| US5220104A | 1993-06-15 | |||
| US5160425A | 1992-11-03 | |||
| US4575455A | 1986-03-11 | |||
| EP0299166A1 | 1989-01-18 | |||
| GB1271331A | 1972-04-19 | |||
| GB1089388A | 1967-11-01 | |||
| US3725208A | 1973-04-03 |
PATENT ABSTRACTS OF JAPAN vol. 011, no. 202 (C - 432) 30 June 1987 (1987-06-30)
DATABASE WPI Section Ch Week 8524, Derwent World Patents Index; Class E19, AN 85-145018, XP002011803
| 1. | A method for inhibiting aldol condensation in monoethanolamine scrubbers comprising the step of treating a monoethanolamine solution with an inhibiting agent in an amount sufficient to 5 inhibit said aldol condensation, wherein said inhibiting agent is selected from the group consisting of hydroperoxides, hydrogen peroxide, and dialkylketone oximes. |
| 2. | A method for inhibiting aldol condensation in monoethanolamine scrubbers comprising the step of treating a ι o monoethanolamine scrubber solution with an inhibiting agent in an amount sufficient to inhibit said aldol condensation, wherein said inhibiting agent comprises a hydrazine. |
| 3. | The method of claim 2 wherein said hydrazine generally has the following structure: 15 R2NNH2 wherein R is independently selected from the group consisting of a hydrogen, a straight, branched, or cyclic alkyl group having between about 18 carbon atoms, an aryi group, an alkaryl group, and an aralkyl group. 20 4. |
| 4. | The method of claim 1 wherein said inhibiting agent comprises a hydroperoxide. |
| 5. | The method of claim 4 wherein said hydroperoxide is selected from the group consisting of tertiarybutyl hydroperoxide and cumene hydroperoxide. |
| 6. | The method of claim 1 wherein said inhibiting agent comprises hydrogen peroxide. |
| 7. | The method of claim 1 wherein said inhibiting agent comprises a dialkyi ketone oxime wherein said alkyl groups are selected from the group consisting of straight, branched, and cyclic alkyl groups having between about 18 carbon atoms. |
| 8. | The method of claim 7 wherein said dialkyi ketone oxime comprises 2butanone oxime. |
| 9. | The method of claim 1 wherein said hydrocarbon stream contains a molar concentration of reactive carbonyls, and wherein said hydrocarbon stream is treated with a molar amount of said inhibiting agent that is at least substantially the same as said molar amount of said reactive carbonyls. |
| 10. | The method of claim 2 wherein said hydrocarbon stream contains a molar concentration of reactive carbonyls, and wherein said hydrocarbon stream is treated with a molar amount of said inhibiting agent that is at least substantially the same as said molar amount of said reactive carbonyls. |
| 11. | The method of claim 4 wherein said hydrocarbon stream contains a molar concentration of reactive carbonyls, and wherein said hydrocarbon stream is treated with a molar amount of said inhibiting agent that is at least substantially the same as said molar amount of said reactive carbonyls. |
| 12. | The method of claim 6 wherein said hydrocarbon stream contains a molar concentration of reactive carbonyls, and wherein said hydrocarbon stream is treated with a molar amount of said inhibiting agent that is at least substantially the same as said molar amount of said reactive carbonyls. |
| 13. | The method of claim 7 wherein said hydrocarbon stream contains a molar concentration of reactive carbonyls, and wherein said hydrocarbon stream is treated with a molar amount of said inhibiting agent that is at least substantially the same as said molar amount of said reactive carbonyls. |
| 14. | A monoethanolamine scrubbing solution comprising an inhibiting agent in an amount sufficient to inhibit aldol condensation, wherein said inhibiting agent is selected from the group consisting of a hydrazine, hydroperoxides, hydrogen peroxide, and dialkylketone oximes. |
| 15. | The monoethanolamine scrubbing solution of claim 12 wherein said inhibiting agent comprises a hydrazine. |
| 16. | The monoethanolamine scrubbing solution of claim 12 wherein said hydrazine generally has the following structure: R2NNH2 wherein R is independently selected from the group consisting of a hydrogen, a straight, branched, or cyclic alkyl group having between about 18 carbon atoms, an aryl group, an alkaryl group, and an aralkyl group. |
| 17. | The monoethanolamine scrubbing solution of claim 12 wherein said inhibiting agent comprises a hydroperoxide. |
