Synergized hemiacetals composition and method for scavenging sulfides and mercaptans

Abstract

This invention provides a composition comprising I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, and II. at least one reaction product between a nitrogen-free sugar alcohol and an aldehyde or ketone, and optionally III. at least one reaction product from III.a) formaldehyde, and III.b) an amine, selected from the group consisting of primary alkyl amines having 1 to 4 carbon atoms, and primary hydroxy alkyl amines having 2 to 4 carbon atoms, and optionally IV. at least one solid suppression agent selected from the group consisting of IV(a). alkali or alkaline earth metal hydroxides IV(b). mono-, di- or tri-hydroxy alkyl, aryl or alkylaryl amines, IV(c). mono-, di- or tri-alkyl, aryl or alkylaryl primary, secondary and tertiary amines or IV(d). multifunctional amines and IV(e). mixtures of compounds of groups IV(a) to IV(c). wherein alkyl is C.sub.1 to C.sub.15, aryl is C.sub.6 to C.sub.15 and alkylaryl is C.sub.7 to C.sub.15.

Claims

1. A composition comprising I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, and II. at least one reaction product between a sugar alcohol and an aldehyde or ketone wherein the reaction products I. and II. are hemiacetals and/or acetals.

2. The composition according to claim 1, further comprising III. at least one reaction product from formaldehyde and ammonia and/or an amine, selected from the group consisting of primary alkyl amines having 1 to 10 carbon atoms, and primary hydroxy alkyl amines having 2 to 10 carbon atoms.

3. The composition according to claim 1, further comprising IV. at least one inorganic or organic alkaline compound that functions as a solids suppression agent.

4. The composition according to claim 1 wherein the aldehyde or ketone contains 1 to 10 carbon atoms.

5. The composition according to claim 1, wherein the aldehyde or ketone is selected from the group consisting of formaldehyde, paraformaldehyde, glyoxal, acetaldehyde, propionaldehyde, butyraldehyde and glutaraldehyde.

6. The composition according to claim 1, wherein the aldehyde or ketone is formaldehyde.

7. The composition according to claim 1, wherein the monohydric alcohol comprises 1 to 15 carbon atoms.

8. The composition according to claim 1, wherein the monohydric alcohol is an aliphatic alcohol.

9. The composition according to claim 1, wherein the monohydric alcohol is selected from the group consisting of methanol, ethanol, propanol, iso-propanol, n-butanol, iso-butanol, tert-butanol, pentanol, hexanol, heptanol and octanol, and any mixture thereof.

10. The composition according to claim 1, wherein the sugar alcohol is a polyol obtainable by reduction of a sugar.

11. The composition according to claim 1, wherein the sugar alcohol contains 4 to 12 carbon atoms and 4 to 10 hydroxy groups wherein not more than one hydroxy group is attached to each carbon atom.

12. The composition according to claim 1, wherein the sugar alcohol is selected from tetritols, pentitols and hexitols.

13. The composition according to claim 1, wherein the sugar alcohol is selected from the group consisting of erythritol, threitol, arabitol, ribitol, xylitol, allitol, dulcitol, sorbitol, iditol, mannitol, talitol, inositol.

14. The composition according to claim 1, wherein the sugar alcohol is a linear sugar alcohol having the general formula (1)
HO—CH.sub.2—(CHOH).sub.n—CH.sub.2—OH  (1) wherein n is 2, 3 or 4.

15. The composition according to claim 1, wherein the reaction product between a sugar alcohol and an aldehyde or ketone is selected from the group consisting of:
OHCHR.sub.1—O—CH.sub.2—CH(OCHR.sub.1OH)—CH(OCHR.sub.1OH)—CH(OCHR.sub.1OH)—CH(OCHR.sub.1OH)—CH.sub.2—O—CHR.sub.1OH  (2),
OHCHR.sub.1—O—CH.sub.2—CH(OCHR.sub.1OH)—CHOH—CH(OCHR.sub.1OH)—CH(OCHR.sub.1OH)—CH.sub.2—O—CHR.sub.1OH  (3),
OHCHR.sub.1—O—CH.sub.2—CH(OCHR.sub.1OH)—CHOH—CH(OCHR.sub.1OH)—CHOH—CH.sub.2—O—CHR.sub.1OH   (4),
and OH—CH.sub.2—CH(OCHR.sub.1OH)—CHOH—CH(OCHR.sub.1OH)—CHOH—CH.sub.2—O—CHR.sub.1OH   (5), wherein R.sub.1 is H or C.sub.1 to C.sub.9 alkyl.

