Synergized acetals 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 monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms 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 process for the scavenging of hydrogen sulphide and/or mercaptans, comprising the step of adding to a medium comprising the 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 monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone having one or two carbon atoms, wherein the reaction products (I) and (II) are hemiacetals and/or acetals.

2. The process according to claim 1, further comprising adding (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 process according to claim 1, further comprising adding (IV) at least one inorganic or organic alkaline compound that functions as a solids suppression agent.

4. The process according to claim 1, wherein the aldehyde or ketone for the reaction with the monohydric alcohol (I) contains 1 to 10 carbon atoms.

5. The process according to one claim 1, wherein the aldehyde or ketone for the reaction with the monohydric alcohol (I) is selected from the group consisting of formaldehyde, paraformaldehyde, glyoxal, acetaldehyde, propionaldehyde, butyraldehyde and glutaraldehyde.

6. The process according to claim 1, wherein the formaldehyde for the reaction with the monosaccharide having 3 to 6 carbon atoms and/or the oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms (group II) is selected from the group consisting of formaldehyde, paraformaldehyde, acetaldehyde and glyoxal.

7. The process according to claim 1, wherein the aldehyde or ketone for both components (group I) and (group II) is formaldehyde.

8. The process according to claim 1, wherein the monohydric alcohol comprises 1 to 15 carbon atoms.

9. The process according to claim 1, wherein the monohydric alcohol is an aliphatic alcohol.

10. The process 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.

11. The process according to claim 1, wherein the monosaccharide having 3 to 6 carbon atoms and/or the oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms is a monosaccharide having 3 to 6 carbon atoms.

12. The process according to claim 1, wherein the monosaccharide is a linear polyhydroxycarbonyl compound having the general formula (1)
C.sub.n(H.sub.2O).sub.n  (1) wherein n is an integer between 3 and 6.

13. The process according to claim 12 wherein n is between 4 and 6.

14. The process according to claim 13 wherein n is 5 or 6.

15. The process according to claim 1, wherein the monosaccharide is a polyhydroxyaldehyde of formula (2)
CHO—(CH—OH).sub.m—CH.sub.2OH  (2) wherein m is 1, 2, 3 or 4.

16. The process according to claim 1, wherein the monosaccharide is a polyhydroxyketone of formula (3)
HO—CH.sub.2—C(═O)—(CH—OH).sub.p—CH.sub.2OH  (3) wherein p is 0, 1, 2 or 3.

17. The process according to claim 1, wherein the monosaccharide is a mixture of open-chain and cyclic form of the polyhydroxyaldehyde of formula (2) and the polyhydroxyketone according to formula (3).

18. The process according to claim 1, wherein the monosaccharide is selected from the group consisting of glucose, mannose, galactose, ribose, arabinose, xylose and fructose.

19. The process according to claim 1, wherein the monosaccharide having 3 to 6 carbon atoms and/or the oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms is an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms.

20. The process according to claim 1, wherein the oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms is a disaccharide being formed by dimerization of monosaccharides having 3 to 6 carbon atoms.

21. The process according to claim 20, wherein the disaccharide formed by oligomerization of monosaccharides having 3 to 6 carbon atoms has the general formula (4)
C.sub.y(H.sub.2O).sub.y-1  (4) wherein y is 10, 11 or 12.

22. The process according to claim 20, wherein the disaccharide is formed from aldoses and/or ketoses having 5 or 6 carbon atoms which are linked by a glycosidic linkage.

23. The process according to one or more of claim 19, wherein the oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms is selected from maltose, Isomaltose, cellobiose, trehalose, sucrose, isomaltulose, trehalulose, lactose, lactulose and raffinose.

24. The process according to claim 2, wherein the reaction product (III) of ammonia or an amine and formaldehyde corresponds to formula (7a) ##STR00009## wherein R is H or methyl, and n is 1 or 2.

25. The process according to claim 2, wherein the reaction product (III) of an amine and formaldehyde corresponds to the formula (7b) ##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.