| 18. | The monoethanolamine scrubbing solution of claim 17 wherein said hydroperoxide is selected from the group consisting of tertiarybutyl hydroperoxide and cumene hydroperoxide. |
| 19. | The monoethanolamine scrubbing solution of claim 12 wherein said inhibiting agent comprises hydrogen peroxide. |
| 20. | The monoethanolamine scrubbing solution of claim 12 wherein said inhibiting agent comprises a dialkyi ketone oxime wherein said alkyl groups are selected from the group consisting of straight, branched, and cyclic alkyl groups having between about 18 carbon atoms. baker\367\pto\01.mor. |
SCRUBBERS
Field of the Invention
The present invention relates to the use of inhibiting agents to reduce fouling caused by aldol condensation in monoethanolamine (MEA) scrubbers Such agents include hydrazines, hydroperoxides, hydrogen peroxide, and dialkylketone oximes. Preferred inhibiting agents are hydrazines
Background of the Invention
Refineries employ atmospheric and vacuum distillation towers to separate crude oil into narrower boiling fractions These fractions then are converted into fuel products, such as motor gasoline, distillate fuels (diesel and heating oils), and bunker (residual) fuel oils Some of the low boiling fractions from various units of the refinery are directed to petrochemical plants, where they are further processed into highly refined chemical feedstocks to be used as raw materials in the manufacture of other types of products, such as plastics and basic chemicals
During the refining of petroleum, hydrocarbon streams typically are treated in an amme scrubber, such as a DEA or MEA scrubber, to remove acid gases, such as hydrogen sulfide and carbon dioxide In a petrochemical plant, hydrocarbon streams typically are treated for the same purpose in a caustic scrubber All of these scrubbers herein are referred to as "acid gas" scrubbers The hydrocarbon stream entering an acid gas scrubber may contain aldehydes and ketones, their precursors, such as vinyl acetate, or other impurities, that are hydrolyzed or otherwise converted to aldehydes and salts of organic acids in the
highly alkaline environment of an acid gas scrubber. Such compounds will herein be referred to as "reactive compounds." These reactive compounds either (a) contain carbonyls, or (b) form carbonyls under highly alkaline conditions that are susceptible to classic aldol condensation reactions. Carbonyls that are susceptible to classic aldol condensation reactions hereinafter will be referred to as "reactive carbonyls."
Under highly alkaline conditions, lower molecular weight aldehydes, such as propionaldehyde (propanal) and especially acetaldehyde (ethanal), readily undergo base catalyzed aldol condensation at ambient temperatures. The result is the formation of oligomers and polymers which precipitate out of the scrubbing solution as viscous oils, polymeric gums, and solids. These precipitates can foul the processing equipment and result in the reduction of processing throughput and costly equipment maintenance or repair.
In the past, organic reducing agents or organic and inorganic oxidizing agents have been proposed to prevent such polymerization. These organic agents might successfully retard polymerization in acid gas scrubbers; however, the organic agents also tend to undergo other reactions which can reduce their effectiveness as aldol condensation inhibitors.
Effective and economical methods for retarding aldol condensation in monoethanolamine scrubbers would be highly desirable.
Summary of the Invention
The present invention provides a large number of inhibiting agents that are useful to reduce aldol condensation in monoethanolamine scrubbers.
Suitable agents include hydrazine, hydroperoxides, hydrogen peroxide, and dialkylketone oximes. Preferred inhibiting agents are hydrazines. Detailed Description of the Invention
The present invention is directed to reactions that cause fouling in monoethanolamine scrubbers. Without limiting the present invention, it is believed that the red precipitate that forms in acid gas scrubbers is the result of several aldol condensation/dehydration steps. As used herein, the term "aldol condensation" is intended to refer to the reactions that ultimately result in the formation of a precipitate in acid gas scrubbers. The inhibiting agents of the present invention are believed to inhibit fouling by inhibiting such aldol condensation.