16. The composition according to claim 1, wherein the reaction product III of an amine and formaldehyde corresponds to formula (6a) ##STR00009## wherein R is H or methyl, and n is 1 or 2.

17. The composition according to claim 1, wherein the reaction product III of an amine and formaldehyde corresponds to the formula (6b) ##STR00010## wherein each R.sup.2 is C.sub.1 to C.sub.4 alkyl or C.sub.2 to C.sub.4 hydroxy alkyl.

18. The composition according to claim 16, wherein the compound of formula 6a is 3,3′-methylenebis-5-methyl-oxazolidine.

19. The composition according to claim 1, wherein the reaction product III of an amine and formaldehyde is present in the composition in an amount from 1 wt.-% to 20 wt. %.

20. The composition according to claim 3, wherein the alkaline compound IV. is selected from the group consisting of IV(a). alkaline metal salts or alkaline earth metal salts, IV(b). ammonia; alkyl amines, aryl amines or alkylaryl amines, IV(c). hydroxy alkyl amines, hydroxy aryl amines or hydroxy alkylaryl amines, IV(d). multifunctional amines containing besides an amino group, at least one further functional group selected from the group consisting of amino groups, ether groups and acid groups or an ester, amide or salt thereof, and IV(e). mixtures of compounds of groups IV(a) to IV(c), wherein “alkyl” means C.sub.1 to C.sub.20 alkyl, “aryl” means C.sub.6 to C.sub.20 aryl and “alkylaryl” means C.sub.7 to C.sub.20 alkylaryl.

21. The composition according to claim 1, comprising 1 to 60 wt.-% of the reaction product between a monohydric alcohol and an aldehyde or ketone.

22. The composition according to claim 1, comprising 1 to 95 wt.-% of the reaction product between a sugar alcohol and an aldehyde or ketone.

23. The composition according to claim 1, wherein the molar ratio between the reaction product between a monohydric alcohol and an aldehyde or ketone (group I) and the reaction product between a sugar alcohol and an aldehyde or ketone (group II) is between 20:1 and 1:20.

24. The composition according to claim 2, wherein the ratio between the combined reaction products of group I and group II on the one hand side and the at least one reaction product from formaldehyde and ammonia and/or an amine of group III on the other hand side is between 1000:1 and 5:1.

25. Composition according to claim 1, comprising 0.1 to 15 wt. % of at least one solids suppression agent (group IV).

26. A composition comprising I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, II. at least one reaction product between a sugar alcohol and an aldehyde or ketone wherein the reaction products I. and II. are herniacetals and/or acetals, and an alkyl dimethyl benzyl ammonium chloride according to formula (9) as a corrosion inhibitor ##STR00011## wherein R.sup.9 is C.sub.8 to C.sub.18 alkyl.

27. The composition according to claim 26, wherein the compound of formula (9) is present in an amount between 0.01 and 5 wt. %.

28. A composition comprising I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, II. at least one reaction product between a sugar alcohol and an aldehyde or ketone wherein the reaction products I. and II. are hemiacetals and/or acetals, and a demulsifier in an amount between 0.1 to 10 wt. %.

29. The composition according to claim 28, wherein the demulsifier is selected from the group consisting of polysorbates, fatty alcohols, polymers comprising ethylene oxide, polymers comprising propylene oxide, ethylene oxide-propylene oxide copolymers, alkyl polyglucosides, alkylphenol ethoxylates, alkyl polyethylene oxide, alkylbenzenesulfonic acid and ethoxylated and/or propoxylated alkyl phenol-formaldehyde resins.