26. The process according to claim 24, wherein the compound of formula 7a is 3,3′-methylenebis-5-methyl-oxazolidine.

27. The process according to one or more of claim 2, wherein the reaction product (III) of an amine and formaldehyde is present in the composition in an amount from 1 wt.-% to 20 wt.-%.

28. The process 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 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.

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

30. The process according to claim 1, comprising 1 to 95 wt.-% of the reaction product between a monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone.

31. The process 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 monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms and an aldehyde having one or two carbon atoms (group II) is between 20:1 and 1:20.

32. The process according to claim 2, wherein the weight ratio between the combined reaction products of groups (I) and group (II) on the one hand side and the synergist (group III) on the other hand side is between 1000:1 and 5:1.

33. The process according to claim 3, comprising 0.1 to 15 wt.-% of at least one solids suppression agent (group IV).

34. The process according to claim 1, further comprising an alkyl dimethyl benzyl ammonium chloride according to formula (10) in an amount between 0.01 and 5 wt.-% ##STR00011## wherein R.sup.9 is C.sub.8 to C.sub.18 alkyl.

35. The process according to claim 1, further comprising a demulsifier in an amount between 0.1 to 10 wt.-%.

36. The process according to claim 35, 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.

37. The process according to claim 35, wherein the demulsifier corresponds to the formula (8) ##STR00012## wherein R.sub.10 is C.sub.2 to C.sub.4 alkylene, R.sub.11 is C.sub.1 to Cis alkyl, k is a number from 1 to 200, m is a number from 1 to 100.

38. The process according to claim 35, wherein the demulsifier is dodecylbenezesulfonic acid (9) ##STR00013##

39. The process according to claim 35, wherein the demulsifier is a mixture of at least one compound of formula (8) and at least one compound of formula (9) in a weight ratio of from 5:1 to 1:5, preferably in a weight ratio of from 3:1 to 1:3.

40. A process for the scavenging of hydrogen sulphide and/or mercaptans, comprising adding to a medium comprising such hydrogen sulphide or mercaptans a formulation comprising 10 to 99 wt.-% of 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 monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone having one or two carbon atoms, wherein the reaction products I. and II. are hemiacetals and/or acetals, 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.

Description

EXAMPLES

Preparation of Hemiacetals

(1) Method A (using paraformaldehyde, PFA): The amounts of alcohols and/or sugars 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.

(2) 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 and/or sugars 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.

(3) 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.

(4) 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.

(5) TABLE-US-00001 TABLE 1 Preparation of (hemi-)acetals reactor charge reaction product monohydric water formaldehyde acetalized CH.sub.2O (hemi-)acetal alcohol charge [g] sugar charge [g] [g] source charge [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 glucose 780 0 AFA 1036 76    0.07 A6 (comp.) — 0 sucrose 1033 988 PFA 624 71    0.12 A7 (comp.) — 0 xylose 694 0 AFA 1200 73    0.09 A8 methanol 128 glucose 721 982 PFA 620 79    0.05 A9 methanol 64 sucrose 685 736 PFA 464 75    0.10 A10 methanol 80 xylose 375 511 PFA 323 74    0.06 A11 methanol 96 fructose 772 0 AFA 877 58    0.07 A12 methanol 96 lactose 1027 500 PFA 872 95    0.11 A13 ethanol 157 lactose 1663 0 AFA 1738 67    0.09 2-EH = 2-ethyl hexanol

(6) Scavenger Performance Tests—Efficiency

(7) 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.

(8) 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.

(9) 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.

(10) 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, 1000 ppm of the composition to be tested was injected into the autoclave by an HPLC pump.

(11) 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 aqueous formulations. 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 A13 according to table 1 was taken into account.

(12) 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 the mass portions of active material.