Suitable inhibiting agents for MEA scrubbers include hydrazines, hydroperoxides, hydrogen peroxide, and dialkylketone oximes. Preferred inhibiting agents are hydrazines. Substantially any hydrazine should function in the present invention.
Suitable hydrazines generally have the following structure:
R 2 N-NH 2 wherein R is independently selected from a hydrogen, a straight, branched, or cyclic alkyl group having between about 1-8 carbon atoms, an aryl group, an alkaryl group, or an aralkyl group. Hydrazine is commercially available from Elf Atochem North America, Inc., 2000 Market Street, Philadelphia, PA.
Preferred hydroperoxides are commercially available hydroperoxides, such as tertiary-butyl and cumene hydroperoxide, which may be obtained from Elf Atochem North America, Inc.
A preferred form of hydrogen peroxide is a 30% solution of hydrogen peroxide, which may be obtained commercially from EM Science, a division of
EM Industries, Inc., 5 Skyline Drive, Hawthorne, NY, and Elf Atochem North America, Inc.
Suitable dialkyl ketone oximes are those in which the alkyl groups are selected from the group consisting of straight, branched, and cyclic alkyl groups having between about 1-8 carbon atoms. A preferred dialkylketone oxime is 2- butanone oxime, which may be obtained commercially from AlliedSignal, Inc.,
Morrison, NJ.
Preferably, the inhibiting agent should be injected into the scrubber slowly, on an "as-needed" basis. Due to substantially continuous mode of operation of most scrubbers, it is believed that the agent should reach a steady state during processing. An equimolar ratio of inhibiting agent to active carbonyl containing compound should be sufficient to inhibit aldol condensation. Even less than a 1:1 ratio may be sufficient. An excess of inhibiting agent also may be added, if desired. The agents of the present invention will react with the reactive carbonyls, or a condensation product of two or more reactive carbonyls, in the acid gas scrubber at ambient temperatures. Therefore, the hydrocarbon stream need not be heated In the following examples, the samples are heated to between about
50-55°C (122-131°F) to hasten the polymerization reaction for facile candidate evaluation. In actual use, heating is neither necessary nor advisable.
The invention will be more readily understood with reference to the following examples. Example 1
A number of screening tests were performed to ascertain agents that would reduce aldol condensation and/or oligomerization in MEA scrubbers. To perform the screening, 2 oz. bottles were dosed with 1.5 g or 1.5 ml of candidate- -an amount in excess of 1.1 mmoles of candidate for every 1.0 mmole of vinyl acetate. As seen below, the dosage of vinyl acetate that was added to each bottle is 600 ml (6.51 mmoles).
After dosing with the candidate, 25 ml of MEA in NaCI saturated water (to render the aldol condensation product less soluble) was added to each bottle, and the bottles were shaken 100 times. Subsequently, 600 ml of vinyl acetate
(560 mg, or 6.51 mmoles) was added to each bottle. The bottles were shaken 50 times, and placed in an oven at 50-55°C (122-131 °F) and observed after 24 hours for color and precipitate. Candidates that exhibited no color, or only slight color, and no precipitation were selected for further study. Approximately 26 candidates were selected for further testing.
EXAMPLE 2 The procedures of Example 1 were followed to test 26 candidates except that an exact mole ratio of candidate: vinyl acetate of 1.1 was used in each case,
case.except for candidates 1 and 11. The amount of candidate added to each bottle is given in Table I: TABLE I
SAMPLE CANDIDATE SOURCE MW AMT. OF MMOLES OF CANDI¬ CANDIDATE DATE ADDED (mg)
1 70% tertiary- butyl Arco 90 1 ,610 12.5 hydro-peroxide Chemical
Co.
2 H 2 N-NH 2 Aid rich 32 229 7.16
Chemical
Co.
3 Benzyl isothi-uronium Synthesized 202 1 ,450 7.16 chloride by treating benzyl chloride with thiourea in ethanol
4 * HO-CH 2 CH 2 -SH Aldrich 78.1 559 7.16
Chemical
Co.
