is 2, 3, or 4, [Cu(NH.sub.3).sub.4]SO.sub.4, etc., onto surfaces of support(s) comprising alumina, e.g., γ-Al.sub.2O.sub.3, α-Al.sub.2O.sub.3, graphite, graphene, activated carbon, or aluminosilicates (with various alumina-silica ratios). Loading percentages of the catalyst on the support(s) may be as high as 33, 25, 20, 18, 15, 12.5, or 10 wt. %, considering all catalytic metals on the support (or in the catalyst compound). Catalyst precursor solutions may comprise water in at least 75, 80, 85, 90, 92.5, 95, 97.5, 98, 99, 99.1, 99.5, or 99.9 or more wt. %, but may also comprise water mixed with a chelating agent, or copper complexes, such as copper(II)-n,n-diethylethylenediamine, [CuLn]-(BAr.sub.4).sub.2—wherein Ln is ligand, B is boron, and Ar is aryl etc.).

(35) Inventive catalysts may be used (1) directly in a fixed bed adsorbent for scavenging H.sub.2S from sour gas stream, i.e., 50, 60, 70, 75, 80, 85, 90, 95, 98, 99, 99.99 or more % solvent free; (2) mixed in a liquid (sorbent solution), the sour gas being allowed to bubble through the sorbent solution; (3) in counter-current circulation of the mixed catalyst-solution with the sour gas stream; and/or (4) co-current circulation of the mixed catalyst-solution with the sour gas stream. Counter-current and co-current circulations may be implemented in parallel and/or in series. Exit gas concentrations may be measured as a function of time and breakthrough curves may be recorded, with differences between feed and exit stream H.sub.2S concentrations representing the amount of H.sub.2S scavenged.

(36) In an inventive plant arrangement, an optionally preheated H.sub.2S-containing feed may flow through a heater where the feed mixture is totally vaporized and heated to the required temperature before entering the reactor and flowing through a fixed-bed and/or liquid layer of inventive catalyst where the hydrodesulfurization (HDS) reaction takes place. The HDS reaction products may be at least partially cooled, if necessary, by flowing through the heat exchanger where the reactor feed was preheated and then through, e.g., a water-cooled heat exchanger before optional (de)pressurization and/or gas separation. Rather than, or in addition to, routing gas from a gas separator vessel, through an amine contactor for removal of the reaction product H.sub.2S, this gas may be passed through at least one inventive sweetening apparatus. The H.sub.2S-free gas may then be sent to further processing and/or an end use.

(37) Sour gas, e.g., from a stripper or from a hydrocarbon source may contain H.sub.2, CH.sub.4, C.sub.2H.sub.6, H.sub.2S, C.sub.3H.sub.8, C.sub.3H.sub.6, C.sub.4H.sub.10, butene(s), pentene(s), and/or heavier components. Sour gas, particularly containing H.sub.2S, but optionally also organic thiols, sulfides, disulfides, thiophenes, and sulfur oxides, from basically any source may be sent to a gas processing plant comprising an inventive sweetening apparatus for removal of the H.sub.2S. After the H.sub.2S is removed in the inventive sweetening apparatus, and optionally further in an amine gas treating unit, the sweetened gas may be optionally passed through a series of distillation towers to recover and/or isolate hydrocarbon components, such as methane, ethane, ethylene, propane, propylene, butane, pentane, and/or heavier components. The H.sub.2S removed/recovered by the inventive sweetening apparatus(es), and any amine gas treating unit(s), may be subsequently converted to elemental sulfur in a Claus Process unit or to sulfuric acid in a wet sulfuric acid process and/or in a conventional Contact Process.

WORKING EXAMPLES

Example 1

(38) A fixed mass (0.05 g) of solid copper catalyst is placed in a 1.5 mm jacketed glass tube. Glycol solution was circulated to maintain the desired reaction temperature (e.g., room temperature of −22° C.)±+1° C. Synthetic natural gas streams containing variable concentrations of H.sub.2S (50, 100 ppmv), CO.sub.2 (1000, 2000 ppmv) and the balance methane were introduced at different flowrates. The pressure drop across the catalyst bed was monitored using a digital pressure gauge. The concentrations of inlet and outlet H.sub.2S were measured continuously using an RAE multi-gas meter.

Example 2

(39) The same procedure as in Example 1 was repeated but pure deionized water (10 mL) was used as a blank solution. The water was maintained in a 1-cm ID fretted glass tube.

Example 3

(40) The same procedure as in Example 2 was repeated where copper-based catalyst-water slurry was used instead of pure water. The desired amount of copper-based catalyst (0.05 g) was dispersed in 10 mL deionized water.

Example 4

(41) The same procedure as in Example 2 was repeated but a mixture of copper complex (0.05 g) was used instead of pure water.

(42) Table 1

(43) TABLE-US-00001 TABLE 1 Surface area and pore size analysis for Cu—Al.sub.2O.sub.3 catalyst Property Value BET surface area: 62.5383 m.sup.2/g BJH adsorption cumulative surface area of pores 68.097 m.sup.2/g between 17.000 and 3000.000 Å diameter: Å and 3000.000 Å diameter: Adsorption average pore width (4V/A by BET): 202.9286 Å width (4V/A by BET): BJH adsorption average pore diameter (4V/A): 175.833 Å BJH desorption average pore diameter (4V/A): 153.486 Å

(44) Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.