(13) 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 19.53 9.43 P5 (comp.) A6 100 — 0 — 0 19.10 9.53 P6 (comp.) A1 + A2 100 — 0 — 0 19.12 9.85 (1:1) P7 (comp.) A5 + A6 100 — 0 — 0 18.87 9.06 (1:1) P8 A1 + A5 100 — 0 — 0 14.56 7.80 (1:1) P9 A1 + A6 100 — 0 — 0 15.18 7.59 (1:2) P10 A2 + A5 100 — 0 — 0 15.21 8.07 (1:3) P11 A8 100 — 0 — 0 13.61 7.01 P12 A9 100 — 0 — 0 13.43 6.93 P13 (comp.) A1 98 MBO 2 — 0 5.31 4.22 P14 (comp.) A2 98 MBO 2 — 0 5.65 4.63 P15 (comp.) A3 98 MBO 2 — 0 5.86 4.86 P16 (comp.) A5 98 MBO 2 — 0 5.52 4.67 P17 (comp.) A6 98 MBO 2 — 0 5.37 4.49 P18 A1 + A5 98 MBO 2 — 0 3.27 2.94 (1:1) P19 A1 + A6 98 MBO 2 — 0 3.98 3.00 (1:2) P20 A2 + A6 98 MBO 2 — 0 3.95 2.97 (1:3) P21 A3 + A5 98 MBO 2 — 0 4.01 3.06 (1:3) P22 A8 96 HTT 4 — 0 3.40 3.01 P23 A9 96 HTT 4 — 0 3.35 2.98 P24 A12 96 HTT 4 — 0 3.16 2.72 P25 (comp.) A1 93 — 0 GLY 7 3.10 2.70 P26 (comp.) A2 93 — 0 MEA 7 3.23 2.87 P27 (comp.) A5 95 — 0 NaOH 5 3.17 2.84 P28 (comp.) A6 93 — 0 PIP 7 3.45 2.93 P29 A1 + A5 93 — 0 GLY 7 3.23 2.83 (1:1) P30 A8 93 — 0 GLY 7 3.09 2.90 P31 A8 95 — 0 NaOH 5 3.16 2.92 P32 A9 93 — 0 PIP 7 3.25 2.89 P33 A9 93 — 0 MEA 7 3.38 3.04 P34 (comp.) A1 93 MBO 2 MEA 5 4.46 3.93 P35 (comp.) A2 90 MBO 2 PIP 8 4.76 4.06 P36 (comp.) A3 88 MBO 2 TEA 10 4.80 4.12 P37 (comp.) A5 93 MBO 2 MEA 5 4.53 3.87 P38 (comp.) A6 90 MBO 2 PIP 8 4.38 3.62 P39 A1 + A5 93 MBO 2 MEA 5 2.65 2.36 (1:1) P40 A1 + A6 93 MBO 2 MEA 5 2.30 2.08 (1:2) P41 A2 + A5 88 MBO 2 TEA 10 2.78 2.48 (1:2) P42 A3 + A6 93 MBO 2 MEA 5 2.89 2.31 (1:3) P43 A8 93 MBO 2 MEA 5 2.38 2.21 P44 A8 89 HTT 4 GLY 7 2.37 2.09 P46 A8 91 HTT 4 NaOH 5 2.40 2.11 P47 A9 89 HTT 4 PIP 7 2.41 2.23 P48 A9 89 HTT 4 MEA 7 2.39 2.17 P49 A11 89 HTT 4 GLY 7 2.47 2.19 P50 A12 89 HTT 4 GLY 7 2.38 2.10