5 " Acetalde- Allied Signal 59.1 423 7.16 hyde
Oxime
6 Aniline Aldrich 93.1 666 7.16
Chemical
Co.
7 Benzylamine Aldrich 107 766 7.16
Chemical
Co.
8 Benzoic hydrazide Aldrich 136 973 7.16
Chemical
Co.
9 2-butanone oxime Allied-Signal 87 623 7.16
10 Benzaldehyde oxime Aldrich 121 697 5.76
Chemical
Co.
11 Dimethyl maleate Aldrich 144 1 ,030 7.16
Chemical
Co.
12 aleic Baker 98.1 702 7.16 Anhydride Performance
Chemicals
SAMPLE CANDIDATE SOURCE MW AMT. OF MMOLES OF CANDI¬ CANDIDATE DATE ADDED ( g)
13 Aceto- Aldrich 120 859 7.16 phenone Chemical
Co.
14 Benzo- Aldrich 182 1 ,300 7.16 phenone Chemical
Co.
15 Thiophenol Aldrich 110 788 7.16
Chemical
Co.
16 Diethyl Aldrich 160 1 ,150 7.16 malonate Chemical
Co.
17 Triphenyl- phosphine Aldrich 262 1 ,880 7.16
Chemical
Co.
18 Triphenyl phosphite Aztec 310 2,220 7.16 Catalyst Co.
19 Trimethyl phosphite Aldrich 124 888 7.16
Chemical
Co.
20 Benzaldehyde Aldrich 106 759 7.16
Chemical
Co.
21 2 Benz-aldehyde/1 — 212/58 1520/ 7.16 acetone 415 (reactio n product)
22 30% H 2 0 2 EM Science 34 811 7.16
23 25% Na 2 CS 3 Baker 154 4,410 7.16 Perfor¬ mance Chemicals, Inc.
Candidates 4 and 5 inadvertently may have been double-dosed with vinyl acetate.
The bottles were observed for color and precipitation after 24 hours. The results are shown in Table II:
TABLE II
CANDIDATE OBSERVATION AT 24 HOURS
1 Dark red solution, red deposit on top
2 Colorless, no haze, no precipitate
3 Light yellow solution, no red precipitate; but insoluble candidate on bottom
4 Yellow solution, insoluble candidate on bottom
5 Dark red solution, very hazy, possible precipitate
6 Red solution, unreacted candidate on top
7 Red solution, unreacted candidate on top
8 Yellow solution, voluminous amount of white, air-filled precipitate on top
9 Light red solution, no haze or precipitate
10 Light red solution, insoluble candidate on top
11 Dark red solution, very hazy; lots of red precipitate
12 Dark Red solution, very hazy; lots of red precipitate
13 Red solution, small amount of insoluble candidate on bottom
14 Red solution; no haze or precipitate, but substantial unreacted candidate on top
15 Yellow solution, no haze or precipitate, but a lot of insoluble candidate on top
16 Red solution, hazy but no observable precipitate
17 Red solution, ho haze or precipitate, but substantial undissolved candidate
18 Light yellow solution, no haze or precipitate, but substantial unreacted candidate
19 Dark red solution, haze, but no obvious precipitate
20 Red solution, no haze, no precipitate, but substantial sticky black precipitate on top
21 Red solution, hazy, a lot of sticky black precipitate on top
22 Dark red solution, no haze, no precipitate
23 Light red solution, no haze; flaky, black precipitate on bottom
Based on the foregoing, candidate 2 (hydrazine) is a preferred inhibiting agent for MEA scrubbers because the solution is colorless and no haze or precipitate is present. Candidates 1 , 9, and 22-tertiary-butyl hydroperoxide, 2-butanone oxime, and hydrogen peroxide, respectively— appear to be suitable agents for inhibiting aldol condensation in MEA scrubbers.
Persons of skill in the art will appreciate that many modifications may be made to the embodiments described herein without departing from the spirit of the present invention. Accordingly, the embodiments described herein are illustrative only and are not intended to limit the scope of the present invention.