Example 5

(45) Process of scavenging H.sub.2S. A laboratory scale process of scavenging H.sub.2S by a circulating fluidized slurry of Cu—Al.sub.2O.sub.3 is exemplified in FIG. 1. On large scale, gas stream(s) containing H.sub.2S may be introduced at one or more locations at the bottom of the fluidized reactor, i.e., below 33, 25, 20, 15, 10, 7.5, 5, 4, 3, 2, and/or 1% of the reactor height, where the slurry containing the Cu—Al.sub.2O.sub.3 and optional solvents/solutions may contact the gas stream(s) and be carried upward. Sweetened gas may then be passed through a separator element (2, upper), such as fritted glass, gauze, and/or membrane(s), etc., to one or more analyzers and/or an outlet (1). The catalyst slurry may be accumulated in an inclined portion, such as a tube, and a check slurry valve (4) may allow partial flow to maintain a specified solid-liquid ratio. For example, the solid-liquid ratio, measured as the percent solid catalyst mass per mass of liquid, may be in a range of from 0.01 to 5, 0.05 to 5, 0.1 to 4, 0.15 to 3.5, 0.2 to 3, 0.25 to 2.5, 0.3 to 2, 0.33 to 1.75, 0.35 to 1.5, 0.4 to 1.25, 0.425 to 1, 0.45 to 0.75%, e.g., 0.5 mg of catalyst may be used in 10 g of liquid. The accumulated slurry or used catalyst can be allowed to flow downwards by the effect of gravity and may be mixed with fresh catalyst and/or at least partially regenerated. The Cu—Al.sub.2O.sub.3 catalyst may be added batch-wise and/or continuously in a catalyst inlet (7) and may be added to tailor the efficiency of scavenging H.sub.2S gas and/or heat transfer, for example. Part of the slurry catalyst may be accumulated in a spent catalyst container through a valve (5), and/or sent to a recycle, while non-separated catalyst may be returned to contact the inlet gas stream (3) and cycled again with the gas stream. Spent catalyst (6) may be regenerated in a separate process by washing with oxidizing agent such as nitric acid or hydrochloric acid, washed, e.g., with water, and used again.

(46) FIG. 2 shows a BET hysteresis loop for a supported Cu—Al.sub.2—O.sub.3 catalyst according to the invention. The catalyst was prepared by wet incipient method using a copper salt. FIGS. 3, 4, and 5 respectively shows a scanning electron microscopy (SEM) image, transmission electron microscopy (TEM) image, and x-ray diffraction pattern, of the Cu—Al.sub.2O.sub.3 catalyst.

(47) As seen on 5 micron scale in FIG. 3, inventive catalyst may take a substantially amorphous, fractal, and/or flocculent morphology, with fuzzy outcroppings upon agglomerated masses of irregular shape. The outcroppings may have a somewhat snow-flake like appearance with roughly 1 to 3 micron widths and 2 to 5 micron lengths in 2D. FIG. 4 reveals that the catalyst particles have an irregular shape on 200 nm scale, with (in 2D) ovular and/or circular volumes of greater density spaced irregularly throughout the morphology, with occasional agglomerations of 2 to 3 spheroids, spaced by 100 nm or more from other spheroids and/or agglomerations. The 200 nm scale TEM shows a jagged outer surface of the catalyst particle/flake, apparently overlaid, with approximately 400 to 600 micron span in its longest dimension and some 200 to 300 micron span perpendicular to the longest dimension.

(48) FIG. 5 shows 2θ peaks in the XRD of inventive catalyst at ˜19° (full width at half maximum—FWHM ˜5, 0.2 relative intensity—r.i.), ˜33° (FWHM ˜4, 0.3 r.i.), ˜36° (FWHM ˜4, 0.6 r.i.), ˜38° (FWHM ˜2, 0.4 r.i.), ˜43° (FWHM ˜1, 0.4 r.i.), ˜45° (FWHM ˜1, 1 r.i.), ˜46° (FWHM ˜2 with shoulder, 0.65 r.i.), ˜52° (FWHM ˜2, 0.35 r.i.), 61° (FWHM ˜4, 0.25 r.i.), ˜63° (FWHM ˜3, 0.25 r.i.), ˜67° (FWHM ˜3, 0.8 r.i.), and ˜76° (FWHM ˜2, 0.25 r.i.). FIG. 6 shows a comparison between the H.sub.2S breakthrough curves obtained using three-phase and two-phase processes. The amount of catalyst is very comparable, i.e., within 95 wt. % of each other, 4.7% for both processes, dispersed in 10 mL water, and each sour natural gas feed contained 100 ppmv H.sub.2S. The scavenging process was conducted at room temperature and atmospheric pressure. While the solid, two-phase application shows and earlier adsorption of H.sub.2S and a gradual, almost linear adsorption process, the three-phase, catalyst slurried in liquid adsorbed the H.sub.2S in roughly 100 minutes, while the two-phase approach needed about 600 minutes to accomplish the same H.sub.2S removal.

(49) FIG. 7 shows the effect of sour gas flow rate on the H.sub.2S breakthrough curve, whereby the sour natural gas feed contained 100 ppmv H.sub.2S and the amount of supported copper catalyst utilized was about 50 mg. The catalyst is dispersed in 10 mL water. The scavenging process was conducted at room temperature and atmospheric pressure.

(50) Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

REFERENCE SIGNS

(51) 1 gas outlet 2 phase separator, e.g., fritted glass 3 gas inlet 4 check valve outlet valve 6 catalyst outlet, e.g., spent catalyst or regeneration feed 7 catalyst inlet