30. The composition according to claim 28, wherein the demulsifier corresponds to the formula (7) ##STR00012## wherein R.sub.10 is C.sub.2 to C.sub.4 alkylene, R.sub.11 is C.sub.1 to C.sub.18 alkyl, k is a number from 1 to 200, m is a number from 1 to 100.

31. The composition according to claim 28, wherein the demulsifier is dodecylbenezesulfonic acid (8) ##STR00013##

32. The composition according to claim 28, wherein the demulsifier is a mixture of at least one compound of formula (7) and at least one compound of formula (8) in a weight ratio of from 5:1 to 1:5.

33. A formulation, comprising 10 to 99 wt.-% of a composition according to claim 1, and 1 to 90 wt.-% of a solvent selected from the group consisting of water, methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, 2-butoxyethanol, glycerol and their mixtures.

34. A process for the scavenging of hydrogen sulphide and/or mercaptans, comprising the step of adding to a medium comprising such hydrogen sulphide or mercaptans a composition comprising I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, and II. at least one reaction product between a sugar alcohol and an aldehyde or ketone wherein the reaction products I. and II. are hemiacetals and/or acetals.

Description

EXAMPLES

(1) Preparation of Hemiacetals

(2) Method A (using paraformaldehyde, PFA): The amounts of alcohol and water given in table 1 were charged into a stirred reactor. 0.25 wt.-% (based on the mass of alcohols) of sodium hydroxide solution at 50 wt.-% was added. This mixture was homogenized for 10 minutes before paraformaldehyde (PFA, 93 wt.-%) was added in the amount given in table 1 over a period of approximately 30 minutes. The reaction mixture was warmed while stirring for 8 hours at a temperature between 80 to 85° C. After the reaction time, the mixture was cooled to 30° C.

(3) Method B (using aqueous formaldehyde, AFA): A stirred reactor was charged with the quantities of an aqueous solution of formaldehyde (AFA, 37 wt.-%) given in table 1. Then, amounts of alcohols given in table 1 were added followed by 0.25 wt.-% (based on the mass of alcohols) of sodium hydroxide solution at 50 wt.-%. This mixture was homogenized for 10 minutes before heating the stirred reaction mixture to a temperature between 80 to 85° C. for 8 hours. After the reaction time, the mixture was cooled to 30° C.

(4) The sugars were used as pure reagents; in examples A5, A11, A13 and A14 sorbitol was used as a 70 wt.-% active aqueous solution.

(5) The reaction products are characterized by the molar amounts of hemiacetal in respect to the total amount of hydroxyl groups charged and the content of free formaldehyde (CH.sub.2O) as determined by .sup.1H NMR spectroscopy.

(6) Further materials used were hexahydro-1,3,5-trimethyl-s-triazin (HTT) and 3,3′-methylenebis-5-methyloxazolidine (MBO) as the synergists according to group III. triethylamine (TEA), monoethanolamine (MEA), piperazine (PIP), 5 wt.-% aqueous solution of NaOH (NaOH), and the monosodium salt of glycine (GLY) as the solids suppressants according to group IV. All these materials were commercial grades.