(14) 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 P51 (comp.) A1 100 — 0 — 0 23.36 10.04 P52 (comp.) A2 100 — 0 — 0 23.82 10.20 P53 (comp.) A4 100 — 0 — 0 28.51 14.21 P54 (comp.) A5 100 — 0 — 0 22.64 9.84 P55 (comp.) A7 100 — 0 — 0 21.84 9.21 P56 (comp.) A1 + A2 100 — 0 — 0 21.87 9.95 (1:1) P57 A1 + A5 100 — 0 — 0 18.97 7.99 (1:1) P58 A1 + A7 100 — 0 — 0 19.14 8.05 (1:3) P59 A4 + A7 100 — 0 — 0 19.46 8.11 (1:1) P60 A2 + A5 100 — 0 — 0 19.21 8.07 (1:1) P61 A8 100 — 0 — 0 18.75 7.94 P62 A10 100 — 0 — 0 18.81 7.96 P63 A11 100 — 0 — 0 18.72 8.01 P64 (comp.) A1 94 HTT 6 — 0 8.76 7.04 P65 (comp.) A2 98 MBO 2 — 0 8.40 6.88 P66 (comp.) A4 98 HTT 2 — 0 8.45 7.12 P67 (comp.) A5 98 MBO 2 — 0 8.56 6.96 P68 (comp.) A7 94 HTT 6 — 0 8.63 7.01 P69 A1 + A5 98 MBO 2 — 0 7.95 6.84 (1:1) P70 A1 + A7 94 HTT 6 — 0 8.03 6.99 (2:1) P71 A4 + A7 94 HTT 6 — 0 7.86 6.91 (1:3) P72 A2 + A5 98 MBO 2 — 0 7.94 6.90 (1:2) P73 A8 94 HTT 6 — 0 7.77 6.84 P74 A10 98 MBO 2 — 0 7.83 6.72 P75 A10 94 HTT 6 — 0 7.71 6.76 P76 (comp.) A1 95 — 0 NaOH 5 7.56 6.66 P77 (comp.) A2 93 — 0 GLY 7 7.62 6.71 P78 (comp.) A4 93 — 0 MEA 7 7.70 6.78 P79 (comp.) A5 93 — 0 GLY 7 7.63 6.70 P80 (comp.) A7 93 — 0 PIP 7 7.68 6.73 P81 A8 93 — 0 GLY 7 7.60 6.69 P82 A8 93 — 0 MEA 7 7.61 6.70 P83 A10 93 — 0 GLY 7 7.64 6.63 P84 A10 93 — 0 MEA 7 7.62 6.65 P85 A13 90 — 0 TEA 10 7.84 6.82 P86 A2 + A5 90 — 0 MEA 10 7.60 6.67 (1:4) P87 A10 90 — 0 MEA 10 7.61 6.65 P88 (comp.) A1 89 HTT 6 NaOH 5 6.91 5.72 P89 (comp.) A2 88 MBO 2 MEA 10 6.52 5.56 P90 (comp.) A5 88 MBO 2 MEA 10 7.05 5.92 P91 (comp.) A7 89 HTT 6 NaOH 5 7.06 5.95 P92 A1 + A5 88 MBO 2 MEA 10 6.95 5.62 (1:1) P93 A1 + A7 89 HTT 6 NaOH 5 6.97 5.78 (2:1) P94 A4 + A7 89 HTT 6 NaOH 5 7.00 5.94 (1:3) P95 A2 + A5 89 HTT 4 GLY 7 6.63 5.60 (1:2) P96 A8 89 HT 6 NaOH 5 6.57 5.59 P97 A8 89 HTT 4 GLY 7 6.53 5.54 P98 A8 89 HTT 4 MEA 7 6.55 5.56 P99 A9 91 HTT 4 NaOH 5 6.71 5.60 P100 A9 89 HTT 4 PIP 7 6.69 5.63 P101 A10 88 MBO 2 MEA 10 6.60 5.59 P102 A10 89 HTT 4 GLY 7 6.58 5.53 P103 A10 89 HTT 4 PIP 7 6.56 5.50 P104 A12 89 HTT 6 NaOH 5 6.50 5.49 P105 A13 89 HTT 6 NaOH 5 6.66 5.67

(15) 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 a monohydric alcohols and a monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms 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.

(16) Scavenger Performance Tests—Gas Breakthrough

(17) 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 was 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.

(18) 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.

(19) 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.