(7) TABLE-US-00001 TABLE 1 Preparation of (hemi-)acetals reactor charge formaldehyde reaction product monohydric charge sugar charge water source; charge acetalized free CH.sub.2O (hemi-)acetal alcohol [g] alcohol [g] [g] [g] [mol-%] [wt.-%] A1 (comp.) methanol 500 — 0 0 PFA 500 98% 0.07 A2 (comp.) ethanol 600 — 0 0 PFA 420 99% 0.06 A3 (comp.) i-propanol 600 — 0 0 PFA 320 99% 0.08 A4 (comp.) 2-EH 800 — 0 0 PFA 200 98% 0.11 A5 (comp.) — 0 sorbitol (aq.) 692 0 AFA 1208 79% 0.07 A6 (comp.) — 0 xylitol 490 0 AFA 1046 77% 0.09 A7 (comp.) — 0 isomalt 1416 1513 PFA 955 65% 0.13 A8 (comp.) — 0 inositol 931 400 PFA 800 75% 0.08 A9 (comp.) — 0 mannitol 212 0 AFA 368 64% 0.09 A10 (comp.) — 0 erythritol 155 178 PFA 113 69% 0.05 A11 ethanol 23 sorbitol (aq.) 130 0 AFA 227 76% 0.07 A12 methanol 19 sorbitol 108 46 AFA 270 78% 0.06 A13 methanol 19 sorbitol (aq.) 154 170 PFA 107 78% 0.08 A14 methanol 19 sorbitol (aq.) 154 0 AFA 337 97% 0.05 A15 methanol 80 xylitol 380 143 PFA 387 77% 0.07 A16 methanol 45 isomalt 484 575 PFA 363 68% 0.14 A17 methanol 75 inositol 422 670 PFA 423 76% 0.08 A18 methanol 77 mannitol 438 688 PFA 434 77% 0.08 A19 methanol 86 erythritol 328 0 AFA 654 59% 0.10 A20 i-propanol 150 erythritol 305 0 AFA 608 56% 0.14 2-EH = 2-ethyl hexanol; (aq.) = aqueous solution, 70% active

(8) Scavenger Performance Tests—Efficiency

(9) In order to demonstrate the improved efficiency of the instant invention in removing sulfhydryl compounds compared to group I respectively group II compounds alone, the removal of H.sub.2S from an oil and from an oil/water mixture was measured.

(10) The oil used was a mixture of kerosene with 10% of xylene with zero bottom sediment and water (BS&W) to simulate oil field conditions.

(11) The oil/water mixture was a mixture of the oil described above and brine (in a 50:50 volume ratio of oil to aqueous phase) to mimic the efficiency in hydrated crude oil.

(12) In a 500 mL stirred autoclave (Parr reactor), 350 mL of the oil respectively the oil/brine mixture was de-aerated for 1 hour with N.sub.2, then saturated with a sour gas mixture of 0.2 wt.-% H.sub.2S and 99.8 wt.-% CO.sub.2, by purging this gas into the oil resp. oil/brine mixture with a flow rate of 0.6 L/min. After equilibration by the sour gas mixture, 1.000 ppm of the composition to be tested was injected into the autoclave by an HPLC pump.

(13) For reasons of better comparability of performance tests the compositions given in tables 2 and 3 containing (hemi-)acetal, synergist and/or solids suppressant as active materials, were applied as 50 wt.-% active formulations in water. The portions of (hemi-)acetal, synergist and solids suppressant given in tables 2, 3 and 4 refer to the portion of the respective component in the active material, therefore summing up to 100%. For preparation of the compositions given in tables 2, 3 and 4 the water content introduced during preparation of the (hemi-)acetals A1 to A20 according to table 1 was taken into account.

(14) The performance tests were carried out at 30° C. and under 1 bar, using a gas chromatograph to measure the outlet H.sub.2S content in the gas phase every two minutes. Then, a graph of the measured values of H.sub.2S content (ppm) versus time (min) was plotted. The amount of hydrogen sulfide scavenged is the area above the resultant performance curve, which is calculated by the integration of the curve. For all samples the integration of the curve was done up to 60 min after the injection of H.sub.2S-scavenger. As the output parameter of this performance test L.sub.sc/kgH.sub.2S (Liters of H.sub.2S scavenger required to remove 1 kg of H.sub.2S from the system) has been determined for 6 minutes and 1 hour of analysis. All consumption values (L.sub.sc/kgH.sub.2S) refer to the amount of 100% active composition consumed in the test and are averages of three repeat tests. The test results have been summarized in Table 2 and Table 3. Percentages mean weight percent if not indicated otherwise. Ratios in mixtures of (hemi-)acetals refer to mass portions of active material.

(15) TABLE-US-00002 TABLE 2 Performance tests for H.sub.2S-scavengers in oil (zero BS&W) solids (hemi)acetal synergist suppressant amount amount amount L.sub.SC/kg H.sub.2S example Type [wt %] Type [wt %] Type [wt %] @ 6 min. @ 1 hour P1 (comp.) A1 100 — 0 — 0 19.45 8.70 P2 (comp.) A2 100 — 0 — 0 20.76 9.56 P3 (comp.) A3 100 — 0 — 0 21.23 10.04 P4 (comp.) A5 100 — 0 — 0 19.62 9.23 P5 (comp.) A6 100 — 0 — 0 18.57 8.58 P6 (comp.) A7 100 — 0 — 0 20.08 10.35 P7 (comp.) A1 + A2 (1:1) 100 — 0 — 0 19.12 9.85 P8 (comp.) A5 + A6 (2:1) 100 — 0 — 0 17.68 9.05 P9 A1 + A5 (1:4) 100 — 0 — 0 14.56 7.45 P10 A2 + A5 (1:1) 100 — 0 — 0 14.77 7.53 P11 A3 + A6 (1:3) 100 — 0 — 0 14.06 7.43 P12 A3 + A7 (2:1) 100 — 0 — 0 14.78 7.72 P13 A11 100 — 0 — 0 12.22 6.43 P14 A12 100 — 0 — 0 12.05 6.32 P15 A15 100 — 0 — 0 12.43 6.71 P16 A1 + A5 (1:4) 93 — 0 MEA 7 11.79 6.06 P17 A2 + A5 (1:1) 93 — 0 GLY 7 11.65 5.99 P18 A3 + A7 (2:1) 95 — 0 NaOH 5 11.81 6.02 P19 A11 93 — 0 GLY 7 11.88 5.98 P20 A12 93 — 0 MEA 7 11.79 6.03 P21 A15 93 — 0 GLY 7 11.65 6.20 P22 A16 93 — 0 PIP 7 11.81 6.32 P23 (comp.) A1 98 MBO 2 — 0 6.22 4.73 P24 (comp.) A2 98 MBO 2 — 0 6.65 4.87 P25 (comp.) A5 98 MBO 2 — 0 5.32 4.43 P26 (comp.) A6 98 MBO 2 — 0 5.21 4.64 P27 A1 + A5 (1:4) 98 MBO 2 — 0 3.21 2.68 P28 A2 + A5 (1:1) 98 MBO 2 — 0 3.12 2.75 P29 A3 + A6 (1:3) 98 MBO 2 — 0 3.43 2.97 P30 A11 98 MBO 2 — 0 2.99 2.65 P31 A12 98 MBO 2 — 0 3.05 2.62 P32 A3 + A6 (1:3) 98 MBO 2 — 0 3.55 2.81 P33 A11 96 HTT 4 — 0 3.23 2.76 P34 A15 96 HTT 4 — 0 3.73 2.92 P35 A16 96 HTT 4 — 0 3.48 2.91 P36 (comp.) A1 93 MBO 2 MEA 5 4.85 4.13 P37 (comp.) A2 90 MBO 2 PIP 8 4.94 4.20 P38 (comp.) A3 88 MBO 2 TEA 10 8.02 6.78 P39 (comp.) A5 93 MBO 2 MEA 5 4.68 3.23 P40 (comp.) A6 90 MBO 2 GLY 8 4.75 3.26 P41 A1 + A5 (1:4) 93 MBO 2 MEA 5 2.25 1.99 P42 A2 + A5 (1:1) 93 MBO 2 MEA 5 2.41 2.07 P43 A3 + A7 (1:3) 88 MBO 2 TEA 10 2.60 2.31 P44 A11 93 MBO 2 MEA 5 2.20 1.87 P45 A12 93 MBO 2 MEA 5 2.13 1.85 P46 A3 + A6 (1:3) 90 MBO 2 PIP 8 2.55 2.28 P47 A12 89 HTT 4 GLY 7 2.15 1.84 P49 A13 89 HTT 4 GLY 7 2.43 1.90 P50 A13 89 HTT 4 MEA 7 2.47 1.92 P51 A15 89 HTT 4 GLY 7 2.36 1.83 P52 A15 89 HTT 4 MEA 7 2.34 1.85 P53 A16 89 HTT 4 GLY 7 2.40 1.89