(20) 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.) A3 100 — 0 — 0 27 opaque B4 (comp.) A5 100 — 0 — 0 30 opaque B5 (comp.) A6 100 — 0 — 0 31 opaque B6 (comp.) A7 100 — 0 — 0 29 opaque B7 (comp.) A1 + A2 100 — 0 — 0 35 opaque (1:1) B8 (comp.) A5 + A7 100 — 0 — 0 37 opaque (1:1) B9 A1 + A5 100 — 0 — 0 38 opaque (1:1) B10 A1 + A7 100 — 0 — 0 34 opaque (2:1) B11 A2 + A7 100 — 0 — 0 37 opaque (1:3) B12 A3 + A7 100 — 0 — 0 36 opaque (1:2) B13 A8 100 — 0 — 0 45 opaque B14 A9 100 — 0 — 0 38 opaque B15 A10 100 — 0 — 0 43 opaque B16 A11 100 — 0 — 0 42 opaque B17 A12 100 — 0 — 0 39 opaque B18 A13 100 — 0 — 0 37 opaque B19 (comp.) A1 93 MBO 7 — 0 76 turbid B20 (comp.) A2 97 HTT 3 — 0 69 turbid B21 (comp.) A3 95 HTT 5 — 0 68 turbid B22 (comp.) A5 97 HTT 3 — 0 75 turbid B23 (comp.) A6 93 MBO 7 — 0 70 turbid B24 (comp.) A7 93 MBO 7 — 0 73 turbid B25 A1 + A5 97 HTT 3 — 0 78 turbid (1:1) B26 A1 + A6 97 HTT 3 — 0 74 turbid (2:1) B27 A2 + A7 95 MBO 5 — 0 79 turbid (1:3) B28 A3 + A5 95 HTT 5 — 0 76 turbid (1:2) B29 A8 96 HTT 4 — 0 80 turbid B30 A9 96 HTT 4 — 0 76 turbid B31 A10 96 HTT 4 — 0 77 turbid B32 A12 97 HTT 3 — 0 78 turbid B33 A13 93 MBO 7 — 0 75 turbid B34 (comp.) A1 90 — 0 MEA 10 149 opalescent B35 (comp.) A2 85 — 0 PIP 15 146 opalescent B36 (comp.) A3 85 — 0 PIP 15 134 opalescent B37 (comp.) A5 85 — 0 PIP 15 140 opalescent B38 (comp.) A5 93 — 0 GLY 7 143 opalescent B39 (comp.) A7 90 — 0 MEA 10 142 opalescent B40 A1 + A5 85 — 0 PIP 15 146 opalescent (1:1) B41 A1 + A6 85 — 0 PIP 15 140 opalescent (2:1) B42 A2 + A7 85 — 0 PIP 15 144 opalescent (1:3) B43 A3 + A5 85 — 0 PIP 15 145 opalescent (1:2) B42 A8 93 — 0 GLY 7 149 opalescent B43 A8 93 — 0 MEA 7 147 opalescent B44 A9 95 — 0 NaOH 5 145 opalescent B45 A9 93 — 0 TEA 7 143 opalescent B46 A10 93 — 0 GLY 7 148 opalescent B47 A10 93 — 0 PIP 7 145 opalescent B38 A11 85 — 0 PIP 15 146 opalescent B39 A12 90 — 0 MEA 10 143 opalescent B48 (comp.) A1 83 MBO 7 MEA 10 215 clear B49 (comp.) A2 82 HTT 3 PIP 15 200 clear B50 (comp.) A3 90 HTT 5 PIP 15 192 clear B51 (comp.) A5 82 HTT 3 PIP 15 203 clear B51 (comp.) A6 90 HTT 3 GKY 7 193 clear B52 (comp.) A7 83 MBO 7 MEA 10 201 clear B53 A1 + A5 82 HTT 3 PIP 15 210 clear (1:1) B54 A1 + A6 82 HTT 3 PIP 15 201 clear (2:1) B58 A2 + A7 80 MBO 5 PIP 15 202 clear (1:3) B59 A3 + A5 80 HTT 5 PIP 15 200 clear (1:2) B60 A8 89 HTT 4 GLY 7 217 clear B61 A8 89 HTT 4 MEA 7 214 clear B62 A9 89 HTT 4 TEA 7 203 clear B63 A9 89 HTT 4 PIP 7 207 clear B64 A10 91 HTT 4 NaOH 5 215 clear B56 A11 82 HTT 3 PIP 15 208 clear B57 A12 83 MBO 7 MEA 10 210 clear

(21) A comparison of the inventive examples and the comparative examples shows that mixtures of (hemi-)acetals containing reaction products of a monohydric alcohol and a monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms 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.