(16) TABLE-US-00003 TABLE 3 Performance tests for H.sub.2S-scavenging in a mixture of the oil and brine (50:50 volume ratio of oil to aqueous phase) solids (hemi)acetal synergist suppressant amount amount amount L.sub.SC/kg H.sub.2S example type [wt %] type [wt %] type [wt %] @ 6 min. @ 1 hour P54 (comp.) A1 100 — 0 — 0 23.36 10.04 P55 (comp.) A2 100 — 0 — 0 23.82 10.20 P56 (comp.) A4 100 — 0 — 0 23.60 12.20 P57 (comp.) A5 100 — 0 — 0 22.78 9.31 P58 (comp.) A8 100 — 0 — 0 22.27 10.08 P59 (comp.) A9 100 — 0 — 0 23.07 10.32 P60 (comp.) A10 100 — 0 — 0 22.97 10.27 P61 (comp.) A1 + A2 (1:1) 100 — 0 — 0 21.87 9.95 P62 (comp.) A5 + A9 (2:1) 100 — 0 — 0 20.34 9.55 P63 A1 + A5 (1:4) 100 — 0 — 0 15.93 7.78 P64 A2 + A5 (1:1) 100 — 0 — 0 14.97 7.83 P65 A1 + A9 (1:3) 100 — 0 — 0 15.36 8.36 P67 A13 100 — 0 — 0 13.42 7.63 P68 A14 100 — 0 — 0 13.52 7.72 P69 A17 100 — 0 — 0 13.57 7.74 P70 A19 100 — 0 — 0 13.31 7.51 P71 A1 + A5 (1:4) 93 — 0 GLY 7 12.95 7.03 P72 A1 + A9 (1:3) 93 — 0 PIP 7 13.47 7.26 P73 A13 93 — 0 GLY 7 13.68 7.48 P74 A13 93 — 0 MEA 7 13.37 7.97 P75 A14 93 — 0 GLY 7 14.03 7.48 P76 A14 93 — 0 MEA 7 14.56 7.44 P77 A17 93 — 0 GLY 7 15.00 7.40 P78 A19 93 — 0 NaOH 5 14.81 7.62 P79 (comp.) A1 98 MBO 2 — 0 8.29 6.63 P80 (comp.) A2 98 MBO 2 — 0 8.40 6.88 P81 (comp.) A4 98 MBO 2 — 0 9.84 6.55 P82 (comp.) A5 98 MBO 2 — 0 8.56 6.80 P83 (comp.) A9 98 MBO 2 — 0 8.26 6.65 P84 A1 + A5 (1:4) 98 MBO 2 — 0 6.29 5.03 P85 A2 + A5 (1:1) 98 MBO 2 — 0 6.12 4.99 P86 A1 + A10 (1:3) 98 MBO 2 — 0 6.43 5.17 P87 A13 98 MBO 2 — 0 6.05 5.12 P88 A14 98 MBO 2 — 0 6.12 5.20 P89 A4 + A9 (1:3) 98 MBO 2 — 0 6.55 5.81 P90 A13 96 HTT 4 — 0 6.44 5.76 P91 A14 96 HTT 4 — 0 7.03 5.92 P92 A18 96 HTT 4 — 0 6.54 5.84 P93 (comp.) A1 88 MBO 2 MEA 10 6.52 5.56 P94 (comp.) A2 90 MBO 2 PIP 8 6.94 5.71 P95 (comp.) A4 88 MBO 2 TEA 10 6.75 5.49 P96 (comp.) A5 88 MBO 2 MEA 10 7.05 5.92 P97 (comp.) A10 90 MBO 2 PIP 8 6.75 5.57 P98 A1 + A5 (1:4) 93 MBO 2 MEA 5 4.25 3.82 P99 A2 + A5 (1:1) 93 MBO 2 MEA 5 4.31 3.90 P100 A4 + A19 (1:3) 88 MBO 2 TEA 10 4.60 4.01 P101 A13 93 MBO 2 MEA 5 4.24 3.80 P102 A14 93 MBO 2 MEA 5 4.27 3.85 P103 A4 + A9 (1:3) 90 MBO 2 PIP 8 4.85 3.94 P104 A10 89 HTT 4 GLY 7 4.15 3.75 P105 A13 89 HTT 4 GLY 7 4.53 3.89 P106 A13 91 HTT 4 NaOH 5 4.49 3.84 P107 A14 89 HTT 4 GLY 7 4.81 4.01 P108 A14 89 HTT 4 MEA 7 4.63 4.05 P109 A18 89 HTT 4 GLY 7 4.41 5.84 P110 A18 89 HTT 4 MEA 7 4.43 4.83 P111 A19 89 HTT 4 GLY 7 4.61 3.89 P112 A20 89 HTT 4 PIP 7 4.76 3.99

(17) In tables 2 and 3 the lower consumption of the scavenger to remove 1 kg of H.sub.2S, the more efficient is the scavenger. In the inventive examples the mixtures of acetals being based on mixtures of monohydric alcohols and sugar alcohols are more efficient than the single components. The efficiency is further improved by the incorporation of a synergist and/or a solids suppressant. Furthermore, incorporation of the synergist enhances the reaction rate in the initial phase of the test as can be seen from the difference between scavenging efficiency after 6 minutes versus 1 hour.

(18) Scavenger Performance Tests—Gas Breakthrough

(19) The performance of the H.sub.2S scavengers according to the invention was evaluated for their ability to remove H.sub.2S from a flowing gas stream by passing gas laden with H.sub.2S through a column of fluid containing the scavenger chemical. A sour gas mixture of 0.2% H.sub.2S and 99.8% CO.sub.2 is purged with a flow rate of 60 mL/min through 440 mL of a 22% active solution of the scavenger composition in water. Under these conditions the average contact time of gas and scavenger was about 4 seconds. Initially all of the H.sub.2S is removed from the gas stream and no H.sub.2S is detected in the effluent gas. At some point in time (the breakthrough time or TBT) the chemical can no longer entirely remove H.sub.2S from the gas stream and H.sub.2S is observed in the effluent. This parameter is a measure of the efficacy of the scavenger especially for contact tower applications with short contact time. The longer the break through time the more efficient is the chemical scavenger.

(20) The effect of the solids suppression agent is rated by visual inspection of the spent scavenger fluid after the gas breakthrough test. The degree of solids formation is rated opaque>turbid>opalescent>clear.

(21) The overall concentration of the scavenger formulations in all examples is 22 wt.-% (active ingredients), i. e. in examples where synergist and/or solids suppressant is present the concentration of (hemi-)acetals is reduced accordingly.

(22) TABLE-US-00004 TABLE 4 Gas breakthrough times for different (hemi-)acetals solids (hemi-)acetal synergist suppressant amount amount amount TBT visual example type [wt.-%] type [wt-%] type [wt-%] [min] inspection B1 (comp.) A1 100 — 0 — 0 31 opaque B2 (comp.) A2 100 — 0 — 0 29 opaque B3 (comp.) A5 100 — 0 — 0 19 opaque B4 (comp.) A7 100 — 0 — 0 29 opaque B5 (comp.) A10 100 — 0 — 0 54 opaque B6 (comp.) A1 + A2 (1:1) 100 — 0 — 0 31 opaque B7 (comp.) A5 + A7 (1:1) 100 — 0 — 0 35 opaque B8 A1 + A5 (1:1) 100 — 0 — 0 43 opaque B9 A1 + A5 (1:4) 100 — 0 — 0 46 opaque B10 A1 + A7 (1:4) 100 — 0 — 0 55 opaque B11 A2 + A10 (1:2) 100 — 0 — 0 49 opaque B12 A11 100 — 0 — 0 57 opaque B13 A12 100 — 0 — 0 56 opaque B14 A18 100 — 0 — 0 53 opaque B15 (comp.) A1 93 MBO 7 — 0 76 turbid B16 (comp.) A2 97 HTT 3 — 0 69 turbid B17 (comp.) A5 97 HTT 3 — 0 77 turbid B18 (comp.) A7 93 MBO 7 — 0 75 turbid B19 A1 + A5 (1:1) 97 HTT 3 — 0 85 turbid B20 A1 + A5 (1:4) 97 HTT 3 — 0 90 turbid B21 A11 97 HTT 3 — 0 88 turbid B22 A12 97 HTT 3 — 0 89 turbid B23 A13 93 MBO 7 — 0 88 turbid B24 A1 + A7 (1:4) 95 MBO 5 — 0 84 turbid B25 A2 + A10 (1:2) 95 HTT 5 — 0 83 turbid B26 A13 96 HTT 4 — 0 85 turbid B27 A14 96 HTT 4 — 0 87 turbid B28 A16 96 HTT 4 — 0 84 turbid B29 (comp.) A1 90 — 0 MEA 10 149 opalescent B30 (comp.) A2 85 — 0 PIP 15 146 opalescent B31 (comp.) A3 85 — 0 PIP 15 134 opalescent B32 (comp.) A5 85 — 0 PIP 15 153 opalescent B33 (comp.) A7 90 — 0 MEA 10 147 opalescent B34 A1 + A5 (1:1) 85 — 0 PIP 15 167 opalescent B35 A1 + A5 (1:4) 85 — 0 PIP 15 180 opalescent B36 A11 85 — 0 PIP 15 166 opalescent B37 A12 85 — 0 PIP 15 177 opalescent B38 A13 95 — 0 NaOH 5 167 opalescent B39 A13 93 — 0 MEA 7 165 opalescent B40 A14 93 — 0 GLY 7 158 opalescent B41 A14 93 — 0 MEA 7 159 opalescent B42 A16 90 — 0 MEA 10 172 opalescent B43 A1 + A7 (1:4) 85 — 0 PIP 15 170 opalescent B44 A2 + A7 (1:2) 85 — 0 PIP 15 161 opalescent B45 A19 93 — 0 GLY 7 169 opalescent B46 (comp.) A1 83 MBO 7 MEA 10 215 clear B47 (comp.) A2 82 HTT 3 PIP 15 200 clear B48 (comp.) A3 90 HTT 5 PIP 15 192 clear B49 (comp.) A5 82 HTT 3 PIP 15 221 clear B50 (comp.) A7 83 MBO 7 MEA 10 219 clear B51 A1 + A5 (1:1) 82 HTT 3 PIP 15 258 clear B52 A1 + A5 (1:4) 82 HTT 3 PIP 15 288 clear B53 A11 82 HTT 3 PIP 15 305 clear B54 A12 82 HTT 3 PIP 15 310 clear B55 A12 83 MBO 7 MEA 10 300 clear B56 A1 + A7 (1:4) 80 MBO 5 PIP 15 299 clear B57 A2 + A10 (1:2) 80 HTT 5 PIP 15 295 clear B58 A10 89 HTT 4 GLY 7 320 clear B59 A13 89 HTT 4 GLY 7 311 clear B60 A13 89 HTT 4 MEA 7 309 clear B61 A14 89 HTT 4 GLY 7 295 clear B62 A14 91 HTT 4 NaOH 5 297 clear B63 A19 89 HTT 4 MEA 7 298 clear

(23) A comparison of the inventive examples and the comparative examples shows that mixtures of (hemi-)acetals containing reaction products of monohydric and sugar alcohols have a higher TBT than the single components or mixtures of components of the same group. The addition of a synergist according to group III increases the H.sub.2S scavenging activity of (hemi-)acetals and especially of mixtures of (hemi-)acetals significantly. The scavenging process becomes faster and more efficient. The addition of a solids suppressant further significantly improves the performance of the scavenger. Formation of solids is mostly inhibited which otherwise hampers the accessibility of part of the scavenger and furthermore bears the risk of clogging flow lines for the effluent. The enhancement in scavenging efficiency exceeds the stoichiometric H.sub.2S scavenging capacity of the added synergist considerably.